The structures of fast deflagrations and quasi-detonations

Abstract

Flame propagation for stoichiometric H 2 -O 2 mixtures ( p o <150 Torr) in a channel filled with obstacles has been examined. It was observed that, upon ignition by a glow plug, the resulting flame accelerated very rapidly as it propagated down the channel. Eventually, it either reached a steady-state velocity as a fast deflagration or became a quasi-detonation by way of a transition. The structures of these two forms of combustion waves were examined using schlieren photography, pressure transducers and smoke foils. The controlling mechanisms for the propagation of the two waves were found to be turbulent burning and shock heating, respectively. Results showed that obstacles inside the channel play a key role in the propagation of fast deflagrations and quasi-detonations. In a case of a fast deflagration the reaction zone is perturbed repeatedly by the obstacle-induced transverse waves; as a result of shock-flame interaction, the high burning rate is maintained. On the other hand, the presence of obstacles prevents a quasi-detonation from propagating at the Chapman-Jouguet detonation velocity.