Burning Rate Characteristics of Magnesium Sodium Nitrate Propellants

Abstract

The combustion phenomena of Mg-NaNO/sub 3/ propellants have been studied. Results of burning rate at different mixture ratios and particle sizes indicate that the compositions containing finer particle size (50 millimicron) NaNO/sub 3/ give higher burning rate at high fuel content of the mixture than at the stoichiometric ratio; whereas the compositions with coarser particle size (250 millimicron) NaNO/sub 3/ show increasing burning rate with increasing oxidiser content and give a maximum at stoichiometric point. Thermal decomposition results indicate that the condensed phase heat release at the propellant surface and the reactions in the vapour phase are responsible for variations in the burning rate. The decomposition products of finer size NaNO/sub 3/, react with Mg before Mg particles acquire sufficient energy for ignition, and lead to condensed phase heat release. This heat is maximum at high fuel content and causes high burning rate with low pressure and temperature sensitivity. The increase in the oxidiser content reduces the condensed phase heat due to formation of metal agglomerates and causes lower burning rate with high pressure and temperature sensitivity. After the Mg particles acquire sufficient energy for ignition the decomposition products of coarser size NaNO/sub 3/ diffuse out along with Mg and react in the vapour phase. This causes an increase of burning rate with increase in the oxidiser content of the mixture up to the stoichiometric ratio with a pressure and temperature dependence.