Oct. 2024, Japan Society for Mechanical Engineers, Thermal Engineering Division, Thermal Engineering Award for International Activity　　　　　　　　　　　　　　　
International leadership in the field of microgravity combustion research and contributions to combustion engineering from a fundamental perspective
Osamu Fujita

Oct. 2023, Hokkaido University, Excellent Teacher Award　　　　　　　　　　　　　　　
令和4年度全学教育科目
Osamu Fujita

Feb. 2023, The Combustion Institute, 39th International Symposium on Combustion Distinguished Paper Award　　　　　　　　　　　　　　　
Experimental study on downward/opposed flame spread and extinction over electric wires in partial gravity environments
Yusuke Konno;Yutao Li;Jean-Marie Citerne;Guillaume Legros;Augustin Guibaud;Nozomu Hashimoto;Osamu Fujita

Nov. 2022, Combustion Society of Japan, 2022 Photo Contest -Beautiful Flames- The HIGHEST AWARD　　　　　　　　　　　　　　　
Chrysanthemum Flame
DELFIN, Jerric;GUO, Feng;HASHIMOTO, Nozomu;FUJITA, Osamu

Sep. 2022, The Japan Society of Microgravity Application, The Best Paper Award　　　　　　　　　　　　　　　
Limiting Oxygen Concentration Trend of ETFE-Insulated Wires under Microgravity
Ken MIZUTANI;Kyosuke MIYAMOTO;Nozomu HASHIMOTO;Yusuke KONNO;Osamu FUJITA

Nov. 2018, TANIKAWA FUND PROMOTION OF. THERMAL TECHNOLOGY, Komou Thermal Technology Award　　　　　　　　　　　　　　　
Contribution to combustion engineering, specially research on combustion phenomena for industrial furnace
FUJITA Osamu

Feb. 2018, The Combustion Institute, Fellow　　　　　　　　　　　　　　　
FUJITA Osamu

Mar. 2015, The Japan Society for Aeronautical and Space Science, Fellow　　　　　　　　　　　　　　　
FUJITA Osamu

Mar. 2015, Hokkaido University, President Award for Educational Contribution　　　　　　　　　　　　　　　
Contribution to Hokkaido Universal Campus Initiative
FUJITA Osamu

Dec. 2014, Combustion Society of Japan, 2014Phto Contest-Beautiful Flame- The Highest Award　　　　　　　　　　　　　　　
Flame cake of the first birthday
Sunghwan YOON;Taejoon NOH;Osamu FUJITA

Oct. 2013, 機械学会熱工学部門部門表彰, 第90期熱工学部門研究業績表彰　　　　　　　　　　　　　　　
熱工学、とりわけ微小重力環境を利用した火炎中のすす生成、および固体燃焼などの分野における研究業績
藤田 修

May 2013, 日本スマートプロセス学会（高温学会）, 2013年度Best Reviewer 賞　　　　　　　　　　　　　　　
固体バイオマスの燃焼研究、－高圧縮バイオマスブリケットの燃焼特性－
伊東弘行;酒井雄人;中原毅朗;井田民男;藤田 修

Apr. 2013, Japan Society of Mechanical Engineers (JSME), Fellow　　　　　　　　　　　　　　　
FUJITA Osamu

Nov. 2012, Japan Society for Mechanical Engineers, Thermal Engineering Division, Best Presentation Award　　　　　　　　　　　　　　　
Research on pyrolysis gas release characteristics from bio-cokes fuel
Hiroyuki Ito;Yuto Sakai;Tamio Ida;Kaoru Wakatsuki;Osamu Fujita

Apr. 2007, Japan Society of Mechanical Engineers (JSME), Best paper award　　　　　　　　　　　　　　　
A study on the Effect of Wall Temperature on Soot Deposition Process from a Diffusion Flame in Microgravity
Osamu Fujita, Japan

Oct. 2006, The Japan Society of Microgravity Application, The Best Paper Award of the Japan Society of Microgravity Application　　　　　　　　　　　　　　　
Combustion behavior of polyethylene insulated electric wire under low flow velocity in microgravity
Osamu Fujita, Japan

Nov. 1999, Combustion Society of Japan, Award for young researchers, Combustion Society of Japan (1999.11)Best Flame Picture Award, Combustion Society of Japan, (2001.12)　　　　　　　　　　　　　　　
Research on solid material flammability and soot formation utilizaing microgravity environment
Osamu Fujita, Japan

Thermoacoustic parametric instability of premixed ammonia flames propagating downwards in an open-closed tube
Jerric R. Delfin, Feng Guo, Nozomu Hashimoto, Osamu Fujita
Fuel, 373, 01 Oct. 2024, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, This work investigates the self-excited thermoacoustic parametric instability of downward propagating laminar premixed ammonia flames in an open-closed combustion tube. NH3/O2/N2 flames were propagated at different laminar burning velocities at equivalence ratios of ɸ = 0.8 and ɸ = 1.2. Different unstable flame regimes were observed through pressure fluctuation measurements and synchronized high-speed imaging capturing the lateral and longitudinal perspectives of flame propagation. The observed propagation speed of quasi-planar flames showed a strong correlation with the calculated laminar burning velocities of NH3/O2/N2 mixtures. For the first time, the cellular structures of laminar premixed ammonia flames at the onset of parametric instability were clearly observed from the present experimental approach. The experimental cellular flame wavenumbers and acoustic velocity fluctuation amplitudes at the onset of parametric instability are in qualitative agreement with the theory of stability of laminar flames under acoustic excitation. Experiments have shown that NH3/O2/N2 flames are more unstable than CH4/O2/N2 flames at the same laminar burning velocity independent of Lewis number within the range of tested conditions. The influence of activation energy on parametric instability is investigated through a comparative thermoacoustic analysis between two different fuels at varied equivalence ratios. Ammonia flames are characterized by large overall activation energy and Zeldovich numbers compared to hydrocarbon flames. This work elucidates how this unique property characterizes the acoustic instability of downward propagating premixed ammonia flames in a tube based on classical theories on acoustic instability of laminar premixed flames., 40646070

Droplet evaporation characteristics of hydrotreated vegetable oil (HVO) under high temperature and pressure conditions
Leang So Khuong, Nozomu Hashimoto, Yusuke Konno, Yusuke Suganuma, Hiroshi Nomura, Osamu Fujita
Fuel, 368, 131604, 131604, Elsevier BV, Jul. 2024, [Peer-reviewed], [Last author]
English, Scientific journal

Modelling of opposed flame spread over thin electric wires: estimation of flame spread rates and limiting oxygen concentrations
Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
Combustion Theory and Modelling, 1, 32, Informa UK Limited, 23 May 2024, [Peer-reviewed], [Last author]
English, Scientific journal

Downward flame spread over thin electrical wires in quiescent normal- and hypergravity environments: Effects of gravity level, applied current and wire configuration
Zhengda Guo, Yuxuan Ma, Qiang Wang, Zhonghua Li, Yuhang Chen, Osamu Fujita, Longhua Hu
Proceedings of the Combustion Institute, 40, 1-4, 105773, 105773, Elsevier BV, 2024, [Peer-reviewed]
English, Scientific journal

Turbulent flame propagation limits in polymethylmethacrylate particle cloud combustion
Yu Xia, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, 40, 1-4, 105511, 105511, Elsevier BV, 2024, [Peer-reviewed], [Last author]
English, Scientific journal

Quantitative prediction of the flammability limits of filter paper in microgravity conditions
Shuhei Takahashi, Hiroyuki Torikai, Yoshinari Kobayashi, Masao Kikuchi, Osamu Fujita
Proceedings of the Combustion Institute, 40, 1-4, Jan. 2024
Scientific journal, Under JAXA's FLARE project, ongoing since May 2022, long-duration microgravity combustion experiments have been conducted using filter paper. These experiments utilize the Solid Combustion Experiment Module (SCEM) in the ISS/Kibo module. The dimensions of the filter paper used were 130 mm in length and either 40 mm or 20 mm in width, with the experiments conducted in an environment of 298 K and 100 kPa. This paper highlights the results of 19 flame spread experiments performed in opposed-flow environments and compares the predetermined flammability limiting curve with the flammability map obtained in orbital experiments. One of the objectives of the FLARE project is to predict the flammability limiting curve in microgravity environments based on the results of tests that can be conducted on the ground. These experiments produced intriguing findings, demonstrating the effects of both radiation loss and blow-off during flame spread, as the opposed flow velocity was incrementally increased from 10 cm/s to 18 cm/s in 2 cm/s steps, within an environment containing 15.5 % oxygen concentration. When comparing with the combustible map obtained from orbital experiments, it was discovered that the original limit curve accurately replicated the blow-off branch but overestimated the flammable region in areas with opposed-flow velocity below 10 cm/s. This discrepancy was attributed to the inadequate consideration of the effect of opposed-flow velocity on the radiation quenching branch. Therefore, by considering the velocity distribution measurement results obtained in orbit and modeling the impact of the effective flow velocity opposing the flame front on both the radiation quenching branch and the blow-off branch, we successfully quantitatively replicated the results of the orbital experiments. These findings indicate that the flammability limits of thin flat plate samples can be accurately predicted by properly assessing the effect of the boundary layer on the sample surface.

Determination method of Markstein number based on wavenumber measurement of cellular flames at the onset of parametric instability of downward propagating flames
Jerric R. Delfin, Feng Guo, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, 40, 1-4, Jan. 2024, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, This work proposes a new method to estimate the Markstein number by investigating the thermoacoustic parametric instability of laminar premixed flames propagating downwards in an open-closed tube. Methane-air flames were propagated in a combustion tube to capture the flame evolution in transition to parametric instability. By synchronized high-speed imaging filming both lateral and longitudinal views of flame propagation, cellular flame wavenumbers are measured from the clear transition of flat flames to cellular flames visualized in the present approach. The Markstein number is indirectly determined from wavenumber measurements at the onset of parametric instability by employing a laminar flame model under acoustic excitation treating the Markstein number as a free parameter. Acoustic velocity fluctuation amplitudes obtained from pressure fluctuation measurements were determined to further evaluate the validity of wavenumber-derived Markstein numbers. Markstein numbers obtained in the present work are compared with Markstein numbers relative to fresh gases in the literature from indirect and computational methods., 40646070

Downward flame spread and extinction over electric wires placed in a ground-based centrifuge
Yusuke Konno, Shoryu Ishikawa, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, 40, 1-4, Jan. 2024, [Peer-reviewed], [Last author]
English, Scientific journal, This study investigates the downward flame spread over laboratory wire samples in a ground-based centrifuge. The specimens consist of low-density polyethylene (LDPE) insulation over metallic cores. Copper (Cu) and nickel-chrome (NiCr) were selected as core materials because they can establish different flame sizes under the same experimental conditions. The centrifugal force is varied from 0 G to 3 G by adjusting the rotational speed of the centrifuge. The flame shapes are photographed from two angles, revealing the tilt of the flame due to the Coriolis force as well as the centrifugal force. Flame spread rates and flame spread limits are also obtained as a function of centrifugal force with oxygen concentration and wire characteristics as experimental variables. As the centrifugal force increases, the flame spread rate decreases and the flammable range narrows. This suggests suppressed flammability under hyper-gravity conditions, explained by finite rate chemistry and thermal effects from flame shape deformation. The Cu sample with large thermal conductivity is strongly affected by the change in heat balance due to the change in flame shape, and the dependence of the flame spread rate and flame spread limit on the centrifugal force is pronounced. Additionally, the displacement of downstream flame is measured with respect to the wire position, and the ratio of Coriolis and centrifugal forces affecting the flame is estimated along with a simple analysis. The ratio of Coriolis force-to-centrifugal force on the flame is found to increase with decreasing the centrifugal force and the radius of rotation decreased.

Application of ISO 4589-4 to determine limiting oxygen concentrations for opposed-flow flame spread over thin electric wires and their comparison with microgravity data
Yusuke Konno, Muhammad Zhaffri Bin Zainal, Nozomu Hashimoto, Osamu Fujita
Fire Safety Journal, 141, 103989, 103989, Elsevier BV, Dec. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Identifying two ignition modes of polymer insulated wires with continuous excess current in microgravity
Feng Guo, Seiya Kawaguchi, Nozomu Hashimoto, Osamu Fujita
Fire Safety Journal, 141, 103925, 103925, Elsevier BV, Dec. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Flame Spread Behavior Over a Filter Paper Near Extinction Limit Under Microgravity on the ISS/Kibo
Shuhei Takahashi, Hiroyuki Torikai, Yoshinari Kobayashi, Masao Kikuchi, Osamu Fujita
Fire Technology, 60, 1, 313, 334, Springer Science and Business Media LLC, 04 Nov. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

Revealing the role of limiting oxygen concentration test for a wick flame in characterizing the liquid fuel flammability
Feng Guo, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 257, 113029, 113029, Elsevier BV, Nov. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

On the radiation extinction of opposed flame spread over curved solid surface in low flow velocity conditions
Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 254, 112836, 112836, Elsevier BV, Aug. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Effect of solid surface curvature and wall heat loss on the downward flame spread along the edge of thin PMMA sheets
Yuxuan Ma, Yusuke Konno, Qiang Wang, Longhua Hu, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 254, 112837, 112837, Elsevier BV, Aug. 2023, [Peer-reviewed], [Last author]
English, Scientific journal

The effect of duct size, sample size, and fuel composition on concurrent flame spread over large cellulose samples in microgravity
Sandra L. Olson, Gary A. Ruff, Paul V. Ferkul, Jay C. Owens, John Easton, Ya-Ting Liao, James S. T'ien, Balazs Toth, Grunde Jomaas, Carlos Fernandez-Pello, Guillaume Legros, Augustin Guibaud, Osamu Fujita, Nikolay Smirnov, David L. Urban
Combustion and Flame, 248, 112559, 112559, Elsevier BV, Feb. 2023, [Peer-reviewed]
Scientific journal

Blowout limits of inclined nonpremixed turbulent jet flames
Qiang Wang, Xuan Liang, Aquan Lu, Ben Wang, Osamu Fujita, Suk Ho Chung, Longhua Hu
Proceedings of the Combustion Institute, 39, Elsevier BV, Dec. 2022, [Peer-reviewed]
English, Scientific journal, 40646075

Turbulent flame propagation limits of polymethylmethacrylate particle cloud–ammonia–air co-combustion
Yu Xia, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Elsevier BV, Nov. 2022, [Peer-reviewed], [Last author]
English, Scientific journal, Ammonia is a highly promising energy carrier for achieving a carbon-neutral society. The co-combustion of solid particle clouds-ammonia, in particular, is considered an efficient and feasible method of reducing carbon dioxide emissions. Understanding turbulent flame stabilization and extinguishment processes during the two-phase hybrid-mixture co-combustion of solid particle clouds-ammonia is essential for the co-combustion technology to be used in combustors. To the best of our knowledge, this is the first study to describe the turbulent flame propagation limits and associated mechanism on the co-combustion of solid particle clouds-ammonia-air. Turbulent flame propagation experiments on silica particle clouds-ammonia-air mixing combustion and polymethylmethacrylate (PMMA) particle cloud-ammonia-air co-combustion were conducted in this work using a novel fan-stirred constant-volume vessel to clarify the turbulent flame propagation limits and associate mechanism of solid particle cloud-ammonia-air co-combustion. Results showed that adding inert silica particles contracted the turbulent flame propagation limits of premixed ammonia-air mixtures. However, adding PMMA particles expanded and then contracted the turbulent flame propagation limits of a premixed ammonia-air mixture as the ammonia equivalence ratio increased from lean to rich. In the solid particle cloud-ammonia-air co-combustion, reactive particles induce two types of effects on the turbulent flame propagation limits of premixed ammonia-air mixtures: The local equivalence ratio increment effect is caused by adding volatile matter from preheated particles in the preheat zone of the flame front, and the heat sink negative effect is induced by the unburned particles.

Investigation of Combustion of the Gas Turbine Engine from Kerosene and Biokerosene and Their Soot Characteristics in Diffusion Flames
Thong D. Hong, Iman K. Reksowardojo, Tatang H. Soerawidjaja, Osamu Fujita
ACS Omega, 7, 42, 37085, 37094, American Chemical Society (ACS), 25 Oct. 2022, [Peer-reviewed], [Last author]
Scientific journal

Effect of pyrolysis kinetic parameters on the overload ignition of polymer insulated wires in microgravity
Feng Guo, Seiya Kawaguchi, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Elsevier BV, Oct. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, The overload ignition of polymer insulated wires in microgravity was investigated as basic information for space fire safety. This paper focuses on the effect of pyrolysis kinetic parameters of the insulation material on the ignition characteristics. A two-dimensional numerical model calculation under varied pyrolysis model was carried out to simulate the overload ignition, and microgravity experiments have been conducted for the model validation. With the help of thermogravimetric analysis, the original pyrolysis model of the polyethylene insulation used for wire ignition experiments was obtained. Three groups of varied pyrolysis models were proposed by changing the activation energy (E), pre-exponential factor (A) from the original model. Numerical simulations were conducted with the varied pyrolysis models. The simulated results employing the original pyrolysis model showed a good agreement with the microgravity experiments for ignition delay time with continuous current and the minimum ignition energy (MIE) with short-term current, respectively. From the simulation results with continuous overloading, the independent variation of A and E in the pyrolysis model has a limited effect on the ignition delay time but a significant effect on ignition modes in microgravity. Such effects are mainly reflected by changing the pyrolysis temperature during overloading, which determines the ease of spontaneous ignition. With a constant pyrolysis temperature, the change of mass loss rate in the pyrolysis model may affect the transition point from the "spontaneous ignition" to the "wire assisted ignition" when the current increases. Finally, for short-term current supply in microgravity, the single change of A or E showed higher MIE than the original pyrolysis model.

Experimental study on downward/opposed flame spread and extinction over electric wires in partial gravity environments
Yusuke Konno, Yutao Li, Jean-Marie Citerne, Guillaume Legros, Augustin Guibaud, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Elsevier BV, Jul. 2022, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, Downward/opposed flame spread over laboratory wire samples under varied gravity conditions were investigated in the range from 0 G to 1 G. Reduced gravity experiments are conducted by parabolic flights of an airplane. Limiting oxygen concentrations (LOCs) and flame spread rates and flame spread rates (Vf) are obtained as a function of gravity level, with oxygen concentration, forced flow velocity, and wire characteristics such as insulation thickness and core material as experimental variables. The samples used in this study consist of low-density polyethylene (LDPE) insulation over metallic cores. Copper (Cu) and nickel-chrome (NiCr) were selected as core materials. It is found that the effect of gravity on the insulation flammability varies with the thermal conductivity of the wire core; the LOCs of the Cu sample are less affected by gravity, while those of the NiCr sample decrease with decreasing gravity level. On the other hand, Vf increase monotonically with increasing gravity level in the Cu sample, while Vf of the NiCr sample show a peak value under the low gravity conditions. It is suggested that these differences in the response of LOCs and Vf to the gravity level due to the difference in core materials are controlled by the fuel concentration in the reaction zone, which is a function of Vf. It is also found that the molten LDPE produced during the flame spread process shows unique behaviors depending on the gravity levels and wire characteristics. Some characteristics of the dynamic motion of the molten LDPE during the flame spread process, such as deformation and dripping, are also summarized in this paper. The experimental data obtained in this study provide useful information on the flammability of materials in a partial gravity environment and will serve as a database for fire safety design in future space exploration.

Turbulent flame propagation mechanism of polymethylmethacrylate particle cloud–ammonia co-combustion
Yu Xia, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 241, 112077, 112077, Elsevier BV, Jul. 2022, [Peer-reviewed]
Scientific journal

Development and validation of evaporation model for a multi-component fuel considering volume-average internal mass and enthalpy
Yushin Naito, Nozomu Hashimoto, Osamu Fujita
International Journal of Heat and Mass Transfer, 188, 01 Jun. 2022, [Peer-reviewed]
Scientific journal, We developed a droplet evaporation model for a multi-component fuel, considering the nonuniform distributions of both mass fraction and temperature inside multi-component fuel droplet. The distribution equations satisfy the conservation of droplet mass and enthalpy. We proposed mass fraction and temperature distribution equations inside a droplet to accurately determine variations between the numerical assumptions of a liquid phase and a gas phase. We found that an obvious gradient appears in the mass fraction and temperature distribution profiles at various ambient temperatures. To verify the accuracy of the developed model, we further compared the predicted droplet lifetimes with the experimental results at various ambient temperatures. The consideration of the pre-evaporation process led to more accurate droplet lifetime prediction using the present model. We also investigated the differences between the present model and the uniform distribution model. The difference in the predicted droplet lifetime becomes more than 10% at practical spray combustion conditions. Thus, internal distribution of mass fraction ad temperature must be considered in practical spray combustion simulations.

Experimental study of downward flame spread and extinction over inclined electrical wire under horizontal wind
Siyao Jia, Longhua Hu, Yuxuan Ma, Xiaolei Zhang, Osamu Fujita
Combustion and Flame, 237, 111820, 111820, Elsevier BV, Mar. 2022, [Peer-reviewed], [Last author]
English, Scientific journal

Turbulent flame propagation of polymethylmethacrylate particle clouds in an O2/N2 atmosphere
Yu Xia, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 234, Dec. 2021, [Peer-reviewed]
English, Scientific journal, The combustion of solid particle clouds is extensively used in many engineering areas. However, experimental data describing the turbulent flame propagation behavior and the combustion mechanism of solid particle clouds have remained limited. In this work, the combustion of polymethylmethacrylate (PMMA) particle clouds was studied by employing a unique fan-stirred constant-volume chamber. For the quasi-monodispersed particle clouds, the flame propagation velocity increased with the increase in the turbulence intensity and the decrease in the quasi-monodispersed particle size. However, the particle concentration had little effect on the flame propagation velocity, which is unique in a turbulent flow field. The consistency of the results between the current study of PMMA particle clouds and the previous study for coal particle clouds showed that the heterogeneous combustion of char particles had little effect on the turbulent flame propagation velocity of the solid particle clouds. Further, two types of quasi-monodispersed particles were mixed to study how the interactions between small and large (polydispersed) particles affect turbulent flame propagation. We found that the turbulent flame propagation velocity had a nonlinear relationship with the mass ratio of small particles (J-shaped curve). The turbulent flame propagation velocity slightly increased with low mass ratio of small particles, while it sharply increased with high mass ratio of small particles. Increasing the turbulence intensity and decreasing the primary particle (large particle) size can advance the starting point of the sharp increase. These unique features were explained by a mechanism considering the polydispersed interparticle interaction proposed by the authors. In the combustion of turbulent polydispersed particle clouds, the particle–particle agglomeration and the agglomeration break-up in the turbulent flow field affect turbulent flame propagation. To the best of our knowledge, this is the first report on the fundamental spherical turbulent flame propagation phenomenon and the mechanism of solid particle cloud combustion considering the polydispersed interparticle interactions.

Flammability Evaluation of Carbonate Esters by Using Wick-LOC Method
Osamu FUJITA, Feng GUO
Journal of the Combustion Society of Japan, 63, 206, 294, 301, 15 Nov. 2021, [Peer-reviewed], [Invited]
Japanese, Scientific journal

Effect of sample thickness on concurrent steady spread behavior of floor- and ceiling flames
Yuxuan Ma, Longhua Hu, Yajun Huang, Nan Zhu, Osamu Fujita
Combustion and Flame, 233, 111600, 111600, Elsevier BV, Nov. 2021, [Peer-reviewed], [Last author]
English, Scientific journal

Acoustic parametric instability, its suppression and a beating instability in a mesoscale combustion tube
Ajit Kumar Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 228, 277, 291, Jun. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2021 The present work reports thermo-acoustic instability in a mesoscale tube of diameter 8 mm (> quenching diameter) and length 702 mm. Mixtures with Lewis number, Le~ 0.8 (rich C2H4/O2/CO2), 1.05 (lean C2H4/O2/CO2) and 1.34 (lean C2H4/O2/N2) are used. Several new flame responses are observed. For lower burning velocity mixtures, flame extinction is observed due to heat loss when primary instability transforms to secondary instability for all Le mixtures. However, parametric cellular structures which are characteristic of parametric instability are observed only for Le of 0.8. It is proposed based on calculations and experiments that parametric structures will be observed only when diameter of tube is two times larger than the characteristic wavelength of parametric instability. If the tube diameter doesn't allow formation of parametric structure whirling and counter-rotating flames are observed instead of parametric structures. Suppression of acoustic parametric instability is observed for higher burning velocity mixtures with Le>1 and its mechanism is discussed. For a range of SL, a beating instability is observed for CO2 diluted mixtures of Le>1, where pressure oscillation and flame motion show beating oscillations of frequency around 15 Hz. This beating instability is believed to be caused by non-linear interaction of acoustic instability with pulsating instability of flame front which is caused due to combined radiative and convective heat loss. Due to CO2 dilution, the radiative heat losses could play a significant role in inducing pulsating instability.

Quantitative infrared image analysis of simultaneous upstream and downstream microgravity flame spread over thermally thin cellulose fuel in low speed forced flow
Sandra Olson, Osamu Fujita, Masao Kikuchi, Takashi Kashiwagi
Combustion and Flame, 227, 402, 420, May 2021, [Peer-reviewed]
English, Scientific journal, © 2021 Quantitative image analysis of infrared (IR) measurements are compared to visible color images for simultaneous upstream and downstream flame spread over thermally thin cellulose samples in low speed forced flow in microgravity. These results are a unique set of data that provide a wealth of information to guide future modeling efforts. Test conditions at ambient pressure were conducted in 21–50% O2 by volume (N2 balance) and forced flow velocities from 2 cm/s to 20 cm/s. The tests conditions encompass strictly upstream flame spread to simultaneous upstream and downstream flame spread. Steady upstream flame spread is observed while the downstream flame only begins to spread at the highest flow velocities due to the oxygen shadow cast by the upstream flame (oxygen depleted region downstream of the flame). Blackbody surface temperature gradients for the upstream flame are an order of magnitude larger than the downstream gradients. Upstream preheat lengths decrease with flow while downstream preheat lengths increase. Downstream pyrolysis lengths reach steady state for most cases and increase with convective heating while upstream pyrolysis lengths increase with time. Surface thermocouple (TC) histories were non-dimensionalized to obtain a characteristic surface temperature profile using new scaling analyses. Applying the ellipticity of the leading edge to the scaling reveals the local flow velocity at the leading edge is on the order of diffusive velocities and the flame thermal expansion acts as a significant barrier to divert the flow. A surface energy balance reveals that the peak heat flux for both upstream and downstream flames increases with oxygen concentration and forced flow velocity. The upstream flame heat flux is equally divided between fuel heat up and surface radiation. The downstream heat flux goes almost exclusively to surface radiation. Comparisons of these results to previous applicable research are provided throughout the text and generally agree well.

Effect of reduced ambient pressures and opposed airflows on the flame spread and dripping of LDPE insulated copper wires
Lauren Gagnon, Carlos Fernandez-Pello, James L. Urban, Van P. Carey, Yusuke Konno, Osamu Fujita
Fire Safety Journal, 120, 103171, 103171, Elsevier BV, Mar. 2021, [Peer-reviewed], [Last author]
English, Scientific journal

Experimental Study on Evaporation Characteristics of Light Cycle Oil Droplet under Various Ambient Conditions
Yushin Naito, Kengo Ueda, Nozomu Hashimoto, Masahide Takagi, Satoshi Kawauchi, Yasuo Imai, Manabu Watanabe, Takayuki Hasegawa, Toshiaki Hayashi, Yusuke Suganuma, Hiroshi Nomura, Osamu Fujita
Energy and Fuels, 35, 7, 6219, 6230, 2021, [Peer-reviewed]
English, Scientific journal, The authors conducted droplet evaporation experiments of light cycle oil (LCO) at various ambient temperatures and pressures. Five kinds of LCO and three kinds of arranged fuels were used. We investigated the evaporation characteristics of LCO and the relationships between the evaporation characteristics and the cetane index. In addition to that, a surrogate fuel composed of four chemical species, which can simulate the droplet evaporation characteristics of LCO, was suggested. Experimental results show that the differences in droplet lifetime between fuel species become larger with decreasing ambient temperature. This is because the low volatile component made the evaporation rate outstandingly slow at a low ambient temperature. It was found that the relationship between droplet lifetime and the late-stage distillation temperature becomes stronger at low ambient temperature and high ambient pressure. By an analysis employing the properties of chemical species in LCO surrogate fuel, it is clarified that the mass evaporation rate becomes smaller than the internal diffusion, which is the condition similar to that in the distillation test. Finally, the relationship between the droplet lifetime and the cetane index was investigated. It can be concluded that the droplet lifetime is independent of the cetane index under all conditions tested in this study. The experimental data obtained by this research can be utilized for the validation of multicomponent fuel droplet evaporation models in the future.

Accessing the soot-related radiative heat feedback in a flame spreading in microgravity: optical designs and associated limitations
A. Guibaud, J.-M. Citerne, J.-L. Consalvi, J.L. Torero, O. Fujita, M. Kikuchi, P.V. Ferkul, N. Smirnov, G. Jomaas, B. Toth, S. Rouvreau, G. Legros
Proceedings of the Combustion Institute, 38, 3, 4805, 4814, Elsevier BV, Jan. 2021, [Peer-reviewed]
English, Scientific journal

Effect of ambient pressure on the extinction limit for opposed flame spread over an electrical wire in microgravity
Masashi Nagachi, Jean-Marie Citerne, Hugo Dutilleul, Augustin Guibaud, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, 38, 3, 4767, 4774, Elsevier BV, Jan. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Turbulent flame propagation limits of ammonia/methane/air premixed mixture in a constant volume vessel
Genya Hashimoto, Khalid Hadi, Yu Xia, Aainaa Hamid, Nozomu Hashimoto, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
Proceedings of the Combustion Institute, Jan. 2021, [Peer-reviewed]
English, Scientific journal, © 2020 The Combustion Institute. Ammonia is one of promising energy carriers that can be directly used as carbon-neutral fuel for combustion applications. However, because of the low-burning velocity of ammonia, it is challenging to introduce ammonia to practical combustors those are designed for general hydrocarbon fuels. One of ways to enhance the combustibility of ammonia is by mixing it with other hydrocarbon fuels, such as methane, with a burning velocity is much higher than the burning velocity of ammonia. In this study, we conducted flame propagation experiments of ammonia/methane/air using a fan-stirred constant volume vessel to clarify the effect of methane addition to ammonia on the turbulent flame propagation limit. From experimental results, we constructed the flame propagation maps and clarified the flame propagation limits. The results show that the flame propagation limits were extended with an increase in mixing a fraction of methane to ammonia. Additionally, ammonia/methane/air mixtures with the equivalence ration of 0.9 can propagate at the highest turbulent intensity, even though the peak of the laminar burning velocity is the fuel-rich side because of the diffusional-thermal instability of the flame surface. Furthermore, the Markstein number of the mixture obtained in this research successfully expressed the strength of the diffusional-thermal instability effect on the flame propagation capability. The turbulence Karlovitz number at the flame propagation limit monotonically increases with the decreasing Markstein number.

Effect of fuel ratio of coal on the turbulent flame speed of ammonia/coal particle cloud co-combustion at atmospheric pressure
Khalid Hadi, Ryo Ichimura, Genya Hashimoto, Yu Xia, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, 38, 3, 4131, 4139, Elsevier BV, Jan. 2021, [Peer-reviewed], [Last author]
English, Scientific journal

Near-limit oscillatory behaviors on wick flames of dimethyl carbonate with trimethyl phosphate additions
Feng Guo, Yu Ozaki, Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Jan. 2021, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, © 2020 The Combustion Institute. The near-limit oscillatory behaviors on wick flames of dimethyl carbonate (DMC) with trimethyl phosphate (TMP) additions have been investigated experimentally. The experiments were conducted under a wick burner in conjunction with the limiting oxygen concentration test (wick-LOC), and the fuels were selected as typical examples of electrolyte solvents and organophosphorus compounds (OPCs) for lithium-ion batteries. The near-limit oscillating flames on the wick configuration were observed into two main characters: side-to-wake or side oscillation in for the side-stabilized flame (full flame) and wake oscillation for the wake-stabilized flame (wake flame). By tracing the flame base movement using a 240-fps camera, stable limit cycle oscillations were found in full flame cases, while the wake flame cannot sustain the oscillation for long and finally leads to global extinction. With the addition of TMP in DMC, the transition from the side-to-wake oscillation to the side oscillation was found in the unstable full flames with a linear increase in frequency and a significant drop in amplitude, while the wake oscillating flames performed increased trends for both. To clarify the dominant mechanism of TMP-added flame oscillations, laminar burning velocities of DMC+TMP mixtures were calculated at the oxygen level of each near-limit oscillating flame. The weakened flame speed with TMP addition revealed the inadequacy of buoyancy-driven mechanisms for the OPC added wick-flame. Then the wick surface temperature was measured adopting a special thermocouple arrangement to validate the thermal-diffusive promotion by TMP addition. Results showed that the heat feedback from TMP-added flames compensated for the low reactivity and provided a faster oscillation near the extinction limit.

Effect of ammonia/oxygen/nitrogen equivalence ratio on spherical turbulent flame propagation of pulverized coal/ammonia co-combustion
Yu Xia, Khalid Hadi, Genya Hashimoto, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Jan. 2021, [Peer-reviewed]
English, Scientific journal, © 2020 The Combustion Institute. Because ammonia is one of the most promising candidates for energy carrier in the future, various applications of ammonia as a fuel are currently considered. One medium for utilizing ammonia is by introducing it to coal-fired boilers. To the best of our knowledge, this paper is the first to report the fundamental mechanism of the flame propagation phenomenon for pulverized coal/ammonia co-combustion. The effects of the equivalence ratio of the ammonia-oxidizer mixture on the flame propagation velocity of pulverized coal/ammonia co-combustion in turbulent fields were clarified by the experiments employing a unique fan-stirred constant volume chamber. The flame propagation velocities of pulverized coal/ammonia co-combustion, pure ammonia combustion, and pure pulverized coal combustion were compared. As expected, the flame propagation velocity of pulverized coal/ammonia was higher than that of the pure pulverized coal combustion for all conditions. However, the comparison of the flame propagation velocities of pulverized coal/ammonia co-combustion and that of the pure ammonia combustion, revealed that whether the flame propagation of the pulverized coal/ammonia was higher than that of the pure ammonia combustion was dependent on the equivalence ratio of the ammonia-oxidizer. This unique feature was explained by a mechanism including three competing effects proposed by the authors. In the ammonia lean condition, the positive effects, which are the strong radiation from the luminous flame and the increment of local equivalence ratio by the addition of volatile matter, are larger than the negative effect, which is the heat absorption by coal particles in preheat zone. In the ammonia rich condition, the effect of an increment of the local equivalence ratio by the addition of volatile matter turns into a negative effect. Consequently, the negative effects overcome the positive effect in the ammonia rich condition resulting in a lower flame propagation velocity of pulverized coal/ammonia co-combustion.

Exploring a critical diameter for thermo-acoustic instability of downward propagating flames in tubes
Ajit Kumar Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute, Jan. 2021, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, © 2020 The Combustion Institute. Published by Elsevier Inc. Thermo-acoustic oscillations are observed when a flame ignited at open end of a tube propagates towards the closed end due to interaction between unsteady heat release rate fluctuations from flame and acoustic fluctuations. In our past work, it was found that thermo-acoustic instability increases with decreasing diameter from 7.0 cm to 3.0 cm. A recent study in flame propagation in Hele-Shaw cells showed that thermo-acoustic instability is not observed for plate separation less than or equal to 0.4 cm. Thermoacoustic instabilities cannot be observed in very narrow tubes due to excessive damping from the wall. This opens up the possibility of a critical diameter where thermo-acoustic instability would be maximum. In this work we perform flame propagation experiments with diameter of combustion tube in the range 0.5 cm to 3 cm for a fixed length of 70.2 cm. It was found that thermo-acoustic parametric instability begins at lowest laminar burning velocity when the diameter is around 1.0 cm. This diameter is termed as critical diameter. Critical diameter is found to be independent of Lewis number of mixtures. Existence of a critical diameter is thus proved experimentally. Growth rates of primary instability increase with decreasing diameter and show a maximum around the critical diameter and decrease with further decrease in tube diameter. But, growth rates of secondary instability as well as maximum pressure fluctuation amplitude decreases continuously with decreasing diameter. Mechanisms responsible for these observations and existence of a critical diameter are clarified.

Effect of flame surface area of downward propagating flames induced by single and double laser irradiation on transition to parametric instability
Nguyen T.G. Tri, Ajit K. Dubey, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 223, 450, 459, Jan. 2021, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2020 The single laser irradiation (SLI) method was adopted to develop a double laser irradiation (DLI) method to investigate the effects of laser-induced structures of downward-propagating flames in a tube on the transition from primary acoustic instability to parametric instability. Previously, the SLI method was effectively used to study the interaction between acoustic oscillation and flame structure by controlling the shape of the flame front. The deformed cellular structure (either concave or convex) of the SLI-induced flame can transition from primary acoustic instability to parametric instability under certain conditions. We conducted experiments in the same combustion tube with C2H4/O2/CO2 mixtures using both SLI and DLI for comparison. The DLI method forms double cellular structures, while SLI only forms single cellular structures on the flames. It was found that the DLI method was more effective than SLI in generating transition to parametric instability under same total laser power. Furthermore, a linear relationship was found between the area of the deformed structure (irrespective of its dimension) and the corresponding growth rate of acoustic pressure fluctuation during the propagation of the deformed flame. SLI- and DLI-induced deformed structures having the same deformed surface area demonstrate the same growth rate of thermo-acoustic instability regardless of the difference in (ak)2, where a is the amplitude and k is the wavenumber of the deformed structures, respectively. This factor described in the velocity coupling mechanism is important to reveal the growth rate of thermo-acoustic instability due to the variation in the flame surface area. The results revealed that the actual flame surface area, rather than (ak)2 of the laser-induced downward-propagating flame structure, determines the transition in the presence of nonhomogeneous cell distribution induced by SLI and DLI. The total deformed surface area is a more comprehensive criterion for transition to parametric instability.

Role of wire core in extinction of opposed flame spread over thin electric wires
Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 220, 7, 15, Elsevier BV, Oct. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2020 The Combustion Institute Theoretical and experimental works have been carried out to clarify the effect of core material on the extinction characteristics of the flame spreading over electric wires. Additionally, an attempt has been made to explain previous experimental results (Takahashi et al., 2013 [1]) which found that Limiting Oxygen Concentration (LOC) of copper (Cu) wire is higher than that of nickel-chrome (NiCr) wire. A theoretical model is developed to discuss the heat loss mechanism in the unburned zone ahead of the gas-phase preheat zone and its validity is confirmed by measured temperature profiles along Cu, iron (Fe), and NiCr wires insulated by low-density polyethylene (LDPE). The theoretical analysis reveals that the flame spread rate is a crucial value to assess the extinction characteristics of the flame spreading over electric wires because it controls heat loss in the unburned zone. The reduction of the flame spread rate increases heat loss in the unburned zone and induces the quenching extinction as a result of extended thermal diffusion length along the electric wire. It is also found that a highly conductive wire increases heat loss rather than poorly conductive wire even under the same flame spread rate. Such characteristics are well described by a newly introduced parameter, ηf, which is a dimensionless flame spread rate derived by the present study. By using ηf, previous experimental findings [1] are successfully explained.

Soap-derived biokerosene as an aviation alternative fuel: Production, composition, and properties of various blends with jet fuel
Long H. Duong, Iman K. Reksowardojo, Tatang H. Soerawidjaja, Osamu Fujita, Godlief F. Neonufa, Tri T.G. Nguyen, Tirto Prakoso
Chemical Engineering and Processing - Process Intensification, 153, Jul. 2020, [Peer-reviewed]
English, Scientific journal, © 2020 Elsevier B.V. This research has developed a soap-derived biokerosene (SBK) production process to produce hydrocarbons for use as an aviation alternative fuel. The SBK production process was developed in keeping with the conditions of the available technologies and investment while leveraging the advantage of an abundant national feedstock resource that is found in Indonesia in particular, and tropical emerging countries in general. The production of SBK comprises two main processes: saponification and thermal decarboxylation to convert coconut oil into hydrocarbons. The composition of SBK was analyzed and compared to that of Jet A1. Additionally, the critical properties of SBK and several of its blends with Jet A1 were measured and collated with the established jet fuel standard. The results show that SBK can be blended directly with Jet A1 at up to 10 vol.% to meet selected properties: distillation temperature, flash point, density, net heating value, viscosity, freezing point, smoke point, and oxidation stability. From this study, it can be concluded that SBK is feasible for use as a drop-in aviation fuel when blended with conventional jet fuel. Thus, the SBK production is highly promising for use in tropical countries to produce aviation biofuels, given the appropriate technologies and feedstock resources.

