Detonation initiation by high-voltage nanosecond discharge

An experimental study of detonation initiation in a stoichiometric propane-oxygen mixture by high-voltage nanosecond gas discharges was performed in a smooth square tube with a 20 mm transverse size. The discharge study showed that two major modes of discharge development were realized under the experimental conditions: a spark mode with high-temperature channel formation and a streamer mode with nonuniform gas excitation. Under spark initiation, simultaneous ignition inside the discharge channel resulted in a conventional deflagration-to-detonation transition (DDT) via an adiabatic explosion. The DDT length and time at 0.3 bar of initial pressure amounted to 250 mm and 300 ¿s, respectively. Under streamer mode at an initial pressure of 1 bar, a successful DDT via a gradient mechanism was observed due to nonuniform mixture excitation. The gradient mechanism implied a DDT time of 150 ¿s, an initiation energy of 1 J, and a DDT run-up distance of 50 mm.