耦合尾喷管堵盖运动的水下固体火箭发动机点火启动过程特性

To investigate the flow field and working characteristics of the underwater solid rocket motor at the initial stage of ignition, the gas bubble evolution process under the constraint of nozzle closure separation is numerically simulated. Based on the VOF multiphase model and dynamic mesh technique, a numerical model of underwater gas jet with the effect of nozzle closure is established. The transient evolution of gas bubble morphology and the oscillation characteristics of flow field parameters are analyzed. The characteristics and formation mechanism of initial thrust pulsation after ignition at variable depths are revealed. The results show that: at the initial stage of nozzle opening, the pressure difference drives the closure to strongly impact the liquid phase, causing a high pressure zone in the tail wall space and the formation of an initial thrust peak; as the ignition depth increases, the axial growth rate is slower and the length becomes shorter, the gas bubble has neck contraction in advance, and the pulsation characteristics of the flow field parameters and thrust of the motor become stronger; at the initial stage of ignition in deep water, the shock wave near nozzle exit has reciprocating oscillations, and the pressure oscillation in the tail wall space forms multiple fluctuating thrust peaks. It is demonstrated that the unstable motion of shock waves is the leading factor of thrust pulsation.