Oxidizer Size Distribution Effects on Propellant Combustion

Abstract

The effect of the oxidizer size and size distribution on the pressure and temperature sensitivity for a nonaluminized composite solid propellant was investigated using a new mathematical model called the Petite Ensemble Model. Calculations were made using the new model, taking into account the oxidizer size and size distribution in determining the burning rates, rate exponents, and temperature sensitivities. Results were obtained for both unimodal and bimodal propellants with oxidizer particle sizes ranging from ultrafine (0.7 /*) to coarse (400 /*). For unimodal propellants, it was determined that the burning rate was higher for the smaller oxidizer sizes, as would be expected. Moreover, the rate exponent was larger for the small and large oxidizer particles with a minimum exponent obtained for some intermediate oxidizer diameter. Temperature sensitivity was found to be higher for propellants with larger oxidizer particles. However, it was found that the temperature sensitivity was constant for small particles. It was shown that for large particles, the temperature sensitivity and rate exponent decreased as the oxidizer distribution was widened.