Effects of CH4 Content on NO Formation in One-Dimensional Adiabatic Flames Investigated by Saturated Laser-Induced Fluorescence and CHEMKIN Modeling

Experiments applying saturated laser-induced fluorescence (LSF) technology were performed focusing on the influence of equivalence ratio, syngas mixture contents, on NO formation in H2/CO/CH4/CO2/N2/O2 premixed flat flames supplied by a heat flux burner. Experimental data were extracted to validate calculation by CHEMKIN software. Both experiments and CHEMKIN calculation draw one conclusion that NO mole fraction in CH4-air flame peaks at stoichiometric and φ1.3, due to thermal NO and prompt NO routes. All mechanisms applied can well-predict the NO mole fraction at the fuel lean side but failed at the fuel rich side. NO mole fraction in syngas flame is propotional to CH4 ratio as shown in the experimental data, but all the mechanisms failed to predict it with some even having a wrong tendency. A rate of NO production and sensitivity analysis suggests that thermal and prompt NO routes play different roles in each mechanism, and modifications to mechanisms are required to improve NO concnetration predictions at CH4-containing syngas flame