Numerical simulation of low-melting temperature solid fuel regression in hybrid rocket engines

Abstract

A computational model of low-melting solid fuel regression in the combustion chamber of hybrid rocket engine is presented. The numerical model is based on a system of governing equations with simple effective viscosity model accounting for turbulence the gas phase. The numerical model takes into account heating of the solid fuel by the heat flux from hot gas flow, melting of the fuel and formation of the molten layer on the grain surface. The molten layer of solid fuel considered as incompressible, high-viscosity liquid; its mechanical interaction with the gas flow leading under certain conditions to the development of instability, formation of surface waves and shedding of molten material by the flow. Equations are solved on a Cartesian mesh by the Volume Of Fluid (VOF) approach. Simulations are performed for a slab of solid fuel (wax) with subsonic flow of hot gas above it. It is shown that the molten layer loses its stability under certain condition, resulting in the formation of waves on the surface of liquid layer. The results of numerical simulations agree qualitatively with known experimental data.