Direct calculation of wave implosion for detonation initiation

Numerical simulations of imploding shock waves for detonation initiation are reported. We solve the one-dimensional Navier-Stokes equations and two-dimensional Euler equations for chemically reactive flows by the space-time conservation element and solution element method. One-dimensional results in cylindrical coordinates show that a converging shock produced by breaking a diaphragm for an initial pressure ratio of 1:0.2 atm is able to successfully initiate a detonation in an argon-diluted hydrogen/oxygen mixture (0.2H(2) + 0-1O(2) + 0.7Ar) initially at 300 K. The result also shows a two-shock implosion system caused by the interaction between the reflected primary shock and the imploding contact discontinuity. Two-dimensional solutions focus on imploding polygonal shock fronts. In each polygonal section, the imploding shock is analogous to a planar shock wave entering a channel with converging walls leading to complex wave reflections. Similar to that in the one-dimensional results, pressure histories in the focal region slow multiple implosions.