Investigation of Self-Sustaining Waves in Metastable Systems: Deflagration to Detonation Transition

Self-sustaining waves can propagate in metastable media; energy needed to support such waves is released by the wave itself. The examples are waves of combustion and waves of boiling in overheated liquids. As a rule, two regimes of propagation exist: subsonic and supersonic. The difference is based on the different mechanisms of medium activation. Processes of transition between those regimes were less studied up to now, in comparison with pure subsonic or supersonic modes. Knowing mechanisms of controlling detonation initiation is important to work out effective preventive measures, such as suppressing deflagration-to-detonation transition in the case of combustible mixture ignition, and mitigation of a detonation wave in case it is already developed. On the other hand, the advantages of burning fuel in a detonation regime in comparison with slow burning at constant pressure attract increasing attention to pulse detonation burning chambers and to their possible application to new generation engines. The deflagration-to-detonation transition can be a principal stage of the work cycle in a pulse detonation engine, and the knowledge of details of this process and means of control can significantly decrease the predetonation distance and optimize the device. This work contains a review of the results obtained in theoretical and experimental investigations of deflagration-to-detonation transition processes in gases. Influence of internal geometry and flow turbulization on the detonation onset is considered; the influence of temperature and fuel concentration in the unburned mixture is discussed. Transitional processes of overheated liquid boiling up are also analyzed. [PUBLISHER ABSTRACT]