• WHAT'S NEW IN GRI-Mech 2.11
• GETTING THE FILES
• HOW TO CITE GRI-MECH 2.11
• TARGETS
• PERFORMANCE THAT WE KNOW ABOUT

WHAT'S NEW IN GRI-Mech 2.11

Version 2.11 contains the chemistry identical to that of version 1.2 but adds 102 reactions of 17 additional nitrogen-containing species. The parameters of the 175 reactions from version 1.2 were not varied in the course of the Version 2.11 optimization process except for the rate coefficient of the CH + H2O --> H + CH2O reaction, which was found to play an important role in prompt NO formation but to have no effect on the course of the carbon-hydrogen- oxygen chemistry of methane combustion. Version 2.11 is therefore identical to version 1.2 with respect to the carbon-hydrogen-oxygen chemistry of natural gas ignition and flames.

Version 2.11 was not optimized for modeling pure nitrogen- hydrogen-oxygen chemistry or any form of NOx removal process except for reburning.

In the course of developing GRI-Mech 2.11 we learned quite early that optimizing the nitrogen chemistry relevant to natural gas flames and reburning is qualitatively a very different challenge than optimizing the carbon-hydrogen-oxygen chemistry. In the first place, we were able to locate only a much smaller data base of experimental information from which to draw optimization targets. Then, once the modeling process had proceeded far enough that we could examine matches between computed and observed behavior, we found a far higher degree of discord among the matches to targets and other data than we had seen in working with our earlier optimizations of carbon-hydrogen-oxygen chemistry. We therefore have to caution users of GRI-Mech 2.11 to regard it only a preliminary starting point that can not be applied with anything like the degree of confidence that can be attached to the version 1.2 carbon-hydrogen-oxygen chemistry. We do believe that GRI-Mech 2.11 is an improvement for the experiments modeled over previous attempts to describe NOx formation and removal in natural gas flames, for example the 1989 Miller and Bowman mechanism, and are therefore releasing it at this time in the spirit of 'beta testing' our first optimized result and stimulating further experimental study of NOx formation and removal in natural gas flames.

GETTING THE FILES

HOW TO CITE GRI-MECH 2.11

TARGETS

PERFORMANCE THAT WE KNOW ABOUT

Here is a list of the validation checks of Version 2.11 that we have made (measurement uncertainties, when reported by the cited investigators, are indicated):

• Flow Reactors
• Low-Pressure Flames
• Stirred Reactors

Flow Reactors

• Glarborg, P. and Miller, J.A., 'Mechanism and Modeling of Hydrogen Cyanide Oxidation in a Flow Reactor,' Combustion and Flame 99, 475 (1994). Species profiles at the exit of a laminar isothermal flow reactor for temperatures between 900 and 1400 K in two mixtures:
  
  • 318ppm HCN/1710ppm CO/2.4% O2/2.8%H2O mixture (fig 4):
    HCN (optimization target NFR1),
    NO (optimization target NFR2), and
    N2O (optimization target NFR3);
  • 298ppm HCN/1620ppm CO/434ppm NO/2.3% O2/2.6%H2O mixture (fig. 6):
    HCN, NO, and N2O.

