Externally triggered steam explosion experiments: amplification or propagation?

Abstract

A vapor explosion is the rapid exchange of energy between a hot and cold liquid caused by, and resulting in, the propagation of shock waves through the liquid-vapor mixture. Many vapor explosion experiments have been performed using an external trigger to initiate the event. In general, the assessment of the explosive behavior has been to report the pressure history resulting from the ‘explosive interaction’. However, with the mutual dispersion of high temperature liquid within the colder temperature host liquid, the pre-mixed configuration represents substantial stored energy. With the imposition of an external trigger to fragment and rapidly mix the debris, some of this stored energy could be released without causing propagation of the event. This paper discusses the difference between amplification of a trigger pulse due to the release of stored energy and propagation of the explosion within the pre-mixed zone. Also, a criterion for deciding if propagation has occurred is provided. It is recommended that if the experiments do not satisfy this criterion, propagation of the event should not be concluded and the results should not be considered as a large-scale explosion. Rather such data should be considered as a characterization of what could occur within an explosion if an explosion (shock wave) could be initiated.