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

CFD Prediction of Partload CO Emissions Using a Two-Timescale Combustion Model

[+] Author and Article Information
Bernhard Wegner1

Energy Sector, Siemens AG, 45478 Mülheim/Ruhr, Germanybernhard.wegner@siemens.com

Uwe Gruschka, Werner Krebs

Energy Sector, Siemens AG, 45478 Mülheim/Ruhr, Germany

Y. Egorov, H. Forkel, J. Ferreira

 ANSYS Germany, 83624 Otterfing, Germany

Kai Aschmoneit

EKT, Darmstadt University of Technology, 64287 Darmstadt, Germany


Corresponding author.

J. Eng. Gas Turbines Power 133(7), 071502 (Mar 17, 2011) (7 pages) doi:10.1115/1.4002021 History: Received April 21, 2010; Revised May 16, 2010; Published March 17, 2011; Online March 17, 2011

Today’s and future electric power generation is characterized by a large diversification using all kind of sources, including renewables resulting in noncoherent fluctuations of power supply and power usage. In this context, gas turbines offer a high operational flexibility and a good turn down ratio. In order to guide the design and down select promising solutions for improving partload emissions, a new combustion model based on the assumption of two separate timescales for the fast premixed flame stabilization and the slow post flame burnout zone is developed within the commercial computational fluid dynamics (CFD) code ANSYS CFX. This model enables the prediction of CO emissions generally limiting the turn down ratio of gas turbines equipped with modern low NOx combustion systems. The model is explained and validated at lab scale conditions. Finally, the application of the model for a full scale analysis of a gas turbine combustion system is demonstrated.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 2

Species and temperature profiles of a premix flame

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Figure 3

YCO profiles obtained from the reaction progress c∗YCO,ff, the transport Eqs. 9,11 by setting cff=0.99

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Figure 4

Sketch of burner and combustor of the atmospheric rig (8)

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Figure 5

Aeordynamic boundary conditions selected at the burner inlet–color coded is the mixture fraction

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Figure 6

Thermal boundary conditions for the atmospheric test rig

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Figure 7

Reference planes used for model validation

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Figure 8

Temperature distribution for the standard setup and the optimized parameter set; z denotes coordinate along lines presented in Fig. 7

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Figure 9

CO prediction for the atmospheric combustor rig—using the BVM, the TSS model, and the chemical equilibrium assumption; z denotes coordinate along lines presented in Fig. 7

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Figure 11

Comparison of calculated and measured CO emissions versus primary zone temperature (all data are nondimensional)

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Figure 12

Scatter plot of CO versus equivalence ratio on the combustor outlet plane

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Figure 13

Flame surface based on an isosurface of reaction progress c=0.98 colored with equivalence ratio

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Figure 14

Timescale of postflame CO oxidation as a function of equivalence ratio obtained from laminar 1D premixed flames using detailed kinetics

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Figure 1

Sketch of CO emission as function of adiabatic flame temperature

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Figure 10

Calculated nondimensional CO emissions as function of the Zimont factor A




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