Combustion response of ammonium perchlorate composite propellants

The Cohen and Strand model for ammonium perchlorate (AP) composite propellants is applied as boundary conditions, one for AP and one for binder, in solving the heat conduction equation in each to compute linear and nonlinear combustion response properties for each and for the aggregate propellant. Iterations couple AP and binder through the quasi-steady flame processes. Illustrative results for linear response functions (pressure coupled and velocity coupled) are presented for a monomodal AP propellant showing effects of varying AP size, pressure, and crossflow speed. Examples of nonlinear responses to arbitrary waveforms are also shown. The model predicts a very large response at high pressures with coarse AP due to AP monopropellant combustion, underpredicts peak response amplitude for low pressures due to a possible change in mechanism, and shows a stabilizing effect of the diffusion flame. A quantitative comparison with response function data is limited to one well-characterized research formulation. Mechanistic implications are discussed, including recommendations for future modeling work.