Combustion at the interface of a laminate system of solid oxidizer and solid fuel

Abstract

The two-dimensional flow field in the vicinity of the interface between laminae of a solid oxidizer and solid fuel under steady-state conditions is solved for empirical inputs, taking into account the nonplanarity of the burning surfaces of the two laminae. The experimentally observed nonplanar burning surface under steady-state conditions is used to prescribe the upstream boundary conditions to the gas phase domain. The regression rate of the burning surface along the laminar interface, determined experimentally, is also used as an input. This decouples the condensed phase energy balance from the gas phase fluid dynamics, and assigns the distribution of surface temperature along the burning surface. The equation for two-dimensional energy conservation in the condensed phase is also solved, with the heat flux balance giving a boundary condition across the burning surface. A distribution of heat release rate is assumed in the gas phase, and the gas phase energy equation is solved iteratively with a convergence criterion set by the interfacial heat flux balance across the burning surface. This obviates the need for a knowledge of the chemical kinetic details of the gas phase flame. The goal is to determine a realistic distribution of heat release rate which satisfies the burning surface profile and its regression rate, measured for a laminar system of ammonium perchlorate and polymethyl methacrylate at pressures below the self-deflagration limit of the former. The results indicate lateral heat conduction in the condensed phase from the oxidizer lamina to the fuel lamina. The computed distribution of heat release rate in the gas phase indicates the need to include heat release near the surface, as well as farther downstream at typical stand-off distances for the flame.