Range of “complete” instability of flat flames propagating downward in the acoustic field in combustion tube: Lewis number effect
Ajit K. Dubey, Yoichiro Koyama, Sung H. Yoon, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 216, 326, 337, Jun. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2020 Downward propagating flames ignited at the open end of an open-closed tube exhibit thermo-acoustic instability due to interaction of combustion generated acoustic fluctuations with the flame front. At sufficiently high laminar burning velocity (SL) two regimes of thermo-acoustic instability are observed, namely, primary instability (where initial cellular flame transitions to a vibrating flat flame) and a secondary instability (where vibrating flat flame transitions to vibrating turbulent flame due to parametric instability of flame front). On further increasing SL to a particular value, “complete instability” of flat flames is observed meaning flat flame cannot be stabilized and initial cellular flame transitions directly to parametric instability. This particular SL introduced in this work is termed “critical SL”. In past experimental works, stability of flat flames in the acoustic field had only been studied in terms of acoustic velocity amplitude and a critical acoustic velocity amplitude had been measured at the onset of parametric instability. The novelty of this work is that boundary of unconditional instability of flat flame (flat flame is unstable irrespective of acoustic velocity amplitude) is determined in terms of mixture conditions, e.g., SL. Particularly for propagating flames, this critical SL can be measured more easily and accurately than the critical acoustic velocity. This work presents the effect of Le (Lewis number) on critical SL. Three different fuels, CH4, C2H4 and C3H8 are tested with two different dilution gases (N2 and CO2) for equivalence ratio of 0.8 (lean) and 1.2 (rich). Twelve different Le ranging from 0.7 to 1.9 are generated through these mixture combinations. Generally, larger Le mixtures show higher critical SL than lower Le mixtures for any fuel. Theoretical calculations are performed to predict critical SL by studying instability of planar flame fronts in presence of acoustic forcing. Theoretical calculations successfully captured the effect of Le as predicted stability region of planar flame is narrower for lower Le than that for higher Le. However, accurate quantitative predictions of critical SL couldn't be obtained from existing theory, particularly for non-unity Le. Hence, a correction (a function of Zeldovich number, β and Le) to width of stability region is proposed to obtain better quantitative agreement for critical SL between experiments and theory and performs significantly well. The correction factor acts to compensate for the inaccuracies in Markstein number obtained from an analytical relationship during calculation of stability region width., 11969560

Turbulent burning velocity of ammonia/oxygen/nitrogen premixed flame in O2-enriched air condition
Yu Xia, Genya Hashimoto, Khalid Hadi, Nozomu Hashimoto, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
Fuel, 268, 117393, 1, 10, Elsevier, 15 May 2020, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, © 2020 Elsevier Ltd Ammonia is a promising hydrogen-energy carrier as well as a carbon-free fuel. However, turbulent burning behavior of ammonia flame had yet to be sufficiently studied. In this work, laminar and turbulent burning velocities of ammonia/oxygen/nitrogen flames were investigated under the condition of oxygen enrichment. The turbulent burning velocity of ammonia/oxygen/nitrogen mixtures was found to increase with increasing turbulence intensity. The ratio of the turbulent burning velocity to stretched laminar burning velocity, Utr/UN, increased with the turbulence Karlovitz number. However, because of the diffusional–thermal instability effect, given the same turbulent Karlovitz numbers, Utr/UN in ammonia-lean cases is larger than in ammonia-rich cases. These findings indicate that consideration of the effects of diffusional–thermal instability and of the turbulence is important for the prediction of turbulent flame propagation velocity in ammonia combustion fields.

Influence of lithium salts on the combustion characteristics of dimethyl carbonate-based electrolytes using a wick combustion method
Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 213, 314, 321, Mar. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2019 Flammability studies of electrolytes are required for screening safer materials used in lithium-ion batteries. Besides the thermal stability, the effects of lithium salts on electrolyte combustion are important as well for fire safety of electrolytes. To clarify the influence of lithium salts on the electrolyte flammability, experimental analyses were conducted using a unique wick combustion system in conjunction with the limiting oxygen concentration (LOC) test, called wick-LOC method. The dimethyl carbonate (DMC)-based electrolytes with 1M addition of different lithium salts (LiPF6, LiBF4, and LiTFSI) were studied comparing with pure DMC and trimethyl phosphate (TMP)-added solvents. The three lithium salts gave unique and distinct flame behaviors including flame shapes, colors and the changes of wick surface until self-extinguishing. The wick-LOC results indicated a considerable flame-retardant effect of LiPF6, while other salts have minor effects on the flame extinction. Utilizing the flame spectrum and combustion residue analyses, the roles of salts during combustion were characterized. The PF6 anion played a similar role with the TMP additive in the gas phase flame inhibition. In the cases of LiPF6 and LiBF4, the solid products (LiF) accumulation blocked the fuel supply from the wick to the flame region. In the case of LiTFSI, the serious charring of the cotton wick was considered as a potential hazard on solid combustibles in the real fire scenarios.

Performance and emission characteristics of a gas turbine engine burning soap-derived biokerosene/Jet A-1 blends
Iman K. Reksowardojo, Long H. Duong, Tatang H. Soerawidjaja, Tri T.G. Nguyen, Osamu Fujita, Godlief F. Neonufa
SAE International Journal of Fuels and Lubricants, 13, 2, 125, 136, SAE International, 2020
English, Scientific journal, There has been an increased interest as regards the use of biofuels in aviation gas turbine engines due to global efforts to reduce greenhouse gas emissions along with fluctuating jet fuel prices. This work researches the use of soap-derived biokerosene (SBK) in aircraft engines. SBK is a promising biofuel option for emerging tropical countries as its production requires a relatively simple technology, and its feedstock sources are abundant in these countries. Blends of Jet A-1 with up to 20 vol.% SBK were tested on a 1S/60 Rover gas turbine engine over a range of brake powers to measure engine performance and emissions. The results were then compared to those of pure Jet A-1. It shows that the engine running on SBK/Jet A-1 blends and pure Jet A-1 have almost similar engine performance parameters including engine efficiency, specific fuel consumption (SFC), turbine inlet temperature (TIT), and exhaust gas temperature (EGT). On the other hand, increasing the volume fraction of SBK in the fuel blends with Jet A-1 leads to a slight increase in carbon monoxide (CO) and HC emissions, while insignificant differences in the nitrogen oxides (NOx) emissions were found. From this study, some valuable recommendations could be found to improve the feasibility of SBK for use as an alternative aviation fuel.

Effect of Ignition Condition on the Extinction Limit for Opposed Flame Spread Over Electrical Wires in Microgravity
Masashi Nagachi, Fumiya Mitsui, Jean Marie Citerne, Hugo Dutilleul, Augustin Guibaud, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
Fire Technology, 56, 1, 149, 168, 01 Jan. 2020, [Peer-reviewed]
English, Scientific journal, © 2019, Springer Science+Business Media, LLC, part of Springer Nature. Flame spread over wire insulation plays a crucial role in spacecraft fire safety. To quantify the effect of the initial ignition condition on the limiting oxygen concentration (LOC) of spreading flame over wire insulation, opposed flow flame spread experiments with wire insulation were conducted in microgravity (parabolic flights). Both ignition power (32.7 W to 71.8 W) and heating time (5 s to 15 s) were varied for an external flow of 100 mm/s. The sample wires were made of polyethylene-coated nickel-chrome (NiCr) and Copper (Cu), respectively, both with inner core diameter of 0.50 mm and insulation thickness of 0.30 mm. A 0.50 mm diameter coiled Kanthal wire wrapped around the sample wire 6 times with 8 mm length was used as the igniter. The experimental results show that the LOC gradually decreases as the ignition power or heating time increases and eventually it reaches a constant value. Also, the effect of ignition condition on LOC was more pronounced for Cu wires than for NiCr wires. The variation range of LOC in the tested ignition condition in microgravity was larger than that of horizontal flame spread in normal gravity. This conclusion can have implication for future experiment in the International Space Station to avoid the wrong LOC value because of the insufficient initial ignition energy and will eventually lead to an improved fire safety in spacecrafts.

Experimental Evaluation of Flame Radiative Feedback: Methodology and Application to Opposed Flame Spread Over Coated Wires in Microgravity
Augustin Guibaud, Jean Marie Citerne, Jean Louis Consalvi, Osamu Fujita, Jose Torero, Guillaume Legros
Fire Technology, 56, 1, 185, 207, 01 Jan. 2020, [Peer-reviewed]
English, Scientific journal, © 2019, Springer Science+Business Media, LLC, part of Springer Nature. The objective of this work is to quantify for the first time soot-related radiative heat transfer in opposed flow flame spread in microgravity. This article presents experimental results obtained in parabolic flight facilities. A flame is established over a solid cylindrical polyethylene coated metallic wire and spreads at a steady rate, in low velocity flow conditions allowed by the absence of buoyancy. Implementing the Broadband Modulated Absorption/Emission technique, the two-dimensional fields of soot volume fraction and temperature are obtained for the first time in flame spread configuration over an insulated wire in microgravity. The consistency of the results is assessed by comparing results from independent experimental runs. From these fields, radiative losses attributed to soot in the flame are computed at each location. This map of radiative losses together with the profile of the wire surface are then used as inputs to a novel experimental approach that enables the assessment of soot radiative heat feedback to the wire. Results are extracted from a specific case of a flame propagating over a polyethylene coated Nickel–Chrome wire at nominal pressure. The oxidizer, composed of 19% oxygen and 81% nitrogen in volume is blown at opposed flow parallel to the wire at a velocity of 200mm·s-1. This new approach provides the first detailed quantitative measurements which are required to check the relevance of heat transfer models under development, therefore to better understand the mechanisms driving flame spread in microgravity.

Opposed-Flow Flame Spread and Extinction in Electric Wires: The Effects of Gravity, External Radiant Heat Flux, and Wire Characteristics on Wire Flammability
Yusuke Konno, Yoshinari Kobayashi, Carlos Fernandez-Pello, Nozomu Hashimoto, Shinji Nakaya, Mitsuhiro Tsue, Osamu Fujita
Fire Technology, 56, 1, 131, 148, 01 Jan. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal, © 2019, Springer Science+Business Media, LLC, part of Springer Nature. Combustion of electric wires is the most probable cause of fire in human space activities. Therefore, the fire performance of electric wires in microgravity conditions must be thoroughly analyzed. This study investigates the opposed-flow flame spread and its limits in electric wires preheated by external radiation, under both normal gravity and microgravity, to understand their fire performance when exposed to external heat sources in such gravity conditions. The experiments were performed on low-density polyethylene (LDPE)-insulated copper (Cu) wires having an outer diameter of 4 mm and differing in core diameter (2.5 and 0.7 mm, corresponding to insulation thicknesses of 0.75 and 1.65 mm, respectively). Both standard and black LDPE insulations were used to study the effect of radiation absorption on the wire preheating and subsequent flame spread. The comparison of the flame spread limits revealed that the wire with the thicker Cu core was less flammable under both normal gravity and microgravity; in particular, its flammability further decreased in the case of microgravity, in contrast with thinner electric wires (~ 1 mm outer diameter), which exhibited higher flammability in the same gravity condition. These results suggest that different mechanisms, for thicker and thinner wires, determining the critical conditions to sustain flame spread under microgravity. This study provides valuable information about the fire performance of electric wires in space gravity.

Blowout of non-premixed turbulent jet flames with coflow under microgravity condition
Qiang Wang, Longhua Hu, Shaoming Wang, Shuangfeng Wang, Suk Ho Chung, Osamu Fujita
Combustion and Flame, 210, 315, 323, Dec. 2019, [Peer-reviewed]
English, Scientific journal, © 2019 The Combustion Institute The blowout behavior of non-premixed turbulent coflow jet flames under microgravity environment was studied experimentally by utilizing a 3.6 s drop tower. Variations of flames leading to liftoff as well as blowout were examined by varying the coflow velocity and compared with those obtained under the normal gravity condition. A modeling work was conducted to incorporate the effects of the gravity (buoyancy) and coflow velocity on blowout behavior. Major findings include: (1) the flame length in microgravity was longer than that in normal gravity and decreased with increasing coflow velocity. The flame in microgravity showed more intense yellow luminosity with larger sooting zone; (2) the flame liftoff height increased with increasing coflow velocity in both gravity levels. The flame base was closer to the burner in microgravity as compared with that in normal gravity; (3) the blowout velocity in microgravity was appreciably larger than that obtained in normal gravity; and (4) a physical model based on Damköhler number was developed by using similarity solutions to characterize the differences in the blowout limits considering both the coflow and gravity (buoyancy) effects. The proposed model can successfully predict the experimental data. This work provided new data and basic scaling analysis for blowout limit of non-premixed turbulent jet flames considering both the coflow and gravity (buoyancy) effects.

Experimental study on flammability limits of electrolyte solvents in lithium-ion batteries using a wick combustion method
Feng Guo, Wataru Hase, Yu Ozaki, Yusuke Konno, Masaya Inatsuki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
EXPERIMENTAL THERMAL AND FLUID SCIENCE, 109, 109858, ELSEVIER SCIENCE INC, Dec. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, To quantify the flammability limits of organic electrolyte solvents used in lithium-ion batteries, a unique wick combustion system was developed in conjunction with limiting oxygen concentration (LOC) of candle-like flame, named wick-LOC method. By controlling the oxygen-nitrogen ratio of external flow of the wick diffusion flame, the flammability limits (LOC) of electrolyte solvents were determined experimentally. To provide reproducible results under specified conditions, the effects of axial flow velocity, exposed wick length and elapsed time after ignition on the wick-LOC were studied, and the proper experimental conditions were selected for further applications. To validate the reliability of wick-LOC in flammability evaluation, correlation analyses to other flammability properties (flash point, auto-ignition temperature, the heat of combustion and other types of LOC) were conducted. The wick-LOC method was then applied to quantify the flammability of mixed solvents. The linear changes of wick-LOC with mixing ratios were found in the mixture of linear and cyclic carbonates, while the non-linear trends were found in carbonate-ether mixed solvents. To evaluate the flame-retardant effectiveness of organophosphorus compounds (OPCs) as additives in electrolyte solvents, a series of tests were conducted. Results showed that small amounts of OPCs had significant flame-retardant effects, but the efficiency decreased with the higher OPC additions. The effectiveness of four OPCs was distinguished as well. The results of this work provided valuable information about the flammability limits of single and mixed electrolyte solvents, and it may be useful for designing electrolyte balanced in both performance and safety.

Determination of flame stability limits of Li-ion battery electrolyte solvents with organophosphorus compounds addition by wick-LOC method
Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame(IF:4.12), 207, 63, 70, Sep. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Experimental and theoretical study of secondary acoustic instability of downward propagating flames: higher modes and growth rates
Ajit K Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita
Combustion and Flame, 205, 316, 326, Jul. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Extinction limits of an ammonia/air flame propagating in a turbulent field
Ryo Ichimura, Khalid Hadi, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
FUEL(IF:5.128), 246, 15, 178, 186, Jun. 2019, [Peer-reviewed]
English, Scientific journal

Soot characteristics of dodecane, aviation bio-paraffins and their blends with propylbenzene in diffusion flames
Thong D Hong, Osamu Fujita, Tatang H Soerawidjaja, Iman K Reksowardojo
Renewable Energy(IF:5.439), 136, 84, 90, Jun. 2019, [Peer-reviewed]
English, Scientific journal

Flame propagation limit of premixed gas of ammonia and methane in turbulent fields in a constant volume vessel
Genya Hashimoto, Ryo Ichimura, Khalid Hadi, Yu Xia, Nozomu Hashimoto, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
The Proceedings of the National Symposium on Power and Energy Systems, 2019.24, D124, D124, Japan Society of Mechanical Engineers, 2019
Scientific journal

Prediction of soot formation characteristics in a pulverized-coal combustion field by large eddy simulations with the TDP model
H. Takahashi, N. Hashimoto, H. Watanabe, R. Kurose, O. Fujita
Proceedings of the Combustion Institute, 37, 3, 2883, 2891, 2019, [Peer-reviewed]
Scientific journal, © 2018 Elsevier Ltd. In this study, the soot formation characteristics in a pulverized-coal combustion field formed by a 4 kW Central Research Institute of Electric Power Industry (CRIEPI) jet burner were predicted by large eddy simulation (LES) employing a tabulated-devolatilization-process model (TDP model) [N. Hashimoto et al., Combust. Flame 159 (2012) 353-366]. This model enables to take into account the effect of coal particle heating rate on coal pyrolysis. The coal-derived soot formation model proposed by Brown and Fletcher [A. L. Brown and T. H. Fletcher, Energy Fuels 12 (1998) 745-757] was employed in the LES. A comparison between the data predicted by LES and the soot volume fraction distribution data measured by laser induced incandescence confirmed that the soot formation characteristics in the coal combustion field of the CRIEPI burner can be accurately predicted by LES. A detailed analysis of the data predicted by LES showed that the soot particle distribution in this burner is narrow because the net soot formation rate is negative on both sides of the base of the soot volume fraction. At these positions, soot particles diffused from the peak position of soot volume fraction are oxidized due to a relatively high oxygen concentration. Finally, the effect of soot radiation on the predicted gas temperature distribution was examined by comparing the simulation results obtained with and without soot radiation. This comparison showed that the maximum gas temperature predicted by the simulation performed with soot radiation was over 100 K lower than that predicted by the simulation performed without soot radiation. From result strongly suggests the importance of considering a soot formation model for performing numerical simulations of a pulverized-coal combustion filed.

Effects of gas temperature and oxygen concentration on the soot formation of laminar diffusion flames in the ambient gas mixtures of carbon-dioxide and oxygen
Kenichi Sato, Fujita Osamu
Transactions of the JSME (in Japanese), 85, 876, 1, 12, 2019, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Scientific journal

Flame Spread:Effects of Microgravity and Scale
David Urban, Sandra Olson, Gary A Ruff, James S T'ien, Ya-Ting T Liao, A. Carlos Fernandez-Pello, Jose A Torero, Guillaume Legros, Christian Eigenbrod, Nickolay Smirnov, Osamu Fujita, Sébastien Rouvreau, Balazs Toth, Grunde Jomaas
Combustion and Flame(IF:4.12), 199, 168, 182, Jan. 2019, [Peer-reviewed]
English, Scientific journal

Spherical turbulent flame propagation of pulverized coal particle cloud in O2/N2 Atmosphere
Khalid Hadi, Ryo Ichimura, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute(IF:3.299), 37, 3, 2935, 2942, Jan. 2019, [Peer-reviewed]
English, Scientific journal, The present study aims to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent flame propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments on spherical turbulent flame propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted. A common bituminous coal was used in the present study. The flame propagation velocity was obtained from an analysis of flame propagation images taken using a high-speed camera. It was found that the flame propagation velocity increased with increasing flame radius. The flame propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical flames using gaseous fuel. The coal concentration has a weak effect on the flame propagation velocity, which is unique to pulverized coal combustions in a turbulent field. These are the first reports of experimental results for the spherical turbulent flame propagation behavior of pulverized coal particle clouds. The results obtained in the present study are obviously different from those of previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.

Experimental investigation on the smoldering limit of scraps of paper initiated by a cylindrical rod heater
Hui Yan, Osamu Fujita
Proceedings of the Combustion Institute(IF:3.299), 37, 3, 4099, 4106, Jan. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Soot Formation Prediction in a Pulverized Coal Combustion Field by Large Eddy Simulation with TDP Model
H. Takahashia, N. Hashimotoa, H. Watanabeb, R. Kurosec, O. Fujita
Proceedings of the Combustion Institute(IF:3.299), 37, 3, 2883, 2891, Jan. 2019, [Peer-reviewed]
English, Scientific journal

Broadband Modulated Absorption/Emission technique to probe sooting flames: implementation, validation, and limitations
A. Guibaud, J.M. Citerne, J.M. Orlac’h, O. Fujita, J.-L. Consalvi, J.L. Torero, G. Legros
Proceedings of the Combustion Institute(IF:3.299), 37, 3, 3959, 3966, Jan. 2019, [Peer-reviewed]
English, Scientific journal

Effect of geometrical parameters on thermo-acoustic instability of downward propagating flames in tubes
Ajit KumarDubey, KoyamaYoichiro, HashimotoNozomu, FujitaOsamu
Proceedings of the Combustion Institute(IF:3.299), 37, 2, 1869, 1877, Jan. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Effect of Le on criteria of transition to secondary acoustic instability of downward-propagating flame in a tube with controlled curvature induced by external laser
Chung Yongho, Osamu Fujita, Nozomu Hashimoto
Proceedings of the Combustion Institute(IF:3.299), 37, 2, 1887, 1894, Jan. 2019, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Laser piloted ignition of electrical wire in microgravity
Yoshinari Kobayashi, Yusuke Konno, Xinyan Huang, Shinji Nakaya, Mitsuhiro Tsue, Nozomu Hashimoto, Osamu Fujita, Carlos Fernandez-Pello
Proceedings of the Combustion Institute, 37, 3, 4211, 4219, 2019, [Peer-reviewed]
English, Scientific journal, © 2018 Elsevier Ltd. This work studied the piloted ignition of electrical wires in both normal gravity and microgravity using the laser-induced spark. Unique experiments were conducted in the microgravity parabolic flight with laboratory wires under the oxygen concentration of 14-21% and external radiation of up to 15.9 kW/m2. The wire sample consists of a 2.5-mm thick core, using the solid copper (Cu) or the hollow stainless steel (SS) tube, and a 0.75-mm thick black polyethylene (PE) insulation. This is the first piloted-ignition experiment on solid fuel in microgravity with the laser-induced spark as the pilot. Experimental results show that regardless of the oxygen level, the ignition delay time is always smaller in microgravity than in normal gravity, indicating a higher fire risk in the microgravity space environment. As the heat flux and the oxygen concentration increase, auto-ignition is observed. Moreover, if the core is exposed to the external heating source, it can heat the insulation to promote the ignition, different from the heat sink found in past ignition research. This unique research provides valuable information about the fire risk of electrical wire in microgravity and future long-term space travel.

Downward flame spreading over electric wire under various oxygen concentrations
Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 37, 3, 3817, 3824, ELSEVIER SCIENCE INC, 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, The downward flame spread over laboratory electric wire under various oxygen concentrations has been investigated experimentally to improve our knowledge of electric-wire combustion. Two kinds of electrical wire (low-density-polyethylene (LDPE)-insulated copper (Cu) and nickel-chrome (NiCr)) are used in this study. The oxygen concentration of the mixture stream (O-2 and N-2) in the test section is varied between 15 and 41 vol%. Opposed-flow velocity in the test section is fixed at 15 cm/s. For NiCr wire, the flame spread rate ( V-f) and flame length (L-f) monotonically increase with oxygen concentration. For Cu wire, both V-f and L-f show non-monotonic behavior against oxygen concentration. Most interestingly, V-f decreases with oxygen concentration increase in the 25-31% range. Theoretical analysis shows two regimes of variation of V-f with oxygen concentration: the "temperature-dependent regime (TDR)" and the "negative-oxygendependent regime (NOR)". The non-monotonic behavior of V-f against oxygen concentration for Cu can be explained by the controlling mechanism behind TDR and NOR. However, experimental results show one more regime above 31% oxygen concentration that cannot be explained by the theory proposed in this work, namely the "soot-generation-dependent regime (SGR)"; here, radiation from the flame and soot deposit plays a dominant role in flame spread. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Can a spreading flame over electric wire insulation in concurrent flow achieve steady propagation in microgravity?
Masashi Nagachi, Fumiya Mitsui, Jean-Marie Citerne, Hugo Dutilleul, Augustin Guibaud, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
Proceedings of the Combustion Institute(IF:3.299), 37, 3, 4155, 4162, Jan. 2019, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal

Rapidly mixed combustion of hydrogen/oxygen diluted by N2 and CO2 in a tubular flame combustor
Ningfei Wang, Baolu Shi, Bo Li, Xiaoyao Zhao, Run Chen, Osamu FUJITA
International Journal of Hydrogen Energy(IF:4.084), 43, 31, 14806, 14815, Aug. 2018, [Peer-reviewed]
English, Scientific journal

Comparison of thermodynamical potentials of oxy-fuel combustion and regenerative combustion
SATO Kenichi, FUJITA Osamu
Transaction of the JSME, 84, 865, Aug. 2018, [Peer-reviewed], [Last author, Corresponding author]
Japanese, Scientific journal

The sooting tendency of aviation biofuels and jet range paraffins: effects of adding aromatics, carbon chain length of normal paraffins, and fraction of branched paraffins
Long H. Duong, Iman, K. Reksowardojo, Tatang, H. Soerawidjaja, Duc Ng. Pham, Osamu Fujita
Combustion Science and Technology(IF:1.564), 190, 10, 1710, 1721, Jun. 2018, [Peer-reviewed]
English, Scientific journal

Limiting Oxygen Concentration Trend of ETFE-Insulated Wires under Microgravity
Ken Mizutani, Kyosuke Miyamoto, Nozomu Hashimoto, Yusuke Konno, Osamu Fujita
INTERNATIONAL JOURNAL OF MICROGRAVITY SCIENCE AND APPLICATION, 35, 1, 350104-1, 350104-6, JAPAN SOC MICROGRAVITY APPLICATION, 2018, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, This study investigated the flammability of the fire-resistant material ethylene-tetrafluoroethylene (ETFE) as insulation for copper wires under different flow velocity and gravity conditions. The limiting oxygen concentration (LOC) of flame spreading horizontally over the sample was investigated at external opposed flow velocities ranging from 0 to 200 mm/s under normal gravity (1g(0)) and microgravity (mu g(0)). The LOC under mu g(0) showed a U-shape, which has been reported in previous studies. Aminimum LOC of approximately 26% was found at external flow velocities ranging 50-100 mm/s. An expanded heat balance model and radiation number for wire combustion (R-rad,R-wire) were proposed considering the heat conduction through the copper core, which is a notable feature of wire combustion. The U-shaped LOC curve was qualitatively explained in the low flow velocity region by this model and in the high flow velocity region by the DamkOhler number. We also compared the LOC trend of ETFE with that of polyethylene (PE)-insulated wires reported in a previous study and demonstrated that the drop of LOC in ETFE was much larger than that of PE when the gravitational condition was changed from lg(0) to mu g(0) (Delta LOC). This large difference was explained by two factors. First, the rate of change of flame temperature with an increasing oxygen concentration is small at high oxygen concentrations. Second, the increase in heat input through the copper core owing to gravity change was larger for ETFE than for PE because of the difference in the rate of change in flame length along the copper core.

Effect of insulation melting and dripping on opposed flame spread over laboratory simulated electrical wires
Yoshinari Kobayashi, Yusuke Konno, Xinyan Huang, Shinji Nakaya, Mitsuhiro Tsue, Nozomu Hashimoto, Osamu Fujita, Carlos Fernandez-Pello
Fire Safety Journal, 95, 1, 10, Jan. 2018, [Peer-reviewed]
English, Scientific journal, © 2017 Elsevier Ltd In electrical wires with insulations that burn and melt, the dripping of molten insulation can change the wire fire behavior, ignite nearby objects, and enhance the fire spread. Dripping is a result of gravity and depends on the insulation type of the wire and its orientation. In this work, the opposed flame spread over simulated electrical wires was studied with emphasis on the effect of the core and insulation type, and the melting and dripping of insulation. To facilitate the study, “laboratory” wires with polyethylene (PE) as insulation, were selected for the experiments. Horizontal and vertical wires of 8- and 9-mm diameter with soild copper (Cu) and hollow stainless steel (SS) cores and two types of PE insulations, low density and high density, were tested. The sizes of the laboratory wires were selected to facilitate the study of the effect of the type of insulation, the ratio of insulation to core thickness, or the thermal properties of the core, on the wire fire behaviors. Experimental results show a strong dependence of wire orientation on molten insulation dripping and flame spread. For horizontal wires, the flame spread is faster with Cu core than SS core because of a larger heat transfer ahead of the flame through the core. For vertical wires, the flame spread rate is dominated by the downward dripping of the molten insulation, but is comparatively not sensitive to the core material. Increasing the opposed flow speed, the flame gets closer to the wire which enhances the heating from Cu core and locally increases the flame spread. The effects of other parameters such as oxygen concentration, wire diameter, and insulation material are also discussed. This work provides important support to a larger project aimed at studying the fire behavior of electrical wires in a spacecraft environment. Without gravity, the dripping of molten material will not occur in a spacecraft, thus, characteristics of the flame spread process over a wire insulation material that melts during the spread of the flame will be drastically different on Earth or in a spacecraft.

Experimental observation of pulsating instability under acoustic field in downward-propagating flames at large Lewis number
Sung Hwan Yoon, Longhua Hu, Osamu Fujita
Combustion and Flame, 188, 1, 4, Elsevier Inc., 2018, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, According to previous theory, pulsating propagation in a premixed flame only appears when the reduced Lewis number, β(Le-1), is larger than a critical value (Sivashinsky criterion: 4(1 +3) ≈ 11), where β represents the Zel'dovich number (for general premixed flames, β ≈ 10), which requires Lewis number Le >
2.1. However, few experimental observation have been reported because the critical reduced Lewis number for the onset of pulsating instability is beyond what can be reached in experiments. Furthermore, the coupling with the unavoidable hydrodynamic instability limits the observation of pure pulsating instabilities in flames. Here, we describe a novel method to observe the pulsating instability. We utilize a thermoacoustic field caused by interaction between heat release and acoustic pressure fluctuations of the downward-propagating premixed flames in a tube to enhance conductive heat loss at the tube wall and radiative heat loss at the open end of the tube due to extended flame residence time by diminished flame surface area, i.e., flat flame. The thermoacoustic field allowed pure observation of the pulsating motion since the primary acoustic force suppressed the intrinsic hydrodynamic instability resulting from thermal expansion. By employing this method, we have provided new experimental observations of the pulsating instability for premixed flames. The Lewis number (i.e., Le ≈ 1.86) was less than the critical value suggested previously.

Flame spread over inclined electrical wires with AC electric fields
Seung J. Lim, Sun H. Park, Jeong Park, Osamu Fujita, Sang I. Keel, Suk H. Chung
COMBUSTION AND FLAME, 185, 82, 92, ELSEVIER SCIENCE INC, Nov. 2017, [Peer-reviewed]
English, Scientific journal, Flame spread over polyethylene-insulated electrical wires was studied experimentally with applied alternating current (AC) by varying the inclination angle (0), applied voltage (V-AC), and frequency (f(AC)). For the baseline case with no electric field applied, the flame spread rate and the flame width of downwardly spreading flames (DSFs) decreased from the horizontal case for -20 degrees <= theta < 0 degrees and maintained near constant values for -90 <= theta < -20 degrees, while the flame spread rate increased appreciably as the inclination angle of upwardly spreading flames (USFs) increased. When an AC electric field was applied, the behavior of flame spread rate in DSFs (USFs) could be classified into two (three) sub-regimes characterized by various functional dependences on V-AC, f(AC), and theta. In nearly all cases of DSFs, a globular molten polyethylene formed ahead of the spreading flame edge, occasionally dripping onto the ground. In these cases, an effective flame spread rate was defined to represent the burning rate by measuring the mass loss due to dripping. This effective spread rate was independent of AC frequency, while it decreased linearly with voltage and was independent of the inclination angle. In DSFs, when excessively high voltage and frequency were applied, the dripping led to flame extinction during propagation and the extinction frequency correlated well with applied voltage. In USFs, when high voltage and frequency were applied, multiple globular molten PEs formed at several locations, leading to ejections of multiple small flame segments from the main flame, thereby reducing the flame spread rate, which could be attributed to the electrospray phenomenon. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Study of the transient combustion of highly densified biomass briquette (Bio-coke) in an air flow
Hui Yan, Osamu Fujita
FUEL, 188, 595, 602, ELSEVIER SCI LTD, Jan. 2017, [Peer-reviewed]
English, Scientific journal, End-face combustion experiments were conducted on cylindrical bio-coke (BIC), i.e., a highly densified biomass briquette, to investigate whether quasi-one-dimensional steady combustion can be attained in 400-K air flow, as measured by a steady regression rate. In the experiment, it was found that the average regression rate in the first 0.01 m of BIC was relatively small after ignition, whereas after the first 0.01 m, the average regression rate became almost steady and much larger than that in the first 0.01 m. This suggests that before the steady regression period is reached, a non-negligible unstable regression rate phase exists. To investigate this transient combustion phase, one-dimensional numerical calculations were conducted, and the time-dependent regression rate and temperature distribution were computed. The mechanisms controlling transient combustion and the effects of volatile and moisture contents on transient combustion behavior were examined. The results show that a transient combustion period exists before steady combustion is achieved. This transient combustion period decreases as volatile content increases, and moisture content has a similar effect on transient combustion as volatile content. The phenomenon can be explained by the different final steady temperature distribution and evolution rate from the initial temperature distribution to the final steady temperature distribution. (C) 2016 Elsevier Ltd. All rights reserved.

Limiting oxygen concentration for extinction of upward spreading flames over inclined thin polyethylene-insulated NiCr electrical wires with opposed-flow under normal- and micro-gravity
Longhua Hu, Yong Lu, Kosuke Yoshioka, Yangshu Zhang, Carlos Fernandez-Pello, Suk Ho Chung, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 36, 2, 3045, 3053, ELSEVIER SCIENCE INC, 2017, [Peer-reviewed]
English, Scientific journal, Materials, such as electrical wire, used in spacecraft must pass stringent fire safety standards. Tests for such standards are typically performed under normal gravity conditions and then extended to applications under microgravity conditions. The experiments reported here used polyethylene (PE)-insulated (thickness of 0.15 mm) Nichrome (NiCr)-core (diameter of 0.5 mm) electrical wires. Limiting oxygen concentrations (LOC) at extinction were measured for upward spreading flame at various forced opposed-flow (downward) speeds (0-25 cm/s) at several inclination angles (0-75 degrees) under normal gravity conditions. The differences from those previously obtained under microgravity conditions were quantified and correlated to provide a reference for the development of fire safety test standards for electrical wires to be used in space exploration. It was found that as the opposed-flow speed increased for a specified inclination angle (except the horizontal case), LOC first increased, then decreased and finally increased again. The first local maximum of this LOC variation corresponded to a critical forced flow speed resulted from the change in flame spread pattern from concurrent to counter-current type. This critical forced flow speed correlated well with the buoyancy-induced flow speed component in the wire's direction when the flame base width along the wire was used as a characteristic length scale. LOC was generally higher under the normal gravity than under the microgravity and the difference between the two decreased as the opposed-flow speed increases, following a reasonably linear trend at relatively higher flow speeds (over 10 cm/s). The decrease in the difference in LOC under normal- and microgravity conditions as the opposed-flow speed increases correlated well with the gravity acceleration component in the wire's direction, providing a measure to extend LOC determined by the tests under normal gravity conditions (at various inclination angles and opposed-flow speeds) to LOC under microgravity conditions. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.

A numerical and experimental study of the ignition of insulated electric wire with long-term excess current supply under microgravity
Kohei Shimizu, Masao Kikuchi, Nozomu Hashimoto, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 36, 2, 3063, 3071, ELSEVIER SCIENCE INC, 2017, [Peer-reviewed]
English, Scientific journal, The ignition of electric wire after long-term excess current supply under microgravity was studied using both experimental and numerical methods. The experiments were conducted in parabolic flights that provided about 20 s of microgravity, while the numerical simulation was carried out in one-dimensional cylindrical co-ordinate system. The experimental results showed wire insulation was ignited by much lower electric currents under microgravity than under normal gravity and that the ignition delay time increased as the applied current decreased. It was further found that the total electric energy required for ignition increased with a decrease in the current value. The numerical analysis suggested that the increase in the required energy for ignition was caused by an increase in heat losses by conduction and radiation from the wire insulation surface to the ambient air, which increased the ignition delay time. As the ignition delay time became longer, heat loss by radiation became more dominant in the total heat loss. This was because a slow exothermic oxidation reaction occurred in the gas phase near the sample, and the temperature gradient next to the wire surface became smaller. We conclude that the ultimate ignition limit over a very long exposure to microgravity is mainly determined by radiation heat loss. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.

Effects of Lewis number on generation of primary acoustic instability in downward-propagating flames
Sung Hwan Yoon, Tae Joon Noh, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 36, 1, 1603, 1611, ELSEVIER SCIENCE INC, 2017, [Peer-reviewed]
English, Scientific journal, The generation mechanism of primary acoustic instability of downward-propagating flames in a combustion tube is investigated experimentally. The discussion first treats the effects of the coupling constant beta M, where beta and M represent the Zel'dovich and Mach numbers, respectively, and the effects of the flame surface area variation in equidiffusive flames on primary acoustic instability. A higher coupling constant tends to generate stronger acoustic sound under the same acoustic losses, whereas the variation in the flame surface area does not seriously affect the coupling between pressure and heat release rate fluctuations. We then de-scribe the effect of the Lewis number on primary acoustic instability in non-equidiffusive flames, where the diffusive thermal effects largely determine the internal flame structure. For a Lewis number below (above) unity, where the reaction rate increases (decreases) with reducing (increasing) reaction zone thickness, relatively strong (weak) acoustic sound is produced under the same coupling constant, because the chemical reaction rate becomes very sensitive (insensitive) to gas temperature fluctuations in the acoustic field. Finally, we obtain a linear relationship between the coupling constant and the average acoustic intensity, and results show that relatively large coupling constant is required to generate primary acoustic instability as the Lewis number increases. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.

Experimental investigation of the effects of cycloparaffins and aromatics on the sooting tendency and the freezing point of soap-derived biokerosene and normal paraffins
Long H. Duong, Osamu Fujita, Iman K. Reksowardojo, Tatang H. Soerawidjaja, Godlief F. Neonufa
FUEL, 185, 1, 855, 862, ELSEVIER SCI LTD, Dec. 2016, [Peer-reviewed]
English, Scientific journal, The effects of cycloparaffin and aromatic hydrocarbons when blended with soap-derived biokerosene (SBK) and normal paraffins (n-paraffins) on the sooting tendency and the freezing point are quantified to determine a method for improving the properties of SBK and n-paraffin fuels. In this study, SBK was derived from the saponification and dercarboxylation of coconut oil, and consists predominantly of n-paraffins with carbon chain lengths from C7 to C17. Dodecane, butylcyclohexane and butylbenzene were chosen as surrogate components for n-paraffins in SBK, cycloparaffins and aromatics, respectively. The total soot volume was measured from the light extinction at ambient conditions in a wick-fed laminar diffusion flame. The measured smoke point of the fuel was correlated with the required sooting tendency according to the jet fuel standard. The freezing point was measured using the JIS K2276 test method. The results show that butylcyclohexane affects the sooting tendency much lesser than butylbenzene when blended with SBK or dodecane. In contrast, butylcyclohexane decreases the freezing point more, as compared to butylbenzene, when blended with dodecane. Butylcyclohexane and butylbenzene have a similar trend of effect on the freezing point when blended with SBK or dodecane. Blending SBK or dodecane with butylcyclohexane matches the requirements of both smoke point and freezing point for jet fuel specified by ASTM D1655. Conversely, blending SBK or dodecane with butylbenzene does not meet these requirements. Therefore, given the tradeoff between sooting tendency and freezing point, cycloparaffins are considered more promising than aromatics for blending with SBK or n-paraffin fuels. (C) 2016 Elsevier Ltd. All rights reserved.

Limiting oxygen concentration (LOC) of burning polyethylene insulated wires under external radiation
Kyosuke Miyamoto, Xinyan Huang, Nozomu Hashimoto, Osamu Fujita, Carlos Fernandez-Pellob
FIRE SAFETY JOURNAL, 86, 32, 40, ELSEVIER SCI LTD, Nov. 2016, [Peer-reviewed]
English, Scientific journal, Electrical cables and harnesses have been identified as a potential source of fire in the spacecraft cabin. Future space missions may require spacecraft cabin environments to have elevated oxygen concentrations and reduced ambient pressures which could change the wire fire behaviors. In this work, a group of experiments is conducted to measure the flammability limit of polyethylene (PE) insulated wires under varying oxygen concentration and external radiation. Wires with different insulation dimensions, core conditions (with and without copper core) and insulations (LDPE, HDPE and black LDPE) are examined. Experiments show that external radiation extends the burning limit of the wire insulation to a lower limiting oxygen concentration (LOC) in a linear manner for all wire configurations. Comparison also reveals that the copper core acts as a heat sink to reduce the wire flammability, similar to its role in the ignition of wire insulation, while different from the heat source found in flame spread over the wire insulation. It is also observed that with the external radiation, LDPE insulated wire become less flammable than HDPE and black LDPE insulated wires, in contrast to the result without external radiation. A simple theoretical analysis shows that (1) the in-depth radiation through the semi-transparent LDPE to the copper core acts as an additional cooling to weaken the external radiative heating, and (2) the easier dripping of molten LDPE reduces its flammability. The results of this work provide valuable information about the fire risk of electrical wires under variable oxygen concentration and external heating from an adjacent fire. Thus, it may be useful toward upgrading the fire safety design and standards of future space missions.

