NO EMISSION CHARACTERISTICS OF METHANE AIR DOUBLE FLAME

NO emission characteristics of methane-air Bunsen-type burner flames w ere studied numerically in terms of counterflow flame. The flames have the well-known double flame structure: the rich premixed flame to pro duce CO and H-2 as the main intermediate products and the diffusion fl ame where the intermediate products burn with surrounding air, and the structure can be simulated by using rich counterflow flame with air. The similarity solution was adopted to describe the flow, temperature, and concentration fields and the detailed kinetics calculation was ma de by using C2 chemistry with the all mechanisms leading to NO formati on. including thermal and prompt NO mechanisms. The calculation was ma de as well for thermal mechanism alone, so as to distinguish contribut ion of the respective NO formation mechanisms in total NO production. The emission characteristics were evaluated quantitatively in terms of the emission index, as compared to the normal premixed and pure diffu sion flames. The effects of equivalence ratio and the velocity gradien t on the emission index of these flames were studied.