Electronic-specific modeling of a nonequilibrium recombining N₂/Ar plasma and comparison with experiments

Abstract

An electronic-specific kinetic model for nitrogen–argon plasmas is developed by the reduction of a state-of-the-art vibronic-specific model. The model is used to study the nonequilibrium recombination of high-temperature nitrogen–argon plasmas, initially in local thermodynamic equilibrium at high temperature and atmospheric pressure, and forced to cool rapidly. Simulations using the electronic-specific model are performed along the axis of the tube. The results are compared with measurements of electron densities, ground state species (N), and several excited electronic states of N, N2(B, C), and N2+(B), obtained in two sets of experiments. The simulations and measurements generally agree within a factor of 3, while the nonequilibrium degree is typically several orders of magnitude. A detailed analysis of the main processes governing the recombination of the plasma indicates that the transfer of electronic energy from N2(A) to N(2P) and the three-body recombination of N2 by N-impact play key roles in the recombination kinetics. We show that accurate predictions of species densities depend primarily on accurate predictions of N2(A) and N(2P) densities, which must be the focus of future research efforts.