Kinetics of nonequilibrium processes in air plasma formed behind shock waves: state-to-state consideration

Abstract

A new kinetic thermal nonequilibrium model for air plasma, considering vibrations of , and molecules in both the ground and electronically excited states in a state-to-state approach, was developed. The model treats in a consistent way the coupling of vibrational–electronic excitation of molecules and plasma chemical reactions as well as thermal nonequilibrium between translational degrees of freedom of electrons and heavy particles. The model was validated against the values of the radiation intensity of the and bands measured in the shock-tube experiments in an – mixture at shock wave speeds up to . Numerical analysis of thermally nonequilibrium processes in shock wave air plasma using the developed state-to-state model was conducted. It was shown that behind the shock front, a non-Boltzmann distribution over vibrational levels of , and molecules in both the ground and electronically excited states forms, but at the same time low vibration levels of these molecules are still populated in line with the local Boltzmann distribution with its own vibrational temperature. However, at extremely high shock wave velocities () disruption of the Boltzmann distribution of and molecules starts from vibrational levels with quantum numbers , so it is worth using the state-to-state consideration in such cases.

Submicrosecond Spectroscopy of Lightning‐Like Discharges: Exploring New Time Regimes

“…We think that this disagreement is mainly due to the fact that the very high speed recorded spectra include light emissions from both the hot core air plasma channel (kept at a lower gas density than ambient) and the hot and overpressure shock front. Right behind the shock front thermal nonequilibrium (different values of translational, vibrational, and electronic temperatures) can occur that could also cause disruption of the Boltzmann equilibrium distribution for sufficiently high shock front speeds as the ones estimated here (Kadochnikov & Arsentiev, 2018). .…”

“…Overpressure, equilibrium, and black-body dynamics of the lightning-like plasma channel were investigated. We have computed fast (>4 km/s) propagation speeds for the discharge shock front that, as discussed in previous works (Kadochnikov & Arsentiev, 2018), could lead to the disruption of the Boltzmann equilibrium right behind the shock front in posttrigger submicrosecond times. However, Boltzmann equilibrium was found to be kept at very early pretrigger times (where synthetic spectra based on equilibrium calculations at 1 atm nicely agree with measured spectra) and, depending on the discharge, at "late" times such as ≃2 μs (SI and small spark) or ≃10 μs (LI) after triggering when the shock front speed has considerably decreased and the pressure inside the discharge channel approaches the ambient one.…”

Interaction of Atomic Nitrogen with Electronically Excited Molecular Oxygen: a Theoretical Study

“…[16]). Так, ранее была построена уровневая кинетическая модель для воздушной плазмы, учитывающая широкий набор химических и плазмохимических реакций с участием молекул как в основном, так и в возбуждённых электронных состояниях [17]. В рамках этой модели были проведены расчёты типичных параметров неравновесного газа за фронтом сильной ударной волны и выделены процессы, оказывающие наиболее существенное влияние на изменение компонентного состава воздушной плазмы.…”

“…, для которой константа скорости достоверно не определена. Стоит отметить, что данные реакции важны не только для учета возбуждения синглетного кислорода, но и для уточнения кинетической модели для азотной (воздушной) плазмы в целом [17].…”

“…1. Изменение мольных долей компонентов азотной плазмы в основном электронном состоянии N2(X 1 g + ), N( 4 S), O2(X 3 g), O( 3 P), NO(X 2 r), а также электронно-возбуждённых молекул O2(a 1 g) в потоке за фронтом сильной ударной волны при начальных условиях перед ударной волной T0 = 300 K, P0 = 0.1 торр и u0 = 8 км/с, определённое с использованием уровневой кинетической модели [17]…”