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Effect of Turbulence Intensity and Periodic Unsteady Wake Flow Condition on Boundary Layer Development, Separation, and Reattachment Along the Suction Surface of a Low-Pressure Turbine Blade

[+] Author and Article Information
B. Öztürk, M. T. Schobeiri

Turbomachinery Performance and Flow Research Laboratory, Texas A&M University, College Station, TX 77843-3123

J. Fluids Eng 129(6), 747-763 (Oct 31, 2006) (17 pages) doi:10.1115/1.2734188 History: Received March 28, 2006; Revised October 31, 2006

This paper experimentally investigates the individual and combined effects of periodic unsteady wake flows and freestream turbulence intensity (FSTI) on flow separation along the suction surface of a low-pressure turbine blade. The experiments were carried out at a Reynolds number of 110,000 based on the suction surface length and the cascade exit velocity. The experimental matrix includes freestream turbulence intensities of 1.9%, 3.0%, 8.0%, and 13.0%, and three different unsteady wake frequencies with the steady inlet flow as the reference configuration. Detailed boundary layer measurements are performed along the suction surface of a highly loaded turbine blade with a separation zone. Particular attention is paid to the aerodynamic behavior of the separation zone at different FSTIs at steady and periodic unsteady flow conditions. The objective of the research is (i) to quantify the effect of FSTIs on the dynamics of the separation bubble at steady inlet flow conditions and (ii) to investigate the combined effects of Tuin and the unsteady wake flow on the behavior of the separation bubble.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Turbine cascade research facility with the components and the adjustable test section

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Figure 4

Static pressure distributions at Re=110,000 and reduced frequencies Ω=0, 1.59, 3.18 (no rod, 160mm, 80mm), SS=separation start, SE=separation end

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Figure 5

(a–d). Time-dependent ensemble-averaged velocities and fluctuations for Re=110,000 at a constant location s∕s0=3.36mm inside the bubble for different inlet turbulence intensities ranging from 1.9% to 13%

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Figure 6

Distribution of time-averaged velocity (a) and turbulence fluctuation root mean square (rms) (b) along the suction surface for steady case Ω=0(SR=∞) and unsteady cases Ω=1.59(SR=160mm) and S=3.18(SR=80mm) at Re=110,000 and FSTI=1.9% (without grid)

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Figure 7

Distribution of time-averaged velocity (a) and turbulence fluctuation rms (b) along the suction surface for steady case Ω=0(SR=∞) and unsteady cases Ω=1.59(SR=160mm) and Ω=3.18(SR=80mm) at Re=110,000 and FSTI=3% with grid TG1

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Figure 8

Distribution of time-averaged velocity (a) and turbulence fluctuation rms (b) along the suction surface for steady case Ω=0(SR=∞) and unsteady cases Ω=1.59(SR=160mm) and Ω=3.18(SR=80mm) at Re=110,000 and FSTI=8% with grid TG2

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Figure 9

Distribution of time-averaged velocity (a) and turbulence fluctuation rms (b) along the suction surface for steady case Ω=0(SR=∞) and unsteady cases Ω=1.59(SR=160mm) and Ω=3.18(SR=80mm) at Re=110,000 and FSTI=13% with grid TG3

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Figure 12

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=1.59(SR=160mm) at Re=110,000 and FSTI=8% (with TG2)

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Figure 13

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=1.59(SR=160mm) at Re=110,000 and FSTI=13% (with TG3)

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Figure 14

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=3.18(SR=80mm) at Re=110,000 and FSTI=1.9% (without grid)

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Figure 15

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=3.18(SR=80mm) at Re=110,000 and FSTI=3% (with TG1)

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Figure 18

Time-averaged momentum thickness for (a)FSTI=1.9% (without grid), (b)FSTI=3% (with grid TG1), (c)FSTI=8% (with grid TG2), and (d)FSTI=13% (with grid TG3) for three different reduced frequency of Ω=0, 1.59, 3.18 (no rod, 160mm, 80mm) at Re=110,000)

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Figure 19

Ensemble-averaged relative momentum thickness distribution along the suction surface for different streamwise positions for (a)FSTI=1.9% (without grid), (b)FSTI=3% (with grid TG1), (c)FSTI=8% (with grid TG2), and (d)FSTI=13% (with grid TG3) for Ω=1.59(160mm) at Re=110,000

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Figure 20

Time-averaged shape factor for (a)FSTI=1.9% (without grid), (b)FSTI=3% (with grid TG1), (c)FSTI=8% (with grid TG2), (d)FSTI=13% (with grid TG3) for three different reduced frequency of Ω=0, 1.59, 3.18 (no rod, 160mm, 80mm) at Re=110,000

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Figure 21

Ensemble-averaged relative momentum thickness distribution along the suction surface for different streamwise positions for (a)FSTI=1.9% (without grid), (b)FSTI=3% (with grid TG1), (c)FSTI=8% (with grid TG2), and (d)FSTI=13% (with-grid TG3) for Ω=3.18(80mm) at Re=110,000

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Figure 10

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=1.59(SR=160mm) at Re=110,000 and FSTI=1.9% (without grid)

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Figure 3

Turbine cascade research facility with three-axis traversing system

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Figure 2

Wake generator (left), generated velocity distributions (right)

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Figure 11

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=1.59(SR=160mm) at Re=110,000 and FSTI=3% (with TG1)

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Figure 16

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=3.18(SR=160mm) at Re=110,000 and FSTI=8% (with TG2)

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Figure 17

Ensemble-averaged velocity contours along the suction surface for different s∕s0 with time t∕τ as parameter for Ω=3.18(SR=160mm) at Re=110,000 and FSTI=13% (with TG3)

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