研究者詳細 - 坪井　伸幸

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Effects of a Recess on Coaxial Cryogenic Injections at Supercritical Pressure 査読有り国際誌

Muto D., Terashima H., Araki T., Tsuboi N.

Journal of Propulsion and Power 38 ( 4 ) 581 - 591 2022年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Effects of recess lengths on coaxial cryogenic jets under a supercritical pressure are numerically studied. A hybrid large-eddy simulation/Reynolds-averaged Navier–Stokes methodology is applied to capture unsteady jet behaviors of recessed injectors. For the injector with a moderate recess length, the dense-core length of the inner jet is shorter than that with a nonrecessed injector, demonstrating that recessing improves the mixing. The flowfields show that the vortex structures in an inner mixing layer are strongly developed within the recessed region, and the entrainment of the outer jet into the inner jet is strengthened. However, a further increase in the recess length turns to the increase of the dense-core length and deteriorates the inner jet decay along the centerline. This deterioration is caused by the separation of the outer jet flow on the wall in the recessed region. The turbulence generation in the outer mixing layer is suppressed because of the separation, resulting in less enhancement of the mixing in the downstream region. Therefore, the study demonstrates that there is an approximate recess length for optimum jet mixing. Finally, a correlation relationship is provided between the dense-core length and the momentum flux ratio from a comprehensive comparison of existing experimental and numerical data.

DOI： 10.2514/1.B38552

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Difference between 2D and 3D NS calculations for RDE pressure gain 査読有り国際誌

Hayashi A.K., Nihonmatsu R., Ito T., Tsuboi N., Ozawa K., Otsuka Y., Ishii K.

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025 2025年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

RDE pressure gain (PG) analyses by NASA group in 2018 show that PG is one of the evaluations for RDE performance problems by comparing experimental data. Our groups (Hayashi, Tsuboi, and Ishii) have started the evaluation of RDE by PG from 2022 and presented our first results in AIAA SciTech 2023, January which can improve the PG value. The present presentation will provide what can affect a big and positive value to PG value through numerical analyses.

DOI： 10.2514/6.2025-1398

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Correction: [3D Numerical Simulation on Disk Type RDE used Hydrogen-Air Premixed Gas and Non-premixed Gas with Multi-Ports Injection] (American Institute of Aeronautics and Astronautics Inc, AIAA) 査読有り国際誌

Ito T., Tsuboi N., Ozawa K., Hayashi A.K.

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025 2025年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Correction Notice A. Comparison of propagation transition ・No.1: Before Figure 4 shows the temperature contours of the instantaneous field for each case. case 1 and case 2, which are nonpremix cases, show more unburned gas pockets than the premix case. Another feature of the non-premix case is the presence of a thin high-temperature region on the wall behind the wavefront. Figure 5 shows the time history of pressure at the outer wall. The vertical axis is the circumferential angle and the horizontal axis is time. The detonation propagation frequency was read from this pressure history, and Case 1 to Case 3 were in an overdriven state with respect to the cj velocity. In the case4, the propagation velocity was 4% lower than the cj velocity because of three wavefronts. This is due to the pressure drop caused by the increased number of propagating wavefronts [12]. After Figure 4 shows the temperature contours of the instantaneous field for each case. In Case 1, although a clear plane wave is not generated, a small area on the outer surface contains a high-temperature and high-pressure region. Case 2 also does not produce a plane wave, and many pockets of unburned gas are observed. In Case 3, the detonation wave is flat, and a high-temperature region is also observed in the oblique shock wave area on the radial side. In Case 4, the premixed gas inflow was large, resulting in a three-wave front. Figure 5 shows the time history of pressure at the outer wall. The vertical axis is the circumferential angle, and the horizontal axis is time. The detonation propagation velocity read from this pressure history is shown in Figure 6. Case 4 has three wavefronts, so the propagation velocity is 4% lower than the CJ velocity. This is due to the pressure drop caused by the increased number of propagating wavefronts [12]. The reason for this is that the geometry of the DRDE causes the shock waves to hit curved surfaces, and the overlapping of the shock waves creates a high-pressure zone on the wall surface. ・No.2 Add the following figure (Figure presented).

DOI： 10.2514/6.2025-1974.c1

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3D Numerical Simulation on Disk Type RDE used Hydrogen-Air Premixed Gas and Non-premixed Gas with Multi-Ports Injection 査読有り国際誌

Ito T., Tsuboi N., Ozawa K., Hayashi A.K.

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025 2025年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

A three-dimensional viscosity simulation of a rotating disk detonation engine (DRDE) using the Navier-Stokes equations with the UT-JAXA reaction mechanism for H2-air Premix and Non-premix gas is presented. The purpose of this study is to visualize the propagation pattern in the DRDE combustor, to investigate the effect of the injection method on the propagation pattern, and to evaluate its impact on stable detonation propagation and DRDE performance. The results show that the injection method affects the generation of new detonation waves, that the injection method has no significant effect on the Pressure Gain, and that DRDEs have comparable performance in Pressure Gain compared to RDEs.

DOI： 10.2514/6.2025-1974

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Two-dimensional detailed numerical simulation of ammonia/hydrogen/air detonation: hydrogen concentration effects and transverse detonation wave structure 査読有り国際誌

Kohama S., Ito T., Tsuboi N., Ozawa K., Hayashi A.K.

Shock Waves 34 ( 2 ) 139 - 154 2024年04月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Numerical simulations on ammonia/hydrogen/air detonation are performed using a detailed reaction model to investigate the cellular instability and detonation dynamics as a function of hydrogen content. The UT-LCS model that includes 32 species and 213 elementary reactions is used in the present simulations. The fifth-order target compact nonlinear scheme captured the unstable detonation dynamics and the complicated flow structure including the propagation of a sub-transverse wave. The simulation performed with different hydrogen dilutions shows that the detonation propagates at the Chapman–Jouguet velocity for all cases, and the cell size for the ammonia/hydrogen mixing ratio α=0.3 becomes approximately 10 times larger than that for α=1.0 (hydrogen/air mixture). A transverse detonation produces a finescale cellular structure on the computed maximum pressure history. This complex shock formation is similar to those of a spinning detonation and two-dimensional propane/oxygen detonation. The cellular irregularity increases with decreasing hydrogen content because ammonia destabilizes the detonation cellular structure with a reduced activation energy of more than approximately 8.

DOI： 10.1007/s00193-024-01181-6

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Study of Nozzle Choking Effect on Pressure Gain of Disc Rotating Detonation Engine 査読有り国際誌

Hayashi A.K., Otsuka Y., Ishii K., Ito T., Tsuboi N., Ozawa K.

AIAA SciTech Forum and Exposition, 2024 2024年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The present study performs the disc-type rotating detonation engine experiments for the various mass flow with the various nozzle configuration ratio of A8/A3,2, where A3,2 and A8 denote the air slit and the nozzle exit area, respectively. The pressure gain is evaluated based on the equivalent available pressure determined from the measured thrust and the air-prenum pressure. As a results, regardless of the value of A8/A3,2, Equivalent available pressure (EAP) increases monotonically with the increase of the mass flow rate. However, for the same mass flow rate, the EAP for A8/A3,2=0.2 is about three times larger than that for A8/A3,2 =0.6 and 0.8. For A8/A3,2 = 0.2, the mass flow rate and pressure gain are positively correlated and the naximum pressure gain of -0.19 is obtained at the mass flow rate of 278 g/s. For A8/A3,2= 0.6 and 0.8, the pressure gain show a decreasing trend with increasing mass flow rate. The effect of A8/A3,2 on the pressure gain is found to responsible for the flow choking in the air slit of the combustion chamber.

DOI： 10.2514/6.2024-1034

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Two-Dimensional Detailed Numerical Simulation on Ammonia/Hydrogen/Air Detonation : Hydrogen dilution effects and sub-transverse wave structure in transverse detonation 査読有り国際誌

Shui Kohama, Nobuyuki Tsuboi, Kouhei Ozawa, Koichi A Hayashi

29th International Colloquium on the Dynamics of Explosions and Reactive Systems Papaer 176 2023年07月

Analysis on Pressure Gain of Rotating Detonation Engine 査読有り国際誌

A. K. Hayashi, Y. Otsuka, K. Ishii, K. Yoshidomi, T. Ito, N. Tsuboi, K. Ozawa

The 34th International Symposium on Shock Waves T04-0282 2023年07月

Effects of Reynolds Number and Ramp Angle on Gortler Vortices over a Compression Ramp 査読有り国際誌

Kalash Dixit, Ritu Raj Kumar, Nagabhushana Rao Vadlamani, Nobuyuki Tsuboi

The 34th International Symposium on Shock Waves T19-0135 2023年07月

Numerical Simulation on DDT in Real and Large Scale Combustion Chamber Using a Combustion Velocity Model and Ignition Model with a Detailed Chemical Reaction System 査読有り

Ichiro Nakamori, Takayuki Tomizuka, Atsuo Takahashi, Fumitomo Onishi, Mikhail Kuznetsov, Takashi Kodama, Yoshikazu Tamauchi, Naoya Sato, A. Koichi Hayashi and Nobuyuki Tsuboi

29th International Colloquium on the Dynamics of Explosions and Reactive Systems Paper 127 2023年07月

Detailed Numerical Simulation on Dimethyl Ether/Oxygen Premixture Detonation Using Reduced Chemical Reaction Model -Disturbance of Cellular Structure- 査読有り国際誌

Kubota Daiki, Tsuboi Nobuyuki, Ozawa Kohei, Hahashi A. Koichi

29th International Colloquium on the Dynamics of Explosions and Reactive Systems Paper 193 2023年07月

Operation characteristics of a disk-type rotating detonation engine 査読有り国際誌

Ishii K., Ohno K., Kawana H., Kawasaki K., Hayashi A.K., Tsuboi N.

Shock Waves 33 ( 3 ) 267 - 274 2023年04月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

In the present work, operation characteristics of a disk-type rotating detonation engine (DRDE) with a constant chamber area were experimentally studied for various total mass flow rates and a wide variety of equivalence ratios of hydrogen–air mixtures. From the direct visualizations, the rotating detonation wave was found to propagate near the outer wall of the combustion chamber, regardless of the wave mode. For the present test conditions, single- and double-wave modes are observed, depending on the equivalence ratio of the mixture. The pressure gain was evaluated based on a one-dimensional flow model together with the chamber static pressure measured with the capillary tube average pressure technique. Although the present DRDE configuration provided a negative pressure gain for all the test conditions, it was found that the single-wave mode was superior to the double-wave mode in terms of the pressure gain.

DOI： 10.1007/s00193-023-01133-6

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Influence of tube cross-section geometry on high-pressure hydrogen-flow-induced self-ignition 査読有り国際誌

Asahara M., Yokoyama A., Tsuboi N., Hayashi A.K.

International Journal of Hydrogen Energy 48 ( 21 ) 7909 - 7926 2023年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

Self-ignition within a cylindrical tube that discharges high-pressure hydrogen results in flame formation. Because rectangular tubes are used to visualize fuel-flow dynamics, the influence of the tube cross-section on the self-ignition characteristics is investigated. As experimental investigation of the mechanisms underlying the self-ignition phenomenon in cylindrical tubes is difficult, three-dimensional numerical simulation is employed. Following the bursting of diaphragm by high-pressure hydrogen with a storage pressure of 9.0 MPa and a temperature of 300 K, initial self-ignition occurs at the center of the rectangular tube sidewall. This is because of the mixing of air and hydrogen induced by the bow-shock reflection-generated jet flow and resulting adiabatic shock compression-induced temperature increase. This temperature rise induces a secondary self-ignition at the tube corners. In the cylindrical tube, a solitary ring-shaped self-ignition occurs near the sidewall. The flame evolutions in rectangular and cylindrical tubes reveal similar flame-spreading trends, which indicates similar bow-shock reflection-induced self-ignition mechanisms.

DOI： 10.1016/j.ijhydene.2022.08.210

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Numerical Study of Cryogenic Hydrogen Jet in Crossflow under Supercritical Pressure: Comparison of Tandem and Twin Jets 査読有り国際誌

NAKATSUKASA Tomohito, AMANO Taishi, ARAKI Takahide, TERASHIMA Hiroshi, TSUBOI Nobuyuki, OZAWA Kohei

Journal of Evolving Space Activities ( 宇宙技術および科学の国際シンポジウム ) 1 ( 0 ) n/a 2023年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

The present study numerically investigates the flow fields of the twin- and tandem-jet in crossflow (JIC) under supercritical pressure. An ILES/RANS method is applied. In the present JIC, cryogenic hydrogen jets are vertically injected to warm temperature hydrogen crossflow through circular injector holes. The results show that the penetration of cryogenic jets into the crossflow is more enhanced with the tandem-jet than with the twin-jet. The higher jet penetration with the tandem jets is caused by a downstream jet behavior less influenced by the crossflow. Nevertheless, a mixedness analysis indicates that the mixing state at a downstream position is almost similar between the tandem and twin jets.

DOI： 10.57350/jesa.29

Visualization of the physical destruction process of additive-manufactured regression sensor structures 査読有り国際誌

Ozawa Kohei, Neki Tomoya, Tsuboi Nobuyuki

Science and Technology of Energetic Materials ( 一般社団法人火薬学会 ) 84 ( 2 ) 24 - 31 2023年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Advanced closed-loop control of thrust and mixture ratio of hybrid rockets can be realized by combing a fuel mass flow rate control technique with a real-time fuel regression measurement. One of the promising techniques to realize real-time fuel regression measurement is the multi-material-additive-manufactured solid fuel with an integrated sensor probe structure. In this work, the destruction process of its regression sensor structure was visualized by the high-speed video from the top view of the sensor structure. The acquired high-speed video revealed the destruction process and its relationship with the time history of the voltage on the sensor structure. One of the findings is that unevenness or bumps of the rung form hot spots with strong emission, leading to the dropping-off and entrainment of the fragmented rung into the diffusion flame. Another important finding is that the destruction process of the rung starts before the rapid voltage increase, but it precedes the more intensive and frequent destruction. The post-processing of the sequential frames of the high-speed video successfully provided the observation of the fuel surface behind the diffusion flames. These reconstructed videos visualized the motions of the fragmented rung remaining on the fuel surface. The physical destruction process of the regression sensor structure revealed in this study can contribute to the improvement of the sensor structure design to avoid the unexpected off-nominal responses previously observed.

DOI： 10.34571/stem.84.2_24

Validation of Soave–Redlich–Kwong equation of state coupled with a classical mixing rule for sound speed of non-ideal gas mixture of oxygen-hydrogen as liquid rocket propellants 査読有り国際誌

Takahashi R., Tsuboi N., Tokumasu T., Tsuda S.I.

Journal of Thermal Science and Technology ( 一般社団法人日本機械学会・社団法人日本伝熱学会 ) 18 ( 1 ) 22-00365 - 22-00365 2023年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Numerical simulations of inlet jets flow of propellants in the main combustion chamber equipped in a liquid rocket engine have been conducted by compressible CFD technics employing a van der Waals-type equation of state (EOS) and chemical reaction models. Various simulations have been already conducted both for combustion and non-combustion state in the chamber; however, the accuracy of EOS for the mixture of propellant employing a classical mixing rule (CMR), particularly for the sound speed, has not been understood well. Therefore, we have validated the applicability of Soave–Redlich–Kwong (SRK) EOS as one of the van der Waals-type EOSs coupled with the CMR for the sound speed using molecular dynamics (MD) simulations against an imaginary model of oxygen-hydrogen mixture system. We found that SRK EOS coupled with a well-employed CMR can reproduce the sound speed in the MD simulations within a relative error of several percent and that the CMR hardly increases the deviation of the SRK EOS in the single component. The present results suggest that the SRK EOS with the CMR cannot be the main factor to cause critical errors in the CFD based on RANS, which will give reliability to current CFD simulations for internal flows in a combustion chamber of a liquid rocket engine.

