On the role of ‘hot’ atoms in plasma-assisted ignition

Abstract

This paper discusses the processes leading to the formation of ‘hot’ atoms and radicals possessing excessive translational energy in high-voltage NS pulse discharges. It is shown that the formation of such ‘hot’ atoms occurs efficiently both in the dissociation of molecules by direct electron impact, and in the collisional quenching of electronically excited states. Depending on the magnitude of the reduced electric field in the discharge, reactions of these ‘hot’ atoms increase the initial concentration of radicals in the discharge afterglow two to three times when compared with the values calculated without effects of translational non-equilibrium. The role of thermally non-equilibrium excitation has been demonstrated in the formation of the initial distribution of the chemically active components in the mixture and its influence on the kinetics of ignition initiation at low and high temperatures. It was found that in undiluted mixtures the presence of ‘hot’ atoms can significantly decrease an ignition threshold and accelerate a low-temperature oxidation.