Extinction and structure of unequal lean premixed flames formed in opposite turbulent flow

Extinction and structure of unequal lean premixed flames formed in opposite turbulent flow was studied experimentally using propane/air and methane/air mixtures. The extinction phenomena interacting lean and ultra lean methane/air turbulent premixed flame could be divided into two distinct regimes depending on the fuel concentrations of the ultra lean mixture. When the fuel concentration of the ultra lean mixture was below 4%, the effect of ultra lean mixture on the extinction was weak, the extinction that occurred under the total fuel concentration was not uniform value. On the other hand, when the ultra lean mixture was above ≈ 4%, both flames strongly interact; the sum of the both fuel concentrations keeps nearly constant at the extinction. The ultra lean mixture could be reacting due to molecular level diffusion of heat and mass. The ultra lean methane-air premixed gas interacted with lean premixed gas and the stable region extends to the lower fuel concentration zone. However, for the propane/air flame, the extinction limits depended on the more concentrated burner condition regardless of the less concentrated burner condition. In this case, the flame interaction of upper and lower flame did not affect the flame extinction. Original is an abstract.