DOI： 10.1299/jtst.22-00365

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3D Evaluation of Premixed Gas Injection Ports Number on Flow Field in Disk RDE 査読有り国際誌

Ito T., Tsuboi N., Ozawa K., Hayashi A.K.

AIAA SciTech Forum and Exposition, 2023 2023年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Three-dimensional viscous simulations on the DRDE (disk-type rotating detonation engine) are presented using the Navier-Stokes equations with the H2-air UT-JAXA reaction mechanism. The purposes of this study are to visualize the propagation pattern inside the DRDE combustor, to investigate the number of injection ports on the propagation pattern, and to evaluate their effects on the stable propagation of detonation and the performance of the DRDE. The results show that the number of injection ports affects the generation of new detonation waves; that the number of injection ports is related to the number of propagating detonation waves; that when two detonation waves are propagating, they have a characteristic form of propagation that they approach and leave each other.

DOI： 10.2514/6.2023-0577

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Numerical Study on Pressure Gain of Rotating Detonation System 査読有り国際誌

Koichi Hayashi A., Ito T., Tsuboi N., Ozawa K., Ishii K., Dzieminska E., Obara T., Maeda S., Mizukaki T.

AIAA SciTech Forum and Exposition, 2023 2023年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The study of pressure gain (PG) for disc type - rotating detonation engine (D-RDE) is performed numerically to figure out how their PG can be increased. The mixture system of H2/O2 is applied to see a difference in PG between two different dimension calculation. The numerical system is performed using the 2D- and 3D- compressible Navier-Stokes equations with the UT-JAXA hydrogen combustion mechanism. The experimental data from H2/air mixture for PG are also obtained to compare with the previously obtained numerical data. The present numerical results show that the PG of D-RDE is almost no difference or a bit smaller than that of regular RDE. To get an increase of PG, the relation between injection pressure and exit pressure of chamber, P8/P3,1, we have to check the area ratio between the fuel injection total area and the exit area, the effect of mass flow rate on PG, and the back pressure effect on PG.

DOI： 10.2514/6.2023-2565

Kyutacar

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Numerical study on unsteady characteristics of high-pressure hydrogen jet ejected from a pinhole 査読有り

Asahara M., Iwasa T., Tsuboi N., Hayashi A.K.

International Journal of Hydrogen Energy 47 ( 74 ) 31709 - 31728 2022年08月

記述言語：英語掲載種別：研究論文（学術雑誌）

The aim of this study was to delineate the unsteady fluid dynamics of the high-pressure hydrogen jet to clarify the relationship between the forced ignition position and the flame development characteristics in a high-pressure hydrogen jet leaking from a pinhole. The Navier–Stokes equation for a compressible multi-component gas was used to simulate a high-pressure (82 MPa stagnation pressure) unsteady hydrogen jet ejected into the atmosphere through a pinhole (diameter = 0.2 mm). The results indicated that the flapping jet at the base of the jet formed a cloud of highly concentrated hydrogen that flowed downstream. A correlation was observed between the spatio-temporal distribution of hydrogen concentration and velocity was observed. The unsteady high-pressure hydrogen jet obtained by simulation will be used in subsequent studies focusing on flame development under forced ignition.

DOI： 10.1016/j.ijhydene.2022.05.079

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Numerical Analysis on Ammonia / Hydrogen / Air Detonation Using Detailed Chemical Reaction Model 査読有り国際誌

G. Inoue, N. Tsuboi, K. Ozawa, A.K. Hayashi

28th International Colloquium on the Dynamics of Explosions and Reactive systems Paper 94 2022年06月

Operation Characteristics of a Disk-Type Rotating Detonation Engine 査読有り国際誌

K. Ishii, K. Ohno, H. Kawana, K. Kawasaki, A.K. Hayashi, N. Tsuboi

28th International Colloquium on the Dynamics of Explosions and Reactive systems Paper 203 2022年06月

Numerical Analysis on Pressure Gain of Rotating Detonation Engine Using H2-O2 Gases: Influence of Number of Injector 査読有り国際誌

A.K. Hayashi, K. Yoshidomi, K. Ozawa, N. Tsuboi, H. Kawashima

28th International Colloquium on the Dynamics of Explosions and Reactive systems Paper 218 2022年06月

Experimental and Numerical Study on Disc-RDE: Relation between Number of Detonation Wave and Pressure 査読有り国際誌

Koichi Hayashi A., Ohno K., Ishii K., Shimomura K., Tsuboi N., Ozawa K., Jourdaine N.H., Dzieminska E., Obara T., Maeda S., Mizukaki T.

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 2022年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Disc-RDE is studied experimentally and numerically to figure out how single-wave mode and double-wave mode appear. From the measurement, we can pick up the better condition for the better pressure gain result. The experimental results are obtained that rotating detonation waves mainly propagate near the outer circumference of the combustion chamber. A transition of the wave number from single to double is found to exist at the equivalence ratio of 0.67 to 0.84. However, the normal transition of wave number is from double to single transition at the equivalence ratio of 1.45 and higher. Numerical work starts with a single-wave system to turn to double-wave system, then single-wave system back due to the ignition, bifurcation, and so on. Depending on the condition, a single-wave becomes a double-wave, which is confirmed at both the experiment and numerical analysis. The reduction of detonation velocity is confirmed at both experiment and numerical calculation up to 7 % when a single detonation becomes double one.

DOI： 10.2514/6.2022-0837

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Numerical Simulation on Rotating Detonation Engine: Effect of Number of Injection Ports in Non-Premixed H2-O2 Gases 査読有り国際誌

Yoshidomi K., Kurita N., Ozawa K., Tsuboi N., Hayashi A.K., Kawashima H.

AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 2022年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The effect of the number of injection ports in H2-O2 non-premixed gases on the performance of rotating detonation engine is estimated using two-dimensional numerical simulation with a detailed H2-O2 chemical reaction model. The differences in the instantaneous flow field, specific impulse, detonation velocity, and pressure gain are discussed among three configurations with the different numbers of injection ports. The detonation disappears for the 40-port configuration, while it continues to propagate stably for 60-and 80-port configurations. During the detonation propagation, the specific impulse has small, but significant difference depending on the number of injection ports. Detonation velocity is lower than the CJ velocity and its difference increases as the number of injection ports decreases. Pressure gain using oxygen has a maximum value of-0.084 at the 60-port configuration.

DOI： 10.2514/6.2022-1112

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Numerical Simulation of Jet Mixing in Supersonic Crossflow: Effect of Jet Exit Geometry 査読有り国際誌

IWASA Toshihiro, TSUBOI Nobuyuki

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES ( 一般社団法人日本航空宇宙学会 ) 65 ( 4 ) 172 - 184 2022年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Implicit large-eddy simulation/Reynolds-averaged Navier-Stokes hybrid simulation of sheet-like hydrogen jets in a supersonic crossflow are performed to investigate jet mixing, focusing on the difference in flow structures between sheet-like jets and round jets. The simulation is validated with a helium jet experiment in terms of the mean concentration. The numerical results showed good agreement with the experimental results. A characteristic of injection from the sheet-like jet exit is the spread of the windward jet toward the spanwise direction owing to the strong interaction with the freestream, while the leeward jet highly penetrated the freestream. In the investigation on jet mixing using different jet exit geometries, it was found that the sheet-like jet has a lower mixing efficiency compared with the round jet. The two mixing characteristics of the sheet-like jet are (i) a large jet cross-sectional area, and (ii) a weak turbulent mixing in the windward shear layer. As the effect of the momentum flux ratio on the jet mixing with sheet-like jet port, the mixing is enhanced with increasing the momentum flux ratio.

DOI： 10.2322/tjsass.65.172

Attempts of Time-Resolved Fuel Regression Measurements of an Altering-Swirling-Oxidizer-Flow-Type Hybrid Rocket Motor 査読有り国際誌

Ozawa K., Omiya K., Tsuboi N., Ishii K.

AIAA AVIATION 2022 Forum 2022年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

This paper presents efforts to acquire the time-resolved fuel regression data of an Altering-Swirling-Oxidizer-Flow-Type (A-SOFT) hybrid rocket motor using polylactic acid (PLA)-based segmented solid fuels as well as the steady-state fuel regression behavior of the A-SOFT with PLA-based solid fuel. The sensing segments are manufactured by the multi-material Fused Filament Fabrication. They have a ladder-shaped resistor structure to detect the fuel regression in the form of rapid voltage changes caused by its rung destruction. Despite the successful firings of the motor, the verification of the temporally resolved fuel regression was imperfect. The destructions of the first and final rungs provided rapid voltage change, but the other rungs did not provide a rapid voltage change when they were expected to be broken according to the time-averaged regression rate of the segment. The major factors causing the unexpected sensor voltages can include chamber pressure and thermal environments in the motor because the sensor structure had not been tested under these conditions. The spatiotemporal-averaged fuel regression behavior was approximated by a fuel-mass-flux-based linear regression, reflecting the variety of filling rates in additive-manufactured solid fuels. The approximation agreed with the resultant fuel regression behavior, with the residual standard deviation of 2.97×10-2 mm/s. The segmentation of the solid fuels provided the ease of post-experimental measurements of axial distribution of regression rates.

DOI： 10.2514/6.2022-3565

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85135041692&origin=inward

Numerical Simulation of the Deflagration to Detonation Transition in a Tube with Repeated Obstacles: Experimental Scale Simulation Using the Artificial Thickened Flame Method 査読有り国際誌

N. Tsuboi, A.K. Hayashi, Y. Tamauchi, T. Kodama

Transactions on Aerospace Research 4 ( 265 ) 41 - 53 2021年12月

Numerical investigation of three deflagration-to-detonation transition conditions related to the velocity of the spontaneous reaction wave 査読有り

Tang X., Dziemińska E., Hayashi A.K., Tsuboi N.

International Journal of Hydrogen Energy 46 ( 75 ) 37487 - 37501 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this work, the deflagration-to-detonation transition (DDT) process in a tube filled with quiescent and stoichiometric hydrogen/oxygen mixture is numerically simulated by a detailed chemical reaction model together with a high-resolution adaptive mesh refinement (AMR) mesh system. Then the flow field is analyzed in detail. It is found that for the onset of detonation in a DDT process there are three essential conditions related to the velocity of the spontaneous reaction wave DSpRW. The first condition is that on a hot spot the DSpRW should be slower than the speed of the Chapman–Jouguet (CJ) detonation wave DCJ to make sure that a spontaneous shock wave could arise originating from the spontaneous reaction wave. The spontaneous shock wave and the spontaneous reaction wave have conspicuous positive correlation to accelerate the spontaneous reaction wave to be faster than the local sound speed, which is the second DDT condition. With this condition the spontaneous reaction wave could catch up with its associated spontaneous shock wave and implement a coupling of the gasdynamics and the chemical energy release. This process is in line with Lee's SWACER idea, while throughout the process the spontaneous reaction wave propagates mainly through the Zel'dovich's reactivity gradients mechanism. Meanwhile, the gas velocity Vg is also essential to maintain the above two conditions and the resultant velocity meets the relation ∥DSpRW+Vg∥≥DCJ, which is the third condition. Distinctly this settles the wave speed gap between deflagration and detonation. More importantly, gas velocity plays an important role especially for the pressure build-up. The most important expressive differences between CJ deflagration and CJ detonation are the gas velocities of both the reactants and products as well as the pressure build-up. When these three relations successfully trigger a DDT and get a detonation wave, they still hold in the resulting detonation wave. They are delicately inherited as the inherent characters of the (detonation) wave. Formerly they are preconditioning-sustaining in the DDT process, and now they become self-sustaining in the detonation wave. Besides, the important role of the progress ratio of the induction period ε is emphasized for a spontaneous propagation.

DOI： 10.1016/j.ijhydene.2021.09.055

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85116006904&origin=inward

Time-resolved fuel regression measurement function of a hybrid rocket solid fuel integrated by multi-material additive manufacturing 査読有り

Ozawa K., Wang H.w., Yoshino T., Tsuboi N.

Acta Astronautica 187 89 - 100 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

The function of time-resolved fuel regression measurement is integrated into additively manufactured hybrid rocket fuels and conceptually demonstrated through the comparison with time-resolved optical fuel regression measurements during burns. This function is enabled by multi-material additive manufacturing of mainly thermoplastic solid fuels with a ladder-shaped resistor made of a conductive thermoplastic. This functionalization has many advantages, as indicated by its wide range of applicability, including solid fuel grains with emerging complex geometries, cost-effectiveness, ease of implementation, and minimal influence on the original propulsive performance and fuel regression behavior. Fuel regression is detected by a step change in the voltage applied to the ladder-shaped resistor, indicating the breakage of its top fuel surface rung during a burn. For ignited cases, all the rung breaks were detected, while the fuel regression was also optically measured using high-speed video. Errors were observed between the fuel regression time-histories measured using the two methods; however, most of these errors could be explained by the distribution of the fuel regression in the camera direction and the camera resolution and the melted fuel layer thickness. Considering these uncertainties, the remaining errors that could not be explained by these factors were less than ±0.15 mm, corresponding to ±1 layer of additive manufacturing applied to the prototyping of the solid fuels.

DOI： 10.1016/j.actaastro.2021.06.031

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85108881693&origin=inward

Experimental and numerical study on disc-rde: Flow structure and its performances 査読有り

Hayashi A.K., Ishii K., Watanabe T., Tsuboi N., Ozawa K., Jourdaine N.H., Dzieminska E., Tang X., Obara T., Maeda S., Mizukaki T.

AIAA Scitech 2021 Forum 1 PartF 1 - 12 2021年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The present study discusses disc-type rotating detonation engine (DRDE) experimentally and numerically. The experimental work shows that the detonation propagates in three different modes; single, dual, and hybrid. The operating frequency of dual-wave mode is 1.8-2.1 times faster than that of single wave mode. The number of detonation wave can be predicted based on the pressure history and the operating frequency signal. The numerical work shows the performance of 3D numerical analysis of DRDE with uniform injection case and multiport injection case. By increasing the wave number from one to two, the detonation propagation velocity decreases by 18.7 %. The one-detonation head case gives some better performance to the flow than the two-detonation head case. The inlet flow angle to the radial turbine becomes about 50 degrees to the radial direction no matter how large the plenum chamber is.

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ワックス燃料後退速度の加速度環境下における可視化システム研究開発

長坂春花, 小澤晃平, 坪井伸幸, 中田大将

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2021 ( 0 ) 2021年01月

Regression behavior of polylactic acid manufactured by fused filament fabrication for hybrid rocket propulsion 査読有り国際誌

Ozawa Kohei, Wang Han-wei, Inenaga Takefumi, Tsuboi Nobuyuki

Science and Technology of Energetic Materials ( 一般社団法人火薬学会 ) 82 ( 6 ) 170 - 177 2021年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Advanced closed-loop control of thrust and mixture ratio of hybrid rockets is planned by combing a fuel mass flow rate control technique with a real-time fuel regression measurement. The latter technique is enabled by a multi-materialadditive-manufactured solid fuel with an integrated sensor probe structure. This work investigated the fuel regression behavior of polylactic acid (PLA) fuel used for the main material of this type of solid fuels. Rectangular slab fuels and cylindrical fuel grains were manufactured by Fused Filament Fabrication (FFF) and fired in an optically accessible slab burner and a lab-scale motor, respectively. The cylindrical fuel grains had more than 2 times larger regression rates than rectangular slab fuels even with the same PLA filament. One of the main factors causing this large difference can be an anisotropy in the fuel regression rate behavior of the solid fuels manufactured by FFF.

