Investigation of single drop evaporation characteristics of two-component fatty acid methyl esters at high temperature

To investigate the evaporation and micro-explosion characteristics of blended droplets at 773 K and 973 K ambient temperatures, methyl palmitate (MP) and methyl oleate (MO) are selected as typical fuels in this study. The MP concentration ranges from 10 % to 50 % to investigate the micro-explosion characteristics of the blended droplets. No micro-explosion that occurs during its whole lifetime when MP is pure, but the micro-explosion can be observed in all blended droplets. Interestingly, the micro-explosion intensity, average evaporation rate, microexplosion delay time, and evaporation duration of droplet all reach the optimum value when the MP concentration is 20 % at 773 K and 973 K. The micro-explosion can be divided into three categories by intensity, namely strong micro-explosion, weak micro-explosion, and puffing. The strong micro-explosions occur at 973 K when the concentration is 20 %. It can be inferred that micro-explosion is the critical factor in shortening the evaporation duration. Cleavage reaction that occurs in the MO produced bubbles to increase the micro-exploration intensity. Meanwhile, the polymerization that carried out in the MO inhibits the evaporation with producing solid. It is observed experimentally that the residual volume caused by the polymerization decreases with increasing MP concentration. Furthermore, a new relationship is established in terms of the evaporation rate, micro-explosion intensity and ambient temperature by numerical fitting.

Automated summary

In this study, the evaporation and micro-explosion characteristics of blended droplets at different temperatures were investigated using methyl palmitate (MP) and methyl oleate (MO) as fuels. When MP was pure, no micro-explosion occurred, but it was observed in all blended droplets. The optimal micro-explosion intensity, evaporation rate, micro-explosion delay time, and evaporation duration were all achieved when the MP concentration was 20% at both 773 K and 973 K. Micro-explosions were categorized into strong micro-explosions, weak micro-explosions, and puffing. Cleavage reaction in MO increased the intensity of micro-explosions, while polymerization inhibited evaporation. The residual volume caused by polymerization decreased with increasing MP concentration. A new relationship between evaporation rate, micro-explosion intensity, and ambient temperature was established through numerical fitting.