中国科学院力学研究所高温气体动力学国家重点实验室;

由于激波和燃烧的耦合作用,气相爆轰波的波面后方会出现横向运动的激波,从而形成胞格爆轰波结构。对于超声速气流中的斜爆轰波,其胞格结构比正爆轰波更加复杂,研究者对此还缺乏深入的认识。采用无粘Euler方程和单步化学反应模型对斜爆轰波进行了数值模拟,重点研究了活化能和诱导斜爆轰波楔面角度对于波面胞格结构的影响。模拟发现存在两种斜爆轰结构,一种的特点是只存在单向横波,另一种是存在双向的横波。其中在双向横波的结构后方,首次在斜爆轰结构中发现了波后未反应气团的存在。利用统计方法对斜爆轰中横波的产生过程进行分析,结果表明两种结构的产生过程受到不同因素的影响,为斜爆轰波结构的预测提供了依据

Numerical Investigation of Toroidal Shock Wave Focusing

In this paper,focusing of a toroidal shock wave propagating from a shock tube of an- nular cross-section into a cylindrical chamber was investigated numerically with the dispersion- controlled scheme. For CFD validation, the numerical code was rst applied to calculate both viscous and inviscid ows at a low Mach number of 1.5, which was compared with the experi- ment results and got better consistency. Then the validated code was used to calculate several cases for high Mach numbers. From the result, several major factors that in uent the ow, such as the Mach number and the viscosity, were analyzed detailedly and along with the high Mach number some unusual ow structure was observed and explained theoreticall

Instability Criterion of One-Dimensional Detonation Wave with Three-Step Chain Branching Reaction Model

One-dimensional detonation waves are simulated with the three-step chain branching reaction model, and the instability criterion is studied. The ratio of the induction zone length and the reaction zone length may be used to decide the instability, and the detonation becomes unstable with the high ratio. However, the ratio is not invariable with different heat release values. The critical ratio, corresponding to the transition from the stable detonation to the unstable detonation, has a negative correlation with the heat release. An empirical relation of the Chapman-Jouguet Mach number and the length ratio is proposed as the instability criterion

Numerical investigation of flow structures resulting from the interaction between an oblique detonation wave and an upper expansion corner

Wedge-induced oblique detonation waves (ODWs) have been studied widely, but their interactions with complicated geometries have not been fully addressed. In this study, we investigate ODW interaction with a deflected upper corner due to confinement change upstream of the ODW. Numerical simulations are conducted using the reactive Euler equations with a two-step induction-reaction kinetic model. Two ODWs without the upper wall deflection are first simulated to resolve the basic structures with inflow Mach numbers M-0 = 6 and 7. Thereafter, we introduce a deflected upper confinement, resulting in a new wave configuration. This wave is characterized by a post-turning, triangular recirculation zone coupled with a gaseous wedge connecting the deflection point and ODW surface. A parametric study is performed to analyse the effects of the deflection location, deflection angle and activation energy of the heat release reaction. The results reveal that the wave configuration is due to the evolution of ODW decoupling in an expanded supersonic flow. We further study the surface stability and structural unsteadiness arising for M-0 = 6. Upstream-travelling transverse waves are observed for the first time, and effects of different parameters on the surface instability are analysed via fast Fourier transforms. Two destabilizing mechanisms of ODW structures are proposed, one from the post-surface thermal choking and the other from the enhanced surface instability

Numerical study of oblique detonation initiations with chain-branching kinetics

Oblique detonations induced by semi-infinite wedge are simulated by solving Euler equations with chain branching kinetics. Numerical results show the initiation can be triggered by either the abrupt transition or smooth transition, dependent on incident Ma Minand wedge angle 胃, and then their effects on the oblique detonation angle 尾 and initiation length Liniare analyzed. When 胃 increases, Linidecreases monotonically but 尾 has a minimum value, corresponding to 胃 = 29掳 in this study. When Min decreases, both Liniand 尾 increases monotonically until Mindecreases below certain critical value, Min= 9.2 in this study. Then low inflow Ma effects generate the maximum Lini, with the complex of ODW (oblique detonation wave), SODW (secondary oblique detonation wave) and SIDW (self-ignition deflagration wave). The transient process is observed, demonstrating the structure can self-adjust to find a proper position. The wave structure suggests two wave/heat release process determining the detonation initiation. In the cases with high Minfeatured by SIDW, the oblique-shock induced self-ignition dominates, and Liniincreases when Mindecreases. In the cases with low Minfeatured by SODW, the interaction of ODW and SODW dominates, and Linidecreases when Min decreases. 漏 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.</p

