研究者データベース

橋本 望(ハシモト ノゾム)
工学研究院 機械・宇宙航空工学部門 宇宙航空システム
准教授

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

  • 准教授

学位

  • 博士(工学)(北海道大学)

ホームページURL

科研費研究者番号

  • 70392751

ORCID ID

Researcher ID

  • A-4504-2015

J-Global ID

研究キーワード

  • 燃焼   Combustion of a Solid Fuel   Rocket Engine   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 熱工学

職歴

  • 2015年01月 - 現在 北海道大学大学院 工学研究院 機械宇宙工学部門 准教授
  • 2005年08月 - 2014年12月 電力中央研究所 エネルギー技術研究所 主任研究員
  • 2004年04月 - 2005年07月 電力中央研究所 エネルギー技術研究所 研究員

学歴

  • 2001年04月 - 2004年03月   北海道大学大学院   工学研究科   機械科学専攻
  •         - 2001年   北海道大学   工学研究科   機械科学
  •         - 2001年   北海道大学
  •         - 1999年   北海道大学   工学部   機械工
  •         - 1999年   北海道大学

所属学協会

  • 北海道宇宙科学技術創成センター   日本鉄鋼協会   日本液体微粒化学会   日本マイクログラビティ応用学会   日本ガスタービン学会   日本エネルギー学会   化学工学会   日本機械学会   日本燃焼学会   日本航空宇宙学会   

研究活動情報

論文

  • Nozomu Hashimoto, Jun Hayashi
    KONA Powder and Particle Journal 2021年01月10日 [査読有り][通常論文]
  • Yusuke Konno, Nozomu Hashimoto, Osamu Fujita
    Combustion and Flame 220 7 - 15 2020年10月 [査読有り][通常論文]
     
    © 2020 The Combustion Institute Theoretical and experimental works have been carried out to clarify the effect of core material on the extinction characteristics of the flame spreading over electric wires. Additionally, an attempt has been made to explain previous experimental results (Takahashi et al., 2013 [1]) which found that Limiting Oxygen Concentration (LOC) of copper (Cu) wire is higher than that of nickel-chrome (NiCr) wire. A theoretical model is developed to discuss the heat loss mechanism in the unburned zone ahead of the gas-phase preheat zone and its validity is confirmed by measured temperature profiles along Cu, iron (Fe), and NiCr wires insulated by low-density polyethylene (LDPE). The theoretical analysis reveals that the flame spread rate is a crucial value to assess the extinction characteristics of the flame spreading over electric wires because it controls heat loss in the unburned zone. The reduction of the flame spread rate increases heat loss in the unburned zone and induces the quenching extinction as a result of extended thermal diffusion length along the electric wire. It is also found that a highly conductive wire increases heat loss rather than poorly conductive wire even under the same flame spread rate. Such characteristics are well described by a newly introduced parameter, ηf, which is a dimensionless flame spread rate derived by the present study. By using ηf, previous experimental findings [1] are successfully explained.
  • Ajit K. Dubey, 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, Khalid Hadi, Nozomu Hashimoto, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
    Fuel 268 117383 - 117383 2020年05月 [査読有り][通常論文]
  • 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.
  • 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01日 [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.
  • Feng Guo, Wataru Hase, Yu Ozaki, Yusuke Konno, Masaya Inatsuki, Katsunori Nishimura, Nozomu Hashimoto, Osamu Fujita
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 109 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 207 63 - 70 2019年09月 [査読有り][通常論文]
     
    © 2019 The Combustion Institute To evaluate the fire-retardant effectiveness of organophosphorus compounds (OPC) added to Li-ion battery electrolyte solvents, the limiting oxygen concentration (LOC) method is used in conjunction with a wick combustion system, called as wick-LOC method. With the wick-LOC method, two modes of stabilized flame are found, namely, wake flame and full flame. When OPC is added to the electrolyte, two distinct branches of extinction processes occur according to the different flame modes near extinction with no transition from the full flame to the wake flame in the case of higher OPC addition. The flame stability limits are measured as a function of OPC addition for both flame modes. The wake flame is shown to be consistently more stable at low levels of OPC addition. However, once the OPC addition exceeds a critical amount, the full flame shows higher stability with a lower LOC than the wake flame. These phenomena in the two regimes are also found in other cases of high OPC addition (different type of OPC and electrolyte solvent). In the most stable flame mode, the regime switches from the wake flame to the full flame with increasing OPC addition, and they are defined correspondingly as “blow-off regime” and “quenching regime”. To explain the presence of these two regimes, the thermal balance effect is considered in the discussion of flame extinction mechanisms. The difference in flame volume near the extinction limit shows that the quenching mechanism dominates flame extinction under higher OPC addition. The thermal balance effect on flame stabilization or extinction can be the additional impact on the fire retardation abilities of OPC itself.
  • 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, Nozomu Hashimoto, Akihiro Hayakawa, Hideaki Kobayashi, Osamu Fujita
    Fuel 246 178 - 186 Elsevier {BV} 2019年06月 [査読有り][通常論文]
  • Kazuki Tainaka, Yong Fan, Nozomu Hashimoto, Hiroyuki Nishida
    Renewable Energy 136 358 - 364 Elsevier {BV} 2019年06月 [査読有り][通常論文]
  • Masashi Nagachi, Fumiya Mitsui, Jean-Marie Citerne, Hugo Dutilleul, Augustin Guibaud, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
    Fire Technology 2019年04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.
  • Jun Hayashi, Jun Hayashi, Nozomu Hashimoto, Nozomu Hashimoto, Noriaki Nakatsuka, Kazuki Tainaka, Hirofumi Tsuji, Kenji Tanno, Hiroaki Watanabe, Hisao Makino, Fumiteru Akamatsu
    Proceedings of the Combustion Institute 37 3045 - 3052 2019年01月 [査読有り][通常論文]
     
