Combustion of heptane-in-water emulsion foamed with hydrogen-oxygen mixture

One of the perspective types of combined fuels is the oil-in-water emulsion foamed with the hydrogen-oxygen mixture. In this paper, the process of combustion of such a system obtained via hydrogen-oxygen mixture bubbling through the heptane-in-water emulsion is considered experimentally for the first time. The main goal of this paper is to study different regimes of foamed emulsion combustion at varying composition of hydrogen-oxygen mixture inside bubbles and heptane content in the emulsion. Flame speed is measured with the use of high-speed filming. It is shown that the use of hydrogen allows increasing the speed of flame propagation through the foamed emulsion, and at certain conditions even detonation onset becomes possible. The detonation in the foamed emulsion is determined by the effect of energy focusing during the collapse of gaseous bubbles. When using a lean hydrogen-oxygen mixture, the dependence of the total burning rate of the foamed emulsion on heptane concentration has a maximum. It is found that when using the stoichiometric hydrogen-oxygen mixture, the flame speed decreases monotonically with the increase in heptane concentration. In the case of a weakly reactive compound of the foamed emulsion, the regime of spinning detonation is possible. •New type of fuel – emulsion foamed with hydrogen-oxygen mixture.•Flame acceleration is defined by the phenomenon of flame auto-turbulization.•Detonation in the foam is defined by the cumulative collapse of bubbles.•It is expedient to use heptane as an inhibitor of detonation.•A spinning regime can be realized in weakly detonating compounds.