A study of the gas dynamics of combustion of a mixed solid propellant with pressure fluctuations

The non-stationary burning rate of a solid rocket propellant under harmonic variations in pressure over the combustion surface is studied. The physical and mathematical model is based on the equations of heat transfer and oxidizer decomposition in the solid phase, and on the flow model for the reacting products of solid propellant gasification. Calculations are carried out for the unsteady burning rate of mixed solid propellants with harmonic pressure variations over the combustion surface. The dependence of the amplitude of the burning rate fluctuations on the frequency of the pressure variations are obtained. The amplitude of the burning rate varies non-monotonically with frequency. As the frequency increases, the amplitude first increases and then decreases. At a frequency of pressure variation with a semi-period greater than or equal to the characteristic time of relaxation for heat transfer in solid propellants, the instantaneous burning rate at the lowest point of the pressure curve is lower than the equilibrium value and is higher at the highest point. At high frequencies, the burning rate exceeds the corresponding equilibrium value at minimum pressure and is lower than the equilibrium value at maximum pressure.