共查询到16条相似文献,搜索用时 421 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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激波在收缩管内的反射与聚焦会形成高温高压区,点燃可燃混合气并诱导爆轰,因此对爆轰发动机的点火具有重要意义。本文基于二维N-S方程,结合五阶WENO格式,对马赫数为6的正激波在三角形楔面内的反射与聚焦现象进行了数值研究。结果表明,楔面顶角的变化对激波的反射类型以及聚焦均有明显的影响:随着顶角的增加,激波的反射类型从马赫反射向过渡马赫反射和双马赫反射转变,且壁面上的前向射流更加明显;三波点第一次碰撞产生的高温高压区足够满足可燃混合气体的点火条件,且其温度与压力值随顶角的增加而增大;当激波在楔面上发生临界双马赫反射时,温度与压力达到最大;当顶角增加到一定值时,激波在楔面反射转变为常规反射,不会产生激波对碰,因而没有高温高压区。 相似文献
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激波与爆轰波对撞的数值模拟研究 总被引:2,自引:1,他引:1
用二阶精度NND差分格式和改进的二阶段化学反应模型模拟了爆轰波与激波的对撞过程,研究了不同强度入射激波对爆轰过渡区域的影响. 当对撞激波较弱时,透射爆轰波演变主要受流动膨胀作用的影响,可划分为对撞影响区、爆轰恢复区和稳定发展区3个阶段. 在爆轰恢复区和稳定发展区,前导激波压力经历一个过冲、然后向稳定爆轰过渡的过程,表现了爆轰波熄爆和再起爆的物理特征. 当对撞激波较强时,可燃混合气体的高热力学参数导致了更高的化学反应活化程度,形成了弱爆轰向稳定爆轰的直接转变. 相似文献
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采用频散可控的耗散格式(DCD),求解Euler方程和一种改进的二阶段化学反应模型,
对氢氧反向-正向双爆轰驱动段激波管进行了数值模拟. 计算结果表明:当辅驱动段与主驱动
段初始压力比小于临界值时,Taylor波仍会出现,但波扇夹角较单一前向爆轰驱动段小,入
射激波马赫数衰减率变小;当初始压力比等于临界值时,主驱动段中的Taylor波完全被消除,
入射激波马赫数不再衰减. 当初始压力比大于临界值时,在主驱动段中能产生过驱动爆轰波,
不仅Taylor波被完全消除,而且驱动能力较单一前向爆轰驱动段强. 相似文献
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圆球诱发斜爆轰波的数值研究 总被引:2,自引:0,他引:2
斜爆轰发动机是飞行器在高马赫数飞行条件下的一种新型发动机,具有结构简单、成本低和比冲高等优点.但是斜爆轰发动机的来流马赫数范围广,来流条件复杂,为实现斜爆轰波的迅速、可靠引发,采用钝头体来诱发.利用Euler方程和氢氧基元反应模型,对超声速氢气/空气混合气体中圆球诱导的斜爆轰流场进行了数值研究.不同于楔面诱发的斜爆轰波,球体首先会在驻点附近诱发正激波/爆轰波,然后在稀疏波作用下发展为斜激波/爆轰波.模拟结果显示,经过钝头体压缩的预混气体达到自燃温度后,会出现两种流场:当马赫数较低时,由于稀疏波的影响,燃烧熄灭,钝头体下游不会出现燃烧情况;而当马赫数较高时,燃烧阵面能传到下游.分析表明,当钝头体的尺度较小时,驻点附近的能量不足以诱发爆轰波,只会形成明显的燃烧带与激波非耦合结构;当钝头体的尺度较大时,流场中不会出现燃烧带与激波的非耦合现象,且这一特征与马赫数无关.通过调整球体直径,获得了激波和燃烧带部分耦合的燃烧流场结构,这一流场结构在楔面诱发的斜爆轰波中并不存在,说明稀疏波与爆轰波面的相互作用是决定圆球诱发斜爆轰波的关键. 相似文献
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基于带化学反应的二维Euler方程,对圆柱形爆轰波的直接起爆和传播过程进行了二维数值模拟研究,拟分析起爆条件和初始压强对圆柱形爆轰波形成和传播的影响。研究发现,圆柱形爆轰波起爆成功向外传播的过程中,新的三波结构的生成标志着爆轰波进入稳定传播阶段。在起爆能量足够的情况下,起爆半径(曲率)的大小决定着三波结构初始形成时的数目和传播半径,起爆压强对其基本不产生影响;起爆半径大(曲率小)时,三波结构初始形成时的传播半径大、数目多,圆柱形爆轰波进入稳定传播阶段的传播距离长;数值模拟中,初始压强的提高,有助于圆柱形爆轰在较短的传播距离内进入稳定传播阶段。 相似文献
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Abstract. From practical and theoretical standpoints, the initiation of combustion in gaseous media due to the shock waves focusing
process at various reflectors is a subject of much current interest. The complex gas flowfield coupled with chemical kinetics
provides a wide spectrum of possible regimes of combustion, such as fast flames, deflagration, detonation etc. Shock wave
reflection at concave surfaces or wedges causes converging of the flow and produces local zones with extremely high pressures
and temperatures. The present work deals with the initiation of detonation due to shock waves focusing at parabolic and wedge
reflectors. Particular attention has been given to the determination of the critical values of the incident shock wave (ISW)
Mach number, parameters of the combustible mixture, and geometrical sizes of reflector at which different combustion regimes
could be generated.
