研究者データベース

藤田 修(フジタ オサム)
工学研究院 機械・宇宙航空工学部門 宇宙航空システム
教授

基本情報

所属

  • 工学研究院 機械・宇宙航空工学部門 宇宙航空システム

職名

  • 教授

学位

  • 工学博士(北海道大学)

論文上での記載著者名

  • Osamu Fujita
  • Fujita O.
  • 藤田 修

ホームページURL

J-Global ID

研究キーワード

  • 火災安全   代替燃料   燃焼工学   微小重力   宇宙環境利用   Alternative Fuel   Combustion Science   Microgravity   Space Utilization   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 熱工学
  • フロンティア(航空・船舶) / 航空宇宙工学

職歴

  • 2003年04月 - 現在 北海道大学 大学院工学研究科機械宇宙工学部門 教授
  • 1990年04月 - 2003年03月 北海道大学 工学部機械工学科 助教授
  • 1994年03月 - 1994年12月 University of California at Berkeley Department of Mechanical Engineering Visiting Professor
  • 1987年04月 - 1990年03月 北海道大学 工学部機械工学科 講師
  • 1986年04月 - 1987年03月 日本学術振興会 特別研究員

学歴

  • 1984年04月 - 1987年03月   北海道大学   工学研究科   機械工学専攻博士課程
  • 1982年04月 - 1984年03月   北海道大学 大学院   工学研究院   機械工学専攻修士課程
  • 1978年04月 - 1982年03月   北海道大学   工学部   機械工学科

所属学協会

  • The Combustion Institute   日本火災学会   日本マイクログラビティ応用学会   日本航空宇宙学会   日本ガスタービン学会   自動車技術会   日本燃焼学会   日本機械学会   Japan Association for Fire Science and Engineering   Japan Soceity of Microgravity Application   Gas Turbine Society of Japan   Society of Automotive Engineers of Japan   

研究活動情報

論文

  • Ajit K. Kumar, Yoichiro Koyama, Sung H. Yoon, Nozomu Hashimoto, Osamu Fujita
    Combustion and Flame 216 326 - 337 2020年06月 [査読有り][通常論文]
     
    © 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.
  • Yu Xia, Genya Hashimoto, Nozomu Hashimoto, Khalid Hadi, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
    FUEL 268 117393 1 - 10 Elsevier 2020年05月 [査読有り][通常論文]
     
    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.
  • Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
    Combustion and Flame 213 314 - 321 2020年03月 [査読有り][通常論文]
     
    © 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.
  • Masashi Nagachia, Fumiya Mitsuia, Jean-Marie Citerneb, Hugo Dutilleulb, Augustin Guibaud, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
    Fire Technology 56 1 149 - 168 2020年01月 [査読有り][通常論文]
  • Augustin Guibaud, Jean-Marie Citerne, Jean-Louis Consalvi, Osamu Fujita, Jose Torero, Guillaume Legros
    Fire Technology 56 1 185 - 207 2020年01月 [査読有り][通常論文]
  • Yusuke Konno, Yoshinari Kobayashi, Carlos Fernandez-Pello, Nozomu Hashimoto, Shinji Nakaya, Mitsuhiro Tsue, Osamu Fujita
    Fire Technology 56 1 131 - 148 2020年01月 [査読有り][通常論文]
     
    © 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.
  • Wang Qiang, Hu Longhua, Wang Shaoming, Wang Shuangfeng, Chung Suk Ho, Fujita Osamu
    Combustion and Flame 210 315 - 323 2019年12月 [査読有り][通常論文]
  • Feng Guo, Wataru Hase, Yu Ozaki, Yusuke Konno, Masaya Inatsuki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 109 109858  2019年12月 [査読有り][通常論文]
     
    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.
  • Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
    Combustion and Flame(IF:4.12) 207 63 - 70 2019年09月 [査読有り][通常論文]
  • Ajit K Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita
    Combustion and Flame 205 316 - 326 2019年07月 [査読有り][通常論文]
  • Ryo Ichimura, Khalid Hadi, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
    FUEL(IF:5.128) 246 15 178 - 186 2019年06月 [査読有り][通常論文]
  • Thong D Hong, Osamu Fujita, Tatang H Soerawidjaja, Iman K Reksowardojo
    Renewable Energy(IF:5.439) 136 84 - 90 2019年06月 [査読有り][通常論文]
  • H. Takahashi, N. Hashimoto, H. Watanabe, R. Kurose, O. Fujita
    Proceedings of the Combustion Institute 37 3 2883 - 2891 2019年 [査読有り][通常論文]
     
    © 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.
  • 佐藤賢一, 藤田 修
    日本機械学会論文集 85 876 1 - 12 2019年 [査読有り][通常論文]
  • 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 2019年01月 [査読有り][通常論文]
  • Khalid Hadi, Ryo Ichimura, Nozomu Hashimoto, Osamu Fujita
    Proceedings of the Combustion Institute(IF:3.299) 37 3 2935 - 2942 2019年01月 [査読有り][通常論文]
  • Hui Yan, Osamu Fujita
    Proceedings of the Combustion Institute(IF:3.299) 37 3 4099 - 4106 2019年01月 [査読有り][通常論文]
  • H. Takahashia, N. Hashimotoa, H. Watanabeb, R. Kurosec, O. Fujita
    Proceedings of the Combustion Institute(IF:3.299) 37 3 2883 - 2891 2019年01月 [査読有り][通常論文]
  • 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 2019年01月 [査読有り][通常論文]
  • Ajit KumarDubey, KoyamaYoichiro, HashimotoNozomu, FujitaOsamu
    Proceedings of the Combustion Institute(IF:3.299) 37 2 1869 - 1877 2019年01月 [査読有り][通常論文]
  • Chung Yongho, Osamu Fujita, Nozomu Hashimoto
    Proceedings of the Combustion Institute(IF:3.299) 37 2 1887 - 1894 2019年01月 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
     
