Consistent Kinetic-Continuum Recombination Model for High Temperature Reacting Flows

TL;DR

This paper develops a consistent kinetic-continuum recombination model for high-temperature reacting flows based on ab initio data, capturing vibrational energy effects and non-Boltzmann distributions, validated through simulations.

Contribution

It introduces a novel recombination model derived from ab initio data that accurately accounts for vibrational energy states and non-equilibrium effects in high-temperature flows.

Findings

The model predicts high vibrational energy favoring in recombination.

Analytical expressions for vibrational energy and distribution functions are derived.

Simulation results align well with existing models, validating the approach.

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.