Computational study of condensed-phase kinetics during combustion of pure RDX

A computational model for constant pressure combustion of RDX monopropellant has been developed to analyze the significance of condensed phase decomposition process. The model is based on conservation equations and takes into account detailed chemical kinetics in the condensed phase. Experimentally measured values of the melt layer thickness, the burn rate, and the propellant burning surface temperature are provided as input to the model. The extent of RDX decomposition in the melt layer is calculated and compared against values obtained in previous studies with global reaction mechanism for the condensed phase. Systematic sensitivity analysis of various model parameters, which affect RDX decomposition in condensed phase, is also performed. The results show that RDX mole fraction at the propellant burning surface is 90% at atmospheric pressure. This value is very sensitive to the kinetic rate parameters of the HONO-elimination step for RDX. The effect of experimental uncertainty in measurement of temperature and burn rate is comparatively small. The effect of higher pressures is also examined. It is found that at higher pressure the extent of RDX decomposition is significantly higher. This suggests that the significance of condensed phase decomposition process increases with pressure.