Basic aspects of OH(A), CH(A), and C2(d) chemiluminescence in the reaction zone of laminar methane-air premixed flames

Detailed spatial intensity profiles of OH(A), CH(A), and C2(d) chemiluminescence in the reaction zone were revealed in “two-dimensional” laminar premixed flames (ϕ=0.85-1.5) using spatially resolved emission measurements with a resolution-enhanced Cassegrain-type optical probe. A numerical simulation of one-dimensional laminar premixed flames using the PREMIX code, with GRI-Mech 3.0 incorporating with reaction and quenching kinetics for OH(A), CH(A), and C2(d), was compared with the experimental result. The measured and simulated profiles showed reasonable agreement in shape, peak location, emission zone thickness, and peak-intensity variation in fuel-lean and stoichiometric flames. We found disagreement between the experimental and numerical results under fuel-rich conditions, which likely resulted from incomplete C2(d) chemistry used in the present study. Stoichiometry dependence of chemiluminescence peak-intensity ratio, OH(A)/CH(A), observed experimentally was clearly supported by the simulated result.