Research Projects -
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Prediction of Instantaneous wall shear stress distribution through the fusion of Experimental/Computational/Data-driven Fluid Dynamics
Grant number：22K18302 2022.06 - 2025.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Pioneering) Grant-in-Aid for Challenging Research (Pioneering)
河内 俊憲, 田中 健人
Grant amount：\25870000 （ Direct expense: \19900000 、 Indirect expense：\5970000 ）
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高レイノルズ数空力予測の精度向上を目指した衝撃波/境界層干渉の先進画像計測
Grant number：22H01684 2022.04 - 2026.03
日本学術振興会 科学研究費助成事業 基盤研究(B) 基盤研究(B)
河内 俊憲, 鈴木 博貴, 田中 健人
Grant amount：\17420000 （ Direct expense: \13400000 、 Indirect expense：\4020000 ）
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Mechanism of Transonic Buffet for A Swept Wing Revealed by Advanced Fluid Measurements
Grant number：18H03814 2018.04 - 2022.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
Kouchi Toshinori
Grant amount：\44200000 （ Direct expense: \34000000 、 Indirect expense：\10200000 ）
We conducted a series of the wind tunnel experiments focused on a shock wave-boundary layer interaction inducing a transonic buffet which determines capability of a flight in a high-speed region. Wing model had a 10°sweep angle and a cross section of NASA common research model, which is a simplified model for a commercial aircraft wing. Through this work, we newly developed a dual layer focusing schlieren system to take flow information with several tens of kHz frame rate. We combined this system with unsteady pressure sensitive paint (uPSP) measurement system which take wall information with several kHz frame rate, to measure the flow-field both around the wing and on the wing surface. We successfully measured flow and wall information for the buffet with high spatiotemporal resolution in being the first in the world. Based on these data, we obtained new knowledge on the generation and maintenance of the self-oscillation of the shock wave for the swept wing.
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Development of Unsteady Velocity Measurement using Afterglow of an Image Intensifier
Grant number：17K18938 2017.06 - 2019.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory) Grant-in-Aid for Challenging Research (Exploratory)
Kouchi Toshinori
Grant amount：\6370000 （ Direct expense: \4900000 、 Indirect expense：\1470000 ）
Unsteady velocity measurements in supersonic flows is very challenging topics. I developed new measurement system which is able to measure unsteady velocity using a continuous laser light and an image intensifier. First, I applied the measurement system to low speed wind tunnel experiments to confirm that my new idea is correct or not. The present data well agreed with the previous ones. Therefore, I conclude that my new measurement system has an enough potential to measure unsteady velocity-field. However, the developed system cannot measure the velocity in supersonic flow, because measurement uncertainty became increased compared to that in the low speed experiments. Unfortunately, I cannot improve this within the term of this project. In addition to confirm my idea being correct, I developed new generation method of tracer particle using velocity measurement. This particle has potential to reveal much detail flow structure in highly turbulent flows.
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Two-color PLIF Measurement of Instantaneous Molar Fraction in A Supersonic Combustor
Grant number：15H04199 2015.04 - 2018.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
Kouchi Toshinori
Grant amount：\16380000 （ Direct expense: \12600000 、 Indirect expense：\3780000 ）
Spaceplane is a promising candidate for next generation space transportation system. Supersonic mixing and combustion are keys to realize the spaceplane. We developed a new technique to measure instantaneous injectant molar fraction in a supersonic flow through this project. The measurement technique is based on Planner Laser Induced Fluoresces (PLIF) using tracer molecules which are excited by laser light. To establish the technique, we first investigated photochemical characteristics of toluene under low-temperature and pressure conditions which is observed in a suction-type supersonic wind tunnel. Then, we established the two-color PLIF measurement system. By using this new measurement system, we are able to quantitatively evaluate mixing efficiency of fuel in a supersonic flow.
