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

Experimental and Numerical Investigation of Fuel–Air Mixing in a Radial Swirler Slot of a Dry Low Emission Gas Turbine Combustor

[+] Author and Article Information
Festus Eghe Agbonzikilo

School of Engineering,
University of Lincoln,
Brayford Pool,
Lincoln LN6 7TS, UK
e-mail: fagbonzikilo@lincoln.ac.uk

Ieuan Owen

Professor
Mechanical Engineering,
School of Engineering,
University of Lincoln,
Brayford Pool,
Lincoln LN6 7TS, UK
e-mail: iowen@lincoln.ac.uk

Jill Stewart

Professor
Mechanical Engineering,
Department of Engineering and Mathematics,
Sheffield Hallam University,
City Campus,
Sheffield S1 1WB, UK
e-mail: J.Stewart@shu.ac.uk

Suresh Kumar Sadasivuni

Siemens Industrial Turbomachinery Limited,
P.O. Box 1,
Lincoln LN5 7FD, UK
e-mail: suresh.sadasivuni@siemens.com

Mike Riley

School of Engineering,
University of Lincoln,
Brayford Pool,
Lincoln LN6 7TS, UK
e-mail: mriley@lincoln.ac.uk

Victoria Sanderson

Siemens Industrial Turbomachinery Limited,
P.O. Box 1,
Lincoln LN5 7FD, UK
e-mail: victoria.sanderson@siemens.com

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 29, 2015; final manuscript received September 21, 2015; published online November 17, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(6), 061502 (Nov 17, 2015) (13 pages) Paper No: GTP-15-1381; doi: 10.1115/1.4031735 History: Received July 29, 2015; Revised September 21, 2015

This paper presents the results of an investigation in which the fuel/air mixing process in a single slot within the radial swirler of a dry low emission (DLE) combustion system is explored using air/air mixing. Experimental studies have been carried out on an atmospheric test facility in which the test domain is a large-scale representation of a swirler slot from a Siemens proprietary DLE combustion system. Hot air with a temperature of 300 °C is supplied to the slot, while the injected fuel gas is simulated using air jets with temperatures of about 25 °C. Temperature has been used as a scalar to measure the mixing of the jets with the cross-flow. The mixture temperatures were measured using thermocouples while Pitot probes were used to obtain local velocity measurements. The experimental data have been used to validate a computational fluid dynamics (CFD) mixing model. Numerical simulations were carried out using CFD software ansys-cfx. Due to the complex three-dimensional flow structure inside the swirler slot, different Reynolds-averaged Navier–Stokes (RANS) turbulence models were tested. The shear stress transport (SST) turbulence model was observed to give best agreement with the experimental data. The momentum flux ratio between the main air flow and the injected fuel jet, and the aerodynamics inside the slot were both identified by this study as major factors in determining the mixing characteristics. It has been shown that mixing in the swirler can be significantly improved by exploiting the aerodynamic characteristics of the flow inside the slot. The validated CFD model provides a tool which will be used in future studies to explore fuel/air mixing at engine conditions.

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References

Figures

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Fig. 1

A Siemens industrial gas turbine engine showing the components of a generic DLE combustion system. (Courtesy of SITL).

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Fig. 2

The radial swirler showing a rectangular slot. (Courtesy of SITL).

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Fig. 3

Principle of a jet in cross-flow [6,7]

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Fig. 4

Experimental test rig with arrows indicating the direction of air flow

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Fig. 6

The pressure and suction sides of the swirler slot

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Fig. 7

The rake showing 3 detachable Pitot tubes and 12 thermocouple probes mounted on it

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Fig. 8

The rake positioned in the swirler slot for experimental data measurements

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Fig. 9

CFD domain with boundaries

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Fig. 10

Comparison of different RANS turbulence models against experimental data by PTP on the pressure side of the swirler slot, at plane x/L = 0.6

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Fig. 11

Comparison of different RANS turbulence models against experimental data by PTC at the centerline of the swirler slot, at plane x/L = 0.6

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Fig. 12

Temperature profile measured by TCP on the pressure side compared with CFD at plane x/L = 0.6

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Fig. 13

Temperature profile measured by TCC in the region of the slot centerline compared with CFD at plane x/L = 0.6

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Fig. 14

Temperature profile measured by TCS on the suction side compared with CFD at plane x/L = 0.6

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Fig. 15

Experimental and CFD temperature contour plots indicating mixing at a vertical plane x/L = 0.3

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Fig. 16

The flow recirculation zone including axial velocity profiles across the slot width in the midheight region of the swirler slot

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Fig. 17

TKE distribution within the swirler slot at a horizontal plane located midheight of the slot

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Fig. 18

Effect of recirculation zone on mixing. The shear layer opposes the penetration of the jet toward the suction wall.

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Fig. 19

Comparison of mixing characteristics resulting from injecting fuel from the pressure and suction sides of the swirler slot. Plane shown is at exit of the slot (i.e., 100% of slot length).

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Fig. 20

The recirculation zone formed within the swirler slot when fuel injection is made from the suction side

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