Ignition characteristics of the shock wave focusing in combustive gases

The two-dimensional plane shock wave focusing with the parabolic reflectors in combustive gases is numerically simulated, and the ignition characteristics of the detonation initiation are investigated. In the stoichiometric hydrogen/air mixtures under 20 kPa, the shock wave focusing with the incident Mach number 2.6-2.8 will generate two ignition zones. One is derived from the reflection shock convergence; the other is derived from the high temperature zone, which is induced by Mach reflection on the parabolic reflectors. Then the focusing shock wave with the incident Mach number 2.6-2.8 will induce the detonation initiation via deflagration-to-detonation transition. The initiation points locate on the tube wall, the parabolic reflector and near the second ignition point, separately. The corresponding initiation mechanisms are the shock wave reflection on the tube wall, the shock reflection on the parabolic reflector, and the interaction of the ignition-induced shock and the deflagration induced by the second ignition zone, respectively. Different ignition and detonation initiation processes result in various wave systems in the flow field, and lead to different wave dynamic processes of the detonation wave propagation.