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Grant number：24656512 2012
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research Grant-in-Aid for Challenging Exploratory Research
MASUYA Goro, TAKITA Kenichi, KOUCHI Toshinori
Grant amount：\4030000 （ Direct expense: \3100000 、 Indirect expense：\930000 ）
Fast mixing of fuel and air is one of the most important technical subjects to realize hypersonic air breathing engines. In order to measure instantaneous distribution of fuel mole fraction, we tried to develop a new technique using laser induced fluorescence signals of two tracer gases. We investigated fluorescent characteristics of several candidate matters and selected acetone and toluene as the tracer gas. We tested fluorescent characteristics of their mixture in air and other gases.
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Investigation of Mixing Mechanism in A Scramjet Combustor Using Combined PIV-LIF Measurement System
Grant number：23360377 2011.04 - 2014.03
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
KOUCHI Toshinori, MASUYA Goro, TAKITA Kenichi, TOMIOKA Sadatake
Grant amount：\19110000 （ Direct expense: \14700000 、 Indirect expense：\4410000 ）
Scramjet engine is one of the promising candidates as a propulsion system for hypersonic flight vehicles and space planes. We developed a combined stereoscopic Particle Image Velocimetry (PIV) and acetone Planar Laser Induced Fluoresce (PLIF) measurement system, to evaluate turbulent eddy diffusion flux in the combustor, which physically means the averaged transport due to turbulent fluctuations. We applied this measurement system to a transverse jet in a Mach 2 supersonic flow with/without pseudo shock wave, simulating the scramjet combustor. The system successfully measured the eddy flux in the flowfield. These quantitative data provided insight into the fundamental physics of the supersonic mixing.
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平衡／非平衡プラズマの併用による超音速流中での着火・燃焼促進
Grant number：23360375 2011.04 - 2014.03
日本学術振興会 科学研究費助成事業 基盤研究(B) 基盤研究(B)
滝田 謙一, 升谷 五郎, 河内 俊憲
Grant amount：\18460000 （ Direct expense: \14200000 、 Indirect expense：\4260000 ）
本研究は，平衡（熱）プラズマと非平衡（低温）プラズマの併用により極めてエネルギ効率の高い着火・燃焼促進技術の新規開発を目的とする。平成24年度は ①平衡／非平衡プラズマを併用した着火システムによる着火・燃焼実験，②プラズマ及び火炎の光学計測，③プラズマ反応のモデリング，④３次元燃焼解析コードを用いたプラズマ着火の数値シミュレーション の実施を計画し，以下の成果を得た。
①については，プラズマジェット（PJ)トーチと誘電体バリア放電（DBD）を併用した着火システムを用いて，水素及び炭化水素を燃料とする着火・燃焼実験を行った。その結果，水素燃料についてはDBD装置の併用による着火促進効果が見られた。しかしスクラムジェットの代表的な炭化水素燃料であるエチレンに対しては，目立った着火促進効果を捉えることができなかった。
②については今年度は実施しなかった。
③については，空気中でDBD装置を作動させた場合に，多く生成されることが知られているオゾンを燃焼機構に加えて着火遅れ時間の解析を行い，上記①で観測されたエチレン燃料に対してDBD装置を併用しても着火促進効果がほとんど見られない原因を探った。
④については水素燃料について，DBD装置の作動を模擬するオゾン添加を行う領域とオゾン添加濃度を変化させた計算を行った。その結果，断面全域に平均的にオゾンを加えた場合と同等の着火促進効果を，噴射孔側の壁面付近に集中的にオゾンを供給することができ，より効率的にオゾンの着火促進効果を得られることを見出した。 -
Investigation of Mixing Enhancement Mechanism Caused by Pseudo-Shock Wave
Grant number：20360081 2008 - 2011
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
MASUYA Goro, TAKITA Kenichi, KOUCHI Toshinori
Grant type：Competitive
Grant amount：\19890000 （ Direct expense: \15300000 、 Indirect expense：\4590000 ）
Mixing of fuel injected into supersonic internal flow with a pseudo-shock wave, which appears in the combustor of a dual-mode ramjet engine, is significantly and non-isotropically improved. In order to clarify the mechanism of this mixing enhancement, injectant concentration and velocity distributions were measured using a particle image velocimetry (PIV)and a planar laser-induced fluorescence (PLIF), respectively. In addition, numerical simulations were carried out to understand the flowfield. As a result, we found that the pseudo-shock wave produced strong turbulence near the wall and it enhanced mixing of the jet.
