二维凹面腔内暂冲式激波聚焦机理的实验

针对两级脉冲爆震发动机中第二级凹面腔内激波聚焦起爆能量和周期的研究,设计了二维凹面腔内暂冲式激波聚焦实验系统。通过分析粒子图像测速系统捕捉的照片和动态压力数据,获得了凹面腔内激波聚焦高压区压力特性和多循环流场演化特征。并且开展了A和B两种型面凹面腔的对比实验,进一步分析了多循环激波聚焦的形成机理。结果表明:入射激波第一次在凹面腔底部聚焦后形成的聚焦反射激波在喷口射流边界上发生反射,产生的反射激波再次在凹面腔底部聚焦,形成了第二次激波聚焦,如此往复便形成了周期性的激波聚焦,聚焦频率高达7~10kHz；并且,速度场和射流强度随入射激波碰撞而减弱,在排气过程中又增强,呈现周期性变化。 

Experiment of transient shock wave focusing performance in two-dimensional concave cavity

Two-dimensional transient shock wave focusing experiment system was designed to investigate the shock wave focusing initiation energy of two-stage pulse detonation engine. Dynamic pressure sensors and particle image velocimetry system were adopted to capture the dynamic pressure of the cavity bottom vertex and the velocity vector field during multi-cycle of shock focus. Furthermore, the cavities of type A and B were used in contrast tests and the velocity vector field was analyed in the meantime. It was found that the first focus was caused by incident shock produced by diaphragm rupture. The post-focus reflected wave formed immediately after shock focus reflected at jet boundary of the nozzle exit and generated the re-reflected wave. The re-reflected wave acted a incident shock in the second cycle and contributed to the second shock focus, then periodic shock focus formed. The focus frequency was up to 7-10kHz. In addition, the velocity field and the strength of the jet weakened with the collision of incident shock waves, then enhanced when high-pressure flow was exhausted, forming a cyclical change.