Fire safety in space - Investigating flame spread interaction over wires
Jean-Marie Citerne, Hugo Dutilleul, Koki Kizawa, Masashi Nagachi, Osamu Fujita, Masao Kikuchi, Grunde Jomaas, Sebastien Rouvreau, Jose L. Torero, Guillaume Legros
ACTA ASTRONAUTICA, 126, 500, 509, PERGAMON-ELSEVIER SCIENCE LTD, Sep. 2016, [Peer-reviewed]
English, Scientific journal, A new rig for microgravity experiments was used for the study flame spread of parallel polyethylene-coated wires in concurrent and opposed airflow. The parabolic flight experiments were conducted at small length- and time scales, i.e. typically over 10 cm long samples for up to 20 s. For the first time, the influence of neighboring spread on the mass burning rate was assessed in microgravity. The observations are contrasted with the influence characterized in normal gravity. The experimental results are expected to deliver meaningful guidelines for future, planned experiments at a larger scale.
Arising from the current results, the issue of the potential interaction among spreading flames also needs to be carefully investigated as this interaction plays a major role in realistic fire scenarios, and therefore on the design of the strategies that would allow the control of such a fire. Once buoyancy has been removed, the characteristic length and time scales of the different modes of heat and mass transfer are modified. For this reason, interaction among spreading flames may be revealed in microgravity, while it would not at normal gravity, or vice versa. Furthermore, the interaction may lead to an enhanced spread rate when mutual preheating dominates or, conversely, a reduced spread rate when oxidizer flow vitiation is predominant.
In more general terms, the current study supports both the SAFFIRE and the FLARE projects, which are large projects with international scientific teams. First, material samples will be tested in a series of flight experiments (SAFFIRE 1-3) conducted in Cygnus vehicles after they have undocked from the ISS. These experiments will allow the study of ignition and possible flame spread in real spacecraft conditions, i.e. over real length scale samples within real time scales. Second, concomitant research conducted within the FLARE project is dedicated to the assessment of new standard tests for materials that a spacecraft can be composed of. Finally, these tests aim to define the ambient conditions that will mitigate and potentially prohibit the flame spread in microgravity over the material studied. (C) 2016 IAA. Published by Elsevier Ltd. All rights reserved.

Onset mechanism of primary acoustic instability in downward-propagating flames
Sung Hwan Yoon, Tae Joon Nob, Osamu Fujita
COMBUSTION AND FLAME, 170, 1, 11, ELSEVIER SCIENCE INC, Aug. 2016, [Peer-reviewed]
English, Scientific journal, This paper deals with the onset mechanism of primary acoustic instability of downward-propagating flames in a combustion tube. We focus on the effects of a coupling constant, beta M, where beta and M represent the Zel'dovich and Mach numbers, respectively, and the variation in the flame surface area. To change the coupling constant, various gas compositions for lean ethylene flames diluted with carbon dioxide or nitrogen are used. We obtain a linear relationship between the coupling constant and the average acoustic intensity, and the critical values of the coupling constants are acquired through linear approximation regarding the onset of the primary acoustic instability. Furthermore, we adopt the CO2 laser irradiation method to alter the shape of the flame front, and experimental results show that the variation in the flame surface area does not always cause spontaneous generation of the primary acoustic instability in initially non-vibrating flames. Furthermore, even in initially vibrating flat flames, the growth rate of the primary acoustic instability is not associated with the increase or decrease in the flame surface area in the present experiments. Finally, we also estimate the effects of acoustic losses on acoustic instability, and experimental results show that larger total acoustic losses tend to suppress acoustic vibration even at the same coupling constant. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Fire safety in space - beyond flammability testing of small samples
Grunde Jomaas, Jose L. Torero, Christian Eigenbrod, Justin Niehaus, Sandra L. Olson, Paul V. Ferkul, Guillaume Legros, A. Carlos Fernandez-Pello, Adam J. Cowlard, Sebastien Rouvreau, Nickolay Smirnov, Osamu Fujita, James S. T'ien, Gary A. Ruff, David L. Urban
ACTA ASTRONAUTICA, 109, 208, 216, PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2015, [Peer-reviewed]
English, Scientific journal, An international research team has been assembled to reduce the uncertainty and risk in the design of spacecraft fire safety systems by testing material samples in a series of flight experiments (Saffire 1, 2, and -3) to be conducted in an Orbital Science Corporation Cygnus vehicle after it has undocked from the International Space Station (ISS). The tests will be fully automated with the data downlinked at the conclusion of the test before the Cygnus vehicle re-enters the atmosphere.
The unmanned, pressurized environment in the Saffire experiments allows for the largest sample sizes ever to be tested for material flammability in microgravity, which will be based on the characteristics of flame spread over the surface of the combustible material. Furthermore, the experiments will have a duration that is unmatched in scale compared to earth based microgravity research facilities such as drop towers (about 5 s) and parabolic flights (about 20 s). In contrast to sounding rockets, the experiments offer a much larger volume, and the reduction in the oxygen concentration during the Saffire experiments will be minimal.
The selection of the experimental settings for the first three Saffire experiments has been based on existing knowledge of scenarios that are relevant, yet challenging, for a spacecraft environment. Given that there is always airflow in the space station, all the experiments are conducted with flame spread in either concurrent or opposed flow, though with the flow being stopped in some tests, to simulate the alarm mode environment in the ISS and thereby also to study extinguishment The materials have been selected based on their known performance in NASA STD-6001Test-1, and with different materials being classified as charring, thermally thin, and thermally thick. Furthermore, materials with non-uniform surfaces will be investigated. (C) 2014 IAA. Published by Elsevier Ltd. All rights reserved.

Flame spread over electrical wire with AC electric fields: Internal circulation, fuel vapor-jet, spread rate acceleration, and molten insulator dripping
Seung Jae Lim, Minkuk Kim, Jeong Park, Osamu Fujita, Sukho Chung
COMBUSTION AND FLAME, 162, 4, 1167, 1175, ELSEVIER SCIENCE INC, Apr. 2015, [Peer-reviewed]
English, Scientific journal, The effect of electric field on the characteristics of flame spread along a polyethylene (PE) insulated electrical wire was investigated experimentally by varying the AC frequency and voltage applied to the wire. The results showed that the flame spread rate was accelerated due to the convergence of electric flux near the end of wire, having three distinct regimes depending on applied voltage. In each regime, several subregimes could be identified depending on AC frequency. Flame shape (height and width) and slanted direction of the spreading flame were influenced differently. Fuel-vapor jets were ejected from the molten PE surface even for the baseline case without the application of an electric field; this could be attributed to the bursting of fuel vapor bubbles generated from internal boiling at the molten PE surface. An internal circulation of molten-PE was also observed as a result of non-uniform heating by the spreading flame. In the high voltage regime with a high AC frequency, excessive dripping of molten PE led to flame extinction. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Solid combustion research in microgravity as a basis of fire safety in space
Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 35, 3, 2487, 2502, ELSEVIER SCIENCE INC, 2015, [Peer-reviewed]
English, Scientific journal, This paper introduces fire safety standards for flammability evaluation of solid material intended for use in a spacecraft habitat. Two types of existing standards include material evaluation by pass/fail criteria corresponding to Test 1 of NASA STD 6001B and evaluation by a flammability index such as maximum oxygen concentration (MOC) corresponding to the improved Test 1. The advantage of the latter is the wide applicability of the MOC index to different atmospheres in spacecraft. Additionally, the limiting oxygen index (LOI) method is introduced as a potential alternative index for the evaluation using the improved Test 1 method. When criteria based on an index such as MOC or LOI are applied for material screening, the discrepancy of the index to the actual flammability limit in microgravity such as minimum limiting oxygen concentration (MLOC) is essential information for guaranteeing fire safety in space because material flammability can be higher in microgravity. In this paper, the existing research on the effects of significant parameters on material flammability in microgravity are introduced, and the difference between the limiting value in microgravity and the indices given by the standard test methods on the ground is discussed. Finally, on- going efforts to develop estimation methods of material flammability in microgravity according to normal gravity tests are summarized. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Study on one-dimensional steady combustion of highly densified biomass briquette (bio-coke) in air flow
Takero Nakahara, Hui Yan, Hiroyuki Ito, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 35, 3, 2415, 2422, ELSEVIER SCIENCE INC, 2015, [Peer-reviewed]
English, Scientific journal, Combustion experiments on cylindrical bio-coke (BIC), a highly densified biomass briquette, have been conducted to observe whether quasi-one-dimensional steady combustion can be attained in room temperature air flow. In the experiments, the air flow velocity was the main test condition and the fuel consumption rate when the bottom surface of the BIC sample burned was evaluated as the regression rate of the combustion zone at the bottom surface. In addition, one-dimensional calculations based on an energy equation at the combustion zone were conducted to understand the mechanism that results in steady combustion and predict the effect of water and volatile matter content in BIC on the extinction limit. The results showed that steady combustion of the BIC sample could be attained in 4.67 m/s or more, and, in contrast, extinction was observed in 3.82 m/s or less. The critical regression rate explained by the combustion zone temperature was shown, and the reason combustion becomes unsteady could be explained by the energy balance at the combustion zone. Though the main reason for extinction was radiation heat loss, the heat loss by water and volatile matter was not negligible. Therefore, the effect of water and volatile matter content on steady combustion must be considered. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Flame spread over electric wire with high thermal conductivity metal core at different inclinations
Longhua Hu, Yangshu Zhang, Kosuke Yoshioka, Hirokazu Izumo, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 35, 3, 2607, 2614, ELSEVIER SCIENCE INC, 2015, [Peer-reviewed]
English, Scientific journal, This paper reveals experimentally the flame spread rate (FSR) [both upward (concurrently) and downward (opposed)] over electric wire with high thermal conductivity metal core at different inclination angles, which is new in view of that previous works about such inclination effect are mainly focusing on the material (wood, PMMA......) where the conductivity through media itself is not so important. Polyethylene (PE) insulated copper (Cu) wires with inner core diameter (d(c)) of 0.30 mm, 0.50 mm 0.80 mm and insulation thickness (delta(p)) of 0.15 mm, 0.30 mm are studied with inclination angles ranged from -90 degrees to +90 degrees. Their behaviors are examined in both naturally normal (Hefei city with altitude of 50 m; 100 kPa) and a reduced (Lhasa city with altitude of 3650 m; 64 kPa) ambient pressure atmosphere. Results show that with increase in inclination angles from -90 degrees to 90 degrees, the FSR first decreases and then increases ("U" trend) with its value being lowest at nearly horizontal condition (0 degrees) in both pressures, which is quite different from what we normally know for other materials with low thermal conductivity. Two characteristic lengths, the flame base width (W-f) and the pyrolysis zone length (L-p), are found to account for this special variation behavior with their variation trend with inclination angle being consistent with that of FSR. A simplified heat balance analysis concerning core thermal conduction effect is performed to calculate the FSR in relation to these two characteristic lengths, thermal conductivity of the metal core as well as the effective convection heating of the wire by the flame base. The calculated FSR are shown to be in fairly good agreement with the measured values at different inclination angles for different inner core (wire) diameters in both ambient pressures. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

5-2-5 Studies on thermodynamical evaluation of oxy-fuel combustion and the regenerative combustion in industrial furnaces
SATO Kenichi, FUJITA Osamu
Proceedings of the Annual Conference of The Japan Institute of Energy, 24, 194, 195, The Japan Institute of Energy, 2015
Japanese, Thermodynamical potential of the oxy-fuel combustion with exhaust gas recycle has been studied in comparison with regenerative combustion furnace and normal air combustion. The energy consumption and the change in entropy were calculated for the purposes. The results showed that the thermodynamical potential of the oxy-fuel combustion could be competitive enough to the regenerative combustion according to the evaluation based on specific entropy production per unit industrial product.

Microgravity flammability limits of ETFE insulated wires exposed to external radiation
Andres F. Osorio, Ken Mizutani, Carlos Fernandez-Pello, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 35, 3, 2683, 2689, ELSEVIER SCIENCE INC, 2015, [Peer-reviewed]
English, Scientific journal, The present work studied the normal gravity (1 g) and microgravity (mu g) flame spread limits (LOC) of ETFE insulated copper wires exposed to an external radiant flux. Experiments with sample wires of a 0.50 mm copper core and 0.30 mm ETFE insulation thickness were conducted in oxygen concentrations ranging from 20% to 32% and external radiant fluxes from 0 to 25 kW/m(2). Microgravity experiments conducted in parabolic flights showed that mu g reduced the Limiting Oxygen Index of the material. The addition of an external radiant flux further extends the Limiting Oxygen Concentration (LOC) for flame spread over ETFE insulated wires. Microgravity reduced heat losses and allowed the flame to propagate in lower oxygen concentrations. The addition of an external radiant flux further compensates for lower flame temperatures in reduced oxygen concentrations and further extends the LOC of the material. Limiting Oxygen Index (LOI) results obtained with ETFE were also compared to available results with PE and show that mu g conditions have a larger impact in ETFE than PE. The results of this work are relevant given that the flammability of materials is routinely tested without considering the effects of environmental variables and according to the results presented in here may not be indicative of the absolute flammability limits. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Interaction Between Propagation Speed and Flame Structure in Downward Cellular Propagating Flame in a Combustion Tube with Co-2 Laser Irradiation
Kira Aguilar, Yoshikazu Taniyama, Hiroyuki Ito, Osamu Fujita
COMBUSTION SCIENCE AND TECHNOLOGY, 186, 10-11, 1434, 1446, TAYLOR & FRANCIS INC, Nov. 2014, [Peer-reviewed]
English, Scientific journal, This study investigates a downward propagating cellular flame to describe its transient phenomena induced by CO2 laser irradiation. An experimental investigation has been conducted in a combustion tube with C2H4 - O-2 - CO2 fuel rich mixtures at ambient temperature and atmospheric pressure. After ignition, a cellular flame is formed, and once CO2 laser irradiates the mixture, several motions can be observed. First, transition from cellular to smooth surface occurs as a consequence of the local increment of the flame speed. Then, as the laser is continuously irradiating, concave structure develops and finally new cells appear around this concave structure because buoyancy overcomes the initial enhancement of the propagation speed, decelerating it close to the initial value where cellular flame can exist. Therefore, it is concluded that CO2 laser actively controls the evolution of the propagating flame shape.

Initiation and formation of the corrugated structure leading to the self-turbulization of downward propagating flames in a combustion tube with external laser absorption
Yoshikazu Taniyama, Osamu Fujita
COMBUSTION AND FLAME, 161, 6, 1558, 1565, ELSEVIER SCIENCE INC, Jun. 2014, [Peer-reviewed]
English, Scientific journal, Combustion tube (length 45 cm, inner diameter 5 cm) experiments with flames of premixed gas of C2H4/CO2-O-2 (Le < 1) were conducted. The flame fronts propagated downward to the closed bottom of an open-ended tube. An initially steadily propagating flat flame was deformed by an external laser irradiation method to investigate its evolution under the interaction with acoustic vibration. Results showed that the locally deformed flame evolved into a corrugated structure at the flame front followed by self-turbulization. The process to form this corrugated structure was investigated in detail based on the images captured using high-speed cameras. From the observations, a possible mechanism for the initiation of the corrugated structure, explained mainly by periodic acoustic acceleration, was proposed. Then, according to the mechanism an alternative definition for the inverse Froude number is proposed in this work and used as criterion for the initiation of the corrugated flame structure. To prove the validity of the criterion two mixtures having different flame speed were tested and it was confirmed that the criterion provided transition condition very well for both tested mixtures. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

A study on developing aviation biofuel for the Tropics: Production process-Experimental and theoretical evaluation of their blends with fossil kerosene
Thong D. Hong, Tatang H. Soerawidjaja, Iman K. Reksowardojo, Osamu Fujita, Zarrah Duniani, Mai X. Pham
CHEMICAL ENGINEERING AND PROCESSING, 74, 124, 130, ELSEVIER SCIENCE SA, Dec. 2013, [Peer-reviewed]
English, Scientific journal, In the present work, the production process of bio-jet paraffins is appropriately proposed according to the conditions of the socioeconomic situations, the current technologies of biofuel production and the available feedstock sources for the tropical countries. The blending process of bio-kerosene which is a mixture of bio-jet paraffins and fossil kerosene is also displayed. The two prototypes of bio-paraffins (Bio-P1 and Bio-JP2), which were manufactured in Indonesia following the proposed production process, are used for making bio-kerosenes in current study. The theoretical and experimental investigations have been carried out to evaluate and identify the critical properties of bio-kerosenes: distillations, freezing point, lower heating value, density, flash point and viscosity to ensure ASTM criteria of jet fuel. The results show it can be blended directly 5% volume of Bio-P1 or 10% volume of Bio-JP2 to commercial Jet A-1 for powering aviation gas turbine engines without redesigning fuel system or fuel supply infrastructure. The use of these bio-paraffins not only reduces CO2 lifecycle but also significantly decreases emissions of sulfur compounds (SOx). With preliminary achievements of this work, it is no doubt about the feasibility of developing aviation alternative fuels according to the proposed production process for the tropical countries. (c) 2013 Elsevier B.V. All rights reserved.

Extinction limits of spreading flames over wires in microgravity
Shuhei Takahashi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita
COMBUSTION AND FLAME, 160, 9, 1900, 1902, ELSEVIER SCIENCE INC, Sep. 2013, [Peer-reviewed]
English, Scientific journal, Tests with flames spreading over wires in microgravity were performed at external opposed flow conditions from 60 to 200 mm/s to examine the influence of flow velocity on the extinction limit. In the experiments, low density polyethylene insulated Nickel-chrome and Copper wire samples were used. The experiments were conducted both in normal gravity and microgravity attained by parabolic flights. The experimental results are discussed based on non-dimensional numbers developed by Takahashi et al. This study added the heat conduction through the wire insulation to the inner core to their model, which is considered as a heat loss term arising due to the presence of the inner core. Further the effect of curvature of the sample is taken into consideration. From the results of the experiments in normal gravity, there was a low oxygen limit for Copper wire at around 125 mm/s. However there was no low oxygen limit for Nickel-chrome wire; the limits of the oxygen concentration decreased monotonically with decreases in the external flow velocity. The non-dimensional number implies that the decrease in inner core temperature around the preheat zone occurring with Copper wire plays a role in the change in low oxygen limits. Further, in the external flow velocity range investigated here, there was no low oxygen limit in microgravity with the Copper wire. This might arise due to the changes in the flame shapes by gravity. The heat input from flame to the wire is supposed to increase in microgravity because the wire is surrounded by flame due to inhibited natural convection. This increased heat input might help the increase of the inner core temperature around the preheat zone. For this reason, there is a possibility that the low oxygen limit with Copper wire in microgravity exists at lower flow velocity than that in normal gravity. (c) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Investigation of applying DC electric field effect on carbon nanotube synthesis
Kohta Masunaga, Hiroyuki Ito, Osamu Fujita
Asia-Pacific Journal of Chemical Engineering, 8, 2, 246, 253, Mar. 2013, [Peer-reviewed]
English, Scientific journal, Flame synthesis is focused as a carbon nanotube (CNT) formation method in the present study. Although promotion of CNT formation by applying electric field to flame synthesis method has been reported, it is difficult to distinguish whether the promotion of CNT growth is caused by the effect of electric field on the condition near the flame or whether it is caused by other effects accompanied with electric field application so far. Therefore, the influence of the change in condition near the flame accompanied with the DC electric field application on the CNT formation was analyzed in this study. Moreover, the effect of the electric field application on the CNT growth rate and the carbon processing rate on the catalyst was investigated in the chemical vapor deposition method. In the flame synthesis method, the significant promotion of CNT growth is observed, whereas there is less effect of the electric field on the condition such as gas temperature and composition. In the chemical vapor deposition method, the CNT length increases with increasing the intensity of the electric field. Moreover, extension of the catalyst lifetime and increase in the CNT growth rate are found with applying the electric field. © 2012 Curtin University of Technology and John Wiley &
Sons, Ltd.

Downstream interaction between stretched premixed syngas-air flames
Tae Hyung Kim, Jeong Park, Osamu Fujita, Oh Boong Kwon, Jong Ho Park
FUEL, 104, 739, 748, ELSEVIER SCI LTD, Feb. 2013, [Peer-reviewed]
English, Scientific journal, Effect of strain rate on flame extinction is numerically investigated in downstream interaction among lean (rich) and lean (rich) premixed as well as partially premixed (50% H-2 + 50% CO)-air flames. The strain rate varies from 30 to 4671 s(-1) until interacting flames cannot be sustained anymore. Flame stability diagrams mapping lower and upper limit fuel concentrations for flame extinction as a function of strain rate are explored. It is shown that significant increase of strain rate makes even the upper rich extinction boundary be slanted due to strong chemical interaction. The lower extinction boundary can be also extended to rich fuel concentrations over the stoichiometric mixture condition when strain rate significantly increases. The lower and upper extinction boundaries, mainly caused by the conductive heat loss from the stronger flame to ambience, become narrower and narrower in increasing strain rate. The results also show that the extinction boundaries with positive flame speed are extended and then reduced in increasing strain rate, thereby leading to an island of extinction boundary and subsequently being changed into a point on the symmetric fuel concentration line. The detailed explanations on those flame extinction characteristics in the stability diagrams are made through analysis of the flame structures in increase of strain rate. The mechanism of flame extinction is also proposed and discussed in detail. (C) 2012 Elsevier Ltd. All rights reserved.

Prediction Performance of Chemical Mechanisms for Numerical Simulation of Methane Jet MILD Combustion
Yu Jeong Kim, Chang Bo Oh, Osamu Fujita
ADVANCES IN MECHANICAL ENGINEERING, 2013, SAGE PUBLICATIONS LTD, 2013, [Peer-reviewed]
English, Scientific journal, The prediction performance of five chemical mechanisms (3-STEP, WD4, SKELETAL, DRM-19, and GRI-2.11) was investigated to confirm their suitability for use in numerical simulations of methane combustion in moderate or intense low-oxygen dilution (MILD). A wall-confined jet geometry was introduced to simulate MILD combustion. The oxygen level in the coflowing air was adjusted by mixing the air with combustion products. Each chemical mechanism was analyzed with respect to the flame structure and main product, including CO and NO; the emission indices for CO were also discussed. The temperature distributions and heat-release rates predicted by the chemical mechanisms were similar when the flames were stably attached to the fuel jet exit. The temperature distributions and heat-release rates were dependent on the flame liftoff characteristics, as were the CO and NO emissions. The NO concentration predicted by GRI-2.11 was lower than those predicted using other chemical mechanisms, although DRM-19 predicted a relatively similar value. The emission indices for NO (EINO) and CO (EICO) predicted by each chemical mechanism decreased with increasing dilution rate. The predicted EICO had a negative value even at a small dilution rate, which implies that some of the CO supplied to the air stream is consumed during MILD combustion.

Soot Characteristics of Kerosene and Its Blend with Aviation Bio-Paraffins in Diffusion Flames　　　　　　　　　　　　　　　
Thong D. Hong, Osamu Fujita, Tatang H. Soerawidjaja, Iman K. Reksowardojo, Zarrah Duniani, Mai X. Pham
International Journal of Engineering & Technology (IJET-IJENS), 13, 05, 2227, 2232, 2013, [Peer-reviewed]
English, Scientific journal

Study on unsteady molten insulation volume change during flame spreading over wire insulation in microgravity
Shuhei Takahashi, Hiroyuki Takeuchi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 34, 2, 2657, 2664, ELSEVIER SCIENCE INC, 2013, [Peer-reviewed]
English, Scientific journal, Tests with flames spreading over wire insulation in microgravity were performed at varying external opposed flow conditions to examine the influence of flow velocity in the time dependent volume change of molten insulation. In the experiments, low density polyethylene insulated Nickel-chrome wire specimens were used and the oxygen concentration was fixed at 30% (N-2 balanced). The results show that the time dependent changes in molten insulation volume are related to the opposed flow velocity. Further, as opposed flow velocity increases, the volume change rate decreases monotonically. By subtracting the volume change rate from the volume supply rate from the solid part to the molten part, which is calculated by multiplying the rate of spreading of molten insulation at the leading edge by the cross sectional area of the insulation, a pyrolysis volume rate for the polyethylene was established. The pyrolysis volume rate is defined as the amount of consumed molten insulation volume per unit time. After these calculations, it was found that the pyrolysis volume rate increases monotonically with increases in the opposed flow velocity. Further, numerical calculations of time dependent volume change in the molten insulation at different flow velocities were made. The numerical results show good agreement with the experimental results of the molten insulation volume change during the 0-4.5 s of microgravity measured here. By using the numerical calculations for this initial short period, the time dependent volume change in molten insulation during longer-term microgravity is predicted. The calculated results show that the volume finally reaches a steady state value in flow velocities of 10-250 mm/s investigated here. These results provide insight into the mechanism of flame spreading over wire insulation, especially the unsteadiness of the flame in flame spreading events. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Ignition limits of short-term overloaded electric wires in microgravity
Yoshitomo Takano, Osamu Fujita, Naoki Shigeta, Yuji Nakamura, Hiroyuki Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 34, 2, 2665, 2673, ELSEVIER SCIENCE INC, 2013, [Peer-reviewed]
English, Scientific journal, Ignition phenomena of electric wires carrying short-term excess electric currents were investigated in microgravity with experiments and calculations. Microgravity experiments were conducted in 100 m and 50 m drop towers and calculations were carried out with a one dimensional cylindrical coordinate system. The experimental results showed that the limiting oxygen concentration (LOC) under a given electric current was much lower in microgravity than that in normal gravity except for extremely large electric current overload cases. According to the calculations, the supplied electric current, the Joule energy supplied to the wire, determined the amount of pyrolysis gas from the insulation and the resulting thickness of the gaseous fuel layer around the sample in gas phase increased. The increased fuel layer thickness resulted in a longer ignition delay, which leads to lower LOC. The changes in the estimated LOC changed as a function of supplied energy and agreed well with the experimental results. Further, the minimum ignition energy causing ignition (ignition limit) is nearly constant under a constant oxygen concentration, which supports experimental findings in previous research. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Ignition limit of electric wire insulation with continuous excess current in several microgravity periods
Naoki Shigeta, Hiroyuki Ito, Osamu Fujita
43rd International Conference on Environmental Systems, American Institute of Aeronautics and Astronautics Inc., 2013
English, International conference proceedings, Overloading of an electric wire is a potential cause of fire in space craft. So it is important to know the ignition limit in long term μG environment such as in space craft on orbit. In this research, therefore, the effect of μG period on ignition limit defined as lowest applied power for ignition is investigated by experiments. The μG environment is attained by parabolic flights
the available μG period is around 20 s and two different drop towers
the periods are 4.5 s and 2.5 s. In these experiments, electric current is applied to a wire continuously during μG period. The test results show that ignition limit decreases as μG period is increased. However, despite of decrease in ignition limit as μG period is increased, the ignition energy, defined as total Joule energy for ignition, in μG doesn't change significantly. It means that the minimum amount of Joule energy is almost constant for ignition.

Quantitative infrared image analysis of simultaneous upstream and downstream microgravity flame spread over thermally-thin cellulose in low speed forced flow　　　　　　　　　　　　　　　
S. L. Olson, J. R. Lee, O. Fujita, M. Kikuchi, T. Kashiwagi
8th US National Combustion Meeting 2013, 4, 3654, 3672, Western States Section/Combustion Institute, 2013
English, International conference proceedings, The effect of low velocity forced flow on microgravity flame spread is examined using quantitative analysis of infrared video imaging. The objective of the quantitative analysis is to provide insight into the mechanisms of flame spread in microgravity where the flame is able to spread from a central location on the fuel surface, rather than from an edge. Surface view calibrated infrared images of ignition and flame spread over a thin cellulose fuel were obtained along with a color video of the surface view and color images of the edge view using 35 mm color film at 2 Hz. The cellulose fuel samples were mounted in the center of a 12 cm wide by 16 cm tall flow duct and were ignited in microgravity using a straight hot wire across the center of the 7.5 cm wide by 14 cm long samples. Four cases, at 1 atm. 35%O2 in N2, at forced flows from 2 cm/s to 20 cm/s are presented here. This flow range captures flame spread from strictly upstream spread at low flows, to predominantly downstream spread at high flow. Surface temperature profiles are evaluated as a function of time, and temperature gradients for upstream and downstream flame spread are measured. Flame spread rates from IR image data are compared to visible image spread rate data. IR blackbody temperatures are compared to surface thermocouple readings to evaluate the effective emissivity of the pyrolyzing surface. Preheat lengths and pyrolysis lengths are evaluated both upstream and downstream of the central ignition point. A surface energy balance estimates the net heat flux from the flame to the fuel surface along the length of the fuel. Surface radiative loss and gas-phase radiation from soot are measured relative to the net heat feedback from the flame. At high surface heat loss relative to heat feedback, the downstream flame spread does not occur.

Competition between buoyancy effects and propagation speed on flame structure in a downward cellular propagating flame in a combustion tube with time controlled CO2 laser irradiation　　　　　　　　　　　　　　　
Kira Aguilar, Yoshikazu Taniyama, Hiroyuki Ito, Osamu Fujita
Proceedings of the 9th Asia-Pacific Conference on Combustion, ASPACC 2013, Korean Society of Combustion, 2013
English, International conference proceedings, Competition between the effects of buoyancy and propagation speed is observed on a cellular flame that propagates downwardly in a combustion tube, when time controlled CO2 laser irradiation is given to the flame. The tube is aligned vertically and filled with premixed gas (C2H 4-O2-CO2) at atmospheric pressure and ambient temperature. Flame front propagates towards the unburned mixture and is exposed to time controlled CO2 laser power input that preheats the unburned mixture ahead of the flame front and locally increases the combustion velocity. With the CO2 laser irradiation, transition from cellular to smooth flame occurs. Then, after irradiation is stopped, concave structure towards the unburned gas is formed. Finally, concave structure fully disappears and the flame returns to its initial cellular state. We have compared the transition time and the delay time for every motion to discuss the relative importance of combustion velocity enhancement by laser irradiation, to the buoyancy force in the process of such transient phenomena.

Global equivalence and dilution ratio effects on the flame structure and pollutants emission of methane MILD jet combustion　　　　　　　　　　　　　　　
Yu Jeong Kim, Chang Bo Oh, Osamu Fujita
Proceedings of the 9th Asia-Pacific Conference on Combustion, ASPACC 2013, Korean Society of Combustion, 2013
English, International conference proceedings, The MILD combustion and pollutant emission characteristics were investigated computationally. The dilution rate (Ω) of exhaust gas in the air-stream were adjusted to investigate the effects of those parameters on the MILD combustion in wall-confined jet flow field. The global equivalence ratio(Φg) effects on the flame structure and pollutants emission were discussed. As a results, the high-temperature region disappeared gradually as the mixing rate increased for fixed air-stream temperature. For the condition where flame can be stabilized near the fuel nozzle, the flame length was reduced with increasing the global equivalence ratio for fixed dilution rate. The EICO and EINO decreased with the dilution rate. It was found that the EICO trend with the dilution ratio was independent of the Φg. For Ω <
0.3, the EINO was also independent of the Φg, however, the EINO for Φg = 0.9 decreased more rapidly than for more lean conditions.

Studies on Solid Biomass Combustion : Combustion Characteristics of Highly Densified Biomass Briquette
ITO Hiroyuki, SAKAI Yuto, NAKAHARA Takero, IDA Tamio, FUJITA Osamu
Journal of Smart Processing, 1, 2, 36, 43, Smart Processing Society for Materials, Environment & Energy (High Temperature Society of Japan), Feb. 2012, [Peer-reviewed]
Japanese, Scientific journal

Numerical simulation of the pyrolysis of solid waste in an externally heated rotary kiln
Teruyuki Okazaki, Tomoko Suzuki, Kenji Yamamoto, Hiroyuki Nakata, Osamu Fujita, Nobuyuki Oshima
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 78, 786, 338, 352, 2012, [Peer-reviewed]
Japanese, Scientific journal, A computational model was developed to predict the pyrolysis process of municipal solid waste in externally heated rotary kiln. The model was calculated assuming solid waste and gas are one-dimensional flow. The heat transfer coefficient among solid waste, gas and inner cylinder of kiln, which is variously affected by kiln structure and operation condition, was acquired by a scale model examination. A flexible computational grid was adopted in the model, which could change its shape according to the height of solid waste layer in each time step. The accuracy of this model was verified by comparison with the pilot scale experiments and the actual plant data. The predicted transient temperature profile is in good agreement with experimental data. Compared to the actual plant data, temperature prediction error is less than 10% at inner cylinder wall, pyrolysis gas, and solid waste. © 2012 The Japan Society of Mechanical Engineers.

Formation characteristics of high-density and high-hardness new briquette based on herby biomass
Satoru Mizuno, Tamio Ida, Manabu Fuchihata, Kunihiko Namba, Atsushi Kakosaka, Osamu Fujita
Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy, 91, 1, 41, 47, 2012
Japanese, Scientific journal, The aim of the lapanese cabinet council's 'Biomass Nippon Strategy' is to increase the utilization of biomass as one of the ways to reduce the dependence on fossil resources. However, there are various problems associated with the use biomass, one of which is the cost associated with the collection and transportation of biomass. Biomass has high moisture content and low bulk density. The biomass solidification technology developed by Ida et al. partly aims to solve the transportability problem. This study shows physical properties of high density and hardness of the new briquette produced from herby biomass. The relationship between apparent density and maximum compressive strength and an effect on the maximum compressive strength by black colorization are considered. Also, an attempt is made to explain the effect on properties of the briquette by hemi-cellulose and lignin in the region before semi-carbonized region. As a result, the relation between the apparent density and the compressive strength shows that maximum value exists as characteristics of the herby briquette. The maximum apparent density for all processing conditions is 1.38 g/cm3 at the initial moisture 0.10 kg/kg-wet -processing temperature 473 K. The maximum compressive strength for all processing conditions is 127 MPa at the initial moisture 0.05 kg/kg-wet -processing temperature 453 K. Furthermore, the effect of black colorization indicates that when the area of black colorization is increased for the surface of herby biomass briquette by increased in the processing temperature, the maximum compressive strength is decreased due to reduction in the adhesion of lignin. Consequently, high-density and high-hardness of the new briquette can be controlled by the initial moisture and the processing temperature.

Ignition Behavior of Bio-Coke (Highly Densified Biomass Fuel) in High-Temperature Air Flows
Hiroyuki Ito, Yuto Sakai, Tamio Ida, Yuji Nakamura, Osamu Fujita
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, 6, 1, 111, 122, JAPAN SOC MECHANICAL ENGINEERS, 2011, [Peer-reviewed]
English, Scientific journal, The ignition behavior of a newly developed biomass briquette, Bio-coke (BIC), is investigated. The fuel has unique features such as economical advantages for its versatility of biomass resources, high volumetric calorific value because of its high density (1300 kg/m(3); twice or more than that of ordinary wood pellets) and high mechanical strength. The ignition characteristics of cylindrical BIC blocks (48 mm in diameter and 85 mm in length), important when using the fuel in actual combustion furnaces, are investigated in high temperature air flows (473-873 K, 550-750 NL/min.). In the experiments, preheated air is blown onto the bottom surface of BIC cylinders and the ignition behavior of the bottom surface is observed monitoring the surface temperature as well as the time dependent mass loss rates. The results show two ignition modes; (1) solid surface ignition preceding gas-phase ignition in high air temperature conditions (T >= 598K), and (2) gas-phase ignition accompanied by simultaneous surface ignition occurring at relatively low air temperature conditions. The appearance of each mode depends on the preheated air supply condition in terms of the air temperature, flow velocity, and moisture content of the fuel. The rate of evolution of volatile gases is closely correlated with the temperature distribution inside the BIC briquette which depends on the heating rate, implying that variations in the temperature distribution inside the fuel could be one reason for the appearance of the observed ignition modes. It is suggested that the temperature distribution inside the fuel has to be taken into account in the control of the ignition behavior of BIC briquettes.

Effect of AC electric fields on flame spread over electrical wire
M. K. Kim, S. H. Chung, O. Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 33, 1, 1145, 1151, ELSEVIER SCIENCE INC, 2011, [Peer-reviewed]
English, Scientific journal, The effect of electric fields on the characteristics of flame spread over insulated electrical wire has been investigated experimentally by varying AC voltage and frequency applied to the wire in the normal gravity condition. The polyethylene (PE) insulated electrical wire was placed horizontally on electrically non-conducting posts and one end of the wire was connected to the high voltage terminal. Thus, the electrical system is the single electrode configuration. The wire was ignited at one end and the flame spread rate along the wire has been measured from the images using a video camera. Two distinct regimes existed depending on the applied AC frequency. In the low frequency regime, the flame spread rate decreased with the frequency and voltage. While in the high frequency regime, it decreased initially with voltage and then increased. At high frequency, the spread rate was even over that without applying electric fields. This result implies that fire safety codes developed without considering the effect of electric fields may require modifications. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Transition of flat flames to turbulent motion induced by external laser irradiation
June Sung Park, Osamu Fujita, Yuji Nakamura, Hiroyuki Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 33, 1, 1105, 1112, ELSEVIER SCIENCE INC, 2011, [Peer-reviewed]
English, Scientific journal, Experiments with flames premixed C2H4/CO2-O-2 (Le < 1) in a tube have been conducted. The mixture was ignited at the top, open end of the tube, and a flame front propagated downward toward the closed end of tube. To investigate details of motion of flame tip fluctuations at the initial moment of irradiating the CO2 laser light, a completely flat flame front was considered a default flame, corresponding to the primary acoustic instability as reported by Searby [1]. The laser exposure to the mixture induced local flame front deformation, resulting in a strong turbulent flame transforming eventually via the secondary acoustic instability. To elucidate the effect of the flame curvature, the flame velocity and curvature prior to establishment of the secondary acoustic instability were analyzed using a high speed camera. The results showed a sudden acceleration of the flame tip front during the advancing period. This was followed by a time lag between the flame velocity and curvature, indicating an increase in the flame velocity even with the decreasing flame curvature. These behaviors can be explained by selective acceleration at the center of the flame by an acoustic field and diffusive-thermal effects at a critical curvature beyond which flame extinction occurs. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Ignition of electrical wire insulation with short-term excess electric current in microgravity
Osamu Fujita, Takeshi Kyono, Yasuhiro Kido, Hiroyuki Ito, Yuji Nakamura
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 33, 2, 2617, 2623, ELSEVIER SCIENCE INC, 2011, [Peer-reviewed]
English, Scientific journal, Ignition phenomena of overloaded electric wires have been investigated in microgravity as basic information for fire safety in space. Microgravity experiments were conducted at MGLAB (Micro Gravity Laboratory of Japan) to provide 4.5 s of microgravity time. In the experiments the current supply duration was selected as the main test parameter to simulate the status of the circuit breaker shortly after the overload occurs. Other important test parameters were the surrounding oxygen concentration and the supplied electric current amount. The results showed that the microgravity environment significantly increases the ignition probability, including the occurrence of delayed ignition and extended ignition limits, with large electric currents when compared with the situation under normal earth based gravity. The increase in the ignition probability is explained by decreases in the minimum ignition energy in microgravity interacting with the ignition mechanism. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

COMBUSTION OF BIO-COKE (HIGHLY DENSIFIED BIOMASS FUEL) BLOCK IN HIGH-TEMPERATURE AIR FLOW
Hiroyuki Ito, Yuto Sakai, Tamio Ida, Yuji Nakamura, Osamu Fujita
PROCEEDINGS OF THE ASME/JSME 8TH THERMAL ENGINEERING JOINT CONFERENCE 2011, VOL 2, 83, 92, AMER SOC MECHANICAL ENGINEERS, 2011, [Peer-reviewed]
English, International conference proceedings, Bio-coke (BIC, highly densified biomass briquette), a newly developed biomass fuel as an alternative to coal coke which utilized in blast furnace, is employed in this study. This fuel is manufactured in highly compressed and moderate temperature conditions and has advantages in its versatility of biomass resources, high volumetric calorific value and high mechanical strength. Japanese knotweed is chosen as a biomass resource and is shaped into cylinder (48 mm in diameter and 85 mm in length). One of the most important characteristics of BIC is its high apparent density (1300 kg/m(3); twice or more than that of an ordinary wood pellet).
In the present study, combustion characteristics of a single BIC fuel in high temperature air flow (473-873 K, 550-750 NL/min.) are investigated. Air is preheated and blown to the bottom surface of the BIC. Ignition and subsequent combustion behavior are observed with monitoring gas temperature near the BIC, surface and inside the BIC temperature, and time dependent mass loss of the BIC is measured.
In the case with low air temperature, low heat flux from the fuel surface leads to the broad temperature distribution inside the BIC accompanied by the increase in ignition delay time and, then, once ignition takes place degradation rate becomes larger than the case with high temperature air. On the other hand, mass loss rate for the case of solid surface combustion in the high temperature air does not depend on the air temperature but does depend on the air flow rate, which is a result of reduced degradation rate relating to narrow temperature distribution in depth caused by short ignition delay time. Consequently, it is suggested that the history of preheating, i.e. the preheated condition which is determined by air temperature and air flow rate, is an essential factor to determine the ignition mode in the early stage of BIC combustion and the mass burning velocity in the period of main combustion with flame. It is found that the mass loss rate of BIC in the gas-phase combustion period increases with decrease in supplied air temperature in this study.