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Enhancement of Fuel Mixing and Jet Penetration using Pulsed Injection into a Supersonic Flow
Grant number：20760105 2008 - 2010
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B) Grant-in-Aid for Young Scientists (B)
KOUCHI Toshinori
Grant type：Competitive
Grant amount：\4290000 （ Direct expense: \3300000 、 Indirect expense：\990000 ）
This research experimentally and numerically investigated the penetration characteristics of the pulsed injection into Mach 2 supersonic crossflow. This research revealed the pulsed jet penetration in a rising phase of injection pressure was higher than that in a declining phase of injection pressure at a certain value of injection pressure. This hysteresis was owing to the upward flow produced by the pulsed jet like a slug which inclined toward the injection wall. The numerical simulations revealed the vortex rings was generated in each pulse cycle. They dominated the jet penetration and promoted mixing of the injectant with crossflow-air. Based on these experimental and numerical results, we conclude that the pulsed injection could control the jet penetration and mixing by changing its frequency.
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Ignition and Combustion Enhancement by non-equilibrium plasma in supersonic flow
Grant number：20360378 2008 - 2010
Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B) Grant-in-Aid for Scientific Research (B)
TAKITA Kenichi, MASUYA Goro, KOUCHI Toshinori
Grant amount：\18720000 （ Direct expense: \14400000 、 Indirect expense：\4320000 ）
The generation method of non-equilibrium plasma by dielectric barrier discharge(DBD)in a supersonic flow was established. Excited nitrogen molecules and oxygen radicals, which were suitable for ignition and combustion enhancement, were detected by a spectroscopic measurement. The effects of applied voltage and frequency in discharge on the generation of non-equilibrium plasma were clarified and the electric energy for generation of the plasma was estimated. Moreover, efficient discharge conditions for radical generation were theoretically supposed.
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スクラムジェットエンジン内部形状の最適化
Grant number：03J07299 2003 - 2005
日本学術振興会 科学研究費助成事業 特別研究員奨励費 特別研究員奨励費
河内 俊憲
Grant amount：\1700000 （ Direct expense: \1700000 ）
極超音速飛行するスペースブレーン用のエンジンとして有望視されている,スクラムジェットエンジン内壁におけるレイノルズアナロジーの妥当性を,数値計算を用いて定量的に議論し,その適用限界を調べた.その結果±10%程度の範囲で,エンジン内壁のおよそ90%でレイノルズアナロジーが適用できることが分かった.そこで,このレイノルズアナロジーを組み込んだ一次元解析により,いくつかのエンジン形状と飛行条件について熱負荷や冷却要求を調べた.例えばストラット付きエンジンでは,マッハ8飛行条件において,エンジン平均熱流束は燃焼時に0.5MW/m2となり,冷却に必要な水素流量は,燃焼用の燃料流量と同程度になることが分かった.従って,今後エンジンの作動マッハ数域を広げるには,冷却要請のおよそ80%を占める燃焼器においてフィルム冷却を行ったり,形状を最適化していく必要がある.
マッハ6飛行条件のストラット付きスクラムジェットエンジンと,そのエンジンの燃焼器の一部を切り出したセクター燃焼器モデルに対して反応流計算を行い,エンジン内の火炎形状が,燃焼性能をどのように決定しているのか,またインレットの偏流が燃焼性能に対してどのような影響を与えているかを考察した.その結果,インレットの偏流により,燃料の大規模な合体が生じ,燃焼効率の増加が著しく抑制されていることが分かった.従って,今後エンジン性能を改善していくには,燃料噴流の合体を防ぐために,燃料噴射孔間隔の最適化を図ること,特にインレットを最適化し,カウル衝撃波による境界層内の二次流を低減していく必要がある.また数値計算で得られた,エンジン内の火炎構造と燃焼効率分布を比較することで,供試エンジンでも,ストラット壁側からの垂直噴射,ストラットベース面・カウル側からの平行噴射を行えば、燃焼性能を改善しうることが分かった.