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

Impact of a Cooled Cooling Air System on the External Aerodynamics of a Gas Turbine Combustion System

[+] Author and Article Information
A. Duncan Walker

Department of Aeronautical and
Automotive Engineering,
Loughborough University,
Loughborough LE11 3TU, Leicestershire, UK
e-mail: A.D.Walker@lboro.ac.uk

Bharat Koli

Department of Aeronautical and
Automotive Engineering,
Loughborough University,
Loughborough LE11 3TU, Leicestershire, UK
e-mail: B.Koli@lboro.ac.uk

Liang Guo

Associate Professor
Department of Internal Combustion Engines,
Jilin University,
Changchun 130022, China
e-mail: liangguo@jlu.edu.cn

Peter Beecroft

Rolls-Royce plc,
SIN-A-65,
P.O. Box 31,
Moor Lane,
Derby DE24 8BJ, UK
e-mail: Peter.Beecroft@Rolls-Royce.com

Marco Zedda

Rolls-Royce plc,
ML-92,
P.O. Box 31,
Moor Lane,
Derby DE24 8BJ, UK
e-mail: Marco.Zedda@Rolls-Royce.com

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 1, 2016; final manuscript received September 30, 2016; published online January 10, 2017. Assoc. Editor: Joseph Zelina.

J. Eng. Gas Turbines Power 139(5), 051504 (Jan 10, 2017) (13 pages) Paper No: GTP-16-1199; doi: 10.1115/1.4035228 History: Received June 01, 2016; Revised September 30, 2016

To manage the increasing turbine temperatures of future gas turbines a cooled cooling air system has been proposed. In such a system some of the compressor efflux is diverted for additional cooling in a heat exchanger (HX) located in the bypass duct. The cooled air must then be returned, across the main gas path, to the engine core for use in component cooling. One option is do this within the combustor module and two methods are examined in the current paper; via simple transfer pipes within the dump region or via radial struts in the prediffuser. This paper presents an experimental investigation to examine the aerodynamic impact these have on the combustion system external aerodynamics. This included the use of a fully annular, isothermal test facility incorporating a bespoke 1.5 stage axial compressor, engine representative outlet guide vanes (OGVs), prediffuser, and combustor geometry. Area traverses of a miniature five-hole probe were conducted at various locations within the combustion system providing information on both flow uniformity and total pressure loss. The results show that, compared to a datum configuration, the addition of transfer pipes had minimal aerodynamic impact in terms of flow structure, distribution, and total pressure loss. However, the inclusion of prediffuser struts had a notable impact increasing the prediffuser loss by a third and consequently the overall system loss by an unacceptable 40%. Inclusion of a hybrid prediffuser with the cooled cooling air (CCA) bleed located on the prediffuser outer wall enabled an increase of the prediffuser area ratio with the result that the system loss could be returned to that of the datum level.

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Figures

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Fig. 1

Cooled cooling air concept [2]

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Fig. 2

Potential CCA routes across the main gas path (a) transfer pipe concept and (b) via struts in the prediffuser

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Fig. 3

Test rig photograph

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Fig. 4

Test rig cross section

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Fig. 5

Prediffuser design parameters (a) datum 1, (b) datum 2, (c) strutted, and (d) hybrid

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Fig. 6

Typical prediffuser loading chart

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Fig. 7

Transfer pipe test section

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Fig. 9

Mechanisms of a hybrid diffuser [14]

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Fig. 10

Hybrid diffuser geometries

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Fig. 11

CFD model—hybrid 1—axial velocity (4% bleed)

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Fig. 12

CFD model—radial velocity (4% bleed) (a) hybrid 1 and (b) hybrid 2

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Fig. 13

CFD model—hybrid 2—axial velocity (4% bleed)

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Fig. 14

CFD model—hybrid 3—axial velocity (4% bleed)

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Fig. 15

Contours of axial velocity—OGV exit (A)—datum 1 OGV/prediffuser (a) without transfer pipe (20 deg sector) and (b) with transfer pipe (20 deg sector)

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Fig. 16

Contours of axial velocity—prediffuser exit (B)—datum 1 OGV/prediffuser (a) without transfer pipe (20 deg sector) and (b) with transfer pipe (20 deg sector)

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Fig. 17

Contours of axial velocity—inner annulus (C)—datum 1 OGV/prediffuser (a) without transfer pipe (20 deg sector) and (b) with transfer pipe (40 deg sector)

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Fig. 18

Contours of axial velocity—outer annulus (E)—datum 1 OGV/prediffuser (a) without transfer pipe (20 deg sector) and (b) with transfer pipe (40 deg sector)

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Fig. 19

Total pressure feed to the fuel injector

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Fig. 20

Contours of axial velocity—OGV exit (A) (a) clean datum 2 OGV/prediffuser (20 deg sector), (b) strutted datum 2 OGV/prediffuser (20 deg sector), and (c) hybrid prediffuser (20deg sector)

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Fig. 21

Contours of axial velocity—prediffuser exit (B) (a) clean datum 2 OGV/prediffuser (20 deg sector) and (b) strutted datum 2 OGV/prediffuser (20 deg sector)

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Fig. 22

Averaged radial profiles—prediffuser exit (B) (a) axial velocity and (b) flow angles

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Fig. 23

Contours of axial velocity—prediffuser exit (B)—hybrid prediffuser (a) CFD—0%, 2%, and 4% bleed and (b) experiment—0%, 2%, and 4% bleed

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Fig. 24

Contours of axial velocity—prediffuser exit (B)—hybrid prediffuser (a) 2% bleed (20 deg sector) and (b) 4% bleed (20deg sector)

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Fig. 25

Contours of axial velocity—inner annulus (C2) (a) clean datum 2 OGV/prediffuser (20 deg sector), (b) strutted datum 2 OGV/prediffuser (20 deg sector), and (c) hybrid prediffuser—4% bleed (20 deg sector)

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Fig. 26

Contours of axial velocity—outer annulus (E2) (a) clean datum 2 OGV/prediffuser (20 deg sector), (b) strutted datum 2 OGV/prediffuser (20 deg sector), and (c) hybrid prediffuser—4% bleed (20 deg sector)

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Fig. 27

Performance parameters—transfer pipes (a) mass-weighted total pressure loss coefficient and (b) mass-weighted static pressure recover coefficient

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Fig. 28

Performance parameters—strutted and hybrid prediffuser (a) mass-weighted total pressure loss coefficient and (b) mass-weighted static pressure recover coefficient

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