Numerical Investigation of Flash Evaporation of the Combined Injection of Liquid Oxygen and Gaseous Methane/Hydrogen

In this work a novel Euler-Euler, two-phase, multi-species solver based on OpenFOAM for the simulation of flashing cryogenic jets is developed. The solver is applied to two test cases of a coaxial injection of cryogenic liquid oxygen (LOX) and gaseous methane (CH4) or gaseous hydrogen (H2) at typical conditions for the ignition in space. With the rapid decrease in static pressure, the LOX enters superheated conditions, which cause the liquid to flash evaporate. The homogeneous relaxation model (HRM) in conjunction with the one-fluid method prove to be suitable under these challenging conditions. The simulation domain encompasses both the dome geometry and the convergent part of the nozzle. This enables the use of the experimentally measured static pressure values as boundary conditions instead of the less accurately measured mass flow rates. The results show a good agreement with both experimental schlieren images in the vicinity of the faceplate and a second reference simulation. The shock waves and contraction of the flashing LOX jet are captured with a high degree of accuracy. In order to accurately capture the position of the central Mach disc, it is imperative to take into account the reduction in the speed of sound in the disperse phase.