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Research Papers

Influence of Purge Flow Swirl at Exit to the High-Pressure Compressor on OGV/Pre-Diffuser and Combustion System Aerodynamics

[+] Author and Article Information
A. Duncan Walker

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

Bharat Koli

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

Peter A. Beecroft

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

1Corresponding author.

Manuscript received May 11, 2018; final manuscript received May 9, 2019; published online June 14, 2019. Assoc. Editor: Guillermo Paniagua.

J. Turbomach 141(9), 091009 (Jun 14, 2019) (14 pages) Paper No: TURBO-18-1105; doi: 10.1115/1.4043781 History: Received May 11, 2018; Accepted May 09, 2019

As aero gas turbine designs strive for ever greater efficiencies, the trend is for engine overall pressure ratios to rise. Although this provides greater thermal efficiency, it means that cycle temperatures also increase. One potential solution to managing the increasing temperatures is to employ a cooled cooling air system. In such a system, a purge flow into the main gas path downstream of the compressor will be required to prevent hot gas being ingested into the rotor drive cone cavity. However, the main gas path in compressors is aerodynamically sensitive and it is important to understand, and mitigate, the impact such a flow may have on the compressor outlet guide vanes, pre-diffuser, and the downstream combustion system aerodynamics. Initial computational fluid dynamics (CFD) predictions demonstrated the potential of the purge flow to negatively affect the outlet guide vanes and alter the inlet conditions to the combustion system. The purge flow modified the incidence onto the outlet guide vane, at the hub, such that the secondary flows increased in magnitude. An experimental assessment carried out using an existing fully annular, isothermal test facility confirmed the CFD results and importantly demonstrated that the degradation in the combustor inlet flow resulted in an increased combustion system loss. At the proposed purge flow rate, equal to ∼1% of the mainstream flow, these effects were small with the system loss increasing by ∼4%. However, at higher purge flow rates (up to 3%), these effects became notable and the outlet guide vane and pre-diffuser flow degraded significantly with a resultant increase in the combustion system loss of ∼13%. To mitigate these effects, CFD was used to examine the effect of varying the purge flow swirl fraction in order to better align the flow at the hub of the outlet guide vane. With a swirl fraction of 0.65 (x rotor speed), the secondary flows were reduced below that of the datum case (with no purge flow). Experimental data showed good agreement with the predicted flow topology and performance trends but the measured data showed smaller absolute changes. Differences in system loss were measured with savings of around 10% at the turbine feed ports for a mass flow ratio of 1% and a swirl fraction of 0.65.

