Control Strategy Optimization of Thermodynamic Venting System in Liquid Hydrogen Storage Tank Under Microgravity

Abstract

This study employed a lumped vapor model to investigate the depressurization dynamics during the thermodynamic venting process in a cryogenic liquid hydrogen storage tank under microgravity conditions. The effects of different control strategies-such as flow distribution, circulation flow rate, spray angle, and throttle valve switching time-on the performance of the thermodynamic venting system (TVS) were studied. Building on this foundation, the control strategies are refined across various filling rates and heat loads. The findings indicate that directing the flow towards the upper nozzle proximate to the vapor enhances the depressurization rate and augments the utilization of cooling capacity. The optimal circulation flow rate matches the heat entering the air pillow, and increases with higher heat load and lower filling rate. When the injection angle is 60°, the TVS achieves optimal performance with the fastest depressurization rate and no thermal stratification. The throttle valve opens during the early depressurization stage and closes when the pressure drops to the critical pressure P_cr, resulting in better performance. A lower filling rate and higher heat load lead to an increase in P_cr. This study provides a solid foundation for optimizing TVS control under various conditions, ultimately extending the storage duration of propellants in orbit.