    © 2018 The Combustion Institute. In this study, transient soot formation processes in a small-scale jet burner (CRIEPI burner) were investigated by simultaneous measurements of coal particles, polycyclic aromatic hydrocarbons (PAHs) and soot. Pairs of simultaneous measurements of "Mie scattering measurement for coal particles with laser induced fluorescence (LIF) for PAHs" and "LIF for PAHs with laser induced incandescence (LII) for soot" were performed to understand the transitive formation processes of soot formation in pulverized coal flame, whose signals were successfully separated. Findings in the present study are as follows. Coal particles, PAHs and soot were distributed in this order in radial direction from the central axis. Existing regions of coal particles, PAHs and soot were overlapped from the time averaged viewpoint while there were few overlapping areas of coal particles, PAHs and soot from the instantaneous viewpoint. This result indicates that a long time is required for the formation of soot from 2 to 3 rings PAHs through larger PAHs.
  • Khalid Hadi, Ryo Ichimura, Nozomu Hashimoto, Osamu Fujita
    Proceedings of the Combustion Institute 37 2935 - 2942 2019年01月 [査読有り][通常論文]
     
    © 2018. The present study aims to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent flame propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments on spherical turbulent flame propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted. A common bituminous coal was used in the present study. The flame propagation velocity was obtained from an analysis of flame propagation images taken using a high-speed camera. It was found that the flame propagation velocity increased with increasing flame radius. The flame propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical flames using gaseous fuel. The coal concentration has a weak effect on the flame propagation velocity, which is unique to pulverized coal combustions in a turbulent field. These are the first reports of experimental results for the spherical turbulent flame propagation behavior of pulverized coal particle clouds. The results obtained in the present study are obviously different from those of previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.
  • 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.
  • Masashi Nagachi, Fumiya Mitsui, Jean Marie Citerne, Hugo Dutilleul, Augustin Guibaud, Grunde Jomaas, Grunde Jomaas, Guillaume Legros, Nozomu Hashimoto, Osamu Fujita
    Proceedings of the Combustion Institute 37 4155 - 4162 2019年01月 [査読有り][通常論文]
     
    © 2018. Concurrent flame spread over electric wire insulation was studied experimentally in microgravity conditions during parabolic flights. Polyethylene insulated Nickel-Chrome wires and Copper wires were examined for external flow velocities ranging from 50 mm/s to 200 mm/s. The experimental results showed that steady state flame spread over wire insulation in microgravity could be achieved, even for concurrent flow. A theoretical analysis on the balance of heat supply from the flame to the unburned region, radiation heat loss from the surface to the ambient and required energy to sustain the flame propagation was carried out to explain the presence of steady spread over insulated wire under concurrent flow. Based on the theory, the change in heat input (defined by the balance between heat supply from flame and radiation heat loss) was drawn as a function of the flame spread rate. The curve intersected the linear line of the required energy to sustain the flame. This balance point evidences the existence of steady propagation in concurrent flow. Moreover, the estimated steady spread rate (1.2 mm/s) was consistent with the experimental result by considering the ratio of the actual flame length to the theoretical to be 0.5. Further experimental results showed that the concurrent flame spread rate increased with the external flow velocity. In addition, the steady spread rate was found to be faster for Copper wires than for Nickel-Chrome wires. The experimental results for upward spreading (concurrent spreading) in normal gravity were compared with the microgravity results. In normal gravity, the flame did not reach a steady state within the investigated parameter range. This is due to the fact that the fairly large flame spread rate prevented the aforementioned heat balance to be reached, which meant that such a spread rate could not be attained within the length of the tested sample.
  • Ajit Kumar Dubey, Yoichiro Koyama, Nozomu Hashimoto, Osamu Fujita
    Proceedings of the Combustion Institute 37 1869 - 1877 2019年01月 [査読有り][通常論文]
     
    © 2018 The Combustion Institute. Experiments and theoretical analysis are presented to clarify the effect of geometrical parameters on thermo-acoustic instability of downward propagating flames in tubes. The experiments reveal that the longer tubes have higher instability compared to shorter tubes and the lower diameter tubes have higher instability compared to higher diameter tubes. The secondary instability leading to turbulent burning is found to be more sensitive to change in geometrical parameters compared to primary instability (oscillating flat flame). The secondary instability is re-stabilized for some intermediate burning velocity conditions even though lower and higher burning velocity conditions show secondary instability. The appearance of such re-stabilization is only observed for some specific lengths of the tube. Present experimental observations pertaining to the effect of geometrical parameters is found to be contradicting the theoretical predictions based on pressure coupling mechanism. To clear the underlying mechanism, analytical growth rate is computed considering velocity coupling mechanism. The computed growth rates correctly predict the effect of geometrical parameters on thermo-acoustic instability of downward propagating flames. This work provides further evidence to believe that the flame -acoustic coupling in downward propagating flames is due to flame area modulation (leading to heat release modulation) through action of acoustic acceleration.
  • 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.
  • Yongho Chung, Osamu Fujita, Nozomu Hashimoto
    Proceedings of the Combustion Institute 37 1887 - 1894 2019年01月 [査読有り][通常論文]
     
    © 2018. An experimental study is conducted to investigate the effect of Le on the transition to secondary acoustic instability when the curvature of the flame front in a tube is induced and controlled by using external laser irradiation. Once a downward-propagating flame in the primary acoustic instability region is exposed to a specific laser irradiation condition, the flame is transferred to the secondary acoustic instability region. The transition limit is decreased, that is, transition occurs is an easier manner, with increasing laser power input. While the flame propagates with increasing laser irradiation, the flame first exhibits a convex curvature owing to laser irradiation and then a concave structure is formed owing to buoyancy-induced flow. Two types of transition behavior caused by the concave structure and the convex structure are observed. The conflicting thermal-diffusive effect depending on Le leads to the differing transition behaviors. Based on an evaluation of the flame stretch effect attributed to the flame front curvature, it is confirmed that the Lewis number effect influences the transition criteria.
  • Nozomu Hashimoto, Hiroyuki Nishida, Masayoshi Kimoto, Kazuki Tainaka, Atsushi Ikeda, Satoshi Umemoto
    Renewable Energy 126 924 - 932 2018年10月 [査読有り][通常論文]
     
