Fast deflagration-to-detonation transition

Studies of fast deflagration-to-detonation transition in gas and drop air-fuel explosive mixtures are reviewed. Fast deflagration-to-detonation transition is understood as the appearance of detonation at which a turbulent flame is sped up to a much lower velocity than that required for the classic deflagration-to-detonation transition in a straight tube with smooth or rough walls. The main goal of studies was to determine conditions under which fast deflagration-to-detonation transition was possible in weakly sensitive explosive mixtures at very low ignition energies. Examples of fast deflagration-to-detonation transitions checked experimentally and by multidimensional numerical calculations are given, including deflagration-to-detonation transitions (1) in a tube segment with regular obstacles of a special shape, (2) in tube coils, and (3) in tubes with U-shaped bends. In all cases, fast deflagration-to-detonation transition occurs because of the formation of distributed ignition zones in reflections of a running shock wave formed by an accelerated flame. The use of various combinations of reflecting elements can induce fast deflagration-to-detonation transition in an air mixture of aviation kerosene at ignition energies at a level of 5 J.