DOI： 10.34571/stem.82.6_170

その他リンク： http://hdl.handle.net/10228/00008705

3D numerical study on flow field in disc-RDE 査読有り国際誌

Hayashi A.K., Shimomura K., Tsuboi N., Ozawa K., Jourdaine N.H., Ishii K., Dzieminska E., Obara T., Maeda S., Mizukaki T.

AIAA Propulsion and Energy Forum, 2021 2021年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Disc-type rotating detonation engine is studied numerically using the threedimensional compressible Navier-Stokes equations with 9 species and 21 reactions and with an multi-port injection system. Especially the grid resolution using two-detonation case and the process of stabilization for one and two-detonation cases are studied. As the results of grid resolution, the case of larger grid number provides higher pressure due to capturing the pressure oscilation better and that their rotating speed becomes faster. And the detonation velocity becomes faster when the number of grid becomes larger. As the results of the process of stabilization for one and two-detonation cases, two detonation wave propagate by changing back and forth their distance and no matter what the number of detonation wave is given, one or two, the final detonation wave number becomes two.

DOI： 10.2514/6.2021-3665

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85123365877&origin=inward

Numerical simulations on propane/oxygen detonation in a narrow channel using a detailed chemical mechanism: formation and detailed structure of irregular cells 査読有り国際誌

Takeshima N., Ozawa K., Tsuboi N., Hayashi A.K., Morii Y.

Shock Waves 30 ( 7-8 ) 809 - 824 2020年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Numerical simulations of two-dimensional inviscid detonations for a stoichiometric propane/oxygen gas mixture are performed using a detailed chemical reaction model. The UC San Diego model which includes 57 chemical species and 268 elementary reactions is mainly used in the present study. It is shown that a grid size of 3 µm can capture important features such as the unburned gas pocket behind the detonation when compared to larger grid sizes. The effects of channel width show that the detonation propagates with the CJ (Chapman–Jouguet) velocity for all cases and for more than 100 times the channel width of 4.5 mm. Increasing the channel width results in an irregular detonation cell structure. A transverse detonation forms with cross-hatching marks on the maximum pressure history. The irregular detonation cell structure forms because both the reduced activation energy and the stability parameter have a value of approximately 10; however, the maximum thermicity in the detonation is one. The free radicals C3H7 and H2O2 play an important role in the propane oxidation under the high temperature in the detonation. The maximum concentration exists at a temperature of 2000–3000 K. The fifth-order WCNS (weighted compact nonlinear scheme) scheme can resolve the contact surface and complicated flow structure behind the detonation front compared to the second-order MUSCL (Monotonic Upstream-centered Scheme for Conservation Laws).

DOI： 10.1007/s00193-020-00978-5

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85097766750&origin=inward

Recent Experimental and Numerical Study on Disc-Type RDEs 査読有り国際誌

A. K. Hayashi, N. Tsuboi, K. Ozawa, T. Watanabe, N.H. Jordaine, K. Ishii, H. Kawana, W. Kuwata, K. Ohno, T. Obara, S. Maeda, E. Dzieminska, X. Tang, T. Mizukaki

2020 AIAA SciTech AIAA-2020-1169 2020年01月

Numerical Simulation on Disk Rotating Detonation Engine: Influence of Internal Flow Field Structure on Performance 査読有り国際誌

Tomohiro Watanabe, Kodai Shimomura, Nicolas H. Jourdaine, Kohei Ozawa, Nobuyuki Tsuboi, Takayuki Kojima, Kazuhiro Ishii, A. Koichi Hayashi

AIAA Scitech 2020 Forum AIAA-2020-2160 2020年01月

Three-Dimensional Numerical Simulation on Hydrogen/Air Rotating Detonation Engine with Aerospike Nozzle: Effects of Nozzle Geometries 査読有り国際誌

Nobuhiro Kurita, Nicolas Jourdaine, Nobuyuki Tsuboi, Kohei Ozawa, A. Koichi Hayashi

2020 AIAA SciTech AIAA-2020-0688 2020年01月

多素材3Dプリンタ製燃料後退計測機能付き固体燃料の研究

小澤晃平, 王瀚緯, 坪井伸幸

スペース・エンジニアリング・コンファレンス講演論文集 ( 一般社団法人日本機械学会 ) 2020 ( 0 ) 2020年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

Prototype solid fuels for a hybrid rocket were fabricated by using a multi-material 3D printer and conductive thermoplastic composite to construct a ladder-shaped resistance inside the electrically-insulated thermoplastic solid fuel and to measure the time-resolved fuel regression. In this type of fuels, the remaining fuel thickness is monitored by the voltage applied to the resistance that changes according to the number of rungs of the ladder-shaped resistor. For comparison with the proposed measurement, the time-resolved fuel regression was optically measured by using a high-speed video visualization. The solid fuel regression history with the proposed technique agreed well with that with the optical measurement considering the uncertainties in the measurement methods. Errors that cannot be explained by these uncertainties were found to be ±0.15 [mm], corresponding to ±1 layer of the stacking pitch of the 3D printer applied in this study. This paper also shows a preliminary firing test result using a post-processed 3D-printed cylindrical solid fuel grain as a preparation for the application of the proposed technique to the cylindrical solid fuel.

DOI： 10.1299/jsmesec.2020.29.C1

その他リンク： https://ci.nii.ac.jp/naid/130008064623

Three-dimensional numerical simulation on hydrogen/air rotating detonation engine with aerospike nozzle: Effects of nozzle geometries 査読有り

Kurita N., Jourdaine N., Tsuboi N., Ozawa K., Hayashi A.K., Kojima T.

AIAA Scitech 2020 Forum 1 PartF 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Three-dimensional simulations with a detailed chemical reaction model were performed to evaluate the propulsive performance of rotating detonation engines (RDEs) for H2/Air with conic aerospike nozzles. The simulations aimed to clarify the propulsive performance for various configurations of aerospike nozzle: open/choked or complete/truncated configurations. The governing equations were the Euler equations, and the chemical model was for 9 species and 21 element chemical reactions. Various equivalent ratios from 0.9 to 1.4 were simulated. The results show that the specific impulse (Isp) and the efficiency of the choked nozzle were 4-6% higher than those for the open nozzle. The higher pressure in the chamber due to the decreasing in the throat area resulted in a gain of pressure thrust by the nozzle and consequently, an addition in Isp and the efficiency. The difference in thrust performance between the complete and the truncated nozzle was smaller than 2% because the pressure component on the base surface compensated for the thrust drop.

DOI： 10.2514/6.2020-0688

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091953963&origin=inward

Recent experimental and numerical study on disc-type rdes 査読有り

Hayashi K., Tsuboi N., Ozawa K., Watanabe T., Jourdaine N.H., Ishii K., Kawana H., Kuwata W., Ohno K., Obara T., Maeda S., Dzieminska E., Tang X., Mizukaki T.

AIAA Scitech 2020 Forum 1 PartF 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The present study discusses disc-type rotating detonation engine (DTRDE) experimental ly and numerically. The experimental work is performed using hydrogen and air and measuring pressure records together with taking a high speed movie to see a direction of rotating detonation. Especially the relation between mass flow rate and operation frequency and that between equivalence ratio and operation frequency. The number of detonation head is figured out from the maximum operation frequency. Then the 3D numerical analysis of DTRDE will provide the flow structure in the DTRDE combustion chamber, high pressure profile, and low mach number profiles.

DOI： 10.2514/6.2020-1169

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091925389&origin=inward

Numerical study on JP-10/air detonation and rotating detonation engine 査読有り国際誌

Hayashi A.K., Tsuboi N., Dzieminska E.

AIAA Journal 58 ( 12 ) 5078 - 5094 2020年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

JP-10/air two-phase detonation and rotating detonation engine (RDE) are numerically studied to find out their limits of physical values as a function of equivalence ratio, prevaporization, fuel concentration, droplet diameter, and initial pressure and temperature. To find such limits, the JP-10/air two-step chemical reaction mechanism is used and the Eulerian–Eulerian two-phase governing system is developed to simulate those limits. Especially the JP-10/air two-phase detonation velocity and cell size are investigated in detail and the generation of nonreacted region and quenching mechanism of JP-10/air two-phase RDE are simulated. The findings from those studies are that 1) the JP-10/air two-phase detonation and RDE codes are developed and validated to calculate detonation and RDE; 2) the JP-10/air detonation cell size is calculated by the developed code to show a good agreement with the experimental data; and 3) the JP-10/air RDE simulation shows a detonation quenching at the condition when the droplet diameter is larger than 4 μm and the prevaporization factor is smaller than 20%.

DOI： 10.2514/1.J058167

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Accuracy of real-time fuel regression measurement function of a 3d printed solid fuel 査読有り

Ozawa K., Wang H.W., Inenaga T., Tsuboi N.

AIAA Propulsion and Energy 2020 Forum 1 - 15 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

The accuracy of a real-time fuel regression measurement by an additive manufactured solid fuel was discussed by comparing with optically measured regression acquired in firing experiments for the conceptual demonstration. The solid fuels that succeeded in fuel regression measurement were manufactured by a multi-material 3D printer and had the ladder-shaped resistor structure with the 0.15 mm thickness rungs. The fuel regression is detected by the voltage change in the reference resistor due to the break of rungs. For all experiments, the initial resistance of the ladder-shaped resistor structure was estimated to be as expected, and all rung break was successfully detected by the steep voltage change. The acquired measurement values by the two methods had errors like an offset for all runs. The major factors of these errors were the distribution of the fuel regression in the fuel width direction and the resolution of the high-speed video camera. As a result, it was found that the time histories of the values optically measured for comparison had relatively large uncertainties. The remaining errors that cannot be explained by these major error factors were estimated to be less than ±0.15 mm, which corresponds to two layers of the solid fuels manufactured in this study.

DOI： 10.2514/6.2020-3741

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85091296741&origin=inward

Real-time regression rate measurement of an additive-manufactured functional hybrid rocket fuel 査読有り国際誌

Ozawa, K, Wang, H.-W., Yoshino, T., Tsuboi, N.

70th International Astronautical Congress, IAC 2019 2019年10月

Boundary-layer combustion of wax-based fuels at various chamber pressures under two static acceleration environments 査読有り国際誌

Ozawa, K., Yoshino, T., Wang, H.-W., Tsuboi, N.

AIAA Propulsion and Energy Forum and Exposition 2019 AIAA-2019-4100 2019年08月

A Study on Operating Conditions of Disk-Type Rotating Detonation Engine 査読有り国際誌

H. Kawana, W. Kurata, K. Ohno, K. Ishii, A. K. Hayashi, N. Tsuboi, K. Ozawa, T. Obara, S. Maeda, E. Dzieminska, T. Mizukaki

27th International Colloquium on the Dynamics of Explosions and Reactive System 415 2019年08月

Gradient Mechanism on the Onset of Detonation in the Deflagration to Detonation Transition 査読有り国際誌

X. M. Tang, E. Dzieminska, A.K. Hayashi, N. Tsuboi

27th International Colloquium on the Dynamics of Explosions and Reactive System 247 2019年08月

Simulation of detonation propagation in a two-phase gas/liquid cross flow injection 査読有り国際誌

Nicolas Jourdaine, Nobuyuki Tsuboi, A. Koichi Hayashi, Xinmeng Tang, Kohei Ozawa

27th International Colloquium on the Dynamics of Explosions and Reactive System 435 2019年08月

Two-dimensional Numerical Simulations on Unstable Propagation of Propane/Oxygen Detonation Using Detailed Chemical Mechanism 査読有り国際誌

Naomi Takeshima, Kohei Ozawa, Nobuyuki Tsuboi, Youhi Morii, A. Koichi Hayashi

27th International Colloquium on the Dynamics of Explosions and Reactive System 268 2019年08月

Two-dimensional Numerical Simulation of Flame Acceleration and Deflagration-to-Detonation Transition in Channels with Obstacles: Effects of Blockage Ratio and Channel Size 査読有り国際誌

Kanta Iwasaki, Ayu Ago, Nobuyuki Tsuboi, Kohei Ozawa, A. Koichi Hayashi

27th International Colloquium on the Dynamics of Explosions and Reactive System 267 2019年08月

Mixing characteristics of the slit-shaped hydrogen jet in supersonic crossflow 査読有り国際誌

Toshihiro Iwasa, Nobuyuki Tsuboi

32nd International Symposium on Shock Waves OR-21-0357 2019年07月

Feasibility Study of a Real-time Fuel Regression Rate Measurement using an Electrostatic Capacitive Probe for Hybrid Rocket Engine 査読有り

Han-Wei Wang, Kohei Ozawa, Nobuyuki Tsuboi

32nd International Symposium on Space Technology and Science 2019 a91363 2019年06月

Numerical Study on Cryogenic Jet/Crossflow Interaction Structures under a Supercritical Pressure 査読有り

Taishi Amano, Takahide Araki, Hiroshi Terashima, Daiki Muto, Kohei Ozawa, Nobuyuki Tsuboi

32nd International Symposium on Space Technology and Science (ISTS) a91387 2019年06月

Validation of classical mixing rule coupled with van der Waals type equation of state for sound speed of non-ideal gas mixture

Ryuji Takahashi, Nobuyuki Tsuboi, Takashi Tokumasu, Satoshi Watanabe and Shin-ichi Tsuda

American Physical Society March Meeting 2019 R18.00010 2019年03月

Three-dimensional numerical thrust performance analysis of hydrogen fuel mixture rotating detonation engine with aerospike nozzle 査読有り

Jourdaine N., Tsuboi N., Ozawa K., Kojima T., Koichi Hayashi A.

Proceedings of the Combustion Institute 37 ( 3 ) 3443 - 3451 2019年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

The propulsive performance for an H 2 /O 2 and H 2 /Air rotating detonation engine (RDE) with conic aerospike nozzle has been estimated using three-dimensional numerical simulation with detailed chemical reaction model. The present paper provides the evaluation of the specific impulse (I sp ), pressure gain and the thrust coefficient for different micro-nozzle stagnation pressures and for two configurations of conic aerospike nozzle, open and choked aerospike. The simulations show that regardless of the nozzle, increase the micro-nozzles stagnation pressure increases the mass flow rate, the pre-detonation gases pressure and consequently the post-detonation pressure. This gain of pressure in the combustion chamber leads to a higher pressure thrust through the nozzle, improving the I sp . It was also found that the choked nozzle increases the chamber time-averaged static pressure by 50-60% compared with the open nozzle, inducing higher performance for the same reason explained before.

DOI： 10.1016/j.proci.2018.09.024

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85054134991&origin=inward

Three-dimensional numerical simulation of disk rotating detonation engine: Unsteady flow structure 査読有り

Watanabe T., Jourdaine N., Ozawa K., Tsuboi N., Kojima T., Hayashi A.

AIAA Scitech 2019 Forum 2019年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2019 by Timothy K. Minton. Published by the American Institute of Aeronautics and Astronautics, Inc. Disk Rotating Detonation Engine (DRDE) simulation using a mixture of hydrogen and oxygen was performed by three-dimensional numerical analysis with detailed chemical reaction model. The computational grid is created based on the DRDE combustor shape designed by Huff et al. and this grid system use three regions. In zone 1 and 2, the inside of the combustor is simulated and in zone 3, the flow behind the nozzle exit is simulated. The combination of coarse and fine computational grids can calculate the propagation of rotating detonation wave inside the DRDE with small computational resources. The present results show that the detonation wave front is not normal to the outer circular wall but has approximately 60 degrees. The maximum pressure near the detonation head on the outer wall has approximately 10 MPa. The Mach number of the exhaust flow becomes approximately 2.5 in this condition.

