Microexplosions in Multicomponent Fuel Droplets

Certain blends of multicomponent fuel droplets containing compounds with large differences in volatility have a tendency to experience violent combustion, which is known as microexplosions. The preferential evaporation of the more volatile component at the surface of the droplet creates a liquid phase concentration gradient when there is little internal circulation. At high temperatures such as those experienced in combustion, this allows the interior of the droplet to become superheated. It is postulated that when the temperature at the center of the droplet reaches the limit of superheat for the mixture composition at that point, the droplet will microexplode. A computational model is developed to predict conditions under which a multicomponent droplet undergoes microexplosion. Simulations are performed and results are compared with measurements to rationalize the transition between stable, weakly disruptive puffing, and microexplosion modes.