Initial flame acceleration in an explosive gas

Abstract

The paper is concerned with pressure waves generated by a flame during the initial phase of its acceleration in a detonation tube filled with a stoichiometric hydrogen + oxygen mixture. The process was observed by means of streak schlieren photography with simultaneous pressure measurements at several stations in the tube. Experimental records revealed in considerable detail the characteristics of pressure waves and yielded information on the structure of the reaction zone with a noticeable effect of the transition from a wrinkled laminar to a turbulent flame. Marked influence of the mode of ignition (electrical obtained by spark discharge, chemical by pilot flame, and thermal by glow coil) on the process of flame acceleration was demonstrated. It is shown that the generation of pressure waves by the flame can be accounted for by the change in the rate of heat release brought about by the increase in the surface area of the combustion front. The computed acceleration of the flame and the structure of the pressure wave ahead of it were in a satisfactory agreement with experimental observation.