Phenomena in oscillating downward propagating flames induced by external laser irradiation method
June Sung Park, Osamu Fujita, Teruaki Honko, Yuichiro Yamada, Hiroyuki Ito, Yuji Nakamura
EXPERIMENTAL THERMAL AND FLUID SCIENCE, 34, 8, 1290, 1294, ELSEVIER SCIENCE INC, Nov. 2010, [Peer-reviewed]
English, Scientific journal, Experiments in C(2)H(4)/CO(2)-O(2) premixed flames (Le < 1) propagating downwardly in a tube have been conducted to observe transition phenomena from laminar flame front to turbulent flame propagation triggered by external laser irradiation method. To investigate the exact motions of flame tip fluctuation at the initial moment of irradiating CO(2) laser, the completely flat flame front is selected as a default flame, which is corresponding to the primary acoustic instability as reported by Searby (1992) [1].
According to the time-resolved observation, the flame front exposed to CO(2) laser beam shows extremely unstable flame motions in which highly curved flame front towards unburned mixture is subject to diffusive-thermal instability. Then, the sudden enhanced burning state (increased flame surface) caused by flame instability induces the secondary acoustic instability which is akin to the observation in Ref. [1]. In the present study, we report the detailed descriptions of flame fronts on the transient behaviors leading the primary acoustic instability to turbulent motions actively induced by the absorption of externally irradiated CO(2) laser beam. (C) 2010 Elsevier Inc. All rights reserved.

高温空気流中におけるバイオコークス燃料の着火挙動
伊東弘行, 酒井雄人, 藤田修, 中村祐二, 井田民男
高温学会誌, 36, 3, 25, 26, May 2010, [Peer-reviewed]
Japanese, Scientific journal

Observation of Flame Spreading over Electric Wire under Reduced Gravity Condition Given by Parabolic Flight and Drop Tower Experiments
Yosuke ONISHI, Osamu FUJITA, Kei AGATA, Hiroyuki TAKEUCHI, Yuji NAKAMURA, Hiroyuki ITO, Masao KIKUCHI
Transaction of the JSASS Aerospace Tech. Japan, Vol.8, 27, 19, 24, THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, 2010, [Peer-reviewed]
English, Scientific journal, Ground-based, microgravity experiments attained by aircraft parabolic flight and drop tower on flame spread phenomenon over electric wire are performed. These are the preliminary tests for expected long-term microgravity experiments by sub-orbital or on orbit microgravity experiment. The main objectives of this study are (1) to confirm the apparatus can be work properly in microgravity and (2) to show the necessity of long-term microgravity experiments in order to observe the unsteady phenomenon. The flame spread rate and the total soot volume are important items as fundamental characteristics of the spreading flame. From the parabolic flight test, which can provide relatively long microgravity period, it is confirmed that the apparatus can work properly in microgravity. On the other hand, the quality of microgravity provided by aircraft is fair including G-jitters, and dependable data in the slow external flow velocity regime is hardly expected. Flame spread rate and the total soot volume are measured by drop tower, which can provide 10^-4G microgravity environment. Although, in some conditions, the flame spread phenomenon seems to reach steady-state within the available microgravity time with the drop tower (∼ five seconds), the phenomenon includes periodical change in flame shape in reality. Consequently, to confirm the actual steadiness of the spread phenomenon, at least 10^-4G microgravity environment and long-term microgravity environment is necessary.

Joule Energy for Onset of Wire Ignition given by Short-term Excess Electric Current in Microgravity
FUJITA Osamu, KYONO Takeshi, KIDO Yasuhiro, ITO Hiroyuki, NAKAMURA Yuji
JASMA : Journal of the Japan Society of Microgravity Application, 26, 4, 374, 374, 19 Oct. 2009
English

Numerical simulation on soot deposition process in laminar ethylene diffusion flames under a microgravity condition
Jae Hyuk Choi, Junhong Kim, SangKyu Choi, Byoung-Ho Jeon, Osamu Fujita, Suk Ho Chung
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, 23, 3, 707, 716, KOREAN SOC MECHANICAL ENGINEERS, Mar. 2009, [Peer-reviewed]
English, Scientific journal, A numerical study on soot deposition in ethylene diffusion flames has been conducted to elucidate the effect of thermophoresis on soot particles under a microgravity environment. Time-dependent reactive-flow Navier-Stokes equations coupled with the modeling of soot formation have been solved. The model was validated by comparing the simulation results with the previous experimental data for a laminar diffusion flame of ethylene (C(2)H(4)) with enriched oxygen (35% O(2) + 65% N(2)) along a solid wall. In particular, the effect of surrounding air velocity as a major calculation parameter has been investigated. Especially, the soot deposition length defined as the transverse travel distance to the wall in the streamwise direction is introduced as a parameter to evaluate the soot deposition tendency on the wall. The calculation result exhibits that there existed an optimal air velocity for the early deposition of soot on the surface, which was in good agreement with the previous experimental results. The reason has been attributed to the balance between the effects of the thermophoretic force and convective motion.

Research on the relation of flame front curvature and oscillatory flame propagation by external laser irradiation method
Masakazu Tsuchimoto, Osamu Fujita, Teruaki Honko, Yuji Nakamura, Hiroyuki Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 32, 1003, 1009, ELSEVIER SCIENCE INC, 2009, [Peer-reviewed]
English, Scientific journal, Oscillatory propagation phenomena of ethylene premixed gas induced by absorption of externally supplied CO(2) laser was investigated. Premixed gas was filled in a combustion tube of 50 null in diameter at 0.1 MPa and CO(2) laser beam of different diameter was irradiated along the center axis of the tube. The experimental results showed that the flame front curvature was controlled by the irradiated beam diameter and had strong effect on the oscillatory propagation behavior. When the beam diameter is narrow, the flame oscillation phenomena clearly appeared and the oscillation frequency became larger with increased flame front curvature. On the other hand, oscillation phenomena could not be observed when beam diameter was lager than a certain value. According to the time-resolved observation, it was found that the flame front curvature fluctuated with time when oscillatory propagation appeared and the instant of the maximum curvature presence corresponded to the instant of flame propagation deceleration or pause. The observed results could support the mechanism of the oscillation propagation proposed in the previous study, which included the relation of the flame front curvature and thermal-diffusive instability. (c) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Flame spread over electric wire in sub-atmospheric pressure
Yuji Nakamura, Nobuko Yoshimura, Hiroyuki Ito, Keisuke Azumaya, Osamu Fujita
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 32, 2559, 2566, ELSEVIER SCIENCE INC, 2009, [Peer-reviewed]
English, Scientific journal, Flame spread along the single wire harness (thin-metal wire with coating of polyethylene film) in sub-atmospheric pressure has been examined experimentally to gain better understandings of the electric fire ill the aircraft and space habitats. Two kinds of sample Wires, made by nickel-chrome (NiCr) and iron (Fe) as core metal, are used in this study. Ambient gas is fixed as air and total pressure is varied from atmospheric to sub-atmospheric (100-20 kPa). As the pressure decreases. flame shape changes from typical "teardrop" to "oval" and flame becomes less-luminous irrespective of the materials of the wire. It turns out that the dependence of the spread rate on pressure varies with the materials of the wire: when the pressure decreases, the spread rate of NiCr-harness monotonically increases, whereas that of Fe-harness mostly remains as constant. From the simple thermal-length analysis, it is proposed that there are two modes in the spread depending oil the controlling factor: one is "wire-driven mode" (the spread is mainly governed by the thermal input through the wire) and the other is "flame-driven mode" (the spread is mainly governed by the thermal input from the flame). observed two cases (NiCr- and Fe-harness) would be categorized to the latter and former modes, respectively. (c) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Effect of Heat Radiation from Soot on Flame Spread of Wire Insulation under Microgravity
AGATA Kei, ONISHI Yosuke, FUJITA Osamu, NAKAMURA Yuji, ITO Hiroyuki, KIKUCHI Masao
JASMA : Journal of the Japan Society of Microgravity Application, 25, 4, 744, 744, 30 Oct. 2008
English

Observation of Wire Ignition Phenomena Induced by Short-term Excess Electric Current Application in Microgravity
FUJITA Osamu, KYONO Takeshi, KIDO Yasuhiro, NAKAMURA Yuji, ITO Hiroyuki
JASMA : Journal of the Japan Society of Microgravity Application, 25, 4, 743, 743, 30 Oct. 2008
English

Visualization of Combustion of Polymer-coated Electric Wire in Low Pressure Enclosure
NAKAMURA Yuji, AZUMAYA Keisuke, ITO Hiroyuki, FUJITA Osamu
可視化情報学会誌. Suppl. = Journal of the Visualization Society of Japan, 28, 2, 153, 154, 15 Sep. 2008
Japanese

Experimental study on thermophoretic deposition of soot particles in laminar diffusion flames along a solid wall in microgravity
Jae-Hyuk Choi, Osamu Fujita, Takafumi Tsuiki, Junhong Kim, Suk Ho Chung
EXPERIMENTAL THERMAL AND FLUID SCIENCE, 32, 8, 1484, 1491, ELSEVIER SCIENCE INC, Sep. 2008, [Peer-reviewed]
English, Scientific journal, Soot deposition process in diffusion flames along a solid wall has been investigated experimentally under a microgravity environment. An ethylene (C2H4) diffusion flame was formed around a cylindrical rodburner with the surrounding air velocities of V-a = 2.5, 5, and 10 cm/s, the oxygen concentration of 35%, and the burner wall temperature of 300 K. A laser extinction method was adopted to measure the distribution of soot volume fraction. The experiments determined the trace of maximum soot concentration together with the relative distance of the trace of flame. Results showed that the distance was about 2-5 mm. As the surrounding air velocity increased, the region of the soot particle distribution moved closer to the burner wall. The soot particles near the flame zone tended to move away from the flame zone because of the thermophoretic force and to concentrate at a certain narrow region inside the flame. Because of the simultaneous effects of convection and the thermophoresis, soot particles finally adhered to the burner wall. It has been found that there existed an optimal air velocity for the early deposition of soot on the furnace wall. (C) 2008 Elsevier Inc. All rights reserved.

Flame Spread over Polymer-Insulated Wire in Reduced Pressure Environments-Similarity to Microgravity Phenomena-
NAKAMURA Y.
Progress in Scale Modeling, 17, 28, Springer-Verlag, 2008

微小重力環境下における被覆導線の通電着火特性　　　　　　　　　　　　　　　
日本マイクログラビティ応用学会誌, Vol.1, No.1, 11, 16, 2008, [Peer-reviewed]

Improvement of Pyrolysis of Wastes in a Externally Heated Rotary Kiln : 2nd Report, Experimental Study on the Heat Transfer Enhancement
SUZUKI Tomoko, OKAZAKI Teruyuki, YAMAMOTO Kenji, NAKATA Hiroyuki, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers B, 74, 743, 1586, 1592, The Japan Society of Mechanical Engineers, 2008, [Peer-reviewed]
Japanese, The effects of rotating speed and internal structure on the performance of externally heated rotary kiln for the waste pyrolysis were in vestigated. For this purpose newly developed evaluation method of the overall heat transfer coefficient (k_) from the internal wall to the wastes was adopted. The experimental results showed that k_ monotonically increased with number of the lifter and the height of the lifter. As six lifters with 200mm height were attached to the inside wall of the kiln, the mean value of k_increased from 38.6 W/m^2 K to 45.3 W/m^2 K at 2.7rpm. In addition, k_ increased to 50.1 W/m^2 K as the rotating speed increased to 4.0rpm. In the water vaporization phase during the course of pylorysos process, the height of the lifter had a significant influence on the k_. On the other hand, the number of the lifter had a significant impact on the k_ in the plastic base wastes pyrolysis phase. According to the measurement the installation of lifters to attain the ratio of the height of lifter (H_l) to the thickness of the waste bed (H_w) larger than 0.45 or the arc length between the two lifters (L_l) to the arc length of the interface between the bed material and the kiln wall (L_w) larger than 1 gives 10% increase of k_.

Improvement of Pyrolysis of Wastes in an Externally Heated Rotary Kiln : 1st Report, Measurement of the Overall Heat Transfer Coefficient form the Wall to the Wastes
SUZUKI Tomoko, OKAZAKI Teruyuki, YAMAMOTO Kenji, NAKATA Hiroyuki, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers B, 74, 743, 1579, 1585, The Japan Society of Mechanical Engineers, 2008, [Peer-reviewed]
Japanese, For pyrolysis reactor of solid wastes, the externally heated rotary kiln is the most appropriate furnace. The goal of this study is to improve the heat transfer in the externally heated rotary kiln for the waste pyrolysis. As an important property of heat transfer, we performed experimental evaluation of the overall heat transfer coefficient (k_). The simulant waste was pyrolyzed using externally heated batch type rotary kiln pyrolyzer. In order to measure the radial heat flux through the dram wall, six pairs of thermo-couple were attached to the inside and outside surface of the drum wall. Heat flux (q_m) was calculated using the radial temperature gradient in the wall. k_ was calculated using the formula, k_=q_m/AdT; A is internal surface area of the wall, dT is temperature difference between inside surface of the wall and the waste. q_m and dT showed the highest value at the beginning of the pyrolysis. On the other hand, k_ showed the lowest value at the beginning and increased with increase in waste temperature. In the case of the mean temperature of the kiln inner wall was 555 centigrade, k_ changed from 22 W/m^2 K to 55 W/m^2 K. Consequently, in the continuous type kiln, at the closer distance to the end of the drum, the higher k_ appears.

DME 噴霧燃焼における輝炎化手法の開発
日本燃焼学会誌, 50, 153, 264, 270, 2008, [Peer-reviewed]

微小重力下での被覆導線燃え広がり現象に与える火炎輻射の影響
日本燃焼学会誌, 50, 153, 255, 263, 2008, [Peer-reviewed]

Effect of gravity and beam diameter on flame oscillation phenomena induced by external laser absorption
Masakazu Tsuchimoto, Teruaki Honko, Yuji Nakamura, Hiroyuki Ito, Osamu Fujita
COMBUSTION SCIENCE AND TECHNOLOGY, 180, 10-11, 1803, 1811, TAYLOR & FRANCIS INC, 2008, [Peer-reviewed]
English, Scientific journal, The effect of gravity and beam diameter on flame oscillation phenomena induced by external laser irradiation was investigated. Ethylene premixed gas was charged in a 50mm diameter combustion tube at 0.1MPa and a CO(2) laser beam was irradiated along the center axis of the tube. The microgravity maintained during the experiment assures that presently observed oscillation phenomena are not caused by gravity. Experiments with different laser beam diameters indicate that the flame front curvature affects the oscillatory propagation behavior. The results suggest that this phenomenon is caused by a transformation of the flame front curvature by a locally increased flame speed observed with the laser absorption, which is closely related to the thermal-diffusive instability in combination with a flame stretch effect.

Improvements in Pyrolysis of Wastes in an Externally Heated Rotary Kiln (Experimental Study on Heat Transfer Enhancement)
Tomoko Suzuki, Teruyuki Okazaki, Kenji Yamamoto, Hiroyuki Nakata, Osamu Fujita
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, 3, 3, 532, 539, JAPAN SOC MECHANICAL ENGINEERS, 2008, [Peer-reviewed]
English, Scientific journal, The effects of rotating speed and internal structure on the performance of an externally heated rotary kiln for waste pyrolysis were investigated. A newly developed method was adopted to evaluate the overall heat transfer coefficient k(m-w) from the inner wall to the wastes for this purpose. The experimental results revealed that k(m-w) monotonically increased with the number of lifters and their height. When six lifters 200 mm in height were attached to the inner wall of the kiln, the mean value of k(m-w) increased from 38.6 W/m(2)K to 45.3 W/m(2)K at 2.7 rpm. In addition, k(m-w) increased to 50.1 W/m(2)K when the rotating speed was increased to 4.0 rpm. In the water vaporization phase during the course of the pyrolysis process, the height of the lifters had a significant influence on k(m-w). However, the number of lifters had a significant impact on k(m-w) in the pyrolysis phase of the plastic-based wastes. According to measurements, a 10% increase in k(m-w) could be obtained when installing lifters to attain a ratio of lifter height H-l to the thickness of the waste layer H-w larger than 0.45 or when arc length between two lifters L-l to the arc length of the interface between the wastes and the kiln wall L-w was larger than 1.

DME拡散火炎とメタン部分予混合火炎のすす生成特性の比較
小林 雅律, 今井 亮介, 藤田 修
機械学会論文集B, 74, 748, 2718, 2723, 2008, [Peer-reviewed]

Opposed-wind Effect on Flame Spread of Electric Wire in Sub-atmospheric Pressure
Yuji Nakamura, Nobuko Yoshimura, Tomohiro Matsumura, Hiroyuki Ito, Osamu Fujita
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, 3, 3, 430, 441, JAPAN SOC MECHANICAL ENGINEERS, 2008, [Peer-reviewed]
English, Scientific journal, Opposed flame spread of electric wire in sub-atmospheric pressure is studied experimentally. Thin-polyethylene (PE) coated nickel-chrome (NiCr) and iron (Fe) wire are used as test samples in this study. Total pressure is reduced from atmospheric (100 kPa) to sub-atmospheric (40 kPa) and range of employed external forced-flow speed is from 0 cm/s to 40 cm/s. Results show that the spread rate monotonically decreases, or stays nearly constant, as the forced-flow speed increases regardless of the material of the wire. Dependence of the spread rate on the opposed-flow speed appears differently depending on the material of the wire; with high-conductive material (Fe), decrement trend of the spread rate with wind is suppressed. Importantly, under the conditions considered in this study, the spread rate tends to increase as the pressure decreases regardless of the pressure and the material of the wire. Dependence of the spread rate on pressure is more pronounced with less-conductive (NiCr) wire, whereas less-pronounced with high-conductive (Fe) wire. Qualitative discussions are made to explain the observed spread trend and the importance of the presence of wire to characterize the flame spread of the wire is addressed.

Improvements in Pyrolysis of Wastes in an Externally Heated Rotary Kiln (Measurements of the Overall Heat Transfer Coefficient from the Wall to Wastes)
Tomoko Suzuki, Teruyuki Okazaki, Kenji Yamamoto, Hiroyuki Nakata, Osamu Fujita
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, 3, 3, 523, 531, JAPAN SOC MECHANICAL ENGINEERS, 2008, [Peer-reviewed]
English, Scientific journal, Externally heated rotary kilns are the most appropriate furnaces to dispose of solid wastes using pyrolysis reactions. The goal of this study was to improve heat transfer in externally heated rotary kilns for waste pyrolysis. We experimentally evaluated the overall heat transfer coefficient k(m-w) as it is an important property of heat transfer. The model wastes were pyrolyzed using an externally heated batch-type rotary-kiln pyrolyzer. Six pairs of thermocouples were attached to the inner and outer surfaces of the drum wall to measure the radial heat flux through it. The heat flux q(m) was calculated using the radial temperature gradient in the wall. k(m-w) was calculated using the formula, k(m-w)=q(m)/AdT, where A is the internal surface area of the wall, and dT is the difference in temperature between the inner surface of the wall and the wastes. q(m) and dT had the highest values when pyrolysis began. However, k(m-w) had the lowest value when pyrolysis began and rose with an increase in waste temperature. When the mean temperature of the kiln's inner wall was 555 degrees C, k(m-w) rose from 22 W/m(2)K to 55 W/m(2)K. Consequently, a higher k(m-w) appeared closer to the end of the drum in a continuous-type kiln.

Flow and Thermal Structure during Flame Spread Event over Polymer-Insulated Wire in Sub-atmospheric Enclosure
NAKAMURA Yuji, YOSHIMURA Nobuko, ITO Hiroyuki, FUJITA Osamu, AZUMAYA Keisuke
Transactions of Visualization Society of Japan, 27, 2, 171, 172, The Visualization Society of Japan, 15 Sep. 2007
Japanese

DME火炎におけるすす生成特性
小林 雅律, 佐川 瞬大, 藤田 修
日本機械学会論文集B編, 73, 727, 680, 686, 2007, [Peer-reviewed]

The Flame Oscillation Phenomena Induced by External Radiation
TSUCHIMOTO Masakazu, KYOZU Akihiro, FUJITA Osamu, ITO Hiroyuki, NAKAMURA Yuji
Transactions of the Japan Society of Mechanical Engineers B, 73, 727, 803, 808, The Japan Society of Mechanical Engineers, 2007, [Peer-reviewed]
Japanese, Effect of external radiation on flame propagation phenomena of ethylene premixed gas was investigated. The mixture is charged in the combustion tube of 50 mm in diameter at 0.1 MPa and C0_2 laser was used as an external radiation source. We found that flame oscillation phenomena occurred in some conditions. The results showed that when C0_2 laser power was stronger than a given value and the Full-Width-Half-Maximum (FWHM) of C02 laser was 5 mm, flame oscillation occurred clearly. The flame oscillation pattern was influenced by the component of gas mixture and gravitational condition. It was suggested that this phenomena is caused by the transformation of flame front curvature by locally increased flame speed which closely relates with thermal-diffusive flame instability in combination with flame stretch effect.

Effect of Co-Axial Flow Velocity on Soot Formation in a Laminar Jet Diffusion Flame under Microgravity
Byoung-Ho Jeon, Osamu Fujita, Yuji Nakamura, Hiroyuki Ito
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, 2, 2, 281, 290, JAPAN SOC MECHANICAL ENGINEERS, 2007, [Peer-reviewed]
English, Scientific journal, To examine the effect of low co-axial flow on soot formation in a laminar jet diffusion flame, microgravity experiments have been conducted. The tested co-axial flow velocity range is 0-7.3cm/s, which is very difficult to provide on the ground because of suffering from the additional external flow induced by buoyancy force. The result showed that the soot formation characteristics were greatly affected by co-axial flow velocity at the low flow velocity range, that is, soot concentration increased with increase in the external flow velocity. According to the radial distributions, the effect of external flow velocity on the soot formation was prominent near the outer edge of visible flame. A comparison with numerical calculation suggested that the increase of soot concentration was caused by increased flame temperature in the area of low oxygen and fuel excess region.

DC Biasing Effects on Carbon Nanotube Formation in Microgravity Diffusion Flame　　　　　　　　　　　　　　　
Journal of the Japan Society of Microgravity Applications, Vol.24, No.3, 220, 224, 2007, [Peer-reviewed]

Reduced Gravity Devices Based on theYOYO priciple　　　　　　　　　　　　　　　
Journal of the Japan Society of Microgravity Applications, Vol.24, No.3, 312, 315, 2007, [Peer-reviewed]

Flame spread along PE-insulated wire in sub-atmospheric pressure enclosure
Yuji Nakamura, Nobuko Yoshimura, Tomohiro Matsumura, Hiroyuki Ito, Osamu Fujita
PROCEEDINGS OF THE ASME/JSME THERMAL ENGINEERING SUMMER HEAT TRANSFER CONFERENCE 2007, VOL 1, 591, 596, AMER SOC MECHANICAL ENGINEERS, 2007, [Peer-reviewed]
English, International conference proceedings, Flame spread over polymer-insulated wire in reduced (sub-atmospheric) pressure has been studied experimentally in order to evaluate the fire safety of electric circuit in the aircraft as well as the space habitats. Polyethylene (PE) insulated NiCr wire is used as the burning sample. Ambient gas is the mixture of nitrogen and oxygen, and the composition is fixed as air (79 vol.% of N-2 and 21 vol% of O-2) throughout the study. Total pressure is reduced from atmospheric (101 kPa) to sub-atmospheric (20 kPa) in order to investigate the role of the reduced pressure on the flame spread along the wire. Spread event followed by the forced ignition is recorded by digital video camera to obtain any time-dependent flame behavior. Experimental results show that the flame shape is changed from typical "teardrop" to "round" (and even oval) with the decrease in total pressure. Flame spread rate increases in the reduced pressure although the partial pressure of oxygen is "reduced" with the total pressure. Such "pronounced" spread behavior is continuously observed until just before the extinction condition (similar to 25 kPa in the present study). The change in flame shape could enhance thermal input to the unburned PE through gas-phase conduction as well as conduction along the wire, and these should be responsible for the faster flame spread in sub-atmospheric pressure. Heat balance is roughly estimated with measured temperature and relative contribution of above two thermal input pathways is understood almost comparable. Importance of the presence of conductive material, such as metal wire, on flame spread is addressed in the current spread behavior.

Research on Wire Ignition with Excess Electric Current by Utilizing 50m Drop Tower
FUJITA Osamu, EJARQUE Joan Pablo, FUJII Takashi, NAKAMURA Yuji, ITO hiroyuki
JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 23, 4, 342, 342, 30 Nov. 2006
English

Effect of gravity conditions on soot formation characteristics in C2H4 diffusion flame
JEON Byoungho, FUJITA Osamu, ITOU hiroyuki
JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 23, 4, 341, 341, 30 Nov. 2006
English

Numerical simulation and flight experiment on oscillating lifted flames in coflow jets with gravity level variation
J Kim, KN Kim, SH Won, O Fujita, J Takahashi, SH Chung
COMBUSTION AND FLAME, 145, 1-2, 181, 193, ELSEVIER SCIENCE INC, Apr. 2006, [Peer-reviewed]
English, Scientific journal, Charactetistics of oscillating lifted flames have been investigated numerically and experimentally by varying the gravity level in coflow jets with propane fuel highly diluted with nitrogen. The results showed that the oscillation amplitude and frequency increased with gravity level. As the gravity level decreased, the oscillation ceased and stationary lifted flames were stabilized when the gravity level became smaller than a critical value. A flame blowout occurred at high gravity levels. The reason for this limited range of oscillation has been analyzed by considering the local characteristics of the propagation speed of tribrachial (triple) flame and axial velocity at the edges of lifted flames. Considerations of the maximum and minimum values of these two components with gravity level during the flame edge oscillation could successfully explain the lower bounds of oscillation accounting for the influences of buoyancy and flame curvature. The blowout at high gravity levels can be explained by the effect of buoyancies on burnt gas and on propane fuel in such a way that the stoichiometric contour near the flame zone became detached from the contour near the nozzle. Finally, the experiments by varying gravity level through the parabolic flights of an aircraft substantiated the overall behavior of the oscillating lifted flames. (c) 2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

In-situ observation of the soot deposition process on a solid wall with a diffusion flame along the wall
JH Choi, O Fujita, T Tsuiki, JH Kim, SH Chung
JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 49, 1, 167, 175, JAPAN SOC MECHANICAL ENGINEERS, Feb. 2006, [Peer-reviewed]
English, Scientific journal, Experiments at the Japan Microgravity Center (JAMIC) have investigated the interaction between diffusion flames and solid surfaces placed near flames. The fuel for the flames was C2H4 and the surrounding oxygen concentration 35%, with surrounding air temperatures of T-a = 300 and 600 K. The effects of these parameters on soot distribution in diffusion flames and soot deposition on solid walls were studied. Direct images of the whole flame and shadow images of the flame with back light were recorded and used to calculate the soot volume fraction by the Abel transformation method. Results show that at the higher surrounding air temperature the soot particle distribution region is closer to the wall and results in more deposition. Numerical simulation was also performed to determine the motion of soot particles in the flames and the soot deposition characteristics. The results are in good agreement with the observed soot behavior in microgravity.

An overview of challenges in modeling heat and mass transfer for living on Mars
Masamichi Yamashita, Yoji Ishikawa, Yoshiaki Kitaya, Eiji Goto, Mayumi Arai, Hirofumi Hashimoto, Kaori Tomita-Yokotani, Masayuki Hirafuji, Katsunori Omori, Atsushi Shiraishi, Akira Tani, Kyoichiro Toki, Hiroki Yokota, Osamu Fujita
INTERDISCIPLINARY TRANSPORT PHENOMENA IN THE SPACE SCIENCES, 1077, 232, 243, BLACKWELL PUBLISHING, 2006, [Peer-reviewed]
English, Scientific journal, Engineering a life-support system for living on Mars requires the modeling of heat and mass transfer. This report describes the analysis of heat and mass transfer phenomena in a greenhouse dome, which is being designed as a pressurized life-support system for agricultural production on Mars. In this Martian greenhouse, solar energy will be converted into chemical energy in plant biomass. Agricultural products will be harvested for food and plant cultivation, and waste materials will be processed in a composting microbial ecosystem. Transpired water from plants will be condensed and recycled. In our thermal design and analysis for the Martian greenhouse, we addressed the question of whether temperature and pressure would be maintained in the appropriate range for humans as well as plants. Energy flow and material circulation should be controlled to provide an artificial ecological system on Mars. In our analysis, we assumed that the greenhouse would be maintained at a subatmospheric pressure under 1/3-G gravitational force with 1/2 solar light intensity on Earth. Convection of atmospheric gases will be induced inside the greenhouse, primarily by heating from sunlight. Microclimate (thermal and gas species structure) could be generated locally around plant bodies, which would affect gas transport. Potential effects of those environmental factors are discussed on the phenomena including plant growth and plant physiology and focusing on transport processes. Fire safety is a crucial issue and we evaluate its impact on the total gas pressure in the greenhouse dome.

A study of the effect of oxygen concentration on the soot deposition process in a diffusion flame along a solid wall by in-situ observations in microgravity
JH Choi, O Fujita, T Tsuiki, J Kim, SH Chung
JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 48, 4, 839, 848, JAPAN SOC MECHANICAL ENGINEERS, Nov. 2005, [Peer-reviewed]
English, Scientific journal, The effect of oxygen concentration on the soot deposition process from a diffusion flame to a solid wall was investigated in a microgravity environment to attain in-situ observations of the process. An ethylene (C2H4) diffusion flame was formed around a cylindrical rod burner in oxygen concentrations Of O-2 = 21, 35, and 50% with a surrounding air and wall temperatures of 300 K. Laser extinction was adopted to determine the soot volume fraction distribution between the flame and burner wall. The experimental results show that the soot particle distribution region moves closer to the surface of the wall and that more deposition occurs with increasing surrounding oxygen concentrations. The experiments determined the trace of the maximum soot concentration position, defined as the "soot line", and it was comparable to that established with numerical calculations. A numerical simulation was also performed to understand the motion of soot particles in the flame and the characteristics of the soot deposition to the wall. The results successfully predicted, the differences in the motion of soot particles by different oxygen concentrations near the burner surface and are in good agreement with observed soot behavior, ie the "soot line", in microgravity. A comparison of the calculations and experimental results led to the conclusion that a consideration of the thermophoretic effect is essential to understand the soot deposition on walls.

Two-sided ignition of a thin PMMA sheet in microgravity
Y Nakamura, T Kashiwagi, SL Olson, K Nishizawa, O Fujita, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 30, 2319, 2325, COMBUSTION INST, 2005, [Peer-reviewed]
English, Scientific journal, Numerical computations and a series of experiments were conducted in microgravity to study the ignition characteristics of a thin polymethylmethacrylate (PMMA) sheet (thicknesses of 0.2 and 0.4 mm) using a CO, laser as an external radiant source. Two separate ignition events were observed, including ignition over the irradiated surface (frontside ignition), and ignition, after some delay, over the backside surface (backside ignition). The backside ignition was achieved in two different modes. In the first mode, after the laser was turned off, the flame shrank and stabilized closer to the fuel surface. This allowed the flame to travel from the frontside to the backside through the small, open hole generated by the laser's vaporization of PMMA. In the second mode, backside ignition was achieved during the laser irradiation. The numerical calculation simulating this second process predicts fresh oxygen supply flows from the backside gas phase to the frontside gas phase through the open hole, which mixes with accumulated hot NIMA fuel vapor which is ignited as a second flame in the frontside gas phase above the hole. Then, the flame initiated from the second ignition travels through the hole to ignite the accumulated flammable mixture in the backside gas phase near the hole, attaining backside ignition. The first backside ignition mode was observed in 21% oxygen and the second backside ignition mode in 35%. The duration of the laser irradiation appears to have important effects on the onset of backside ignition. For example, in 21% oxygen, the backside ignition was attained after a 3 s laser duration but was not observed after a 6 s laser duration (within the available test time of 10 s). Longer laser duration might prevent two-sided ignition in low oxygen concentrations. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The effect of irradiation angle on laser ignition of cellulose sheet in microgravity
J Takahashi, O Fujita, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 30, 2311, 2317, COMBUSTION INST, 2005, [Peer-reviewed]
English, Scientific journal, The objective of this work was to investigate the effect of external radiation angle on radiative ignition of solid materials. A laser ignition experiment was performed in microgravity to investigate events occurring in the ignition process in a quiescent atmosphere. Filter paper was used as the test material, and it was heated by infrared radiation (CO2 laser 10.6 mu m) or near-infrared radiation (diode laser, 800.1 nm). The ignition time was determined for various irradiation angles, and the gas phase density change before ignition was observed by a Mach-Zehnder interferometer for each test condition. The results showed that the ignition by CO2 laser occurred on the laser beam line depending on the irradiation angle, while diode laser caused a similar ignition position independent of the irradiation angle. The period from gasification to ignition with CO2 laser was almost the same for different irradiation angles, while it varied with the irradiation angle for diode laser, and the ignition time was much shorter than that with diode laser. According to these results, it is considered that solid ignition with inclined external radiation is characterized based on (1) solid surface heating and (2) gas phase heating, and the second factor, gas phase heating, causes the different dependence of solid ignition on irradiation angle with different radiation wavelengths: (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

A study on the effect of wall temperature on soot deposition process from a diffusion flame in microgravity
Osamu Fujita, Jae-Hyuk Choi, Takafumi Tsuiki
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 71, 703, 970, 977, Japan Society of Mechanical Engineers, 2005, [Peer-reviewed]
Japanese, Scientific journal, The effect of wall temperature on soot deposition from a diffusion flame placed near the wall has been investigated by utilizing microgravity environment, which can attain very stable flame along the wall. Cylindrical burner with fuel injection was adopted to obtain two dimensional soot distributions by laser extinction method. In the experiment three different wall temperatures, Tw=300, 600, 800 K, were selected as test conditions. The results showed that the soot distribution between flame and burner wall was strongly affected by the wall temperature and soot deposition increases with decrease in wall temperature. According to the numerical calculation both convective motion and thermophoretic effect are important to explain the transfer of soot toward the burner wall. Then, "soot deposition length" defined as the relevant approach distance to the wall per a given axial distance is newly introduced as a better parameter to evaluate the soot deposition tendency to the wall. The comparison among the values for three different wall temperatures suggested that the change in thermophoretic effect is the most dominant factor to give the change in soot deposition characteristics.

Two-sided ignition of a thin PMMA sheet in microgravity
Y Nakamura, T Kashiwagi, SL Olson, K Nishizawa, O Fujita, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 30, 2319, 2325, COMBUSTION INST, 2005, [Peer-reviewed]
English, Scientific journal, Numerical computations and a series of experiments were conducted in microgravity to study the ignition characteristics of a thin polymethylmethacrylate (PMMA) sheet (thicknesses of 0.2 and 0.4 mm) using a CO, laser as an external radiant source. Two separate ignition events were observed, including ignition over the irradiated surface (frontside ignition), and ignition, after some delay, over the backside surface (backside ignition). The backside ignition was achieved in two different modes. In the first mode, after the laser was turned off, the flame shrank and stabilized closer to the fuel surface. This allowed the flame to travel from the frontside to the backside through the small, open hole generated by the laser's vaporization of PMMA. In the second mode, backside ignition was achieved during the laser irradiation. The numerical calculation simulating this second process predicts fresh oxygen supply flows from the backside gas phase to the frontside gas phase through the open hole, which mixes with accumulated hot NIMA fuel vapor which is ignited as a second flame in the frontside gas phase above the hole. Then, the flame initiated from the second ignition travels through the hole to ignite the accumulated flammable mixture in the backside gas phase near the hole, attaining backside ignition. The first backside ignition mode was observed in 21% oxygen and the second backside ignition mode in 35%. The duration of the laser irradiation appears to have important effects on the onset of backside ignition. For example, in 21% oxygen, the backside ignition was attained after a 3 s laser duration but was not observed after a 6 s laser duration (within the available test time of 10 s). Longer laser duration might prevent two-sided ignition in low oxygen concentrations. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The Mechanical Properties of PEEK Sheet after Atomic Oxygen Irradiation
NAKAMURA Hiroshi, NAKAMURA Takashi, NOGUCHI Toru, FUJITA Osamu, IMAGAWA Kichiro, INOUE Toshihiko
Transactions of the Japan Society of Mechanical Engineers Series B, 71, 710, 1327, 1332, The Japan Society of Mechanical Engineers, 2005, [Peer-reviewed]
Japanese, We irradiated 5 eV Atomic Oxygen (AO) to PEEK sheets with 0.4 mm thickness under tensile load, and estimated strength of the specimen. Three phenomena caused by exposure were observed : (1) appearance of numerous conical pits a few I-μm deep on the specimen surface; (2) reduction of thickness at the irradiated area; (3) change of chemical structure on the surface, which is probably caused by UV generated slightly during the AO irradiation test. As a result of tensile tests, tensile properties after AO irradiation were almost same as those of pristine samples regardless of applied stress. The depth of conical pits was so small and the thickness of layer changed after AO irradiation test was so thin that they did not affect mechanical properties of PEEK sheets. Consequently, residual strength of this material after AO exposure can be estimated by consideration of thickness decrease.

Microgravity combustion research by utilizing the new 50M drop tower　　　　　　　　　　　　　　　
Osamu Fujita, Hiroyuki Ito, Yuji Nakamura, Tsutomu Uematsu, Kenichi Ito
International Astronautical Federation - 56th International Astronautical Congress 2005, 1, 551, 555, 2005
English, International conference proceedings, Construction of new 50M drop tower to give 3 seconds Microgravity time is now going on in Hokkaido, Japan. The facility provides microgravity quality of 10-3 × G0 (G0 is a gravity level on the earth) or better and inner capsule of Φ 500 × 800 mm for payloads. Since combustion phenomena are strongly affected by presence of gravity and their time scale is generally short, many research subjects in combustion science are expected to proceed extensively with aid of the facility even it provides only 3s microgravity time. In the paper, the detail description of the facility and status of the construction is introduced. Further, the effective way to utilize the facility for combustion research will be discussed by introducing the examples of research attained previously by the authors.

3425 Strength properties of PEEK sheet exposed in the Low Earth Orbit
NAKAMURA Takashi, NAKAMURA Hiroshi, FUJITA Osamu, IMAGAWA Kichiro, INOUE Toshihiko
The proceedings of the JSME annual meeting, 2005, 451, 452, The Japan Society of Mechanical Engineers, 2005
Japanese, PEEK (Poly-ether-ether-keton) sheets with 0.4mm thickness were exposed to the real space environment for 315 days by using the International Space Station (ISS). Surface observations, mass measurements, and monotonic tensile tests were carried out to investigate the degradation after space exposure. As a result, the sample showed: (a) color change into dark brown, (b) thickness reduction, and (c) decrease of elongation at break. By comparison with results obtained by the ground control tests which irradiated atomic oxygen (AO), ultraviolet ray (UV), and electron beam (EB) to the same kind of PEEK samples, it was clarified that (a) and (c) were caused by UV in the ISS orbit, and that (b) was by AO.

