Temperature and convection velocities in two-component liquid droplet until micro-explosion

[Display omitted] •Convection velocities increase severalfold before micro-explosion of used droplets.•Convection velocities and temperatures fields of used droplets remain unsteady.•Effect on convection of thermal, dynamic and geometric factors is significant.•2–3-fold growth of gas temperature increases convection velocity by 50–80% in water.•2–3-fold growth of gas temperature increases convection velocity by 4–5 times in oil. The micro-explosion of slurries and emulsions droplets under heating contribute to a significant increase in efficiency of a large group of promising technologies, in particular, in the production of heat carriers based on flue gases, vapors, and water droplets, in flame and thermal water purification from unspecified impurities, and in environmentally friendly combustion of fuels, including those prepared from abundant industrial waste containing sewage and service water. In this paper, we study the consistent patterns of partial fragmentation and micro-explosion of two-liquid droplets consisting of a flammable (oil) and non-flammable (water) liquids. The consequences of rapid convective heat exchange have been researched between a droplet and heated air flow. The Planar Laser Induced Fluorescence optical technique was used to measure the droplet temperature field, and the Micro Particle Image Velocimetry – the convection velocities in the droplet. We focus on the structure of convective flows, centers of vortex formation, velocities, and the influence on the temperature in different droplet sections (especially, at the inter-component interface, whose destruction triggers the micro-explosive breakup of droplets). The tracer particles were used to simultaneously measure the convection velocities in the flammable and non-flammable liquids making up two droplet parts. We have determined the velocities and temperatures near the inter-component interface sufficient for micro-explosion of a rapidly heated two-liquid droplet. The experimental findings provide a deeper insight into the mechanism and main stages of inter-component interface destruction in heated heterogeneous droplets.