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Research Papers

Endwall Loss Reduction of High Lift Low Pressure Turbine Airfoils Using Profile Contouring—Part I: Airfoil Design

[+] Author and Article Information
M. Eric Lyall

Aerospace Systems Directorate,
Air Force Research Laboratory,
1950 Fifth Street,
Wright Patterson AFB, OH 45433
e-mail: michael.lyall@us.af.mil

Paul I. King

Air Force Institute of Technology,
2950 Hobson Way, Building 641,
Wright Patterson AFB, OH 45433
e-mail: paul.king@us.edu

John P. Clark

Aerospace Systems Directorate,
Air Force Research Laboratory,
1950 Fifth Street,
Wright Patterson AFB, OH 45433
e-mail: john.clark.38@us.af.mil

Rolf Sondergaard

Aerospace Systems Directorate,
Air Force Research Laboratory,
1950 Fifth Street,
Wright Patterson AFB, OH 45433
e-mail: rolf.sondergaard@us.af.mil

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 23, 2013; final manuscript received September 24, 2013; published online January 31, 2014. Editor: Ronald Bunker.

J. Turbomach 136(8), 081005 (Jan 31, 2014) (9 pages) Paper No: TURBO-13-1195; doi: 10.1115/1.4025951 History: Received August 23, 2013; Revised September 24, 2013

This paper presents the reasoning for and the design process of contouring a high lift front-loaded low pressure turbine (LPT) airfoil near the endwall to reduce the endwall loss. The test airfoil, L2F, was designed to the approximate gas angles with 38% larger pitchwise spacing than the widely studied Pack B airfoil. Being more front-loaded with a higher stagger angle, L2F is shown to produce more endwall losses than Pack B. It is suggested that the high endwall loss of L2F is due to the high stagger angle, not front-loading, as usually suggested in the literature. A procedure is presented to approximate the front-loading and stall resistance of L2F and obtain a low stagger version of that airfoil, designated as L2F-LS. A contoured airfoil is then designed by transitioning L2F into L2F-LS at the endwall to obtain a benefit from the reduced stagger angle at the endwall. Due to the contouring process generating a fillet, the contoured airfoil is referred to as L2F-EF (“endwall fillet”). Predictions in this paper suggest endwall loss reductions between 17% and 24% at Re = 100,000. Linear cascade experiments in Part II of this paper indicate that L2F-EF reduces endwall losses more than 20% compared to L2F. The overall conclusion is that the stagger angle has a significant effect on endwall loss and should be considered for designing high lift LPT airfoils at the endwall.

Copyright © 2014 by ASME
Topics: Pressure , Design , Airfoils
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References

Figures

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Fig. 1

Cascade definitions

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Fig. 2

Comparison of the Pack B and L2F profiles

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Fig. 3

Comparison of the Pack B and L2F midspan Reynolds lapse

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Fig. 4

Pack B and L2F pressure loading (LEO code)

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Fig. 5

Effect of the static pressure field on the inlet boundary layer flow for the Pack B and L2F profiles (streamlines initiated at 1/2 the inlet boundary layer thickness)

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Fig. 6

Leading edge streamlines showing more entrainment of the inlet boundary layer fluid for L2F compared to Pack B (streamlines released at the edge of the inlet boundary layer)

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Fig. 7

Effect of peak suction and lift on BLFP

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Fig. 8

Comparison of the new baseline profile with L2F

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Fig. 9

Pressure surface modifications to eliminate the pressure surface separation

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Fig. 10

Y contours to show the elimination of the pressure surface separation bubble (computed using LEO; Re = 100,000)

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Fig. 11

L2F-LS Reynolds lapse compared to L2F and Pack B

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Fig. 12

L2F-LS pressure loading compared to L2F and Pack B

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Fig. 13

Illustration of the L2F-EF airfoil near the endwall to show the fillet shape

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Fig. 14

Sensitivity of the L2F-EF passage loss to the fillet height; Re = 100,000 (computed using LEO)

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Fig. 15

Comparison of the L2F and L2F-LS endwall and passage performance

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Fig. 16

Endwall loss reduction of L2F-LS compared to L2F

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Fig. 17

Comparison of the Yew reduction between L2F-LS and L2F-EF

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Fig. 18

Comparison of the L2-series passage loss (Yps) to that of the conventionally loaded Pack B airfoil

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Fig. 19

Comparison of the L2-series endwall loss (Yew) to that of the conventionally loaded Pack B airfoil

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