    © 2018 Elsevier Ltd This study investigated the effect of crude Jatropha oil (CJO) blending with C-heavy oil on the combustion characteristics of oil-fired boilers. Combustion experiments were conducted using a 550 kW liquid fuel combustion test facility equipped with a steam-atomizing burner. The results indicated that the flame radiation intensity is decreased by the CJO blending with C-heavy oil. Consequently, the heat absorption of the sections near the burner decreases. Due to the lower nitrogen and sulfur contents in CJO, the NOx and SO 2 emissions are decreased by the CJO blending with C-heavy oil. It was also found that both the particulate matter concentration and the particle size in the exhaust gas are decreased by the CJO blending. This is attributed by the low carbon residue content of CJO. The results of this study imply that when CJO is introduced into oil-fired thermal power stations, considerable attention should be paid to changes in the heat absorption balance and the possibility of a decrease in the particle collection efficiency of the electrostatic precipitator.
  • 微粉炭燃焼場におけるすす計測技術
    泰中一樹, 橋本 望, 梅本 賢, 中塚記章, 林 潤, 渡邊裕章, 赤松史光, 牧野尚夫
    粉体工学会誌 55 5 275 - 281 2018年05月 [査読無し][招待有り]
  • 林 潤, 赤松 史光, 中塚 記章, 橋本 望, 渡邊 裕章, 黒瀬 良一, 泰中 一樹, 辻 博文, 牧野 尚夫
    粉体工学会誌 = Journal of the Society of Powder Technology, Japan 55 3 138 - 146 粉体工学会 2018年01月 [査読無し][通常論文]
  • Ken Mizutani, Kyosuke Miyamoto, Nozomu Hashimoto, Yusuke Konno, Osamu Fujita
    INTERNATIONAL JOURNAL OF MICROGRAVITY SCIENCE AND APPLICATION 35 1 350104  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.
  • Jun Hayashi, Nozomu Hashimoto, Nozomu Hashimoto, Hiroyuki Nishida, Fumiteru Akamatsu
    Atomization and Sprays 27 1077 - 1087 2017年12月 [査読有り][通常論文]
     
    The soot formation characteristics of a palm methyl ester (PME) spray flame were investigated through a comparison with those of diesel fuel and n-dodecane in a simple combustion field. A laminar counterflow field was used as a simple combustion field to investigate in detail the spray flame structures and soot formation. The effects of the existence of PAHs in the fuel on soot formation in a PME spray flame were also investigated. n-dodecane has a straight chain structure and does not contain oxygen atoms in its molecular structure, thus allowing us to determine the effects of the oxygenated characteristics of PME on soot formation in a PME spray flame. The spray characteristics of those fuels and the soot formation characteristics were measured and analyzed using phase Doppler anemometry (PDA) and two-dimensional laser-induced incandescence (LII), respectively. Results showed that the PME spray flame formed less soot than the diesel spray flame and the PME spray flame had a narrow vertical distribution of soot formation compared to the diesel spray flame because the range of volatilities of the components in PME is narrower than that of the diesel fuel. Also, the PME and n-dodecane spray flames had similar time-averaged soot volume fractions and instantaneous structure of soot formation characteristics, despite only PME having oxygen in its molecular structure.
  • 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.
  • Hiroshi Nomura, Takahiro Murakoshi, Yusuke Suganuma, Yasushige Ujiie, Nozomu Hashimoto, Hiroyuki Nishida
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 36 2 2425 - 2432 2017年 [査読有り][通常論文]
     
    Droplet evaporation in sub-and supercritical environments has been studied experimentally under microgravity conditions. A single suspended droplet of n-hexadecane was employed for the experiments. The initial droplet diameter was 0.4 mm. A pair of alumina/silica fibers of 7 mu m in diameter was applied to suspend a droplet. The ambient pressure was varied in the range of 1.0-3.0 MPa, and the ambient temperature was set at 773 K. Sequential backlit images of an evaporating droplet were recorded using a high-speed digital video camera. Temporal variations in the droplet diameter were measured using a self-made computer-aided image analyzer. Microgravity conditions were produced by a 50-m drop tower. Temporal variations in the droplet diameter were successfully obtained for droplet evaporations in the supercritical environments. The normalized droplet lifetime increased with the ambient pressure. The evaporation rate constant increased with the ambient pressure, reached the maximum value at an ambient pressure slightly above the critical pressure of the fuel, and then decreased. The initial heat-up period linearly increased with the ambient pressure, reached the maximum value at an ambient pressure of 2.0 MPa, and then decreased. The ratio of the initial heat-up period to droplet lifetime increased with the ambient pressure, reached the maximum value of about 0.6 at an ambient pressure of 2.0 MPa, and then decreased. The droplet evaporation lifetime increased with the ambient pressure at subcritical ambient pressures even though the evaporation rate constant increased be-cause the increase in the initial heat-up period overtook the decrease in the quasi-steady evaporation period. It was found that, in the case of fuels with a high critical temperature, the initial heat-up period determines the ambient pressure dependence of the droplet evaporation lifetime in the environments around the critical point of the fuel. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.
  • Nozomu Hashimoto, Hiroaki Watanabe, Ryoichi Kurose, Hiromi Shirai
    ENERGY 118 47 - 59 2017年01月 [査読有り][通常論文]
     
    To investigate the effects of fuel NO formation models on the prediction of NO concentrations in a coal combustion field, numerical simulations for a coal combustion field in a 760 kW test furnace were performed. Three models, those proposed by De Soete, Chen et al. and Mitchell et al. were employed to calculate fuel NO formation originating from volatile matter. The results show that the model proposed by Mitchell et al. reproduces the tendency of the experimental data better than the other two models. In addition, the difference between the NO conversion ratios of bituminous coal and sub-bituminous coal that contains a high level of moisture was examined in detail using simulation results from the model of Mitchell et al. It was found that the formation of a region with a low oxygen mole fraction immediately downstream of a region with a high NO production rate is essential to realize a low NO conversion ratio. (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.
  • Nozomu Hashimoto, Hiroaki Watanabe
    FUEL PROCESSING TECHNOLOGY 145 20 - 30 2016年05月 [査読有り][通常論文]
     
