Analysis and Modeling of No-Vent Filling Process for Liquid-Hydrogen Tank in Orbital Conditions

Abstract

A four-node model is proposed to investigate the no-vent filling performance of liquid hydrogen (LH2) at microgravity. The no-vent filling method can directly prevent the influence of random gas–liquid distributions at microgravity, making it a good choice for cryogenic propellants to achieve orbital refueling. The typical phase distribution of the centrally located ullage was assumed and, in particular, the correlations for the boiling heat transfer of LH2 at microgravity were corrected in this model. After the accuracy of this model was effectively verified, the effects of different filling conditions, including the initial tank pressure, the initial temperature, and the temperature of the inlet liquid, were studied. The results showed that the initial pressure had a major influence on the initial pressure rise but only a slight influence on the final pressure development. A higher initial temperature would have led to an obvious increase in the tank pressure and an obvious decrease in the final filling level when reaching the upper pressure limit. Reducing the temperature of the inlet liquid has certain effects on the pressure control and the improvement of the final filling level. In conclusion, to achieve a higher filling level under a lower pressure level during the no-vent filling of LH2 at microgravity, sufficient pre-cooling of the filling system is required. Furthermore, appropriate evacuation of the receiver tank before filling and subcooling of the inlet liquid within an acceptable range of costs are both suggested. While the proposed model is less accurate than full-resolution CFD for the detailed evolution of physical fields, it offers much greater computational speed for quick parametric studies of key input conditions.