Unsteady Combustion of the Heptane-in-Water Emulsion Foamed with Hydrogen–Oxygen Mixture

Abstract

This research paper numerically studies how hydrocarbon additives affect hydrogen combustion in the process of complex fuel burning on the example of the combustible foam representing the heptane-in-water emulsion foamed with a hydrogen–oxygen mixture. It is demonstrated that the two-phase hydrodynamic model with an account of foam structure and chemical kinetics reproduces quite accurately, at least at the qualitative level, the experimentally observed features of foamed emulsion combustion. Due to this, it is concluded that a proposed model can be fruitfully used for the interpretation of the combustion features observed in such a complex combined fuel. Based on the obtained numerical data, it is found that there are two main possibilities related to the hydrogen–hydrocarbon chemistry interactions. In the case of near-stoichiometric, hydrocarbons act mainly as an inhibitor of hydrogen combustion; however, for lean hydrogen–oxygen mixtures, flame propagation is determined by the joint hydrocarbon and hydrogen oxidation kinetics. Herewith, the hydrocarbon burns together with the hydrogen inside the flame front in the case of slow combustion, while in the case of high-speed combustion, hydrogen oxidation kinetics becomes predominant, and hydrocarbons evaporate and burn behind the flame front, causing a lesser effect on the flame dynamics.

Keywords

• complex fuel
• foamed emulsion
• non-stationary combustion
• flame acceleration
• combustion kinetics
• numerical analysis