    © 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.
  • Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 37 3 3817 - 3824 2019年 [査読有り][通常論文]
     
    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.
  • 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 2019年01月 [査読有り][通常論文]
  • Ningfei Wang, Baolu Shi, Bo Li, Xiaoyao Zhao, Run Chen, Osamu FUJITA
    International Journal of Hydrogen Energy(IF:4.084) 43 31 14806 - 14815 2018年08月 [査読有り][通常論文]
  • 佐藤賢一, 藤田 修
    日本機械学会論文集 84 865 2018年08月 [査読有り][通常論文]
  • 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 2018年06月 [査読有り][通常論文]
  • Ken Mizutani, Kyosuke Miyamoto, Nozomu Hashimoto, Yusuke Konno, Osamu Fujita
    INTERNATIONAL JOURNAL OF MICROGRAVITY SCIENCE AND APPLICATION 35 1 350104-1 - 350104-6 2018年 [査読有り][通常論文]
     
    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.
  • Yoshinari Kobayashi, Yusuke Konno, Xinyan Huang, Shinji Nakaya, Mitsuhiro Tsue, Nozomu Hashimoto, Osamu Fujita, Carlos Fernandez-Pello
    Fire Safety Journal 95 1 - 10 2018年01月 [査読有り][通常論文]
     
    © 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.
  • Sung Hwan Yoon, Longhua Hu, Osamu Fujita
    Combustion and Flame(IF:4.12) 2018年01月 [査読有り][通常論文]
  • Seung J. Lim, Sun H. Park, Jeong Park, Osamu Fujita, Sang I. Keel, Suk H. Chung
    COMBUSTION AND FLAME 185 82 - 92 2017年11月 [査読有り][通常論文]
     
    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.
  • Hui Yan, Osamu Fujita
    FUEL 188 595 - 602 2017年01月 [査読有り][通常論文]
     
    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.
  • 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 2017年 [査読有り][通常論文]
     
    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.
  • Kohei Shimizu, Masao Kikuchi, Nozomu Hashimoto, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 36 2 3063 - 3071 2017年 [査読有り][通常論文]
     
    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.
  • Sung Hwan Yoon, Tae Joon Noh, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 36 1 1603 - 1611 2017年 [査読有り][通常論文]
     
    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.
  • Long H. Duong, Osamu Fujita, Iman K. Reksowardojo, Tatang H. Soerawidjaja, Godlief F. Neonufa
    FUEL 185 1 855 - 862 2016年12月 [査読有り][通常論文]
     
    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.
  • Kyosuke Miyamoto, Xinyan Huang, Nozomu Hashimoto, Osamu Fujita, Carlos Fernandez-Pellob
    FIRE SAFETY JOURNAL 86 32 - 40 2016年11月 [査読有り][通常論文]
     
    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.
  • 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 2016年09月 [査読有り][通常論文]
     
    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.
  • Sung Hwan Yoon, Tae Joon Nob, Osamu Fujita
    COMBUSTION AND FLAME 170 1 - 11 2016年08月 [査読有り][通常論文]
     
    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.
  • 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 2015年04月 [査読有り][通常論文]
     
    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.
  • Seung Jae Lim, Minkuk Kim, Jeong Park, Osamu Fujita, Sukho Chung
    COMBUSTION AND FLAME 162 4 1167 - 1175 2015年04月 [査読有り][通常論文]
     
    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.
  • Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 35 3 2487 - 2502 2015年 [査読有り][通常論文]
     
    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.
  • Takero Nakahara, Hui Yan, Hiroyuki Ito, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 35 3 2415 - 2422 2015年 [査読有り][通常論文]
     
    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.
  • Longhua Hu, Yangshu Zhang, Kosuke Yoshioka, Hirokazu Izumo, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 35 3 2607 - 2614 2015年 [査読有り][通常論文]
     
    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.
  • Andres F. Osorio, Ken Mizutani, Carlos Fernandez-Pello, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 35 3 2683 - 2689 2015年 [査読有り][通常論文]
     
    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.
  • Kira Aguilar, Yoshikazu Taniyama, Hiroyuki Ito, Osamu Fujita
    COMBUSTION SCIENCE AND TECHNOLOGY 186 10-11 1434 - 1446 2014年11月 [査読有り][通常論文]
     
    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.
  • Yoshikazu Taniyama, Osamu Fujita
    COMBUSTION AND FLAME 161 6 1558 - 1565 2014年06月 [査読有り][通常論文]
     
    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.
  • Thong D. Hong, Tatang H. Soerawidjaja, Iman K. Reksowardojo, Osamu Fujita, Zarrah Duniani, Mai X. Pham
    CHEMICAL ENGINEERING AND PROCESSING 74 124 - 130 2013年12月 [査読有り][通常論文]
     
    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.
  • Shuhei Takahashi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita
    COMBUSTION AND FLAME 160 9 1900 - 1902 2013年09月 [査読有り][通常論文]
     
    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.
  • K.Masunaga, H.Ito, O.Fujita
    Asia-Pacific Journal of Chemical Engineering 8 2 246 - 253 2013年03月 [査読有り][通常論文]
  • Tae Hyung Kim, Jeong Park, Osamu Fujita, Oh Boong Kwon, Jong Ho Park
    FUEL 104 739 - 748 2013年02月 [査読有り][通常論文]
     
    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.
  • Yu Jeong Kim, Chang Bo Oh, Osamu Fujita
    ADVANCES IN MECHANICAL ENGINEERING 2013 2013年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • Shuhei Takahashi, Hiroyuki Takeuchi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 34 2 2657 - 2664 2013年 [査読有り][通常論文]
     
