Improvements to RDX combustion modeling

Abstract

Many improvements have been made to models of RDX combustion in the past few years. The onedimensional model presented in this paper, models the solid, two-phase, and gas regions using complex kinetics and concentration and temperature dependent thermophysical properties. Calculated values agree well with experimentally determined burn rate, ap, melt layer thickness, surface temperature and species concentration profiles. When including laser-assisted burning in the model, a dark zone appeared similar to that seen experimentally. With the laser assisted case, the chemistry controlling the burn rate is significantly different from cases without the laser heat flux. Calculations show that the melt layer thickness is determined primarily by the liquid thermal conductivity and the surface temperature is controlled by the vapor pressure correlation. All other model predictions are relatively insensitive to these parameters. The weakest areas of the model remain the condensed phase decomposition and evaporation/condensation sub-model. Nomenclature A = area (cm) A = pre-exponential rate constant c = heat capacity (erg/g K) C = molar concentration (moles/cm-*) Ea = activation energy (cal/mole) H = molar enthalpy (erg/mole) h = specific enthalpy (erg/g) kk = number of gas phase species rh = mass flow rate (g/s) n = number of bubbles per volume 1 e 13 bubbles/cm^ p = pressure q = rate of progress variable (moles/cm s) rb = burn rate (cm/s) R = universal gas constant s = sticking factor T = temperature (K) u = gas velocity (cm/sec) V = diffusion velocity (cm/sec) W = average molecular weight (g/mole) W = molecular weight (g/mole) W = molar rate of production (moles/cm s) x = distance from 2-phase-gas interface (cm) X = mole fraction Y = mass fraction P = temperature exponent rate constant