Cavity ring down spectroscopy of CH, CH2, HCO, and H2CO in a premixed flat flame at both atmospheric and sub-atmospheric pressure

Density distributions of CH, CH2, HCO and H2CO have been measured in a premixed CH4/air flat flame by Cavity Ring Down Spectroscopy (CRDS). At atmospheric pressure problems are encountered due to the narrow spatial distribution of these species. Rotational flame Temperatures have been derived from the spectral line intensities of CH. Additional distributions of the species are recorded in a low-pressure set up at 2x104 Pa. The results at both pressures are compared to modeling calculations using GRI-Mech 2.11 and 3.0 showing a relatively good agreement. Deviations are attributed to the applied reaction mechanisms.