Combustible gas cylinder detonation upon incident shock focusing

Two-dimensional interaction of a shock in air with elliptic area (two-dimensional gas bubble) filled with propane-oxygen mixture with addition of heavy gas is numerically studied using Euler’s equations. Propane combustion is modeled with one-stage Arrhenius kinetics. Three different ignition regimes are found: direct detonation initiation by sufficiently strong shock, detonation near the triple point formed during weaker shock refraction and detonation at the focusing point of even weaker shock. The latter regime is observed only for significantly elongated bubbles. Detonation initiation regime dependence on shock Mach number and bubble diameter ratio is determined. It is shown that due to bubble elongation, critical Mach number may be significantly lowered in comparison with direct initiation.