Simulation of Nozzle Erosion Process in a Solid Propellant Rocket Motor

Abstract

This paper presents an approach to the simulation of erosion within a rocket nozzle from fundamental principles that relies on as little empirical data as possible. A model is developed that accounts for shear and pressure forces, particle impacts, heat transfer and its subsequent diffusion through the nozzle material, and surface chemical kinetics. The model is based on macro-scale dynamical model concepts, which allow the particle impacts to be modeled based on a lattice method and properties of the material. The macro-scale dynamical model is extended by solving the energy equation at each lattice point for thermal effects, applying surface forces to surface site, and applying chemical kinetics to surface sites. The thermal model, chemical model, and surface regression are validated against experiments and other simulations, and they are all found to be accurate in the subgrid scales that are to be modeled. The chemical erosion of a carbon nozzle in an H2O-CO2 environment over a range of pressures and compositions is studied, and high erosion rates are seen for flows with high water content at high pressures. Additionally, preliminary erosion studies are performed on niobium and tungsten-rhenium materials. It is found as expected that the more ductile and lighter niobium is subject to more erosion by particle impacts. Niobium is found to be subjected to significant erosion by particle impacts and thermal effects, whereas erosion of tungsten-rhenium is found to be almost entirely due to thermal effects in a nozzle-like environment. The model has been developed enough that it is ready for full integration into internal rocket flow field solvers.