The Simulation Research Of Cryogenic Engine Hydrogen System Chilldown

LOX/LH₂ rocket engine has a high specific impulse,which plays an irreplaceable role in high orbit satellite launching,deep space exploration and other aerospace fields.When starting up a LOX/LH₂ rocket engine,pre-cooling the hydrogen supply system and controlling the temperature to a reasonable range is necessary.In this paper,we carried out the system modeling and pre-cooling simulation of a domestic LOX/LH₂ rocket engine to provide theoretical support and guidance to optimize the pre-cooling procedure,find a proper end mark of pre-cooling and improve launching capability.The liquid hydrogen is unstable in the membrane boiling state and easily converts to nucleate boiling state.In the mature two-phase flow model,the Mixture model is simulation to nucleate boiling flow,and it is more accurate for calculating unsteady boiling two-phase flow-solid heat transfer.We based on the existing engine emission pre-cooling system,a complete geometric model is established by Creo simulation software,and a steady-state calculation method is used to determine the geometry size of outlet.On this base,the grid independence and the time step independence are verified by the simulation calculation of the pre-cooling process of a test run.The reliability and accuracy of the model are verified by comparing the experimental data.On this basis,the simulation model is used to simulate the continuous emission pre-cooling process during engine start-up,and the relationship between the gas-liquid two-phase distribution of propellant and the temperature distribution of hydrogen system with time is obtained during the pre-cooling process.The result show that:1.The size of pre-cooling flow is correlated to propellant consumption in pre-cooling process;2.The wall temperature of pump shell demonstrate small correlation between the existing criteria of good pre-cooling and the actual pre-cooling situation during pre-cooling process;3.Gravity has little influence on pre-cooling when the flow rate is large so ground test can simulate the real pre-cooling process,and when the flow rate is small,gravity is a main factor.The research on the regeneration process and the pre-cooling process before start-up shows that the main factors of the regeneration process during the stop pre-cooling stage of the hydrogen pump include:1.Heat leakage at the high temperature turbine end;2.Heat balance of local hot spots in the hydrogen pump at the end of pre-cooling.We can effectively lower the degree of rewarming during the stop pre-cooling process by means of Reducing the leakage heat at the turbine end and the overall temperature of the hydrogen pump.The study on pre-start emission pro-cooling shows that the existing emission pre-cooling time order propellant wastes a lot,and it can be effectively reduced by reducing the emission time of propellant.