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References

Advisory Council Aviation Research and Innovation in Europe, 2011, “Flightpath 2050—Europe’s Vision for Aviation”, http://ec.europa.eu/transport/modes/air/doc/flightpath2050.pdf. Accessed January 2018.
Wilfert, G., Sieber, J., Rolt, A., Baker, N., Touyeras, A., and Colantuoni, S., 2007, “New Environmentally Friendly Aero Engine Core Concepts,” ISABE Paper No. 2007-1120.
Walker, A. D., Carrotte, J. F., and McGuirk, J. J., 2007, “Enhanced External Aerodynamic Performance of a Generic Combustor Using an Integrated OGV/Pre-Diffuser Design Technique,” ASME J. Eng. Gas Turbines Power, 129(1), pp. 80–87. [CrossRef]
Walker, A. D., Carrotte, J. F., and McGuirk, J. J., 2008, “Compressor/Diffuser/Combustor Aerodynamic Interactions in Lean Module Combustors,” ASME J. Eng. Gas Turbines Power, 130(1), p. 011504. [CrossRef]
Walker, A. D., Carrotte, J. F., and McGuirk, J. J., 2009, “The Influence of Dump Gap on External Combustor Aerodynamics at High Fuel Injector Flow Rates,” ASME J. Eng. Gas Turbines Power, 131(3), p. 031506. [CrossRef]
Ford, C. L., Carrotte, J. F., and Walker, A. D., 2012, “The Impact of Compressor Exit Conditions on Fuel Injector Flows,” ASME J. Eng. Gas Turbines Power, 134(11), p. 111504. [CrossRef]
Sharma, O. P., and Butler, T. L., 1987, “Predictions of Endwall Losses and Secondary Flows in Axial Flow Turbine Cascades,” ASME J. Turbomach., 109(2), pp. 229–236. [CrossRef]
Ong, J., Miller, R. J., and Uchida, S., 2012, “The Effect of Coolant Injection on the Endwall Flow of a High Pressure Turbine,” ASME J. Turbomach., 134(5), p. 051003. [CrossRef]
McLean, C., Camci, C., and Glezer, B., 2001, “Mainstream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High-Pressure Turbine Stage. Part I: Aerodynamic Measurements in the Stationary Frame,” ASME J. Turbomach., 123(4), pp. 687–696. [CrossRef]
McLean, C., Camci, C., and Glezer, B., 2001, “Mainstream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High-Pressure Turbine Stage. Part II: Aerodynamic Measurements in the Rotational Frame,” ASME J. Turbomach., 123(4), pp. 697–703. [CrossRef]
Barigozzi, G., Franchini, G., Perdichizzi, A., Maritano, M., and Abram, R., 2014, “Influence of Purge Flow Injection Angle on the Aero-Thermal Performance of a Rotor Blade Cascade,” ASME J. Turbomach., 136(4), p. 041012. [CrossRef]
Schrewe, S., Werschnik, H., and Schiffer, H., 2013, “Experimental Analysis of the Interaction Between Rim Seal and Main Annulus Flow in a Low Pressure Two Stage Axial Turbine,” ASME J. Turbomach., 135(5), p. 051003. [CrossRef]
Stevens, S. J., Nayak, U. S. L., Preston, J. F., and Scrivener, C. T. J., 1978, “Influence of Compressor Exit Conditions on Diffuser Performance,” J. Aircraft, 15(8), pp. 482–488. [CrossRef]
Stevens, S. J., and Williams, G. J., 1980, “The Influence of Inlet Conditions on the Performance of Two Annular Diffusers,” ASME J. Fluids Eng., 102(3), pp. 357–363. [CrossRef]
Stevens, S. J., Harasgama, S. P., and Wray, A. P., 1984, “The Influence of Blade Wakes on Combustor Shortened Pre-Diffusers,” J. Aircraft, 21(9), p. 641. [CrossRef]
Zierer, T., 1993, “Experimental Investigation of the Flow in Diffusers Behind an Axial Flow Compressor,” ASME Paper No. 93-GT-347.
Barker, A. G., and Carrotte, J. F., 2001, “The Influence of Compressor Exit Conditions on Combustor Annular Diffusers—Part I: Diffuser Performance,” AIAA J. Propul. Power, 17(3), pp. 678–686. [CrossRef]
Barker, A. G., and Carrotte, J. F., 2001, “The Influence of Compressor Exit Conditions on Combustor Annular Diffusers—Part II: Flow Redistribution Within the Diffuser,” AIAA J. Propul. Power, 17(3), pp. 687–695. [CrossRef]
Walker, A. D., Koli, B., Liang, G., Beecroft, P., and Zedda, M., 2017, “Impact of a Cooled Cooling Air System on the External Aerodynamics of a Gas Turbine Combustion System,” ASME J. Eng. Gas Turbines Power, 139(5), p. 051504. [CrossRef]
Cumpsty, N. A., 1989, Compressor Aerodynamics, Longman Scientific and Technical, Harlow, Essex, UK.
Howard, J. H. G., Henseler, H. J. and Thornton-Trump, A. B., 1967, “Performance and Flow Regimes for Annular Diffusers,” ASME Paper 67-WA/FE-21.
Wray, A. P. and Carrotte, J. F., 1993, “The Development of a Large Annular Facility for Testing Gas Turbine Combustor Diffuser Systems,” Paper No. AIAA-93-2546.
Klein, A., 1995, “Characteristics of Combustor Diffusers,” Prog. Aerosp. Sci., 31(3), pp. 171–271. [CrossRef]
Paniagua, G., Dénos, R., and Almeida, A., 2004, “Effect of the Hub Endwall Cavity Flow on the Flow-Field of a Transonic High-Pressure Turbine,” ASME J. Turbomach., 126(4), pp. 578–586. [CrossRef]
Koli, B., and Walker, A. D., 2016, “SILOET II Project 18 Deliverable 2.2.6 CCA HP System Purge Flow Optimization—CFD,” Report TT/UTC/16/R32, Department of Aeronautical and Automotive Engineering, Loughborough University, UK.

