LIF measurements and modeling of nitric oxide concentration in atmosphericcounterflow premixed flames

Laser-induced fluorescence (LIF) measurements of NO concentration were obta ined in a series of flat, laminar, premixed counterflow CH4/O-2/N-2, flames at atmospheric pressure with equivalence ratios ranging from 0.65 to 1.5. The counterflow configuration permits measurement of NO concentration profi les in the preheat zone, through the flamefront and into the postflame regi on of premixed flames. NO predictions using the Sandia opposed diffusion fl ame code in conjunction with the GRI reaction mechanism (version 2.11) were compared to the measured NO concentrations. Under lean conditions, remarka ble agreement was found between predictions and measurements; however, this agreement broke dawn in moderately rich flames both with respect to the pe ak NO concentrations and to the relative shape of the NO profiles. Pathway, quantitative reaction path, and sensitivity analyses are used to further a nalyze this behavior and to suggest key reaction rate coefficients that cou ld be responsible for the observed results. (C) 2001 by The Combustion Inst itute.