Influence of Detonation Cell Size on Propagation of Cylindrical Detonation Wave

Abstract

To achieve reliable transmission of detonation wave to a pulse detonation engine (PDE) combustor, authors examined a combination method of "predetonator", "reflector" and "overfilling of the driver gas" experimentally. A detonation wave propagates around our reflector changing its shape through three transition processes; from planer to cylindrical, toroidal, and planar again. Here, successful transmission to self-sustainable expanding cylindrical detonation wave is key issue. The authors used high sensitivity driver gas mixture (stoichiometric H₂-O₂ mixture) for the center of the cylindrical part to make the cylindrical detonation wave transmit in target gas mixture easily. To generalize the influence of the target gas composition on the necessary overfilling radius of the driver gas mixture, we employ stoichiometric H₂-O₂ mixture diluted by nitrogen or argon as target gas mixture. In this study, we showed that the ration of width of the cylindrical path on cell size of propagation limits of both dilution cases are about 1 when the driver gas is supplied enough to create a stable cylindrical detonation wave over 50 mm. Accordingly, when the cell size of the target gas mixture becomes over comparable size to the width of the cylindrical path, the stable expanding cylindrical detonation wave does not sustain.