DOI： 10.2514/6.2019-1498

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85068967701&origin=inward

Development of a high efficiency system with a rotating detonation engine for a gas turbine engine (RDE-GTE) using pressure gain combustion 査読有り

Koichi Hayashi A., Tsuboi N., Ozawa K., Ishii K., Obara T., Maeda S., Dzieminska E., Mizukaki T.

AIAA Scitech 2019 Forum 2019年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. The present study will show a new development of a gasturbine engine with rotating detonation engine. Five universities and a venture company will study characteristics of rotating detonation engines to develop a gasturbine engine with RDE system in order to improve its performance of gas turbine engine, especially its efficiency. We have three teams; the experimental team, numerical team, and gasturbine team. The experimental team will perform several categories; concentric as well as disk type RDE development and measurement of its stable conditions and controlabilities as well as its efficiency; the cooling system of RDE; injection and ignition system; and DDT performance. The numerical group will simulate above experimental categories by real size calculations with both DNS and AMR base. And a micro-gasturbine engine will be run together with RDE system in a near future. We prefer to choose a disc type RDE instead of concentric cylinder type one. Hence the midterm report like presentation will be given at the SciTech meeting, Jan 2019 and 2020.

DOI： 10.2514/6.2019-1509

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85068912203&origin=inward

Effects of a recess on supercritical co-flowing planar jets 査読有り

Muto D., Terashima H., Tsuboi N.

Transactions of the Japan Society for Aeronautical and Space Sciences 62 ( 4 ) 203 - 212 2019年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 The Japan Society for Aeronautical and Space Sciences. The effects of a recess on co-flowing planar jets under supercritical pressure are numerically studied. Two-dimensional hybrid LES/RANS simulations are performed in a wide range of recess lengths and injection momentum flux ratios, which are important design parameters for liquid rocket engine injectors. The present study showed that confinement effects of the near-injector flowfield by applying a recess, suppress outer jet spreading and thus enhances the penetration of the outer jet flow into the inner jet. The enhanced penetration of the outer jet flow results in the appearance of flapping motions in the inner jet. Low-frequency oscillations corresponding to the flapping motions clearly appear in the case of recessed injectors. Moreover, the confinement effects promote interactions between vortex structures resulting in vortex breakdown. Consequently, the inner-jet length is shortened, indicating an improvement in mixing when a recess is applied. The present results also show that the inner-jet length deceases as the recess length increases, and the effects of a recess remarkably appear at higher momentum flux ratios. This is explained by the vortices generated behind the post lip that is strengthened as the result of increased velocity ratio.

DOI： 10.2322/tjsass.62.203

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障害物を有する管内での酸水素デトネーション遷移の2次元数値解析：実験との比較

岩﨑幹太, 吾郷愛由, 坪井伸幸, 小澤晃平, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) 2019年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

Detonation is a type of premixed combustion, which propagates interacting with shock waves and combustion flames at supersonic speed. It is known in the early researches that DDT (Deflagration to Detonation Transition) in a channel is promoted by installing obstacles. This research investigates flame propagation and local explosions in channels filled with hydrogen/oxygen stoichiometric mixture and installed ten obstacles by using the two-dimensional simulation with a detailed reaction model. Furthermore, we estimate differences between the three-dimensional experiments performed in a past study and the present two-dimensional simulations. The simulations performed by changing the scale of the channel, grid width, and obstacle height. As a result, the flames did not transit to detonation under any conditions of the obstacle heights and channel sizes, unlike the experiments. Higher obstacles disturbed the flame propagation and induced the shock waves crossing the channel, which lead to the enhancement and acceleration of the combustion reaction. A small local explosion was observed near the eighth obstacle at one-tenth the size. The flame acceleration was faster in the experiment than in the numerical analysis.

DOI： 10.1299/jsmekyushu.2019.72.B14

その他リンク： https://ci.nii.ac.jp/naid/130007801915

超臨界圧下における主流と直交干渉する極低温噴流構造について：3-D LES/RANSハイブリッド解析

天野泰嗣, 荒木天秀, 寺島洋史, 武藤大貴, 坪井伸幸

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) 2019年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

The engine cycle of a Japanese next flagship liquid rocket applies an expander bleed cycle and it has a component called mixer. In the mixer, cryogenic hydrogen is vertically injected through the perforated plate into the high temperature hydrogen flow under supercritical pressures. It is important to complete mixing efficiently in the mixer because insufficient mixing may lead to non-uniform temperature distribution and thereby cause combustion instabilities in the chamber. The objective of this study is to investigate flow structures and mixing of a cryogenic jet injected into the crossflow under a supercritical pressure using a three-dimensional LES/RANS hybrid model. The results found that periodic vortex structures are formed around the jet and they have dominant role on near jet mixing processes. The shedding vortices penetrate into a region behind the jet, establishing a recirculation region. There are some differences in the jet height and the recirculation region, compared with those in a two-dimensional calculation.

DOI： 10.1299/jsmekyushu.2019.72.D12

その他リンク： https://ci.nii.ac.jp/naid/130007801950

異種分子間相互作用の影響に注目した酸水素混合系に対するcubic型状態方程式の第一原理的検証

髙橋竜二, 坪井伸幸, 徳増崇, 渡邉聡, 津田伸一

年次大会 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) 2019年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In compressible computational fluid dynamics (CFD) analyses for combustion chamber of liquid rocket engine, the combination of cubic type equation of state (EOS) and classical mixing rule (CMR) is mostly used as typical EOS for mixture system. However, validation of the EOS for the mixture of liquid rocket propellant has hardly been validated due to lack of experimental data. Previously, validation of cubic type EOS with CMR was conducted by molecular simulation applying an ab-initio intermolecular potential as a quantum chemical approach. However, the accuracy of the H2-O2 potential is questionable because it was constructed on the basis of molecular orbital (MO) calculation for some limited molecular orientations. Therefore, in this study, we performed MO calculations for more molecular orientations between H2-O2 and reconstructed the intermolecular potential on the basis of the results of MO calculations with CCSD(T)/augcc-PVQZ level of theory. Next, we revalidated cubic type EOS coupled with CMR by evaluating the thermophysical properties of supercritical oxygen-hydrogen mixture system using Monte Carlo (MC) simulations applying the improved H2-O2 potential. As a result, we confirmed that cubic type EOS coupled with CMR can roughly reproduce the thermophysical properties obtained from MC simulation. Therefore, it was suggested that cubic type EOS with CMR can be applied to CFD analyses for combustion chamber of liquid rocket engine.

DOI： 10.1299/jsmemecj.2019.J05412

その他リンク： https://ci.nii.ac.jp/naid/130007816327

メタン/酸素予混合気におけるデトネーションセル構造の新たな可視化方法とギャッロッピングデトネーションの速度振動の詳細計測に関する研究

久門昂平, 小澤晃平, 坪井伸幸, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) 2019年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In order to understand the detailed mechanism of galloping detonation of methane and oxygen, efforts were made to improve the cellular structure and propagation velocity of unsteady detonation. Firstly, as an alternative to smoked foil method, a new visualization of cell structure was attempted using CB film, mylar film covered by carbon black with spray-type adhesive. CB film succeeded in recording cell structure, and this result suggests a potential to apply for image recognition of the cell structure using strong backlight at scanning CB film. Secondly, the correlation between the cell structure and the propagation velocity in a galloping detonation was investigated by combining the detonation velocity measurement and smoked foil method. The propagation velocity distribution was measured using twice the sampling points in the same detonation tube length as in our previous research. This experiment revealed that, after the over-driven detonation started to decelerate, small non-uniform cell structure was formed and transited to spinning mode during the deceleration. Consequently, in galloping detonation, a strong correlation was found between wave-front acceleration and cell structure.

DOI： 10.1299/jsmekyushu.2019.72.D13

その他リンク： https://ci.nii.ac.jp/naid/130007801952

Real-time regression rate measurement of an additive-manufactured functional hybrid rocket fuel 査読有り

Ozawa K., Wang H.W., Yoshino T., Tsuboi N.

Proceedings of the International Astronautical Congress, IAC 2019-October 2019年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. The function of real-time fuel regression integrated into an additively-manufactured hybrid rocket fuel was conceptually demonstrated by firing experiments. This fuel has a complex ladder resistor structure made of a plastic filament including conductive additives in an electrically insulated main plastic fuel. The real-time regression rate measurement is enabled by the change of the voltage applied to the ladder resistor structure when the top rung is broken by the fuel regression. This type of fuel has advantages in the easy acquisition of the distribution of the local regression rates with a greatly small pitch, minimizing the influences on the structural mass, propulsive performance, and fuel regression behavior especially when loading such a measurement system on space vehicles. Prototype slab fuels outputted steep changes in the voltage indicating the break of the rungs when using rungs with the thickness of 0.15 mm in firing experiments. The acquired breaking signals with the positions of the rungs were compared with the results of the fuel surface detection in the high-speed videos. In 3 of 4 successful experiments, the sensing system of the proposing measurement method followed the fuel regression detected by the high-speed videos within 0.5 mm errors, which are in the same range as the roughness of the solid fuels after the burns. The time history of the breaking signals showed a fuel regression at an almost constant rate. The difference of the steady-state regression rates was less than 0.06 mm/s between these two methods, except for run #4, 0.094 mm/s. It was also confirmed that the ladder resistor structures can be a heater to warm the main solid fuel when applying a voltage larger than 5 V to the resistor structure. This function is also useful for the thermal management of solid fuels in space.

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Boundary-layer combustion of wax-based fuels at various chamber pressures under two static acceleration environments 査読有り

Ozawa K., Yoshino T., Wang H.W., Tsuboi N.

AIAA Propulsion and Energy Forum and Exposition, 2019 2019年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2019 by American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Boundary layer combustion of wax-based fuels was visualized under atmospheric and supercritical chamber pressures under vertical and horizontal setups. The final goal of this research is to clarify the effects of acceleration environments on the performance of wax-based fuels. At the atmospheric pressure, the roll waves of the melted fuel excited propagated over the fuel top surface, and fuel droplets were entrained by the main gaseous flow for the horizontal setup. However the propagation of the roll waves covered at most 55% of the fuel to surface, and the entrained fuel droplets were hardly observed for the vertical setup. Above the critical pressure, the instabilities of the melted fuel were observed for both setups, but it was difficult to find any differences in the behaviors of the melted fuel due to the strong radiation of the fuel-rich flame on the melted fuels even after the various improvements of the optical system and the solid fuel. At supercritical pressures, the diffusion flames and the melted fuels oscillated at the frequency of approximately 600 Hz by sight, which is approximately the same with the natural frequency of the TCG coupling mode. The fast Fourier transformation up to 500 Hz output an intense peak of approximately 311 Hz for all runs with the horizontal setup and the sonic nozzle. A slight difference in the fuel regression behavior was found between the two burner setups. The vertically set burner showed the larger regression rates at supercritical conditions whereas the regression exponent for the horizontal setup agreed with that of existing data with a horizontally set motor. This result suggests body force increases the mass flow rate of the melted fuel film, which was not considered as a fuel mass transfer in the current liquefying hybrid theory.

DOI： 10.2514/6.2019-4100

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Numerical Study on Aerodynamic Characteristics of Reusable Vehicle-eXperiment Rocket with Body-flap during Gliding

Yoshiki Nishikawa, Nobuyuki Tsuboi, Takashi Ito, Satoshi Nonaka

15th International Conference on Flow Dynamics GS1-30 2018年11月

Statistical mechanical evaluation of thermophysical properties of oxygen-hydrogen mixture system based on the differential hierarchy of a complete thermodynamic function

Ryuji Takahashi, Nobuyuki Tsuboi, Takashi Tokumasu and Shin-ichi Tsuda

Fifteenth International Conference on Flow Dynamics CRF-58 2018年11月

Numerical Simulations of Hydrogen Jet Mixing in Supersonic Crossflow for Liquid Rocket Commanded Destruction

Toshihiro Iwasa, Keiichiro Fujimoto, Daiki Muto, Nobuyuki Tsuboi

12th Asian Computational Fluid Dynamics Conference 0104 2018年10月

Two-Dimensional Numerical Simulation of Detonation Transition with Multi-Step Reaction Model: Effects of Obstacle Height 査読有り

A. Ago, N. Tsuboi, E. Dzieminska, A. K. Hayashi

Combustion Science and Technology 191 659 - 675 2018年08月

Numerical investigation of a high pressure hydrogen jet of 82 MPa with adaptive mesh refinement: Concentration and velocity distributions 査読有り

Tang X., Dzieminska E., Asahara M., Hayashi A., Tsuboi N.

International Journal of Hydrogen Energy 43 ( 18 ) 9094 - 9109 2018年05月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 Hydrogen Energy Publications LLC To investigate the safety properties of high-pressure hydrogen discharge or leakage, an under-expanded hydrogen jet flow with a storage pressure of 82 MPa from a small jet orifice with a diameter of 0.2 mm is studied by three-dimensional (3D) numerical calculations. The full 3D compressible Navier-Stokes equations are utilized in a domain with a size of about 3 × 3 × 6 m which is discretized by employing an adaptive mesh refinement (AMR) technology to reduce the number of grid cells. By AMR, the local mesh resolutions can narrowly cover the Taylor microscale lTand direct numerical simulations (DNS) are performed. Both the instantaneous and mean hydrogen concentration distributions in the present jet are discussed. The instantaneous concentrations of hydrogen CH2on the axis presents significant turbulent pulsating oscillations. The centerline value of the intensity of concentration fluctuation σˆH2asymptotically comes to 0.23, which is in a good agreement with the existing experimental results. It substantiates the conclusion that the asymptotic centerline value of σˆH2is independent of jet density ratio. The probability distributions function (PDF) of instantaneous axial CH2agree approximately with the Gaussian distribution while skewing a little to the higher range. The time averaged hydrogen concentration C¯H2along the radial directions can also be described as a Gaussian distribution. The axial C¯H2of 82 MPa hydrogen jet tends to obey the distribution discipline approximated with C¯H2=4200/(z/θ) where z is the axial distance from the nozzle and θ is the effective ejection diameter, which is consistent with the experimental results. In addition, the hydrogen tip penetration Ztipis found to be in a linear relationship with the square root of jet flow time t. Meanwhile, the jet's velocity half-width LVhapproximately gains an linear relation with z which can be expressed as LVh=0.09z.

DOI： 10.1016/j.ijhydene.2018.03.089

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Three-dimensional numerical simulation on hydrogen-oxygen rotating detonation engine with unchoked aerospike nozzle 査読有り

Tsuboi N., Jourdaine N., Watanabe T., Koichi Hayashi A., Kojima T.

AIAA Aerospace Sciences Meeting, 2018 ( 210059 ) 2018年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. The present study simulates three-dimensional rotating detonation engine with an unchoked aerospike nozzle geometry for hydrogen/oxygen gas mixture to understand the advantages to use the aerospike nozzle on the thrust performance. The gonverning equations uses the unsteady three-dimensional compressible Euler equations with the detailed chemistry model. The oblique shock wave propagates along the coaxial combustion chamber and outside of the nozzle exit. The exhaust jet under atmospheric condition is slightly underexpanded and some complicated and unsteady shock waves are formed in the plume. The degree of the expansion in the exaust flow increases as the stagnation pressure increases. The effects of the stagnation pressure on the thrust performance indicate that Isp increases 270s for p0= 4 MPa although Isp for p0= 1.5 MPa is 220s. The time-averaged thrust is proportional to the injected mass flow and this feature is different from those without the external regions.

