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

Development and Application of an Eight-Step Global Mechanism for CFD and CRN Simulations of Lean-Premixed Combustors

[+] Author and Article Information
Igor V. Novosselov

Energy and Environmental Combustion Laboratory, Department of Mechanical Engineering, University of Washington, P.O. Box 352600, Seattle, WA 98195-2600

Philip C. Malte1

Energy and Environmental Combustion Laboratory, Department of Mechanical Engineering, University of Washington, P.O. Box 352600, Seattle, WA 98195-2600malte@u.washington.edu

1

Corresponding author.

J. Eng. Gas Turbines Power 130(2), 021502 (Jan 22, 2008) (9 pages) doi:10.1115/1.2795787 History: Received April 26, 2007; Revised June 21, 2007; Published January 22, 2008

In this paper, the development of an eight-step global chemical kinetic mechanism for methane oxidation with nitric oxide formation in lean-premixed combustion at elevated pressures is described and applied. In particular, the mechanism has been developed for use in computational fluid dynamics and chemical reactor network simulations of combustion in lean-premixed gas turbine engines. Special attention is focused on the ability of the mechanism to predict NOx and CO exhaust emissions. Applications of the eight-step mechanism are reported in the paper, all for high-pressure, lean-premixed, methane-air (or natural gas-air) combustion. The eight steps of the mechanism are as follows: (1) oxidation of the methane fuel to CO and H2O, (2) oxidation of the CO to CO2, (3) dissociation of the CO2 to CO, (4) flame-NO formation by the Zeldovich and nitrous oxide mechanisms, (5) flame-NO formation by the prompt and NNH mechanisms, (6) postflame-NO formation by equilibrium H-atom attack on equilibrium N2O, (7) postflame-NO formation by equilibrium O-atom attack on equilibrium N2O, and (8) postflame Zeldovich NO formation by equilibrium O-atom attack on N2.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 6

CFD results for NO in comparison to measurements for the bluff body combustor Calculations of Leonard and Stegmaier NOx also plotted.

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Figure 7

Comparison of modeled and measured NOx for the engine test rig combustor. NOx emission is normalized by test rig emission for the neutral pilot. At neutral, the pilot has the same phi as the main premixer.

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Figure 1

CFD solutions for the generic, can-type, lean-premixed, gas turbine combustor. Upper, forward section of combustor shown. Flow is from left to right. Injectors are at the left side. Pilot injector is shown on the centerline. Weak pilot case: 50% of neutral pilot. The main premixer injector is located above the centerline.

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Figure 2

Comparison of R5 by a global rate expression of Table 3 (y axis) versus rates computed by GRI 3.0 (x axis)

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Figure 3

View of the bluff body combustor from the exit plane. Shown is the gas sampling probe.

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Figure 4

CFD solutions for the bluff body combustor: methane fuel, 0.59 premixer phi, 14.3atm pressure, and 678K inlet air temperature.

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Figure 5

CFD results for CO in comparison to measurements for the bluff body combustor

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