Effect of micro-explosion and puffing on combustion interactions of multi-component fuel droplet array during flame spread

Abstract

Micro-explosion is a potential scheme to increase the combustion rate of engine spray and reduce emissions. The present study investigates the effects of micro-explosion and puffing on the combustion interaction of multi-component fuel droplet array using a magnified high-speed backlit illumination technique. The mechanisms of micro-explosion and puffing in droplet array combustion were proposed. The results indicate that droplet array combustion primarily consists of two droplets burning in the same flame, three droplets burning in the same flame, and independent flame combustion. Three droplets burning in the same flame lasts the longest at droplet spacings of 2 and 3, accounting for 97.14 % and 72.06 % of the total combustion time, respectively. The total combustion duration of the droplet array is shortened by 34.1 % and 40.3 % at droplet spacings of 2 and 3 compared to the theoretical combustion time. However, the total combustion duration of the droplet array is 1.9 % and 7.4 % longer than the theoretical value at droplet spacings of 4 and 5. Most importantly, the interaction factor first increases and then decreases with increasing droplet spacing. The third droplet has the smallest interaction factor. This is mainly determined by the combined effects of hypoxia, flame heating, and vapor cooling.