    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.
  • Yoshitomo Takano, Osamu Fujita, Naoki Shigeta, Yuji Nakamura, Hiroyuki Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 34 2 2665 - 2673 2013年 [査読有り][通常論文]
     
    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.
  • 伊東弘行, 酒井雄人, 中原毅朗, 井田民男, 藤田 修
    日本スマートプロセス学会誌(高温学会) 1 2 36 - 43 2012年02月 [査読有り][通常論文]
  • 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 78 786 132 - 146 2012年02月 [査読有り][通常論文]
  • 水野 諭, 井田 民男, 渕端 学, 難波 邦彦, 加子坂 篤志, 藤田 修
    日本エネルギー学会誌 91 1 41 - 47 2012年 [査読無し][通常論文]
  • Hiroyuki Ito, Yuto Sakai, Tamio Ida, Yuji Nakamura, Osamu Fujita
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 6 1 111 - 122 2011年 [査読有り][通常論文]
     
    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.
  • M. K. Kim, S. H. Chung, O. Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 33 1 1145 - 1151 2011年 [査読有り][通常論文]
     
    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.
  • June Sung Park, Osamu Fujita, Yuji Nakamura, Hiroyuki Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 33 1 1105 - 1112 2011年 [査読有り][通常論文]
     
    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.
  • Osamu Fujita, Takeshi Kyono, Yasuhiro Kido, Hiroyuki Ito, Yuji Nakamura
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 33 2 2617 - 2623 2011年 [査読有り][通常論文]
     
    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 2011年 [査読有り][通常論文]
     
    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.
  • June Sung Park, Osamu Fujita, Teruaki Honko, Yuichiro Yamada, Hiroyuki Ito, Yuji Nakamura
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 34 8 1290 - 1294 2010年11月 [査読有り][通常論文]
     
    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.
  • 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 2010年05月 [査読有り][通常論文]
  • 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 2010年 [査読有り][通常論文]
  • 藤田 修, 京野 嵩, 城戸 泰裕, 伊東 弘行, 中村 祐二
    JASMA : Journal of the Japan Society of Microgravity Application 26 4 2009年10月19日 [査読無し][通常論文]
  • 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 2009年03月 [査読有り][通常論文]
     
    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.
  • Masakazu Tsuchimoto, Osamu Fujita, Teruaki Honko, Yuji Nakamura, Hiroyuki Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 32 1003 - 1009 2009年 [査読有り][通常論文]
     
    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.
  • Yuji Nakamura, Nobuko Yoshimura, Hiroyuki Ito, Keisuke Azumaya, Osamu Fujita
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 32 2559 - 2566 2009年 [査読有り][通常論文]
     
    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.
  • 阿形 蛍, 大西 陽介, 藤田 修, 中村 祐二, 伊東 弘行, 菊池 政雄
    JASMA : Journal of the Japan Society of Microgravity Application 25 4 2008年10月30日 [査読無し][通常論文]
  • 藤田 修, 京野 嵩, 城戸 泰裕, 中村 祐二, 伊東 弘行
    JASMA : Journal of the Japan Society of Microgravity Application 25 4 2008年10月30日 [査読無し][通常論文]
  • 中村 祐二, 東谷 圭祐, 伊東 弘行, 藤田 修
    可視化情報学会誌. Suppl. = Journal of the Visualization Society of Japan 28 2 153 - 154 2008年09月15日 [査読無し][通常論文]
  • Jae-Hyuk Choi, Osamu Fujita, Takafumi Tsuiki, Junhong Kim, Suk Ho Chung
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 32 8 1484 - 1491 2008年09月 [査読有り][通常論文]
     
    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
    Progress in Scale Modeling 17 - 28 2008年 [査読無し][通常論文]
  • 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年 [査読有り][通常論文]
  • 鈴木 朋子, 岡崎 輝幸, 山本 研二, 仲田 博幸, 藤田 修
    日本機械学会論文集B 74 743 1586 - 1592 2008年 [査読有り][通常論文]
  • 鈴木 朋子, 岡崎 輝幸, 山本 研二, 仲田 博幸, 藤田 修
    日本機械学会論文集B 74 743 1579 - 1585 2008年 [査読有り][通常論文]
  • 日本燃焼学会誌 50 153 264 - 270 2008年 [査読有り][通常論文]
  • 日本燃焼学会誌 50 153 255 - 263 2008年 [査読有り][通常論文]
  • Masakazu Tsuchimoto, Teruaki Honko, Yuji Nakamura, Hiroyuki Ito, Osamu Fujita
    COMBUSTION SCIENCE AND TECHNOLOGY 180 10-11 1803 - 1811 2008年 [査読有り][通常論文]
     
    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.
  • Tomoko Suzuki, Teruyuki Okazaki, Kenji Yamamoto, Hiroyuki Nakata, Osamu Fujita
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 3 3 532 - 539 2008年 [査読有り][通常論文]
     
    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.
  • 小林 雅律, 今井 亮介, 藤田 修
    機械学会論文集B 74 748 2718 - 2723 2008年 [査読有り][通常論文]
  • Yuji Nakamura, Nobuko Yoshimura, Tomohiro Matsumura, Hiroyuki Ito, Osamu Fujita
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 3 3 430 - 441 2008年 [査読有り][通常論文]
     
    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.
  • Tomoko Suzuki, Teruyuki Okazaki, Kenji Yamamoto, Hiroyuki Nakata, Osamu Fujita
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 3 3 523 - 531 2008年 [査読有り][通常論文]
     
