Heating, evaporation, fragmentation, and breakup of multi-component liquid droplets when heated in air flow

[Display omitted] •Dispersion behaviors of two- and multi-component droplets differ negligibly.•A second component in a droplet is a necessary condition of explosive breakup.•Two dispersion modes of multi-component droplets are puffing and micro-explosion.•The evaporation surface area may increase by a factor of 9–35 during fragmentation.•Using different parameters, one can vary explosive breakup times 3–5-fold. Current technologies of thermal and flame liquid treatment involve high energy consumption, repeated supply of untreated liquid to the chamber, long-term heating and additive evaporation, hence quite low efficiency. These aspects are the main reason why high-temperature evaporation and burnout of impurities has limited technological implementation. The efficiency of such technologies may be improved by means of explosive breakup of untreated droplets in heating chambers. As a result, one parent droplet breaks up to form several dozens to several hundreds of the so-called child-droplets. The development of such technologies requires fundamental understanding of heating, evaporation, boiling, and explosive breakup of one-, two-, and multi-component droplets. The same processes can be used to improve the environmental and energy performance indicators of burning liquid, emulsion, and slurry fuels in combustion chambers of power plants and internal combustion engines. In this paper, we present the experimental research into the main heat and mass transfer processes occurring during the heating, evaporation, boiling, and explosive breakup of two- and multi-component droplets in a heated air flow. We identify the principal differences of two dispersion behaviors – puffing and micro-explosion – and indicate the conditions, in which this or that behavior dominates. There is also a transient parameter domain, in which both behaviors can occur. The curves are plotted showing droplet heating times until explosive breakup versus temperature, component concentration, and droplet radii. Finally, we single out the conditions for fragmentation and atomization of two-, three-, and multi-component droplets.