自激振荡脉冲喷嘴空化效应及其射流形态的数值分析

摘要

Based on the cavitation effects of the self-excited oscillation pulsed nozzles and multiphase flow model,a cavitation model of the self-excited oscillation pulsed jets was established.The axisymmetric physical model of the chamber was built according to the self-excited oscillation chamber structures and its geometric parameters.The breakup of cavitation bubbles,two-phase distributions in the chambers,turbulent kinetic energy distributions and velocity distributions in an oscillation period of 100 ms were obtained by numerical calculations.The results show that..in 1.02-2.37 ms,the radii of cavitation bubbles decrease rapidly and the bubbles begin to do radial motions to form the accelerating jet on the bubbles surface.In 2.69-4.67 ms,the bubbles start to crush when the pressures of cavitation bubble surfaces reach the limit breaking value.In the beginning of 25 ms,the strong turbulent kinetic energy is formed at the contact interface between the main jet and air,and the center vortex area in self-excited oscillation chamber gradually grows up.Continuous jet in the outflow field is cut into the multiple jet and the jet velocity reaches a stable value about 30-40 m/s near the axis of injection.In 40-90 ms,the central cavitation airbag in the chamber has been formed and begins to block the movements of main jet,and the large cavitation area appears in the nozzle's outlet channel and the maximum turbulent kinetic energy is concentrated in the downstream of the lower nozzle exits.In the later period of oscillation,the velocity of main jet tends to be stable and the diffusion effects are weakened as the main jet interacts with the air and the penetration distances of the jet increase.%基于自激振荡脉冲喷嘴空化效应和多相流模型,建立了自激振荡脉冲射流空化模型.依据自激振荡腔室结构及其几何参数建立了腔室轴对称物理模型,计算得到了振荡周期100 ms内自激振荡脉冲射流的空化泡破碎、腔室内两相分布、湍动能分布和速度分布等结果.研究表明:在1.02～2.37 ms时,空化泡半径减小,气泡开始径向运动形成泡面加速射流;在2.69～4.67 ms时,空化泡面压力达到极限破碎值时气泡开始破碎;在自激振荡周期前25 ms,主射流与空气接触边界面形成较强湍动能,自激振荡腔室中心漩涡区逐渐变大,外流场连续射流被割断成多股状射流,射流在喷射轴线附近速度达到并稳定在30～40m/s;在振荡周期的40～90ms,腔室内中心空化气囊形成并开始阻挡主射流运动,喷嘴出口流道出现大面积空化区域,湍动能最大区域集中在下喷嘴出口下游;在振荡后期,随着主射流与空气相互作用及射流贯穿距离增加,主射流速度逐渐趋于稳定且扩散作用减弱.