    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.
  • 中村 祐二, 吉村 野歩子, 伊東 弘行, 藤田 修, 東谷 圭祐
    可視化情報学会誌. Suppl. 27 2 171 - 172 2007年09月15日 [査読無し][通常論文]
  • 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年 [査読有り][通常論文]
  • 槌本 真和, 興津 彰宏, 藤田 修, 伊東 弘行, 中村 祐二
    日本機械学会論文集 73 727 803 - 808 2007年 [査読有り][通常論文]
  • Byoung-Ho Jeon, Osamu Fujita, Yuji Nakamura, Hiroyuki Ito
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 2 2 281 - 290 2007年 [査読有り][通常論文]
     
    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年 [査読有り][通常論文]
  • Reduced Gravity Devices Based on theYOYO priciple
    Journal of the Japan Society of Microgravity Applications Vol.24 No.3 312 - 315 2007年 [査読有り][通常論文]
  • 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 2007年 [査読有り][通常論文]
     
    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.
  • 藤田 修, エジャルク ジョアン P, 藤井 崇, 中村 祐二, 伊東 弘行
    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 2006年11月30日 [査読無し][通常論文]
  • 田 炳浩, 藤田 修, 伊東 弘行
    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 2006年11月30日 [査読無し][通常論文]
  • J Kim, KN Kim, SH Won, O Fujita, J Takahashi, SH Chung
    COMBUSTION AND FLAME 145 1-2 181 - 193 2006年04月 [査読有り][通常論文]
     
    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.
  • JH Choi, O Fujita, T Tsuiki, JH Kim, SH Chung
    JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING 49 1 167 - 175 2006年02月 [査読有り][通常論文]
     
    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.
  • 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 2006年 [査読有り][通常論文]
     
    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.
  • JH Choi, O Fujita, T Tsuiki, J Kim, SH Chung
    JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING 48 4 839 - 848 2005年11月 [査読有り][通常論文]
     
    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.
  • Y Nakamura, T Kashiwagi, SL Olson, K Nishizawa, O Fujita, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 30 2319 - 2325 2005年 [査読有り][通常論文]
     
    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.
  • J Takahashi, O Fujita, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 30 2311 - 2317 2005年 [査読有り][通常論文]
     
    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.
  • 日本機械学会論文集B Vol.71 No.703(2005-3月号) 226 - 233 2005年 [査読有り][通常論文]
  • Y Nakamura, T Kashiwagi, SL Olson, K Nishizawa, O Fujita, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 30 2319 - 2325 2005年 [査読有り][通常論文]
     
    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.
  • 中村 寛, 中村 孝, 野口 徹, 藤田 修, 今川 吉郎, 井上 利彦
    機械学会論文集(A編) 71 710 1327 - 1332 2005年 [査読有り][通常論文]
  • 藤田 修, 伊東 弘行, 伊藤 献一
    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 2004年11月04日 [査読無し][通常論文]
  • 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 2004年07月 [査読有り][通常論文]
     
    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.
  • M Alam, O Fujita, K Ito
    PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY 218 A2 89 - 95 2004年03月 [査読有り][通常論文]
     
    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.
  • JSME Int. Journal (Ser. A) 47 3 365 - 370 2004年 [査読有り][通常論文]
  • 西澤 勝弘, 藤田 修, 伊藤 献一
    日本機械学会論文集(B編) 70 694 1555 - 1562 2004年 [査読有り][通常論文]
  • 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 2004年 [査読有り][通常論文]
     
    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.
  • 西澤 勝弘, 藤田 修, 伊藤 献一, 菊池 政雄, 柏木 孝
    日本機械学会論文集B 70 692 1043 - 1050 2004年 [査読有り][通常論文]
  • O Fujita, J Takahashi, K Ito
    JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING 46 4 625 - 632 2003年11月 [査読有り][通常論文]
     
    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.
  • J Lee, SH Won, SH Jin, SH Chung, O Fujita, K Ito
    COMBUSTION AND FLAME 134 4 411 - 420 2003年09月 [査読有り][通常論文]
     
    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.
  • SH Won, J Kim, MK Shin, SH Chung, O Fujita, T Mori, JH Choi, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 29 37 - 44 2003年 [査読有り][通常論文]
     
    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.
  • K Prasad, Y Nakamura, SL Olson, O Fujita, K Nishizawa, K Ito, T Kashiwagi
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 29 2553 - 2560 2003年 [査読有り][通常論文]
     
    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.
  • O Fujita, K Nishizawa, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 29 2545 - 2552 2003年 [査読有り][通常論文]
     
    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.
  • 藤田 修, 松永 太, 野呂 貴志, 伊藤 献一
    日本機械学会論文集B編 69 678 490 - 496 2003年 [査読有り][通常論文]
  • 高橋 絢也, 藤田 修, 伊藤 献一
    日本機械学会論文集B編 69 683 1685 - 1691 2003年 [査読有り][通常論文]
  • 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 2003年 [査読有り][通常論文]
     
    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.
  • O Fujita, K Ito
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 26 2-4 305 - 311 2002年06月 [査読有り][通常論文]
     
    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.
  • 藤田 修, 高橋 絢也, 伊藤 献一
    日本機械学会論文集B 68 666 568 - 575 2002年 [査読有り][通常論文]
  • 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 2001年11月 [査読有り][通常論文]
  • SL Olson, T Kashiwagi, O Fujita, M Kikuchi, K Ito
    COMBUSTION AND FLAME 125 1-2 852 - 864 2001年04月 [査読有り][通常論文]
     
    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.
  • 微小重力場における低速空気流中のポリエチレン被覆導線の燃焼挙動
    藤田 修, 西澤 勝弘, 伊藤 献一
    日本マイクログラビティ応用学会誌 18 4 276 - 282 2001年 [査読有り][通常論文]
  • 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 2001年 [査読有り][通常論文]
     
    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.
  • O Fujita, M Kikuchi, K Ito, K Nishizawa
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 28 2905 - 2911 2000年 [査読有り][通常論文]
     
