Evaporation of flammable liquids droplets in an electric discharge

Abstract

Evaporation of a liquid drop under the action of a high-frequency electric discharge is considered. The drops were suspended on a thermocouple and were in air at room temperature. The analysis was carried out under the assumption that the action of the discharge is thermal. It is shown that pure liquid fuel drop (ethanol and diesel fuel) evaporates according to the d2-law. At the same time, the rate of evaporation takes a maximum value depending on the distance to the electrode. Analysis of the rate of drop mass reduction made it possible to estimate the thermal power of the discharge, which also passes through a maximum when the electrode is moved away from the drop. When evaporating emulsion droplets (50%/50% fuel/water) after the heating stage, pulsations of geometric size are observed. The drop size periodically changes near some average value with a certain frequency, which decreases with the time of "evaporation". A physico-mathematical model of droplet heating under the thermal action of a discharge was constructed. The pulsations are explained by the evaporation of water globules inside the emulsion drop, the subsequent increase in the size of the vapor bubbles before the "micro-explosion" of the drop. The loss of emulsion material under the action of an electric discharge occurs mainly due to emissions during microexplosions. That is, the electric discharge leads to the dispersion of emulsions droplets with a high water content, in contrast to individual flammable liquids droplets. A decrease in the water content and the power of the electric discharge leads to an increase in the period of pulsations.