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

# Investigation of Flow Aerodynamics for Optimal Fuel Placement and Mixing in the Radial Swirler Slot of a Dry Low Emission Gas Turbine Combustion Chamber

[+] 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

Siemens Industrial Turbomachinery Limited,
P.O. Box 1,
Lincoln LN5 7FD, UK

Ronald A. Bickerton

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

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 13, 2015; final manuscript received August 31, 2015; published online November 3, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(5), 051505 (Nov 03, 2015) (13 pages) Paper No: GTP-15-1267; doi: 10.1115/1.4031529 History: Received July 13, 2015; Revised August 31, 2015

## Abstract

This paper is concerned with optimizing the fuel–air mixing processes that take place within the radial swirler slot of a dry low emission (DLE) combustion system. The aerodynamics of the flow within the slot is complex and this, together with the placement of the fuel holes with cross injection, controls the mixing of the fuel and air. Computational fluid dynamics (CFD) with the shear stress transport (SST) (k–$ω$) turbulence model was used for flow and mixing predictions within the radial swirler slot and for conducting a CFD-based design of experiments (DOE) optimization study, in which different parameters related to the fuel injection holes were varied. The optimization study was comprised of 25 orthogonal design configurations in the Taguchi L25 orthogonal array (OA). The test domain for the CFD, and its experimental validation, was a large-scale representation of a swirler slot from the Siemens proprietary DLE combustion system. The DOE study showed that the number of fuel holes, injection hole diameter, and interhole distance are the most influential parameters for determining optimal fuel mixing. Consequently, the optimized mixing configuration obtained from the above study was experimentally tested on an atmospheric test facility. The mixing patterns from experiments at various axial locations across the slot are in good agreement with the mixing predictions from the optimal CFD model. The optimized fuel injection design improved mixing compared with the baseline design by about 60%.

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## References

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Agbonzikilo, F. E. , 2015, “ Optimisation of Fuel-Air Mixing Processes in Gas Turbines,” Ph.D. thesis, University of Lincoln, Lincoln, UK.

## Figures

Fig. 1

DLE combustion system. Courtesy of SITL.

Fig. 2

The vortical structures of a jet in cross-flow [9]

Fig. 3

The experimental test rig with arrows indicating the direction of air-flow

Fig. 4

A detailed view of the swirler slot showing fuel holes locations and the pressure and suction sides of the slot. The swirler slot: (a) an isometric view of the slot showing the location of the base fuel hole; (b) a plan of the slot showing the slot inlet and exit; (c) a side view of the slot showing the side-wall fuel delivery; and (d) a section sc–sc through the slot-centerline revealing the twin side-wall fuel holes.

Fig. 5

CFD domain with boundaries, showing the side-wall holes, base fuel hole, and the counterbore

Fig. 6

Local recirculation zone in the swirler slot

Fig. 7

TKE in the swirler slot

Fig. 8

Bar chart showing all experimental designs and the corresponding MPU values. All MPU values are normalized using the MPU value of experimental design 0.

Fig. 9

Bar chart showing each parameter's contribution to mixing in the swirler slot

Fig. 10

The mean SN ratios and settings for all six parameters

Fig. 11

Graphs showing the behaviors of all six parameters to the mean of SN ratios. P2–P6 values have been normalized using the corresponding baseline values.

Fig. 12

Bar chart showing the performance of the optimal design configuration compared against the 24 CAD

Fig. 13

The contour plots of optimal and baseline designs, compared at an axial plane, 30% of the swirler slot length (plane at x/L = 0.3)

Fig. 14

The contour plots of optimal and baseline designs, compared at the slot exit plane (plane at x/L = 1)

Fig. 15

Optimized swirler slot experimental test rig

Fig. 16

Comparison of experimental results from the optimal and baseline swirler slot designs at plane 30% of the swirler slot length (x/L = 0.30)

Fig. 17

Comparison of experimental results from the optimal and baseline swirler slot designs at plane 60% of the swirler slot length (x/L = 0.60)

Fig. 18

Experimental result from the optimized swirler slot design at plane 80% of the swirler slot length (x/L = 0.80)

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