Effect of micro-explosion of biodiesel and ethanol droplets on evaporation: A three-stage mixed fuel droplet evaporation model

Abstract

The ejection and micro-explosion of a mixed fuel droplet group affected the evaporation and combustion rate of fuel. In order to explore the evaporation, micro-explosion, and interaction rules of the biodiesel and ethanol droplet group with different component proportions and volumes during heating, a set of multiparameter tubular furnace experimental equipment was designed. By setting the experimental parameters of the tubular furnace, the heating sequence pictures of the biodiesel and ethanol droplet group were obtained by high-speed photography, and the droplet parameters were analyzed and processed by Image-Proplus. In the experiment, not only the phenomena of ejection, micro-explosion, and white fog but also the interactions of collision, interweaving, and fusion of droplets were observed, which affected the micro-explosion and evaporation of individual droplets in the droplet group. When the ratio of biodiesel to ethanol was 40:60 (40% biodiesel and 60% ethanol), the micro-explosion intensity was the highest. For the same type of droplet, the higher the micro-explosion intensity, the higher the evaporation rate, and the super micro-explosion made the droplet evaporate almost instantaneously. The modified equation for calculating the micro-explosion intensity was established, and the micro-explosion intensity of the mixed droplet was calculated. By integrating the droplet micro-explosion intensity equation and evaporation equation, a three-stage evaporation model of the mixed droplet was established, and the average evaporation rate of the second-stage BD30E70 (30% biodiesel and 70% ethanol) droplet was nearly 28 times the first stage, which was nearly 32 times the third stage.