Some observations by schileren technique of the propagation of flames in a closed vessel

Abstract

The study of flame propagation at constant volume presents problems of particular technical interest both in the analysis of flame propagation and in the application of the results to such practical phenomena as knock in spark ignition engines. In recent years various photographic combustion studies in engine-like apparatus have been made to elucidate flame propagation under actual engine conditions, including the mechanism of knock. In this field the work of Miller (I), Osterstrom (2), Taylor, Taylor, et al. (3), is outstanding. The course of the rapid reactions taking place in the engine cylinder has been followed by stroboscopic sampling by Egerton, et al. (4), and more recently by Downs, et al. (5). As a result of these various experimental studies, it now appears possible to present a reasoned explanation of the knock process at least for some fuels. Precise analysis of flame propagation in the above studies is made difficult by the size and shape of the combustion chamber and also by piston and port induced gas movements. In the present experiments combustion processes in a long, constant volume bomb were studied using simultaneously direct, and Schlieren photography. Preliminary investigation has provided records showing in fine detail, the form and structure of the flame front at all stages of the combustion process and has enabled a study to be made of such phenomena as flame arrest, and the development of pre-reactions in the end gas leading to autoignition and knock.