The effect of irradiation angle on laser ignition of cellulose sheet in microgravity
Junya Takahashi, Osamu Fujita, Kenichi Ito
Proceedings of the Combustion Institute, 30, 2311, 2317, Elsevier Ltd, 2005, [Peer-reviewed]
English, Scientific journal, The objective of this work was to investigate the effect of external radiation angle on radiative ignition of solid materials. A laser ignition experiment was performed in microgravity to investigate events occurring in the ignition process in a quiescent atmosphere. Filter paper was used as the test material, and it was heated by infrared radiation (CO2 laser 10.6 μm) or near-infrared radiation (diode laser, 800.1 nm). The ignition time was determined for various irradiation angles, and the gas phase density change before ignition was observed by a Mach-Zehnder interferometer for each test condition. The results showed that the ignition by CO2 laser occurred on the laser beam line depending on the irradiation angle, while diode laser caused a similar ignition position independent of the irradiation angle. The period from gasification to ignition with CO2 laser was almost the same for different irradiation angles, while it varied with the irradiation angle for diode laser, and the ignition time was much shorter than that with diode laser. According to these results, it is considered that solid ignition with inclined external radiation is characterized based on (1) solid surface heating and (2) gas phase heating, and the second factor, gas phase heating, causes the different dependence of solid ignition on irradiation angle with different radiation wavelengths. © 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Two-sided ignition of a thin PMMA sheet in microgravity
Y. Nakamura, T. Kashiwagi, S. L. Olson, K. Nishizawa, O. Fujita, K. Ito
Proceedings of the Combustion Institute, 30, 2319, 2325, Elsevier Ltd, 2005, [Peer-reviewed]
English, Scientific journal, Numerical computations and a series of experiments were conducted in microgravity to study the ignition characteristics of a thin polymethylmethacrylate (PMMA) sheet (thicknesses of 0.2 and 0.4 mm) using a CO2 laser as an external radiant source. Two separate ignition events were observed, including ignition over the irradiated surface (frontside ignition), and ignition, after some delay, over the backside surface (backside ignition). The backside ignition was achieved in two different modes. In the first mode, after the laser was turned off, the flame shrank and stabilized closer to the fuel surface. This allowed the flame to travel from the frontside to the backside through the small, open hole generated by the laser's vaporization of PMMA. In the second mode, backside ignition was achieved during the laser irradiation. The numerical calculation simulating this second process predicts fresh oxygen supply flows from the backside gas phase to the frontside gas phase through the open hole, which mixes with accumulated hot MMA fuel vapor which is ignited as a second flame in the frontside gas phase above the hole. Then, the flame initiated from the second ignition travels through the hole to ignite the accumulated flammable mixture in the backside gas phase near the hole, attaining backside ignition. The first backside ignition mode was observed in 21% oxygen and the second backside ignition mode in 35%. The duration of the laser irradiation appears to have important effects on the onset of backside ignition. For example, in 21% oxygen, the backside ignition was attained after a 3 s laser duration but was not observed after a 6 s laser duration (within the available test time of 10 s). Longer laser duration might prevent two-sided ignition in low oxygen concentrations. © 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Construction of new drop tower and its role to proceed combustion researches
FUJITA Osamu, ITO Hiroyuki, ITO Kenichi
JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 21, 0, 63, 63, 04 Nov. 2004
English

The space exposure experiment of PEEK sheets under tensile stress
Takashi Nakamura, Hiroshi Nakamura, Osamu Fujita, Toru Noguchi, Kichiro Imagawa
JSME International Journal, Series A: Solid Mechanics and Material Engineering, 47, 3, 365, 370, Jul. 2004, [Peer-reviewed]
English, Scientific journal, To find out the degradation behavior of polymer in the real space, space exposure experiments utilizing the International Space Station (ISS) were scheduled. PEEK sheets under tensile stresses were exposed to the environment around the ISS orbit, and were irradiated by atomic oxygen (AO), ultraviolet ray, and electron beam (EB) in the ground test facility. This study introduces the outline of these experiments, and shows the results of AO and EB pilot irradiation tests as follows: (1) Test piece surfaces after AO exposure exhibited significant morphological damages characterized by micron-sized conical pits. (2) Thickness reductions of the test pieces by AO exposure increased with increasing tensile stress. (3) Residual strength after AO exposure could be estimated by taking account of thickness reduction. (4) No significant change was observed on surface morph, mass, chemical structure, and tensile properties of the test pieces after EB exposure regardless of tensile stress.

The space exposure experiment of PEEK sheets under tensile stress
T Nakamura, H Nakamura, O Fujita, T Noguchi, K Imagawa
JSME INTERNATIONAL JOURNAL SERIES A-SOLID MECHANICS AND MATERIAL ENGINEERING, 47, 3, 365, 370, JAPAN SOC MECHANICAL ENGINEERS, Jul. 2004, [Peer-reviewed]
English, Scientific journal, To find out the degradation behavior of polymer in the real space, space exposure experiments utilizing the International Space Station (ISS) were scheduled. PEEK sheets under tensile stresses were exposed to the environment around the ISS orbit, and were irradiated by atomic oxygen (AO), ultraviolet ray, and electron beam (EB) in the ground test facility., This study introduces the outline of these experiments, and shows the results of AO and EB pilot irradiation tests as follows: (1) Test piece surfaces after AO exposure exhibited significant morphological damages characterized by micron-sized conical pits. (2) Thickness reductions of the test pieces by AO exposure increased with increasing tensile stress. (3) Residual strength after AO exposure could be estimated by taking account of thickness reduction. (4) No significant change was observed on surface morph, mass, chemical structure, and tensile properties of the test pieces after EB exposure regardless of tensile stress.

Performance of NOx reduction catalysts with simulated dimethyl ether diesel engine exhaust gas
M Alam, O Fujita, K Ito
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY, 218, A2, 89, 95, PROFESSIONAL ENGINEERING PUBLISHING LTD, Mar. 2004, [Peer-reviewed]
English, Scientific journal, Characteristics of dimethyl ether oxidation and formaldehyde formation with NOX reduction catalysts were investigated in comparison with noble metal catalysts. The catalysts used in this research were Co and Sri as NOX catalysts and Pt, Pd, Rh as noble metal catalysts. Moreover, all the catalysts were loaded with gamma alumina (gamma-Al2O3). In addition, a pure gamma-Al2O3 catalyst was also used. Laboratory experiments were conducted by using the above catalysts in the presence of oxygen-rich simulated dimethyl ether engine exhaust gas. The catalyst temperature and the concentration of NO in the simulated exhaust gas were selected as experimental parameters. The experimental results showed that low-temperature dimethyl ether oxidation was possible with Pt, Pd and Rh catalysts, whereas higher-temperature dimethyl ether oxidation was observed with Co, Sri and pure gamma-Al2O3 catalysts. A large amount of formaldehyde was formed during the use of NOX reduction catalysts over a certain temperature range. However, the noble metal catalysts did not show any formation of formaldehyde. The effect of NO on dimethyl ether oxidation and formaldehyde formation with NOX reduction catalysts was significant. The dimethyl ether oxidation ratio became lower and the amount of formaldehyde formation increased with increase in NO in the simulated exhaust gas.

The effect of core material on combustion behaviour over polyethylene insulated wire under microgravity
Katsuhiro Nishizawa, Osamu Fujita, Kenichi Ito
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 694, 1555, 1562, Japan Society of Mechanical Engineers, 2004, [Peer-reviewed]
Japanese, Scientific journal, Combustion of wire insulation is important for fire safety in Space. Insulated wire has two unique features, one is sample geometry and another is existence of wire core. In this paper we investigate the effect of core materials on combustion phenomena of insulated wires. An experimental study of flame spread phenomena over polyethylene insulated wires with two different core materials, copper and nichrom, in different O2 concentrations was performed in microgravity. The experiments were performed at the Japan Microgravity Center (JAMIC) 10 s dropshaft. Experiments were performed with different O2 concentration and core material. The results show that the core material strongly affects the flame shape irrespective of gravity level. The flame spread rate is also strongly affected by the core material. Under normal gravity, the flame spread rate with copper cores is faster than that with nichrom cores in any of the tested oxygen concentrations. In microgravity, the effect of the core materials on the flame spread rate changes by oxygen concentration. In 35% O2, flame spread rate with copper wire was faster than that with nichrom core wire, as also seen in the normal gravity case. In 21% O2, the flame spread rate with the nichrom core wire is faster than that with copper core wire. The core heat conduction analysis shows that the thermal conductivity of the core material has an important effect on the flame spread rate. The case of high flame temperatures, the core acts as a heat source and high conductivity material supplies more heat to the insulation. At low temperatures, the core becomes heat sink and high conductivity material causes heat removal from the insulation near the flame front.

Damage properties of PEEK films irradiated by atomic oxygen
T Nakamura, H Nakamura, O Fujita, T Noguchi, K Imagawa, T Inoue
ADVANCES IN FRACTURE AND FAILURE PREVENTION, PTS 1 AND 2, 261-263, 1617, 1622, TRANS TECH PUBLICATIONS LTD, 2004, [Peer-reviewed]
English, Scientific journal, Atomic Oxygen (AO) is a main constituent of the atmosphere on low earth orbit where the International Space Station (ISS) goes around, and is also known as the matter which deteriorate many kinds of polymers. However, the strength properties of polymers suffered from AO have not been fully clarified. To investigate this problem, we irradiated AO to Poly-Ether-Ether-Keton (PEEK) films under three kinds of tensile stresses. Based on the analysis of irradiated samples, the effects of AO fluence (total amount of AO per unit area) and tensile stresses on damage properties were discussed with regard to reaction efficiency Re, surface morph, and tensile strength properties. As a result, the following were obtained: (1) Test piece surfaces exhibited considerable damage covered by conical pits of 1 mum sizes with a few mum depths. (2) Test piece thickness of irradiated area decreased almost proportionally to AO fluence. (3) Re and thickness reduction was accelerated by tensile stress. (4) Strength properties after AO irradiation were almost same as those of a pristine sample considering the decrease of specimen thickness.

Combustion behaviour over ETFE insulated wire in slow external flow under microgravity
Katsuhiro Nishizawa, Osamu Fujita, Kenichi Ito, Masao Kikuchi, Sandra L. Olson, Takashi Kashiwagi
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 692, 1043, 1050, Japan Society of Mechanical Engineers, 2004, [Peer-reviewed]
Japanese, Scientific journal, Opposed flame spreading over ETFE (ethylene-tetrafluoroethylene co-polymer) insulated wire, which is used for actual wire in space, in low air flow velocity has been investigated under microgravity environment. The experiments were performed with Japan Microgravity Center (JAMIC) 10 s dropshaft and NASA's KC 135 parabolic flight, Experiments were performed with changing O2 concentration, 35 and 40%, external air flow velocity, 0 (quiescent) -22 cm/s and dilution gas, N2, CO2, He. The sample of 0.32 mm inner core diameter with 0.15 mm insulation thickness was used. The results showed that flame spread rate over wire insulation was strongly affected by air flow velocity and the dilution gases. Flame spread with N2 dilution had maximum value in a low flow velocity region. However, CO2 dilution resulted in monotonic increase in flame spread rate with decrease in air flow velocity and the maximum flame spread at Ve=0 cm/s (quiescent). The different dependency of the spread rate on flow velocity with different dilution gas was explained by the reabsorption effect of CO2 gas ahead of flame front. Reabsorption of radiation heat with CO2 gas recovers the radiation heat from the flame and prevent the flame temperature decrease even in very low flow velocity region, which is known as radiation control region for optically thin gas.

Construction plan of ground based microgravity experiment system and diffusion flame synthesis of carbon nanotubes under microgravity　　　　　　　　　　　　　　　
Hiroyuki Ito, Osamu Fujita, Ryojiro Akiba, Kenichi Ito
International Astronautical Federation - 55th International Astronautical Congress 2004, 8, 4839, 4846, 2004
English, International conference proceedings

Changes of mechanical properties on PEEK sheet in LEO environment
NAKAMURA Hiroshi, NAKAMURA Takashi, NOGUCHI Toru, FUJITA Osamu, IMAGAWA Kichiro, INOUE Toshihiko
The proceedings of the JSME annual meeting, 2004, 445, 446, The Japan Society of Mechanical Engineers, 2004
Japanese, This paper describes the changes of mechanical properties on PEEK after electron beam (EB), atomic oxygen (AO) and ultraviolet ray (UV) exposure under tensile stress. Tensile tests showed that mechanical properties after EB exposure were almost same as those of pristine PEEK. Radiation resistance of PEEK was so high that EB radiation gave no effect on material properties. Although test peace surface was removed by AO attack, tensile strengths after AO exposure were almost same as those of pristine sample. It was clarified that residual strength of PEEK sheet after AO exposure can be estimated by consideration of thickness reduction. PEEK was embrittled by crosslinking resulting from UV radiation. Applied tensile stress during exposure inhibited the crosslinking reaction.

Experimental study on radiative ignition of filter paper with near infrared radiation under microgravity
O Fujita, J Takahashi, K Ito
JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 46, 4, 625, 632, JAPAN SOC MECHANICAL ENGINEERS, Nov. 2003, [Peer-reviewed]
English, Scientific journal, Experiments with radiative ignition were performed in microgravity to elucidate the events arising during the ignition process in a quiescent field. Filter paper was irradiated by Diode laser light (800.1 nm), which is little absorbed in the gas phase, at various oxygen concentrations (0 - 50%). The ignition delay was measured for various experimental conditions. The density changes of the gas phase before ignition was observed in detail by a Mach-Zehnder interferometer. The results showed that heat conduction from the sample surface induced a weak chemical reaction in the vicinity of the sample surface, and this propagated outward to achieve combustion. The ignition delay decreased with increases in O-2 concentration because the mixture near the sample surface contained more oxygen causing an immediate transition from the weak chemical reactions to the strong reactions of the combustion.

Propagation speed of tribrachial (triple) flame of propane in laminar jets under normal and micro gravity conditions
J Lee, SH Won, SH Jin, SH Chung, O Fujita, K Ito
COMBUSTION AND FLAME, 134, 4, 411, 420, ELSEVIER SCIENCE INC, Sep. 2003, [Peer-reviewed]
English, Scientific journal, The propagation speed of tribrachial (triple) flames in laminar propane jets has been investigated experimentally under normal and micro gravity conditions. We found in the present experiment that the displacement speed varied nonlinearly with axial distance because the flow velocity along the stoichiometric contour was comparable to the propagation speed of tribrachial flame. Approximate solutions for the velocity and concentration accounting density difference and virtual origins have been used in determining the propagation speed of tribrachial flame and the concentration field was validated from the measurement of Raman scattering. Under the microgravity condition, the results showed that the propagation speed of tribrachial flame decreased with the mixture fraction gradient, in agreement with previous studies. The limiting maximum propagation speed under the microgravity condition is in good agreement with the theoretical prediction, ie, the ratio of maximum propagation speed to the stoichiometric laminar burning velocity is proportional to the square root of the density ratio of unburned to burnt mixture. (C) 2003 The Combustion Institute. All rights reserved.

Normal and microgravity experiment of oscillating lifted flames in coflow
SH Won, J Kim, MK Shin, SH Chung, O Fujita, T Mori, JH Choi, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 29, 37, 44, COMBUSTION INST, 2003, [Peer-reviewed]
English, Scientific journal, Characteristics of oscillating lifted flames in coflow have been investigated experimentally with highly diluted propane in both normal gravities and microgravities to elucidate the oscillation mechanism. In normal gravity, oscillating lifted flames with the frequency of 2-5 Hz were observed in a certain range of fuel mole fraction and jet velocity for the jet Reynolds number smaller than 100. The oscillation frequency in terms of the Strouhal number, defined in terms of the stoichiometric laminar burning velocity, correlated well with jet velocity. This demonstrated the importance of the propagation characteristics of tribrachial flames at the base of lifted flames in the flame oscillation. Microgravity experiments have been conducted after the oscillating lifted flames were stabilized in normal gravity. During the change in gravitational acceleration, the flames rapidly stabilized as nozzle attached flames and became stationary. This behavior confirmed that the lifted flame oscillation in normal gravity is due to the buoyancy driven instability. Numerical simulation has also been performed accounting the change in gravitational acceleration. The results success fully predicted the transition behavior from oscillating lifted flame in normal gravity to stationary nozzle attached flame in microgravity and the variation of flame shapes during the transition.

Effect of wind velocity on flame spread in microgravity
K Prasad, Y Nakamura, SL Olson, O Fujita, K Nishizawa, K Ito, T Kashiwagi
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 29, 2553, 2560, COMBUSTION INST, 2003, [Peer-reviewed]
English, Scientific journal, A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier-Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10 s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, and three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges), followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, and convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism. Physical arguments based on the lateral diffusive flux of oxygen, fuel depletion, the oxygen shadow of the flame, and the heat release rate are constructed to explain the various observed flame shapes.

Effect of low external flow on flame spread over polyethylene-insulated wire in microgravity
O Fujita, K Nishizawa, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 29, 2545, 2552, COMBUSTION INST, 2003, [Peer-reviewed]
English, Scientific journal, An experimental study of flame spread phenomena over polyethylene-insulated wires has been performed in opposed flow under microgravity. The experiments were performed at the Japan Microgravity Center (JAMIC) 10 s drop shaft. Two samples with different insulation thicknesses, 0.075 and 0.15 mm, and with the same inner core diameter, 0.5 mm, were used. Experiments were performed with O-2 concentrations of 21%-50% and external flow velocities 0 (quiescent) to 30 cm/s. The results show that the rate of flame spread is affected by the flow velocity and that the effect is much stronger at high oxygen concentrations. According to the results, flame spread phenomena of wire insulation can be classified into four different regimes based on the flow velocity: (1) an oxygen transport control regime, (2) a geometrical effect regime, (3) a thermal regime, and (4) a chemical kinetic control regime. A special feature of the flame spread over wire insulation is the existence of the geometrical effect regime and a maximum spread rate between the oxygen transport control and geometrical effect regimes. The mechanism that gives rise to the unique features is discussed based on changes in preheat length, standoff distance, and flame temperature. The importance of the three effects and their relation to sample geometry, enhancement of diffusive oxygen supply, reduction of standoff distance, and logarithmic effect for the heat transfer are discussed.

Ignition phenomena of PMMA rod in highly preheated air flow
Osamu Fujita, Futoshi Matsunaga, Takashi Noro, Kenichi Ito
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 678, 490, 496, Japan Society of Mechanical Engineers, 2003, [Peer-reviewed]
Japanese, Scientific journal, Ignition process and burning characteristics of a polymethylmethacrylate (PMMA) rod in highly preheated convective environment are investigated experimentally. The main parameters are O2 concentration, flow velocity, preheated air temperature and oxygen dilution gas. The convective ignition can be classified into three steps: blue flame generation, attached flame formation and envelope flame development. Convective ignition of PMMA suddenly exposed to high temperature air is initiated in downstream and dim blue premixed flame is formed there. When the pyrolysis of solid fuel increases enough for flame propagation, the blue flame propagates to upstream to form an attached flame or luminous envelope flame. The ignition delay time is almost independent on oxygen concentration because the initial blue flame formation process is mainly controlled by pyrolysis rate. However, the following attached flame and envelope flame formation time increases with decrease in the oxygen concentration since these processes are chiefly dominated by burning velocity.

Effect of Light Wavelength on Radiative Ignition of Filter Paper in Microgravity
Junya Takahashi, Osamu Fujita, Kenichi Ito
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 683, 1685, 1691, Japan Society of Mechanical Engineers, 2003, [Peer-reviewed]
Japanese, Scientific journal, The objective of this work is to provide information about the details of the effect of light wavelength on radiative ignition of solid material. An experiment of radiative ignition has been performed in microgravity to determine the events occurring in ignition processes in a quiescent atmosphere. Filter papers were irradiated by infrared radiation (CO2 laser 10.6 μm) or near infrared radiation (Diode laser, 800.1 nm). The ignition delay was measured for various experimental conditions, and the density change of gas phase before ignition were observed by a Mach-Zehnder interferometer. The results showed that the ignition delay time of the infrared radiation was much shorter than that of near infrared radiation, and it was observed that the difference of light wavelength of radiations had a strong effect on the ignition process. It was suggested that one of main reasons to give the difference was the difference of radiative absorption in gas phase as well as the difference of absorptivity by solid surface according to the Mach-Zehnder interferometer.

Measurement of coal gasification rate by microgravity laser irradiation method
O Fujita, K Shimizu, J Takahashi, K Ito, S Kanbara
COMBUSTION SCIENCE AND TECHNOLOGY IN ASIA-PACIFIC AREA: TODAY AND TOMORROW, 277, 280, SOUTHEAST UNIV PRESS, 2003, [Peer-reviewed]
English, International conference proceedings, Determination of gasification rate of coal char with CO2 gas has been attempted by using microgravity laser irradiation method. When laser is irradiated to coal char, surface temperature increases depending on the heat flux supplied by the laser. Since the main coal gasification reaction, C + CO2 --> 2CO, is endothermic reaction, it causes temperature decrease. Therefore, the temperature difference between calculated value based on heat balance without reaction term and experimentally measured value could give the reaction rate. The results showed that the calculated temperature is almost identical to the measured one for the case with N2 atmosphere, inert gas for gasification reaction. With the case with CO2 the measured value is lower than that of calculation. According to the temperature discrepancy the reaction rate was given. The gasification reaction rate increases with increase in CO2 pressure and it tends to shift from reaction control to diffusion control judging from the change in estimated apparent activation energy.

Observation of soot agglomeration process with aid of thermophoretic force in a microgravity jet diffusion flame
O Fujita, K Ito
EXPERIMENTAL THERMAL AND FLUID SCIENCE, 26, 2-4, 305, 311, ELSEVIER SCIENCE INC, Jun. 2002, [Peer-reviewed]
English, Scientific journal, Soot agglomeration process in a jet diffusion flame was observed under microgravity condition. Laser shadow method was applied to measure the change of soot agglomerates diameter as well as laser attenuation ratio to give a volume fraction of soot in the flame. According to the experimental results, soot agglomerate size became much larger than that in normal gravity flame and its maximums size was more than 100 mum in the flame. Further, the size of the soot agglomerates increased with increase in the distance from the burner exit. To explain the large soot agglomerates formation, the importance of thermophoretic force as well as longer residence time in microgravity was pointed out based on the motion analysis of the individual soot agglomerates determined from the laser shadow method. That is, the soot particle near the flame zone tends to move away from the flame zone because of thermophoretic force and to concentrate at a certain narrow area inside of the flame. This phenomenon in combination with longer residence time in microgravity leads to high concentration of soot particle in a diffusion flame and caused the larger soot agglomerates formation. (C) 2002 Published by Elsevier Science Inc.

Experimental study on radiative ignition of filter paper with near infrared radiation under microgravity
Osamu Fujita, Junya Takahashi, Kenichi Ito
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 68, 666, 568, 575, Japan Society of Mechanical Engineers, 2002, [Peer-reviewed]
Japanese, Scientific journal, The objective of this work is to provide information about the details of the gas phase reaction on solids material ignition. An experiment of radiative ignition has been performed in microgravity to determine the events occurring in ignition processes in a quiescent field. Filter papers were irradiated by Diode laser (800.1 nm), which is little absorbed in gas phase, in various oxygen concentrations (0-50%). Using this laser makes it possible to observe the radiative ignition without the effect of gas phase absorption. The ignition delay was measured for various experimental conditions. The density change of gas phase before ignition were observed by a Mach-Zehnder interferometer. The results showed that heat conduction from the sample surface induced weak chemical reaction in the vicinity of the sample surface, which propagated outward to reach strong combustion. Ignition delay time decreased with increase in O2 concentration because mixture near the sample surface might contain more oxygen with higher oxygen atmosphere to cause immediate transition from the weak chemical reaction to the strong combustion.

Soot distribution in a diffusion flame along solid wall and its deposition to the wall in μG
TSUIKI Takafumi, FUJITA Osamu, ITO Kenichi
The proceedings of the JSME annual meeting, 2002, 15, 16, The Japan Society of Mechanical Engineers, 2002
Japanese, The interaction between diffusion flame and solid surface placed near the flame are studied experimentally. The main parameters are air temperature and wall temperature. The effects of these parameters on soot distribution in diffusion flame and soot deposition to the solid wall have been studied. Microgravity experiments at Japan Microgravity Center (JAMIC) has been carried out to attain very stable diffusion flame along solid surface.

Effect of wind velocity on flame spread in microgravity
Kuldeep Prasad, Yuji Nakamura, Sandra L. Olson, Osamu Fujita, Katsuhiro Nishizawa, Kenichi Ito, Takashi Kashiwagi
Proceedings of the Combustion Institute, 29, 2, 2553, 2560, Elsevier Ltd, 2002, [Peer-reviewed]
English, Scientific journal, A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier-Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10 s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, and three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges), followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, and convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism. Physical arguments based on the lateral diffusive flux of oxygen, fuel depletion, the oxygen shadow of the flame, and the heat release rate are constructed to explain the various observed flame shapes.

Microgravity Combustion Characteristics of Polystyrene Spheres with Various Ambient Gases　　　　　　　　　　　　　　　
B.C.Choi,K.Ito, O.Fujita
Transaction of Korean Society of Mechanical Engineers, 25, 11, 1509, 1517, Nov. 2001, [Peer-reviewed]
Scientific journal

Experimental observations of spot radiative ignition and subsequent three-dimensional flame spread over thin cellulose fuels
SL Olson, T Kashiwagi, O Fujita, M Kikuchi, K Ito
COMBUSTION AND FLAME, 125, 1-2, 852, 864, ELSEVIER SCIENCE INC, Apr. 2001, [Peer-reviewed]
English, Scientific journal, Non-piloted radiative ignition and transition to flame spread over thin cellulose fuel samples was studied aboard the USMP-3 STS-75 Space Shuttle mission, and in three test series in the 10 second Japan Microgravity Center (JAMIC). A focused beam from a tungsten/halogen lamp was used to ignite the center of the fuel sample while an external air flow was varied from 0 to 10 cm/s. Non-piloted radiative ignition of the paper was found to occur more easily in microgravity than in normal gravity. ignition of the sample was achieved under all conditions studied (shuttle cabin air, 21%-50% O-2 in JAMIC), with transition to flame spread occurring for all but the lowest oxygen and Bow conditions. Although radiative ignition in a quiescent atmosphere was achieved, the flame quickly extinguished in air. The ignition delay time was proportional to the gas-phase mixing time, which is estimated by using the inverse flow rate. The ignition delay was a much stranger function of Bow at lower oxygen concentrations. After ignition, the flame initially spread only upstream, in a fan-shaped pattern. The fan angle increased with increasing external flow and oxygen concentration from zero angle (tunneling flame spread) at the limiting 0.5 cm/s external air Bow, to 90 degrees (semicircular flame spread) for external Bows at and above 5 cm/s, and higher oxygen concentrations. The fan angle was shown to be directly related to the limiting air flow velocity. A surface energy balance reveals chat the heat feedback rate from the upstream flame to the surface decreases with decreasing oxygen mass transport via either imposed flow velocity or ambient oxygen concentration. Quenching extinction occurs when the heat feedback rate from the flame is no longer sufficient to offset the ongoing surface radiative heat losses. Despite the convective heating from the upstream flame. the downstream flame was inhibited due to the 'oxygen shadow' of the upstream flame for the air Bow conditions studied. Downstream flame spread rates in air, measured alter upstream flame spread was complete and extinguished, were slower than upstream flame spread rates at the same Bow. The quench regime for the transition to flame spread was skewed toward the downstream, because of the augmenting role of diffusion for opposed Bow flame spread, versus the canceling effect of diffusion at very low cocurrent flows. (C) 2001 by The Combustion Institute.

Combustion Behavior Over Polyethylene Coated Wire in Slow External Flow under Microgravity　　　　　　　　　　　　　　　
藤田 修, 西澤 勝弘, 伊藤 献一
Osamu FUJITA, Katsuhiro NISHIZAWA and Kenichi ITO, 18, 4, 276, 282, 2001, [Peer-reviewed]
Japanese, Scientific journal

Introduction of some microgravity combustion research in Japan relating solid and gaseous fuel
K Ito, O Fujita
FIRST INTERNATIONAL SYMPOSIUM ON MICROGRAVITY RESEARCH & APPLICATIONS IN PHYSICAL SCIENCES AND BIOTECHNOLOGY, VOLS I AND II, PROCEEDINGS, 454, 285, 292, EUROPEAN SPACE AGENCY, 2001, [Peer-reviewed]
English, International conference proceedings, General situation of microgravity research in Japan regarding to solid and gaseous fuel combustion is described. The ma or topics of solid combustion in the paper are ignition of solid material, flame propagation in dispersed particle cloud and flame spreading over solid material. The section of gaseous fuel combustion introduced the topics on premixed flames such as combustion velocity, extinction and flame ball. Diffusion flame including flame shape and flickering, and sooting phenomena are another the major topics for gaseous fuel combustion. The research on the effect of magnetic field effect and catalytic combustion in microgravity are also introduced. Through there results it was emphasized that the microgravity environment has a essential potential for fundamental understanding of combustion phenomena and provides a unique field to bring new findings which never observed on the ground.

Effective mechanisms to determine flame spread rate over ethylene-tetrafluoroethylzene wire insulation: Discussion on dilution gas effect based on temperature measurements
O Fujita, M Kikuchi, K Ito, K Nishizawa
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 28, 2905, 2911, COMBUSTION INST, 2000, [Peer-reviewed]
English, Scientific journal, Rates of flame spreading for ethylene-tetrafluoroethylene (ETFE) insulated wires in microgravity were compared with downward rates of flame spreading in normal gravity. Three distinctive features were noted: (1) The rate of spreading in microgravity was faster than the rate of downward spreading in normal gravity (V-f0G/V-f1G > 1) for almost all the tested conditions: (2) the increase in V-f0G/(f1G) was the largest with CO2 dilution: and (3) thr ratio of V-f0G/V-f1G with CO2 dilution increased with decreases in O-2 concentra- tion, while the value for other dilution gases showed a peak value at a specific O-2 concentration. The mechanism for these features is discussed with the detailed temperature distributions measured in microgravity) The preheat zone of microgravity flames was much thicker than with normal gravity. The decreases in Rattle temperatures by radiative heat losses in microgravity was smaller for wires because of a curvature effect. The thicker preheated zone and lower temperature decrease in microgravity caused the faster flame spreading in microgravity. The curvature effect is a basic difference from flat samples. Carbon dioxide reabsords the radiation heat, and the temperature of the preheated zone becomes higher than with the other dilution gases. The reabsorption effect caused the largest increase in rates of flame spreading in microgravity when compared with the situation under normal gravity. The reabsorption effect of CO2 has the potential to recover radiated heat while the other dilution gases lose this heat. This recovery effect apparently caused the increase in the V-f0G/V-f1G ratio at lower O-2 concentrations.

Experimental study on radiative ignition of a paper sheet in microgravity
O Fujita, J Takahashi, K Ito
PROCEEDINGS OF THE COMBUSTION INSTITUTE, 28, 2761, 2767, COMBUSTION INST, 2000, [Peer-reviewed]
English, Scientific journal, An experimental study of radiative ignition of sheet paper has been performed in microactivity to determine the events occurring in ignition processes in a quiescent field. Experiments were conducted on filter paper using a CO2 laser with a mean incident flux of about 5.8 W/cm(2) in various oxygen concentrations (0%-35%) and at various pressures (0.5-2 atm). The laser beam was irradiated perpendicular to the sample surface. The ignition delay was measured for various experimental conditions with high-speed video images or HI-R video images taken in microgravity. The gas-phase and solid-surface temperature changes were observed by a Mach-Zehnder interferometer and an infrared camera. The results showed that the ignition delay became shorter with increases in oxygen concentration, and it was observed that the gas-phase temperature increased more than that of the solid surface. Further, the increase in gas-phase temperature was larger with oxygen that without oxygen, though there were increases in the gas-phase temperature even without oxygen. The results showed that chemical processes, such as gas-phase reactions are essential in the ignition mechanism, as are physical processes, such as heating the solid material, and gas-phase laser absorption. The research clearly showed the importance of each process by utilizing a non-convective flow field where gravitational forces were not acting.

Effective mechanisms to determine flame spread rate over ethylene-tetrafluoroethylene wire insulation: Discussion on dilution gas effect based on temperature measurements
Osamu Fujita, Masao Kikuchi, Kenichi Ito, Katsuhiro Nishizawa
Proceedings of the Combustion Institute, 28, 2, 2905, 2911, Elsevier Ltd, 2000, [Peer-reviewed]
English, Scientific journal, Rates of flame spreading for ethylene-tetrafluoroethylene (ETFE) insulated wires in microgravity were compared with downward rates of flame spreading in normal gravity. Three distinctive features were noted: (1) The rate of spreading in microgravity was faster than the rate of downward spreading in normal gravity (Vf0G/Vf1G >
1) for almost all the tested conditions
(2) the increase in Vf0G/Vf1G was the largest with CO2 dilution
and (3) the ratio of Vf0G/Vf1G with CO2 dilution increased with decreases in O2 concentration, while the value for other dilution gases showed a peak value at a specific O2 concentration. The mechanism for these features is discussed with the detailed temperature distributions measured in microgravity. The preheat zone of microgravity flames was much thicker than with normal gravity. The decreases in flame temperatures by radiative heat losses in microgravity was smaller for wires because of a curvature effect. The thicker preheated zone and lower temperature decrease in microgravity caused the faster flame spreading in microgravity. The curvature effect is a basic difference from flat samples. Carbon dioxide reabsorbs the radiation heat, and the temperature of the preheated zone becomes higher than with the other dilution gases. The reabsorption effect caused the largest increase in rates of flame spreading in microgravity when compared with the situation under normal gravity. The reabsorption effect of CO2 has the potential to recover radiated heat while the other dilution gases lose this heat. This recovery effect apparently caused the increase in the Vf0G/Vf1G ratio at lower O2 concentrations.

Performance of NOx catalyst in a di diesel engine operated with neat dimethyl ether
M. Alam, O. Fujita, K. Ito, S. Kajitani, M. Oguma, H. MacHida
SAE Technical Papers, 1999-01, 3599, 1999, [Peer-reviewed]
English, International conference proceedings, An experiment was conducted with a direct injection Diesel engine operated with neat dimethyl ether (DME). Main focus of this research is to investigate the performance of the catalysts designed for NOx reduction, such as Co-alumina and Sn-alumina catalysts, for the reduction of NOX and other unburned species contained in the exhaust gas. In the experiments, DME concentration in the exhaust gas was changed by adding extra DME before the catalytic reactor, which is the important experimental parameter in the research. Results showed that NOX reduction rate was not so high without any DME addition, because the content of unburned DME, reducing agent, is very low in the DME engine exhaust gas. However, NOX reduction rate increased with increase in DME content and it reached around 80% with enough DME addition. The NOX reduction rate increased with increase in reaction temperature up to around 300 °C. The possibility of methanol and formaldehyde formation on the catalyst bed at lower reaction temperature was also pointed out. Copyright © 1999 Society of Automotive Engineers, Inc.

Applying Flame Colors to Mixture Strength Measurement in Laminar Premixed Flames (2nd Reprot)
TATSUTA Setsuo, FUJITA Osumu, ITO Kenichi
Transactions of the Japan Society of Mechanical Engineers. Series B., 64, 625, 3084, 3090, The Japan Society of Mechanical Engineers, 1998, [Peer-reviewed]
Japanese, The flame color method to measure mixture strength in laminar premixed flames was investigated as a new combustion diagnostic technique. Flame colors were quantitatively determined by chromaticity coordinates (x, y) defined by the CIE 1931 standard colorimetric system. Using 12 types of hydrocarbons, the (x, y) of an inner cone in premixed laminar flames held on a circular tube burner were measured with a colorimeter, and the relationship between the (x, y) and the equivalence ratio φ of the mixture was examined in a range of φ=0.9 to 1.4. The experimental results indicated that the equivalence ration could be measured with accuracy of 0.008-0.014 and error due to axial position in the inner cone was less than 0.02-0.05. Humidity of air had almost negligible effects on the accuracy of the measurement. Results also indicated that the effect of back-light could be corrected by introducing the concept of additive mixture of color stimuli.

Quantitative Determination of Flame Color and Its Determining Factor in Hydrocarbon/Air Laminar Diffusion Flames
TATSUTA Setsuo, FUJITA Osamu, ITO Kenichi
Transactions of the Japan Society of Mechanical Engineers. Series B., 64, 624, 2669, 2676, The Japan Society of Mechanical Engineers, 1998, [Peer-reviewed]
Japanese, The color of laminar diffusion flames burning propane, methane and ethylene was determined by chromaticity coordinates (x, y) defined by the CIE 1931 standard colorimetric system. The differences in flame color attributed to burning condition and fuel types were examined with a colorimeter. Spectroscopic measurement and numerical analysis using a simplified radiation model were also carried out to discuss the determining factors of the flame color. The relation between x and y measured on the central axis of the flames was expressed in the experimental equations. The (x, y) in the luminous region plotted on a chromaticity diagram changed along Planckian locus with the burning conditions. The contribution of the thermal radiation of soot particles and the chemiluminescence to the flame color was successfully evaluated by introducing the concept of additive mixture of color stimuli. The (x, y) profiles from the numerical analysis agreed well with the experimental results.

Determination of magnetic field effects on a jet diffusion flame in a microgravity environment
O Fujita, K Ito, T Chida, S Nagai, Y Takeshita
TWENTY-SEVENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, VOLS 1 AND 2, 27, 2573, 2578, COMBUSTION INSTITUTE, 1998, [Peer-reviewed]
English, International conference proceedings, The effect of magnetic fields on a laminar jet diffusion flame has been investigated by using a microgravity enviromnent. The magnetic field was changed from fairly low (around 0 mT) to strong (around 215 mT) intensities. The effect of oxygen concentration was also investigated. The buoyancy caused by gravity is dominant for diffusion flames under normal gravity, so the microgravity environment was used to allow;an observation of the effect of the magnetic field on combustion, especially for weak magnetic Fields. A steady flame could be sustained with a field intensity larger than a critical value that depends on the O-2 concentration. The critical value was determined experimentally and evaluated with a nondimensional number corresponding to the Grashof number used for gravitational fields. The changes in combustion characteristics. that is, flame shape, length, brightness, and color, were evaluated as a function of the magnetic-field intensity. The flame length decreased with increases in the magnetic-field strength, and the color of the flame shifted from red to yellow, indicating a temperature increase with increases in magnetic-field strength. By evaluating the changes in the flame color with chromaticity treatment, it was concluded that the effect of the magnetic field is dominated by F [O-2], where F is the magnetic force acting on the combustion, a function of field strength, and [O-2] is the surrounding oxygen concentration.

Experimental study on flame spread over wire insulation in microgravity
M Kikuchi, O Fujita, K Ito, A Sato, T Sakuraya
TWENTY-SEVENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, VOLS 1 AND 2, 27, 2507, 2514, COMBUSTION INSTITUTE, 1998, [Peer-reviewed]
English, International conference proceedings, An experimental study of flame spread phenomena over ETFE (ethylene-tetrafluoroethylene)-insulated wires has been performed in microgravity to obtain basic data on the fire safety of wire insulation. Three samples with different wire diameters, d(w) (0.32-0.51 mm) and the same insulation thickness, delta (0.15mm) were investigated. The effects of time parameters thought dominant for wire combustion in fires: the ambient oxygen concentration, wire initial temperature, T-i, wire diameter, d(w), pressure, and dilution gas were investigated in the microgravity experiments. A series of comparative experiments were also conducted at normal gravity. The results show that flame spread rates in microgravity are higher than vertically downward spread rates at normal gravity when oxygen concentration is greater than 30% O-2. However, with wire preheating, the spread rate in microgravity is higher than time downward spread rate at normal gravity even at lower O-2 concentrations. The increase in flame spread rates in microgravity became larger with decreases in d(w). Time effect of pressure on the flame spreading appeared very small, and lower pressure caused extinction of the flames in microgravity. The increase in flame spread rates in microgravity was especially large with CO2 dilution, and this must be taken into account when selecting extinguisher gas. The microgravity experiments with CO2 dilution gave rise to a new unsteady flame spread phenomenon for flame spreading over the wire: this phenomenon involves discontinuous flames partly occurring ahead of the spreading flame front.

Observation of Ignition and Flame Spread of Paper Sheet in Slow External Flow under Microgravity
Osamu Fujita, Masao Kikuchi, Kenichi Ito, Sandra L.Olson, Takashi Kashiwagi, Takashi Sakuraya
Journal of Microgravity Science and Application, 14, 1, 10, 18, 日本マイクログラビティ応用学会, 1997, [Peer-reviewed]
Japanese, Scientific journal

Effect of thermophoretic force on soot agglomeration process in diffusion flames under microgravity　　　　　　　　　　　　　　　
Osamu Fujita, Kenichi Ito, Hiroyuki Ito, Yasuhiro Takeshita
NASA Conference Publication, 10194, 217, 222, NASA, 1997
English, International conference proceedings, Soot agglomerate formation in diffusion flames under microgravity is quite different from those under normal gravity. Soot particles in a diffusion flame adhere to each other to form very large visible agglomerates. The combustion field of a butane diffusion flame was investigated to explain the mechanism of large soot agglomerates formation under microgravity. The large soot agglomerates form due to the combination of thermophoretic forces and long residence time in a microgravity environment.

Magnetic support of combustion in diffusion flames under microgravity
NI Wakayama, H Ito, Y Kuroda, O Fujita, K Ito
COMBUSTION AND FLAME, 107, 1-2, 187, 192, ELSEVIER SCIENCE INC, Oct. 1996, [Peer-reviewed]
English, Scientific journal, Flames in an O-2-containing atmosphere rely on natural or forced convection to replenish reactants and remove hot products. Because natural convection is absent under microgravity, diffusion flames become spherical, have low power, and eventually are extinguished. This paper deals with a simple method of generating convective air flows on the application of magnetic fields and supporting combustion under microgravity conditions. Magnetic fields, which act on paramagnetic oxygen, attract fresh air rich in O-2 and push out the combustion products. Thus, a diffusion flame in air was quenched after a few seconds under microgravity. However, when compact permanent magnets were installed, this diffusion flame became more brilliant and shorter than with normal gravity and continued to burn without changing its shape or luminosity during 10 sec of microgravity. Large soot particles, which are characteristic under microgravity, disappeared. These experiments demonstrate that magnetic fields induce air flows and support combustion completely with microgravity. The present method will also be useful to burn liquid or solid fuel under microgravity without forced convection by compressors.