    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.
  • O Fujita, J Takahashi, K Ito
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 28 2761 - 2767 2000年 [査読有り][通常論文]
     
    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.
  • M. Alam, O. Fujita, K. Ito, S.Kajitani, M.Oguma, H.Machida
    SAE paper 1999-01 3599  1999年 [査読有り][通常論文]
  • 立田 節雄, 藤田 修, 伊藤 献一
    日本機械学会論文集B 64 625 3084 - 3090 1998年 [査読有り][通常論文]
  • 立田 節雄, 藤田 修, 伊藤 献一
    日本機械学会論文集B 64 624 2669 - 2676 1998年 [査読有り][通常論文]
  • O Fujita, K Ito, T Chida, S Nagai, Y Takeshita
    TWENTY-SEVENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, VOLS 1 AND 2 27 2573 - 2578 1998年 [査読有り][通常論文]
     
    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.
  • M Kikuchi, O Fujita, K Ito, A Sato, T Sakuraya
    TWENTY-SEVENTH SYMPOSIUM (INTERNATIONAL) ON COMBUSTION, VOLS 1 AND 2 27 2507 - 2514 1998年 [査読有り][通常論文]
     
    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.
  • 藤田 修, 菊池政雄, 伊藤献一, Sandra L.Olson, Takashi Kashiwagi, 桜谷 隆
    日本マイクログラビティ応用学会誌 14 1 10 - 18 1997年 [査読有り][通常論文]
  • NI Wakayama, H Ito, Y Kuroda, O Fujita, K Ito
    COMBUSTION AND FLAME 107 1-2 187 - 192 1996年10月 [査読有り][通常論文]
     
    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.
  • W Kang, O Fujita, K Ito
    JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME 118 1 82 - 87 1996年03月 [査読有り][通常論文]
     
    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.
  • 立田 節雄, 藤田 修, 伊藤 献一
    『日本機械学会論文集B編』 62 593 368 - 373 1996年 [査読有り][通常論文]
  • 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 1996年 [査読有り][通常論文]
     
    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.
  • 藤田 修, 伊藤 献一, 姜 友, 田中 啓一, 森田 知二
    日本機械学会論文集(B編) 61 591 4214 - 4218 1995年 [査読有り][通常論文]
  • H ITO, O FUJITA, K ITO
    COMBUSTION AND FLAME 99 2 363 - 370 1994年11月 [査読有り][通常論文]
     
    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.
  • 日本機械学会論文集B 60 570 662 - 667 1994年 [査読有り][通常論文]
  • 藤田修, 伊藤献一, Kang,Woo, 渡辺伸央
    日本機械学会論文集B 59 565 2914 - 2918 1993年05月 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • Measurement of flame propagation speed of coal dust cloud using microgravity environment
    ASME HTD 269 59 - 66 1993年 [査読有り][通常論文]
  • QUANTITATIVE-DETERMINATION OF FLAME COLORS BASED ON CIE 1931 STANDARD COLORIMETRIC SYSTEM
    S TATSUTA, O FUJITA, K ITO
    IMAGING IN TRANSPORT PROCESSES 471 - 479 1993年 [査読有り][通常論文]
  • 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 1992年05月 [査読有り][通常論文]
     
    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.
  • 雀 炳〓, 伊藤 献一, 藤田 修
    日本機械学会論文集B 58 545 242 - 247 1992年 [査読有り][通常論文]
  • K ITO, BC CHOI, O FUJITA
    JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES 33 4 778 - 784 1990年11月 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 伊藤 献一, 崔 炳, 藤田 修
    日本機械学会論文集B 55 519 3552 - 3557 1989年 [査読有り][通常論文]
  • O FUJITA, K ITO
    JSME INTERNATIONAL JOURNAL SERIES II-FLUIDS ENGINEERING HEAT TRANSFER POWER COMBUSTION THERMOPHYSICAL PROPERTIES 31 2 314 - 319 1988年05月 [査読有り][通常論文]
  • 藤田 修, 伊藤 献一
    日本機械学会論文集B 53 495 3454 - 3458 1987年 [査読有り][通常論文]
  • 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年 [査読有り][通常論文]
  • 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 1986年12月 [査読有り][通常論文]
  • 伊藤 献一, 藤田 修
    日本機械学会論文集B 52 476 2004 - 2010 1986年 [査読有り][通常論文]
  • 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 1985年11月 [査読有り][通常論文]
  • メタノール触媒酸化に及ぼすNOの影響
    伊藤献一, 藤田修
    日本機械学会論文集B 51 463 1066 - 1070 1985年03月 [査読有り][通常論文]
  • メタノール燃焼排気ガス中におけるNO/NO2変換
    伊藤献一, 矢野利明, 藤田修
    日本機械学会論文集 B編 51 461 231 - 238 1984年12月 [査読有り][通常論文]
  • Kenichi Ito, Osamu Fujita
    Proc.Comubstion Institute 20 53 - 59 1984年 [査読有り][通常論文]

書籍

  • 燃焼現象の基礎
    オーム社 2001年
  • 環境圏の新しい燃焼工学
    フジテクノシステム 1999年

講演・口頭発表等

  • Introduction of Combustion Research Project "FLARE" utilizing ISS/KIBO for Fire Safety Standard in the Next Generation  [招待講演]
    藤田 修
    6th International Symposium on Physical Science in space 2015年09月 口頭発表(基調)
  • INTERACTION BETWEEN ACOUSTIC VIBRATION AND PROPAGATING FLAMES DEFORMED BY EXTERNAL LASER IRRADIATION IN A COMBUSTION TUBE  [招待講演]
    Osamu Fujita, Yoshikazu Taniyama
    The 5th East Asia Mechanical and Aerospace Engineering Workshop 2015年05月 口頭発表(基調)
  • Impact of Gravity on Wire Insulation Combustion  [招待講演]
    藤田 修
    Asian Microgravity Symposium 2014 2014年10月 口頭発表(基調)
  • 藤田 修
    35th International Symposium on Combustion 2014年08月 口頭発表(招待・特別)
  • Impact of Gravitational Field on Flammability of Solid Material  [招待講演]
    藤田 修
    8th Asia-Pacific Conference on Combustion 2010年12月 口頭発表(招待・特別)

