Numerical Modelling of Cryogenic Flows Under Near-Vacuum Pressure Conditions

Abstract

A numerical framework for the simulation of two-phase cryogenic flows under a wide range of pressure conditions is presented in this work. Sub-critical injection and near-vacuum ambient pressure conditions were assessed by numerical simulations. Two different computational approaches have been employed, namely a pressure-based solver complemented by a bubble-dynamics model, as well as a density-based solver utilising real-fluid tabulated data to describe the fluid’s thermodynamic properties. The required thermodynamic-data table has been derived using the Helmholtz Equation of State (EoS) and the specific modelling approach can be applied to near-vacuum, sub-critical or even supercritical injection pressure conditions. The geometries of two single-hole injectors have been considered for investigating the flow and spray formation of liquid oxygen (LOx) and liquid Nitrogen (LN2). Both numerical approaches were validated against available experimental data. Overall, the comparison of results to experimentally acquired data demonstrates the suitability of the employed methodologies in describing processes such cryogenic flashing-flow expansion, phase-change and flash-induced spray formation. The density-based tabulated thermodynamics approach in particular, can be considered as a complete numerical framework for treating two-phase cryogenic flows using real-fluid properties, for a wide range of conditions without the need for case-related modifications.