    To investigate the effect of the furnace scale on the heat transfer mechanism of coal particles, numerical simulations of coal combustion fields in three different scale furnaces (915 MWth actual large scale boiler, 2.4 MWth and 0.76 MWth test furnaces) were conducted. High accuracy of simulation methods was validated with the measured data. From the comparison of numerical simulations between three different scale furnaces, it was clarified that the particle residence time with high particle temperature for a small scale furnace is shorter than that for a large scale furnace even if the particle residence time passing the high temperature gas is the same. This is caused by the insufficient heat gain of particles for a small scale furnace due to the lower radiation heat transfer because of the thinner flame thickness in the small furnace. The sphericity of ash particles from small scale furnaces is lower than that for large scale furnaces due to the shorter particle residence time with high particle temperature. These findings should be considered when the usability of coal brands for actual large scale boilers is evaluated by the fly ash properties from a small scale experimental furnace. (C) 2016 Elsevier B.V. All rights reserved.
  • Nozomu Hashimoto, Jun Hayashi, Noriaki Nakatsuka, Kazuki Tainaka, Satoshi Umemoto, Hirofumi Tsuji, Fumiteru Akamatsu, Hiroaki Watanabe, Hisao Makino
    JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 11 3 JTST0049  2016年 [査読有り][通常論文]
     
    To develop accurate models for the numerical simulation of coal combustion field, detailed experimental data using laser techniques, which can figure out the basic phenomena in a coal flame, are necessary. In particular, soot is one of the important intermediate substances in a coal flame. This paper is the first paper in the world reporting soot particle size distributions in a coal flame. The spatial distribution of the primary soot particle diameter were measured by the combination of the time-resolved laser induced incandescence (TiRe-LII) method and the thermophoretic sampling (TS) method. The primary soot particle diameter distribution was expressed by the log normal function based on the particle diameter measurement using SEM images obtained from the TS samples. The relative function between the signal decay ratio obtained by TiRe-LII and the primary soot particle diameter was defined based on the log normal function. Using the relative function, the spatial distributions of the primary soot particle diameter with the soot volume fraction were obtained. The results show that the small isolated soot regions instantaneously exist in the entire combustion field. This characteristics is different from spray combustion field. From the ensemble-averaged TiRe-LII images, it was found that the soot volume fraction and the primary soot particle diameter increases with increasing the height above the burner in any radial distance. It was also found that the volumetric ratio of small particles decreases with increasing radial distance at the region close to the burner exit. However, the variation of the soot particle diameter distribution along the radial direction becomes small in the downstream region. This tendency is caused by the turbulent mixing effect. It is expected that the accurate soot formation model will be developed in the near future by using the data reported in this paper.
  • Nozomu Hashimoto, Hiroshi Nomura, Masato Suzuki, Takahiro Matsumoto, Hiroyuki Nishida, Yasushi Ozawa
    FUEL 143 202 - 210 2015年03月 [査読有り][通常論文]
     
    To investigate the evaporation characteristics of a palm methyl ester (PME) droplet at high ambient temperatures, droplet evaporation experiments were conducted. Thermogravimetric and differential thermal analyses (TG-DTA) were also conducted to investigate the presence of exothermic reactions during fuel evaporation. The results for PME were compared with those for diesel fuel and n-hexadecane. The results show that the initial heating period decreases and the average evaporation coefficient increases with increasing ambient temperature for all fuels. As a results, the droplet lifetime decreases with increasing ambient temperature for all fuels. It was found that the droplet lifetime of PME is longer than that of diesel fuel and n-hexadecane. The average evaporation coefficients of PME and diesel fuel are almost equal. The longer initial heating period of PME due to the higher boiling points of the components leads to the longer droplet lifetime. It was also found that exothermic reactions occur during PME droplet evaporation. The exothermic reactions are considered to be polymerization reactions of the unsaturated fatty acid methyl esters. The volume of the residue formed by the polymerization reactions decreases with increasing ambient temperature due to the shorter reaction time before complete evaporation. (C) 2014 Elsevier Ltd. All rights reserved.
  • 金子堅太郎, 野村浩司, 橋本望
    微粒化 23 80 87 - 94 2014年11月 [査読有り][通常論文]
  • Nozomu Hashimoto, Hiromi Shirai
    ENERGY 71 399 - 413 2014年07月 [査読有り][通常論文]
     
    To investigate the cause of the increase in the unburned fraction when sub-bituminous coal is mixed with bituminous coal observed in previous experimental research using a 100 kg-coal/h-class coal combustion test furnace, numerical simulations of the mixed combustion of sub-bituminous coal and bituminous coal are performed. To take into account the effect of the particle heating rate on the devolatilization parameters, the tabulated-devolatilization-process model (TDP model) is employed. The results show that the simulation could qualitatively reproduce the experimental results, which are an increase in flame lift-off with increasing sub-bituminous coal mixing ratio and a maximum value of the unburned fraction at a sub-bituminous coal mixing ratio of 25%. Furthermore, it is clarified from the simulation results that the nonlinear increase in the overall unburned fraction in the case of sub-bituminous coal mixing with bituminous coal is caused by the steep increase in the unburned fraction of bituminous coal particles with increasing sub-bituminous coal mixing ratio. (C) 2014 Elsevier Ltd. All rights reserved.
  • Nozomu Hashimoto, Hiroyuki Nishida, Yasushi Ozawa
    FUEL 126 194 - 201 2014年06月 [査読有り][通常論文]
     
    To investigate the combustion characteristics of Jatropha pure oil (JPO) and Jatropha methyl ester (JME) as an alternative fuels for gas turbines, combustion experiments were conducted at atmospheric pressure employing an air-assist pressure swirl atomizer. As well as the NOx and CO concentrations and smoke number in the exhaust gas, the flame radiation intensity was measured using the two-color method. The results show that the flame radiation intensity and the soot emission decrease with increasing mixing ratio of JPO or JME to diesel fuel. It was also found that the flame radiation intensity has a strong correlation with the mean diameter of the fuel spray for all fuels. The CO emission for JPO is higher than those for JME and diesel fuel in the case of low flame temperature. (C) 2014 Elsevier Ltd. All rights reserved.
  • Yong Fan, Nozomu Hashimoto, Hiroyuki Nishida, Yasushi Ozawa
    FUEL 121 271 - 283 2014年04月 [査読有り][通常論文]
     
