Extinction of Ammonium Perchlorate: Similarity Between Rapid Depressurization and Low-Pressure Deflagration Limit

The extinction of Ammonium Perchlorate (AP) monopropellant due to two transient processes, namely rapid depressurization and Low-Pressure Deflagration Limit (LPDL), was studied. The critical depressurization rate was determined experimentally using silica grease on the sides of the AP pellet to reduce convective heat loss. The critical depressurization rate was found to lie between 1820 and 1950 MPa/s. The computed critical depressurization rate was found to be 1450–1500 MPa/s with variable thermal properties in the condensed phase. The extinction of AP due to LPDL was studied using different heat fluxes imposed on the surface. Case I involved the constant heat flux imposed on the surface and suddenly reduced to zero, while case II involved constant heat flux imposed on the surface and linearly reduced to zero. The combustion stability was checked for both cases, and it was found that the combustion remains in a stable regime. For case I, the AP did not burn below 5.0 MPa when the imposed heat flux of 3 MW/m2 was suddenly reduced to zero in 0.1 s. However, for case II, the AP was found to burn up to 1.6 MPa when the imposed heat flux of 3 MW/m2 was linearly reduced to zero in 0.5 s. The extinction boundaries of two unsteady processes, extinction by rapid depressurization and extinction due to LPDL, were determined, and the two processes were shown to have similar physical behavior.