Comprehensive analysis of the effect of atomic and molecular metastable state excitation on air plasma composition behind strong shock waves

Abstract

A detailed analysis of the processes of charged and neutral species formation in N 2 -O 2 -Ar system behind strong shock waves is conducted on the basis of an extended thermally non-equilibrium kinetic model with careful allowance of reactions with electronically excited atoms and molecules and vibration-electron-chemistry coupling. The model is validated against experimental data such as measurements of electron number density behind the strong shock wave front, temporal profile of O 2 vibrational temperature, temporal evolution of NO(γ ) radiation intensity in the post-shock region and values of time instants at which maximum quantities of radiation intensity of N 2 (1+) and N + 2 (1−) bands are achieved. It is demonstrated that the model without the allowance of processes involving electronically excited atoms and molecules overestimates the concentrations of both charged and neutral species. For electron and NO concentrations the overestimation can come up to a factor of 2. The computations also indicate the existence of a strong vibration-electron-chemistry coupling in the air plasma produced by the strong shock wave. Only the model, which takes into account such an interaction, makes it possible to properly predict the variation of gas dynamic parameters and species concentrations in the post-shock region.

Vibrational and electronic collisional-radiative model in air for Earth entry problems

“…Atomic species can be electronically excited or ionized. The rate coefficients of some of these processes under heavy particle impact have been reported by Capitelli et al 22 and Starik et al 39 They have been used in the present study. Otherwise, the rate coefficient…”

“…The electron density is negligibly small. The related rate coefficients have been taken from Capitelli et al, 22 Kossyi et al, 38 Park, 30 and Starik et al 39 Few data can be found in the literature for theses processes. When the rate coefficient is not reported in the previous references, we have used data due to Park et al, 40 Bhadra and Ghosh, 41 and Drawin 42 to derive the analytical form…”

“…Dissociative recombination, excitation transfer, charge exchange, and reassociation (concomitant neutral and charge exchange) have been taken into account. For the dissociative recombination process, the backward process (associative ionization) of which is involved in the production of the first free electrons and ions, 55 we have used the rate coefficients due to Motapon et al, 56 Peterson et al, 57 and Peverall et al 58 For excitation transfer, charge exchange and reassociation, we have used the rate coefficients given by Alekseev et al, 59 Capitelli et al, 22 Dunn and Kang, 60 Kossyi et al, 38 Losev et al, 61 Starik et al, 39 and Teulet et al 62 …”

Dissociative recombination in reactive flows related to planetary atmospheric entries

“…• vibrational processes (vibrational excitation under electron, N 2 and N impact) [7][8][9], • dissociation of electronic excited states of N 2 and of all electronic states of N + 2 under electron impact [10], • electronic excitation under electron, N 2 and N impact [3,10,11,[13][14][15][16]18], • excitation transfer [11,17,18],…”

Advanced Models in Shock Waves

“…The equations have been modified in order to take into account reacting gas mixtures following Eqs. (3) to (6) [26][27][28][29][30][31][32]. The populations of the radiating electronic states of molecules, which are considered as independent chemical species in the model [33], are calculated by solving the corresponding kinetic equations.…”