On the peculiar properties of initiation and propagation of multifront detonation

Abstract

At initiation an external source must initiate a chemical reaction in the combustible mixture and ensure its self-sustaining propagation over the whole volume of the mixture. Traditionally, the critical energy is considered as the measured value of successful initiation of a mixture, providing 100% excitation of the process – combustion or detonation. Actually, the initiation of combustion or detonation process has a “threshold” nature (“yes” – “no”). The spatial-temporal law of initiator energy allocation has a noticeable effect on the critical initiation energy. The instability of the system of equations of gas dynamics and chemical kinetics is manifested in the multifront nature of the detonation front and the cellular structure of the trajectories of the transverse waves. The important question is the moment and place of occurrence of such a structure, especially for expanding waves. Along with the kinetic- gasdynamic instability of the combustible mixture, a certain role is played by the instabilities introduced by the initiator: for example, the constrictive (sausage) electromagnetic instability of an electric conductor with a current, the Meshkov-Richtmeier instability at the expanding boundary of the liquid metal of the exploding wire, etc. In this report the existing problems of initiation and propagation of detonation are discussed based on modern data, including the results of the author’s research on these issues.