Experimental study on equilibrium height of capillary rise with liquid oxygen in reduced gravity under the influence of thermal leakage

Cryogenic propellants often experience reduced-gravity levels during orbital transfer and deep exploration, which leads to uncertainty in their interface structure and equilibrium height. In addition, unexpected thermal leakage can cause evaporation at the three-phase contact line, further complicating the prediction of the interface location. In this research, a cryogenic testing apparatus based on a magnetic compensation platform was developed to investigate the capillary rise equilibrium height on a plate and in the corner of liquid oxygen (LOX) in reduced gravity. A periscope-like visual system is employed to visualize and record the interface evolution in the magnetic compensation region. It is found that wall overheat leads to a decrease in the steady-state contact angle, which differs from the static contact angle. Based on the experimental results of LOX interface at different wall overheat conditions, the relationship between wall superheat and the steady-state contact angle applicable to cryogenic propellants is established. Due to the imperfect internal corner caused by industrial machining, the equilibrium height could only reach a finite value. The operation pressure has little effect on the equilibrium height. As the wall overheat and gravity level increase, the capillary rise equilibrium height decreases. Moreover, dimensionless correlations are developed to predict the capillary rise equilibrium height of LOX on the plate and in a corner. The present study is of significance for predicting the propellant interface height in reduced gravity conditions to design and construct propellant management devices.