A Unified Theory of Ammonium Perehlorate Deflagration and the Low Pressure Deflagration Limit

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Abstract
A unified theory is proposed to explain using a single framework the hitherto separately treated aspects of the combustion of ammonium perehlorate: burning rate, low-pressure deflagration limit and ignition. The model on the basis of which the theory is formulated incorporates the experimentally observed microstructure of the burning surface of ammonium perehlorate, which provides an intermediate heat sink in an overall adiabatic system. The theory explains the existence of the low-pressure deflagration limit of ammonium perehlorate, which has eluded previous attempts at theoretical explanation. Furthermore, the theory predicts accurately the variation of the limiting pressure with initial solid temperature and also the nearly constant burning rate at the low-pressure deflagration limit regardless of initial solid temperature. The comparison of the theory and experiment for the low-pressure deflagration limit and burning rate of ammonium perehlorate indicates that the same reaction mechanisms prevail during deflagration and near the pressure limit and that the extinction is due to heat loss rather than to a change in reaction mechanism. The theory also suggests a possibility of modifying the low-pressure deflagration limit by physical means. The rates of the gas-phase reactions are found to be well-represented by second-order overall kinetics.