The existence of supersonic second combustion mode detonation discovered by Mallard et Le Chatelier and by Bertelot et Vieille in 1881 posed the question of mechanisms for transition from one mode to the other. In the period of 1959-1969 experiments, by Salamandra, Soloukhin, Openheim, and their co-workers provided insights into this complicated phenomenon. Since then among all the phenomena relative to combustion processes deflagration to detonation transition is, undoubtedly, the most intriguing one. Deflagration to detonation transition (DDT) in gases is relevant to gas and vapor explosion safety issues. Knowing mechanisms of detonation onset control is of major importance for creating effective mitigation measures addressing the two major goals: to prevent the DDT in case of mixture ignition, or to arrest the detonation wave in case it was initiated. The new impetus to the increase of interest in deflagration to detonation transition (DDT) processes was given by the recent development of pulse detonation devices. The probable application of these principles to creating the new generation of engines put the problem of pulse detonating devices (PDD) effectiveness on top of current research needs. The paper contains the results of theoretical and experimental investigations of DDT processes in combustible gaseous mixtures. In particular, the paper investigates the effect of cavities incorporated in PDD on the onset of detonation in gases. Extensive numerical modeling and simulations allowed studying peculiarities of deflagration to detonation transition in gases in tubes incorporating cavities of a wider cross-section. The presence of cavities essentially affects the combustion modes being established in the device and its dependence on the governing parameters of the problem. The presence of cavities in the ignition section turns the increase of initial mixture temperature into the DDT promoting factor instead of the DDT inhibiting factor.
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