Abstract: The floating rocket mine experiences a large change of environment pressure during operation. In order to simulate the working process of the underwater rocket engines, utilizing the VOF multiphase model, an axisymmetric model describing gas jet in different working states (under-expansion, full-expansion, over-expansion) of underwater engine was established. By simulating the working states with 0m/s and 50m/s, the evolution of the gas jet and unsteady flow characteristics under different working conditions were studied. With velocity 0m/s, the positon of neck shrinkage is far away from the nozzle, and the pulsation of mass flow rate and pressure is not obvious in under-expansion condition. In addition, under full-expansion and over-expansion conditionsmass flow rate and pressure is not obvious in under-expansion condition. In addition, under full-expansion and over-expansion conditions, the positon of neck shrinkage is closer to the nozzle. The maximum pressure amplitudes at nozzle outlet are 5.5MPa, 7MPa, respectively. Correspondingly, oscillation amplitude of mass flow rate is 5.2%, 32.8%. With upstream velocity 50m/s, the positon of neck shrinkage, bulge and back-attack is far away from the nozzle. The maximum pressure amplitude at nozzle outlet under full-expansion is 2MPa, and the pulsation of mass flow rate disappears. The maximum pressure amplitude at nozzle outlet under over-expansion condition is 6.1MPa, correspondingly, and the oscillation amplitude of mass flow rate is 30.4%.

Key words: Underwater solid rocket motor;Submerged gas jet;Pressure oscillation;Multiphase flow;Back-attack and bulge

摘要： 上浮水雷在工作过程中环境压力大幅度变化，针对上浮水雷火箭发动机具有三种不同工作状态（欠膨胀、完全膨胀、过膨胀）的特点，采用VOF两相流模型，建立了水下火箭发动机在不同工作状态喷射流发展的轴对称计算模型，分别在来流速度0m/s和50m/s两种工况下，研究了水下发动机在不同工作状态时喷射流发展规律及流场脉动特性。结果显示，在静水条件下，欠膨胀工况时颈缩发生位置距喷管出口较远，流场压力和喉部流量没有发生脉动现象，其它工况时颈缩发生位置距喷管出口较近，完全膨胀工况和过膨胀工况喷管出口最大压力振幅分别为5.5MPa，7MPa；喷管喉部流量振动幅度约为5.2%，32.8%；在有流速条件下，三种工作状态发生颈缩、胀鼓和回击现象的位置距离喷管出口较远，完全膨胀喷管出口最大压力振幅为2MPa，喷管喉部流量未发生脉动特性，过膨胀工况喷管出口最大压力振幅6.1MPa，喉部流量振动幅度30.4%。

关键词: 水下固体火箭发动机;水下燃气射流;压力脉动;多相流;回击与胀鼓