On the consumption of fuel pockets via inwardly propagating flames

The extinction mechanisms of fuel pockets and the formation of unreacted residue fuels through flame-vortex interaction in turbulent flames were investigated via a computational study of inwardly propagating spherical flames (IPF) in lean and rich hydrogen/air mixtures. Results obtained assuming quasi-steady propagation show that though extinction of the Le < 1, lean flame is stretch induced and is accompanied by substantial amount of unconsumed reactants, extinction of the Le > 1, rich flame is induced by the depletion of the deficient reactant ahead of the flame and yields practically no unconsumed reactant. Results obtained for the more realistic, transient propagation show that flame propagation can actually persist almost to the center for both the lean and rich flames, and, as such, all deficient reactants are consumed upon flame extinction. Extending these results to include hydrocarbon flames within the context of stretch and nonequidiffusion, it is suggested that the formation of unreacted fuel pockets via flame-vortex interaction is not expected to be a matter of serious concern because of the potential of complete consumption of the deficient reactant upon extinction of the IPF.