DOI： 10.2514/6.2018-1885

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Visualization of boundary layer combustion of wax-based fuels in vertical and horizontal configurations 査読有り

Ozawa K., Yoshino T., Tsuboi N.

2018 Joint Propulsion Conference 2018年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Efforts have been carried out from both the theoretical and experimental approaches to reveal the effects of body force parallel to the main flow on the diffusion flame in hybrid rocket propulsion with entrainment of liquid fuel droplets. A theoretical study on liquefying fuels such as wax fuels were partially extended for static acceleration environments and acquired interesting results that the static body force scarcely affects the internal ballistics of the entrained fuel droplets but it can affect the thickness of the liquid fuel layer and the fuel regression rate of the entrained droplets. Diffusion flame of two wax fuels at the atmospheric pressure has been visualized with a slab burner and a high-speed camera in the horizontally and vertical configurations to change the body force loaded to the fluid in the slab burner. The instability of the diffusion flames looked similar to each other over all the experiments, and the high-speed video has observed a few burning droplets entrained from the liquid fuel layer in each of the experiments. The monitoring camera observed a lot of unburned fuel droplets from the slab burner vertically installed.

DOI： 10.2514/6.2018-4928

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Validation of classical mixing rule coupled with a van der Waals-type equation of state for supercritical mixture system of oxygen and hydrogen using molecular simulation 査読有り

TAKAHASHI Ryuji, TSUBOI Nobuyuki, TOKUMASU Takashi, TSUDA Shin-ichi

Mechanical Engineering Letters 2018年01月

Numerical prediction of forced-ignition limit in high-pressurized hydrogen jet flow through a pinhole 査読有り

Makoto Asahara, Nobuyuki Tsuboi, N., Fujimoto, K., Muto, D., Hayashi, A.K.

Intermational Conference on Hydrogen Safety ID193 2017年09月

A molecular dynamics study of nuclear quantum effect on diffusivity of hydrogen molecule 査読有り

Nagashima H., Tsuda S., Tsuboi N., Hayashi A., Tokumasu T.

Journal of Chemical Physics 147 ( 2 ) 2017年07月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 Author(s). In this paper, the nuclear quantum effect of the hydrogen molecule on its diffusivity was analyzed using the molecular dynamics (MD) method. The centroid MD (CMD) method was applied to reproduce the time evolution of the molecules. The diffusion coefficient of hydrogen was calculated using the Green-Kubo method over a wide temperature region, and the temperature dependence of the quantum effect of the hydrogen molecule on its diffusivity was addressed. The calculated results were compared with classical MD results based on the principle of corresponding state (PCS). It was confirmed that the difference in the diffusion coefficient calculated in the CMD and classical MD methods was small, and the PCS appears to be satisfied on the temperature dependence of the diffusion coefficient, even though the quantum effect of the hydrogen molecules was taken into account. It was clarified that this result did not suggest that the quantum effect on the diffusivity of the hydrogen molecule was small but that the two changes in the intermolecular interaction of hydrogen due to the quantum effect offset each other. Moreover, it was found that this tendency was related to the temperature dependence of the ratio of the kinetic energy of the quantum fluctuational motion to the classical kinetic energy.

DOI： 10.1063/1.4991732

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Numerical Study on Effects of Obstacle Shape on Detonation Transition Mechanism 査読有り

A. Ago, T. Niibo, N. Tsuboi, A.K. Hayashi

26th International Colloquium on the Dynamics of Explosions and Reactive systems 1027 2017年07月

Numerical Analysis on Liquid JP10 Rotating Detonation Engine 査読有り

A.K. Hayashi, W. Yoshida, M. Asahara, N. Tsuboi

26th International Colloquium on the Dynamics of Explosions and Reactive systems 2017年07月

Two-Dimensional Numerical Analysis on Shock Flame Interaction in Premixed Gas of Hydrocarbon/Oxygen with Multi-Step Reaction Model 査読有り

M. Iwai, K. Yoshida, Y. Morii, N. Tsuboi, A.K. Hayashi

26th International Colloquium on the Dynamics of Explosions and Reactive systems 1050 2017年07月

Experimental Study on Behavior of Methane/Oxygen Gas Detonation Near Propagation Limit in Small Diameter Tube: Effects of Equivalent Ratio 査読有り

K. Yoshida, T. Inoue, Y. Morii, K. Murakami, N. Tsuboi, A.K. Hayashi,

26th International Colloquium on the Dynamics of Explosions and Reactive systems 822 2017年07月

Numerical Simulations of Transverse Jet in Supersonic Crossflow toward an Understanding of Interaction Mechanism 査読有り

Toshihiro Iwasa, Keiichiro Fujimoto, Daiki Muto, Nobuyuki Tsuboi

31st International Symposium Shock Waves 2017年07月

Numerical investigation of a high pressure hydrogen jet of 82 MPa with adaptive mesh refinement: The starting transient evolution and Mach disk stabilization 査読有り

Tang X., Asahara M., Hayashi A., Tsuboi N.

International Journal of Hydrogen Energy 42 ( 10 ) 7120 - 7134 2017年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017A three-dimensional (3D) strongly under expanded hydrogen jet flow is numerically investigated with a storage pressure of 82 MPa and a tiny jet orifice diameter of 0.2 mm. The full compressible Navier–Stokes equations are utilized in a domain with a size of about 3 × 3 × 6 m which is discretized by employing adaptive mesh refinement (AMR) technology to reduce the number of grid cells. The highly under expanded hydrogen jet flow with a nozzle pressure ratio (NPR) of about 809 is then captured from the very beginning when hydrogen is ejected out of the jet orifice. The starting transient evolution and Mach disk stabilization are then discussed in details. It is found that with the AMR technology, the grid number can be greatly reduced and high resolutions can be easily installed to deal with the small jet orifice size together with those flow microscales. Jet flow is numerically captured and discussed. It is found that over expansion occurs in this under expanded jet. The secondary shock is generated to match the pressure which plays the most important physics in the starting transient period of an under expanded hydrogen jet. The Mach shock and the lateral barrel shock which are originated from the secondary shock play central roles. The jet flow is divided into subsonic and supersonic branches in the near-nozzle region, which makes the highly under-expanded jets have two annular shear layers, the inner and outer layer, in this region.

DOI： 10.1016/j.ijhydene.2017.01.016

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Three-dimensional numerical simulation on dispersion process of unsteady high pressure hydrogen jet flow 査読有り

Tsuboi N., Fujimoto K., Muto D., Asahara M., Hayashi A.

AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting 2017年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 by the authors.The numerical simulations on the high-pressure hydrogen jet are performed by using the unsteady three-dimensional compressible Navier-Stokes equations with multi-species conservation equations. The present numerical results show that the highly expanded hydrogen free jet observes and the distance between the Mach disc and the nozzle exit agrees well with the empirical equation. The time-averaged H2 concentration of the numerical simulations agrees well with the experimental data and the empirical equation. The unsteady feature in the present numerical simulation shows that the PDF of the numerical simulations does not agree with the Gaussian PDF because the jet flow is “potential core” flow at x = 60 mm. Although higher hydrogen concentration is observed at x = 120 mm, the PDF in the numerical simulations agrees well with the Gaussian PDF at x = 180 mm. The numerical simulation of ignition in hydrogen jet is performed to show that the calculated OH distribution becomes isotropic expansion in the initial stage; however, OH flows along the leeward direction.

DOI： 10.2514/6.2017-1232

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Numerical simulation for effects of pressure on cryogenic coaxial jet under supercritical pressure 査読有り

Araki T., Muto D., Terashima H., Tsuboi N.

AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting 2017年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 by Rolls-Royce North America Holdings Inc.Three-dimensional numerical simulations of coaxial nitrogen jet mixing under supercritical pressures are performed with an emphasis on the effects of pressure on the mixing. The results show that the overall mixing behaviors are similar in terms of normalized density profiles between 5 and 12 MPa. However, the normalized temperature profiles are different between two conditions because non-linear change of the density to the temperature near the critical point. The peak of the constant pressure specific heat is particularly observed in the case of 5 MPa. The density and temperature fluctuations become large between the inner jet flow and the outer jet flow. Although the density fluctuation distributions are similar between two cases, the larger fluctuation region of temperature is observed in the case of 5 MPa. This is because the temperature increases are different near the critical temperature between two pressure conditions.

DOI： 10.2514/6.2017-1108

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Front cellular structure and thrust performance on hydrogen-oxygen rotating detonation engine 査読有り

Tsuboi N., Eto S., Hayashi A., Kojima T.

Journal of Propulsion and Power 33 ( 1 ) 100 - 111 2017年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Copyright © 2016 by the authors.Numerical simulations of three-dimensional rotating detonation engines for a hydrogen-oxygen mixture are performed using the detailed chemistry model. The grid-resolution study indicates that the cellular structure of the detonation appears near the inner wall as the circumferential grid resolution increases. However, the effects of the grid resolution are small on Isp. The grid resolution for the high-mass-flow cases should be carefully considered because the rotating detonation velocity increases to produce higher thrust under the low grid resolution. As the annular width increases, a complicated shock structure such as a Mach stem appears, and the cycle time decreases. The effects of the annular width are smallon Isp. As the number of the rotating detonations increases, the asymmetric detonation heads rotate along the circumferential direction with the same cycle time after 30 cycles. Isp for the two-waved rotating detonation engine decreases approximately 10% less than Isp for the one-waved rotating detonation engine. This is because the injected mixture mass flow rate for the two-waved rotating detonation engine increases 16% larger than that for the one-waved rotating detonation engine, whereas the thrusts between them coincide.

DOI： 10.2514/1.B36095

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Three-Dimensional Numerical Simulation of a Rotating Detonation Engine: Effects of the Throat of a Converging-Diverging Nozzle on Engine Performance 査読有り

Eto S., Tsuboi N., Takayuki K., Hayashi A.

Combustion Science and Technology 188 ( 11-12 ) 2105 - 2116 2016年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016 Taylor & Francis.The effect of a converging-diverging nozzle on the performance of a rotating detonation engine was estimated using three-dimensional numerical simulations with a detailed chemical reaction model. The nozzle in this article is composed of a long constant cross section, a short converging section, and a diverging section. The expansion area ratios of nozzles A and B in this article are 2.0 and 1.89, respectively. The periodic exhaust oscillation due to rotating detonation is considerably reduced by nozzle A. The variation of the time-averaged pressure is approximately 0.0048 MPa and the ratio to the time-averaged value is 1.3%. For nozzle B, the variation in pressure is approximately 0.018 MPa, and the ratio to the time-averaged value is 5%. The specific impulse of nozzle A increases by approximately 11 s (3.8%) compared with the value of nozzle B.

DOI： 10.1080/00102202.2016.1213990

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Study on Behavior of Methane/Oxygen Gas Detonation Near Propagation Limit in Small Diameter Tube: Effect of Tube Diameter 査読有り

Yoshida K., Hayashi K., Morii Y., Murakami K., Tsuboi N., Hayashi A.

Combustion Science and Technology 188 ( 11-12 ) 2012 - 2025 2016年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016 Taylor & Francis.The unstable behavior of the detonation is an important issue in predicting detonation limits and safety problems. The present study aims to obtain information of the unstable behavior near the detonation propagating limit in methane/oxygen gas mixture for various initial pressures and tube diameters. The detonation velocity rapidly decreases near α = 1.0 and deviates from the theoretical value for α < 1.0 conditions (α = πd/λ; d: tube diameter; λ: cell width). The onset of the single-head spinning is α = 1.0. For α < 1.0 conditions, the transition to the single-head spinning from small cells and the failure of cellular patterns were observed. For α > 1.0 conditions, the propagation mode was unstable. The unstable phenomenon means that the cellular pattern repeats multi-head and single-head spinning in turn.

DOI： 10.1080/00102202.2016.1213989

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84992702450&origin=inward

Numerical Study on Direct Initiation of Cylindrical Detonation in H<inf>2</inf>/O<inf>2</inf> Mixtures: Effect of Higher-Order Schemes on Detonation Propagation 査読有り

Niibo T., Morii Y., Ashahara M., Tsuboi N., Hayashi A.

Combustion Science and Technology 188 ( 11-12 ) 2044 - 2059 2016年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016 Taylor & Francis.This aim of this study is to investigate the effect of grid resolution and higher-order accuracy schemes. The size of the reaction induction zone at the time of the local explosion affects the generation of transverse cells. When the reaction zone is large, transverse cells appear. As a result, for calculations in which the grid width is small or for a higher-order scheme, such as a weighted compact nonlinear scheme (WCNS), is used, the cell size increases; an irregular cellular structure is obtained, such as that observed in experiments; and unburned gas pockets and circulation structures caused by Kelvin–Helmholtz instability appear behind the detonation front. In terms of the computational cost, the computational time of 7th-order WCNS is approximately three times that of the 2nd-order monotone upstream-centered schemes for conservation laws (MUSCL) scheme.

DOI： 10.1080/00102202.2016.1215109

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84992730237&origin=inward

D-08 液体燃料ロケットタンク破壊時の推進剤ジェット・主流の干渉構造に関する数値解析

岩佐聡洋, 武藤大貴, 藤本圭一郎, 坪井伸幸

日本機械学会九州支部講演論文集 2016 ( 69 ) 141 - 142 2016年03月

E-23 分子シミュレーションを用いた超臨界混合系における古典的混合則の精度検証

谷口正興, 津田伸一, 坪井伸幸

日本機械学会九州支部講演論文集 2016 ( 69 ) 215 - 216 2016年03月

Numerical Analyses on Ethylene/Oxygen Detonation with Multi-step Chemical Reaction Mechanisms: Grid Resolution and Chemical Reaction Model 査読有り

Takayuki Araki, Keisuke Yoshida, Youhi Morii, Nobuyuki Tsuboi, A. Koichi Hayashi

Combustion Science and Technology 188 ( 3 ) 346 - 369 2016年03月

Numerical simulation of jet mixing in a recessed coaxial injector at supercritical pressure 査読有り

Muto D., Terashima H., Tsuboi N.

54th AIAA Aerospace Sciences Meeting 2016年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Three-dimensional numerical simulations of cryogenic coaxial jets under supercritical pressure are performed with flushed and recessed injectors to investigate the effect of a recess on the coaxial mixing. A hybrid ILES/RANS method is applied to simulate wallbounded injectors and a recessed region. The recessed injector enhances the density decay and the temperature increase on the central axis, indicating the improvement of mixing compared with the flushed injector. However, the mixing improvement by the recess is not significant in the present conditions. The recess also induces distinct vortex rings around the outer jet. The power spectra of the velocity fluctuations also demonstrated that the low-frequency velocity fluctuations are clearly induced by the recess which frequency corresponds to the large vortex structures.

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Numerical simulation of the effects of nozzle on thrust performance of rotating detonation engine 査読有り

Eto S., Watanabe Y., Tsuboi N., Kojima T., Hayashi A.

Science and Technology of Energetic Materials 77 ( 5-6 ) 122 - 127 2016年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

The effects of the converging-diverging (CD) nozzle on the thrust performance of the rotating detonation engine (RDE) were estimated by using the three-dimensional numerical simulations with the detailed chemical reaction model. The nozzle geometry is based on the reference of Rankin et al. The nozzle is composed of the long constant cross section, the short converging section, and the diverging section. The periodic exhaust oscillation is considerably reduced by the present CD nozzle. The pressure difference from the averaged value is approximately 1.2 % and the difference in Mach number is approximately 0.4 %. The increment of Isp using the CD nozzle is approximately 15 s. The nozzle performance is estimated via the thrust coefficient. The thrust coefficient of the CD nozzle used this study is nearly corresponded with the ideal value. The combustion efficiency of C∗ ηc∗ are obtained 92-98 % between the combustion chamber pressure of 1.2 and 2.9 MPa.

