Effect of ultrasonic emulsification on the combustion of foamed emulsions

- Foamed emulsion is a perspective type of fuel on the base of water-saturated hydrocarbons.
- Ultrasonic emulsification favors decrease in the total burning rate of foamed emulsion.
- Decrease in oil drops sizes narrows concentration limits of flame propagation in the foam.
- An important role in the process of flame acceleration belongs to explosive boiling of liquid phase of the foam.

The paper analyzes the combustion process of foamed emulsion on the basis of experimental research and phenomenological representations. The foamed emulsion represents a multiphase system consisting of oxygen bubbles dispersed in the oil-in-water emulsion. The research interest to such combustible systems is determined primarily by the fact that even at significant water content the foamed emulsion preserves its combustibility. This paper is mainly focused on the analysis of emulsion preparation methods (mechanical agitation or ultrasonic emulsification) and their influence on the foamed emulsion combustion. It is obtained that ultrasonic emulsification favors decrease in total burning rate of the foam and narrowing in concentration limits of flame propagation. An important role in flame acceleration in the foam belongs to the processes related with explosive boiling of liquid phase of the foam wherein oil drops could play a role of heterogeneous centers of nucleation for vapor bubbles. It is shown that if ultrasonic emulsification causes decrease in the sizes of oil drops in the emulsion below a certain critical value then the conditions for successive flame acceleration will be degenerated.