Absolute CH concentration measurements in low-pressure methane flames: comparisons with model results

Absolute CH concentration profiles were measured for rich and lean premixed, low-pressure, laminar-flow methane flames, using laser-induced fluorescence calibrated with a Rayleigh scattering technique. Agreement between measured concentrations and GRI-Mech 3.0/Premix model predictions varies with flame stoichiometry: measured and predicted maximum CH concentrations and position agree well for a near-stoichiometric flame, but predicted values are approximately 20% too large for rich flames and too small for the lean flame. The model, constrained by a measured temperature profile, predicts the [CH] peak to be too far from the burner for rich flames and too close for the lean flame. Measured OH concentrations give good agreement with model results for all flame stoichiometries.