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Research Papers

Heat Transfer to an Actively Cooled Shroud With Blade Rotation

[+] Author and Article Information
Onieluan Tamunobere

Turbine Innovation and Energy
Research (TIER) Center,
Mechanical Engineering Department,
Louisiana State University,
Baton Rouge, LA 70803
e-mail: otamun3@lsu.edu

Christopher Drewes

Turbine Innovation and Energy
Research (TIER) Center,
Mechanical Engineering Department,
Louisiana State University,
Baton Rouge, LA 70803
e-mail: cdrewe1@lsu.edu

Sumanta Acharya

Turbine Innovation and Energy
Research (TIER) Center,
Mechanical Engineering Department,
Louisiana State University,
Baton Rouge, LA 70803;
Mechanical Engineering Department,
University of Memphis,
Memphis, TN 38152
e-mail: acharya@tigers.lsu.edu

Chiyuki Nakamata

Aero-Engine & Space Operations,
IHI Corporation,
Tokyo 190-1297, Japan

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received December 15, 2014; final manuscript received June 24, 2015; published online September 22, 2015. Assoc. Editor: Bengt Sunden.

J. Thermal Sci. Eng. Appl 7(4), 041020 (Sep 22, 2015) (14 pages) Paper No: TSEA-14-1279; doi: 10.1115/1.4031357 History: Received December 15, 2014; Revised June 24, 2015

An experimental study of the shroud heat transfer behavior and the effectiveness of shroud cooling are undertaken in a single-stage turbine at low rotation speeds. The shroud consists of a periodic distribution of laterally oriented cooling holes that are angled at 45 deg to the shroud surface in a repeating circumferential pattern and has five unique hole pitches in the axial direction. Measurements of the normalized Nusselt number and film cooling effectiveness are done using liquid crystal thermography. These measurements are reported for the no-coolant case and nominal blowing ratios (BRs) of 1.0, 1.5, 2.0, 2.5, and 3.0. The tests are performed at an inflow Reynolds number of 17,500 corresponding to a scaled down design rotation speed of 550 rpm, and two off-design speeds imposed by a motor: (1) a rotation speed below the design speed (400 rpm) and (2) a rotation speed above the design speed (700 rpm). The results at the design speed show that increasing the BR increases the area-averaged film cooling effectiveness, while the Nu/Nu0 in the shroud hole region decreases. As the rotor speed is changed from the design speed, the high Nu/Nu0 region migrates on the shroud surface. This migration affects the coolant coverage in the shroud hole region resulting in increased coolant coverage at below-design rotation speeds and decreased coolant coverage at above-design rotation speeds. At all rotation speeds, as the BR increases, the area-averaged film cooling effectiveness in the shroud hole region increases. Decreasing the circumferential shroud coolant hole spacing changes the lateral heat transfer profile from a periodic sinusoidal distribution for a shroud hole spacing of P/D = 10.4 to a more even distribution for a smaller shroud hole spacing (P/D = 4.8).

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References

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Figures

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Fig. 1

Schematic of rotating turbine facility

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Fig. 2

(a) Stator–rotor–stator arrangement and (b) rotor blade profile with rotor inlet velocity triangle

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Fig. 3

Freestream temperature versus time immediately upstream of stator blades during testing

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Fig. 4

Test section of rotating facility

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Fig. 5

Shroud hole schematic and data

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Fig. 6

Laterally averaged h/h0 for the validation test and comparison with data from literature

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Fig. 7

Laterally averaged η for the validation test and comparison with data from literature [16,18,19]

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Fig. 8

Nu/Nu0 at the design speed for varying BRs: (a) no-coolant case, (b) BR = 1.0, (c)BR = 1.5, (d) BR = 2.0, (e) BR = 2.5, and (f) BR = 3.0

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Fig. 9

ηf at the design speed for varying BRs: (a) BR = 1.0, (b) BR = 1.5, (c)BR = 2.0, (d) BR = 2.5, and (e) BR = 3.0

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Fig. 10

Area-averaged Nu/Nu0 in the shroud hole region as a function of BR for different rotation speeds

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Fig. 11

Area-averaged ηf in the shroud hole region as a function of BR for different rotation speeds

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Fig. 12

Nu/Nu0 at below-design speed for varying BRs: (a) no-coolant case, (b) BR = 1.0, (c) BR = 1.5, and (d) BR = 2.0

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Fig. 13

ηf at below-design speed for varying BRs: (a) BR = 1.0, (b) BR = 1.5, and (c) BR = 2.0

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Fig. 14

Nu/Nu0 at above-design speed for varying BRs: (a) no-coolant case, (b) BR = 1.0, (c) BR = 1.5, (d) BR = 2.0, (e) BR = 2.5, and (f) BR = 3.0

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Fig. 15

ηf at above-design speed for varying BRs: (a) BR = 1.0, (b) BR = 1.5, (c)BR = 2.0, (d) BR = 2.5, and (e) BR = 3.0

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Fig. 16

Area-averaged Nu/Nu0 in the shroud hole region as a function of rotation speed for different BRs

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Fig. 17

Area-averaged ηf in the hole region as a function of rotation speed for different BRs

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Fig. 18

Area-averaged Nu/Nu0 in the shroud region downstream of the coolant holes as a function of rotation speed for different BRs

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Fig. 19

Lateral Nu/Nu0 (top) and lateral film cooling (bottom) distribution at row 2 and BR = 1.5 at different rotation speeds

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Fig. 20

Lateral Nu/Nu0 (top) and lateral film cooling (bottom) distribution at row 4 and BR = 1.5 at different rotation speeds

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Fig. 21

Lateral Nu/Nu0 distribution for row 2 (top) and row 4 (bottom) at the design speed and at different BRs

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