Vaporization of liquid oxygen (LOX) droplets in supercritical hydrogen environments

Vaporization of liquid oxygen (LOX) droplets in hydrogen over a wide range of pressure (5-250 atm) has been studied by means of a comprehensive theoretical analysis. The model accommodates complete sets of conservation equations for both gas and liquid phases, and accounts for variable properties, thermodynamic non-idealities, and a full treatment of vapor-liquid phase equilibrium at the droplet surface. The governing equations and associated interfacial boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The scheme is capable of treating the entire history of a vaporizing LOX droplet, from thermodynamic phase transition through critical mixing point. Various distinct high-pressure effects on droplet behavior were investigated in depth. In particular, a parametric study of droplet lifetime as a function of ambient pressure, temperature, and initial droplet diameter has been conducted. The droplet lifetime exhibits a strong pressure dependence and can be correlated well with the square of the initial diameter.;An examination of ice/water layers on the LOX droplet surface has been made. This analysis is based on the balance of thermophoretic and viscous forces by adding water vapor to the current 1-D vaporization model, and shows that ice/water layers form in the vicinity of the LOX droplet. The blowing effect caused by LOX droplet gasification tends to move the ice/water particles away from the surface in the direction of the flow.