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Research Papers: Gas Turbines: Structures and Dynamics

Cooling Injection Effect on a Transonic Squealer Tip—Part I: Experimental Heat Transfer Results and CFD Validation

[+] Author and Article Information
H. Ma

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

Q. Zhang

Department of Mechanical Engineering
and Aeronautics,
School of Engineering
and Mathematical Sciences,
City, University of London,
Northampton Square,
London EC1V 0HB, UK
e-mail: Qiang.Zhang.1@city.ac.uk

L. He

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

Z. Wang

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

L. Wang

University of Michigan-Shanghai
Jiao Tong University Joint Institute,
Shanghai 200240, China
e-mail: lipo.wang@sjtu.edu.cn

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2016; final manuscript received October 8, 2016; published online January 10, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(5), 052506 (Jan 10, 2017) (9 pages) Paper No: GTP-16-1338; doi: 10.1115/1.4035175 History: Received July 14, 2016; Revised October 08, 2016

Recent studies have demonstrated that the aerothermal characteristics of turbine rotor blade tip under a transonic condition are qualitatively different from those under a low-speed subsonic condition. The cooling injection adds further complexity to the over-tip-leakage (OTL) transonic flow behavior and aerothermal performance, particularly for commonly studied shroudless tip configurations such as a squealer tip. However there has been no published experimental study of a cooled transonic squealer. The present study investigates the effect of cooling injection on a transonic squealer through a closely combined experimental and CFD effort. Part I of this two-part paper presents the first of the kind tip cooling experimental data obtained in a transonic linear cascade environment (exit Mach number 0.95). Transient thermal measurements are carried out for an uncooled squealer tip and six cooling configurations with different locations and numbers of discrete holes. High-resolution distributions of heat transfer coefficient and cooling effectiveness are obtained. ansysFluent is employed to perform numerical simulations for all the experimental cases. The mesh and turbulence modeling dependence is first evaluated before further computational studies are carried out. Both the experimental and computational results consistently illustrate strong interactions between the OTL flow and cooling injection. When the cooling injection (even with a relatively small amount) is introduced, distinctive series of stripes in surface heat transfer coefficient are observed with an opposite trend in the chordwise variations on the squealer cavity floor and on the suction surface rim. Both experimental and CFD results have also consistently shown interesting signatures of the strong OTL flow–cooling interactions in terms of the net heat flux reduction distribution in areas seemingly unreachable by the coolant. Further examinations and analyses of the related flow physics and underlining vortical flow structures will be presented in Part II.

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References

Figures

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Fig. 1

Transonic wind tunnel facility in the present study

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Fig. 2

Test section and the coolant supply system

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Fig. 3

IR camera calibration curve

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Fig. 4

Time histories of the inlet total pressure (P0,i), total temperature (T0,i), and coolant total pressure (P0,c) and total temperature (T0,c) during a blow-down run

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Fig. 5

Linear relationship between heat flux and wall temperature for a selected point during 2 s period of transient measurement

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Fig. 6

Contours of (a) R2 and (b) relative uncertainty for heat transfer coefficient in linear regression (%U) on the blade tip surface for the cooled case (PS9)

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Fig. 7

Computational domain and mesh employed in the present study

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Fig. 8

Contours of the relative difference in HTC between the results from two meshes for the cooled case (PS5): (a) 3 and 5 × 106 and (b) 5 and 7 × 106

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Fig. 9

Nondimensional radially averaged OTL mass flux distribution on the suction side edge of the squealer tip for the cooled case (PS5)

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Fig. 10

Contours of HTC on the blade tip surfaces obtained from experiments (EXP) and CFD using SA and k–ω SST models: (a) uncooled and (b) cooled

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Fig. 11

Circumferentially averaged HTC value: (a) uncooled and (b) cooled

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Fig. 12

Contours of HTC for cooling holes near pressure side: (a) EXP and (b) CFD

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Fig. 13

Contours of HTC for cooling holes along the camber line: (a) EXP and (b) CFD

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Fig. 14

Contours of HTC for cooling holes near suction side: (a) EXP and (b) CFD

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Fig. 15

Contours of cooling effectiveness for the nine-hole case: (a) EXP and (b) CFD

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Fig. 16

Contours of net heat flux reduction for the case with nine holes: (a) EXP and (b) CFD

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