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 fluorescen ce calibrated with a Rayleigh scattering technique. Agreement between measu red concentrations and GRI-Mech 3.0/Premix model predictions varies with fl ame stoichiometry: measured and predicted maximum CH concentrations and pos ition agree well for a near-stoichiometric flame, but predicted values are approximately 20% too large for rich flames and too small for the lean flam e. 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 th e lean flame. Measured OH concentrations give good agreement with model res ults for all flame stoichiometries. (C) 2000 by The Combustion Institute.