Effect of micro- and elevated gravity condition on the evolution of stratification and self-pressurization in a cryogenic propellant tank

Abstract

An efficient way of handling and storing cryogenic propellant is required for future space exploration. In rocketry applications, propellants are stored at subcooled conditions in foam-insulated tanks. Any kind of heat infiltration may lead to stratification and self-pressurization of the tank. The supply of warm propellant beyond the cavitation limit to a turbo-pump is dangerous and hence additional propellant has to be loaded, which affects the payload capacity. The evolution of stratification during lift-off and accelerated conditions and coast phase will be different from those during normal ambient conditions. During lift-off the gravity value can reach up to 6g and microgravity (lg) conditions at the coast phase. Hence, accurate prediction of the state of propellant at all stage is required for the successful mission planning. A multiphase axis-symmetric CFD model is developed, which can simultaneously account for heat transfer from the ambient and heat exchanges within the fluids during different gravity conditions. The results show that the self-pressurisation in microgravity condition is due to phase change rather than thermal stratification. The flow velocity will be maximum during lift-off and accelerated condition. Hence, greater self-pressurisation happens during the initial period and reduction in pressure rise rate is noticed later, which is due to turbulence of the fluid.

Recent Advances in CFD Simulations of Multiphase Flow Processes with Phase Change

“…First, it is challenging to remove evaporated cryogen under microgravity as the convection induced by buoyancy is constrained on this occasion. Second, compared with natural convection, evaporation is more important for self-pressurization under microgravity. , Third, LH 2 is sensitive to heat invasion and radiation because of its high volatility and low density, which can result in a more pronounced self-pressurization in microgravity. Therefore, the cryogenic propellant tank should be prepressurized before launching to restrain liquid vaporization during the operation period and this prepressurization can also prevent severe depressurization during the accelerating stage.…”

Study of the thermal characteristics of propellant tanks in microgravity and its application to propellant gauging

“…Zhang M et al [37] studied the effect of gravity level on the self-pressurisation process of liquid nitrogen cryogenic fluid. Vishnu S B et al [38] studied the effect of microgravity and high gravity conditions on the stratification and self-pressurisation evolution of cryogenic propellant storage tanks.…”