Thermally nonequilibrium effects in shock-induced nitrogen plasma: modelling study

Abstract

A careful analysis of thermally nonequilibrium processes in shock wave nitrogen plasma based on the accurate state-to-state model is conducted. The developed model takes into consideration electron-vibration-chemistry coupling and describes with high accuracy a vast set of experimental data obtained behind the shock wave and in the post-discharge region. The computations show the absence of a Boltzmann distribution over the vibrational levels both in the ground and in the excited states of nitrogen molecules. The prediction ability of the thermally nonequilibrium model of mode approximation is analysed. It is shown that the model of mode approximation, even at moderate shock wave velocity (ush > 2.5 km s−1), can result in the overestimation of vibrational temperatures of nitrogen molecules, both in the ground and in the excited and N2(B 3Πg) electronic states and, conversely, in the underestimation of translational temperature. It is demonstrated that plasmachemical reactions with charged species come into play at rather high shock wave intensity (ush > 6 km s−1). The neglect of these processes can lead to the overprediction of the values of translational and vibrational temperatures and to the underprediction of the concentrations of N(4S), N(2D) and N(2P) atoms.