Nitramine flame chemistry and deflagration interpreted in terms of a flame model

The diversity of chemical kinetic time scales associated with nitramine decomposition has led to incorporation of two simultaneous overall reactions in the vapor phase mode of deflagration. This allowed derivation of an asymptotic burning rate formula, showing variable pressure dependence. The comprehensive model considers a reacting melt layer, coupled to the gas field through conservation conditions satisfied by all chemical species and enthalpy, and is solved numerically. The structure of the deflagration wave near the propellant surface is obtained, along with the overall pressure dependence of the surface temperature and the flame speed eigenvalue, comparing RDX and HMX. A mechanism of coupling between secondary reactions and heat feedback to the surface is proposed, and a quantitative measure of the effect of condensed phase exothermicity on burning rate is demonstrated.