Nitric oxide formation and reburn in low-pressure methane flames

Absolute NO concentrations are measured in low-pressure methane-oxygen-nitrogen flames of varying stoichiometry, using laser-induced fluorescence. These measurements are combined with previously measured absolute CH radical concentrations to test the chemical mechanism of prompt NO formation and NO reburn. The GRI-Mech 2.11 chemical mechanism underpredicts prompt NO by 35–60%. Increasing the rate coefficient for the CH+N 2 reaction brings the predicted [NO] into agreement with the measurements. Reburn chemistry is studied by seeding NO at concentrations between 0.1% and 3% in rich and lean flames. The model agrees with the observed reduction of NO in a fuel-lean (=0.80) flame and underpredicts NO reburn in a fuel-rich (=1.27) flame. The model predicts significantly more reduction of the peak CH concentration by reburn of seeded NO in the rich flame than is measured.

[1]  J. Jeffries,et al.  Comparing Laser‐Induced Fluorescence Measurements and Computer Models of Low Pressure Flame Chemistry , 1992 .

[2]  Jerry M. Seitzman,et al.  Comparison of NO and OH planar fluorescence temperature measurements in scramjet model flowfields , 1994 .

[3]  Robert J. Kee,et al.  PREMIX :A F ORTRAN Program for Modeling Steady Laminar One-Dimensional Premixed Flames , 1998 .

[4]  J. W. Fleming,et al.  Comparative species concentrations in CH4/O2/Ar flames doped with N2O, NO, and NO2 , 1994 .

[5]  Gregory P Smith,et al.  Pressure and temperature dependence of the reactions of CH with N2 , 1996 .

[6]  M P Lee,et al.  Temperature measurements in gases by use of planar laser-induced fluorescence imaging of NO. , 1993, Applied optics.

[7]  W. Kieffer.  Sixth Symposium (International) on Combustion , 1958 .

[8]  S Svanberg,et al.  Spatially resolved temperature measurements in a flame using laser-excited two-line atomic fluorescence and diode-array detection. , 1983, Optics letters.

[9]  James A. Miller,et al.  Prompt NO: Theoretical prediction of the high‐temperature rate coefficient for CH + N2 → HCN + N , 1997 .

[10]  Jay B. Jeffries,et al.  Laser-induced fluorescence of seeded nitric oxide as a flame thermometer , 1998 .

[11]  James A. Miller,et al.  Mechanism and modeling of nitrogen chemistry in combustion , 1989 .

[12]  R. Hanson,et al.  Laser-induced fluorescence measurements of NO and OH mole fraction in fuel-lean, high-pressure (1–10 atm) methane flames: Fluorescence modeling and experimental validation , 1995 .

[13]  J. Jeffries,et al.  LIF measurements in methane/air flames of radicals important in prompt-NO formation , 1992 .

[14]  N. Laurendeau.  Temperature measurements by light-scattering methods , 1988 .

[15]  James F. Schooley,et al.  Temperature : its measurement and control in science and industry , 1992 .