火箭发动机氧相变换热器压力波动分析

Analysis of Pressure Fluctuation of the Oxygen Phase-change Heat Exchanger in Rocket Engine

液体火箭发动机内的螺旋管式氧相变换热器在地面试验时出现进出口压力波动的问题,影响了发动机的正常工作。为了分析压力波动的成因,基于分布参数思想建立了管内流动稳态分析模型。通过局部化的物性参数和传热流阻的准则计算式,求解了螺旋管内工质氧流动的压力、温度、密度、定压比热容等热物性参数的变化。通过比较p-v曲线以及沿程各热力参数变化曲线,初步分析出特定工况下的压力波动与气化压力过低有关。当气化压力接近临界压力,物性的特殊性使气化过程中的热力状态具有不稳定性,导致了压力波动。

Pressure fluctuation occurred in the inlet and outlet of the oxygen helical-coiled heat exchanger in liquid rocket engine during the ground test,which would disturb the normal operation.A steady-state analysis model of the internal oxygen flow is built based on the distributed parameter model(DPM)to explore the mechanism of the pressure fluctuation.The change of thermal parameters including pressure,temperature,density and specific heat along the flow direction is calculated by the use of the local thermal properties and the heat transfer and friction correlations.Though the comparison of the oxygen p-v lines and the thermal properties’change along the flow direction,it can be concluded that the pressure fluctuation is caused by the low vaporization pressure.When vaporization pressure is close to the critical point,thermal properties’specialties make thermodynamic states instable which results in the flow instability and pressure fluctuation.