Numerical Analysis On Dynamic Characteristics Of LOx/LCH4 Space Propulsion System For Attitude And Orbit Control

LOX/LCH4 is considered as the best propellant combination in the field of space propulsion in the future.In this thesis,LOx/LCH4 space propulsion system for attitude and orbit control is taken as the object of study.The design scheme of the system is carried out.According to the theory of modularization modeling and simulation,The whole system simulation model is established,and the dynamic characteristics of the system are simulated.In addition,the dynamics model of the cryogenic propellant flow in the pipeline is established and the filling process is simulated.The influence of the gas-liquid two-phase flow produced by heat tranfer behind the electromagnetic valve on the dynamic characteristics of the system is also considered in this thesis.Firstly,the scheme of LOX/LCH4 space propulsion System is studied.The management of cryogenic propellant is briefly introduced.The schematic diagram of the system is given,which provides the research object for the simulation of dynamic characteristics.Secondly,the distribution characteristics of the cryogenic propellant flowing through the room temperature piping are described briefly.The dynamics model of the flow and heat transfer of the cryogenic propellant in the pipeline is established.The simulation of the liquid oxygen single pipe filling process is carried out by the lumped parameter method.Then a preliminary analysis on the process is taken.Thirdly,a general simulation model of LOX/LCH4 space propulsion System was built on AMESim.The transient response characteristics of the system were analyzed.The influence of valve sequence,injection pressure drop and combustion time delay on the dynamic characteristics was analyzed.The response characteristics of the system under disturbance are analyzed,and the anti-interference ability of the system is also evaluated.Finally,considering the existence of heat transfer behind the solenoid valve,the gas-liquid two-phase flow will appear during the engine start-up process.In this thesis,through simplifying the structure bebind the solenoid valve,the simulation of the starting process is carried out.The results show that the two-phase flow hampers the process of pressure build-up.Some methods to weaken the delay effect are present.