    The effect of the kinematic viscosity on liquid sprays injected by an air-assist pressure-swirl atomizer has been investigated in a series of experiments employing pulse-laser backlight imaging and laser diffraction droplet size distribution measurements. Sprays of crude Jatropha oil, Jatropha methyl ester, diesel fuel and propylene glycol brine were examined, and the liquid viscosity was controlled by changing the liquid temperature. It was found that atomization of the liquids was improved by introducing the assist air. Instantaneous images of the sprays taken using pulse-laser backlight illumination show that the 'spray cone' inside the nozzle cap evolves into the following five phases as the Reynolds number increases (i.e., liquid viscosity decreases): (1) a twisted liquid jet, (2) a folded liquid film, (3) a hollow spray cone with a smooth spray cone surface, (4) an unstable spray cone with periodic fluctuation, (5) a spray cone with many wrinkles on the cone surface. It was found that the droplet size in terms of the Sauter mean diameter (SMD) is small when the spray width is large. The SMD did not monotonically increase with the liquid viscosity. A local maximum of the SMD in the SMD vs. liquid viscosity curve was observed in the unstable transitional region where the transition from laminar flow to turbulent flow occurred. A local minimum of the SMD was observed at a higher liquid viscosity, where the 'spray cone' inside the nozzle cap changed from a twisted liquid jet to a folded liquid film. The change in the SMD as a function of liquid viscosity has a strong correlation with that in the flame radiation intensity as a function of liquid viscosity observed in a combustion test employing the same fuel atomizer (Hashimoto et al. submitted for publication). This indicates that the flame radiation intensity can be decreased by improving atomization characteristics. (C) 2013 Elsevier Ltd. All rights reserved.
  • 野村 浩司, 金子 堅太郎, 橋本 望
    International Journal of Microgravity Science Application 31 4 159 - 164 2014年 [査読有り][通常論文]
  • Jun Hayashi, Nozomu Hashimoto, Noriaki Nakatsuka, Hirofumi Tsuji, Hiroaki Watanabe, Hisao Makino, Fumiteru Akamatsu
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 34 2 2435 - 2443 2013年 [査読有り][通常論文]
     
    Soot formation characteristics of a lab-scale pulverized coal flame were investigated by performing carefully controlled laser diagnostics. The spatial distributions of soot volume fraction and the pulverized coal particles were measured simultaneously by laser induced incandescence (LII) and Mie scattering imaging, respectively. In addition, the radial distributions of the soot volume fraction were compared with the OH radical fluorescence, gas temperature and oxygen concentration obtained in our previous studies [1,2]. The results indicated that the laser pulse fluence used for LII measurement should be carefully controlled to measure the soot volume fraction in pulverized coal flames. To precisely measure the soot volume fraction in pulverized coal flames using LII, it is necessary to adjust the laser pulse fluence so that it is sufficiently high to heat up all the soot particles to the sublimation temperature but also sufficiently low to avoid including a too large of a change in the morphology of the soot particles and the superposition of the LII signal from the pulverized coal particles on that from the soot particles. It was also found that the radial position of the peak LII signal intensity was located between the positions of the peak Mie scattering signal intensity and peak OH radical signal intensity. The region, in which LII signal, OH radical fluorescence and Mie scattering coexisted, expanded with increasing height above the burner port. It was also found that the soot formation in pulverized coal flames was enhanced at locations where the conditions of high temperature, low oxygen concentration and the existence of pulverized coal particles were satisfied simultaneously. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
  • Nozomu Hashimoto, Ryoichi Kurose, Hiromi Shirai
    FUEL 97 277 - 287 2012年07月 [査読有り][通常論文]
     
    The effect of the devolatilization model on the coal particle behavior is investigated in detail by performing numerical simulations of a simple pulverized coal jet flame formed by a small jet burner (0.5 kg-coal/h) [S. Hwang et al., Energy & Fuels 2005;19:382-92]. As the devolatilization model, widely-used conventional devolatilization model, two competing reaction rate model and newly-proposed tabulated-devolatilization-process model (TDP model) [N. Hashimoto et al., Combust Flame 2012;159:353-366] are used. The results show that the coal particle velocities predicted by the TDP model are in better agreement with the experiments than those by the other models, with a slight increase in computation time. The difference in the mean axial particle velocity between the simulations is caused by the difference in the axial gas velocity, which is ultimately caused by the difference in the volatile matter evolution rate. It is also found that the devolatilization model has great influence on particle velocity prediction compared to the turbulence model, the gas-phase combustion model and the radiation model. (C) 2012 Elsevier Ltd. All rights reserved.
  • Nozomu Hashimoto, Ryoichi Kurose, Seung-Min Hwang, Hirofumi Tsuji, Hiromi Shirai
    COMBUSTION AND FLAME 159 1 353 - 366 2012年01月 [査読有り][通常論文]
     
    A new coal devolatilization model employing a tabulated-devolatilization-process model (TDP model) is developed, and its validity is investigated by performing a numerical simulation of a pulverized coal combustion field formed by an industrial low-NO, burner in a 100 kg-coal/h test furnace. The predicted characteristics of the pulverized coal combustion field obtained from the simulation employing the TDP model are compared with those employing the conventional devolatilization model, those employing the two competing reaction rate model, and the experiments. The results show that drastic differences in the gas flow patterns and coal particle behavior appear between simulations. In particular, the recirculation flow behavior is strongly affected by the difference in the coal devolatilization model because of the difference in the volatile matter evolution rate. The TDP model captures the observed behavior of the coal particles in the experiment better than the other models. Although it is considered that by adjusting the devolatilization parameters the prediction similar to the TDP model is also possible by the other models, appropriate devolatilization parameters are automatically set to particles depending on the particle heating rate without trial-error method by employing the TDP model. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
  • Hashimoto N, Hwang S.-M, Kurose R, Tsuji H, Shirai H
    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 76 769 1396 - 1405 2010年 [査読有り][通常論文]
  • Hashimoto N, Kurose R, Shirai H
    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 76 769 1386 - 1395 2010年 [査読有り][通常論文]
  • 鈴木 真人, 野村 浩司, 橋本 望
    自動車技術会論文集 40 5 1351 - 1356 自動車技術会 2009年09月 [査読有り][通常論文]
  • SUZUKI Masato, NOMURA Hiroshi, HASHIMOTO Nozom
    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN 7 ists26 Ph_43 - Ph_48 Japan Society for Aeronautical and Space Sciences 2009年 [査読有り][通常論文]
  • Tsuji H, Hashimoto N, Sfflral H, Makino H
    Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy 88 5 422 - 429 2009年 [査読有り][通常論文]
  • Nozomu Hashimoto, Yasushi Ozawa, Noriyuki Mori, Isao Yuri, Tohru Hisamatsu
    FUEL 87 15-16 3373 - 3378 2008年11月 [査読有り][通常論文]
     
