A three-phase model of HMX combustion

Abstract

The solid rocket propellant ingredient RDX has received a lot of research attention in recent years by both experimentalists and modelers. There has been fairly good agreement between predictions by models and experimental data. In this paper, the three-phase, one-dimensional RDX model is extended to a similar ingredient, HMX. All model inputs were determined independent of the model except for the heat capacity and thermal conductivity of HMXliquid for which no experimental data was found. Reasonable correlation with experimentally determined burn rate, surface temperature, adiabatic flame conditions, melt layer thickness, and some gas-phase species concentration profiles was made using this model. Sensitivity analysis indicates that the adiabatic flame conditions are controlled by the specification of the thermodynamic properties of the solid and liquid phases. The surface temperature is controlled by the vapor pressure correlation, and the burn rate is largely controlled by the heat feed back from the gas-phase flame, or in other words, the gas-phase mechanism. Sensitivity analysis indicates that differences noted in combustion characteristics of HMX and RDX are likely caused by differences in vapor pressure and melting temperature, while the similarity of burn rate data is attributed to the similarity of the gas-phase flames. The sensitivity analysis also indicates which model inputs require further study.