Research Papers: Gas Turbines: Turbomachinery

Impact of Cooling Injection on the Transonic Over-Tip Leakage Flow and Squealer Aerothermal Design Optimization

[+] Author and Article Information
Z. Wang

University of Michigan-Shanghai Jiao Tong
University Joint Institute,
Shanghai 200240, China
e-mail: wangzhaoguang1991@hotmail.com

Q. Zhang

School of Engineering
and Mathematical Sciences,
City University London,
London EC1V 0HB, UK
University of Michigan-Shanghai Jiao Tong,
University Joint Institute,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: qiang.zhang@city.ac.uk

Y. Liu

University of Michigan-Shanghai Jiao Tong
University Joint Institute,
Shanghai 200240, China
e-mail: yliume@umich.edu

L. He

Department of Engineering Science,
University of Oxford,
Oxford OX2 0ES, UK
e-mail: li.he@eng.ox.ac.uk

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 9, 2014; final manuscript received October 27, 2014; published online December 9, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(6), 062603 (Jun 01, 2015) (7 pages) Paper No: GTP-14-1541; doi: 10.1115/1.4029120 History: Received September 09, 2014; Revised October 27, 2014; Online December 09, 2014

In the present work, the effect of coolant injection on the over-tip-leakage (OTL) flow and squealer designs has been investigated in a transonic flow regime. After an experimental verification of the computational tool adopted for capturing transonic flow characteristics, a series of quasi-three-dimensional (3D) computational analyses were carried out to reveal and understand the cooling jet—OTL flow interaction at various hole locations and inclination angles. The results indicate that the performance rankings between flat tip and squealer tip designs might be altered by the addition of cooling injection. Full 3D conjugate heat transfer analyses demonstrate that partially replacing the squealer cavity with a simple flat shaped configuration in the rear transonic flow portion would offer a much improved coolability without paying extra aerodynamic penalty.

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Fig. 1

Computational domain and meshes

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Fig. 2

Grid-independence study: local OTL mass flux distribution at the exit of the tip region, obtained with three density levels of grids

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Fig. 3

Schematics of cooled/uncooled flat and squealer tip geometries investigated in the quasi-3D calculations

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Fig. 4

Shadowgraph system employed for CFD validation

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Fig. 5

(a) Shadowgraph image from experiment and (b)∇2ρ contour from CFD

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Fig. 6

Flow structures of uncooled and cooled flat tips including (a) Mach number distributions along the domain midplane and (b) streamlines and cooling jet core illustrated by Mach number

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Fig. 7

Mach number contours with secondary flow vectors along two cut-planes downstream of the cooling injection

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Fig. 8

Flow structures of uncooled and cooled squealer tips including (a) Mach number distributions along the domain midplane for uncooled and cooled squealer tips and (b) streamlines and cooling jet core illustrated by Mach number

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Fig. 9

Interactions between cooling injection and the squealer OTL flow, illustrated by a Mach number contour, streamlines from the cooling jet and incoming OTL flow, and spanwise averaged mass flux distributions

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Fig. 10

Overall OTL mass flow rate at the exit of the tip gap for all the quasi-3D cases investigated

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Fig. 11

Breakup details of mass flow rate for a cooled flat tip (α = 45 deg, near PS corner) and a cooled squealer tip (α = 60 deg, near suction side rim)

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Fig. 12

Two cooled squealer investigated in the present study: (a) full squealer and (b) partial frontal squealer

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Fig. 13

Mach number contour distribution along the tip gap exit for two tip cooling designs: (a) full squealer and (b) partial frontal squealer

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Fig. 14

Spanwise averaged mass flux distribution of the OTL flow along the gap exit (along suction surface side)

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Fig. 15

Contours of the stagnation pressure ratio (P0/P0,in) along the passage, full squealer and partial squealer

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Fig. 16

Comparisons of surface temperature ratio (Tw/T0,in) for two cooled squealer cases



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