Numerical study of inflow equivalence ratio inhomogeneity on oblique detonation formation in hydrogen-air mixtures

In this study, numerical simulations using Euler equations with detailed chemistry are performed to investigate the effect of fuel-air composition inhomogeneity on the oblique detonation wave (ODW) initiation in hydrogen-air mixtures. This study aims for a better understanding of oblique detonation wave engine performance under practical operating conditions, among those is the inhomogeneous mixing of fuel and air giving rise to a variation of the equivalence ratio (ER) in the incoming combustible flow. This work focuses primarily on how a variable equivalence ratio in the inflow mixture affects both the formation and characteristic parameters of the oblique detonation wave. In this regard, the present simulation imposes initially a lateral linear distribution of the mixture equivalence ratio within the initiation region. The variation is either from fuel-lean or fuel-rich to the uniform stoichiometric mixture condition above the oblique shock wave. The obtained numerical results illustrate that the reaction surface is distorted in the cases of low mixture equivalence ratio. The so-called &quot;V-shaped&quot; flame is observed but differed from previous results that it is not coupled with any compression or shock wave. Analyzing the temperature and species density evolution also shows that the fuel-lean and fuel-rich inhomogeneity have different effects on the combustion features in the initiation region behind the oblique shock wave. Two characteristic quantities, namely the initiation length and the ODW surface position, are defined to describe quantitatively the effects of mixture equivalence ratio inhomogeneity. The results show that the initiation length is mainly determined by the mixture equivalence ratio in the initiation region. Additional computations are performed by reversing ER distribution, i.e., with the linear variation above the initiation region of uniform stoichiometric condition and results also demonstrate that the ODW position is effectively determined by the ER variation before the ODW, which has in turn only negligible effect on the initiation length. (C) 2017 Elsevier Masson SAS. All rights reserved.</p

Gasdynamic Characteristics of Toroidal Shock and Detonation Wave Converging

The modified CCW relation is applied to analyzing the shock, detonation wave converging and the role of chemical reactions in the process. Results indicate that the shock wave is strengthened faster than the detonation wave in the converging at the same initial Mach number. Euler equations implemented with a detailed chemical reaction model are solved to simulate toroidal shock and detonation wave converging. Gasdynamic characteristics of the converging are investigated, including wave interaction patterns, observable discrepancies and physical phenomena behind them. By comparing wave diffractions, converging processes and pressure evolutions in the focusing area, the different effects of chemical reactions on diffracting and converging processes are discussed and the analytic conclusion is demonstrated through the observation of numerical simulations

斜爆轰流动燃烧现象及其机理

斜爆轰是高速可燃气体中激波与释热紧密耦合形成的流动现象，在高超声速推进中有潜在的工程应用价值。第1章介绍爆轰的**理论和研究前沿，以及几个重要工程应用，从气相爆轰视角下引入斜爆轰这一*特的研究方向。第2章和第3章分别讲述起爆区和波面特征的研究成果，从基础研究角度揭示斜爆轰及其相关的复杂流动结构。第4章和第5章分别讲述来流扰动和受限空间对斜爆轰流动与燃烧的影响，源于工程研制遇到的实际问题，具有鲜明的应用指向。第6章和第7章从理论、数值和实验角度，介绍常用的研究方法，同时介绍了一些重要结果。第8章从高超声速推进工程应用的角度进行探讨，分析斜爆轰在应用中面临的主要问题。 [1]</p

Research on some fundamental problems of the universal framework for regular gaseous detonation initiation and propagation

本文综并分析了气规则胞格爆轰在起爆与传播方面研究进展,合高温气体动力学重实验室在爆轰物理方面研究工作,进一步研究了气规则胞格爆轰起爆几个关键础问.这些础问由一个制:非性传播/化学反应过程互作用制;两个本过程:热起爆和化学反应带过程;三个关键物理状态:平衡传播状态、临界起爆状态和稳定胞格尺度等六个关键要组成,是统一框架主要本元.通过六个型物理算例,本文研究了这些关键物理要内在制、表现特征及其客观存在性.应用气规则爆轰起爆与传播统一框架,我们成功地释了目前已有经爆轰理论、应用CFD技获多维爆轰计算和实验研究观察到胞格爆轰图像合理性及其依据关键物理要