Figures

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Fig. 1

Cooled cooling air concept [2]

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Fig. 2

Secondary air systems—compressor exit: (a) conventional “outflow” and (b) proposed “purge” flow

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Fig. 3

Test rig cross section

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Fig. 4

Typical pre-diffuser loading chart [19,21]

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Fig. 5

Purge flow path (test rig and CFD model)

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Fig. 6

Circumferential variation in purge flow (1% MFR)

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Fig. 7

Axial variation on purge flow (1% MFR)

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Fig. 8

OGV/pre-diffuser CFD model

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Fig. 9

CFD validation—no purge flow—OGV exit: (a) experiment and (b) CFD

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Fig. 10

CFD validation—no purge flow—diffuser exit: (a) experiment and (b) CFD

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Fig. 11

Effect of purge flow location (CFD)—1% MFR—OGV exit: (a) slot 1, (b) slot 3, and (c) slot 5

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Fig. 12

Effect of purge flow location (CFD)—1% MFR—diffuser exit: (a) slot 1, (b) slot 3, and (c) slot 5

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Fig. 13

Effect of purge flow rate (CFD)—slot 5—OGV exit: (a) 1%, (b) 1.5%, and (c) 2%

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Fig. 14

Effect of purge flow rate (CFD)—slot 5—diffuser exit: (a) 1%, (b) 1.5%, and (c) 2%

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Fig. 15

Final test rig configuration

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Fig. 16

Circumferentially averaged profiles at rotor exit for varying MFR

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Fig. 17

Contours of axial velocity at OGV exit for varying MFR: (a) 0%, (b) 0.49%, (c) 0.97%, (d) 1.45%, (e) 1.91%, (f) 2.36%, and (g) 2.84%

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Fig. 18

Circumferentially averaged profiles at OGV exit for varying MFR

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Fig. 19

Contours of axial velocity at diffuser exit for varying MFR: (a) 0%, (b) 0.49%, (c) 0.97%, (d) 1.45%, (e) 1.91%, (f) 2.36%, and (g) 2.84%

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Fig. 20

Circumferentially averaged profiles at diffuser exit for varying MFR

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Fig. 21

Variation of total pressure loss with MFR

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Fig. 22

Contours of axial velocity (CFD) at OGV exit for varying MFR and SF

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Fig. 23

Contours of axial velocity (CFD) at diffuser exit for varying MFR and SF

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Fig. 24

Predicted velocity contours immediately upstream of the OGV

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Fig. 25

Predicted streamlines close to the hub (MFR 1%): (a) datum (SF 0), (b) SF 0.35, (c) SF 0.5, (d) SF 0.65, and (e) SF 0.75

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Fig. 26

Predicted axial velocity contours on a plane at 25% height: (a) datum and (b) SF 0.75

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Fig. 27

Streamlines released from the hub/purge (MFR 1%): (a) datum (0%) and (b) SF 0.75

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Fig. 28

Pre-swirl nozzle design

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Fig. 29

Contours of axial velocity at OGV exit for varying MFR and SF

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Fig. 30

Contours of axial velocity at pre-diffuser exit for varying MFR and SF

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Fig. 31

Total pressure loss data, λZx/λdatum: (a) MFR 1% and (b) MFR 1.5%

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