Low-Pressure Flames

• Miller, J.A., Branch, M.C., McLean, W.J., Chandler, D.W., Smooke, M.D., and Kee, R.J., 'The Conversion of HCN to NO and N2 in H2-O2-HCN-Ar Flames at Low Pressure,' Twentieth Symposium (International) on Combustion, The Combustion Institute, pp. 673-684, 1984. Species profiles in rich and lean laminar premixed flames at 25 Torr.
  • Rich flame, 28% H2/9% O2/2% HCN/61% Ar, phi=1.5 (fig. 3):
    NO (optimization target NF6),
    CN (optimization target NF7),
    HCN, and
    N2;
  • Lean flame, 24% H2/24% O2/1% HCN/51% Ar, phi=0.5 (fig. 1):
    NO, CN, HCN, and N2.
• Heard, D.E., Jeffries, J.B., Smith, G.P., and Crosley, D.R., 'LIF Measurements in Methane/Air Flames of Radicals Important in Prompt-NO Formation,' Combustion and Flame 88, 137 (1992). NO and relative CH profiles in a slightly rich (phi=1.13) CH4-air flame at 30 Torr.
• Williams, B.A. and Fleming, J.W., 'Comparative Species Concentrations in CH4/O2/Ar Flames Doped with N2O, NO and NO2,' Combustion and Flame 98, 93 (1994). Relative CH (optimization target NF11), CN (optimization target NF12/13), NCO, and NH concentration profiles in 10 Torr stoichiometric CH4-O2-Ar flames doped with NO and N2O.
• Etzkorn, T., Muris, S., Wolfrum, J., Dembny, C., Bockhorn, H., Nelson, P.F., Attia-Shahin, A., and Warnatz, J., 'Destruction and Formation of NO in Low Pressure Stoichiometric CH4/O2 Flames,' Twenty-fourth Symposium (International) on Combustion, The Combustion Institute, pp. 925-932, 1992. NO concentration profile in a stoichiometric 10 Torr CH4-O2 flame with added NO.
• Zabielski, M.F. and Seery, D.J. 'Mechanisms and Reaction Dynamics Related to Methane Combustion,' GRI Report 84/0126, 1984. CH (optimization target NF8), CN (optimization target NF9), and NO (optimization target NF10) mole fraction profiles in a 35 Torr slightly rich CH4-O2-Ar flame with added NO.
• Brown, M.J., and Smith, D.B., 'Aspects of Nitrogen Flame Chemistry Revealed by Burning Velocity Modeling,' Twenty-fifth Symposium (International) on Combustion, The Combustion Institute, pp. 1011-1018 (1994). Laminar flame speeds in premixed flames at 70 torr and 60C. H2/N2O flames, a reanalysis of the data of Gray, P., Holland, S., and Smith, D.B., Combust. Flame 14, 361-374 (1970).
• Sausa, R.C., Anderson, W.R., Dayton, D.C., Faust, C.M., and Howard, S.L., 'Detailed Structure of a Low Pressure, Stoichiometric H2/N2O/Ar Flame,' Combust. Flame 94, 407-425 (1993). Profiles of NO and O2 and NH and OH in a 20 torr 35% H2, 35% N2O, 30% Ar laminar premixed flame.
• Riesel, J.R., Carter, C.D., and Laurendeau, N.M., 'Evaluation of Chemical Kinetics Predictions for NO and OH in Atmospheric Pressure C2H6/O2/N2 Flames,' International Symposium on Transport Phenomena, 1995. NO concentrations in 1 atm. flat premixed ethane-air flames.
• Luque, J., Smith, G.P., and Crosley, D.R., 'Quantitative CH Determinations in Low Pressure Flames,' submitted to the Twenty-sixth Symposium (International) on Combustion, 1996. Absolute CH profile in a 25 torr laminar premixed 0.138 CH4, 0.258 O2, 0.603 N2 flame (phi = 1.07). An NO concentration of 1.8+/-0.6E12 cm-3 was measured at 2 cm, while GRI-Mech 2.11 predicts 1.0E12 cm-3.
• Harrington, J.E., Smith, G.P., Berg, P.A., Noble, A.R., Jeffries, J.B., and Crosley, D.R., 'Evidence for a New NO Production Mechanism in Flames,' submitted to the Twenty-sixth Symposium (International) on Combustion, 1996. Absolute NO profiles in Phi = 1.5 H2-air premixed laminar flames at 38 torr and 78 torr.

Stirred Reactors

• Bartok, W., Engleman, V.S., Goldstein, and del Valle, E.G., 'Basic Kinetic Studies and Modeling of Nitrogen Oxide Formation in Combustion Processes,' AIChE Symposium Series No. 126, Vol. 68, pp. 30-38, 1972. NO mole fraction in a jet stirred reactor for CH4-air at 1 atm, 60-150% stoichiometric air with and without NO added.
• Steele, R.C., Malte, P.C., Nichol, D.G., and Kramlich, J.C., 'NOx and N2O in Lean-Premixed Jet-Stirred Flames,' Combustion and Flame 100, 440 (1995). NO and N2O mole fractions in a lean premixed jet-stirred reactor of CH4-air at 1 atm, phi=0.52-0.62, t=3.2-3.5 ms.