Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Assessment of Current Chemiluminescence Kinetics Models at Engine Conditions

[+] Author and Article Information
Eric Petersen, Madeleine Kopp, Nicole Donato, Felix Güthe

Department of Mechanical Engineering,  Texas A&M University, College Station, TX Combustion Technology Group, Alstom Power, Baden, Switzerland

J. Eng. Gas Turbines Power 134(5), 051501 (Feb 16, 2012) (7 pages) doi:10.1115/1.4004735 History: Received June 21, 2011; Revised July 09, 2011; Published February 16, 2012; Online February 16, 2012

Chemiluminescence continues to be of interest as a cost-effective optical diagnostic for gas turbine combustor health monitoring. However, most chemical kinetics mechanisms of the chemiluminescence of target species such as OH*, CH*, and CO2 * were developed from atmospheric-pressure data. The present paper presents a study wherein the ability of current kinetics models to predict the chemiluminescence trends at engine pressures was assessed. Shock-tube experiments were performed in highly diluted mixtures of H2 /O2 /Ar at a wide range of pressures to evaluate the ability of a current kinetics model to predict the measured trends. At elevated pressures up to 15 atm, the currently used reaction rate of H + O + M = OH* + M (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. Other important chemiluminescence species include CH* and CO2 *, and separate experiments were performed to assess the validity of existing chemical kinetics mechanisms for both of these species at elevated pressures. A pressure excursion using methane-oxygen mixtures highly diluted in argon was performed up to about 15 atm, and the time histories of CH* and CO2 * were measured over a range of temperatures from about 1700 to 2300 K. It was found that the existing CH* mechanism captured the T and P trends rather well, but the CO2 * mechanism did a poor job of capturing both the temperature and pressure behavior. With respect to the modeling of collider species, it was found that the current OH* model performs well for N2 , but some improvements can be made for CO2 .

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Maximum OH* concentration as a function of temperature at constant pressure and optical settings compared to the work of Petersen [4]. Peak values are normalized to 1498 K and 1.15 atm.

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Figure 2

The normalized, experimentally obtained profile of OH* agrees well with the profile from Petersen [4] at atmospheric pressure. Times have been adjusted to align OH* for comparison of the profile shape rather than the timing.

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Figure 3

Comparison of OH* mechanism and data at three different pressures. The model predictions (lines) significantly over predict the experimental results at elevated pressures.

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Figure 4

Chemiluminescence spectrum pointing out the wavelengths at which CO2 * and CH* were captured

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Figure 5

Representative profiles from stoichiometric methane/oxygen mixtures in 99.1% Ar are compared to model profiles for CO2 * and CH*. Calculations are adjusted in time so that the times of peak concentration coincide with the measured results. (a) CO2 * profiles at P = 1.2 atm. (b) CH* profiles at P = 1.2 atm. (c) CO2 * profiles at P = 14.3 atm. (d) CH* profiles at P = 14.3 atm.

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Figure 6

The product of the CO concentration times the O concentration dictates the overall profile shape of CO2 *. Results here are calculated from the kinetics model (GRI 3.0) for the stoichiometric CH4 -O2 mixture in 99.1% Ar. (a) 2092 K, 1.2 atm and (b) 1641 K, 14.3 atm.

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Figure 7

Peak concentration of CH* is compared to the peak value obtained experimentally at (a) atmospheric and (b) elevated pressures with excellent agreement. (a) 1.3-atm results and (b) 14-atm results.

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Figure 8

Predicted peak concentration of CO2 * is compared to the peak value obtained experimentally. Poor agreement is seen at (a) atmospheric and (b) elevated pressures. (a) 1.3-atm results and (b) 14-atm results.

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Figure 9

Predicted and measured OH* for the nitrogen-based mixture, 2% H2  + 1% O2  + 97% N2 . (a) OH* time histories for 1183 K, 1.2 atm. (b) OH* time histories for 1272 K, 1.1 atm.

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Figure 10

Repeatability of measured OH* for the nitrogen-based mixture, 2% H2  + 1% O2  + 97% N2

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Figure 11

Peak OH* concentration normalized to the result at 1272 K over a range of temperature for the nitrogen-based mixture, 2% H2  + 1% O2  + 97% N2 . Both model and experiment are shown.

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Figure 12

Modeled and measured OH* time history for the mixture containing CO2 : 0.6% H2  + 0.3% O2  + 5% CO2  + 94.1% Ar. Note that the model tends to overpredict slightly the decay rate of OH*.

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Figure 13

Calculated and measured peak OH* concentration for the mixture containing CO2 : 0.6% H2  + 0.3% O2  + 5% CO2  + 94.1% Ar over a range of temperatures. The peak values are normalized to the concentration at 1340 K. Typical error bars are shown on the highest-temperature point.

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Figure 14

Comparison of peak concentration to the normalized area under the entire OH* time history for the nitrogen-based mixture with 97% N2 . Values are normalized to the 1272 K, 1.3-atm results.



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