Diode laser sensor for measurements of CO, CO2, and CH4 in combustion flows

A diode laser sensor has been applied to monitor CO, CO2, and CH4 in combustion gases with absorption spectroscopy and fast extraction-sampling techniques. Survey spectra of the CO 3v band (R branch) and the 2v(1) + 2v(2)(0) + v(3) CO2 band (R branch) near 6350 cm(-1) and H2O lines from the v(1) + 2v(2) and 2v(2) + v(3) bands in the spectral region from 6345 to 6660 cm(-1) were recorded and compared with calculated spectra (from the HITRAN 96 database) to select optimum transitions for species detection. Species concentrations above a laminar, premixed, methane-air flame were determined from measured absorption in a fast-flow multipass absorption cell containing probe-sampled combustion gases; good agreement was found with calculated chemical equilibrium values. (C) 1997 Optical Society of America.