Experimental research into collisions of homogeneous and multi-component liquid droplets

Abstract

This paper presents the results of experiments recording the collision characteristics of droplets of various liquids with each other in a gas medium. We use water-based compositions typical of fuel, petrochemical, and heat and mass transfer technologies: solutions, emulsions, slurries, immiscible two- and multi-component liquids. The study discusses how droplet dimensions, velocities, impact angles, component concentrations and properties affect interaction regime as well as the number and size of child droplets. Threshold conditions are analyzed for the occurrence of bouncing, separation, coalescence, and disruption of droplets. Basic hypotheses are formulated as to why the collision characteristics of single-component droplets in a gas differ from those of highly heterogeneous multi-component ones. We use the interaction regime maps based on the dimensionless processing of experimental results through angular and linear impact parameters, Weber, Reynolds, Ohnesorge, and capillary numbers. Collisions can provide major atomization, in which the relative surface area of the liquid increases 2–6 times. The values of these parameters are influenced by droplet velocity and size, component type (solid or liquid), concentration and properties (density, viscosity, surface tension), as well as temperature and role (projectile or target) of homogeneous and multi-component droplets.