A Comparison of CH4/NO/02and CH4/N20 Flames by LIF Diagnostics and Chemical Kinetic Modeling

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Abstract
Laser-induced fluorescence (LIF) diagnostics and chemical kinetic modeling have been performed on two nitrogen-containing flames al low pressure: CH4/NO/02 and CH4/N20. Relative concentration profiles of Ihe species OH, CH, NO, NH, and CN wereoblained by LIF above a premixed, laminar, flat-flame burner at a pressure of 63Torr. The OH, NH, and CN profiles were converted to absolute concentrations by absorption speclroscopy. Temperature profiles were obtained by analysis of OH LIF excitation spectra above the burner, and by thermocouple measurements of the burner surface. These measured temperatures were used as input to the Sandia Chemkin/Premix flame modeling code. The comparison of measured species relative concentration profiles with model predictions is used to pinpoint areas of uncertainty in the mechanisms and rate parameters in use for the modeling of nitrogen chemistry in combustion. Comparisons are also included for previous work on CH4/N02/02 flames.