作品等

  • 50m級微小重力実験設備の設置
    2006年
  • Construction of New 50m dorp tower for microgravity experiments
    2006年
  • 外部から見たNASDAの先端実験設備の利用に対する期待(招請講演)

その他活動・業績

  • Nozomu Hashimoto, Yushin Naito, Kinya Saito, Jun Hayashi, Noriaki Nakatsuka, Fumiteru Akamatsu, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • Ajit Kumar Dubey, Yoichiro Koyama, Sung Hwan Yoon, Nozomu Hashimoto, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • Yusuke Konno, Nozomu Hashimoto, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • Nguyen Truong Gia Tri, Nozomu Hashimoto, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • Feng Guo, Yu Ozaki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • Yushin Naito, Nozomu Hashimoto, Osamu Fujita 12th Asia-Pacific Conference on Combustion, ASPACC 2019 2019年01月01日 [査読無し][通常論文]
     
    © 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.
  • 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 2018年11月14日 [査読無し][通常論文]
  • 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 2018年11月14日 [査読無し][通常論文]
  • 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 2018年11月14日 [査読無し][通常論文]
  • 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 2018年05月29日 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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 2017年11月13日 [査読無し][通常論文]
  • 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 2017年11月13日 [査読無し][通常論文]
  • 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 2017年11月13日 [査読無し][通常論文]
  • 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 2017年11月13日 [査読無し][通常論文]
  • 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 2017年09月20日 [査読無し][通常論文]
  • 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 2017年09月18日 [査読無し][通常論文]
  • 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 2017年05月20日 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
     
    © 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.
  • 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 年次大会 2017 (0) 2017年 [査読無し][通常論文]
     
    <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>
  • 金野 佑亮, 都築 克弥, 橋本 望, 藤田 修 年次大会 2017 (0) 2017年 [査読無し][通常論文]
     
    <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>
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
  • 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 2016年12月19日 [査読無し][通常論文]
  • 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 2016年11月26日 [査読無し][通常論文]
  • 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 2016年11月26日 [査読無し][通常論文]
  • 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 2016年11月26日 [査読無し][通常論文]
  • 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 2016年09月10日 [査読無し][通常論文]
  • 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 2016年05月11日 [査読無し][通常論文]
  • 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 2016年01月01日 [査読無し][通常論文]
     
    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.
  • 髙橋 弥楊, 橋本 望, 渡邊 裕章, 黒瀬 良一, 藤田 修 日本エネルギー学会大会講演要旨集 25 (0) 142 -143 2016年 [査読無し][通常論文]
     
    <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>
  • 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年 [査読無し][通常論文]
  • 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 53rd 500 -501 2015年11月04日 [査読無し][通常論文]
  • 水谷拳, 宮本恭輔, 橋本望, 藤田修 燃焼シンポジウム講演論文集 53rd 502 -503 2015年11月04日 [査読無し][通常論文]
  • 永地 大志, 吉岡 航佑, 橋本 望, 藤田 修 熱工学コンファレンス講演論文集 2015 "D131 -1"-"D131-2" 2015年10月23日 [査読無し][通常論文]
     
    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%.
  • 藤田 修 日本燃焼学会誌 57 (181) 174 -182 2015年08月 [査読無し][招待有り]
  • 藤田修, 水谷拳, 宮本恭輔, 吉岡航佑, 橋本望 宇宙科学技術連合講演会講演集(CD-ROM) 59th ROMBUNNO.3E04 2015年 [査読無し][通常論文]
  • 水谷拳, 宮本恭輔, 橋本望, 藤田修 日本伝熱シンポジウム講演論文集(CD-ROM) 52nd ROMBUNNO.B221 2015年 [査読無し][通常論文]
  • 藤田 修 日本燃焼学会誌 56 (176) 117 -124 2014年05月 [査読無し][招待有り]
  • Takanari Mizushima, Masao Kikuchi, Masahiro Takayanagi, Hiroyuki Torikai, Akihiko Ito, Shuhei Takahashi, Osamu Fujita Proceedings of the International Astronautical Congress, IAC 1 718 -723 2014年01月01日 [査読無し][通常論文]
     
    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 2014年01月 [査読無し][招待有り]
  • 伊東 弘行, 中原 毅朗, 酒井 雄人, 井田 民男, 藤田 修 バイオマス科学会議発表論文集 0 (7) 150 -151 2012年01月18日 [査読無し][通常論文]
     
    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...
  • Satoru MIZUNO, Tamio IDA, Manabu FUCHIHATA, Kunihiko NAMBA, Atsushi KAKOSAKA, Osamu FUJITA Journal of the Japan Institute of Energy 91 (1) 41 -47 2012年 [査読無し][通常論文]
  • 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 2011年05月 [査読無し][招待有り]
  • 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 2011年03月 [査読無し][通常論文]
  • 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年 [査読無し][招待有り]
  • 大西 尭, 増永 広太, 藤田 修, 中村 祐二, 伊東 弘行 北海道支部講演会講演概要集 2010 (49) 67 -68 2010年11月07日 [査読無し][通常論文]
  • 巌上 純也, 中村 祐二, 若月 薫, 伊東 弘行, 藤田 修 熱工学コンファレンス講演論文集 2010 (0) 93 -94 2010年10月29日 [査読無し][通常論文]
     
