A Study of Reacting Flow Models for Modeling an RCS Thruster in Space Environments

With the advancement of space travel through the Artemis mission and the build-up of the Lunar Gateway, firing of Reaction Control System (RCS) thrusters in space presents several detrimental mechanisms. One effect, cratering and erosion of surrounding bodies, is a result of unburnt fuel particles from incomplete combustion and freezing of flows. This work aims to improve models relevant to rocket nozzles' exhaust expelled into space. To provide a comprehensive flow model for RCS firings in space, a coupling of computational fluid dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) is utilized, transitioning between continuum to rarefied flow. Prior work developed a non-reacting CFD model of an RCS thruster to analyze particle transport using Lagrangian tracers; such provided the parameters necessary for CFD-DSMC coupling. This study investigates the influence of combustion modeling on particle transport from continuum to rarefied by comparing a non-reacting flow simulation to simulations with differing turbulence combustion models. Use of eddy break-up (EBU) and eddy dissipation concept (EDC) models available in STAR-CCM+ are evaluated through relationships of outlet parameters such as pressure, velocity, temperature, and particle density.