Studying On The Mechanism Of Cryogenic Propellant Tank Pressurization Under Micro Gravity Condition

During the launching process under microgravity environment,the ullage pressure of liquid propellant tank will decrease.In this case,pressurization system is applied for maintaining appropriate ullage pressure,which is necessary to reboot the engine and accomplish the launch task.Pressurization of liquid propellant tank is complicated,multiple reasons effect ullage pressure.Studying the mechanism of cryogenic propellant pressure is crucial problem.More and more numerical simulation methods are used in the overall design of carrier rocket power system.Through numerical simulation,not only can the design parameters of the dynamic system be optimized,but also can be cross-checked and verified with theoretical design and experimental measurement,so as to improve the reliability of the system.However,in the process of improvement and optimization of launch vehicles or the design of new launch vehicles,a variety of complex flow and heat transfer problems are often encountered.The numerical calculation model established directly is too complex,and many different materials and structures are coupled,which appear in the problems to be solved at the same time.Problems such as too long computation time(several years),difficulty in convergence and difficulty in program debugging often occur.In this paper,a fluid mechanics calculation model based on a model tank is applied to research,the initial sloshing amplitude,the initial ullage temperature,initial temperature of the liquid propellant temperature,three factors for tank pressure change and the influence of the temperature stratification,etc.For the future of the propellant tank pressure change research,this paper provides basic results of numerical calculation.The results show that the larger the initial sloshing amplitude,the greater the initial pressure drop rate.For the influence of the initial ullage temperature,the overall average temperature of ullage and the temperature stratification should be considered.The overall temperature of ullage affects the current pressure of the air pillow.The lower the overall temperature is,the smaller the current ullage pressure is.Compared with the initial ullage temperature,the liquid temperature has a greater influence on the initial drop rate of the pressure in the tank,and also on the overall equilibrium pressure of the tank.When the initial liquid propellant temperature is lower than the equilibrium temperature,the higher the initial liquid propellant temperature is,the higher the equilibrium pressure is.