The Breakup of RP-2 Liquid Fuel Droplets in a Detonation Field

Experimentally obtained droplet breakup patterns are presented for RP-2 liquid fuel droplets in the environment behind a detonation wave. To the best of our knowledge, this data is the first of its kind to examine the fundamental interactions between detonation waves and an individual fuel droplet. The experiments presented here are expected to support the ongoing effort of creating accurate models of droplet breakup in a variety of environments, which in turn will lead to enhanced predictions of rotating detonation engine performance, improved safety considerations for facilities operating in hazardous conditions, and new knowledge in energetics, hypersonics, and explosion dynamics research. Detonations were produced inside a detonation tube using a gaseous mixture of hydrogen and oxygen while the fuel droplets were allowed to fall into the line-of-sight of a pair of windows used for high-speed shadowgraphy. Baseline conditions for the detonation include an initial temperature of 293 K, an initial pressure of 760 torr, and an equivalence ratio of 0.7. Conditions produced by the detonation wave include an estimated Weber number of 150,000 and a Mach number of 0.84 for droplets with an average diameter of 2.30 mm. Comparisons are made between the observed deformation of the droplet and the results of other experiments from the literature. Comparisons of droplet deformation are also made to predictions from the Taylor Analogy Breakup model. Attempts are made to characterize the effects of different parameters, including initial pressure, equivalence ratio, the introduction of diluents to the gaseous mixture, and droplet diameter. Furthermore, the breakup of water droplets in the same baseline conditions and the breakup of fuel droplets in a methane-oxygen detonation environment are also presented for comparison