    To investigate the combustion characteristics of palm methyl ester (PME) as an alternative fuel for gas turbines, combustion experiments at atmospheric pressure using high-temperature air (673 K) were performed. Chemical equilibrium calculations and investigations of fuel atomizing characteristics using a laser diffraction spray analyzer (LDSA) were also conducted. The results show that combustion characteristics of PME are similar to those of diesel fuel. Furthermore, it is indicated that NO, emissions can be reduced by using PME instead of diesel fuel for gas turbines. (C) 2008 Elsevier Ltd. All rights reserved.
  • 鈴木 真人, 野村 浩司, 橋本 望, 氏家 康成
    微粒化 = Atomization : journal of the ILASS-Japan 17 58 74 - 80 日本液体微粒化学会 2008年06月 [査読有り][通常論文]
  • 赤間 和樹, 林 潤, 瀬尾 健彦, 安 鐵朱, 赤松 史光, 橋本 望, 西田 啓之
    微粒化 = Atomization : journal of the ILASS-Japan 17 58 95 - 101 日本液体微粒化学会 2008年06月 [査読有り][通常論文]
  • Nozomu Hashimoto, Ryoichi Kurose, Hirofumi Tsuji, Hiromi Shirai
    ENERGY & FUELS 21 4 1950 - 1958 2007年07月 [査読有り][通常論文]
     
    A three-dimensional numerical simulation is applied to a pulverized coal combustion field in a furnace equipped with three burners, and the trajectories of the coal particles with respect to each burner, which are hardly obtained experimentally, are also investigated in detail. Simulation results are compared with experimental results. The results show that the numerical and experimental results are consistent generally. Also, the examination of the particle trajectories shows that most of the unburned carbon originates from the upper-stage burner. This result suggests that the overall unburned fraction can be reduced by supplying coal with a low combustibility to lower- or middle-stage burners and supplying coal with a high combustibility to the upper-stage burner.
  • Ryoichi Kurose, Hisao Makino, Nozomu Hashimoto, Akira Suzuki
    POWDER TECHNOLOGY 172 1 50 - 56 2007年03月 [査読有り][通常論文]
     
    Coal is an important energy resource for meeting the future demand for electricity, as coal reserves are much more abundant than those of other fossil fuels. In this study, the percolation model, which can account for swelling due to devolatilization and ash agglomeration, is applied to particulate matter formation process in coal combustion, and the effects of coal properties, ambient temperature, ambient pressure and initial coal size on the characteristics of a burning coal particle are studied. The devolatilization rate of coal is given by the first-order reaction model with FLASHCHAIN (R) model [Niksa, S., Combust. Flame, 100, (1995) 384-394.]. The characteristics of a burning coal particle are investigated under the atmospheric and high pressure conditions. The results show that in the atmospheric pressure condition, the characteristics of the burning coal particle obtained by the percolation model are in general agreement with the experimental data. The particle diameter of Newlands coal with higher fuel ratio and ash content is larger than that of Plateau coal in the char-combustion-dominant process. As the ambient temperature increases, the particle diameter becomes small in the early stage of the char-cornbustion-dornmant process, but becomes large afterward. The porosity in the char-combustion-dominant process decreases with decreasing the initial coal size. It is also observed that the effect of ambient pressure is prominent in the char-combustion-dominant process. The particle diameter and porosity in the pressurized condition are greater than those in the atmospheric pressure condition. These behaviors can be explained by the interaction between char reaction and ash agglomeration. (c) 2006 Elsevier B.V. All rights reserved.
  • Nozomu Hashimoto, Harunori Nagata, Tsuyoshi Totani, Isao Kudo
    COMBUSTION AND FLAME 147 3 222 - 232 2006年11月 [査読有り][通常論文]
     
    This study clarified the blowoff mechanism for a flame spreading in an opposed turbulent flow in narrow solid fuel ducts. To clarify this mechanism, two experiments were conducted. The first experiment was to investigate the influence of ambient pressure and fuel duct size on the blowoff limit. The results indicated that the flow velocity at the point when blowoff occurred, V-g,V-t, increased with ambient pressure. This tendency could not be confirmed by a well-known expression for the Damkohler number, which is defined as the ratio of the characteristic flow time to the characteristic chemical time. Subsequently, to clarify the determining factor for the blowoff, the second experiment, which observed the flow field near the flame leading edge, was conducted. The results show that the flow separation in front of the flame leading edge, which provided sufficient residence time of oxidizer and gaseous fuel, is necessary for the flame to spread in an opposed oxidizer flow. From the results, it is found that the oxidizer friction velocity, u(*), which is an indicator of the turbulent momentum transfer, is the determining factor for the flame blowoff limit. When the friction velocity is larger than a critical value, flame blowoff occurs in the fuel duct, due to the absence of flow separation. (c) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
  • N Hashimoto, S Watanabe, H Nagata, T Totani, Kudo, I
    PROCEEDINGS OF THE COMBUSTION INSTITUTE 29 1 245 - 250 2003年 [査読有り][通常論文]
     
