Numerical studies on flame structure of two interactive droplets in spray

The vaporization characteristics and flame structures of two equal-sized interactive droplets in reactive flows are investigated by means of a body-fitted computation. By fixing the Reynolds number and droplet spacing, and varying the ambient temperature as well as equivalence ratio, the numerical results illustrate that, with increasing the ambient temperature, the flame exhibits the wake flame, transition flame, and envelope flame sequentially. For the wake or transition flame, a triple-flame structure develops. However, a double-flame is established when the envelope flame forms. On the other hand, the influence of increasing the ambient equivalence ratio on the vaporization rate and flame just as the ambient temperature increases. It was found that the droplet combustion will be initiated earlier in the presence of reactive environment, while the flame moves upstream. As the ambient equivalence ratio is as high as 0.2, the effect of ambient fuel vapor becomes significant and the fuel-lean premixed flame can extends to the far-field. In general, the vaporization rate of the trailing droplet is lower than that of the leading one. However, an inverse behavior on vaporization appears as the transition flame takes place.