Mechanisms of the amplification of a shock wave passing through a cool flame zone

A theoretical explanation of the Shchelkin-Sokolik effect, that is the dependence of the predetonation distance on the duration of thermal pretreatment of the explosive mixture before its ignition with an external source, is presented. Gasdynamic and kinetic calculations of the direct initiation of detonation in an n-pentane-oxygen mixture based on a simplified and a detailed kinetic mechanism are performed. It is demonstrated that a thermal pretreatment of the mixture causes a shortening of the predetonation distance, with the shortest predetonation distance being achieved when the shock wave arrives at the moment the cool flame arises. The calculated and measured dependences of the predetonation distance on the duration of thermal pretreatment of the mixture are demonstrated to be satisfactory agreement. The role played by the wall reactions is discussed.