    The influence of channel height on flame spread in a circular duct of the solid fuel in an opposed-flow configuration was examined. Polymethylmethacrylate cylinders with a circular duct (diameter of 1, 2, or 3 mm) were used as fuel specimens, and both flame-spreading and stabilized combustion were observed. In the case of stabilized combustion, the flame cannot spread into the duct because of the high oxygen velocity The flame-traveling velocity is the velocity at which the flame widens the duct by fuel consumption. Therefore, the flame-traveling velocity in stabilized combustion is significantly low compared with flame-spreading combustion. In the case of flame-spreading combustion, the equivalence velocity, which contains channel height information, defines whether the regime is the thermal or the chemical regime. When the equivalent velocity is higher than a certain value, the flame-spread rate is controlled by chemical effects. On the whole, the flame-spread rate decreases with the decrease of channel height in the case of flame-spreading combustion because of the curvature effect. Owing to the curvature effect, the area ratio of the flame to that of the solid surface decreases with decreasing channel height, and this is conspicuous when the channel height is low. The curvature effect is negligible when the channel height is sufficiently large compared with the flame stand-off distance.
  • 加藤 隆博, 橋本 望, 永田 晴紀, 工藤 勲
    日本航空宇宙学会論文集 = Journal of the Japan Society for Aeronautical and Space Sciences 49 565 33 - 39 一般社団法人 日本航空宇宙学会 2001年02月05日 [査読有り][通常論文]
     
    To overcome defects of conventional hybrid rockets such as low combustion efficiency and the O/F shift during the combustion, the authors have proposed a new form of hybrid rocket fuel. The fuel is a fibrous bed in which oxidizer gas flows. Stable diffusion flame appears at the exit surface. Previous researches show that sudden increase of the fuel regression rate occurs with the increase of ambient pressure. This sudden increase is attributed to the flame spreading between fuel fibers. To clarify the limit of fuel gap space the diffusion flame can spread into, experimental study was made. Critical gap space, which means the minimum gap space the diffusion flame can spread into, was obtained experimentally as a function of oxygen gas flow velocity and ambient pressure. Using this result, necessary conditions to realize a stable combustion with this new fuel form are shown.
  • 橋本 望, 加藤 隆博, 永田 晴紀, 工藤 勲
    日本航空宇宙学会論文集 = Journal of the Japan Society for Aeronautical and Space Sciences 49 565 40 - 47 一般社団法人 日本航空宇宙学会 2001年02月05日 [査読有り][通常論文]
     
    To overcome defects of conventional hybrid rockets such as the loss of specific impulse, which is caused by the O/F shift during the combustion, and the low combustion efficiency, the authors have proposed a new idea of design. The point of this idea, named “End-Burning Hybrid Rocket, ” is that oxidizer gas flows in the gap space of a porous solid fuel bed. Diffusion flame is formed at the end of the solid fuel bed. Experimental studies were made to clarify the basic combustion characteristics of the propellant. Results show that pressure exponent of the burning rate with the same equivalence ratio is approximately 0.85 and virtually independent with the equivalence ratio. Using this result, a designing method of End-Burning Hybrid Rocket Motor is shown. Finally, thrust and specific impulse is estimated as functions of oxidizer gas flow rates to investigate the throttling characteristics of the motor.

その他活動・業績

特許

受賞

  • 2019年11月 日本燃焼学会 「美しい炎」の写真展優秀作品賞
     Discoloring sunflower 
    受賞者: 郭 峰;尾崎 悠;橋本 望;藤田 修
  • 2018年04月 日本機械学会 日本機械学会賞(論文)
     Primary soot particle distributions in a combustion field of 4 kW pulverized coal jet burner measured by time resolved laser induced incandescence (TiRe-LII) 
    受賞者: 橋本 望
  • 2017年11月 日本燃焼学会 日本燃焼学会論文賞
     Microgravity experiments of fuel droplet evaporation in sub- and supercritical environments 
    受賞者: 橋本 望
  • 2017年10月 粉体工学会 技術賞
     微粉炭燃焼場でのすす生成特性解明に向けた計測技術 
    受賞者: 橋本 望
  • 2017年06月 12th International Symposium on Fire Safety Science Honorable Mentions
     Dripping Behaviors of Melted Insulation in Wire Fire under Opposed Flow 
    受賞者: 小林芳成;金野佑亮;Xinyan Huang;中谷辰爾;津江光洋;橋本望;藤田修;Carlos Fernandez-Pello
  • 2016年11月 日本燃焼学会優秀作品賞 日本燃焼学会優秀作品賞
     オリンピック聖火 
    受賞者: Taejoon NOH;Sunghwan YOON;小山陽一郎;橋本望;藤田修
  • 2013年12月 日本燃焼学会 日本燃焼学会奨励賞
     微粉炭燃焼場におけるレーザ計測と数値シミュレーションの高度化に関する研究 
    受賞者: 橋本 望
  • 2012年04月 日本機械学会 日本機械学会奨励賞(研究)
     微粉炭燃焼の数値シミュレーションにおける詳細揮発分放出モデルの研究(研究奨励第429号) 
    受賞者: 橋本 望
  • 2008年09月 化学工学会 熱工学部会 2008年度 化学工学会 熱工学部会賞
     粒子昇温速度を考慮した揮発分放出モデル(TDP model)を用いた微粉炭燃焼場の数値計算 
    受賞者: 橋本 望
  • 2005年10月 The 6th International Symposium & Exhibition on Gas Cleaning High Temperatures 優秀論文賞(細川賞)
     Application of Percolation Model to Particulate Matter Formation in Pressurized Coal Combustion 
    受賞者: 黒瀬良一;牧野尚夫;橋本望;鈴木朗

