In order to predict the pressure variation and investigate the interrelation among the physical processes in cryogenic propellant tanks during ground parking

a 2-D axial symmetry volume of fluid (VOF) computational fluid dynamic (CFD) model was established

including a liquid propellant phase and a mixture gas phase. The propellant phase change model was cited based on the assumption of thermodynamic equilibrium. The difference between the simulated pressure rise rate and the test data of a test liquid hydrogen tank was 9.1%. The simulation results of the pressurized stage of liquid hydrogen tank and liquid oxygen tank during ground parking indicate that the heating on the ullage by the heat leakage from the inner surface is the key factor of the pressure rise in the liquid hydrogen tank

and the liquid hydrogen vaporization has comparatively less influence. However

the pressure in the liquid oxygen tank varies as the liquid oxygen phase transition changes at the beginning of the propellant pressurized parking stage. The pressure variations in these two tanks are both under the influence of the propellant phase change affected by the different change trends of the propellant convection induced by the heat transfer between the gas and the liquid.