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Research Papers: Gas Turbines: Turbomachinery

Squealer Tip Leakage Flow Characteristics in Transonic Condition

[+] Author and Article Information
Wei Li

e-mail: lidavid2013@gmail.com

Hongmei Jiang

e-mail: Jianghm188@163.com

Qiang Zhang

e-mail: qzhang@sjtu.edu.cn
University of Michigan-Shanghai,
Jiao Tong University Joint Institute,
UM-SJTU JI, 800 Dongchuan Road,
Minhang District, Shanghai, China

Sang Woo Lee

Department of Mechanical Engineering,
Kumoh National Institute of Technology,
1 Yangho-dong, Gumi,
Gyeongbuk 730-701, China
e-mail: swlee@kumoh.ac.kr

1Corresponding author.

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 24, 2013; final manuscript received October 28, 2013; published online December 10, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(4), 042601 (Dec 10, 2013) (7 pages) Paper No: GTP-13-1385; doi: 10.1115/1.4025918 History: Received October 24, 2013; Revised October 28, 2013

The over-tip-leakage (OTL) flow characteristics for a typical squealer tip of a high-pressure turbine blade, which consists of subsonic and transonic flow, have been numerically investigated in the present study, in comparison with the corresponding flat tip results. For the squealer tip employed, flow choking behavior still exists above the tip surface, even though the Mach number is lower and the transonic region is smaller than that for the flat tip. Detailed flow structure analysis shows that most of the fluid entering the squealer cavity is from the frontal leading edge region. The fluid migrates along the cavity and is ejected at various locations near the suction side rim. These fluids form a large subsonic flow zone under the supersonic flow passing over the tip gap which reduces the OTL flow flux. The squealer design works even in the presence of choked OTL flow. Comparisons between results from three different cavity depths with and without relative casing motion suggest that the over-tip-leakage flow flux has much dependence upon the cavity depth for the subsonic region, but is less sensitive to the depth for the transonic tip flow region. Such behavior has been confirmed with and without the existence of relative casing motion.

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References

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Figures

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Fig. 1

Computational domain and mesh

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Fig. 2

Isentropic Mach number distributions at the midspan of the blade

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Fig. 3

Local Mach number contours in the middle of tip gap for a flat tip and a squealer tip

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Fig. 4

Mach number distributions for a cut plane near the leading edge region of a (a) flat tip and (b) squealer tip

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Fig. 5

Mach number contours for a cut plane near the rear part of the blade for a (a) flat tip and (b) squealer tip

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Fig. 6

Mach number contours along the curved surface on the tip suction side

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Fig. 7

Mass flux distributions along the curve length of the suction side edge shown in Fig. 6

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Fig. 8

Total pressure loss coefficient distributions along axial chord of the blade

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Fig. 9

Streamlines near the squealer tip cavity

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Fig. 10

Flow flux ρVZ contour along tip surface

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Fig. 11

(a) Surface streamlines on the cavity floor in the present study, and (b) oil-film visualization on the cavity floor [10]

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Fig. 12

Mach number distributions along the curved surface on the squealer tip suction side for cases with three different cavity depths

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Fig. 13

OTL mass flux contours along the suction side edge for squealers with cavity depth of 1.3H and 3.0H

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Fig. 14

OTL mass flux distributions along the suction side edge for squealers with three different cavity depths with and without relative casing motion

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Fig. 15

Mach number distributions for cut planes near the frontal region of the squealer tip

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