Breakup and explosion of droplets of two immiscible fluids and emulsions

Abstract

Abstract The explosive breakup of liquid, emulsion, and slurry droplets enables a several-fold increase of their evaporation surface area. This effect reduces the energy and time required for fuel heating, evaporation, and ignition. It also lowers anthropogenic emissions and provides fuller fuel burnout. However, the conditions and possible regimes of explosive breakup of liquid, slurry and emulsion droplets have yet to be found. Knowledge on such processes is necessary for improving the performance of fuel ignition and combustion as well as thermal and flame liquid treatment. Component mixing and storage may differ. The experiments in this research compare the explosive breakup of heated droplets of two immiscible fluids (e.g., water/flammable liquid) and water-in-diesel (W/D) emulsions stabilized by monoethanolamides of fatty acids. The experiments used the most widespread combustible liquids and fuels applied in the industry: kerosene, gasoline, diesel, petroleum oils, as well as petroleum. The most valuable findings are as follows: the experimentally established threshold conditions of droplet breakup, two regimes of droplet fragmentation, four outcomes of the parent droplet heating, as well as the number and size of the resulting fuel aerosol droplets. Another important experimental result consists in determining the maximum droplet heating times to explosive breakup corresponding to the equal proportions of water and flammable liquid (or fuel) in a droplet. If one of the components significantly exceeded the other one in proportion, the shortest heating time to droplet breakup was observed. The focus was on comparing the characteristics and parameters of droplets of W/D emulsions and droplets of two immiscible fluids. W/D emulsion droplets break up to form a fine aerosol, whereas two-component droplets show two breakup regimes: puffing and micro-explosion. The results obtained are important for the development of high-potential gas-vapor-droplet technologies to intensify the evaporation of additives and the ignition of fuel compositions.