Effect of Initial Liquid Hydrogen Temperature on the Pressure Changes in the Cryogenic Propellant Tank

The cryogenic propellant tank will be in microgravity environment for more than several hundred seconds during the MECO (Main Engine Cut-off) phase. Liquid hydrogen propellant works near its saturation temperature, which can easily cause phase transition due to heat transfer and other effects, thus affecting the pressure change of the tank. The effects of different initial cryogenic propellant temperatures on tank pressure and temperature are studied by establishing a three-dimensional CFD model. The results show that the larger the difference between the temperature of the propellant near the gas-liquid interface and the saturation temperature under the current gas pressure is, the greater the pressure drop rate is. As the gas pressure drops, the overall temperature of the ullage gas decreases, the pressure drop rate also gradually decreases, and the pressure change curve tends to flatten out. 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.