Highly turbulent counterflow premixed flames: effects of the composition of the hot product stream

摘要

Virtually all stabilization methods (swirl, bluff body, pilot flame, etc.) of highly turbulent flames ultimately result in the mixing of the reactants with hot products of combustion. Whereas the stabilizing effect of enthalpy of the combustion products has been long recognized, the role played by the chemical composition of the hot gases is typically disregarded. We recently developed a counterflow burner capable of stabilizing highly turbulent non-premixed and premixed flames. We here employ this system to pinpoint the effects of the hot product stoichiometry on the structure of turbulent premixed flames under conditions of both stable burning and local extinction. To that end, a turbulent jet of lean-to-stoichiometric premixed reactants at a turbulent Reynolds number on the order of 1,000 is opposed to a stream of hot products of combustion that were generated in a preburner. The structure of the turbulent flame oxidation layer is analyzed using simultaneous CO LIF and OH LIF measurements. The local CO＋OH reaction rate appears to be more readily quenched by products of combustion from stoichiometric flames, whereas the flame stability is found to be enhanced by products of combustion from lean flames.