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

Scopus

CiNii Research

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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

CiNii Research

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

Scopus

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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）

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）

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）

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

Scopus

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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

Scopus

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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）

<p>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.</p>

DOI： 10.2322/tjsass.65.172

CiNii Research

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

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2478/tar-2021-0022

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

Scopus

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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

Scopus

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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）

DOI： 10.1299/jsmekyushu.2021.74.F33

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130008092382

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

Scopus

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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

CiNii Article

CiNii Research

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

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.

Scopus

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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

Scopus

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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）

USA   Orlando  

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

Scopus

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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）

USA   Orlando  

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）

USA   Orlando  

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

Scopus

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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

Scopus

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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

Scopus

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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）

<p>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.</p>

DOI： 10.1299/jsmesec.2020.29.C1

CiNii Article

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

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）

USA   Washington  

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）

USA   Indianapolis  

DOI： 10.2514/6.2019-4100.c1

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）

China   Beijing  

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）

China   Beijing  

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）

China   Beijing  

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）

China   Beijing  

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）

China   Beijing  

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）

Singapore   Singapore  

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）

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）

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）

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

Scopus

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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

Scopus

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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

Scopus

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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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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）

<p>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.</p>

DOI： 10.1299/jsmekyushu.2019.72.B14

CiNii Article

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

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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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）

<p>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.</p>

DOI： 10.1299/jsmekyushu.2019.72.D13

CiNii Article

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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）

<p>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 <i>ab-initio</i> 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.</p>

DOI： 10.1299/jsmemecj.2019.J05412

CiNii Article

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

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）

<p>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.</p>

DOI： 10.1299/jsmekyushu.2019.72.D12

CiNii Article

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

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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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）

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）

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）

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1080/00102202.2018.1498849

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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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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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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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1299/mel.18-00369

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）

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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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）

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）

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）

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）

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）

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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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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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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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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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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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

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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

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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）

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/110010054693

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）

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/110010054730

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）

DOI： 10.1080/00102202.2015.1106484

Scopus

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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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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記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>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.</p>

DOI： 10.2322/tastj.14.Pa_45

CiNii Article

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

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

CiNii Article

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

担当区分：責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

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.

CiNii Article

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

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）

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.

CiNii Article

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

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）

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）

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）

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）

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

記述言語：日本語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1166/jnn.2015.9623

Scopus

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

Scopus

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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）

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1080/00102202.2014.935647

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1016/j.ijhydene.2014.05.136

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1080/00102202.2014.935646

Scopus

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）

DOI： 10.1016/j.proci.2014.09.010

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1017/jfm.2014.460

Scopus

記述言語：日本語   掲載種別：研究論文（学術雑誌）

DOI： 10.1299/transjsme.2014tep0231

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）

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）

記述言語：日本語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1063/1.4870036

Scopus

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

Scopus

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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.

Scopus

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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.

Scopus

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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.

Scopus

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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

Scopus

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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）

DOI： 10.1299/jsmekyushu.2014.67._101-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951174

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-

CiNii Article

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

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-

CiNii Article

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

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-

CiNii Article

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

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-

CiNii Article

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

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-

CiNii Article

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

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

CiNii Article

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

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）

DOI： 10.1299/jsmekyushu.2014.67._102-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951175

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_

CiNii Article

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

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）

DOI： 10.1299/jsmekyushu.2014.67._219-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951222

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）

DOI： 10.1299/jsmekyushu.2014.67._523-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951304

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）

DOI： 10.1299/jsmekyushu.2014.67._804-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951365

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）

DOI： 10.1299/jsmekyushu.2014.67._808-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951369

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）

DOI： 10.1299/jsmekyushu.2014.67._811-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951372

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_

CiNii Article

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

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）

DOI： 10.1299/jsmekyushu.2014.67._802-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951363

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）

DOI： 10.1299/jsmekyushu.2014.67._806-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009951367

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-

CiNii Article

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

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

Scopus

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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

Scopus

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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）

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.

Scopus

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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）

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）

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）

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）

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）

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）

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）

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）

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）

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.

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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.

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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

Scopus

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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）

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）

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）

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）

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）

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）

記述言語：英語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

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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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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担当区分：責任著者   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）

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）

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.

Scopus

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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

Scopus

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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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記述言語：英語   掲載種別：研究論文（学術雑誌）

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1080/00102202.2010.498676

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

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担当区分：責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

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開催期間： 2017年01月   記述言語：日本語  

CiNii Article

開催期間： 2017年01月   記述言語：日本語  

CiNii Article

開催期間： 2017年01月   記述言語：日本語  

CiNii Article

開催期間： 2016年01月   記述言語：英語  

開催期間： 2016年01月   記述言語：日本語  

<p>Three-dimensional numerical simulation of high pressure hydrogen jet is performed. Hydrogen leakage from the high pressure hydrogen tank has a possibility of serious explosion accidents. Therefore, it is necessary to understand diffusion behavior and ignition characteristics of hydrogen leakage. The present study simulates the high-pressure hydrogen supersonic free jet into the atmosphere to understand the dispersion process. As a result, the Jet flow fluctuates greatly in the radial direction and hydrogen disperses in a wide sphere. Also, lambda vortex structure was found to perform a crucial function in the diffusion of hydrogen.</p>

CiNii Article

開催期間： 2016年01月   記述言語：日本語  

<p>Numerical simulations of the jet injected into supersonic cross-flow are carried out. In aborting process in liquid rocket flight, the fuel is transversely injected into the supersonic freestream. Developed jet/freestream interaction structure may trigger unexpected auto-ignition or explosion events; thus the understanding of the flow-field of jet-in-supersonic cross-flow is essential to meet the reliability of rocket. The two-dimensional numerical simulations are carried out in a wide-range of jet and freestream conditions: the jet-to-freestream momentum flux ratio and the pressure ratio. Present result shows recirculation regions are formed both at the upstream and downstream of injector with the characteristic vortex structures. With increasing the jet-to-freestream momentum flux ratio, the vortex structures in the recirculation region are largely developed. It is founded that the highest temperature in the separation region depends on the total temperature in the separation region and furthermore, it is the lower temperature than the total temperature of freestream.</p>

CiNii Article

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開催期間： 2014年10月   記述言語：英語  

開催期間： 2014年01月01日   記述言語：英語  

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.

開催期間： 2014年01月   記述言語：英語  

開催期間： 2013年11月   記述言語：英語  

開催期間： 2013年10月   記述言語：英語  

開催期間： 2013年01月   記述言語：英語  

開催期間： 2012年09月   記述言語：英語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2012年03月   記述言語：日本語  

開催期間： 2011年11月   記述言語：英語  

開催期間： 2011年11月   記述言語：英語  

開催期間： 2011年11月   記述言語：英語  

開催期間： 2011年11月   記述言語：英語  

開催期間： 2010年11月   記述言語：英語  

開催期間： 2010年09月   記述言語：英語  

開催期間： 2010年09月   記述言語：英語  

開催期間： 2010年09月   記述言語：英語  

開催期間： 2010年09月   記述言語：英語  

開催期間： 2010年08月   記述言語：英語  

開催期間： 2010年03月   記述言語：英語  

開催期間： 2010年03月   記述言語：英語  

開催期間： 2010年03月   記述言語：英語  

開催期間： 2010年03月   記述言語：英語  

講演種別：招待講演   開催地：Beijing, China  

講演種別：招待講演   開催地：Tainan, Taiwan  

講演種別：招待講演   開催地：筑波  

講演種別：招待講演   開催地： 釜山，韓国  

講演種別：招待講演  

講演種別：招待講演