固体火箭发动机水下超音速射流数值研究

The ignition process of gas jets under water is essentially complex, including multiphase flow and complicated flow structures. The Laval nozzle models with expansion ratios of 3.4 and 14.0 are numerically simulated. The CFD method is applied to study the flow structures and corresponding thrust characteristics of rocket engine and analyze the interaction between the high-speed gas jets and water environment. The results show that the flow structures and thrust characteristics of engine change periodically, and the process can be divided into three stages: necking, bulge and return stroke. The interaction between the water environment and the gas jet is the immediate cause leading to the back pressure oscillation, which also induces the fluctuation of shock waves, momentum thrust and pressure differential thrust. For the nozzles with different expansion ratios, the periodic variation of jets pattern and flow structures for the nozzle with expansion ratio of 14 can be more obviously observed, and the oscillation frequency of back pressure for the nozzle with expansion ratio of 3.4 is higher, accompanied with weak periodic characteristics and more stable thrust characteristics.