American Flame Research Committee

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Title Optimized Kinetics Mechanism and Calculator for Natural Gas Combustion GRI-Mech 3.0
Creator Smith, Gregory P.; Golden, D. M.; Frenklach, M.; Goldenberg, M.; Moriarty, N.; Bowman, C. T.; Hansen, R. K.; Gardiner, W. C.; Lissianski, V.; Serauskas, Robert V.
Publisher Digitized by J. Willard Marriott Library, University of Utah
Date 1998
Spatial Coverage presented at Maui, Hawaii
Abstract A reliable computer model of natural gas oxidation and pollutant formation requires sound elementary kinetics, successful prediction of basic flame properties, and a means for practical use by engineers without kinetics expertise. We describe the most recent version of an optimized kinetics mechanism for natural gas oxidation and NO formation and reburning. The accompanying on-line GRI-Mech Calculator allows non-experts to represent and solve combustion problems as combinations of well-mixed and plug flow reactors. Mechanism development begins with a critical literature evaluation of the elementary rate processes and parameters. Experimental measurements were selected to represent combustion properties that the mechanism is then optimized to predict. These targets include flame velocities, shock tube ignition delays, and species profiles in shock tubes, flow reactors and low pressure flames. New targets focusing on formaldehyde oxidation, the role of propane in natural gas, and the CH intermediate in prompt NO formation and reburn were added for this version. A rigorous optimization procedure adjusts a group of sensitive rate parameters (within evaluated kinetics error limits) to achieve the best simultaneous fit to the target database. The GRI-Mech Calculator 3.0 is a new on-line user-friendly modeling tool designed to simulate natural gas combustion chemistry scenarios using the GRI-Mech 3.0 mechanism. It provides graphical and numerical outputs of exhaust concentrations, temperatures, and pressures computed from user-selected input conditions, constraints, and reaction times for well-stirred or plug flow reactors. A new feature simulates processes by allowing users to assemble a flow diagram of their own reactor network. The Calculator will be made available on the GRI-Mech Website (and in a PC version). A hands-on demonstration is planned.
Type Text
Format application/pdf
Language eng
Rights This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
Conversion Specifications Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth.
Scanning Technician Cliodhna Davis
ARK ark:/87278/s6db84gn
Setname uu_afrc
ID 10175
Reference URL https://collections.lib.utah.edu/ark:/87278/s6db84gn

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Title Page 5
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OCR Text research literature. Results were updated for the 279 reactions (49 species) in version 2.11. As in prior mechanisms, the pressure dependences of recombination and decomposition rate constants are appropriately parameterized, so wide ranges of temperature (1000-3500K) and pressure (0-20 bar) are accommodated. For GRI-Mech 3.0, propane chemistry was included in a form suitable for describing its role in natural gas combustion. This minimal set includes the reactions of propane and propyl radical only. Acetaldehyde and C H 2 C H O were added as products of C 2 species oxidation. Among the changes based on n ew elementary rate data are revised expressions for H + 0 2 (+M) reactions producing H 0 2 , new results for the C H 3 + 0 2 reaction which is important to methane ignition, and high temperature data on several C H reactions. Acquiring improved rate constant results can help constrain the ranges available to the optimization, and the optimization and target sensitivity analysis themselves can suggest where improved basic kinetics measurements are most needed. A set of 82 experimental measurements was selected from the literature and our previous target and validation lists to represent combustion properties that the mechanism is optimized to predict. These targets include flame velocities, shock tube ignition delays, and species profiles in shock tubes, flow reactors and low pressure flames. N e w targets focusing on formaldehyde oxidation and the C H intermediate in prompt N O formation and reburn were added for the version 3.0 optimization. Shock tube targets on propane-assisted ignition delays of methane were included also. The nitrogen target list was reevaluated and expanded since its first inclusion in the optimization (version 2.11), although the general shortage and lack of overlap of this set remains a problem. Significant revisions have been made on some targets as well, in light of new experimental data showing that methane flame speeds are lower than the 1.2 target values (due to stretch effects), and based on new, more precise measurements of higher prompt N O amounts produced in low pressure flames. These experiments were modeled using the trial mechanism of evaluated rate parameters, with the Chemkin-II set of codes,[4] including sensitivity analysis. For those targets such as ignition delays where direct sensitivity output was not available, repeated computations using 2k and k/2 for each rate constant were made to compute a brute force sensitivity coefficient. Some typical results are shown in the bar graphs of Figure 1 for the experimental targets described in the caption. H+02=0+OH H+CHj(*M) = CH4(+M) OH+CO = H+C02 H+02+H20 = H02+H20 OH+CH3 = CHj(S)+H20 H02+CH3=OH+CH30 HCOHjO = H+CO*H20 H*CH4 = CH,*H2 OH*H02=02«-H20 H+OH+M = H20+M H+CjH4(+M) = CjH^+M) H+02+Nj=H02+N2 -0 - - > . jiB r i 2-0.1 0 0.1 0.2 0.3 0.4 0. CH* 02 = OHCO CH+NO = HCN+O CH+NO = N+HCO CH+NO = H+NCO CH*H2 = H+CHj CHj+NO = H+HNCO OCHj = H+H2+CO HCO+HJOH+CO+HJO H+CH = C+H2 CH+H20 = H+CH20 5 -0 04 -0.02 0 002 0.04 Figure 1. Sensitivity coefficients for some experimental targets: (left) A stoichiometric methane-air flame speed at 5 bar 400K; (right) The ratio of C H with and without 1.2% N O seeded into a stoichiometric 10 torr methane-oxygen-argon flame. 5
Setname uu_afrc
ID 10171
Reference URL https://collections.lib.utah.edu/ark:/87278/s6db84gn/10171