Detonation and deflagration initiation at the focusing of shock waves in combustible gaseous mixture

Detonation and deflagration initiation under focusing conditions in a lean hydrogen-air mixture was experimentally investigated. The experiments were carried out in a shock tube equipped with the laser schlieren system and pr essure transducers. Two-dimensional wedges (53 degrees and 90 degrees), sem i-cylinder and parabola, were used as the focusing elements. The peculiarit ies of mild and strong ignition inside the reflector cavity were visualized . A hydrogen-nitrogen mixture was taken for comparison between reactive and inert mixture. It was found that mild ignition inside the reflector cavity can lead to detonation initiation outside the cavity. Schlieren pictures o f the process were obtained and the dependence of the distance of detonatio n initiation on Mach number of the incident shock wave was established.