Numerical Simulation Of Engine Jet Diversion Flow Field Under Vacuum Environment

The surface launching of the spacecraft on the surface of the celestial body is a key part of the flight process.The vibration induced by the impact of the engine plume on the launching platform and the combined force and thermal effects of the anti-jet flow on the spacecraft will form a disturbing load on the surface of the spacecraft.It affects the accuracy and attitude of the launch,and may even lead to the failure of the task.Therefore,it is necessary to install a suitable flow guiding device on the launching platform to smoothly drain the plume and minimize the disturbance to the launching platform.In this study,by understanding the research status of vacuum plume flow at home and abroad,combining with the theory of molecular aerodynamics and rarefied gas dynamics,and by using a numerical method of DSMC method for rarefied gas flow field,we have completed the numerical modeling and simulation of the jet diversion problem of spacecraft engine in vacuum environment,and accomplished different kinds of simulation and completed the simulation calculation and working condition analysis of different diversion structures.The main contents are as follows:(1)By using DSMC method,the numerical solution of the jet flow field of the engine with two kinds of working substances,nitrogen and water vapor,is completed,and the difference of the flow field under the two working substances is compared and analyzed.The distribution law of the plume diversion flow field and the gas physical parameters data under the vacuum environment are obtained preliminarily.(2)Aiming at three diversion schemes,that is to say flat plate diversion,inclined plate diversion and conical diversion,the jet flow field of engine during launch is calculated,and the distributions of diversion flow field parameters such as pressure,temperature and Mach number are obtained.The results are compared with those of free flow field.It is concluded that the conical diversion structure has the best effect.(3)Aiming at the different distances between nozzle and diversion platform during takeoff,by changing the distance between nozzle outlet and diversion structure,the pressure,temperature,Mach number and other related parameters of the vacuum plume flow field near the nozzle are analyzed and calculated under different distances.The impact of distance between nozzle outlet and diversion plate on launch platform of spacecraft is analyzed.(4)According to the numerical calculation of different conical diversion structures,the flow field distribution law under different structures is compared and analyzed,and the influence law of diversion schemes on spacecraft is analyzed and compared.(5)The numerical simulation was carried out for different outlet pressure and velocity parameters of the engine nozzle,and the flow field rules were analyzed and compared respectively.The numerical simulation of engine jet diversion flow field in vacuum environment based on DSMC method provides a theoretical basis for the design of engine diversion structure.