Tri-brachial flames around two interactive droplets in flows with fuel vapor

The flame structures around two equal-sized and interactive fuel droplets immersed in high-temperature convective flows are examined. When the flame is sustained between the two droplets while the flow is pure air, an anchor-shape flame structure, namely the tri-brachial flame, is clearly observed. When far-field temperature or ambient equivalence ratio is increased, the flame propagates upstream and the fuel-lean premixed flame withers. However, if the ambient equivalence ratio is high to some extent such as 0.3, two wings of the flame, viz. the fuel-lean and the fuel-rich premixed flames, extend outward from the stoichiometric point. Once the flame encircles the leading droplet, it evolves into a double-flame structure consisting of a front premixed flame and an aft diffusion flame. Accordingly, the impact of the preceding two environmental factors on the droplets' flame structures is outlined.