Visualization of formaldehyde distribution above platinum plate catalyst by using LIF method
W Kang, O Fujita, K Ito
JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME, 118, 1, 82, 87, ASME-AMER SOC MECHANICAL ENG, Mar. 1996, [Peer-reviewed]
English, Scientific journal, Visualization has been attempted to measure formaldehyde formation during catalytic combustion of methanol/air mixtures. The visualization of formaldehyde distribution above a platinum plate in methanol premixed gas flows was carried out by a LIF (laser-induced fluorescence) method. Formaldehyde (CH2O) has fluorescence spectra in the 340.6-493.3-nm range when it is excited by the third harmonic wavelength of Nd:YAG laser (355 nm). In our study, formaldehyde was excited by a pulse laser shot and the florescence at wavelength of 412.2 nm was selected for investigation. By this laser technique, the time resolved instantaneous distribution of formaldehyde on the platinum plate was successfully observed. The results show that the distribution of formaldehyde fluorescence is affected by gas velocity, catalyst temperature, and especially excess air ratio. The results correspond well with the results of a mathematical modeling for formaldehyde formation over Pt, and it confirms that this method is useful for analyzing the mechanism of catalytic combustion.

Applying Flame Colors to Mixture Strength Measurement in Laminar Premixed Flames
TATSUTA Setsuo, FUJITA Osamu, ITO Kenichi
Transactions of the Japan Society of Mechanical Engineers. Series B., 62, 593, 368, 373, The Japan Society of Mechanical Engineers, 1996, [Peer-reviewed]
Japanese, A mixture strength measurement in laminar premixed flames is based on changes in flame colors caused by the variation of mixture strength. Flame colors were quantitatively determined by chromaticity coordinates (x, y) defined by the CIE 1931 standard colorimetric system. The (x, y) of an inner cone in fuel/air premixed laminar flames held on a circular tube burner were measured with a colorimeter, and the relationship between the (x, y) and the equivalence ratio of the mixture was examined in a range where the equivalence ratio varied from about 0.9 to 1.4. The results of the experiments indicate that the equivalence ratio can be measured with an accuracy of more than 0.04 in LPG, gasoline, kerosene and city gas 6 C flames. The results also indicate that in the LPG flames burning conditions such as burner diameter, mixture velocity and mixture temperature have almost negligible effects on the accuracy of the measurement.

Effects of slow wind on localized radiative ignition and transition to flame spread in microgravity
T Kashiwagi, KB McGrattan, SL Olson, O Fujita, M Kikuchi, K Ito
TWENTY-SIXTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, VOLS 1 AND 2, 26, 1345, 1352, COMBUSTION INSTITUTE, 1996, [Peer-reviewed]
English, International conference proceedings, An experimental and numerical investigation of ignition and the subsequent transition to flame spread over a thermally thin cellulosic sample is described. The experiments were conducted using a lamp as an external radian; source in a 50% oxygen atmosphere at three different wind velocities of 0, 2, and 5 cm/s in a 10 s drop tower. The results show that there are no significant effects of the slow wind on the ignition-delay time. Photographic sequences of both the experiments and the calculations show that the wind increases the flame propagation speed in the upwind direction, while decreasing it in the downstream direction. The downstream flame fails the transition to flame spread and becomes a tail of the upstream flame. The downstream char front propagates much slower than that for the upstream direction. Three-dimensional, time-dependent numerical solutions to the Navier-Stokes equations are used to simulate the experiments. Three global degradation reactions describe the pyrolysis of the sample paper, and one gasphase reaction describes the combustion of the fuel gases. The model results reflect the qualitative features of the experiments and also are in reasonable quantitative agreement, given the uncertainty of the gasphase reaction mechanism.

Visualization of Formaldehyde Distribution Produced in Catalytic Oxidation of Methanol on Platinum Plate by LIF Method.
Fujita Osamu, Ito Kenichi, Kang Woo, Tanaka Keiichi, Morita Tomoji
Transactions of the Japan Society of Mechanical Engineers Series C, 61, 591, 4214, 4218, The Japan Society of Mechanical Engineers, 1995, [Peer-reviewed]
Japanese, The visualization for analyzing the reaction mechanism of catalytic combustion of methanol/air mixture has been newly attempted. The measurement of formaldehyde distribution above a platinum plate in premixed methanol gas flows was carried out by the LIF (laser-induced fluorescene) method. Formaldehyde has the fluorescence spectra in the range of 340.6∼493.3 nm when it is excited by the thrid-harmonic wavelength of the Nd : YAG laser (355 nm). In this work, formaldehyde was excited by one pulsed laser shot and the fluorescence at wavelength of 412.2 nm was selected. By this laser technique, the time-resolved instantaneous distribution of formadehyde yielded during catalytic combustion of methanol/air mixtures on a platinum plate has been successfully measured. The results show that the distribution of formaldehyde fluorescence above the platinum plate is affected by gas velocity, catalyst temperature, and, in particular, air-fuel ratio. These results show good correspondence with those of other studies of conventional flow-reactor experiments, and con-firm that this measurement is a reliable method for analyzing the reaction mechanism of catalytic combustion.

AGGLOMERATION OF SOOT PARTICLES IN-DIFFUSION FLAMES UNDER MICROGRAVITY
H ITO, O FUJITA, K ITO
COMBUSTION AND FLAME, 99, 2, 363, 370, ELSEVIER SCIENCE INC, Nov. 1994, [Peer-reviewed]
English, Scientific journal, Experiments have been conducted to investigate the behavior of soot particles in diffusion flames under microgravity conditions using a 490-m drop shaft (10-s microgravity duration) in Hokkaido, Japan. Flames from the combustion of paper sheets and butane jet diffusion flames are observed under microgravity. The oxygen concentration of the surroundings, the butane flow rate, and the burner diameter are Varied as experimental parameters. The generated soot particles are sampled under microgravity and observed using scanning electron and transmission electron microscopes. The flames with a residual convection or forced convection are also observed to examine the influence of flow held on soot particle generation under microgravity. From these results, it is found that a number of large luminous spots appear in diffusion flames under microgravity. From the observation of TEM images, the luminous spots are the result of agglomerating soot particles and the growth of their diameters to a discernible level. The diameter of the agglomerated particles measure about 0.1 mm, 200 to 500 times as large as those generated under normal gravity. It is suggested that these large soot particles are generated in the limited areas where the conditions for the formation of these particles, such as gas velocity (residence time) and oxygen concentration, are satisfied.

Generation of Carbon Particles in Diffusion Flames under Microgravity Condition
Kenichi Ito, Hiroyuki Ito, Osamu Fujita
Transactions of the Japan Society of Mechanical Engineers Series B, 60, 570, 662, 667, 1994, [Peer-reviewed]
English, Scientific journal, The behavior of soot particles was investigated under the microgravity condition using a 490 m (10 second microgravity duration) drop shaft. A butane jet diffusion flame was formed above a burner tube with 6 mm inner diameter. The fuel velocity and the oxygen concentration of surroundings were varied. Generated carbon particles were sampled and their detailed structures were observed using the electron microscope. The results showed that characteristic soot clusters were formed in the flames under microgravity. It was found that the generated soot particles in the flames under microgravity were agglomerated and grew to about 200–500 times as large as one generated under normal gravity. © 1994, The Japan Society of Mechanical Engineers. All rights reserved.

Formaldehyde Purification of Methanol Engine Exhaust Gas Using Automotive Oxidation Catalyst
Osamu Fujita, Kenichi Ito, Kang Woo, Nobuhiro Watanabe
Transaction of Japan Society of Mechanical Engineers B, 59, 565, 2914, 2918, May 1993, [Peer-reviewed]
Japanese, Scientific journal

メタノール予混合触媒燃焼器の開発における問題点　　　　　　　　　　　　　　　
日本機械学会論文集B, 59, 545, 242, 247, 1993, [Peer-reviewed]

Measurement of Flame Propation Speed of Coal Dust Cloud using Microgravity Environment
FUJITA O.
Heat Transfer in Microgravity, 269, 59, 66, 1993, [Peer-reviewed]

QUANTITATIVE-DETERMINATION OF FLAME COLORS BASED ON CIE 1931 STANDARD COLORIMETRIC SYSTEM
S TATSUTA, O FUJITA, K ITO
IMAGING IN TRANSPORT PROCESSES, 471, 479, BEGELL HOUSE, INC, 1993, [Peer-reviewed]
English, International conference proceedings

QUANTITATIVE CHARACTERIZATION OF FLAME COLOR AND ITS APPLICATION - (INTRODUCTION OF CIE-1931 STANDARD COLORIMETRIC SYSTEM)
K ITO, H IHARA, S TATSUTA, O FUJITA
JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES, 35, 2, 287, 292, JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG, May 1992, [Peer-reviewed]
English, Scientific journal, The colors of propane/air premixed flames were quantitatively characterized by the chromaticity coordinates (x,y) defined by the CIE 1931 standard colorimetric system. Detailed relations between flame colors and flame spectra were investigated in the range of air ratio from 0.7 to 1.2. The experimental results indicated that the chromaticity coordinates are useful to accurately express the change of flame color caused by the variation of air ratio. It was also found that the flame colors are mainly attributed to the relative spectral intensity of the CH bands, the C2 bands and the continuous spectrum and that the continuous spectrum plays an important role in the color determination, especially for the lean mixture. Moreover, it was suggested that flame color can be used to evaluate the air ratio and the relative spectral intensity. Thus the flame color could possibily be a valuable information source for combustion diagnostics, and is applicable to combustion control and monitoring systems.

Effective Parameters on the Start-up Characteristics of a Catalytic Combustor Using Methanol Mixture.
CHOI Byung-Chul, ITO Kenichi, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 58, 545, 242, 247, The Japan Society of Mechanical Engineers, 1992, [Peer-reviewed]
Japanese, The emission problem of a catalytic combustor using methanol mixture arises during the start-up condition. A modified quasi-steady-state model is used to analyze the transient behavior of the catalytic combustor. Parameters considered in this study were air-fuel ratio, preheat temperature of the catalyst, space velocity, heat input, catalyst length, combustion efficiency and heat loss coefficient. From the numerical computation, the range of operating parameters of the catalytic combustor during transient condition can be predicted with sufficient accuracy. The transient combustion efficiency was found to be greatly affected by the space velocity, preheat of the catalyst and air-fuel ratio. At a condition of the air-fuel ratio and heat input, the required catalyst length to achieve a certain combustion efficiency can also be predicted.

Some Problems in Developing a Catalytic Combustor Using Methanol Mixture.
CHOI Byung-Chul, ITO Kenichi, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 58, 554, 3208, 3213, The Japan Society of Mechanical Engineers, 1992
Japanese, Experimental studies have been carried out to investigate some problems in the development and practical use of a catalytic combustor using a methanol mixture. For the suppression of undesirable exhaust emission, the possibility of using a catalyst with a higher amount of noble metal than the usual level as a component of the entire catalyst layer is examined. The combustion characteristics of the catalytic combustor with water-containing methanol and with aged catalysts are also investigated. From the results, it was found that undesirable exhaust emission during the startup period was suppressed by use of the higher noble metal loaded catalyst as a component of the catalysts. Formaldehyde emission was increased as the contained water was increased in the range of zero to 15wt%. The reaction region moved downward with the use of the aged catalyst, and the catalyst temperature profile was decreased. This indicates that the emission characteristic on unburned species is degraded.

THE START-UP CHARACTERISTICS OF A CATALYTIC COMBUSTOR USING A METHANOL MIXTURE
K ITO, BC CHOI, O FUJITA
JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES, 33, 4, 778, 784, JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG, Nov. 1990, [Peer-reviewed]
English, Scientific journal

火炎色の定量的表現とその応用　　　　　　　　　　　　　　　
日本機械学会論文集Ｂ, 56, 531, 304, 307, 1990, [Peer-reviewed]

The characteristics of oxidation catalyst for methanol engine exhaust gas --Unburned methanol and formaldehyde under an unsteady engine opoeration--　　　　　　　　　　　　　　　
JSAE Review, 11, 4, 8, 14, 1990, [Peer-reviewed]

Quantitative characterization of flame color and its application. Introduction of CIE 1931 standard colorimetric system.
ITO Kenichi, IHARA Hiroyuki, TATSUTA Setsuo, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 56, 531, 3508, 3513, The Japan Society of Mechanical Engineers, 1990
Japanese, The study on quantitative characterization of flame colors was carried out by using the chromaticity coordinates (x, y) defined by the CIE 1931 standard colorimetric system. Propane/air premixed flames were used in the study. It was found that the coordinates could characterize the colors of flames with various air ratios and contained information about the spectral intensity of CH and C₂ radicals in the flames. These results suggest that flame colors, which had previously been considered qualitative because of their dependence on fallible human perception, can be used to evaluate flame behavior quantitatively. There is a good possibility that the measurement of the colors is applicable to combustion control and monitoring systems.

メタノール予混合気を利用した触媒燃焼器の定常状態の運転特性　　　　　　　　　　　　　　　
韓国機械学会論文集, 13, 6, 1223, 1230, 1989, [Peer-reviewed]

The start-up characteristics of a catalytic combustor using methanol mixture.
ITO Kenichi, CHOI Byung-Chul, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 55, 519, 3552, 3557, The Japan Society of Mechanical Engineers, 1989, [Peer-reviewed]
Japanese

CATALYTIC-OXIDATION OF UNBURNED METHANOL WITH THE PRESENCE OF ENGINE EXHAUST COMPONENTS FROM A METHANOL FUELED ENGINE
O FUJITA, K ITO
JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES, 31, 2, 314, 319, JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG, May 1988, [Peer-reviewed]
English, Scientific journal

Catalytic oxidation of unburned methanol with presence of engine exhaust components from a methanol-fueled engine.
FUJITA Osamu, ITO Kenichi
Transactions of the Japan Society of Mechanical Engineers Series C, 53, 495, 3454, 3458, The Japan Society of Mechanical Engineers, 1987, [Peer-reviewed]
Japanese, The mathanol oxidation reaction on the catalysts of Pt, Pd, Rh, Ir and Cu has been investigated to select the suitable catalysts for the purification of methanol engine exhaust gases. On all of these catalysts, the presence of NO showed an inhibitory effect on the methanol oxidation reaction and caused the formation of formaldehyde. By comparison with other exhaust components (CO, H₂O, HC), it was found that NO had a stronger effect than other species. Under the presence of NO, the relative activity sequence was also obtained as Pt≒Pd>Rh≒Ir>Cu. The temperature conditions for formaldehyde formation were revealed for each catalyst in the presence of NO, and it was also found that formaldehyde formation was most suppressed by use of the Pd catalyst. Consequently, Pd is one of the advantageous catalysts for reducing unburned methanol.

NO共存下でのメタノール触媒酸化反応　　　　　　　　　　　　　　　
自動車技術会論文集, 36, 94, 106, 1987, [Peer-reviewed]

AN APPLICATION OF THE SELECTIVE CONTACT REDUCTION METHOD BY NOX-NH3 REACTION TO A METHANOL FUELED SI ENGINE EXHAUST SYSTEM
K ITO, O FUJITA
BULLETIN OF THE JSME-JAPAN SOCIETY OF MECHANICAL ENGINEERS, 29, 258, 4291, 4296, JAPAN SOC MECHANICAL ENGINEERS SANSHIN HOKUSEI BLDG, Dec. 1986, [Peer-reviewed]
English, Scientific journal

An application of the selective contact reduction method by NOx-NH3 reaction to a methanol fueled S. I. engine exhaust system.
ITO Kenichi, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 52, 476, 2004, 2010, The Japan Society of Mechanical Engineers, 1986, [Peer-reviewed]
Japanese, The catalytic reduction of NO_x by NH₃ generated from NO_x has been applied to a methanol engine exhaust system. In automotive three-way catalyst (Pt-Rh coated) a large amount of NO_x was converted to NH₃ in a temperature range of 500550 K and an excess air ratio of 0.91.0. On the other hand, NO_x reduction by NH₃ in methanol engine exhaust gas was favorably performed under the condition of O₂=24%, gas temperature= 450500 K and NH₃≥ the stoichiometry of NO_x. Finally, about half an amount of NO_x was converted to NH₃ in a three-way catalyst and the formed NH₃ was reached with the NO_x left in the exhaust gas. The resulting NO_x reduction ratio was around 55%. On the basis of these results, some systems using the application of NO_x-NH₃ reactions to practical engines were proposed and their potential was discussed.

Application of second order derivative spectrophotometer to the measurement of CH2O, NO, NO2 and NH3 in exhaust gases from a methanol fueled SI Engine　　　　　　　　　　　　　　　
K.Ito, T.Yano, O.Fujita
ASME HTD, 45, 331, 336, Nov. 1985, [Peer-reviewed]
English, Scientific journal

Effect of NO on catalytic oxidation of unburned methanol
K.Ito, O.Fujita
Transaction of Japan Society of Mechanical Engineers B, 51, 463, 1066, 1070, The Japan Society of Mechanical Engineers, Mar. 1985, [Peer-reviewed]
Japanese, Scientific journal, The effects of NO on catalytic oxidation of methanol and HC were experimentally investigated. Prepared gas which contained N₂, O₂, C₃H₈, CH₃ OH and NO was passed through the oxidation and three-way catalysts designed for motor vehicles. The changes in unburned species were examined under the conditions of inlet temperature and space velocity ranges of 400∼525K and 2.5∼7.5 ×10⁴/h, respectively. The presence of NO made the HC made the HC oxidation ratio high, but it made the methanol oxidation ratio low in the catalysts bed. Furthermore, it was observed that formaldehyde generation from methanol in the catalysts increased under the presence of NO. From these results, it can be concluded that NO emission plays an important role in the catalytic oxidation reaction. Thus, the effects of NO should be considered in the design on of motor vehicle catalyst.

The effects of NO2 on catalytic oxidation of unburned species from a methanol fueled spark ignition engine
Kenichi Ito, Osamu Fujita
Symposium (International) on Combustion, 20, 1, 53, 59, 1985, [Peer-reviewed]
English, Scientific journal, Catalytic oxidation processes of unburned species in methanol combustion products are examined with emphasis on the role of NO2. Two kinds of experiments were carried out. One was on the catalytic oxidation of the exhaust gases from a methanol fueled spark ignition engine, and the other on prepared gases which simulated the engine exhaust gases. Exhaust gases of air-fuel equivalence ratio ranging from 0.8 to 1.5 were investigated. In the catalyst bed, unburned methanol, formaldehyde, NO and NO2 concentrations were determined at gas temperatures ranging from 400 to 540 K. Experimental results were expressed by two parameters, methanol oxidation ratio and NO2 reduction ratio. As soon as the exhaust gas entered the catalyst bed, methanol was oxidized and its concentration decreased. At the same time, NO2 decreased, while NO increased. The methanol oxidation ratio had a maximum value at an equivalence ratio of about 1.2 and was related to the NO2 emission characteristics. The conversion of NO2 to NO was improved by the presence of methanol and the oxidation of methanol was promoted by NO2, within the experimental range. In comparison with ethanol combustion products, the effect of NO2 in catalytic oxidation was greater for methanol combustion products because of the higher NO2 concentration in the methanol combustion products. © 1985 Combustion Institute.

NO/NO2 conversion in methanol engine exhuaust gas　　　　　　　　　　　　　　　
K.Ito, T.Yano, O.Fujita
Transaction of Japan Society of Mechanical Engineers, 51, 461, 231, 238, Dec. 1984, [Peer-reviewed]
Japanese, Scientific journal

NO/NO2 conversion in methanol burned gas. (In case of S.I. engine)
ITO Kenichi, YANO Toshiaki, FUJITA Osamu
Transactions of the Japan Society of Mechanical Engineers Series C, 50, 460, 3059, 3067, The Japan Society of Mechanical Engineers, 1984
Japanese, メタノールを火花点火エンジンで燃焼した場合,排ガス中に含まれるNO₂量の多いことが知られている.この原因が,未燃メタノールの酸化過程と関連したNOからNO₂への酸化(NO/NO₂変換)によるものであることを明らかにした.変換の条件を反応管を用いて細に調べた結果,このNO/NO₂変換は700～950Kの温度場において著しく,また,他燃料との比較からメタノール燃焼排ガスに特有の現象であることをつかんだ.

Spray, droplet evaporation, combustion, and emission characteristics of future transport fuels for compression-ignition engines: A review
Leang So Khuong, Nozomu Hashimoto, Osamu Fujita, Journal of Traffic and Transportation Engineering (English Edition), 11, 4, 575, 613, Aug. 2024
This review examines the potential of hydrogen, ammonia, and biodiesel as alternative fuels, focusing on spray dynamics, droplet evaporation, combustion, and emissions. Hydrogen offers superior combustion characteristics but faces challenges in NOx emissions. Strategies like non-premixed direct injection, increased intake boost pressure, and low-pressure EGR are suggested for robust hydrogen combustion in compression-ignition engines. Control of hydrogen start of injection (SOI) and water injection (WI) are identified as effective techniques for reducing NOx emissions. Ammonia shows inferior combustion and higher NOx and unburned NH3 emissions in the same conditions as conventional fuels with conventional engines. Understanding ammonia spray and evaporation conditions is significant for optimizing an ammonia-air mixture and minimizing wall impingement and ammonia trap in the crevice, thereby improving combustion and emission reduction. Increasing intake pressure, injection pressure, and EGR rate, employing a turbulent jet, and preheating ammonia improve efficiency and reduce NOx emissions. Utilizing ammonia combustion requires the implementation of after-treatment systems such as NH3 adsorber and DeNOx catalysts to mitigate unburned NH3 and NOx emissions. Biodiesel affects the fuel supply system, combustion, and emission characteristics according to its viscosity and density. Increasing injection pressure and blending with volatile fuels enhance spray and combustion. Optimum biodiesel preheating temperatures for the injection pump and injector are crucial for achieving the best pump capacity and spray formation. By utilizing biodiesel-PODE blends and investigating low-temperature biodiesel combustions, there is potential to improve thermal efficiency and PM-NOx trade-off. Therefore, carbon-neutral fuel adoption should be accelerated to mitigate CO2 emissions, highlighting the importance of combustion techniques and emissions reduction strategies., Book review

Solid Combustion Experiment on the ISS/Kibo-Progress in the FLARE Project-
高橋周平, 鳥飼宏之, 小林芳成, 菊池政雄, 藤田修, 燃焼シンポジウム講演論文集(CD-ROM), 60th, 2022

Effect of heat transfer through wire core toward unburned region on the extinction of spreading flame over electric wires
金野佑亮, 橋本望, 藤田修, 日本機械学会熱工学コンファレンス講演論文集(CD-ROM), 2020, 2020

Observation of downward flame spread phenomenon over electric wires with different insulation thickness
蝋山大樹, 金野佑亮, 橋本望, 藤田修, 燃焼シンポジウム講演論文集(CD-ROM), 58th, 2020

Effect of the heat conduction along the core wire on the downward flame spread over an electric wire
金野佑亮, 橋本望, 藤田修, 燃焼シンポジウム講演論文集(CD-ROM), 57th, 2019

Estimation of Blow-off Limit for Flame Spreading over Electric Wires in High Opposed Flow Field
佐藤宏樹, 金野佑亮, 橋本望, 藤田修, 日本機械学会年次大会講演論文集(CD-ROM), 2019, 2019

Study on Flammability of Thermally Thick Insulated Wires: Effects of Insulation Thickness and Gravity Level on Flammability
野一色郁武, 金野佑亮, 橋本望, 藤田修, 日本機械学会熱工学コンファレンス講演論文集(CD-ROM), 2019, 2019

Validation of the multi-component fuel droplet evaporation model in a laminar counterflow kerosene surrogate combustion field
Nozomu Hashimoto, Yushin Naito, Kinya Saito, Jun Hayashi, Noriaki Nakatsuka, Fumiteru Akamatsu, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. In this study, the droplet evaporation model for multi-component fuels, which can consider the distributions of the mass fraction of the components and the temperature inside the droplet, was developed. The developed model was incorporated with the computational fluid dynamics codes, FrontFlowRed-Comb (NuFD/FFR extended by Kyushu University, CRIEPI, Kyoto University and NuFD). Using the codes with the developed model, the numerical simulation for the spray combustion filed formed by the laminar counter flow burner were conducted. The droplet evaporation constants calculated by the developed model were compared with those calculated by the non-equilibrium Langmuir-Knudsen evaporation model and those measured by the High-speed Interferometric Particle Imaging for Droplet Sizing (Hs-ILIDS) method. As a result, it was found that some components, whose boiling temperature is low, were pre-vaporized before the droplet reaches the high temperature flame zone. Finally, it is confirmed that the developed multi-component fuel evaporation model can accurately predict the droplet evaporation in a spray combustion field.

Effect of Le on transition to parametric instability in downward propagating flames
Ajit Kumar Dubey, Yoichiro Koyama, Sung Hwan Yoon, Nozomu Hashimoto, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. Flames propagating downward from open to closed end in a tube are prone to thermo-acoustic instability. At sufficiently high burning velocity (SL) two regimes of instability are observed, namely, primary instability (where initial cellular flame transitions to a flat flame) and a secondary instability (where flat flame transition to turbulent flame due to parametric instability of flame front). On further increasing SL flat flame is not observed and initial cellular flame directly transitions to parametric instability. This SL is called critical SL here. This work presents the effect of Le (Lewis number) on critical SL. Experiments reveal that larger Le condition has higher critical SL compared to lower Le condition. Theoretical calculations of instability of planar flame front in presence of acoustic forcing are presented. Effect of Le is successfully captured by the theory as predicted stability region of planar flame is narrower for lower Le as compared to higher Le. However, quantitative agreement for critical SL between experiments and theory is obtained only after applying a correction factor which is a function of and Le.

Opposed-flow flame spread over thin electric wires
Yusuke Konno, Nozomu Hashimoto, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. An attempt to develop a theoretical model for the flame spreading over electric wires in an opposed-flow configuration is made. To explore the role of the core wire in the flame spread process, a polymer coated single metallic wire is considered in the analysis. In addition, both the core wire and insulation are treated as thermally-thin to simplify the problem. A one-dimensional heat transfer equation for the core wire and insulation are used to describe the flame spread problem over the wire insulation. The qualitative trends of calculated axial temperature profiles of the core wire and flame spread rates are not inconsistent with available experimental data and phenomenological descriptions made by the previous studies. These results reveal that the downstream flame plays a significant role in the flame spread process over the electric wire in opposed-flow due to the presence of the core wire.

Experimental Comparison on Transition Criteria to Parametric Instability of a Downward-propagating Flame in a Tube Induced by Single Laser Irradiation and Double Laser Irradiation
Nguyen Truong Gia Tri, Nozomu Hashimoto, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. Previous single laser irradiation (SLI) method is confirmed to be effective to study an interaction between pressure fluctuation and flame geometry as the method can control the flame front shape actively. This method allows to generate a transition from primary acoustic instability to parametric instability in downward propagating flame in a combustion tube. Adopting this method, the double laser irradiation (DLI) method is further developed and is applied to the same combustion tube experiments for the first time. DLI method could form double cellular structure, while SLI just forms single large cell. The effect of flame curvature and cell number are examined based on the transition criteria regarding critical laminar burning velocity. The results revealed that for Le > 1 flame, DLI is more efficient in triggering the transition. Specifically, at a given laminar burning velocity, DLI required lower total laser power to derive transition than SLI did. Moreover, using the same total laser power, DLI deformed the flame to give larger flame front area and produced higher average acoustic intensity. The present paper can provide useful information on the effect of amplitude and wavenumber induced by laser irradiation on the transition criteria from primary acoustic instability to parametric instability.

Influence of three lithium salts on the flame behaviors and extinction limits of dimethyl carbonate-based electrolytes using a wick combustion method
Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. Flammability studies of electrolytes are required for screening safer materials used in lithium-ion batteries. To clarify the influence of lithium salts addition on the flammability of organic electrolyte solvents, experimental combustion analyses were conducted using a unique wick combustion system in conjunction with limiting oxygen concentration (LOC) test, called wick-LOC method. The dimethyl carbonate (DMC)-based electrolytes with 1M addition of three different lithium salts (LiPF6, LiBF4, and LiTFSI) were studied with the comparison of pure DMC and organophosphorus compound added solvents. The three lithium salts gave unique and distinct flame behaviors including flame shapes, colors and the changes of wick surface until self-extinguishing. LOC results indicated the considerable flame-retardant effect of LiPF6-addition, while other salts have very limited effects on flame extinction. Flame spectrums were analyzed to find how different salts contribute to the combustion of electrolytes. The lithium in the LiPF6 and LiBF6 were captured to form solid products during combustion. The PF6 anion acted as a similar role to the phosphorus-containing flame-retardant in the flame. The additional effect of LiTFSI on cotton wick pyrolysis and burning were considered as a potential hazard on solid combustible in the real fire case.

Development and validations of droplet evaporation model for low ignitibility fuel considering inner distributions under atmospheric pressure
Yushin Naito, Nozomu Hashimoto, Osamu Fujita, 12th Asia-Pacific Conference on Combustion, ASPACC 2019, 01 Jan. 2019
© Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved. Accurate prediction of the evaporation process in spray combustion can contribute to optimal design for the combustor. One of the objectives of this study is to develop a high accuracy simulation technique for spray combustion. In order to achieve this objective, single droplet evaporation model for multi-component fuel considering inner distributions was developed. The developed model was verified by using light cycle oil at various ambient temperature. First, the effects of the enthalpy diffusion term in heat flux from the gas phase to the liquid phase on droplet evaporation were investigated in various ambient temperature. According to the comparison between calculation results and experiment results, it was found that the calculation results of the evaporation model considering the enthalpy diffusion term which is calculated in detail is better agreement with experimental results. As a result of validations for the developed model, it was found that there are differences between the predictions and experiments in low ambient temperature because high volatile fuel species vaporized in experiments before droplet evaporation was observed. Finally, the model considering pre-evaporation could predict the droplet evaporation characteristics with high precision at various ambient temperature.

Validation of multi-component fuel droplet evaporation model for laminar counter flow kerosene spray flame
橋本望, 内藤雄心, 齋藤欣也, 林潤, 中塚記章, 赤松史光, 藤田修, 燃焼シンポジウム講演論文集, 56th, ROMBUNNO.D322, 14 Nov. 2018
Japanese

Verification of Multicomponent Fuel Droplet Evaporation model for Kerosene under Various Ambient Temperature
内藤雄心, 上田健五, ALEXIS Lefevre, 橋本望, 菅沼祐介, 野村浩司, 藤田修, 燃焼シンポジウム講演論文集, 56th, ROMBUNNO.D311, 14 Nov. 2018
Japanese

Effect of Ambient Pressure on Spreading over Wire Insulation under Opposed Flow Condition in Microgravity
永地大志, 三井郁矢, CITERNE Jean‐Marie, DUTILLEUL Hugo, GUIBAUD Augustin, JOMAAS Grunde, JOMAAS Grunde, LEGROS Guillaume, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 56th, ROMBUNNO.D334, 14 Nov. 2018
Japanese

微小重力下における電線被覆上を燃え拡がる火炎の温度に関する検討
都築克弥, 金野佑亮, 佐藤宏樹, 橋本望, 藤田修, 日本火災学会研究発表会概要集, 2018, 82‐83, 29 May 2018
Japanese

Downward flame spread and extinction phenomena of externally heated electric wire: Effect of materials geometry and opacity on its flammability
金野佑亮, 野一色郁武, 橋本望, 藤田修, 日本機械学会熱工学コンファレンス講演論文集(CD-ROM), 2018, 2018

数値解析によるポリエチレン被覆電線上燃え拡がり火炎の限界酸素濃度における熱バランス評価
会田裕樹, 橋本望, 藤田修, 日本伝熱シンポジウム講演論文集(CD-ROM), 55th, ROMBUNNO.A221, 2018
Japanese

微小重力環境下における並行空気流中の電線被覆上燃え拡がり火炎の観察
永地大志, 三井郁矢, CITERNE Jean‐Marie, DUTILLEUL Hugo, GUIBAUD Augustin, JOMAAS Grunde, LEGROS Guillaume, 橋本望, 藤田修, 日本伝熱シンポジウム講演論文集(CD-ROM), 55th, ROMBUNNO.A222, 2018
Japanese

Opposed-flow flame spread over electric wire: The effect of ambient oxygen concentration on flame size and flame spread rate
金野佑亮, 都築克弥, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 55th, 66‐67, 13 Nov. 2017
Japanese

Preheating effect on the extinction limit for a flame spreading over polyethylene coated wire
三井郁矢, CITERNE Jean‐Marie, DUTILLEUL Hugo, JOMAAS Grunde, GUILLAUME Legros, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 55th, 464‐465, 13 Nov. 2017
Japanese

Prediction of Soot Formation in Pulverized Coal Combustion field of 0.5kg/coal/h pulverized coal jet burner by Large Eddy Simulation Employing the TDP model.
高橋弥楊, 橋本望, 渡邊裕章, 黒瀬良一, 藤田修, 燃焼シンポジウム講演論文集, 55th, 446‐447, 13 Nov. 2017
Japanese

Numerical Investigation on Extinction Phenomena of Flame Spreading over Polyethylene Insulated Wire in Microgravity
会田裕樹, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 55th, 534‐535, 13 Nov. 2017
Japanese

乱れ強さおよび粒子濃度が球状に伝播する微粉炭火炎に及ぼす影響
市村涼, KHALID Hadi Bin, 橋本望, 藤田修, 化学工学会秋季大会研究発表講演要旨集(CD-ROM), 49th, ROMBUNNO.EB123, 20 Sep. 2017
Japanese

分解軽油(LCO)液滴の蒸発特性に関する実験的研究
内藤雄心, 橋本望, 高木正英, 川内智詞, 今井康雄, 三ツ井裕太, 青木剛, 林利昭, 野村浩司, 菅沼祐介, 藤田修, 日本機械学会北海道支部講演会講演概要集(CD-ROM), 55th, ROMBUNNO.432, 18 Sep. 2017
Japanese

微小重力下における熱的に厚い電線被覆上を燃え拡がる火炎の消炎限界の推定
宮本恭輔, 金野佑亮, 橋本望, 藤田修, 日本火災学会研究発表会概要集, 2017, 178‐179, 20 May 2017
Japanese

Flame spread and dripping behaviors in horizontal and vertical wires
Y. Kobayashi, X. Huang, Y. Konno, S. Nakaya, M. Tsue, N. Hashimoto, O. Fujita, C. Fernandez-Pello, 10th U.S. National Combustion Meeting, 2017-April, 2017
© 2017 Eastern States Section of the Combustion Institute. All rights reserved. Dripping of polymer insulations in wire fire has a potential risk of igniting nearby objects and expanding the size of the fire, but has not been well studied so far. In this work, dripping behaviors during the flame spread over horizontal and vertical polyethylene (PE) insulated wires were investigated. Wires of 8-and 9-mm diameter with and stainless steel core were tested. The temperature profile of core and insulation were also measured during the flame spread. Experimental results showed that a high-conductance copper core acted as a heat source downstream to increase the flame spread. However, in the upstream burning region, the copper core acted as a heat sink, cooling and reducing the mobility of melting insulation. Therefore, the copper core facilitates burning and reduce dripping. Moreover, in the vertical downward flame spread, the insulation drips flowed downward to preheat the wire, and this dripping heating dominated over the heating by the core. Therefore, higher dripping fraction for wires with lower thermal conductance resulted in a faster flame spread. This is the first time that the simultaneous dual effect of the heat source and heat sink for wire core was observed, and the influence of dripping on the flame spread over the wire was discovered.

Experimental Study of Evaporation Characteristics of Low Ignitibility Fuel Droplet at High Temperatures and Pressures
Naito Yushin, Hashimoto Nozomu, Takagi Masahide, Kawauchi Satoshi, Imai Yasuo, Mitsui Yuta, Aoki Go, Hayashi Toshiaki, Nomura Hiroshi, Suganuma Yusuke, Fujita Osamu, The Proceedings of Mechanical Engineering Congress, Japan, 2017, 0, 2017
<p>It is needed to greatly modify fuel component because of strengthened sulfur component regulations in fuel oil for ships by IMO (International Maritime Organization). Light Cycle Oil (LCO) which contains less sulfur component has been focused as a base fuel. The increase of the LCO mixing ratio in fuels for diesel engines is expected in the future. Evaporation characteristics which are one of a physical process in spray combustion affect flame stabilities and combustion emissions. The objective of this study is to clarify the relationships between evaporation characteristics and fuel characteristics of LCO by conducting evaporation experiments of LCO. The evaporation experiments of LCO were conducted by single LCO droplets at various ambient temperatures (473~873 K) and pressures (0.1, 0.5, 1.0 MPa). Moreover, the evaporation characteristics of 5 types LCO were compared to clarify how the fuel properties affect the evaporation characteristics. As a result, it was found that the difference of the droplet lifetimes between fuels is large at low ambient temperature. This is because high boiling components in LCO make the droplet lifetimes of LCO longer from the middle to the late of evaporation. The pressure dependence of evaporation coefficient of some LCO at high ambient temperature was different from that of single component fuel. This is possibly caused by effect of multicomponent of LCO on the behavior of the evaporation coefficients.</p>, The Japan Society of Mechanical Engineers, Japanese

Dimensional Analysis for Flammability Limits of Spreading Flame over Electric Wire in Microgravity
KONNO Yusuke, TSUZUKI Katsuya, HASHIMOTO Nozomu, FUJITA Osamu, The Proceedings of Mechanical Engineering Congress, Japan, 2017, 0, G0600105, 2017
<p>An attempt to develop a scale model to estimate extinction limits of spreading flame over electric wires in opposed flow under microgravity has been made. Ethylene tetrafluoroethylene (ETFE) insulated copper (Cu) wire is chosen as the sample wire because of the availability of its experimental data. The results showed that the estimated extinction limits given by the scale model developed in the present work corresponded well with experimental results qualitatively. However, further modifications of individual sub-models are expected to provide quantitative estimation.</p>, The Japan Society of Mechanical Engineers, Japanese

No.2-8 Experimental Study on Effect of Turbulence Intensity on Spherical Turbulent Flame Propagation of Pulverized Coal Particle Cloud
橋本望, KHALID Hadi Bin, 市村涼, 藤田修, 日本エネルギー学会石炭科学会議発表論文集(Web), 54, 68‐69(J‐STAGE), 2017
Japanese

周囲空気流速が電線被覆上燃え拡がり火炎の消炎現象に与える影響の数値解析による考察
会田裕樹, 橋本望, 藤田修, 日本伝熱シンポジウム講演論文集(CD-ROM), 54th, ROMBUNNO.A211, 2017
Japanese

異なる心線材質を持つ電線被覆上燃え拡がり火炎の消炎限界に及ぼす初期着火条件の影響
三井郁矢, 永地大志, CITERNE Jean‐Marie, DUTILLEUL Hugo, JOMAAS Grunde, LEGROS Guillaume, 橋本望, 藤田修, 日本伝熱シンポジウム講演論文集(CD-ROM), 54th, ROMBUNNO.A135, 2017
Japanese

The Effect of Ambient Gases on Evaporation Characteristics of n-Hexadecane Droplet under High Pressure
佐藤 佑衣子, 内藤 雄心, 橋本 望, 村越 好泰, 菅沼 祐介, 野村 浩司, 藤田 修, 微粒化シンポジウム講演論文集, 25, 217, 222, 19 Dec. 2016
日本液体微粒化学会, Japanese

微小重力場におけるポリエチレン被覆電線上燃え拡がり火炎消炎限界の対向流と並行流における比較
永地大志, 三井郁矢, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 54th, B313, 26 Nov. 2016
Japanese

微小重力場における被覆導線の通電着火現象に対する被覆厚さ影響
清水晃平, 藤田修, 橋本望, 菊池政雄, 燃焼シンポジウム講演論文集, 54th, B312, 26 Nov. 2016
Japanese

熱的に厚い模擬電線被覆上を燃え拡がる火炎の消炎現象に関する検討
宮本恭輔, 金野佑亮, HUANG Xinyan, FERNANDEZ‐PELLO Carlos, 橋本望, 藤田修, 燃焼シンポジウム講演論文集, 54th, B314, 26 Nov. 2016
Japanese

微小重力場における被覆導線の過電流連続通電時の着火限界に関する数値的検討
清水晃平, 橋本望, 菊池政雄, 藤田修, 日本機械学会年次大会講演論文集(CD-ROM), 2016, ROMBUNNO.G0600504, 10 Sep. 2016
Japanese

電線被覆上燃え拡がり火炎の消炎限界に及ぼす外部輻射の影響
宮本恭輔, 水谷拳, 金野佑亮, HUANG Xinyan, FERNANDEZ‐PELLO Carlos, 橋本望, 藤田修, 日本火災学会研究発表会概要集, 2016, 32‐33, 11 May 2016
Japanese

Flammability limit of polyethylene insulated wires under varying oxygen concentration and external radiation
Kyosuke Miyamoto, Xinyan Huang, Nozomu Hashimoto, Carlos Fernandez-Pello, Osamu Fujita, 2016 Spring Technical Meeting of the Western States Section of the Combustion Institute, WSSCI 2016, 01 Jan. 2016
Future space mibions may require spacecraft cabin environments to have elevated oxygen concen-Trations and reduced ambient prebure. Electrical cables and harnebes have been identified as a key source of fires in the spacecraft cabin. In this work, a group of experiments is conducted to measure the ammability limit of the opposed ame spread over wire under varying oxygen con-centration and external radiation. Wires with different dimensions (8 and 9 mm), core conditions (with and without copper core) and insulation materials (transparent LDPE and HDPE) are exam-ined. Measurements show that external radiation extends the ammability limit to a lower limiting oxygen concentration (LOC) in the linear manner for all wire configurations. Experimental results also reveal that the copper core acts as a heat sink to increase the wire ammability limit, and its cooling effect increases with the core conductance. The ammability limit of high-conductance HDPE insulated wire is found to be larger than that of LDPE, implying that the small difference in insulation micro-structure may not be neglected in wire fire safety design. In addition, the min-imum oxygen concentration, below which ame cannot be sustain even under intensive radiation, is found to be around 14.5% for wires with core, much higher than those without core. Afterwards, a simplified theoretical analysis is used to phenomenologically explain the discovered ammability limit and minimum oxygen concentration.