    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 ...
  • 伊東 弘行, 酒井 雄人, 藤田 修, 中村 祐二, 井田 茂男 熱工学コンファレンス講演論文集 2010 (0) 319 -320 2010年10月29日 [査読無し][通常論文]
     
    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...
  • 増永 広太, 大西 尭, 伊東 弘行, 中村 祐二, 藤田 修 年次大会講演論文集 : JSME annual meeting 2010 (3) 209 -210 2010年09月04日 [査読無し][通常論文]
     
    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...
  • 大西 陽介, 竹内 広行, 藤田 修, 伊東 弘行, 中村 祐二 北海道支部講演会講演概要集 2009 (48) 155 -156 2009年11月28日 [査読無し][通常論文]
  • 伊東 弘行, 酒井 雄人, 藤田 修, 中村 祐二, 井田 民男 熱工学コンファレンス講演論文集 2009 (0) 33 -34 2009年11月06日 [査読無し][通常論文]
     
    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 ...
  • 京野 嵩, 藤田 修, 城戸 泰裕, 中村 祐二, 伊東 弘行 年次大会講演論文集 : JSME annual meeting 2009 (8) 143 -144 2009年09月12日 [査読無し][通常論文]
     
    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 ...
  • 塚中 大介, 為田 数馬, 藤田 修, 中村 祐二, 伊東 弘行 北海道支部講演会講演概要集 2008 (47) 105 -106 2008年09月27日 [査読無し][通常論文]
  • 京野 嵩, 藤田 修, 城戸 泰裕, 中村 祐二, 伊東 弘行 北海道支部講演会講演概要集 2008 (47) 107 -108 2008年09月27日 [査読無し][通常論文]
  • 実験力学ハンドブック
    朝倉書店 2008年 [査読無し][招待有り]
  • Masanori KOBAYASHI, Ryosuke IMAI, Osamu FUJITA Transaction of JSME 74 (748) 2718 -2723 2008年 [査読無し][通常論文]
  • Journal of the Combustion Society of Japan 50 (153) 255 -263 2008年 [査読無し][通常論文]
  • Journal of the Combustion Society of Japan 50 (153) 264 -270 2008年 [査読無し][通常論文]
  • 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 2007年07月 [査読無し][招待有り]
  • 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 2007年03月 [査読無し][招待有り]
  • 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 2007年03月 [査読無し][招待有り]
  • Transaction of JSME 73 (727) 803 -808 2007年 [査読無し][通常論文]
  • Transaction of JSME 73 (727) 680 -686 2007年 [査読無し][通常論文]
  • DME ハンドブック
    日本DMEフォーラム 2006年 [査読無し][招待有り]
  • 永田 晴紀, 橋本 望, 加藤 隆博, 藤田 修, 伊藤 献一, 工藤 勲, 秋葉 鐐二郎 JASMA : Journal of the Japan Society of Microgravity Application 17 (3) 172 -177 2000年07月31日 [査読無し][通常論文]
  • On the Colors of Laminar Flames
    旭川工業高等専門学校研究報文 36 11 -19 1999年 [査読無し][通常論文]
  • 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年 [査読無し][通常論文]
     
    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)
  • O. Fujita, Y. Kuroda, K. Ito, N. I. Wakayama and Y. Takeshita : "Use of Microgravity Environment to Investigate the Effect of Magnetic Field on Flame Shape", Proceedings of the 20th International Symposium on Space Technology and Science, 946-951 (1996)
    1996年 [査読無し][通常論文]
  • Shuhei Takahashi, Hiroyuki Ito, Yuji Nakamura, Osamu Fujita 43rd International Conference on Environmental Systems [査読無し][通常論文]
     
    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

特許

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

受賞

  • 2018年11月 公益財団法人 谷川熱技術振興基金 粉生熱技術振興賞
     燃焼工学の進歩発展、とくに工業用加熱炉の燃焼現象の解明 
    受賞者: 藤田 修
  • 2018年02月 The Combustion Institute Fellow
     
    受賞者: 藤田 修
  • 2015年03月 日本航空宇宙学会 フェロー
     
    受賞者: 藤田 修
  • 2015年03月 北海道大学 教育総長賞
     Hokkaido ユニバーサルキャンパス・イニシャチブ事業への貢献 
    受賞者: 藤田 修
  • 2014年12月 日本燃焼学会 2014年「美しい炎」の写真展最優秀作品賞
     1歳のバースデーケーキ 
    受賞者: Sunghwan YOON;Taejoon NOH;藤田 修
  • 2013年10月 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 
    受賞者: 藤田 修
  • 2013年05月 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- 
    受賞者: 伊東弘行;酒井雄人;中原毅朗;井田民男;藤田 修
  • 2013年04月 日本機械学会 フェロー
     
    受賞者: 藤田 修
  • 2012年11月 日本機械学会熱工学部門部門 一般表彰(講演論文表彰)
     バイオコークス燃料の熱分解ガス放出特性に関する検討 
    受賞者: 伊東弘行;酒井雄人;井田民男;若月薫;藤田修
  • 2007年04月 日本機械学会 日本機械学会「論文賞」
     壁面に沿う拡散火炎中から壁面へのすす付着に及ぼす壁面温度の影響 
    受賞者: 藤田 修
  • 2006年 日本マイクログラビティ応用学会 日本マイクログラビティ応用学会「論文賞」
     微小重力場における低速空気流中のポリエチレン被覆導線の燃焼挙動 
    受賞者: 藤田 修
  • 2006年 The Best Paper Award of Japan Society of Microgravity Application
  • 1999年 日本燃焼学会 日本燃焼学会「奨励賞」
     微小重力環境を利用した固体材料の燃焼性と燃焼生成物に関する研究 
    受賞者: 藤田 修
  • 1999年 Award for young researchers, Combustion Society of Japan (1999.11)Best Flame Picture Award, Combustion Society of Japan, (2001.12)

