DOES INTERNAL CONVECTION PROMOTE MICRO-EXPLOSION OF W/O EMULSION DROPLETS?

Abstract

W/O emulsions are considered as a beneficial alternative to the use of fossil hydrocarbon fuels and not treated vegetable oils. The presence of a dispersed phase composed of water allows to reduce pollutant emissions and also increases combustion efficiency because of the so-called micro-explosion phenomenon. This micro-explosion has a strong stochastic behavior, and its realization depends on several parameters such as water droplet size distribution and motion during heating. This paper aims to provide a better understanding of the impact of the water droplet behavior on the atomization rate. PLIF technique is used to visualize and track the motion of the water droplets dispersed inside heated emulsion drops. Natural convection of the water droplets is observed, and its impact on coalescence and atomization rate is investigated. Emulsion with small size distributions and high droplet velocity tends to show a low or nonexistent micro-explosion rate, while coarse emulsions show an important coalescence rate, resulting in a high micro-explosion occurrence. Finally, a dimensionless indicator measuring dispersed-phase motion intensity is proposed.