5-1-2 Application of TDP model to Unsteady Numerical Simulation for Lab-Scale Pulverized Coal Burner
TAKAHASHI Hiroyasu, HASHIMOTO Nozomu, WATANABE Hiroaki, KUROSE Ryoichi, FUJITA Osamu, Proceedings of the Annual Conference of The Japan Institute of Energy, 25, 0, 142, 143, 2016
<p>In pulverized coal combustion, it is generally known that coal particle's heating rate affects its devolatilization behavior. In previous research conducted by N. Hashimoto et al, TDP (Tabulated Devolatilization Process) Model [1] which enables to take heating rate effects into account by using devolatilization database was suggested. TDP model has already applied for steady numerical simulation. However, it has not yet applied for unsteady numerical simulation. In this research, therefore, TDP model was applied to unsteady simulation. To investigate its validity, numerical simulation for lab-scale pulverized coal burner was performed. As its application results, coal particle's heating rate is calculated for each particle size and extraction of appropriate devolatilization parameter from the database is done. In addition, location of calculated particles with high temperature distribution was in good agreement with experimental direct photograph's luminous flame position.</p>, 一般社団法人 日本エネルギー学会, Japanese

電線被覆上燃え拡がり火炎の消炎限界に及ぼす初期着火条件の影響
三井郁矢, 永地大志, CITERNE Jean‐Marie, DUTILLEUL Hugo, JOMAAS Grunde, LEGROS Guillaume, 橋本望, 藤田修, 日本機械学会熱工学コンファレンス講演論文集(CD-ROM), 2016, ROMBUNNO.D123, 2016
Japanese

微小重力場における被覆電線の連続通電着火現象に対する数値的検討
SHIMIZU KOHEI, FUJITA OSAMU, HASHIMOTO NOZOMU, KIKUCHI MASAO, 燃焼シンポジウム講演論文集, 53rd, 500, 501, 04 Nov. 2015
Japanese

微小重力下における電線被覆上燃え拡がり火炎の消炎限界推定モデルの検討
MIZUTANI KEN, MIYAMOTO KYOSUKE, HASHIMOTO NOZOMU, FUJITA OSAMU, 燃焼シンポジウム講演論文集, 53rd, 502, 503, 04 Nov. 2015
Japanese

D131 Difference of Extinction Limit of Spreading Flame over Polyethylene Insulated Wire between Opposed Air Flow and Concurrent Air Flow
Nagachi Masashi, Yoshioka Kosuke, Hashimoto Nozomu, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2015, "D131, 1"-"D131-2", 23 Oct. 2015
Tests with flames spreading over wires in microgravity were performed at external opposed flow and concurrent flow conditions to examine the influence of flow direction on the extinction limit. In the experiments, low density polyethylene insulated Nickel-chrome and Copper wire samples were used. The experiments were conducted both in normal gravity and microgravity. Limiting Oxygen concentration (LOC) of microgravity is lower than that of normal gravity because of inhibited natural convection. LOC of Nickel-chrome is lower than that of Copper because of difference of heat conduction loss. The minimum LOC of concurrent flow is smaller than that of opposed flow in the range of 1-2%., The Japan Society of Mechanical Engineers, Japanese

Research on Instability of Propagating Flames in a Combustion Tube by using Laser Irradiation Method
FUJITA Osamu, J.Combustion Society of Japan, 57, 181, 174, 182, Aug. 2015, [Invited]
日本燃焼学会, Japanese, Introduction scientific journal

FLAREプロジェクトにおける電線燃焼研究の状況
FUJITA OSAMU, MIZUTANI KEN, MIYAMOTO KYOSUKE, YOSHIOKA KOSUKE, HASHIMOTO NOZOMU, 宇宙科学技術連合講演会講演集(CD-ROM), 59th, ROMBUNNO.3E04, 2015
Japanese

微小重力環境における電線試料の消炎限界酸素濃度低下に対する被覆材料影響
MIZUTANI KEN, MIYAMOTO KYOSUKE, HASHIMOTO NOZOMU, FUJITA OSAMU, 日本伝熱シンポジウム講演論文集(CD-ROM), 52nd, ROMBUNNO.B221, 2015
Japanese

Introduction of Research Projects on Solid Material Combustion utilizing ISS/Kibo and Their Expected Outcome
藤田 修, 日本燃焼学会誌, 56, 176, 117, 124, May 2014, [Invited]
日本燃焼学会, Japanese, Introduction scientific journal

Overview of "Solid Combustion" experiment in the ISS/KIBO
Takanari Mizushima, Masao Kikuchi, Masahiro Takayanagi, Hiroyuki Torikai, Akihiko Ito, Shuhei Takahashi, Osamu Fujita, Proceedings of the International Astronautical Congress, IAC, 1, 718, 723, 01 Jan. 2014
Copyright © 2014 by the International Astronautical Federation. All rights reserved. Our research entitled "Quantitative Description of Gravity Impact on Solid Material Flammability as a base of Fire Safety in Space(Solid Combustion)" will be carried out in the Japanese Experiment Module/KIBO in the ISS. The main target of the research is to clarify the impact of gravity on the the material flammability. In the research, we select the wire and sheets as the material that is rerated to fire safety. With these samples, the flammability in microgravity regarding two fundamental processes of solid combustion, that is, (1) solid material ignitior and (2) flame spread over solid material, is quantitatively investigated. Then, the validity of the current flammability tests will be verified with clarifying the discrepancy between the data in normal gravity and microgravity. In the Exp.I, the flammability in microgravity regarding solid material ignition is quantitatively investigated with polyethylene insulated wires, under the several conditions of the oxygen concentration, current value, electrified time. In the Exp. II, III, IV the flammability in microgravity regarding flame spread

短時間微小重力環境を利用した固体材料の燃焼性に関する研究　　　　　　　　　　　　　　　
藤田 修, International Journal of Microgravity Science Application, 31, 1, 31, 37, Jan. 2014, [Invited]
Japanese, Introduction scientific journal

Ignition and Combustion Characteristics of Highly Densified Biomass Briquette
Ito Hiroyuki, Ida Tamio, Fujita Osamu, 神奈川大学工学研究所所報, 36, 16, 21, Nov. 2013
総説, 神奈川大学工学研究所, Japanese

A113 Ignition of Electric Wire Insulation Caused by Continuous Excess Current Supply in Microgravity
Fujita Osamu, Shigeta Naoki, Procee[d]ings of Thermal Engineering Conference, 2013, 5, 6, 18 Oct. 2013
Ignition tests of overloaded electric wire were carried out in microgravity provided by airplane parabolic flight. Polyethylene insulated NiCr core wire (inner core diameter 0.5 and outer diameter 0.8 mm) was used as a test sample. The results showed that the ignition limit in terms of supplied electric power dramatically decreased with increase in microgravity time. It was suggested that the total electric energy supplied to the wire gave the primary criteria for ignition, which was consistent with experimental findings. Further, the importance of conductive heat loss to the surroundings was pointed out for very low electric current condition according to the simple one-dimensional numerical calculation., The Japan Society of Mechanical Engineers, Japanese

B134 Influence of the condition of non-equilibrium plasma application on the yield of cellulose pyrolysis products
Ito Hiroyuki, Endo Shota, Kambara Shinji, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2013, 61, 62, 18 Oct. 2013
The influence of non-equilibrium Ar plasma on the composition of tar obtained by cellulose pyrolysis was investigated. When Ar plasma is given to the cellulose pyrolysis from the beginning of the experiments (from room temperature), the collected tar composition is almost the same with no plasma condition. In the case plasma is given after furnace temperature becomes higher than 300℃, the rate of furfural in the collected tar increases and the rate of levoglucosan decreases. From the results, it is suggested that decrease in decomposition temperature or increase in pyrolysis rate is caused by applying non-equilibrium Ar plasma to the cellulose pyrolysis., The Japan Society of Mechanical Engineers, Japanese

I213 Influence of non-equilibrium Ar plasma on the yield of cellulose pyrolysis product
Ito Hiroyuki, Neoi Wataru, Kambara Shinji, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2012, 477, 478, 16 Nov. 2012
The influence of non-equilibrium Ar plasma on the yield and composition of cellulose pyrolysis product is investigated. Dielectric barrier discharge (DBD) is used to obtain Ar plasma. The amount of products (gas, collected tar and residual char) are determined and the composition of the collected tar is analyzed by GC-MS. Gas yield decreases and the collected tar in the low temperature range increases with plasma, whereas the temperature in the pyrolysis furnace may change little. It is also suggested that applying plasma may change the reaction pathway of cellulose decomposition because the composition of collected tar has the different tendency to that observed with the temperature increase., The Japan Society of Mechanical Engineers, Japanese

403 Comparison of thermodynamical potentials of oxy-fuel combustion and conventional air-combustion
Sato Kenichi, Fujita Osamu, 北海道支部講演会講演概要集, 2012, 51, 117, 118, 20 Oct. 2012
The Japan Society of Mechanical Engineers, Japanese

Pb-206 Investigation on ignition and subsequent combustion of BIG (Bio-coke) block
ITO Hiroyuki, NAKAHARA Takero, SAKAI Yuto, IDA Tamio, FUJITA Osamu, Proceedings of the Conference on Biomass Science, 0, 7, 150, 151, 18 Jan. 2012
Fundamental thermal and combustion properties of the Bio-coke (BIC) have been investigated. At first ignition and combustion behaviors are observed in the hot air flow. The results show that the ignition mode and the mass loss rate during the flaming combustion are influenced by the supplied air temperature with an interesting manner. This may be ascribed to the thickness of the heated layer inside the BIC depending on the preheating condition. A new concept of BIC combustion method, called "end face combustion", is proposed considering the BIC unique physical features as well as its fundam..., The Japan Institute of Energy, Japanese

Numerical Simulation of the Pyrolysis of Solid Waste in an Externally Heated Rotary Kiln
岡崎輝幸, 鈴木朋子, 山本研二, 仲田博幸, 藤田修, 大島伸行, 日本機械学会論文集 B編(Web), 78, 786, 2012

Formation characteristics of high-density and high-hardness new briquette based on herby biomass
Satoru Mizuno, Tamio Ida, Manabu Fuchihata, Kunihiko Namba, Atsushi Kakosaka, Osamu Fujita, Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy, 91, 1, 41, 47, 2012
The aim of the lapanese cabinet council's 'Biomass Nippon Strategy' is to increase the utilization of biomass as one of the ways to reduce the dependence on fossil resources. However, there are various problems associated with the use biomass, one of which is the cost associated with the collection and transportation of biomass. Biomass has high moisture content and low bulk density. The biomass solidification technology developed by Ida et al. partly aims to solve the transportability problem. This study shows physical properties of high density and hardness of the new briquette produced from herby biomass. The relationship between apparent density and maximum compressive strength and an effect on the maximum compressive strength by black colorization are considered. Also, an attempt is made to explain the effect on properties of the briquette by hemi-cellulose and lignin in the region before semi-carbonized region. As a result, the relation between the apparent density and the compressive strength shows that maximum value exists as characteristics of the herby briquette. The maximum apparent density for all processing conditions is 1.38 g/cm3 at the initial moisture 0.10 kg/kg-wet -processing temperature 473 K. The maximum compressive strength for all processing conditions is 127 MPa at the initial moisture 0.05 kg/kg-wet -processing temperature 453 K. Furthermore, the effect of black colorization indicates that when the area of black colorization is increased for the surface of herby biomass briquette by increased in the processing temperature, the maximum compressive strength is decreased due to reduction in the adhesion of lignin. Consequently, high-density and high-hardness of the new briquette can be controlled by the initial moisture and the processing temperature., Japanese

I213 Considerations on gas evolution from the bio-coke fuel caused by heating
Ito Hiroyuki, Sakai Yuto, Ida Tamio, Wakatsuki Kaoru, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2011, 383, 384, 28 Oct. 2011
The evolution characteristics of degradation gas from highly densified biomass briquette called Bio-coke (BIC) are experimentally and numerically investigated. In the present study, evolution rates of both volatile and water from the sample are determined as Arrhenius-type equations and the constants such as frequency factors and activation energies are given by the thermo-gravimetric analysis. It is confirmed that the model used in the study can qualitatively describe the gas evolution from the BIC sample. With high water content, the time volatile evolution start is delayed because much heat is consumed to evaporate the water. In the period before the volatile evolution start, the rate of evolved water to the whole water increases with increasing the water content of the BIC sample., The Japan Society of Mechanical Engineers, Japanese

G060034 Investigation on the characteristics of pyrolysis gas evolution from BIC (Bio-coke) fuel
ITO Hiroyuki, SAKAI Yuto, IDA Tamio, WAKATSUKI Kaoru, FUJITA Osamu, Mechanical Engineering Congress, Japan, 2011, "G060034, 1"-"G060034-5", 11 Sep. 2011
The evolution characteristics of degradation gas from highly densified biomass briquette called Bio-coke (BIC) are experimentally and numerically investigated. In the present study, evolution rates of both volatile and water from the BIC sample are determined by Arrhenius equations and the constants such as frequency factors and activation energies are given by the experimental results of thermo-gravimetric analysis. It is confirmed that the analysis model used in the study can qualitatively describe the gas evolution from the BIC sample. Rapid increase in the gas evolution rate is identified when the BIC sample ( 0 20 mm x 10 mm) is heated at an end face of the sample. This can be attributed to the finite volume of the BIC sample; the rapid temperature increase can be observed after the water in the sample is completely released. The volatile/water ratio in the evolution gas takes constant value at heat flux higher than 50 kW/m2 while the ratio gradually increases with time at the low heat flux case (25 kW/m2)., The Japan Society of Mechanical Engineers, Japanese

7-327 Internship Student Exchange with ENSMA in France and its Contribution to Student Education
FUJITA Osamu, 工学教育研究講演会講演論文集, 23, 59, 622, 623, 22 Aug. 2011
Japanese Society for Engineering Education, Japanese

高圧縮固体バイオマス燃料の燃料利用
伊東弘行, 酒井雄人, 井田民男, 藤田修, 日本燃焼学会誌, 53, 164, 63, 68, May 2011, [Invited]
Japanese, Introduction scientific journal

微小重力環境を利用した固体燃焼現象研究(H22研究班WG報告)
藤田修, 中村祐二, 永田晴紀, 菊池政雄, 伊藤昭彦, 鳥飼宏之, 梅村章, 高橋周平, 池田光優, CHUNG Suk Ho, OLSON Sandra L, 宇宙利用シンポジウム, 27th, 31, 32, Mar. 2011
第27回宇宙利用シンポジウム (2011年1月24日-25日, 宇宙航空研究開発機構宇宙科学研究所相模原キャンパス), 相模原市, 神奈川県
The Twenty-seventh Space Utilization Symposium (January 24-25, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan
Since solid combustion is dominated by diffusion process of pyrolyzed gas as well as heat transfer process around the combustion region, flammability limit becomes very different depending on the gravitational conditions. In the present work, an attempt to know the mechanism of the extension of ignition limit of overloaded wire has been made by numerical calculation. The results showed that the Joule energy more than a critical value causes release of degradation gas and its ignition, and the critical value becomes smaller in microgravity than that in normal gravity. Further, the preparation status of the ISS experiment including the wire ignition and flame spread over solid material is introduced.
著者人数: 11人
形態: カラー図版あり
Number of authors: 11
Physical characteristics: Original contains color illustrations
資料番号: AA0065129013, 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS), Japanese

ISS日本実験棟における固体材料燃焼研究（Solid Combustion）　　　　　　　　　　　　　　　
藤田 修, 日本マイクログラビティ応用学会誌, 28, 3, 90, 95, 2011, [Invited]
Japanese, Introduction scientific journal

309 The Effect of Electric Field on Single-Walled Carbon Nanotube in Flame Method
ONISHI Akira, MASUNAGA Kota, FUJITA Osamu, NAKAMURA Yuji, ITO Hiroyuki, 北海道支部講演会講演概要集, 2010, 49, 67, 68, 07 Nov. 2010
The Japan Society of Mechanical Engineers, Japanese

D113 Effect of ambient pressure on consumption rate of melting polyethylene coated over electric wire
Iwakami Junya, Nakamura Yuji, Wakatsuki Kaoru, Ito Hiroyuki, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2010, 0, 93, 94, 29 Oct. 2010
Flame spread behavior over electric wire coated polyethylene (PE) in low pressure is studied experimentally. The objective of this study is to investigate the relationship between consumption rate of melting PE and ambient pressure. The ambient gas composition is fixed to the same as air and total pressure is set to sub-atmospheric range (30〜100 kPa). Dynamic behavior of molten PE under various conditions is precisely observed/recorded in order to analyze the growth rate of molten PE and increment of spread rate in time with various types of wires. It turns out that the growth rates in the ..., The Japan Society of Mechanical Engineers, Japanese

E213 Ignition and combustion behavior of bio-coke fuel placed in high temperature air flow
Ito Hiroyuki, Sakai Yuto, Fujita Osamu, Nakamura Yuji, Ida Tamio, Procee[d]ings of Thermal Engineering Conference, 2010, 0, 319, 320, 29 Oct. 2010
Ignition and combustion characteristics of Bio-coke (BIC, highly densified biomass briquette) in high temperature air flow have been investigated. In the present study, ignition behavior is observed, and the mass loss rates for flaming combustion and surface combustion are measured. The experimental results showed that the surface ignition precedes gas-phase ignition in the case of high temperature air, while surface ignition and gas-phase ignition simultaneously occur in the case of low temperature air. Consequently, it is suggested that the temperature distribution inside BIC, i.e. the pr..., The Japan Society of Mechanical Engineers, Japanese

G0600-8-5 Effects of DC Electric Field on Carbon Nanotube Synthesis
MASUNAGA Kohta, ONISHI Akira, ITO Hiroyuki, NAKAMURA Yuji, FUJITA Osamu, The proceedings of the JSME annual meeting, 2010, 3, 209, 210, 04 Sep. 2010
The purpose of this study is to reveal the effects of DC electric field on carbon nanotube (CNT) synthesis. In flame synthesis method, it is considered that there are two effects of DC electric field which promotes CNT growth; i.e. generating ionic wind and enhancing catalytic activity. To distinguish the effect of DC bias on catalytic activity promotion, chemical vapor deposition (CVD) synthesis with high voltage DC bias is used in the present study. DC bias voltage is varied from -1.0 kV to +1.0 kV. It is confirmed that CNT growth is promoted by applying electric field. Moreover, it is su..., The Japan Society of Mechanical Engineers, Japanese

微小重力環境を利用した固体燃焼現象研究 (H21研究班WG報告)—Solid Combustion Research in Microgravity（2009 Research WG Report
藤田, 修, 中村, 祐二, 永田, 晴紀, 菊池, 政雄, 伊藤, 昭彦, 鳥飼, 宏之, 梅村, 章, 高橋, 周平, 池田, 光優, Fujita, Osamu, Nakamura, Yuji, Nagata, Harunori, Kikuchi, Masao, Ito, Akihiko, Torikai, Hiroyuki, Umemura, Akira, Takahashi, Shuhei, Ikeda, Mitsumasa, Chung, Suk Ho, 宇宙利用シンポジウム = Space Utilization Research: Proceedings of Space Utilization Symposium, 26, Feb. 2010
第26回宇宙利用シンポジウム(2010年1月25日-26日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス)
The Twenty-sixth Space Utilization Symposium (January 25-26, 2010: ISAS/JAXA Sagamihara, Japan)
Since solid combustion is dominated by diffusion process of pyrolyzed gas as well as heat balance around combustion area, flammability limit becomes very different depending on the gravitational conditions. In the present work, the attempt to obtain ignition limit for overloaded electric wire and extinction limits for spreading flame over flat sheet has been made under the limit of 4.5 sec microgravity time provided by MGLAB. According to the experiments, it is found that the flammable limits, ignition and extinction limits, significantly extend in microgravity in comparison with those in normal gravity.
形態: カラー図版あり
共催: 日本学術会議
Physical characteristics: Original contains color illustrations
joint hosting: The Science Council of Japan
資料番号: AA0064730020, 宇宙航空研究開発機構宇宙科学研究本部, Japanese

510 Unsteady phenomenon of spreading flame over wire insulation under microgravity
ONISHI Yosuke, TAKEUCHI Hiroyuki, FUJITA Osamu, ITO Hiroyuki, NAKAMURA Yuji, 北海道支部講演会講演概要集, 2009, 48, 155, 156, 28 Nov. 2009
The Japan Society of Mechanical Engineers, Japanese

B112 Observation of Ignition Process of Bio-coke Fuel Placed in High Temperature Air
Ito Hiroyuki, Sakai Yuto, Fujita Osamu, Nakamura Yuji, Ida Tamio, Procee[d]ings of Thermal Engineering Conference, 2009, 0, 33, 34, 06 Nov. 2009
Bio-coke, one of biomass fuels, is expected as a substitution to fossil fuel to prevent global warming as well as the other biomass energy. In this study, we investigate combustion characteristics of bio-coke in high temperature airflow, especially for ignition processes, which is not widely-known. Japanese knotweed is chosen as an ingredient of bio-coke. The gas temperature near the sample is measured by thermo-couple, the surface temperature of bio-coke is monitored by IR camera and the reduction of weight is scaled by a balance. It is identified that there are two types of ignition mode ..., The Japan Society of Mechanical Engineers, Japanese

T0501-4-7 A Study on Wire Insulation Ignition Induced by Short-term Excess Electric Current Application by using Microgravity Condition
KYONO Takeshi, FUJITA Osamu, KIDO Yasuhiro, NAKAMURA Yuji, ITO Hiroyuki, The proceedings of the JSME annual meeting, 2009, 8, 143, 144, 12 Sep. 2009
Ignition behavior of overloaded electric wire is investigated under various gravitational conditions to know the impact of surrounding flow field on the ignition process. The experimental parameters are oxygen concentration, supplied electric current value and the applied time. The result shows that the ignition phenomenon easily occurs in non-convective flow field (in microgravity), which is characterized by lower limit of electric current to attain ignition. Moreover, as a result of the observation by Mach-Zehnder interferometry, due to a distinguished difference of pyrolysis gas motions ..., The Japan Society of Mechanical Engineers, Japanese

F218 An Improvement of Start-up Characteristics of DME Catalytic Combustor for Mobile Use
Fujita Osamu, Tameda Kazuma, National Symposium on Power and Energy Systems, 2009, 14, 511, 512, 28 Jun. 2009
This study investigates low temperature startability of dimethyl-ether (DME) catalytic combustor as a small size heat generator. A procedure of DME pre-supply followed by mixture supply into the reactor shows great improvement of startability. With this procedure catalyst surface temperature increases caused by DME adsorption heat at the period of DME pre-supply and increased temperature promote catalytic reaction. When the period of DME pre-supply is excess, the reactor temperature turns decrease by increased heat loss in comparison with adsorption heat. The mechanism to appear the optimum condition of DME pre-supply to attain the best startability of DME catalytic combustor is discussed based on the DME adsorption characteristics to the catalyst surface., The Japan Society of Mechanical Engineers, Japanese

微小重力環境を利用した固体燃焼現象研究（H20研究班WG報告）—Solid combustion research in microgravity (2008 Research WG Report)
藤田, 修, 中村, 祐二, 永田, 晴紀, 菊池, 政雄, 伊藤, 昭彦, 鳥飼, 宏之, 梅村, 章, 高橋, 周平, 池田, 光優, Fujita, Osamu, Nakamura, Yuji, Nagata, Harunori, Kikuchi, Masao, Ito, Akihiko, Torikai, Hiroyuki, Umemura, Akira, Takahashi, Shuhei, Ikeda, Mitsumasa, Chung, Suk Ho, 宇宙利用シンポジウム = Space Utilization Research: Proceedings of Space Utilization Symposium, 25, Mar. 2009
第25回宇宙利用シンポジウム(2009年1月14日-15日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス)
The Twenty-fifth Space Utilization Symposium (January 14-15, 2009: ISAS/JAXA Sagamihara, Japan)
Since solid combustion is dominated by diffusion process of pyrolyzed gas as well as heat balance around combustion area, which are strongly affected by convective flow, micorgravity could be an effective tool to understand its mechanism. One of the most important contributions of solid combustion research in microgravity is fire safety in space. In the present report, some researches on going regarding fire safety in space will be introduced.
資料番号: AA0064297124, 宇宙航空研究開発機構宇宙科学研究本部, Japanese

411 Measurement of Products from DME Catalytic Combustion Operated in Fuel-Rich Condition
Tsukanaka Daisuke, Tameda Kazuma, Fujita Osamu, Nakamura Yuji, Ito Hiroyuki, 北海道支部講演会講演概要集, 2008, 47, 105, 106, 27 Sep. 2008
The Japan Society of Mechanical Engineers, Japanese

412 Effect of Gravity Condition on Wire Insulation Ignition : Observation of Ignition Phenomena in Normal Gravity
KYONO Takeshi, FUJITA Osamu, KIDO Yasuhiro, NAKAMURA Yuji, ITO Hiroyuki, 北海道支部講演会講演概要集, 2008, 47, 107, 108, 27 Sep. 2008
The Japan Society of Mechanical Engineers, Japanese

Activities of Hokkaido Applied Combustion Research Group
FUJITA Osamu, 日本燃焼学会誌 = Journal of the Combustion Society of Japan, 50, 153, 174, 175, 15 Aug. 2008
Japanese

実験力学ハンドブック　　　　　　　　　　　　　　　
朝倉書店, 2008, [Invited]

Comparison of Soot Formation Characteristics between DME Diffusion Flame and the Partially Premixed Methane Flame
Masanori KOBAYASHI, Ryosuke IMAI, Osamu FUJITA, Transaction of JSME, 74, 748, 2718, 2723, 2008

Effects of Radiation Feedback on Flame Spread along Polymer-Insulated Wire in Microgravity
Journal of the Combustion Society of Japan, 50, 153, 255, 263, 2008

Attainment of Luminous DME Spray Flame by Controlling Air Mixing at the Flame Base
Journal of the Combustion Society of Japan, 50, 153, 264, 270, 2008

E223 Improvement of Low Temperature Startability of Small Size DME Catalytic Combustor with Aid of Adsorption Heat
Tameda Kazuma, Fujita Osamu, Procee[d]ings of Thermal Engineering Conference, 2007, 335, 336, 23 Nov. 2007
This study investigates low temperature startability of dimethyl-ether (DME) catalytic combustor as a small size heat generator. A procedure of DME pre-supply followed by mixture supply into the reactor shows great improvement of startability. With this procedure catalyst surface temperature increases caused by DME adsorption heat at the period of DME pre-supply and increased temperature promote catalytic reaction. When the period of DME pre-supply is excess, the reactor temperature turns decrease by increased heat loss in comparison with adsorption heat. Consequently, it is suggested that the optimum condition for DME pre-supply exists to give best startability of DME catalytic combustor with this procedure., The Japan Society of Mechanical Engineers, Japanese

104 Effect of pre-adsorbed species on the startability of DME catalytic combustor as a use of small size heat generator
TAMEDA Kazuma, FUJII Toshio, FUJITA Osamu, 北海道支部講演会講演概要集, 2007, 46, 7, 8, 29 Sep. 2007
The Japan Society of Mechanical Engineers, Japanese

大学研究室めぐり、北海道大学機械宇宙工学専攻宇宙環境応用工学研究室
藤田 修, 工業加熱, 44, 4, 62, 68, Jul. 2007, [Invited]
日本工業炉協会, Japanese, Others

微小重力環境を利用した固体燃焼現象研究:研究班WG報告—Solid combustion research in microgravity: Research WG report
藤田, 修, 中村, 祐二, 永田, 晴紀, 菊池, 政雄, 伊藤, 昭彦, 梅村, 章, 高橋, 周平, Fujita, Osamu, Nakamura, Yuji, Nagata, Harunori, Kikuchi, Masao, Ito, Akihiko, Umemura, Akira, Takahashi, Shuhei, 宇宙利用シンポジウム 第23回 平成18年度 = Space Utilization Research: Proceedings of the Twenty-third Space Utilization Symposium, 137, 138, Mar. 2007
Since solid combustion is dominated by diffusion process of pyrolyzed gas as well as heat balance around combustion area, which are strongly affected by convective flow, microgravity could be an effective tool to understand its mechanism. One of the most important contributions of solid combustion research in microgravity is fire safety in space. In the present report, some researches on going regarding fire safety in space will be introduced. Because individual physical processes included in the solid combustion have different time scale, it is specially noted that combination of short-term and long-term microgravity experiments is important to proceed the researches on solid combustion in space.
資料番号: AA0063349036, 宇宙航空研究開発機構宇宙科学研究本部, Japanese

短時間微小重力環境を利用した燃焼研究と宇宙実験への展開　　　　　　　　　　　　　　　
藤田 修, 平成18年度宇宙環境利用の展望、（財）資源探査用観測システム・宇宙環境利用研究開発機構, 46, 58, Mar. 2007, [Invited]
Japanese, Introduction commerce magazine

微小重力環境を利用した火炎振動現象の研究－乱流火炎面に現れる不安定現象の解明を目指して－　　　　　　　　　　　　　　　
藤田 修, 宇宙環境利用に関する公募地上研究ニュース, 8, 4, 5, Mar. 2007, [Invited]
Japanese, Introduction commerce magazine

Flame oscillation phenomenon induced by external radiative heat supply
Transaction of JSME, 73, 727, 803, 808, 2007

Soot formation characterisitcs of DME diffusion flame
Transaction of JSME, 73, 727, 680, 686, 2007

B123 Characteristics of DME Catalytic Combustion as a Small Size Heat Source
FUJII Toshio, FUJITA Osamu, Procee[d]ings of Thermal Engineering Conference, 2006, 49, 50, 23 Nov. 2006
Dimethyl ether (DME) is used as a gaseous fuel which has many merits, and easy to transport and store. Catalytic combustion is a promising method to attain stable low temperature combustion. However, DME has less activity of catalytic combustion in comparison with hydrogen and methanol. Nonetheless, there is still few in a report of a study about the catalytic combustion of DME. The main objective in the present study is to investigate fundamental characteristics of DME catalytic combustion. The results showed that O_2 concentration of premixed gas affects the steady and transient behavior of DME catalytic combustion., The Japan Society of Mechanical Engineers, Japanese

微小重力環境を利用した固体燃焼現象検討ＷＧ報告—WG report on Solid Combustion in Microgravity
藤田, 修, 中村, 祐二, 永田, 晴紀, 菊池, 政雄, 伊藤, 昭彦, 岡島, 敏, 梅村, 章, 高橋, 周平, Fujita, Osamu, Nakamura, Yuji, Nagata, Harunori, Kikuchi, Masao, Ito, Akihiko, Okajima, Satoshi, Umemura, Akira, Takahashi, Shuhei, 宇宙利用シンポジウム = Space Utilization Research: Proceedings of Space Utilization Symposium, 22, Mar. 2006
第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京)
The Twenty-second Space Utilization Symposium (January 17-19, 2006: Science Council of Japan, Roppongi, Tokyo, Japan)
Since solid combustion, which has long time scale, is dominated by diffusion process of pyrolyzed gas, micorgravity could be an effective tool to understand its mechanism. One of the most important contributions of solid combustion research in microgravity is fire safety in space. In the present report, some researches attained previously as well as future expected subjects regarding fire safety in space will be introduced. Because individual physical processes included in the solid combustion have different time scale, combination of short-term and long-term microgravity experiments is requisite to proceed the research on solid combustion in microgravity.
形態: カラー図版あり
共催: 日本学術会議
Physical characteristics: Original contains color illustrations
Meeting sponsors: The Science Council of Japan, The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS)(JAXA)
資料番号: AA0064113029, 宇宙航空研究開発機構宇宙科学研究本部, Japanese

DME ハンドブック　　　　　　　　　　　　　　　
日本DMEフォーラム, 2006, [Invited]

Combustion Synthesis of Carbon Nanotubes under Microgravity Environment
NAKADE Yusuke, UCHIYAMA Tomoyasu, ITO Hiroyuki, FUJITA Osamu, JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 22, 4, 320, 320, 28 Nov. 2005
English

Effects of Gravity on Ignition of Polymer Insulated Wire induced by Excess Electric Current
NODA Hiroya, FUJITA Osamu, NAKAMURA Yuji, JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 22, 4, 318, 318, 28 Nov. 2005
English

314 DME火炎におけるすす生成特性(熱工学(2))
小林 雅律, 松村 智洋, 森岡 陽太郎, 藤田 修, 北海道支部講演会講演概要集, 2005, 44, 106, 107, 08 Oct. 2005
一般社団法人日本機械学会, Japanese

315 Catalytic Puriffication of NOx in DME Engine Exhaust Gas with Injection of Reducing Agent
FUJII Toshio, FUJITA Osamu, 北海道支部講演会講演概要集, 2005, 44, 108, 109, 08 Oct. 2005
The Japan Society of Mechanical Engineers, Japanese

Trend of Catalytic Combustion Research
FUJITA Osamu, Journal of the Combustion Society of Japan, 46, 138, 233, 241, 30 Nov. 2004
日本燃焼学会, Japanese

The Effect of Core Material on Combustion Behavior over Polyethylene Insulated Wire under Microgravity
FUJITA Osamu, NISHIZAWA Katuhiro, KUDO Takuya, JASMA : Journal of the Japan Society of Microgravity Application = 日本マイクログラビティ応用学会誌, 21, 79, 79, 04 Nov. 2004
English

Present and Future of Microgravity Combustion Research in Japan and USA
FUJITA Osamu, JASMA : Journal of the Japan Society of Microgravity Application, 20, 4, 286, 291, 30 Oct. 2003
Japanese

Description of planned microgravity facility and its use for combustion experiments
FUJITA Osamu, KATO Taichi, ITO Kenichi, JASMA : Journal of the Japan Society of Microgravity Application, 20, 23, 23, 23 Oct. 2003
English

Computational and Experimental studies of Thermophoretic Effect on Agglomeration of Soot Particles in Microgravity Diffusion Flame
CHOI Jaehyuk, TSUIKI Takafumi, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2003, 43, 148, 149, 28 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

Numerical Simulation of Flame Spread over Insulated Wire in Microgravity
SATOH Hiroyuki, FUJITA Osamu, NISHIZAWA Katsuhiro, UMEMURA Akira, UCHIDA Masahiro, KIKUCHI Masao, 北海道支部講演会講演概要集, 2003, 43, 146, 147, 28 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

Observation of a diffusion flame in a non-uniform magnetic field
SUGAWARA Akifumi, FUJITA Osamu, 北海道支部講演会講演概要集, 2003, 43, 100, 101, 28 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

Purification of DME Diesel engine exhaust gas by catalytic reactor
TSUKUDA Masakazu, HATTORI Naoki, FUJITA Osamu, 北海道支部講演会講演概要集, 2003, 43, 120, 121, 28 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

Effect of Radiation Absorption on the Flame Propagation in Tube
IKEDA Junichi, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2003, 43, 158, 159, 28 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

512 張力を与えたPEEK^[○!R]膜材の宇宙環境曝露実験(高分子材料の劣化)(一般セッション)
中村 孝, 中村 寛, 藤田 修, 野口 徹, 今川 吉郎, 学術講演会講演論文集, 52, 143, 144, 2003
日本材料学会, Japanese

Atomic Oxygen Irradiation on PEEK Sheet under Tensile Loads
NAKAMURA Hiroshi, NAKAMURA Takashi, NOGUCHU Toru, FUJITA Osamu, IMAGAWA Kichiro, TACHI Yoshiaki, 北海道支部講演会講演概要集, 2002, 42, 122, 123, 05 Oct. 2002
The relationship between the polymeric material degradation by atomic oxygen (AO) and tensile load was investigated. AO irradiation experiments were carried out at the facility of National Space Development Agency (NASDA). AO was irradiated to PEEK sheets under tensile stress. After AO exposure, surface observation, reaction efficiency (Re) measurements, and tensile tests were made on the sample. As a result, the following were obtained : (1) The circular irradiated region can be observed on all exposed samples. (2) Re was increased by AO exposure under tensile stress. (3) Conical pits were observed allover on all exposed specimens. (4) Elastic modulus was decreased by AO irradiation and this tendency was enhanced by applied stress. It was clear that stress affected polymer degradation by AO., The Japan Society of Mechanical Engineers, Japanese

Distribution of intermediate formation and heat release in high temperature air combustion : Spatial distribution of CO
JEON Byoungho, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2002, 42, 76, 77, 05 Oct. 2002
Combustion could be sustained even in ultra low oxygen concentration by utilizing highly preheated air. In this research, methane combustion in high temperature air is examined to know the fundamental characteristics of high temperature combustion. Intensity of heat release distribution is estimated by analyzing spatial distribution of carbon monoxide, which is a main intermediate of methane combustion. The results showed that the broad distribution of heat release could be attained with high temperature and low oxygen content. Using this combustion method to the industrial furnace, it is anticipated that the homogeneous heating or heat controlling of the furnace., The Japan Society of Mechanical Engineers, Japanese

Electron Beam Irradiation on PEEK Sheets under Tensile Loads
SAWAYA Masumi, NAKAMURA Takashi, NOGUCHI Toru, FUJITA Osamu, IMAGAWA Kichiro, TACHI Yoshiaki, 北海道支部講演会講演概要集, 2002, 42, 124, 125, 05 Oct. 2002
A polymer, PEEK, was investigated how tensile load would effect on its characteristics when irradiated by electron beam (EB). PEEK sheets under different tensile stresses were irradiated to EB by using the Combined Space Effects Test Facility of NASDA. After EB radiati on, mass measurements, surface observation and tensile tests were made on the samples. As a result, the following were obtained : (1) No major changes were not observed in mass measurements. (2) Irradiated surface showed no difference from non-irradiated surface. (3) Decreases in tensile strength and elongation were detected for the sheets irradiated under tensile stress., The Japan Society of Mechanical Engineers, Japanese

Gasification of coal at high temperature and elevated pressure
SHIMIZU Keisuke, FUJITA Osamu, ITO Kenichi, TAKAHASHI Jynya, 北海道支部講演会講演概要集, 2002, 42, 74, 75, 05 Oct. 2002
Gasification of coal with CO_2 under high temperature and elevated pressure has been investigated in normal and microgravity. The results showed that the increase in CO_2 pressure increased the gasification reaction rate. Further, the reaction rate was affected by the gravitational condition, that is, higher reaction rate in microgravity than in normal gravity. It seemed that natural convection is so strong that coal gasification was suppressed under normal gravity. On the other hand gasification reaction proceeded under microgravity because enough reaction time was available with reduced external flow., The Japan Society of Mechanical Engineers, Japanese

Synthesis of Carbon Nanotubes in Microgravity Diffusion Flame
FUJISAWA Kazuki, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2002, 42, 78, 79, 05 Oct. 2002
Flame synthesis of carbon nanotubes has been attempted in microgravity diffusion flame. The experiments were carried out with different fuel in various oxgen concentrations. Carbon nanotubes were collected from the diffusion flame for subsequent transmission electron microscopy (TEM) analysis by TEM grid. Finally some multi-walled carbon nanotubes with a diameter in the range of 5-20nm were found to grow on a Fe particle in diffusion flames. It was suggested that Fe particles acted as catalyst and flame synthesis could be a large-scale production method of carbon nanotubes., The Japan Society of Mechanical Engineers, Japanese

Observation of heavy droplet combustion in microgravity
SUDO Makoto, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2002, 42, 72, 73, 05 Oct. 2002
Combustion of heavy fuel droplet in microgravity was studied. The tested fuels were n-nonadecane and LCO. The external air flow velocity in the combustion chamber was 4.7cm/s. Laser extinction method has been used to measure droplet diameter and to visualize the soot distribution in the flame. Results showed that burning rate and soot volume increased with O_2concentration in the test of n-nonadecane. LCO combustion produced more soot than n-nonadecane and had lower burning rate than n-nonadecane in the same condition., The Japan Society of Mechanical Engineers, Japanese

Experience of Application to The First IAO for Microgravity Science
FUJITA Osamu, JASMA, 19, 3, 167, 170, 31 Jul. 2002
日本マイクログラビティ応用学会, Japanese

Research on Solid Material Ignition with Laser Irradiation in Microgravity
ITO Kenichi, FUJITA Osamu, TAKAHASHI Junya, JASMA : Journal of the Japan Society of Microgravity Application, 18, 20, 20, 01 Oct. 2001
English

