THEORY OF NON-STEADY STATE DROPLET COMBUSTION.

The method of matched asymptotic expansions is applied to the analysis of nonsteady state combustion of liquid fuel droplets. It is shown that perturbations due to the unsteady outer region increase the burning rate and reduce the droplet lifetime. Flame trajectories calculated from uniformly valid composite expansions show that (i) the flame moves away from the droplet then back towards it, (ii) the ratio of flame-to-droplet radius increases continually, and (iii) flame extinction occurs after the droplet vanishes. These results contradict the quasi-steady state theory of droplet combustion, but they agree with observed droplet behavior.