共同研究・競争的資金等の研究課題

  • 固体燃料とガス燃料混焼時の相互作用メカニズムの解明とモデル構築
    日本学術振興会:科学研究費補助金 基盤研究(B)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 橋本 望
  • ガス・燃料流動の気液二相流のサイクル変動
    自動車技術組合(AICE)および経産省:2019年度プロジェクト研究(CAE要素研究)
    研究期間 : 2019年04月 -2021年03月 
    代表者 : 高木 正英
  • 高精度かつ計算コストの低い多成分燃料液滴蒸発モデルの開発
    東燃ゼネラル石油研究奨励・奨学財団:第38回研究奨励助成
    研究期間 : 2019年04月 -2020年03月 
    代表者 : 橋本 望
  • 水素の混焼による微粉固体燃料の燃焼促進に関する研究
    ホソカワ粉体工学振興財団:平成30年度研究助成
    研究期間 : 2019年04月 -2020年03月 
    代表者 : 橋本 望
  • エネルギーキャリアガスと天然ガスの乱流混焼特性に関する研究
    北海道ガス株式会社:平成30年度北海道ガス大学研究支援制度
    研究期間 : 2018年04月 -2019年03月 
    代表者 : 橋本 望
  • エネルギーキャリアとしてのアンモニア普及へ向けた難燃性固体燃料とアンモニアの混焼による着火特性改善効果の解明
    科学技術振興機構:さきがけ
    研究期間 : 2015年10月 -2019年03月 
    代表者 : 橋本 望
  • カーボンフリーエネルギーキャリア利用における科学と技術
    東北大学流体科学研究所:平成29年度重点公募研究
    研究期間 : 2017年11月 -2018年03月 
    代表者 : 小林 秀明
  • ガス燃料の酸素燃焼における燃料・酸化剤・希釈剤の最適混合方法の解明
    一般財団法人パロマ環境技術開発財団:平成28年度研究助成
    研究期間 : 2017年04月 -2018年03月 
    代表者 : 橋本 望
  • 低品位固体燃料を対象とした高精度燃焼数値シミュレーション技術の開発
    日本ボイラ協会:平成29年度ボイラー・圧力容器等研究助成
    研究期間 : 2017年04月 -2018年03月 
    代表者 : 橋本 望
  • 高温気流中に吹き込まれる固体燃料粒子の挙動に関する研究
    日本鉄鋼協会:第25回鉄鋼研究振興助成
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 橋本 望
  • バイオマス由来液体燃料の蒸発特性の解明と数値解析用モデル構築
    スズキ財団:平成27年度科学技術研究助成
    研究期間 : 2016年04月 -2017年03月 
    代表者 : 橋本 望
  • 固体燃焼場における粒子状物質(PM)生成・酸化プロセスのモデリング
    日本学術振興会:科学研究費補助金 若手(B)
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 橋本 望
  • 微粉炭粒子の着火プロセスの解明と混相乱流燃焼モデリング
    日本学術振興会:科学研究費補助金基盤研究(C)
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 渡邊 裕章
  • CO2回収型次世代IGCC技術開発
    新エネルギー・産業技術総合開発機構:革新的ゼロエミッション石炭ガス化発電プロジェクト/ゼロエミッション石炭火力基盤技術開発/革新的ガス化技術に関する基盤研究事業
    研究期間 : 2008年04月 -2014年02月 
    代表者 : 原三郎
  • Research on Flame Spread over Solid Fuel Surface
  • Study on End-Burning Hybrid Rocket

教育活動情報

主要な担当授業

  • Advanced Combustion(燃焼学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 : chemical reaction, combustion, analysis, theory
  • 燃焼学特論
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 工学院
  • Advanced Combustion(燃焼学E)
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
  • 燃焼学特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
  • CAD・CAM演習
    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 : 機械製図法,工業規格,立体図
  • 設計演習Ⅰ
    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 : 機械製図法,工業規格,立体図,強度設計

大学運営

委員歴

  • 2019年08月 - 現在   日本燃焼学会   令和元年度先進的燃焼技術の調査研究委員会「水素・アンモニア」「固体燃焼」委員
  • 2019年04月 - 現在   日本機械学会   熱工学コンファレンス2020 幹事
  • 2018年10月 - 現在   日本燃焼学会   第57回燃焼シンポジウム実行委員会 庶務幹事
  • 2018年07月 - 現在   日本機械学会   動力・エネルギー技術シンポジウム OS次世代エネルギーシステム技術 オーガナイザー
  • 2017年04月 - 現在   日本航空宇宙学会   北部支部 幹事
  • 2017年01月 - 現在   日本液体微粒化学会   会誌委員会委員
  • 2015年07月 - 現在   国立教育政策研究所   チューニングによる大学教育のグローバル質保証 テスト問題バンクの取組<工学分野> WG委員
  • 2013年04月 - 現在   化学工学会   エネルギー部会炭素系資源利用分科会 幹事
  • 2018年06月 - 2019年07月   Asia-Pacific Conference on Combustion   Colloquium Chair (Stationary Combustion Systems and Control of Greenhouse Gas Emissions)
  • 2017年07月 - 2019年06月   日本燃焼学会   将来構想・研究戦略研究分科会 幹事
  • 2018年08月 - 2019年03月   日本燃焼学会   平成30年度調査研究委員会「固体燃焼」「燃焼解析プラットフォーム」委員
  • 2017年04月 - 2019年03月   日本機械学会北海道支部   会計幹事
  • 2017年03月 - 2018年09月   日本伝熱学会   第55回伝熱シンポジウム実行委員
  • 2017年06月 - 2018年05月   日本伝熱学会   第55回電熱シンポジウム OS燃焼研究の最前線 オーガナイザー
  • 2017年06月 - 2018年03月   日本燃焼学会   先進的燃焼技術の調査研究「固体燃焼」小委員長
  • 2015年06月 - 2018年03月   日本燃焼学会   産学連携研究事業 燃焼解析プラットフォーム開発・検証 WG 委員
  • 2014年04月 - 2018年03月   日本機械学会   熱工学部門運営委員会 委員
  • 2016年04月 - 2017年03月   日本機械学会北海道支部   学生会 顧問
  • 2015年04月 - 2017年03月   日本航空宇宙学会   宇宙利用部門委員会 部門委員
  • 2015年11月 - 2016年12月   11th Asian Microgravity Symposium (AMS2016)   Organizing Committee menber
  • 2015年10月 - 2016年03月   日本燃焼学会   先進的燃焼技術の調査研究 「固体燃焼・ガス化」小委員長
  • 2015年01月 - 2015年12月   日本機械学会   2015年度年次大会 実行委員会 委員
  • 2012年04月 - 2014年03月   日本機械学会   校閲委員
  • 2012年12月 - 2013年12月   日本燃焼学会   第51回燃焼シンポジウム 実行委員
  • 2009年04月 - 2013年03月   化学工学会   エネルギー部会 幹事
  • 2011年12月 - 2012年03月   日本燃焼学会   平成23年度調査研究委員会 委員
  • 2000年04月 - 2000年09月   日本機械学会   北海道学生会2000年度上期幹事


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