Relation of chemical and physical processes in two-phase detonations

Abstract

Both physical and chemical factors influence combusion instabilities and explosions in two-phase systems consisting of fuel liquid drops in a gaseous oxidizer. It is generally agreed that in two-phase detonations, fuel drops are broken up via a mass stripping mechanism and form combustible mixtures of fuel micromist and hot gaseous oxidizer in the wake of each parent drop. The large surface area between the micromist (micron size drops) and the hot oxidizer enable chemical reactions to proceed at a rapid enough rate to support the incident shock front. Therefore, the detonability of two-phase mixtures is affected by both the fuel drop breakup and the chemical energy release rate. An experimental study was undertaken to elucidate the relative importance of the roles of chemical and physical processes. Additives were employed to alter the physical properties (such as viscosity) and the chemical properties (such as ignition delay) of the fuel. In addition, fuel drop size was systemically varied, since this also affects breakup time. The sensitivity of a hydrocarbon fuel drop-air mixture to detonate was significantly increased by using additives which alter the chemical energy release rate and by decreasing the initial fuel drop size.