Analysis And Numerical Study On Boil-off Of Cryogenic Propellant On Orbit

The main power of space vehicles comes from cryogenic propellant.For the reason that it has high impulse and energy,it provides propulsion for most space vehicles.Cryogenic propellant has very low saturation temperature,and easily evaporates when heated.Thus it will lead to the decrease of cryogenic propellant.And the lifetime of space vehicles will become short.The research on cryogenic storage underground has been carried on for many years.Due to the high cost of the storage of cryogenic propellant on orbit for space vehicle and the difficulty in stratifying of gas and liquid in microgravity environment and zero-gravity environment,it is difficult to store cryogenic propellant in space.Many factors in space,such as solar radiation,earth albedo,planetary albedo and space particle effect,have impacts on cryogenic tanks.When cryogenic evaporates,the pressure in the tanks will increase,thus pressure control system will become more complex.And what's more the amount of cryogenic decrease.So it is necessary to do research on the influence factors of the boil-off of cryogenic on orbit and the law of evaporation.In this thesis,the model of cryogenic tank is made by Thermal Desktop.By the use of CFD software Sinda/Fluint,the conditions of the space are simulated.The effects of spatial heat environment on cryogenic tanks in space vehicles are modeled.In this thesis,in one orbit period of time,external thermal flux is simulated when different thermal protective materials on cryogenic tank are used.The influence of thermal protective materials on the absorption of heat flux of cryogenic tank is studied.External thermal flux of sun pointing flight attitude and earth pointing flight attitude is simulated.The influence of different flight attitude on the absorption of heat flux of cryogenic tank is studied.In this thesis,phase change in cryogenic tank on orbit is simulated by the use of phase change model of cryogenic propellant and CFD software Fluent.The flow field and evaporation field of the cryogenic tank when spatial heat environment impacts on it are obtained.The purpose of this thesis is to get evaporation rate of cryogenic propellant.Thus it will provide advice for improving storage conditions.