Comparative study of the influence of CO2 and H2O on the chemical structure of lean and rich methane-air flames at atmospheric pressure

Abstract

A comparative study of the influence of CO2 and H2O on both lean and rich CH4-air laminar flames is performed. Six premixed flames are stabilized on a flat flame burner at atmospheric pressure: lean (with the equivalence ratio maintained constant at ϕ = 0.7) and rich (with the equivalence ratio maintained constant at ϕ = 1.4) CH4-air, CH4-CO2-air, and CH4-H2O-air flames. These flames are studied experimentally and numerically. The [CO2]/[CH4] and [H2O]/[CH4] ratios are kept equal to 0.4 for both flames series. Species mole fraction profiles are measured by gas chromatography and Fourier transform infrared spectroscopy analyses of gas samples withdrawn along the vertical axis by a quartz microprobe. Flames structures are computed by using the ChemkinII/Premix code. Four detailed combustion mechanisms are used to calculate the laminar flame velocities and species mole fraction profiles: GRI-Mech 3.0, Dagaut, UCSD, and GDFkin®3.0.