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

Analysis of the Pollutant Formation in the FLOX® Combustion

[+] Author and Article Information
H. Schütz

DLR-German Aerospace Center, Institute of Combustion Technology, Linder Höhe, 51147 Cologne, Germanyharald.schuetz@dlr.de

R. Lückerath

DLR-German Aerospace Center, Institute of Combustion Technology, Pfaffenwaldring 38-40, 70569 Stuttgart, Germanyrainer.lueckerath@dlr.de

T. Kretschmer

DLR-German Aerospace Center,  Institute of Combustion Technology, Linder Höhe, 51147 Cologne, Germany

B. Noll, M. Aigner

DLR-German Aerospace Center,  Institute of Combustion Technology, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

J. Eng. Gas Turbines Power 130(1), 011503 (Jan 09, 2008) (9 pages) doi:10.1115/1.2747266 History: Received January 04, 2007; Revised January 29, 2007; Published January 09, 2008

FLOX®, or flameless combustion is characterized by ultralow NOx emissions. Therefore the potential for its implementation in gas turbine combustors is investigated in recent research activities. The major concern of the present paper is the numerical simulation of flow and combustion in a FLOX®-combustor [Wünning, J. A., and Wünning, J. G., 1997, “Progress in Energy and Combustion Science  ,” 23, pp. 81–94; Patent EP 0463218] at high pressure operating conditions with emphasis on the pollutant formation. FLOX®-combustion is a highly turbulent and high-velocity combustion process, which is strongly dominated by turbulent mixing and chemical nonequilibrium effects. By this means the thermal nitric oxide formation is reduced to a minimum, because even in the nonpremixed case the maximum combustion temperature does not or rather slightly exceeds the adiabatic flame temperature of the global mixture due to almost perfectly mixed reactants prior to combustion. In a turbulent flow, the key aspects of a combustion model are twofold: (i) chemistry and (ii) turbulence/chemistry interaction. In the FLOX®-combustion we find that both physical mechanisms are of equal importance. Throughout our simulations we use the complex finite rate chemistry scheme GRI3.0 for methane and a simple partially stirred reactor (PaSR) model to account for the turbulence effect on the combustion. The computational results agree well with experimental data obtained in DLR test facilities. For a pressure level of 20 bar, a burner load of 417 kW and an air to fuel ratio of λ=2.16 computational results are presented and compared with experimental data.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

CO and NO molar fraction distribution and streamline representation of the flow on longitudinal slice through nozzle and combustor axis for λ=2.16. Note: the molar fraction is related to dry gas and 15% O2 concentration at the combustor exit (see Table 2).

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Figure 2

Inhomogeneous methane distribution at burner nozzle exit, CH4min=0.3%, CH4max=17.7% -turbulent velocity profile at the nozzle exit, vmax≈187m∕s, vmean≈173m∕s. Note: Maximum speed of v≈197m∕s is reached about 3.7mm downstream of the nozzle exit-streamlines indicating recirculation around the jet.

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Figure 3

Schematic of the experimental/computational setup

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Figure 4

Characteristic chemistry time over the elementary reactions of the GRI3.0 reaction scheme. Red colored line: nonordered; black colored line: ordered chemical reactions.

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Figure 5

Characteristic chemistry time (lower half) and turbulent mixing time (upper half) in the combustion zone on a longitudinal slice through the burner nozzle and combustor axis

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Figure 6

Damköhler-# (lower half) and heat release rate (upper half) in the combustion zone on a longitudinal slice through the burner nozzle and combustor axis

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Figure 7

OH molar fraction distribution on slice plane 2 (see Fig. 3) for λ=2.16. Comparison-Simulation: GRI3.0 quasilaminar/Experiment: LIF.

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Figure 8

OH molar fraction distribution on slice plane 2 (see Fig. 3) for λ=2.16. Comparison-Simulation: GRI3.0+PaSR-model (Cmix=0.002)/Experiment: LIF.

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Figure 9

Temperature distribution on slice plane 3 (see Fig. 3) for λ=2.16-Comparison-Simulation: GRI3.0+PaSR/Experiment: OH-LIF

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Figure 10

OH (upper half) production rate and heat release rate (lower half) in the combustion zone on a longitudinal slice through the burner nozzle and combustor axis

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Figure 11

OH (upper half) and CO (lower half) production rate in the combustion zone on a longitudinal slice through the burner nozzle and combustor axis. 1, 2 analysis points.

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Figure 12

Relative amount of CO production plotted over the elementary reactions of the GRI3.0 mechanism at analysis point 1 (left) and analysis point 2 (right)

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Figure 13

OH (upper half) and NO (lower half) production rate in the combustion zone on a longitudinal slice through burner nozzle and combustor axis. 1, 2, 3 analysis points.

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Figure 14

Relative amount of NO production plotted over the elementary reactions of the GRI3.0 mechanism at analysis point 1 and 2. Red: Zeldovich, Green: N2O, Black: NO2, Blue: Fenimore.

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Figure 15

Graphical representation of Eq. (12)

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