Received 30 August 1999 / Accepted 23 February 2000 相似文献
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Detonation and deflagration initiation at the focusing of shock waves in combustible gaseous mixture 总被引:12,自引:0,他引:12
B.E. Gelfand S.V. Khomik A.M. Bartenev S.P. Medvedev H. Grönig H. Olivier 《Shock Waves》2000,10(3):197-204
Abstract. Detonation and deflagration initiation under focusing conditions in a lean hydrogen-air mixture was experimentally investigated.
The experiments were carried out in a shock tube equipped with the laser schlieren system and pressure transducers. Two-dimensional
wedges (53° and 90°), semi-cylinder and parabola, were used as the focusing elements. The peculiarities of mild and strong
ignition inside the reflector cavity were visualized. A hydrogen-nitrogen mixture was taken for comparison between reactive
and inert mixture. It was found that mild ignition inside the reflector cavity can lead to detonation initiation outside the
cavity. Schlieren pictures of the process were obtained and the dependence of the distance of detonation initiation on Mach
number of the incident shock wave was established.
Received 30 August 1999 / Accepted 23 February 2000 相似文献
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In this paper, focusing of a toroidal shock wave propagating from an annular shock tube into a cylindrical chamber was investigated
numerically with the dispersion controlled dissipation (DCD) scheme. The first case for an incident Mach number of 1.5 was
conducted and compared with experiments for validation. Then, several cases were calculated for higher incident Mach numbers
varying from 2.0 to 5.0, and complicated flow structures were observed. The numerical study was mainly focused on two aspects:
focusing process and flow structures. The process, including diffraction, focusing, and reflection, is displayed to reveal
the focusing mechanism, and the flow structures at different incident. Mach numbers are used to demonstrate shock reflection
styles and focusing characteristics.
PACS 47.40.Ki; 47.40.Nm; 52.35.Tc 相似文献
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环形激波聚焦流场特性的数值研究 总被引:1,自引:0,他引:1
针对环形激波聚焦过程产生的高温、高压特性,采用间断有限元方法模拟了环形激波在同轴圆柱
形激波管内的聚焦流场特性。计算结果表明,采用间断有限元方法能够有效地捕捉激波聚焦过程形成的二次
激波、涡环、三波交点和球面双马赫反射等主要流动特征。此外,通过改变环形管道内外半径对聚焦流场进行
模拟发现,环形管道外径对中心轴线上聚焦峰值压力的大小和位置影响较小,环形管道内径对中心轴线上聚
焦峰值压力的大小和位置影响较大。计算结果可以为工程应用提供一定的理论指导。 相似文献
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The spherically converging detonation wave was numerically investigated by solving the one-dimensional multi-component Euler
equations in spherical coordinates with a dispersion-controlled dissipative scheme. Finite rate and detailed chemical reaction
models were used and numerical solutions were obtained for both a spherical by converging detonation in a stoichiometric hydrogen-oxygen
mixture and a spherically focusing shock in air. The results showed that the post-shock pressure approximately arises to the
same amplitude in vicinity of the focal point for the two cases, but the post-shock temperature level mainly depends on chemical
reactions and molecular dissociations of a gas mixture. While the chemical reaction heat plays an important role in the early
stage of detonation wave propagation, gas dissociations dramatically affect the post-shock flow states near the focal point.
The maximum pressure and temperature, non-dimensionalized by their initial value, are approximately scaled to the propagation
radius over the initial detonation diameter. The post-shock pressure is proportional to the initial pressure of the detonable
mixture, and the post-shock temperature is also increased with the initial pressure, but in a much lower rate than that of
the post-shock pressure.
Zonglin Jiang is presently a visiting professor at McGill University, Canada. 相似文献