共同研究・競争的資金等の研究課題

  • レーザ加熱火炎面曲率制御法による予混合火炎と圧力振動のCoupling機構解明
    日本学術振興会:科学研究費補助金基盤研究(A)
    研究期間 : 2018年04月 -2023年03月 
    代表者 : 藤田 修
  • 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
    日本学術振興会:科学研究費補助金基盤研究(B)
    研究期間 : 2014年03月 -2018年03月 
    代表者 : 藤田 修
  • Oxy-fuel 燃焼におけるすす生成条件Mapの提示とその拡大手法の検討
    日本学術振興会:科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 藤田 修
  • 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
    日本学術振興会:科学研究費補助金基盤研究(B)
    研究期間 : 2009年04月 -2013年03月 
    代表者 : 藤田 修
  • 日本学術振興会:科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2010年04月 -2012年03月 
    代表者 : 藤田 修
  • 日本学術振興会:科学研究費補助金基盤研究(B)
    研究期間 : 2006年04月 -2009年03月 
    代表者 : 藤田 修
  • Combustion of high density solid fuel derived from bio-resources
    Grant-in-Aid for Scientific Research
    研究期間 : 2007年
  • 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
    日本学術振興会:科学研究費補助金基盤研究(C)
    研究期間 : 2004年04月 -2005年03月 
    代表者 : 藤田 修
  • 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
    日本学術振興会:科学研究費補助金基盤研究(C)
    研究期間 : 1995年04月 -1997年03月 
    代表者 : 藤田 修
  • Igntion and subsequent flame spreding over solid material
    International Joint Research Projects
    研究期間 : 1995年
  • 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
    日本学術振興会:科学研究費奨励研究(A)
    研究期間 : 1993年04月 -1994年03月 
    代表者 : 藤田 修

教育活動情報

主要な担当授業

  • STSI基礎論
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
  • 大学院共通授業科目(教育プログラム):PARE
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : エネルギー,バイオマス,水資源,地下水,通信ネットワーク,交通システム
  • 大学院共通授業科目(教育プログラム):STSI
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : インド、日本、インターンシップ、チームワーク型研究、メンバー
  • 大学院共通授業科目(教育プログラム):STSI
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 持続可能性,輸送システム,社会インフラ,環境,政策,国際共同研究
  • 大学院共通授業科目(教育プログラム):STSI
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : インド、日本、インターンシップ、チームワーク型研究、リーダー
  • Space Utilization Engineering(宇宙環境利用工学E)
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Space utilization, Micro-gravity, Heat and mass transfer, Combustion, Optical measurements, Project proposal
  • 宇宙環境利用工学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Space utilization, Micro-gravity, Heat and mass transfer, Combustion, Optical measurements, Project proposal
  • Space Utilization Engineering(宇宙環境利用工学E)
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Space utilization, Micro-gravity, Heat and mass transfer, Combustion, Optical measurements, Project proposal
  • 宇宙環境利用工学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Space utilization, Micro-gravity, Heat and mass transfer, Combustion, Optical measurements, Project proposal
  • 国際交流Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 国際本部
    キーワード : Space utilization, Micro-gravity, Heat and mass transfer, Combustion, Optical measurements, Project proposal
  • 燃焼学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 燃料、燃焼計算、化学反応速度論、化学平衡、燃焼現象論、燃焼生成物、燃焼装置
  • 航空宇宙工学
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 航空機原動機、機体、翼、宇宙輸送、宇宙環境利用、人工衛星

大学運営

学内役職歴

  • 2013年4月1日 - 2015年3月31日 企画・経営室室員
  • 2015年4月1日 - 2017年3月31日 企画・経営室室員
  • 2017年4月1日 - 2019年3月31日 総長補佐
  • 2017年4月1日 - 2021年3月31日 アドミッションセンター副センター長
  • 2017年4月1日 -  教育改革室室員
  • 2019年4月1日 -  総長補佐

委員歴

  • 2020年07月 - 現在   国際燃焼学会   副会長
  • 2017年06月 - 現在   宇宙航空研究開発機構(JAXA)   宇宙科学運営協議会 運営協議員
  • 2017年04月 - 現在   北海道大学   総長補佐
  • 2017年03月 - 現在   日本マイクログラビティ応用学会   会長
  • 2014年10月 - 現在   日本学術会議   連携会員
  • 2014年08月 - 現在   国際燃焼学会   理事
  • 2009年04月 - 現在   宇宙航空研究開発機構   宇宙環境利用科学専門委員会委員(2009.4-2015.3宇宙環境利用科学委員会委員)
  • 2019年04月 - 2020年03月   日本機械学会   副会長
  • 2017年06月 - 2019年06月   日本燃焼学会   会長
  • 2004年04月 - 2019年06月   日本燃焼学会   理事(2011-2012専務理事、2013-2017副会長)   日本燃焼学会
  • 2017年04月 - 2018年03月   北海道大学工学研究院機械宇宙工学部門   部門長
  • 2017年04月 - 2018年03月   日本機械学会熱工学部門   部門長
  • 2015年05月 - 2017年04月   宇宙航空研究開発機構(JAXA)   宇宙科学研究所 宇宙工学委員
  • 2016年04月 - 2017年03月   北海道大学大学院工学研究院   国際交流室 室長
  • 2013年04月 - 2017年03月   北海道大学   企画・経営室室員
  • 2015年03月 - 2016年02月   日本航空宇宙学会   北部支部 支部長
  • 2010年04月 - 2015年03月   日本マイクログラビティ応用学会   理事(2003-2006, 2010-2015)
  • 2008年04月 - 2010年03月   日本機械学会   理事
  • 2006年 - 2008年   日本航空宇宙学会   宇宙利用部門 部門長   日本航空宇宙学会


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