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Research Papers

An Investigation of Reynolds Lapse Rate for Highly Loaded Low Pressure Turbine Airfoils With Forward and Aft Loading

[+] Author and Article Information
M. Eric Lyall1

 Air Force Institute of Technology, 2950 Hobson Way, Bldg 641, Wright Patterson AFB, OH 45433michael.lyall@afit.edu

Paul I. King

 Air Force Institute of Technology, 2950 Hobson Way, Bldg 641, Wright Patterson AFB, OH 45433paul.king@afit.edu

Rolf Sondergaard

 Propulsion Directorate of the Air Force Research Laboratory, 1950 Fifth Street, Building 18 Room D132, Wright Patterson AFB, OH 45433rolf.sondergaard@wpafb.af.mil

John P. Clark

 Propulsion Directorate of the Air Force Research Laboratory, 1950 Fifth Street, Building 18 Room D132, Wright Patterson AFB, OH 45433john.clark3@wpafb.af.mil

Mark W. McQuilling

 Saint Louis University, 3450 Lindell Boulevard, St. Louis, MO 63103mmcquil2@slu.edu

1

Corresponding author.

J. Turbomach 134(5), 051035 (May 24, 2012) (9 pages) doi:10.1115/1.4004826 History: Received July 11, 2011; Revised July 27, 2011; Published May 24, 2012

This paper presents an experimental and computational study of the midspan low Reynolds number loss behavior for two highly loaded low pressure turbine airfoils, designated L2F and L2A, which are forward and aft loaded, respectively. Both airfoils were designed with incompressible Zweifel loading coefficients of 1.59. Computational predictions are provided using two codes, Fluent (with k-kl -ω model) and AFRL’s Turbine Design and Analysis System (TDAAS), each with a different eddy-viscosity RANS based turbulence model with transition capability. Experiments were conducted in a low speed wind tunnel to provide transition models for computational comparisons. The Reynolds number range based on axial chord and inlet velocity was 20,000 < Re < 100,000 with an inlet turbulence intensity of 3.1%. Predictions using TDAAS agreed well with the measured Reynolds lapse rate. Computations using Fluent however, predicted stall to occur at significantly higher Reynolds numbers as compared to experiment. Based on triple sensor hot-film measurements, Fluent ’s premature stall behavior is likely the result of the eddy-viscosity hypothesis inadequately capturing anisotropic freestream turbulence effects. Furthermore, rapid distortion theory is considered as a possible analytical tool for studying freestream turbulence that influences transition near the suction surface of LPT airfoils. Comparisons with triple sensor hot-film measurements indicate that the technique is promising but more research is required to confirm its utility.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of AFRL low speed wind tunnel test section

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Figure 2

Experimental and computational Reynolds lapse for L2F. The Pack B results are from McQuilling [8].

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Figure 3

Experimental and computational Reynolds lapse for L2A. The Pack B results are from McQuilling [8].

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Figure 4

Pressure loading distributions for the L2A and L2F airfoils

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Figure 5

Turbulent kinetic energy at 0.5Cax for the L2A cascade, normalized by the inlet turbulent kinetic energy. Re = 100 k.

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Figure 6

Measured components of the Reynolds stress tensor within the passage at 0.5Cax for the L2A cascade. Re = 100 k.

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Figure 7

Contour plot of the scaled velocity magnitude for the L2A airfoil

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Figure 8

Pitchwise integral scale development in the exit traverse plane for the L2A and L2F airfoils. Data were captured at Re = 100 k.

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Figure 9

Sketch of Goldstein and Durbin’s [35] geometry

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Figure 10

Comparison of L2A midspan turbulence development at 0.5Cax with plane strain rapid distortion. Re = 100 k for experimental results. (δ1 /δ2  = 2.0 and 2δ2 /Lin  = 1.0 for plane strain results of Goldstein and Durbin [35]).

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