Secondary atomization of gas-saturated liquid droplets as a result of their collisions and micro-explosion

The paper presents the experimental research findings for secondary atomization of gas-saturated (filled with CO2 bubbles) water droplets. Experiments were also conducted with water droplets, filled with vapor bubbles as a result of heating them to a near-boiling condition. Two schemes of droplet atomization have been considered: collisions and micro-explosive breakup due to rapid heating. The second scheme was implemented using two-component droplets, formed by adding a liquid combustible component (rapeseed oil - a promising biofuel) to water. A well-tested technique was used to generate a two-component droplet: water at the core with an envelope of rapeseed oil. Using the experimental data, the ratios of liquid surface areas were calculated before and after implementing each of the secondary atomization schemes. Additionally, interaction regime maps of droplets were produced, specifying the conditions of their rapid disruption. It has been shown that the micro-explosive atomization of droplets with CO2 bubbles occurs with a shorter delay, and the ratios of child droplet surface areas are higher than those of parent droplets without CO2 bubbles. Optimal conditions, defined for using two of the investigated methods of secondary atomization of droplets, make it possible to increase the liquid surface area more than tenfold. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.