Consistent Kinetic-Continuum Recombination Model for High Temperature Reacting Flows

Abstract: A recombination reaction model for high-temperature chemical kinetics is derived from ab initio simulations data. A kinetic recombination rate model is derived using a recently developed ab initio state-specific dissociation model and the principle of microscopic reversibility. When atoms recombine, the kinetic rate model shows that product molecules have high favoring for high vibrational energy states. A continuum recombination rate model is then derived analytically from the kinetic recombination rate model. Similarly, the expression for the average vibrational energy of recombining molecules is also derived analytically. Finally, a simple model for non-Boltzmann vibrational energy distribution functions is derived. The distribution model includes both depletion of energy states due to dissociation and re-population of states due to recombination where a Boltzmann distribution is recovered in chemical equilibrium. Isothermal relaxation simulations using the continuum dissociation and recombination model are performed and the results are compared with the state-of-the-art model.