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

Effects of Pilot Fuel and Liner Cooling on the Flame Structure in a Full Scale Swirl-Stabilized Combustion Setup

[+] Author and Article Information
Jens Färber1

Institut für Thermische Strömungsmaschinen, Karlsruhe Institute of Technology—KIT, Kaiserstr. 12, 76128 Karlsruhe, Germanyjens.faerber@kit.edu

Rainer Koch, Hans-Jörg Bauer

Institut für Thermische Strömungsmaschinen, Karlsruhe Institute of Technology—KIT, Kaiserstr. 12, 76128 Karlsruhe, Germany

Matthias Hase, Werner Krebs

 SIEMENS AG Energy Sector, Mellinghofer Str. 55, 45466 Mülheim an der Ruhr, Germany

1

Corresponding author.

J. Eng. Gas Turbines Power 132(9), 091501 (Jun 10, 2010) (7 pages) doi:10.1115/1.4000588 History: Received April 06, 2009; Revised October 19, 2009; Published June 10, 2010; Online June 10, 2010

The flame structure and the limits of operation of a lean premixed swirl flame were experimentally investigated under piloted and nonpiloted conditions. Flame stabilization and blow out limits are discussed with respect to pilot fuel injection and combustor liner cooling for lean operating conditions. Two distinctly different flow patterns are found to develop depending on piloting and liner cooling parameters. These flow patterns are characterized with respect to flame stability, blow out limits, combustion noise, and emissions. The combustion system explored consists of a single burner similar to the burners used in Siemens annular combustion systems. The burner feeds a distinctively nonadiabatic combustion chamber operated with natural gas under atmospheric pressure. Liner cooling is mimicked by purely convective cooling and an additional flow of “leakage air” injected into the combustion chamber. Both additional air flow and the pilot fuel ratio were found to have a strong influence on the flow structure and stability of the flame close to the lean blow off (LBO) limit. It is shown by laser Doppler velocimetry that the angle of the swirl cone is strongly affected by pilot fuel injection. Two distinct types of flow patterns are observed close to LBO in this large scale setup: While nonpiloted flames exhibit tight cone angles and small inner recirculation zones (IRZs), sufficient piloting results in a wide cone angle and a large IRZ. Only in the latter case, the main flow becomes attached to the combustor liner. Flame structures deduced from flow fields and CH-chemiluminescence images depend on both the pilot fuel injection and liner cooling.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 7

Normalized mean velocity for A1 and A2 (ϕglob=0.525, L=0%): (a) axial and (b) tangential component. Isolines represent u in both plots.

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Figure 8

Change of flow field with θ: u/uref at x/db=1.3 for a transition from A1N to A2

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Figure 9

From the narrow to the wide flow pattern: time trace of combustor pressure drop and wall heat flux

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Figure 10

Change of piloted flow field with ϕ: u/uref at x/db=1.3 for reduced fuel mass flow (θ=6%, L=0. Values for (ϕ=0.525, θ=2%, L=0%) plotted for reference.

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Figure 11

Wall heat flux as a function of ϕglob

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Figure 12

Emissions of CO, NOx, and UHC as a function of ϕglob

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Figure 13

CH*-chemiluminescence at the burner outlet for ϕ=0.5 and field of view

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Figure 1

Annular combustion chamber of the Siemens SGTxF type (4)

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Figure 2

Schematic of burner and test rig

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Figure 3

Schematic of the cooled liner structures of this test setup (left) and a common gas turbine (right)

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Figure 4

Measurement locations and coordinate system for LDV.

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Figure 5

Normalized mean velocity for A3 and A4 (ϕglob=0.516, L=5%): (a) axial and (b) tangential component. Isolines represent u in both plots

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Figure 6

rms of axial velocity urms for A3 and A4 (ϕglob=0.516, L=5%) with isolines of u

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