水下爆轰燃气泡形态与激波传播过程研究

Gas Bubble Shape and Shock Wave Propagation Process of Underwater Detonation

关键词:  脉冲爆轰发动机  水下燃气射流  燃气泡  激波  两相流

Key words:  Pulse detonation engine  Underwater gas jet  Gas bubble  Shock wave  Two-phase flow

摘要:

针对脉冲爆轰发动机在水下工作过程中形成的燃气射流问题，搭建了水下爆轰燃气实验系统，研究了第一个爆轰循环中燃气泡发展变化过程。建立了基于气液两相双流体模型的脉冲爆轰发动机水下喷射模型，采用时-空守恒元和求解元方法，模拟了爆轰波与水相互作用形成的激波的传播及衰减过程。研究结果表明：燃气射流冲击水面时，燃气泡形态在膨胀阶段受到水介质的阻滞作用呈现“豌豆”状，其轴向与径向尺寸有不同的发展规律；同时燃气泡内由于气水冲击作用和燃气扩散受限一直保持较高压力；前导激波传播速度远大于燃气泡发展速度，脱离燃气泡后激波压力值迅速衰减至常压量级，且在中心轴线上的衰减最为剧烈，导致其强度指向性发生改变；前导激波在气液交界面处产生反射，回传的反射激波与后续气流形成的拦截激波碰撞在燃气泡内出现回击现象，使管口附近形成较高的压力峰值。

Abstract:

An underwater detonation gas experiment system was established to explore the problem of detonation gas jet formed in the underwater working process of pulse detonation engine （PDE）. The development and changing process of gas bubble in the first detonation cycle of PDE was experimentally investigated. An underwater jet model of PDE based on the gas-liquid two-phase two-fluid model was established and the space-time conservation element and solution element （CE/SE） method was employed to numerically simulate the propagation and attenuation process of shock wave formed by the interaction of detonation wave and water. The results show that the gas bubble expands into the shape of ‘pea’ with different development laws between the axial and radial dimensions as it is blocked by the external water environment when the gas jet hits the water surface. The gas bubble has always maintained high pressure due to the gas-water impact and the restricted gas diffusion meanwhile. The leading shock wave propagates much faster than the gas bubble development， and pressure of leading shock wave quickly decays to the ambient pressure after separating from the gas bubble. Pressure of the leading shock wave attenuates most severely in the axial direction， which results in a change in its intensity directivity. The reflected shock wave formed by reflection of the leading shock wave at the gas-liquid interface colliding with the intercepting shock wave formed by the subsequent airflow results in the return stroke， which causes a high pressure peak near the nozzle.