共查询到19条相似文献,搜索用时 125 毫秒
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可燃气体中激波聚焦的点火特性 总被引:4,自引:0,他引:4
数值模拟了二维平面激波从抛物面上反射在可燃气体中聚焦的过程,研究了形
成爆轰波的点火特性. 对理想化学当量比氢气/空气混合气体,在初始压强20kPa的条件下,
马赫数2.6-2.8的激波聚焦能产生两个点火区:第1个点火区是反射激波会聚引起的,第
2个点火区是由入射激波在抛物面上发生马赫反射引起的. 这种条件下流场中会出现爆燃转
爆轰,起爆点分别分布在管道壁面、抛物反射面和第2点火区附近. 起爆机理分别为激波管
道壁面反射、点火诱导激波的抛物面反射和点火诱导的激波与第2点火区产生的爆燃波的相
互作用. 不同的点火和起爆过程导致了不同的流场波系结构,同时影响了爆轰波传播的波动
力学过程. 相似文献
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采用一种两步化学反应模型对胞格爆轰波的楔面马赫反射过程进行了数值研究,从而澄清和解释胞格不稳定性对马赫反射发展模式和自相似性的影响。考虑到反应欧拉方程源项的刚性问题,本文采用附加RungeKutta方法耦合非刚性对流项和刚性反应源项,对流项的离散采用五阶精度的WENO格式。计算结果表明,对于稳定胞格爆轰波而言,其马赫反射过程本质上与ZND爆轰波的马赫反射是一致的,整体上不存在自相似性,胞格不稳定性只是造成了三波点轨迹线局部小振幅的波动。在楔面顶点附近,由于马赫杆是强过驱的,爆轰波的马赫反射过程是自相似的。在远场,爆轰波马赫反射的三波点轨迹线渐近的趋向于一条直线,说明重新获得了自相似性。对于不稳定的爆轰波,由于自身的不稳定性可以与马赫反射的强度相匹配,定义其三波点的轨迹是困难的,进行自相似性分析没有意义。 相似文献
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用环形激波聚焦实现爆轰波直接起爆的数值模拟 总被引:5,自引:3,他引:5
利用基元反应模型和有限体积法对环形激波在可燃气体中聚焦实现爆轰波直接起爆进行了数值模拟。研究结果表明,标准状态下的氢气-空气混合气体在马赫数为3.1以上的环形激波聚焦产生的高温高压区作用下会诱发可燃气体的直接起爆形成爆轰波,爆轰波与激波和接触间断相互作用产生了复杂的波系结构;爆轰波爆点位置在对称轴上并不是固定的点,而是随着初始激波马赫数的变化而发生移动;可燃气体初始温度和压力对起爆临界马赫数都有影响,但是初始温度的影响大得多。 相似文献
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分析了滑移线延长线与楔面交点附近的流动特点,研究了准定常强激波反射中马赫杆的变形,建立了马赫杆突出变形消失的过渡准则,并用激波极曲线方法进行了求解。对马赫杆的变形过程进行了描述,研究了比热比、马赫数的变化对马赫杆突出变形消失条件的影响,并对突出变形消失区域与终点双马赫反射区域进行了比较。结果表明:马赫杆突出变形的消失是低比热比介质中出现的一种激波反射现象。马赫杆突出变形的消失,导致出现一种新的无射流、直马赫杆的双马赫反射结构。 相似文献
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气相爆轰波在收缩管道中的传播 总被引:3,自引:0,他引:3
详细介绍了对气相爆轰波沿收缩管道传播时发生Mach反射的系统研究。管道中安装了不同楔角的楔块,采用了多种气体组分按不同的初压分组进行实验。在烟薰玻璃片上记录到了爆轰波Mach反射的三波点迹线,其两侧胞格尺寸和密度的变化清晰可见。推算了爆轰波从Mach反射向规则反射转变的临界角。压力传感器记录了Mach反射时楔面上压力和速度的变化。上述参数与空气激波Mach反射作了比较。编制了爆轰波Mach反射计算程序,检验了CCW理论对于爆轰波传播的可用程度,理论值和实验值在楔角不大于30时相当吻合。 相似文献
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研究了甲烷-空气混合物爆轰波在二维突扩通道中传播的各种复杂行为。结果表明:爆轰波在进入突扩通道的初始阶段有局部向爆燃转变的现象;爆炸波在壁面发生马赫反射形成的高温高压区域将直接驱动自持爆轰波的重新形成。 相似文献
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R. S. Srivastava 《Shock Waves》2009,19(4):291-295
In this article, the interaction of a normal shock with a yawed wedge moving at supersonic speed has been considered. The
vorticity distribution of a particle over the diffracted shock wave for various combinations of yawed angles, Mach number
of the shock wave and Mach number of the moving wedge have been obtained. Further triple point angle χ in Mach reflection
has been calculated for the various parameters.