619 The Effect of Gas-Phase Radiation Absorption on Flame Propagation Phenomenon
MORI Takemi, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2001, 41, 126, 127, 25 Sep. 2001
Gas-phase absorption of radiation was experimentally investigated. CO_2 laser beam (λ=10.6μm) was penetrated through a longitudinal combustion chamber (vacuum or filled with air or CO_2 gas), and then the laser absorption and temperature change in the vessel were measured It was found that CO_2 gas can absorb the radiation to increase the temperature. Furthermore, flame propagation experiment was carried out. CH_4/O_2/CO_2 premixed flame with external radiation was observed., The Japan Society of Mechanical Engineers, Japanese

708 Experimental Study on Radiative Ignition of Filter Paper with Visible Light under Microgravity
Takahashi Junya, Sugawara Akifumi, Fujita Osamu, Ito Kenichi, 北海道支部講演会講演概要集, 2001, 41, 240, 241, 25 Sep. 2001
An experiment on radiative ignition of solid fuel has been performed in microgravity to determine the events occurring in the ignition processes in a quiescent field. Filter paper was irradiated by Diode laser (800.1nm) in various oxygen concentrations (0-50%). Using the Diode laser makes it possible to observe the radiative ignition without the effect of gas phase absorption. The ignition delay was measured for various experimental conditions. The density change of gas phase before ignition were observed by a Mach-Zehnder interferometer. The results showed that heat conduction from the sample surface induced weak chemical reaction in the vicinity of the sample surface, which propagated outward to reach strong combustion. Ignition delay time decreased with increase in O_2 concentration because mixture near the sample surface might contain more oxygen with higher oxygen atmosphere to cause immediate transition from the weak chemical reaction to the strong combustion., The Japan Society of Mechanical Engineers, Japanese

627 The Formation of N_2O in the Catalytic Purification of the DME Combustion Exhaust Gas
OHMURA Hideaki, FUJISAWA Kazuki, FUJITA Osamu, ITO Kenichi, 北海道支部講演会講演概要集, 2001, 41, 142, 143, 25 Sep. 2001
The formation of N_2O in the catalytic purification of simulated DME engine exhaust gas is investigated. Main parameters are catalytic reactor temperature and NO inlet concentration. The results show that there is a possibility of the considerable N_2O formation in the process of catalytic NO reduction. The amount of N_2O formation changes with NO concentration in the simulated exhaust gas, and then shows the maximum value as a function of catalyst temperature. Therefore, N_2O formation characteristic during NOx reduction is very important factor in the performance evaluation of the NOx catalyst for DME engine exhaust gas., The Japan Society of Mechanical Engineers, Japanese

706 Combustion Behavior of Paper Sheet in a Low External Flow under Microgravity : Discussion based on Temperature Measurement
NISHIZAWA Katsuhiro, FUJITA Osamu, ITO Kenichi, OLSON Sandra L., KASHIWAGI Takashi, 北海道支部講演会講演概要集, 2001, 41, 236, 237, 25 Sep. 2001
Flame spreading over thin paper in low external air flow has been performed in microgravity. Two ignition methods, kanthal wire heater and CO_2 laser, were examined. The flame spread rates were measured under various oxygen concentrations and external flow velocity. The result showed that external flow velocity had a strong effect on flame spread rates. Temperature distributions indicated that pyrolysis temperature increased and the preheating length decreased with increasing air flow velocity. There are no particular differences in surface temperature distribution between 2D and 3D flames., The Japan Society of Mechanical Engineers, Japanese

629 Flame Stability of Premixed Type Kerosene Foam Burner
TAKADA Masaru, WATANABE Daisuke, FUJITA Osamu, YAMANE Kiyotaka, ITO Kenichi, ANZAWA Norio, 北海道支部講演会講演概要集, 2001, 41, 146, 147, 25 Sep. 2001
This paper represents the research of a premixed type kerosene foam burner. This burner can attain a low excess air ratio premixed combustion even with liquid fuel. Experiments were carried out with changing the combustion load and the excess air ratio. This burner can realize the stable premixed combustion in given conditions with respect to combustion load and excess air ratio. To consider about the flame stability in the burner, the numerical simulation using the heat circulation model was attempted. The result shows that the flame stability of the burner depends on the heat circulation, especially the feedback heat from flame to the porous plate., The Japan Society of Mechanical Engineers, Japanese

Importance of Ground-Based Microgravity Experiments with Drop Shafts for Combustion Research
FUJITA Osamu, JASMA, 18, 3, 156, 161, 31 Jul. 2001
日本マイクログラビティ応用学会, Japanese

微小重力場における拡散火炎中のすす粒子凝集挙動
伊藤 献一, 藤田 修, 燃焼研究, 125, 21, 31, 18 Jul. 2001
日本燃焼学会事務局, Japanese

303 Observation of Flame Spread Over Wire Insulation in Slow External Flow under Microgravity
NISHIZAWA Katsuhiro, FUJITA Osamu, ITO Kenichi, TAKESHITA Yasuhiro, 東海支部地区講演会講演論文集, 2001, 72, 73, 2001
日本機械学会東海支部, Japanese

Observation of Spherical Fuel Combustion within a Low External Flow under Microgravity
FUJITA Osamu, INOUE Yoriaki, ITO Kenichi, TAKESHITA Yasuhiro, JASMA : Journal of the Japan Society of Microgravity Application, 17, 7, 8, 01 Oct. 2000
English

518 Effect of External Flow Velocity on Flame Spread over Wire Insulation in Microgravity
NISHIZAWA Katsuhiro, FUJITA Osamu, ITO Kenichi, KIKUCHI Masao, OLSON Sandra L., TAKESHITA Yasuhiro, 北海道支部講演会講演概要集, 2000, 40, 216, 217, 25 Sep. 2000
Microgravity combustion experiments were conducted to acquire data on the effect of external flow velocity on combustion phenomena of solid material. Polyethylene insulated wire were used as a test sample. The flame spread rates were measured under various oxygen concentrations, external flow velocity and dilution gases. The result showed that external flow velocity had a weak effect for flame spread rates with polyethylene sample under all O_2 concentrations., The Japan Society of Mechanical Engineers, Japanese

505 Combustion of high boiling point fuel in a low external air flow
INOUE Yoriaki, FUJITA Osamu, ITO Kenichi, TAKESHITA Yasuhiro, 北海道支部講演会講演概要集, 2000, 40, 190, 191, 25 Sep. 2000
Combustion of high boiling point fuel in a slow air flow was investigated under microgravity. Air flow velocity was varied from 4.1cm/sec to 15.8cm/sec, then flame shape varied from spherical to spindle shape. Density of soot formed in a flame decreased with an increase of relative velocity. According to the laser shadow image, down wind soot distribution with slow external flow showed a maximum density at a certain distance from the sample and then, rapidly decreased around rear edge of the flame., The Japan Society of Mechanical Engineers, Japanese

504 Observation of soot formation in a laminar diffusion flame sustained above a flat plate under microgravity
TAKAMOTO Yoshiteru, FUJITA Osamu, ITO Kenichi, SAKURAYA Takashi, 北海道支部講演会講演概要集, 2000, 40, 188, 189, 25 Sep. 2000
Soot formation in a boundary layer type laminar diffusion flame sustained above a flat plate under microgravity is studied. The main parameters are gas temperature, oxygen mass fraction, and gas flow velocity. The effects of these parameters on the position and strength of soot formation are observed with optical method. The results showed that higher temperature and O_2 concentration increased the soot formation. The flow velocity strongly affected the position of soot formation., The Japan Society of Mechanical Engineers, Japanese

Combustion Characteristics of Propellants for End-burning Hybrid Rockets
NAGATA Harunori, HASHIMOTO Nozomu, KATO Takahiro, FUJITA Osamu, ITO Kenichi, KUDO Isao, AKIBA Ryojiro, JASMA, 17, 3, 172, 177, 31 Jul. 2000
日本マイクログラビティ応用学会, Japanese

B112 Mechanism of Flame Spreading over Polystyrene Bead Array in Microgravity(Solid combustion/incinerator) :
Fujita Osamu, Ito Kenichi, Takahashi Junya, Proceedings of the ... JSME-KSME Thermal Engineering Conference, 1, "1, 163"-"1-168", 2000
Flame spreading over polystyrene beads arranged in line have been investigated under microgravity as a simulation of flame propagation phenomena of particle cloud combustion. Some experimental parameters, such as O_2 concentration, particle spacing, pressure, and inert gas type, have been examined to know their effect on the flame spreading characteristics. Further, the temperature distribution ahead of the propagating flame front have been estimated by the Mach-Zehnder interferometry. Based on these results the mechanism of flame spreading over fuel particle array has been discussed. The results showed that the importance of relative position between flame front and unburned fuel particle next to the flame front. When the particle is farther than the flame radius, thermal diffusion process has a strong effect on the flame spread rate, while its effect is not so dominant when the flame radius is larger than the particle spacing. The importance of the radiation reabsoption phenomena was also pointed out based on the interferometry results., 日本機械学会, English

B110 EFFECTS OF COAL PARTICLES SEEDING ON BURNING VELOCITY OF METHANE-AIR MIXTURES(Droplet/particle combustion-2) :
NAGATA Harunori, FUJITA Osamu, ITO Kenichi, KUDO Isao, TAKESHITA Yasuhiro, Proceedings of the ... JSME-KSME Thermal Engineering Conference, 1, "1, 151"-"1-155", 2000
This paper describes experimental and numerical studies about effects of coal particles seeding on flame propagation velocity and burning velocity of lean methane-air mixtures. To produce uniform coal dust clouds and to eliminate the buoyancy effect, experiments are carried out under microgravity environment, being obtained with the 500-m drop shaft of Japan Microgravity Center (JAMIC). Experimental and numerical results reveal that seeding of an appropriate amount of coal particles increases flame propagation velocity. In spite of this, the increase of burning velocity is almost zero or very small. Accordingly, the main cause of the enhancement of flame propagation velocity is the gas expansion due to coal combustion behind the methane-air flame. This is because coal combustion is nearly isolated from methane combustion in conditions investigated in this study., 日本機械学会, English

Observation of Flame Spread Phenomena Over Wire Insulation Material in Microgravity-Effect of Surrounding Gas component and Sample Geometry-
FUJITA Osamu, KIKUCHI Masao, ITO Kenichi, JASMA : Journal of the Japan Society of Microgravity Application, 16, 63, 64, 01 Oct. 1999
English

Removal of Unburned Species in Simulated Methanol Engine Exhaust Gas with NO_x Purification Catalyst
FUJITA Osamu, ALAM Mahabubul, ITO Kenichi, Transactions of the Japan Society of Mechanical Engineers. Series B., 65, 634, 2165, 2171, 25 Jun. 1999
Characteristics of methanol reduction and formaldehyde formation with NO_x purification catalyst (NO_x catalyst) have been investigated to know the applicability of NO_x catalyst to lean burn or diesel type methanol engine. The catalysts used in this research were Co-γAl_2O_3 and Sn-Al_2O_3 as examples of NO_x catalysts and Pt-Al_2O_3 as an oxidation catalyst to be compared with NO_x catalyst. Pure γAl_2O_3 was also used additionally. Laboratory experiments were conducted by using above catalysts in oxygen rich atmosphere considering lean burn methanol engines or diesel type methanol engines. Reaction temperature and presenting NO concentration were selected as experimental parameters. The experimental results showed that methanol reduction temperature with NO_x catalyst became around 150℃ higher than that with oxidation catalyst and it became closer to engine exhaust gas temperature level. Large amount of formaldehyde was formed during the use of NO_x catalyst at a certain temperature range. The formation temperature range is higher than that with Pt catalyst, which may cause higher formaldehyde formation in the engine exhaust gas. Effect of NO on methanol oxidation and formaldehyde formation characteristics with NO_x catalyst was significant as was observed in oxidation catalysts. With increase in NO, methanol reduction rate became lower and the amount of formaldehyde formation increased., The Japan Society of Mechanical Engineers, Japanese

Combustion Behavior of Polyethylene Insulated Wires under Microgravity
KIKUCHI Masao, FUIJTA Osamu, ITO Kenichi, SAKURAYA Takashi, JASMA, 16, 2, 119, 128, 20 May 1999
日本マイクログラビティ応用学会, Japanese

Flame Spread over Wire Insulation under Microgravity
FUJITA Osamu, KIKUCHI Masao, ITO Kenichi, SATO Atsuki, SAKURAYA Takashi, Transactions of the Japan Society of Mechanical Engineers. Series B., 65, 632, 1473, 1478, 25 Apr. 1999
An experimental study of flame spread phenomena over ETFE (Ethylene-Tetrafluoroethylene) insulated wire was performed under microgravity to obtain fundamental data on fire safety in space. The effects of the parameters thought dominant for wire combustion in fires-the ambient oxygen concentration, wire initial temperature, T_i, and wire diameter, d_ω,- were investigated in the microgravity experiments. A series of comparative experiments were also conducted at normal gravity. Flame shape under microgravity changed depending on the state of the molten fuel accumulation. Experimental results showed that there existed a possibility of higher flame spread rates under microgravity than at normal gravity, in spite of lower flame temperature in microgravity. Wire initial temperature, T_i, had a very large influence both on flame spread rates and extinction limit of the wire under microgravity. The degree of flame spread rate decreased with increase in d_ω and, correspondingly, the increase with decrease in d_ω under microgravity was higher than at normal gravity., The Japan Society of Mechanical Engineers, Japanese

On the Colors of Laminar Flames
Tatsuta Setsuo, Fujita Osamu, Ito Kenichi, 旭川工業高等専門学校研究報文, 36, 11, 19, 1999
Asahikawa National College of Technology, English

Determination of soot volume fraction in microgravity diffusion flames based on soot visualization technique
HAMADA Makoto, FUJITA Osamu, ITO Kenichi, SAKURAYA Takashi, JASMA : Journal of the Japan Society of Microgravity Application, 15, 65, 66, 01 Oct. 1998
English

Soot Agglomeration in a Boundary-layer Type Diffusion Flame under Microgravity
IGUCHI Akinori, FUJITA Osamu, ITO Ken'ichi, TAKESHITA Yasuhiro, JASMA : Journal of the Japan Society of Microgravity Application, 15, 67, 68, 01 Oct. 1998
English

Visualization and size measurement of soot agglomerates in microgravity diffusion flames
ITO Kenichi, FUJITA Osamu, TAKEUCHI Atsushi, HAMADA Makoto, SAKURAYA Takashi, JASMA : Journal of the Japan Society of Microgravity Application, 14, 45, 46, 01 Oct. 1997
English

Kashiwagi, T., Mell, W. E, McGrattan, T., Baum, H. R., Olson, S. L., Fujita, O., Kikuchi, M. and Ito, K. : "Ignition, Transition, Proc. Flame Spread in Multidimensional Configurations in Microgravity", NASA Conference Publication 10194(Proceeding of Th・・・　　　　　　　　　　　　　　　
1997
Kashiwagi, T., Mell, W. E, McGrattan, T., Baum, H. R., Olson, S. L., Fujita, O., Kikuchi, M. and Ito, K. : "Ignition, Transition, Proc. Flame Spread in Multidimensional Configurations in Microgravity", NASA Conference Publication 10194(Proceeding of The Fourth International Microgravity Combustion Workshop), 441-416 (1997)

Use of Microgravity Environment to Investigate the Effect of Magnetic Field on Flame Shape　　　　　　　　　　　　　　　
O. Fujita, Y. Kuroda, K. Ito, N. I. Wakayama, Y. Takeshita, Proceedings of the 20th International Symposium on Space Technology and Science, 946, 951, 1996
English, Summary international conference

Measurement of Flame Propagation Rate in a Pulverized Coal Cloud
MASUKO Katsumi, SATO Jun'ichi, KITANO Kunihiro, ITO Ken'ichi, FUJITA Osamu, SAKAMOTO Hiroaki, JASMA : Journal of the Japan Society of Microgravity Application, 12, 4, 319, 320, 31 Oct. 1995
English

A study on flame propagation of polystyrene foam beads under microgravity for simulation of particle cloud combustion
FUJITA Osamu, ITO Kenichi, NAKAMURA Keiichi, JASMA : Journal of the Japan Society of Microgravity Application, 12, 4, 323, 324, 31 Oct. 1995
English

OBSERVATION OF MICROGRAVITY DIFFUSION FLAMES WITHIN A MAGNETIC FIELD
FUJITA Osamu, KURODA Yukio, ITO Kenichi, WAKAYAMA Nobuko I., TAKESHITA Yasuhiro, The Journal of space technology and science : a publication of Japanese Rocket Society, 11, 2, 18, 27, 01 Sep. 1995
English

Characteristics of Catalytic Combustion Using Butane Premixed Gas
Kudo Hitoshi, Fujita Osamu, Ito Kenichi, Research reports, Kushiro Technical College, 26, 23, 32, 18 Dec. 1992
Kushiro National College of Technology, Japanese

Characteristics of Catalytic Combustion Using Butane Premixed Gas (Effect of Operating Conditions on Steady-State Characteristics)
Kudoh Hitoshi, Fujita Osamu, Ito Ken'ichi, Research reports, Kushiro Technical College, 25, 33, 41, 20 Dec. 1991
Kushiro National College of Technology, Japanese

Characteristics of Catalytic Combustion Using Butane Premixed Gas
伊藤 献一, 藤田 修, 工藤 均, Bulletin of the Faculty of Engineering,Hokkaido University, 155, p41, 49, May 1991
北海道大学 = Hokkaido University, Japanese

Catalytic Combustion of Lean Methanol Mixture
伊藤 献一, 藤田 修, 岩井 保憲, 崔 炳喆, 山根 清隆, Bulletin of the Faculty of Engineering,Hokkaido University, 140, p73, 81, May 1988
北海道大学 = Hokkaido University, Japanese

Effect of conductor on spreading flames over wire in microgravity
Shuhei Takahashi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita, 43rd International Conference on Environmental Systems
Tests with flames spreading over wires in microgravity were performed with applying power to the inner core wire to examine the influence of inner core heating on the flame spread rate and extinction limit. In the experiments, low density polyethylene insulated Nickel-chrome wire was used as a sample. The experiments were conducted both in normal gravity and microgravity attained by parabolic flights in external opposed flow conditions from 50 to 250 mm/s. The experimental results indicated that flame spread rate becomes about 1.5 times faster with applying 12.4 W/m to the inner core than without applying power. One of the reasons of this result is the decrease of required heat for pyrolysis due to the preheated insulation. Further, increase of heat input from flame to the insulation also might have enhanced flame spread. The flammability tests in 1g indicated that the limiting value of the oxygen concentration decreased with the increase of applying power to the inner core: flame became more flammable by applying power to the inner core. Further, the limiting value of the oxygen concentration decreased in μg at every applying power condition at 150 mm/s flow velocity condition. T

燃焼現象の基礎　　　　　　　　　　　　　　　
オーム社, 2001

環境圏の新しい燃焼工学　　　　　　　　　　　　　　　
フジテクノシステム, 1999

Use of Microgravity for Understanding Combustion Phenomena (Plenary lecture)
Osamu Fujita
The 61st Symposium (Japanese) on Combustion, 15 Nov. 2023, Combustion Society of Japan, Japanese, Invited oral presentation
15 Nov. 2023 - 17 Nov. 2023, Akita city, Japan, [Invited], [Domestic Conference]

Introduction of Combustion Research Project "FLARE" utilizing ISS/KIBO for Fire Safety Standard in the Next Generation　　　　　　　　　　　　　　　
FUJITA Osamu
6th International Symposium on Physical Science in space, 16 Sep. 2015, English, Keynote oral presentation
[Invited], [International presentation]

INTERACTION BETWEEN ACOUSTIC VIBRATION AND PROPAGATING FLAMES DEFORMED BY EXTERNAL LASER IRRADIATION IN A COMBUSTION TUBE　　　　　　　　　　　　　　　
Osamu Fujita, Yoshikazu Taniyama
The 5th East Asia Mechanical and Aerospace Engineering Workshop, 28 May 2015, English, Keynote oral presentation
[Invited], [International presentation]

Impact of Gravity on Wire Insulation Combustion　　　　　　　　　　　　　　　
FUJITA Osamu
Asian Microgravity Symposium 2014, 30 Oct. 2014, English, Keynote oral presentation
[Invited], [International presentation]

Solid Combustion Research in Microgravity as a Base of Fire Safety in Space
FUJITA Osamu
35th International Symposium on Combustion, 06 Aug. 2014, English, Invited oral presentation
[Invited], [International presentation]

Impact of Gravitational Field on Flammability of Solid Material　　　　　　　　　　　　　　　
FUJITA Osamu
8th Asia-Pacific Conference on Combustion, 12 Dec. 2010, English, Invited oral presentation
[Invited], [International presentation]

50m級微小重力実験設備の設置　　　　　　　　　　　　　　　
2006

Construction of New 50m dorp tower for microgravity experiments　　　　　　　　　　　　　　　
2006

Quantitative estimation of onset condition for combustion insatiability of NH3 premixed flame in a combustion tube
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
Apr. 2022 - Mar. 2025
Osamu Fujita, Nozomu Hashimoto
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22H01408

微小重力場における可燃性複合材料の燃焼と燃え拡がりの物理
科学研究費助成事業
18 Nov. 2021 - 31 Mar. 2024
藤田 修, WANG QIANG
日本学術振興会, 特別研究員奨励費, 北海道大学, 21F21343

Fire physics of spreading flame over multi-layer flammable material in microgravity
Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows
Jul. 2022 - Mar. 2024
Osamu Fujita, Wang Qiang
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 22F21343

Study on coupling mechanism of acoustic vibration and propagating premixed flame by using laser irradiation method
KAKENHI KIBAN (A)
Apr. 2018 - Mar. 2023
FUJITA Osamu
本年度は、再生可能エネルギー由来の燃料として期待されるNH3に重点を置いた研究を進め、以下の３つの項目について成果を得た。
(1)管内伝播火炎の燃焼振動発生におよぼす代替燃料の混入割合の影響：再生可能エネルギー由来の燃料として期待されるNH3を選択し、その代替率と不安定性が発現する限界条件の関係を実験的に取得した。この結果、混合燃料（NH3とCH4の混合）中のNH3比率に対する不安定性の変化を特定の当量比について取得し、NH3の混合割合が増加すると燃焼振動の発生限界が拡大することを示した。また、この結果について考察を行い、NH3による燃料代替率が上昇するとルイス数が低下することが大きな影響を与えている可能性を指摘した。また、NH3を混入すると伝播管内で不安定性の増幅する火炎位置が変化するという結果が得られており、Pressure Couplingの不安定性への寄与を考慮する必要性を示した。
(2)平面火炎の圧力変動に対する不安定現象発現時の火炎構造の観察：従来から炭化水素燃料を対象として行ってきた、平面火炎に現れるParametric Instability発生時の詳細構造をNH3火炎を対象として観察し、炭化水素を燃料とした場合と比較を行った。この結果、火炎面に現れるセル構造の波数や発光強度の時間変化は両者で異なり、反応過程で生じる中間生成物（H2や活性化学種）を含めた拡散係数を考慮した不安定性の議論が必要であることを示した。
(3)変形を与えた火炎の不安定性の観察：これまでの研究で確立してきたレーザ照射法により、変形させた火炎の圧力変動の増幅率や不安定性の発生限界をNH3/C2H4混合燃料に対して調べた。この結果、火炎変形はNH3混合燃料の場合でも圧力増幅率を増加させ、Velocity couplingは依然として燃焼振動を発生させる重要な機構の一つであることが示された。また、純粋な炭化水素燃料と比較すると(1)でも述べたとおりNH3の混入が不安定性を増加させるという結果が得られた。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Principal investigator, Competitive research funding, 18H03755

Clarification and model development for the interaction mechanism of solid fuels and gaseous fuels during the mixing-combustion
Grants-in-Aid for Scientific Research
01 Apr. 2019 - 31 Mar. 2022
Hashimoto Nozomu
In this study, the detailed flame structure and the interaction between the gaseous fuel and the solid particle cloud for the co-combustion field of the gaseous fuel and the solid particle cloud were clarified. For the co-combustion of gaseous fuel / solid particle cloud, it was clarified that there are two interaction effects, namely, (1) the heat absorption effect of solid particles, and (2) the equivalence ratio increase effect by the evolution of volatile matter from solid particles, in the pre-heat zone of the flame. The outcome of this study is expected to contribute for the introduction of carbon-free energy carrier gas and operation of various high temperature processes using solid fuel.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02073

レーザ加熱火炎面曲率制御法によるＧＴ燃焼器の不安定振動燃焼トリガー機構の研究　　　　　　　　　　　　　　　
科学研究費補助金基盤研究（Ｂ）
Mar. 2014 - Mar. 2018
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

Modeling
Grants-in-Aid for Scientific Research
01 Apr. 2015 - 31 Mar. 2017
Hashimoto Nozomu, WATANABE Hiroaki, KUROSE Ryoichi, FUJITA Osamu, TAKAHASHI Hiroyasu
A model that can reproduce the phenomena of soot formation from the volatile matter evolved from solid particles for the unsteady numerical simulation of solid combustion field has been developed. 13 species including tar are postulated as volatile matter. The model can take into account the effect of particle heating rate on the amount of volatile matter and its evolution rate. The large eddy simulation of the 4 kW coal combustion filed with the developed model was conducted. As a result, the tendency of the soot volume fraction distribution predicted by the numerical simulation was consistent with that obtained by the optical measurement. The high accuracy of the developed model was validated by the comparison.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 15K17992

Development of new combustion method of densified solid biomass fuel
Grants-in-Aid for Scientific Research
01 Apr. 2014 - 31 Mar. 2017
Ito Hiroyuki, FUJITA OSAMU
A possibility of the new combustion method in which combustion region is formed at one end of a columnar briquette and propagates one dimensionally was investigated. As a result of the combustion experiments in the case with cylindrical briquette, it was confirmed that there is a condition in which the mass loss rate is almost constant. In the condition, it was observed that the flames are formed around the outer periphery at the lower part of the briquette and above the top end, and the long char combustion region was formed above the flame formed around the briquette. In the case of 1100 and 1300 kg/m3 briquette density, both the mass loss rate and the combustion efficiency decreased with high and low air flow rate and, therefore, they have a peak at moderate air flow rate.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Kanagawa University, 26420160

Soot generation map for Oxy-Fuel combustion and its extenstion method　　　　　　　　　　　　　　　
Grant-in-Aid for Scientific Research
Apr. 2015 - Mar. 2017
FUJITA Osamu
Japan Society for the Promotion of Science, Principal investigator, Competitive research funding

固体材料の微小重力場における着火・消炎およびすす生成挙動に関する研究
科学研究費助成事業
01 Apr. 2012 - 31 Mar. 2015
藤田 修, HU Longhua
本研究においては、研究計画に沿って、以下の２項目について実施した。
1. 固体材料表面を燃え広がる火炎の燃え広がり速度におよぼす試料傾きの影響
実験用試料として、ポリエチレン被覆の電線を選定し、この燃え広がり速度に及ぼす角度の影響（水平からの傾きの角度：-90度～+90度）を調べた。電線の心線材質としては通常の銅の他にニクロム心線を用いた。また、実験変数として雰囲気圧力を変化させた。この結果、電線上火炎燃え広がり速度は、銅心線の場合角度が0度（水平）の場合が最も燃え広がり速度が小さくなり、角度が正、負のいずれに傾いても（すなわち、自然対流が同軸流、対向流のいずれも場合でも）燃え広がり速度は増大することがわかった。一方、心線がニクロムとなった場合は、試料の傾きが正の角度（対向流）が負の角度（同軸流）へ変化すると燃え広がり速度は単調減少することがわかった。これらのことが生じる要因を、新たに構築した熱循環モデルに基づき検討し、実験結果を良く再現できることを明らかにした。これらの結果は、Proc.Combustion Instituteにて公表されている。
２．燃え広がり火炎の消炎限界に対する試料傾きの影響
上記の実験に引き続いて、電線上燃え広がり火炎の消炎限界酸素濃度（LOC)に対する試料傾きの影響を調べた。この結果静止雰囲気においては、LOCは、試料が水平の時最も大きな値を示しそれよりいずれの方向に傾いても低下するという興味深い結果が得られた。さらに、周囲に流動を与えた場合は、試料周囲に生じる自然対流の電線に沿う速度成分と対向周囲流速がちょうど釣り合うような条件の時に、LOCが極大になることを実験的に初めて示した。この結果は、Asian Microgravity SymposiumのKey Note Speechとして発表している。


日本学術振興会, 特別研究員奨励費, 北海道大学, 12F02360

レーザ加熱法を用いた火炎面曲率制御によるFlame Dynamicsの研究　　　　　　　　　　　　　　　
科学研究費補助金基盤研究（Ｂ）
Apr. 2009 - Mar. 2013
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

Study on seslective synthesis of alternative chemical materials originated from biomass by using non-equilibrium plasma
Grants-in-Aid for Scientific Research
2011 - 2013
ITO HIROYUKI, FUJITA Osamu
By heating solid biomass such as wood and waste, liquid fuel and chemical materials, alternative of the fossil fuel, can be obtained because it generates liquid tar via pyrolysis reaction. However, it is difficult to control the composition of liquid tar by giving only heat so far. In this study, gas is dissociated electrolytically to the electrons which has high energy and ions (called non-equilibrium plasma) by adding the energy. The objective of the study is to confirm whether non-equilibrium plasma can change the product yield and composition or not.
Cellulose, one of major components of wood, was used as a biomass material. The change in gas and liquid tar composition was researched by applying argon or hydrogen plasma. The promotion of cellulose pyrolysis in lower temperature region was suggested with argon plasma.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), 23603001

バイオ原料由来高密度固体燃料の定常端面燃焼の研究
科学研究費補助金 挑戦的萌芽研究
Apr. 2010 - Mar. 2012
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

Elucidation of the enhancement mechanism of carbon nanotube growth by combustion plasma
Grants-in-Aid for Scientific Research
2008 - 2010
ITO Hiroyuki, FUJITA Osamu
Combustion synthesis of carbon nanotube (CNT), in which thermal plasma is coexist with heat and carbon sources, is expected to make the mass production of CNT with low cost possible. It has been found that the CNT growth in this method is promoted by applying the direct current electric field. In this study, the effect of electric field on the change in temperature, concentration of chemical species of the CNT formation field, the amount and characteristics of the CNT formed are investigated. The effect of electric field on the CNT growth in the electric furnace is also investigated. As a result, the promotion of CNT growth and improvement of crystallization of CNT are observed in the combustion synthesis. It is suggested that the effect of electric field on the CNT manufacturing in the combustion synthesis can be ascribed to the increase in collection of CNT formed due to the motion of thermal plasma and the promotion of catalytic activity.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 20560176

レーザー加熱法を用いた火炎面曲率制御による火炎不安定現象の研究
科学研究費補助金基盤研究（Ｂ）
Apr. 2006 - Mar. 2009
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

微小重力燃焼研究に基づく地下空間火災安全に関する基礎研究　　　　　　　　　　　　　　　
科学研究費補助金基盤研究（Ｃ）
Apr. 2004 - Mar. 2005
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

微小重力環境を利用した浮遊微小粒子群の火炎伝播および熱輸送特性　　　　　　　　　　　　　　　
科学研究費補助金基盤研究（Ｃ）
Apr. 1995 - Mar. 1997
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

DME/メタノール混合燃料のエンジン適合性と環境負荷低減に関する燃焼学的検討
科学研究費助成事業
1996 - 1997
伊藤 献一, 森川 多津子, 藤田 修
近年その製法が確立され新たな代替燃料として期待されるDME(ジメチルエーテル)のディーゼルエンジンへの適用の可能性を知る上での基礎的データとしてその触媒反応性について検討を行った。
前年度までの研究で、DME単体(ニート)あるいはDME/メタノール混合燃料を自動車用燃料として使用した場合を想定し、これらを燃料とする排ガスの触媒浄化に関する基礎的データを得てきた。とくに、NOx還元触媒(Co-γAl203やSn-γAl203)を利用し、酸素共存下での、これらの燃料成分やNOxの浄化特性について検討してきた。
本年度は、新たに触媒として市販のリーンエンジン排ガス用触媒を用い、同様な実験を行った。この結果、DMEは100°C付近で浄化が開始し300°C以上ではほぼ100%近い浄化率を示した。ただし、この浄化率は排ガス中のNOx濃度に強く影響をうけ、NOxが250ppm程度共存すると、反応温度は100°CC以上高くなる。これとあわ、NOxが共存すると、反応過程でホルムアルデヒドの生成される可能性が示された。一方、NOxはかなり低温度条件から濃度低下が観察され、触媒への吸着作用の強いことがわかった。これらの実験結果から、すでに実用化の実績のある触媒で、ある程度DME排ガス浄化が可能であることが示された。このことは、DMEをジ-ゼル代替燃料として使用した場合、すすの発生がほとんどないことを考えあわせると、その排気を触媒との組み合わせで、十分浄化できる可能性のあることを示している。
このほか、昨年からの使用しているNOx触媒あるいは酸化触媒(Pt-γAl203)を用いて、エンジン始動時等を想定した非定常実験も行い、触媒非定常作動特性に対し、触媒での吸着離脱現象が重要な役割を果たすことが示された。
日本学術振興会, 基盤研究(B), 北海道大学, 08455097

微小重力燃焼における機能性カーボン粒子の生成と構造　　　　　　　　　　　　　　　
科学研究費奨励研究（Ａ）
Apr. 1993 - Mar. 1994
藤田 修
日本学術振興会, Principal investigator, Competitive research funding

Combustion of solid material under microgravity -In case of porous material-
Grants-in-Aid for Scientific Research
1992 - 1994
ITO Kenichi, TAZUMI Masahiro, FUJITA Osamu
Natural convection caused by gravity field makes the combustion phenomena complicated. Since solid combustion is constituted by many physical processes, microgravity field is quite helpful to study its combustion processes through the elimination of natural convection.
In the first year of this project microgravity experimental technique have been developed by using three types of drop tower, 5m, 50m and 500m drop towers. The flame propagation speed of cotton strings and paper sheet has been successfully measured.
In the second year, the effect of various parameters, such as oxygen concentration, and dimension of test pieces have been investigated. The smaller amount of required oxygen, the higher propagation velocity. The higher oxygen concentration also gave the higher propagation velocity. The matrix of paper sheet, simulation of porous material, has also burned to examined the effect of pore size inside of the material, ventilation availability and oxygen concentration. Under microgravity these parameters except oxygen concentration did not affect to the flame propagation speed while they had strong effect under normal gravity. This is because these parameters have effect on the combustion through the change of natural convection strength inside the material.
In the final year, the combustion of polystirene foam beads, which is made from a single chemical component have been investigated to hnow the dominant factors of porous material combustion. The results showed that flame spread phenomena of solid material is mainly dominated by the rates of heat supply to the unburned region and oxygen supply to combustion region. When the former factor, heat supply, is more dominant flame propagation is easier under microgravity because heat is not taken away by natural convection. When the later factor is dominant, flame propagation is faster under normal gravity with aid of natural convection to supply oxygen.
Japan Society for the Promotion of Science, Grant-in-Aid for General Scientific Research (B), Hokkaido University, 04452143

乱流拡散燃焼過程における可視長波長域発光現象と燃焼生成物
科学研究費助成事業
1990 - 1990
伊藤 献一, 田住 正弘, 藤田 修
燃料吹き出しを伴うブラフボディ後流拡散火炎を対象として、せん断層に形成される渦火炎の構造を、可視波長域発光現象および従来からの手法である温度変動、イオン電流変動、シュリ-レン写真撮影、ガス成分濃度分布測結果に基づいて、明らかにした。また、レ-ザ-誘起螢光法により、乱流火炎中のホルムアルデヒド濃度の非接触測定について検討した。これらの結果、以下のような成果が得られた。
(1)せん断層に形成される火炎は明確な渦構造を有し、この構造は組織的かつ連続的にあらわれる。
(2)この渦火炎においては、高温の燃焼ガスが過濃混合気を抱き込むようにしながら層状の渦構造を形成し、燃焼はこの渦内へ向かうような形で進行し最終的には均質な燃焼生成物の塊となる。
(3)この均質化の過程において、渦内での独立した燃焼が進行するために周囲に酸素が存在していても局所的に不完全燃焼が生じることになる。とくに下流域においては、混合気の選択拡散の影響となり過濃燃焼となりやすく、不完全燃焼が生じやすい。これは、酸素過剰な条件における一酸化炭素の生成機構の一つであるとともに、濃淡燃焼によるNOxの抑制につながるものである。
(4)火炎発光現象に基づく画像処理によって上記の濃淡燃焼の状況をとらえることができた。とくに、渦火炎の内部あるいは燃焼場の下流域において火炎の当量比が高くなる傾向にあることが確認できた。
(5)レ-ザ-誘起螢光法により乱流火炎内のホルムアルデヒド濃度分布が測定できる可能性が示された。とくに、燃焼場が混合律速場であるか反応律速場であるかの違いをとらえることが可能であることが示された。
日本学術振興会, 重点領域研究, 北海道大学, 02209201

乱流拡散燃焼過程における可視長波長域発光現象と燃焼生成物
科学研究費助成事業
1989 - 1989
伊藤 献一, 田住 正弘, 藤田 修
本年度は、乱流拡散火炎の可視波長域発光現象の結果として生じる火炎色情報を利用することにより、比較的大規模な二次元渦火炎構造の観察を行った。このために以下に示す項目について検討を行い、同時に行われた成果についても示す。
1.火炎色の定量化
火炎色を定量的に表現することにより、火炎の色情報を燃焼計測のための一情報はとして利用可能とした。具体的には色彩学法に基づいて火炎色をCIE等色関数に基づく色度座標(X,Y,Z)により表現することが可能となった。
2.火炎色と空気比あるいはラジカル濃度分布との関連性の検討
火炎色は、反応帯に存在するラジカルの発光や化学反応の結果として生じるために、ラジカル濃度分布や空気比と関連性をもつことが予想される。この関連性について検討した結果、プロパンを燃料とした場合、色度座標は空気比に対して一意的に変化し火炎色から空気比の予測が可能であることが示された。また、火炎の発光源が限られている場合には火炎中のラジカル発光強度分布を予測できる可能性が示された。
3.火炎色による乱流火炎構造の観察
(1)乱流拡散火炎の基本特性の把握 本年度は、ブラフボディ後流に形成される拡散火炎を対象とし、とくに再循環領域と主流の境界せん断領域に形成される渦火炎に注目した。この構造を高速度シュリ-レン像、温度変動、イオン電流変動により観察しその火炎構造の規則性あるいは火炎の渦構造を明らかにした。
(2)火炎色による乱流火炎構造の観察 上記の火炎を対象とし火炎色による火炎構造の観察を行なった。渦火炎中の空気比分布などの推定を行い、(1)で得られた結果と矛盾のない分布であることが示された。
日本学術振興会, 重点領域研究, 北海道大学, 01627501

乱流拡散燃焼過程における可視長波長域発光現象と燃焼生成物
科学研究費助成事業
1988 - 1988
伊藤 献一, 田住 正弘, 藤田 修
1〕目的: 本研究は火炎の分光スペクトルをもとに、色彩学的取扱いにより火炎色を数量にして表現し、火炎色と燃焼過程の関連性を解明することにある。対象として可視長波長域発光現象を取上げた。
2〕手法: 水素、メタノール、炭火水素の各種火炎を対象とし、(1)分光スペクトルの測定、(2)等色関数を用い、色刺激に相当する三刺激値および刺激和を求める。(3)これらの色度座標を決定する。
3〕知見: 火炎色の数量化手法により、水素火炎およびメタノール火炎にみられる可視長波長域発光現象の解析を行なった。その結果、H┣_<2┫>O分子による700nm域の赤色発光の寄与は少なく、むしろ、燃焼用空気中あるいは燃料中に含まれる微量Naによる線スペクトルと、Co炎バンドによる連続スペクトルとの混色発光が主因であることを明らかにできた。また、炭化水素予混合火炎に対して、火炎色と当量比の関連を色度図上に表すことを試み、当量比土0.01〜0.05の精度で識別が可能であることを見出した。
4〕検討中の事項および今後の課題:(1)火炎色のより詳細な基礎特性の把握 (2)カラー画像処理による火炎色の実時間測定 (3)発光強度を考慮した火炎色の表現 (4)反応機構と火炎色との関連性の解明 (5)工学的応用を含めた火炎色彩学の確立
5〕まとめ:本研究の成果は次のようにまとめられる。
(1)火炎色を色度座標で数値的に表現した。
(2)水素およびメタノール火炎にみられる可視長波長域発光現象には、空気中および燃料中に含まれるNaの熱発光が重要な役割を果している。
(3)火炎色数値比の工学的応用の第一歩として、炭化水素予混合火炎における当量比計測の可能性を示した。
(4)火炎色彩学という新分野を拓くことの可能性が認められた。
日本学術振興会, 重点領域研究, 北海道大学, 63627501

成型固体バイオマス燃料の燃焼装置　　　　　　　　　　　　　　　
Patent right
特願2011-027133

Bachelor's degree program, School of Engineering

Master's degree program, Graduate School of Engineering

Doctoral (PhD) degree program, Graduate School of Engineering