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自由回転軸を持つ翼型を用いた円柱の抗力低減方法について査読有り

佐藤一志, 吹場活佳, 坪井伸幸

日本航空宇宙学会論文集 64 ( 3 ) 153 - 159 2016年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

A novel drag reduction method for a cylinder using a pivoted airfoil is proposed in this study. The pivoted airfoil can rotate freely on a shaft so that the airfoil can head windward. First, we conducted a water tunnel test to validate the drag reduction method. Contrary to our expectation, the airfoil did not head windward completely. The airfoil started to move from an initial angle of 0º to a stable angle of about 14º. Next, we calculated the aerodynamic force of the airfoil by a computational fluid dynamics (CFD) method. The reason the airfoil did not head windward completely was revealed. This is because the sign of the moment coefficient around the rotating shaft changes with increasing angle of attack. The CFD simulation also revealed that the drag reduction method can decrease the drag by 34%.

DOI： 10.2322/jjsass.64.153

その他リンク： http://ci.nii.ac.jp/naid/130005154803

Characteristics of Jet-Mixing at Supercritical Pressure: Effects of Recess Length and Post Height 査読有り

MUTO Daiki, TERASHIMA Hiroshi, TSUBOI Nobuyuki

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 14 ( 30 ) Pa_45 - Pa_52 2016年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Effects of injector geometries on cryogenic co-flowing planar jets under a supercritical pressure are numerically investigated. The present study covers a wide range of injector exit geometries which focuses post lip height and recess length, and evaluates these effects on mixing characteristics. A hybrid ILES/RANS methodology is applied to simulate wall-bounded injector regions. The results show that thicker post lips generate larger vortices behind the post lip, resulting the comb-like structure of the rolled-up inner dense jet. As a result, the mixing is well improved, and the inner jet potential core is shortened. The recessed injectors additionally induce a large-scale flapping motion of the inner jet and further enhance the mixing. The frequency analysis with velocity fluctuations demonstrates that the vortex shedding behind the post lip has a frequency which depends on the post lip height. The recessed injectors induce another low-frequency peak of the flapping motion, and which value is independent of the post lip height.

DOI： 10.2322/tastj.14.Pa_45

その他リンク： http://ci.nii.ac.jp/naid/130005172064

極低温超臨界圧下の噴流に関する流体力学とその数値解析

坪井伸幸

日本燃焼学会誌 ( 日本燃焼学会 ) 57 ( 182 ) 257 - 264 2015年11月

D121 管内高圧水素噴流による自着火機構(OS-10:火災・爆発(2))

朝原誠, 横山瑛紀, 窪田智之, 佐分利禎, 和田有司, 茂木俊夫, 坪井伸幸

熱工学コンファレンス講演論文集 2015 "D121 - 1"-"D121-2" 2015年10月

記述言語：日本語掲載種別：研究論文（その他学術会議資料等）

This paper deals with a self-ignition mechanism of high-pressure hydrogen jet in a tube filled with air. Although the self-ignition phenomenon is expected to clarify for industrial safety, the ignition mechanism in a tube still has not been known well. In this study, the direct photographs of flame behaver initiated by the self-ignition are captured by a high speed camera. The flame propagation histories are obtained from the pressure and light sensors. Additionally, a numerical simulation is performed to understand the ignition process induced by hydrogen jet in detail. As the results, a self-ignition occurs at the region where the contact surface interacts with the local high-temperature region which is built by the shock wave reflects from the sidewall of tube.

その他リンク： http://ci.nii.ac.jp/naid/110010045446

Numerical simulation on low-speed hydrogen jet diffusion 査読有り

Yuki Takatori, Nobuyuki Tsuboi, Keisuke Fujimoto, Daiki Muto, Makoto Asahara

The 6th International Conference on Hydrogen Safety ID179 2015年10月

J0540307 二原子分子流体の臨界点近傍における静的・動的ゆらぎ構造の分子動力学的解析

井川祥平, 永島浩樹, 坪井伸幸, 徳増崇, 津田伸一

年次大会 : Mechanical Engineering Congress, Japan 2015 "J0540307 - 1"-"J0540307-5" 2015年09月

記述言語：日本語掲載種別：研究論文（その他学術会議資料等）

In our study, we investigated fluctuation structure of diatomic fluids around the critical point. We used molecular dynamics simulation to evaluate the principle of corresponding state of fluctuation structure of 2-center-Lennard-Jones fluid which has molecular elongation as a parameter. We evaluated the static fluctuation structure by calculating dispersion of number of molecules at divided cells and static structure factor. As results, the principle of corresponding state on the static fluctuation structure is satisfied because static fluctuation structure does not have dependence on molecular elongation. On the other hand, dynamic fluctuation structure of fluid which has longer molecular elongation disagrees with dynamic fluctuation structure of fluid which has shorter molecular elongation. Therefore, it was found that the principle of corresponding state of dynamic fluctuation structure might not be satisfied.

その他リンク： http://ci.nii.ac.jp/naid/110010048952

Three-dimensional cellular structure and propagation process of spherical detonation 査読有り

R. Iida, M. Asahara, A. Hayashi, N. Tsuboi

25th International Colloquium on the Dynamics of Explosions and Reactive Systems No.273 2015年08月

Behavior of Methane/Oxygen Gas Detonation near Propagating Limit in Small Diameter Tube:Effect of Tube Diameter 査読有り

K. Yoshida, K. Hayashi, Y. Morii, K. Murakami, A. Susa, N. Tsuboi, A. Hayashi

25th International Colloquium on the Dynamics of Explosions and Reactive Systems No.139 2015年08月

3D Numerical Simulation on Rotating Detonation Engine: Effects of Converging-Diverging-Nozzle on Thrust Performance 査読有り

Seiichiro ETO, Yusuke WATANABE, Nobuyuki TSUBOI, Takayuki KOJIMA, A. Koichi HAYASHI

25th International Colloquium on the Dynamics of Explosions and Reactive Systems No.132 2015年08月

Numerical Study on Direct of Cylindrical Detonation in H2/O2 Mixture: Influence of Higher-order Scheme 査読有り

Tomotaka NIIBO, Youhi MORII, Nobuyuki TSUBOI, Makoto ASAHARA, A. Koichi HAYASHI

25th International Colloquium on the Dynamics of Explosions and Reactive Systems No.136 2015年08月

デフラグレーションからデトネーションへの遷移過程における新展開 -音速近傍で伝播する火炎の存在-

朝原誠，坪井伸幸，石井一洋，林光一

Explosion ( 日本火薬学会 ) 25 ( 1 ) 16 - 21 2015年04月

円筒デトネーションの伝播過程とセル構造に関する数値解析査読有り

朝原誠，飯田遼平，林光一，坪井伸幸

Explosion 25 ( 1 ) 8 - 15 2015年04月

Extraction of the Density Fluctuations in Diatomic Fluids Around the Critical Points Using Molecular Dynamics Simulation 査読有り

Shin-ichi Tsuda, Masato Tomi, Nobuyuki Tsuboi, Shohei Ikawa, and Takashi Tokumasu

Journal of Nanoscience and Nanotechnology 15 ( 4 ) 3117 - 3120 2015年04月

Numerical simulation of propagation process and cellular structure of cylindrical detonation 査読有り

Asahara M., Iida R., Hayashi A., Tsuboi N.

Explosion 25 ( 1 ) 8 - 15 2015年01月

New page of deflagration to detonation transition - Flame propagation around a speed of sound 査読有り

Asahara M., Tsuboi N., Ishii K., Hayashi A.

Explosion 25 ( 1 ) 16 - 21 2015年01月

Reactive fluid Dynamics laboratory Department of Mechanical and Control Engineering, Faculty of Engineering, Kyushu Institute of Technology

Tsuboi N.

Explosion ( Explosion ) 25 ( 3 ) 198 - 199 2015年01月

Three-Dimensional Simulation on Deflagration-to-Detonation Transition with a Detailed Chemical Reaction Model 査読有り

Takuya Machida, Makoto Asahara, A. Koichi Hayashi, Nobuyuki Tsuboi

Combustion Science and Technology 186 ( 10-11 ) 1758 - 1773 2014年12月

Implementation of Weighted Compact Nonlinear Scheme for Hydrogen/Air Detonation 査読有り

Ryohei Iida, Makoto Asahara, A. Koichi Hayashi, Nobuyuki Tsuboi, Taku Nonomura

Combustion Science and Technology 186 ( 10-11 ) 1736 - 1757 2014年12月

Aerodynamic Characteristics of Simplified Waveriders 査読有り

Haruka Etoh, Nobuyuki Tsuboi, Yusuke Maru, Kazuhisa Fujita

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 12 ( ists29 ) Pg_25 - Pg_31 2014年12月

Numerical simulation of auto-ignition induced by high-pressure hydrogen release with detailed reaction model: Fluid dynamic effect by diaphragm shape and boundary layer 査読有り

M.Asahara, A. Yokoyama, A.Koichi Hayashi, E. Yamada, N. Tsuboi

International Journal of Hydrogen Energy 39 20378 - 20387 2014年12月

Numerical Study of Real Gas Effects on Shock Tube Problems 査読有り

Daiki Muto, Hiroshi Terashima, Nobuyuki Tsuboi

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 12 ( ists29 ) Po_2_39 - Po_2_44 2014年12月

Estimation of the Thrust Performance on a Rotating Detonation Engine for a Hydrogen-Oxygen Mixture 査読有り

Nobuyuki Tsuboi, Yusuke Watanabe, Takayuki Kojima, and A.Koichi Hayashi

Proceedings of the Combustion Institute, The Combustion Institute 35 2005 - 2013 2014年11月

Spinning detonation , cross-currents, and the Chapman-Jouguet velocity 査読有り

M. Kurosaka, N. Tsuboi

Journal of Fluid Mechanics 756 728 - 757 2014年10月

二原子分子流体の臨界点近傍におけるゆらぎ構造の分子動力学計算査読有り

冨正人，井川祥平，坪井伸幸，徳増崇，津田伸一

日本機械学会論文集 80 ( 816 ) TEP0231 2014年08月

Effect of pressure-dependent detailed chemical reaction models on detonation cell size 査読有り

Koji Yamashita, Makoto Asahara, Koichi Hayashi, N. Tsuboi

Tenth International Symposium in Hazards, Preventation, and Mitigatikon of Industrial Explosion (X ISHPMIE) #65 2014年06月

Multi-dimensional propagation process of diverging detonation 査読有り

Ryohei Iida, Makoto Asahara, Nobuyuki Tsuboi, Koichi Hayashi

Tenth International Symposium in Hazards, Preventation, and Mitigatikon of Industrial Explosion (X ISHPMIE) #64 2014年06月

直接起爆による酸水素爆轟波の爆轟限界近傍における数値解析査読有り

朝原誠，林光一，坪井伸幸

Science and Technology of Energetic Materials 75 ( 4 ) 99 - 105 2014年05月

An Analysis of Quantum Effects on the Thermodynamic Properties of Cryogenic Hydrogen Using the Path Integral Method 査読有り

Hiroki Nagashima, Shin-ichi Tsuda, Nobuyuki Tsuboi,A. Koichi Hayashi, and Takasih Tokumasu

THE JOURNAL OF CHEMICAL PHYSICS 134506-1-10 2014年04月

Numerical study of cryogenic coaxial jet under supercritical condition 査読有り

Muto D., Tsuboi N., Terashima H.

52nd Aerospace Sciences Meeting 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2014, American Institute of Aeronautics and Astronautics Inc. All rights reserved.Effects of recess on the mixing of the cryogenic coaxial jet under supercritical conditions were numerically investigated. Recessed injectors have been applied as coaxial injectors of liquid rocket engines because it is expected to improve propellant mixing and combustion efficiency. In the present study, a numerical simulation code was developed to examine jet mixing under the supercritical pressures. For validation of the present method, a two-dimensional planner jet simulation was carried out. The present result showed good agreement with an experimental result. As a preliminary study of coaxial jets, co-planner simulations were performed in a recessed case and an unrecessed case. Large-scale vortical structures were observed in the both cases, and the recessed case showed the larger struc- tures relative to the unrecessed case. This is because of the destabilization mechanism of a recessed region. These instabilities improved entrainments of ambient uid, and as a result, the enhanced jet mixing shortens the jet-core length.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84938403091&origin=inward

Numerical simulation on ignition with shock tube - Effect of reflected shock wave - Boundary layer at adiabatic wall interaction on ignition 査読有り

Asahara M., Machida T., Yamada E., Hayashi A., Tsuboi N.

Science and Technology of Energetic Materials 75 ( 1-2 ) 50 - 58 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

A reflected shock wave in two-dimensional shock tube is studied numerically using Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. The results reproduced mild and strong ignition behind the reflected shock wave, in particular, the detailed mild ignition process, which was not shown well in past research. Owing to the interaction between the viscous boundary layer and the reflected shock wave, the latter has a lambda shock configuration. The flow behind the lambda shock wave becomes a complex vortical structure ; thus, the reactive gas mixture flowing along the detached vortices reaches high temperature and pressure because of compression at the tube side walls. The chemical reaction starts at the location that reaches the auto-ignition temperature to create flame kernels. The above history is appropriate for the process in which a flame kernel appears at the location between the triple point of the lambda shock wave and the tube wall but is insufficient for the process in which a flame kernel appears near the tube center, which is above the triple point of the lambda shock wave.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84904443456&origin=inward

Numerical simulation on H<inf>2</inf>-O<inf>2</inf> detonation induced by direct initiation near detonation limits 査読有り

Asahara M., Hayashi A., Tsuboi N.

Science and Technology of Energetic Materials 75 ( 3-4 ) 99 - 105 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

In order to prevent an accidental explosion by detonation it is necessary to clarify detonation limit and to comprehend its ignition condition. In the past experimental studies were performed to understand critical initiation energy and critical energy density and to propose detonation limit by initiation energy and energy density. However extracting dominant parameters for detonation continuation is difficult because various experimental conditions to compare for detonation continuation are not definitely consistent Therefore these parameters will be put in order by numerically analyzing 2D direct initiation of detonation in oxyhydrogen mixture assuming ideal ignition conditions, and will be clarified for detonation limits. As a result it is found that there exist the conditions for detonation and explosion. These conditions are organized to obtain a detonation limit curve which is quite similar curve shown by Watt and Sharpe. The obtained detonation limit curve is found to be a function of a radius and pressure of initial source region and to give a prediction of the critical source energy for detonation with those initial conditions Additionally a local explosion is predicted near the x-axis boundary under a quasi-steady state condition because of a disturbance there and this type of local explosion was observed by Bach et aL.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84916939418&origin=inward

An analysis of the quantum effect on the thermodynamic and transport properties of cryogenic hydrogen using molecular dynamics method 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Hayashi A., Tokumasu T.

Journal of Physics: Conference Series 490 ( 1 ) 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this paper, we have analysed an effect of quantum nature of the hydrogen molecule on its thermodynamic and transport properties using molecular dynamics (MD) method based on the path integral method. We performed NVE constant MD simulation and the quantum effect on the molecular mechanism was analysed. The simulation results were compared with experimental data. As a result, we clarified that the quantum nature makes the virial pressure larger than in classical mechanics and taking account the quantum nature makes smaller intermolecular interaction energy and larger repulsive force than classical representation. Besides, we have confirmed that the path-integral-based MD method well reproduces the thermal conductivity and quantum effect on the transport properties is also large. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/490/1/012160

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84896979582&origin=inward

A molecular dynamics study of nuclear quantum effect on the diffusion of hydrogen in condensed phase 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Hayashie A., Tokumasu T.

