  The gasification of multicomponent fuel drops is relevant in various
energy-related technologies. An interesting phenomenon associated with this
process is the self-induced explosion of the drop, producing a multitude of
smaller secondary droplets, which promotes overall fuel atomization and,
consequently, improves the combustion efficiency and reduces emissions of
liquid-fueled engines. Here, we study a unique explosive gasification process
of a tricomponent droplet consisting of water, ethanol, and oil ("ouzo"), by
high-speed monitoring of the entire gasification event taking place in the
well-controlled, levitated Leidenfrost state over a superheated plate. It is
observed that the preferential evaporation of the most volatile component,
ethanol, triggers nucleation of the oil microdroplets/nanodroplets in the
remaining drop, which, consequently, becomes an opaque oil-in-water
microemulsion. The tiny oil droplets subsequently coalesce into a large one,
which, in turn, wraps around the remnant water. Because of the encapsulating
oil layer, the droplet can no longer produce enough vapor for its levitation,
and, thus, falls and contacts the superheated surface. The direct thermal
contact leads to vapor bubble formation inside the drop and consequently drop
explosion in the final stage.
