Ignition of Gas Mixtures by Electric Discharges between a Heated and a Cold Electrode : Application in Breakflash Apparatus for Intrinsic Safety Testing

Abstract

THE thermal theory of ignition of gases explains certain phenomena in the ignition of explosive mixtures by electric sparks involving capacitive and break or make discharges. However, a number of important questions for theory as well as practice remain to be answered. In this connexion the author has made some introductory investigations on the ignition of explosive gas mixtures having in mind the simplified assumption that the ignition process is essentially thermal in character, so that some critical temperature is involved in the initiation of the ignition. This temperature may be attained by a single process, such as the heating of a wire, or by more than one process, for example, the heating of a wire plus an electric discharge. In the case of an 8.3 per cent methane–air mixture the initiation of ignition involves a certain critical volume of gas attaining a minimum temperature.