AIP Conference Proceedings 1618 950 - 953 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2014 AIP Publishing LLC.In this paper, the quantum effect of hydrogen molecule on its diffusivity is analyzed using Molecular Dynamics (MD) method. The path integral centroid MD (CMD) method is applied for the reproduction method of time evolution of the molecules. The diffusion coefficient of liquid hydrogen is calculated using the Green-Kubo method. The simulation is performed at wide temperature region and the temperature dependence of the quantum effect of hydrogen molecule is addressed. The calculation results are compared with those of classical MD results. As a result, it is confirmed that the diffusivity of hydrogen molecule is changed depending on temperature by the quantum effect. It is clarified that this result can be explained that the dominant factor by quantum effect on the diffusivity of hydrogen changes from the swollening the potential to the shallowing the potential well around 30 K. Moreover, it is found that this tendency is related to the temperature dependency of the ratio of the quantum kinetic energy and classical kinetic energy.

DOI： 10.1063/1.4897890

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84947543854&origin=inward

Numerical Study of Real Gas Effects on Shock Tube Problems at Supercritical Conditions 査読有り

MUTO Daiki, TSUBOI Nobuyuki, TERASHIMA Hiroshi

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN ( 一般社団法人日本航空宇宙学会 ) 12 ( 29 ) Po_2_39 - Po_2_44 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Investigations of real gas effects of supercritical fluids on shock tube problems were numerically performed. Understandings of fluid behaviors under supercritical conditions are essential for the design of high pressure combustors. We developed a numerical code for simulations of flow fields under the supercritical conditions. Cubic types of equation of state are applied to evaluate properties of nearcritical and supercritical fluids. The present code was tested on shock tube problems, and the present result agreed well with a reference result. Comparisons of results between the real gas equations of state and the ideal gas equation of state showed differences in position of shock waves, contact discontinuities, and expansion fans due to the specific thermodynamic features of the supercritical fluids. In a condition that crosses the critical point, the results showed a large density jump with a small temperature jump at the contact discontinuity because of drastic changes of thermodynamic properties. This indicated that the real gas effects obviously appear when the initial condition is close to the critical point of the working fluids.

DOI： 10.2322/tastj.12.Po_2_39

その他リンク： https://ci.nii.ac.jp/naid/130004956821

J0550204 分子動力学法による液体水素の輸送物性に対する量子効果の影響解析([J055-02]マイクロ・ナノスケール熱流体現象(2))

永島浩樹, 津田伸一, 坪井伸幸, 越光男, 林光一, 徳増崇

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _J0550204 - -_J0550204- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we conducted analysis of quantum effect of hydrogen molecules on the energy transport of liquid hydrogen using classical Molecular Dynamics (MD) and path integral Centroid MD (CMD) method. We performed MD simulation across a wide temperature region in the constant density and compared the thermal conductivity of each method. The thermal conductivity was calculated using non-equilibrium MD method. As a result, it was confirmed that CMD shows lower thermal conductivity than classical MD and this tendency is consistent with experimental data. Moreover, it was clarified that because of the change of intermolecular potential due to the quantum effect, the potential energy transport by molecular motion and the energy transport by intermolecular interaction decrease.

DOI： 10.1299/jsmemecj.2014._J0550204-

その他リンク： https://ci.nii.ac.jp/naid/110009943927

J0550104 分子動力学シミュレーションによる臨界点近傍のニ原子分子流体に対する密度ゆらぎの評価([J055-01]マイクロ・ナノスケール熱流体現象(1))

井川祥平, 徳増崇, 坪井伸幸, 津田伸一

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _J0550104 - -_J0550104- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we investigated the density fluctuation of diatomic fluids around the critical points for evaluation of the principle of corresponding state. We used Molecular Dynamics (MD) simulation against the 2-Center Lennard-Jones (2CLJ) fluids for extraction of structure of fluctuation around the critical points. We evaluated the density fluctuation by two methods. One is the dispersion of number of molecules at certain domain as time-averaged quantity. The other is the calculation of static structure factor. As the results, in 2CLJ fluids that have shorter molecular elongations comparatively, the principle of corresponding state is satisfied because of the small difference in the fluctuation structure extracted by the present two methods.

DOI： 10.1299/jsmemecj.2014._J0550104-

その他リンク： https://ci.nii.ac.jp/naid/110009943922

G0510306 3次元数値解析による高圧水素噴流の管内における自着火機構の解明([G051-03]流体工学部門一般セッション(3),流体工学部門)

横山瑛紀, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510306 - -_G0510306- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

One of self-ignition mechanisms of high-pressure hydrogen jet occurs by vortex caused from instability. Several studies about self-ignition of high-pressure hydrogen spouted from a tube attached with a tank are reported. In this analysis, the numerical study is performed to find out mechanism of self-ignition of hydrogen jet in a tube with a 10mm in diameter connected to a high pressure tank of 9.0MPa. Hydrogen and air are mixed at their contact surface to yield vortices, and the mixture ignites because the high temperature and high pressure regions are yielded behind the precursor shock wave.

DOI： 10.1299/jsmemecj.2014._G0510306-

その他リンク： https://ci.nii.ac.jp/naid/110009943304

G0510305 反射衝撃波と境界層の干渉による流れの3次元挙動に関する数値解析([G051-03]流体工学部門一般セッション(3),流体工学部門)

若林諒, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510305 - -_G0510305- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

At the reflected shock rear, a chemical reaction starts at a temperature and pressure constant static premixed gas conditions by filling reactive premixed gas in the shock tube, and reflects the shock wave in the pipe ends. Meyer and Oppenheim were classified into ignition two forms Mild Ignition and Strong Ignition, the start of the H2/O2 detonation due to the reflected shock wave. In order to ignite instantly in the tube cross-section of the entire near-wall reflection, Strong Ignition is a form ignition reaction theory. Mild Ignition is a firing mode hydrodynamic, under the influence of lambda shock wave generated by the mutual interference between the boundary layer and are reaching the ignition shock wave backward flow becomes multidimensional. Mark was revealed from the experiment due to the mutual interference between the boundary layer and the reflected shock, lambda shock wave to be formed in connection with this phenomenon. Thus, experiments by the reflected shock ignition is performed, there are cases in which ignition occurs is unexpected due to the interference of the reflected shock wave and boundary layer. In this study, we focus on the flow field due to the interference of the boundary layer and reflected shock, it is an object of the present invention to elucidate the flow three-dimensional.

DOI： 10.1299/jsmemecj.2014._G0510305-

その他リンク： https://ci.nii.ac.jp/naid/110009943303

G0510304 矩形管内を伝播するデトネーション波の多頭構造に関する3次元数値解析([G051-03]流体工学部門一般セッション(3),流体工学部門)

朝原誠, 長尾剛史, 坪井伸幸, 林光一

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510304 - -_G0510304- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

Three-dimensional numerical analysis using practical scale of the experiment is performed to obtain cellular structure in rectangular tube. As a result, transverse wave in three-dimensions moves in different direction comparing with two-dimensional structure at the point of propagation structure. Furthermore, each transverse wave affects to accelerate the propagation velocity in circumferential direction and makes unreacted gas pockets after transverse wave goes through each other.

DOI： 10.1299/jsmemecj.2014._G0510304-

その他リンク： https://ci.nii.ac.jp/naid/110009943302

G0510303 数値解析によるローテーティングデトネーションエンジンの推力性能に関する研究([G051-03]流体工学部門一般セッション(3),流体工学部門)

吉田航, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510303 - -_G0510303- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

Study of detonation engine has been actively carried out in order to improve the thrust performance and expected to apply rocket engine. Even among them, rotating detonation engine has attracted attention. Many experiments have been performed, but in the experiments, varying the combustion chamber size is difficult. In this study, the numerical study is carried out to find out thrust performance with changing combustion chamber size.

DOI： 10.1299/jsmemecj.2014._G0510303-

その他リンク： https://ci.nii.ac.jp/naid/110009943301

806 ローテーティングデトネーションエンジンの運転条件と性能評価 : 格子解像度がIspに与える影響

渡辺裕介, 坪井伸幸, 原野孝也, 小島孝之, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _806 - 1_-_806-2_ 2014年01月

802 超臨界圧力下における極低温同軸噴流への噴射器形状の及ぼす効果に関する数値解析

武藤大貴, 坪井伸幸, 寺島洋史

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _802 - 1_-_802-2_ 2014年01月

B213 分子動力学シミュレーションによる二原子分子流体の臨界点近傍における密度ゆらぎに関する研究

井川祥平, 徳増崇, 坪井伸幸, 永島浩樹, 津田伸一

熱工学コンファレンス講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _B213 - 1_-_B213-2_ 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we evaluated the density fluctuation of diatomic fluids around the critical point. We performed Molecular Dynamics (MD) simulation against 2-Center-Lenard-Jones (2CLJ) fluids that have molecular elongation as a parameter. We compared the density fluctuation of each fluid to evaluate the principle of corresponding state of density fluctuation. We evaluated the density fluctuation by dispersion of number of molecules, static structure factor, and intermediate scattering function. As the results, in 2CLJ fluids that have shorter molecular elongation comparatively, the principle of corresponding state of static fluctuation structure was satisfied.

DOI： 10.1299/jsmeted.2014._B213-1_

その他リンク： https://ci.nii.ac.jp/naid/110009938965

811 ハイブリッドロケット内部の3次元非定常圧縮性流れの数値解析 : 乱流モデルによる影響

坂本まい, 武藤大貴, 坪井伸幸

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _811 - 1_-_811-2_ 2014年01月

808 数値解析によるエアロスパイクノズルの性能評価 : 内部ノズルの性能評価

芝尾将史, 坪井伸幸, 伊藤隆

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _808 - 1_-_808-2_ 2014年01月

804 Waverider形状の熱的影響に関する数値解析

浦優介, 衞藤遥, 坪井伸幸, 丸祐介, 藤田和央

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _804 - 1_-_804-2_ 2014年01月

523 固体高分子形燃料電池触媒層一次細孔内の酸素輸送挙動に関する分子動力学的解析

出口将嗣, 福島啓悟, 坪井伸幸, 徳増崇

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _523 - 1_-_523-2_ 2014年01月

219 極超音速流れにおけるランプ模型周りの場数値解析 : ランプ角度の影響

黒川久仁彦, 坪井伸幸, 倉本健史

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _219 - 1_-_219-2_ 2014年01月

1404 H_2/O_2混合気中における衝撃波収束による着火の機構に関する数値解析

朝原誠, 三谷奈々, 坪井伸幸

流体工学部門講演会講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _1404 - 1_-_1404-2_ 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

A reflected shock wave by focusing reflector is simulated using the Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. Into the tube which has focusing end wall, ignition successes around focal point under the no-ignition condition at the flat wall. The shock focusing is one of effective way of detonation initiation. However, the ignition mechanism from shock focusing is not clear. In this study, we aim to indicate the ignition phenomena induced by shock focusing.

DOI： 10.1299/jsmefed.2014._1404-1_

その他リンク： https://ci.nii.ac.jp/naid/110009938781

102 数値計算によるローティングデトネーションエンジンの推進性能評価 : 回転デトネーションの数及び燃焼器サイズによる影響

原野孝也, 渡辺裕介, 坪井伸幸, 小島孝之, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _102 - 1_-_102-2_ 2014年01月

101 煤膜法による円管内でのメタン/酸素デトネーションのセル模様に関する実験的研究

吉田啓祐, 元永孝英, 森井雄飛, 村上清人, 須佐秋生, 坪井伸幸, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _101 - 1_-_101-2_ 2014年01月

A molecular dynamics analysis of quantum effect on the thermodynamic properties of liquid hydrogen 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Hayashi A., Tokumasu T.

ASME 2013 11th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM 2013 2013年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Liquid Hydrogen plays an important role in hydrogen energy society. Therefore it is important to understand its thermal and transport properties accurately. However cryogenic hydrogen has unusual thermodynamic properties because of its quantum nature. The thermal de Broglie wavelength of cryogenic hydrogen molecule becomes the same order as molecular diameter. Therefore, each molecular position and its momentum cannot be defined classically. Because of this nature, hydrogen molecules show higher diffusivity than classical counterpart. Until now, the effects of quantum nature of hydrogen and its mechanism on the thermodynamic properties have not been clarified in detail. Especially, how the quantum nature would effect on the energy transfer in molecular scale has not been clarified. An accurate understanding of the effect and mechanism of quantum nature is important for hydrogen storage method and energy devices which use hydrogen as a fuel. In this study, therefore, we investigated the effect of this quantum nature and its mechanism on the thermodynamic and transport properties of cryogenic hydrogen using classical Molecular Dynamics (MD) method and quantum molecular dynamics method. We applied path integral Centroid Molecular Dynamics (CMD) method for the analysis. First, we have conducted thermodynamic estimation of cryogenic hydrogen using the MD methods. This simulation was performed across a wide density-temperature range. Using these results, equations of state (EOS) were obtained by Kataoka's method, and these were compared with experimental data according to the principle of corresponding states. As a result, it was confirmed that both quantitative and qualitative effect of the quantum nature on the thermodynamic properties of hydrogen are large. It was also found that taking account the quantum nature makes larger virial pressure and weaker intermolecular interaction energy. Second, we have calculated the diffusion coefficient of liquid hydrogen to clarify the effect of the quantum nature on the transport properties. We used Green-Kubo form for the calculation using velocity autocorrelation function. The simulation was performed across a wide temperature range. CMD simulation results were compared with classical simulation results and experimental data. We clarified the effect of quantum nature on the transport properties of liquid hydrogen. Copyright © 2013 by ASME.

DOI： 10.1115/ICNMM2013-73161

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84892648397&origin=inward

An analysis of quantum effect on the p-V-T relation of cryogenic hydrogen using centroid molecular dynamics method 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Koichi Hayashi A., Tokumasu T.

Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 79 ( 805 ) 1848 - 1857 2013年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this paper, we conducted analysis of p-V-T relation of cryogenic hydrogen using classical Molecular Dynamics (MD) and path integral Centroid MD (CMD) method to understand an effect of quantum nature of hydrogen molecules. We performed NVE constant MD simulation across a wide density-temperature region to obtain an Equation Of State (EOS). Simulation results were compared with experimental data. As a result, it was confirmed that classical MD cannot reproduce the experimental data at the high density region. On the other hand, CMD well reproduces the thermodynamic properties of liquid hydrogen. Moreover, it was clarified that taking the quantum effect into account makes repulsion force larger and the potential well smaller. Because of this mechanism, the intermolecular interaction of hydrogen diminishes and the virial pressure increases. ©2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.79.1848

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84885115093&origin=inward

Strong and Mild Ignition Mechanism behind Reflected Shock Waves in Hydrogen Mixture 査読有り

Asahara, M., Shirakawa, Y., Hayashi, A.K. , Tsuboi, N.

5th International Conference on Hydrogen Safety No: 167 2013年09月

Numerical analysis of spinning detonation dependency on initial pressure using AUSMDV scheme 査読有り

Nagao T., Asahara M., Koichi Hayashi A., Tsuboi N., Yamada E.