相似文献
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When a weak shock wave reflects from wedges its reflection pattern does not appear to be a simple Mach reflection. This reflection pattern is known to be von Neumann Mach reflection in which a Mach stem can not necessarily be straight. In this paper the local change of the Mach stem curvature was experimentally and numerically investigated. A distinct triple point, at which the curvature becomes infinite as appears in a simple Mach reflection, was not observed but the Mach stem curvature became a maximum between foot of the Mach stem and a point, P1, at which an incident shock met with a reflected shock. Maximum curvature point P2 and P1 do not coincide for small wedge angles and tend to merge over a certain wedge angle. Experimental results agreed with numerical results. The trajectory angle of P2 was found to be expressed well by Whitham's shock-shock angle.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
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气相爆轰波在障碍物上Mach反射的实验验证 总被引:3,自引:0,他引:3
本文公布了气相爆轰波沿收缩管道传播时发生Mach反射的实验证据。在爆轰波通过的管道中安装不同楔角的楔块,形成管道的收缩。爆轰波在通过楔块时会发生Mach反射。利用烟熏玻璃片记录到了爆轰波Mach反射时形成的三波点迹线及其两侧胞格尺寸和密度的变化。据我们掌握的资料,这是首次用胞格结构变化的记录证实,气相爆轰波与无化学反应的空气中的冲击波一样,在一定的入射条件下会发生Mach反射。这一实验结果可使我们更深入了解爆轰波的本质,也为数值模拟气相爆轰波在障碍物上Mach反射现象提供了可对比的依据。 相似文献
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In the Mach reflection of plane shock on a concave double wedge, after two triple points collide with each other, the wave pattern is usually complicated. In this paper, firstly, a shock dynamic approach is used for studying this problem. In this approach, the method of shock-shock polar is used for better understanding the pattern of disturbance propagation. A downward-traveling shock-shock disturbance on the Mach stem is predicted theoretically. Secondly, based on the idea of shock dynamic approach, a gas dynamic model is built for studying the same problem. A similar result is obtained and the formation of the downward-traveling triple point is analyzed. This downward-traveling disturbance propagates and reflects between the upward-traveling shock-shock locus and the wall surface, causing the Mach number of Mach stem to increase and making the wave configuration approach to the one in the Mach reflection on a single wedge.Received: 19 April 2004, Accepted: 2 December 2004, Published online: 16 March 2005[/PUBLISHED]Correspondence to: P. Xie, Z.Y. Han 相似文献
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Numerical simulations have been performed to investigate the stability of shock wave reflection in supersonic steady flow.
Wall deflection control has been applied just downstream of the reflection point in the regular reflection configuration.
The results provide the magnitude of the disturbance required to cause transition from one configuration to the other throughout
the range of incident shock angle. An argument focusing on the subsonic region generated behind the Mach stem in the Mach
reflection configuration explains the mechanism of the transition. Numerical results show that both regular and Mach reflections
are possible in the dual-solution domain, and also indicate the presence of the hysteresis effect. The transition processes
and the stability of the possible states are shown to be described consistently by an analogy based on the potential energy
of a particle on a surface. The necessity of more sophisticated experimental investigations is emphasized to verify the argument
about the stability of shock reflections and proposed analogy.
Received 17 March 1997 / Accepted 26 February 1998 相似文献
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The pattern of shock wave reflection over a wedge is, in general, either a regular reflection or a Mach reflection, depending
on wedge angles, shock wave Mach numbers, and specific heat ratios of gases. However, regular and Mach reflections can coexist,
in particular, over a three-dimensional wedge surface, whose inclination angles locally vary normal to the direction of shock
propagation. This paper reports a result of diffuse double exposure holographic interferometric observations of shock wave
reflections over a skewed wedge surface placed in a 100 × 180 mm shock tube. The wedge consists of a straight generating line
whose local inclination angle varies continuously from 30° to 60°. Painting its surface with fluorescent spray paint and irradiating
its surface with a collimated object beam at a time interval of a few microseconds, we succeeded in visualizing three-dimensional
shock reflection over the skewed wedge surface. Experiments were performed at shock Mach numbers, 1.55, 2.02, and 2.53 in
air. From reconstructed holographic images, we estimated critical transition angles at these shock wave Mach numbers and found
that these were very close to those over straight wedges. This is attributable to the flow three-dimensionality.
相似文献
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In this paper, we present an analytical solution for the flow field of single weak Mach reflection caused by an advancing
plane shock wave over a simple wedge surface. We developed an improvement of Lighthill's linearized theory for the correction
due to nonlinearity of the flow field through a singular perturbation. The expressions obtained, including the one for the
triple point path, compared favorably with existing experimental, computational, and theoretical results.
PACS 01.50.Kw; 47.15.Pn
Communicated by K. Takayama 相似文献
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B. W. Skews 《Shock Waves》1994,4(3):145-154
A study to determine the general gas dynamic behaviour associated with the impact of a shock wave on a porous wedge has been undertaken. A number of interesting features are noted. The pattern of wave reflection is shown to be significantly affected by the inflow of gas into the wedge. This has the effect of reducing the triple point trajectory angle for cases of Mach reflection and for strongly reducing the reflection angle in regular reflection. The permeability of the wedge has a significant effect on the strength of the reflected wave and in some cases this wave can be attenuated to the extent that it is almost eradicated. Pressure measurements taken under the wedge are characterized by oscillations which are of similar shape, for a given wedge, over a range of shock wave Mach numbers. It is shown that the wave transmitted into the wedge is attenuated to varying degrees depending on the material properties, and that for weak incident waves the mean propagation velocity can be less than the sound speed in the pore fluid. Photographs taken using a specially constructed wedge which allows the transmitted wave to be visualised, show that the transmitted wave is nearly plane.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
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Abstract. In this paper, we consider the phenomenon of unsteady Mach reflection generated by a plane shock wave advancing over a straight
wedge surface, with particular attention to the deviation of the flow field from the self-similar nature. We examine the observed
change in angle between incident and reflected shocks, which is in contrast to the fact that the angle should remain constant
with time in a self-similar flow. The effect of the boundary layer behind the advancing shock wave over the surface of the
wedge is considered to cause this, and boundary layer theory is utilized to estimate the thickness of the layer. It is found
that the thickness increases as to the time t compared with t by the overall expansion in the self-similar flow. Assuming that the thicker boundary layer is effectively equivalent to
a change in wedge angle, the effect of the boundary layer on the flow field should be less in later stages with larger t values in accordance with the observation above.
Received 6 March 2000 / Accepted 23 April 2001 相似文献