Blast wave propagation in glow to spark transition in air

Abstract

The formation and propagation of post-discharge blast waves are studied theoretically and the minimum rate of energy transfer between electrons and neutral particles is deduced in the case of a positive point-to-plane discharge in air, described and numerically analysed in a previous paper by the authors. In this type of discharge, the injection of energy in the discharge is spread in time. The blast waves generated by the discharge constitute a set of waves with a complex structure. They first propagate separately, then merge in a single wave. The core of the discharge remains perturbed for a long time (i.e. low neutral densities and high temperatures) after the discharge crossing and thus constitutes a privileged path for possible recurring discharges. The classical analysis of blast waves was adapted to the experimental situation in which the energy injection is spread in time and space. The influence of the injected energy on the expansion radius of the wave has been studied and the authors show that the minimum rate of energy transfer f_min between electrons and neutral particles in the glow to spark transition can be deduced from the Schlieren records. In the experiments analysed, the rate of energy transfer f is greater than 20+or-6%.