The burning of periodic sandwich propellants

We develop a mathematical model which describes the unsteady regression rate determined by simultaneously solving the combustion field in the gas-phase and the thermal field in the solid-phase, with appropriate jump conditions across the gas/solid interface. The model takes into account the AP decomposition flame, reaction between the AP products and the binder gases, properties of the AP and binder, variable gas-phase transport properties, and the unsteady non-planar regressing surface. A Hamilton-Jacobi equation is used that governs the propagation of the unsteady regressing surface. Although the formulation is general, we consider here only the periodic sandwich geometry. Numerical studies show that the surface evolves into a quasi-steady propagating front. The regression rate is calculated as a function of pressure, fuel matrix thickness, AP particle size, and gas-phase Peclet and Damöhler numbers. The gas-phase flame structure as well as the surface shape are also shown.