Critical radius of explosive gaseous mixtures with initial concentration gradients

A synthetic review of works concerning detonation of non-uniform explosive mixtures allows to retain a criterion of detonation onset. This criterion is due to Zel'dovich and then Makhviladze. The present study proposes to adapt Makhviladze's criterion to define the formation point of a quasi-stationary detonation in spatially non-uniform, non-stationary and non-preheated gaseous mixtures. The temperature increase of gaseous mixture is due to the travelling shock. This point is compared to the critical radius defining the distance for which the Chapman-Jouguet conditions are attained. The detonability of a non-uniform medium (propane/oxygen mixtures) is characterized by a small scale experimental investigation and by application of a simple advection-diffusion model. Accepted 3 March 1996