Exploratory experiments on the ignition by laser-induced sparks of chemically reactive gaseous mixtures, both detollable and nondetonable, were performed. It was found that the minimum energy required to induce breakdown was of sufficient magnitude to generate a strong spherical blast wave. The ignition mechanisms are strongly coupled to the dynamics of the decaying blast. For nondetonable gases, it was observed that initially the blast wave is of sufficient strength to result in auto-ignition of the reactive media with the reaction front trailing immediately behind the spherical shock front. As the blast expands, the reaction front decouples rapidly from the shock and propagates as a deflagration wave dependent on the transport properties of the medium. For detonable mixtures there exists a critical energy above which direct initiation of a spherical detonation wave occurs. This critical ignition energy varies inversely with the initial pressure of the mixture showing the same qualitative behavior as the variation of the induction time with initial pressure. For ignition energy well below this critical value, similar behavior of rapid decoupling to a spherical deflagration wave as in the case of nondetonable gases was observed. For ignition energy close to the critical, decoupling followed by re-establishment to a spherical detonation wave occurs. © 1969 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.
