CRITICAL RADIUS OF EXPLOSIVE GASEOUS-MIXTURES WITH INITIAL CONCENTRATION GRADIENTS

A synthetic review of works concerning detonation of non-uniform explo sive mixtures allows to retain a criterion of detonation onset. This c riterion is due to Zel'dovich and then Makhviladze. The present study proposes to adapt Makhviladze's criterion to define the formation poin t of a quasi-stationary detonation in spatially non-uniform, nonstatio nary and non-preheated gaseous mixtures. The temperature increase of g aseous mixture is due to the travelling shock. This point is compared to the critical radius defining the distance for which the Chapman-Jou guet conditions are attained. The detonability of a non-uniform medium (propane/oxygen mixtures) is characterized by a small scale experimen tal investigation and by application of a simple advection-diffusion m odel.