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Research Papers

An Experimental and Numerical Study on the Aerothermal Characteristics of a Ribbed Transonic Squealer-Tip Turbine Blade With Purge Flow

[+] Author and Article Information
A. Arisi

Mechanical Engineering Department,
Virginia Polytechnic Institute and
State University,
Blacksburg, VA 24061
e-mail: arisi@vt.edu

J. Phillips

Mechanical Engineering Department,
Virginia Polytechnic Institute and
State University,
Blacksburg, VA 24061
e-mail: jphill@vt.edu

W. F. Ng

Mechanical Engineering Department,
Virginia Polytechnic Institute and
State University,
Blacksburg, VA 24061
e-mail: wng@vt.edu

S. Xue

Mechanical Engineering Department,
Virginia Polytechnic Institute and
State University,
Blacksburg, VA 24061
e-mail: xuesong@vt.edu

H. K. Moon

Solar Turbines, Inc.,
San Diego, CA 92101
e-mail: Moon_Hee_Koo_X@solarturbines.com

L. Zhang

Solar Turbines, Inc.,
San Diego, CA 92101
e-mail: Zhang_Luzeng_J@solarturbines.com

1Corressponding author.

2Present address: Navigant, Inc., Chicago, IL.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received February 4, 2016; final manuscript received February 10, 2016; published online April 26, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(10), 101007 (Apr 26, 2016) (11 pages) Paper No: TURBO-16-1031; doi: 10.1115/1.4032925 History: Received February 04, 2016; Revised February 10, 2016

Detailed heat transfer coefficient (HTC) and film cooling effectiveness (Eta) distribution on a squealer-tipped first stage rotor blade were measured using an infrared technique. The blade tip design, obtained from the Solar Turbines, Inc., gas turbine, consists of double purge hole exits and four ribs within the squealer cavity, with a bleeder exit port on the pressure side close to the trailing edge. The tests were carried out in a transient linear transonic wind tunnel facility under land-based engine representative Mach/Reynolds number. Measurements were taken at an inlet turbulent intensity of Tu = 12%, with exit Mach numbers of 0.85 (Reexit = 9.75 × 105) and 1.0 (Reexit = 1.15 × 106) with the Reynolds number based on the blade axial chord and the cascade exit velocity. The tip clearance was fixed at 1% (based on engine blade span) with a purge flow blowing ratio, BR = 1.0. At each test condition, an accompanying numerical study was performed using Reynolds-averaged Navier–Stokes (RANS) equations solver ansys fluent to further understand the tip flow characteristics. The results showed that the tip purge flow has a blocking effect on the leakage flow path. Furthermore, the ribs significantly altered the flow (and consequently heat transfer) characteristics within the squealer-tip cavity resulting in a significant reduction in film cooling effectiveness. This was attributed to increased coolant–leakage flow mixing due to increased recirculation within the squealer cavity. Overall, the peak HTC on the cavity floor increased with exit Mach/Reynolds number.

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Figures

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Fig. 1

Scale model of the transonic wind tunnel at Virginia Tech

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Fig. 2

Linear cascade with three squealer-tipped blades, capable of purge flow blowing

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Fig. 3

Test blade geometry

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Fig. 5

Experiment and CFD prediction of the squealer-tip surface flow at Mexit = 0.85

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Fig. 6

CFD result of near-tip (94% height) pressure loading comparison between rib and ribless tip blade

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Fig. 7

(a) Surface oil flow visualization on a squealer tip with no ribs and no purge flow [18], (b) CFD prediction of near surface velocity vectors, and (c) squealer tip with ribs near surface flow velocity vectors

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Fig. 8

HTC distribution of different meshes at exit Mach number 0.85

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Fig. 9

(a) Experiment and CFD result of HTC distribution and (b) experiment and CFD result of film cooling effectiveness distribution

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Fig. 10

Velocity vector plot and cavity fluid temperature distribution along leakage path at x/Cx = 0.1

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Fig. 11

Velocity vector plot and cavity fluid temperature distribution along leakage path at x/Cx = 0

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Fig. 12

Velocity vector plot and cavity fluid temperature distribution along leakage path at x/Cx = 0.4

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Fig. 13

Velocity vector plot and cavity fluid temperature distribution along leakage path at x/Cx = 0.5

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Fig. 14

(a) Pressure distribution on the endwall surface (experiment) and (b) static-to-total pressure ratio on the endwall surface above the suction side rim

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Fig. 15

Contours of leakage mass flow rate at the tip clearance exit

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Fig. 16

HTC and film cooling effectiveness distributions on the squealer tip at Mexit = 1.0 (experiment)

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