Recent Advances in the Numerical Simulation of Heterogeneous Solid Propellant Combustion

Abstract

In recent years a considerable amount of effort has been dedicated to computational simulations of heterogeneous solid propellant combustion.  A variety of tools have emerged from these studies.  The most important are the modeling of propellant morphology, homogenization, and an unsteady three-dimensional coupled combustion code with complete coupling of the gas-phase combustion processes and the solid-phase heat conduction across the unsteadily regressing nonplanar propellant surface.  The combustion code is both parallel and scalable.  These tools have been applied to the study of non-aluminized heterogeneous propellants, including the periodic sandwich (a periodic array of alternating AP and binder slices) and disks or spheres randomly packed.  Comparisons of surface profiles to those of experimental observations for sandwich configurations and comparisons to experimental burn rates for a variety of propellant compositions over a wide pressure range are presented.  These results are encouraging and suggest that multi-dimensional numerical simulation is a viable tool for the understanding of combustion characteristics of composite propellants.  In the first part of the talk we discuss how this framework is used to solve a variety of problems.

Our first studies employed a body-fitted grid along the moving interface by means of a mapping technique relevant when the surface is single valued.  The computational difficulties are significantly increased when the burning surface undergoes a complex or multi-valued shape.  Such shapes can arise, for example, when aluminum particles are embedded in the propellant.  In this case the mapping strategy must be abandoned in favor of a more general method; one such method, level sets, is presented.  We describe how it can be used to capture the injection process of aluminum particles into the gas-phase from the burning propellant.