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013 2013年08月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In order to investigate the fundamental characteristics of spinning detonation propagating tubes, this present study shows a numerical simulation using AUSMDV scheme which is more capable to capture detonation phenomenon clearly than TVD scheme and a detailed chemical kinetic model of H2/O2 by Petersen and Hanson. By analyzing the lower limit of spinning detonation propagation, disclosing the detonation propagation limit and the feature is the present purpose. In the numerical results, the lower limit of spinning detonation propagating in a rectangular tube has partially analyzed. The numerical results indicated the differences of the propagation limit of spinning detonation propagating in between a circular tube and a rectangular tube. Because of the number of transverse wave, spinning detonation propagating in rectangular tube is able to maintain more than circular tube's one. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84881431610&origin=inward

Numerical Study on Shock Wave Interaction over Compression Corner with 30 deg. in Hypersonic Flow 査読有り

T.Kuramoto, D.Muto, N.Tsuboi, H.Nagai, K.Asai

29th International Symposium on Shock Waves #0246-000035 2013年07月

Numerical Analysis of 3D-Rotating Detonation Engine Concerning Propagation Mechanism in Combustor Thickness Direction and Effect on its Performance 査読有り

Zusai K., Uemura Y., Asahara M., Yamada E., Hayashi A.K., Tsuboi N.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #251 2013年07月

Detailed Hydrodynamic Instability Structure at Hydrogen/Air Detonation Front Using WCNS Scheme 査読有り

Iida R., Asahara M., Tsuboi N., Nonomura T., Hayashi A.K.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #234 2013年07月

Thrust Performance Estimation on Rotating Detonation Engine Using Two-Dimensional Numerical Simulations Isp under Low-Pressure Environment 査読有り

Watanabe Y., Tsuboi N., Kojima T., Hayashi A.K.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #117 2013年07月

Experimental Study on CH4/O2 Detonation Characteristics near Propagation Limit: Influence of Initial Pressure and Equivalence Ratio on Cellular Structure 査読有り

Motonaga T., Yoshida K., Morii Y., Murakami K., Susa A., Tsuboi N., Hayashi A.K.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #237 2013年07月

Numerical Simulations on Propagating Process of H2/O2/H2O Cylindrical Detonation with Detailed Reaction Model 査読有り

Sugiyasu T., Morii Y., Tsuboi N., Asahara M., Hayashi A.K.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #158 2013年07月

Three-Dimensional Simulation on Deflagration to Detonation Transition with a Detailed Chemical Reaction 査読有り

Machida T., Fukuda M., Asahara M., Yamada E., Hayashi A.K., Tsuboi N.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #252 2013年07月

Evaluation of Chemical Reaction Models and Numerical Simulations of Detonations in C2H4/O2 Mixtures 査読有り

Araki T., Morii Y., Tsuboi N., Hayashi A.K.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #57 2013年07月

Numerical Analysis on Ignition Problem behind Reflected Shock Waves in Reactive Mixture 査読有り

Asahara M., Koyama T., Hayashi A.K., Tsuboi N.

24th International Colloquium on the Dynamics of Explosions and Reactive Systems #256 2013年07月

Numerical approach to one-dimensional CH<inf>4</inf>/O<inf>2</inf> detonation with the reduced chemical kinetic model DRG30 査読有り

Morii Y., Tsuboi N., Ogawa H., Tokudome S., Koichi Hayashi A.

Science and Technology of Energetic Materials 73 ( 5-6 ) 169 - 174 2012年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

In order to understand the effect of the CH4/O2 chemical kinetic models for detonation phenomena, the numerical calculations use one detailed chemical kinetic model k311 and four reduced chemical kinetic models such as DRG30 model, DRG23 model, Petersen & Hanson model, and Soetrisno model. At first, the calculations of laminar flame velocity and onedimensional ZND model are performed to compare with k311 model. Then, it is shown that DRG30 model is the most reliable reduced chemical kinetic model in four reduced kinetic models in these conditions. Next, the one-dimensional Euler simulations are performed with k311 model, DRG30 model, Petersen & Hanson model, and Soetrisno model. The results are discussed about detonation velocity history, and instantaneous pressure and temperature profiles. The detonations using k311, DRG30, and Petersen & Hanson models can propagate unstably, but Soetrisno model cannot reproduce a detonation. As a result, the similar features appear between the results with k311 model and DRG30 model.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84874817295&origin=inward

Numerical study and performance evaluation for a pulse detonation engine with an exhaust nozzle (1st report: Estimation on performance using a detailed reaction model) 査読有り

Kimura Y., Tsuboi N., Tsuboi N., Hayashi A., Yamada E.

Transactions of the Japan Society for Aeronautical and Space Sciences 55 ( 1 ) 51 - 59 2012年02月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

This paper presents a propulsive performance evaluation for a H 2/Air pulse detonation engine (PDE) equipped with a converging-diverging exhaust nozzle. The evaluation was conducted using system-level modeling and multi-cycle numerical simulations. This study discusses two-dimensional and axisymmetric compressible Euler equations with a detailed chemical reaction model. First, the single-shot propulsive performance of a simplified-PDE (i.e., no exhaust nozzle) is evaluated to show the validity of the numerical and performance evaluation method. The influences of the initial conditions, ignition energy, grid resolution and scale effects on the propulsive performance are studied using multi-cycle simulations. The present results are compared with the results calculated by Ma et al. and Harris et al. The differences between their results and the present simulations are approximately 2-3% because their chemical reactions use a one-step model with a single-γ model. The effects of the specific heat ratio should be estimated for various nozzle configurations and flight conditions. © 2012 The Japan Society for Aeronautical and Space Sciences.

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84856531778&origin=inward

An estimation of thermodynamic and transport properties of cryogenic hydrogen using classical molecular simulation 査読有り

Nagashima H., Tokumasu T., Tsuda S., Tsuboi N., Koshi M., Hayashi A.

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 2 289 - 299 2011年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this paper, we estimated the thermodynamic and transport properties of cryogenic hydrogen using classical molecular simulation to clarify the limit of classical method on the estimation of those properties of cryogenic hydrogen. Three empirical potentials, the Lennard-Jones (LJ) potential, two-center Lennard-Jones (2CLJ) potential, and modified Buckingham (exp-6) potential, and an ab initio potential model derived by the molecular orbital (MO) calculation were applied. Molecular dynamics (MD) simulations were performed across a wide density-temperature range. Using these data, the equation of state (EOS) was obtained by Kataoka's method, and these were compared with NIST (National Institute of Standards and Technology) data according to the principle of corresponding states. Moreover, we investigated transport coefficients (viscosity coefficient, diffusion coefficient and thermal conductivity) using time correlation function. As a result, it was confirmed that the potential model has a large effect on the estimated thermodynamic and transport properties of cryogenic hydrogen. On the other hand, from the viewpoint of the principle of corresponding states, we obtained the same results from the empirical potential models as from the ab initio potential, showing that the potential model has only a small effect on the reduced EOS: the classical MD results could not reproduce the NIST data in the high-density region. This difference is thought to arise from the quantum effect in actual liquid hydrogen. Copyright © 2011 by ASME.

DOI： 10.1115/AJK2011-36005

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84881446073&origin=inward

Dependency of Equivalence Ratio on Hydrogen Cylindrical Detonation Induced by Direct Initiation 査読有り

Asahara, M., Tsuboi, N. Hayashi, A.K. and Yamada, E.

The 4th International Conference on Hydrogen Safety (ICHS) 2011, paper no.224 2011年09月

Oscillating propagation of near-limit detonations of CH4/O2 system in a small diameter tubes 査読有り

2) Akio Susa, Nobuyuki Tsuboi, Takuma Endo, Youhi Morii, Hiroyuki Yokoyama, Syunsuke HASEGAWA, Yosuke OGAWA

23rd International Colloquium on the Dynamics of Explosions and Reactive Systems, Oral 131 2011年07月

Detailed Shock Configuration of Cylindrical Cellular Detonation 査読有り

Makoto Asahara, Nobuyuki Tsuboi, A.Koichi Hayashi

23rd International Colloquium on the Dynamics of Explosions and Reactive Systems, Oral 324 2011年07月

Numerical Simulation on Two-Dimensional Detonation including Boundary Layer Effects 査読有り

Nobuyuki Tsuboi, A.Koichi Hayashi, Youhi Morii, Mitsuo Koshi

23rd International Colloquium on the Dynamics of Explosions and Reactive Systems, Oral 187 2011年07月

Physics of Detonation Propagation in Rotating Detonation Engine 査読有り

Takayuki Yamada, Nobuyuki Tsuboi, Yuho Uemura, A.Koichi Hayashi, Eisuke Yamada

23rd International Colloquium on the Dynamics of Explosions and Reactive Systems, Poster 173 2011年07月

Fast Deflagration in the Smooth Tube in Hydrogen-Oxygen Mixture 査読有り

Edyta Dzieminska, Nobuyuki Tsuboi, A.Koichi Hayashi, Eisuke Yamada, Motoki Fukuda

23rd International Colloquium on the Dynamics of Explosions and Reactive Systems, Poster 185 2011年07月

Two-dimensional　analysis of Hydrogen/Oxygen cylindrical detonation using AUSMDV scheme 査読有り

Makoto Asahara, Nobuyuki Tsuboi, A. Koichi Hayashi, and Eisuke Yamada

Archivum　Combustions 30 ( 3 ) 177 - 186 2011年04月

Transition to detonation after a ‘volume explosion’ - Oppenheim’s experiment validation with a numerical calculation 査読有り

Edyta Dzieminska, Motoki Fukuda, A. Koichi Hayashi, Nobuyuki Tsuboi

Archivum　Combustions 30 ( 3 ) 187 - 195 2011年04月

Updated kinetic mechanism for high-pressure hydrogen combustion 査読有り

Shimizu K., Hibi A., Koshi M., Morii Y., Tsuboi N.

Journal of Propulsion and Power 27 ( 2 ) 383 - 395 2011年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

A chemical kinetic model for high-pressure combustion of H 2=O2 mixtures has ben developed by updating some of the rate constants important under high-pressure conditions without any diluent. The revised mechanism is validated against experimental shock-tube ignition delay times and laminar flame speeds. Predictions of the present model are also compared with those by several other kinetic models proposed recently. Although predictions of those models (including the present model) agree quite well with each other and with the experimental data of ignition delay times and flame speeds at pressures lower than 10 atm, substantial differences are observed between recent experimental data of high-pressure mass burning rates and model predictions, as well as among the model predictions themselves. Different pressure dependencies of mass burning rates above 10 atm in different kinetic models result from using different rate constants in these models for HO 2 reactions, especially for H + HO2 and OH + HO 2 reactions. The rate constants for the reaction H + HO2 involving different product channels were found to be very important for the prediction of high-pressure combustion characteristics. An updated choice of rate constants for those reactions is presented on the basis of recent experimental and theoretical studies. The role of O(1D), which can be produced by the H + HO2 reaction, in the high-pressure combustion of H2 is discussed. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

DOI： 10.2514/1.48553

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Mechanism of high-pressure hydrogen auto-ignition when spouting into air 査読有り

Yamada E., Kitabayashi N., Hayashi A., Tsuboi N.

International Journal of Hydrogen Energy 36 ( 3 ) 2560 - 2566 2011年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

High-pressure hydrogen leak is one of the top safety issues presently. This study elucidates numerically the physics and mechanism of high-pressure hydrogen jet ignition when the hydrogen suddenly spouts into the air through a tube. The direct numerical simulation based on the compressible fluid dynamics was carried out. When high-pressure hydrogen is passing through the tube filled by atmospheric air, a strong shock wave is formed and heats up hydrogen behind the shock wave by compression effect. The leading shock wave is expanded widely after the tube exit, auto-ignitions of hydrogen occur. When the tube becomes longer, the tendency of auto-ignition is increased. Other type of auto-ignitions is also predicted. An explosion is also occurred in the tube under a certain condition. Vortices are generated behind the shock wave in a long tube. There is a possibility of an auto-ignition induced by vortices. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2010.05.011

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Numerical Study and Performance Evaluation for Pulse Detonation Engine with an Aerospike Nozzle 査読有り

N. Tsuboi, Y. Kawakami, K. Ezure, A. Hayashi, E. Yamada

AIAA-2011-800, 49th AIAA Aerospace Sciences Meeting 2011年01月

Numerical Study on Detonation Characteristics Using a Bio-Fuel 査読有り

A. Hayashi, T.Shimada, E. Yamada, N. Tsuboi

AIAA-2011-582, 49th AIAA Aerospace Sciences Meeting 2011年01月

Numerical analysis of threshold of limit detonation in Rotating Detonation Engine 査読有り

Yamada T., Hayashi A., Yamada E., Tsuboi N., Tangirala V., Fujiwara T.

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition 2010年12月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Rotating Detonation Engine (RDE) is a new kind of detonation engine, which may provide a high performance with a smaller and simpler system than the traditional ones. In order to optimize RDE system, the threshold of detonation limit must be studied for its best design and its best run. In this paper, the following four aspects are discussed: (1) what will be happen to the rotating detonation limit when the computational area is doubled; (2) what will be happen to rotating detonation when the ignition energy is increased; (3) what will be happen to specific impulse (Isp) when the ignition energy is increased. The results show that the lower detonation limit gets the computational area effct, but the upper one does not. The max specific impulse of Ispf is about 4000 s and that of Ispm is about 450 s. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

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Combustion characteristics of hydroxylammonium nitrate aqueous solutions 査読有り

Katsumi T., Matsuda R., Inoue T., Tsuboi N., Ogawa H., Sawai S., Hori K.

International Journal of Energetic Materials and Chemical Propulsion 9 ( 3 ) 219 - 231 2010年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Hydroxylammonium nitrate (HAN) based liquid propellant has been investigated as a candidate for the monopropellant to be utilized in the reaction control system of satellites as an alternative to hydrazine. This propellant, which consists of ammonium nitrate, methanol, and water, has moderate burning characteristics, sufficiently low freezing temperature, high density, low toxicity, and its density x Isp is 70% higher than hydrazine. In a previous study, the combustion characteristics of the propellants were obtained and found to be very complex. In this paper, the research was focused on the combustion characteristics of HAN aqueous solution. Sample solutions of several concentrations, 95-50 mass %, were prepared. The measurement of linear burning rates, the temperature measurement of the combustion wave, and the observation of combustion phenomena were included in the study. The linear burning rate does not increase monotonically with increasing HAN concentration. The burning rates increase as the HAN concentration increases up to 80 mass %, and decrease as the concentration increases from 80 to 95 mass %. The burning rate peaks at around 80 mass % of HAN concentration. The combustion mode is very complex and is dependent upon composition and pressure. Temperature measurements indicate that the role of the two-phase region is very important, and the boiling of water caused by superheat is responsible for the high burning rate. The relationship between the rate of nucleation of bubbles and the linear burning rate is discussed. © 2010 by Begell House, Inc.

DOI： 10.1615/IntJEnergeticMaterialsChemProp.v9.i3.30

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Numerical investigations of film cooling effect on sub-scale rocket engine performance 査読有り

Ito T., Tsuboiy N., Miyajima H.

Transactions of the Japan Society for Aeronautical and Space Sciences 53 ( 179 ) 63 - 70 2010年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

LOX/LH 2 subscale rocket nozzle flow fields are simulated computationally using the 3D compressible Navier- Stokes equations. The area ratio of the nozzle is 140 and the film coolant hydrogen gases are injected from 30 film cooling holes distributed circumferentially at an area ratio of 13. The experimental nozzle throat Reynolds number indicates that the boundary layer of the nozzle is in its transition region as the size of the nozzle is small. A clear difference in effective specific impulses of the secondary flow between the laminar and turbulent conditions is also shown. The nozzle wall temperature also influences the nozzle performance and the experimental performances were in better agreement with the laminar computations when the wall temperature is set to 300 K, which is closer to the experimental conditions. Both turbulent and laminar computations are carried out to investigate the effect of the boundary layer conditions on the nozzle performance. The computed results show that the structure of the separated flow downstream of the film cooling injection significantly changes between the turbulent and laminar conditions. © 2010 The Japan Society for Aeronautical and Space Sciences.

DOI： 10.2322/tjsass.53.63