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Research Papers: Gas Turbines: Turbomachinery

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

[+] Author and Article Information
Zhaofang Liu, Zhao Liu

Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China

Zhenping Feng

Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: zpfeng@mail.xjtu.edu.cn

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received January 16, 2014; final manuscript received January 27, 2014; published online February 28, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(8), 082605 (Feb 28, 2014) (11 pages) Paper No: GTP-14-1033; doi: 10.1115/1.4026805 History: Received January 16, 2014; Revised January 27, 2014

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5%, and 2.5% of the blade span with a flat tip were investigated, respectively, and the uniform and nonuniform inlet temperature profiles were taken as the inlet boundary conditions. A new method for heat transfer coefficient calculation recommended by Maffulli and He has been adopted. By solving the unsteady compressible Reynolds-averaged Navier–Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on the blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. Because it is possible for heat transfer coefficient distributions to be greatly different from heat flux distributions, it becomes of great concern to combine both of them in consideration of hot streak migration. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Copyright © 2014 by ASME
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Figures

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Fig. 1

Geometry of the first stage of the GE-E3 turbine

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Fig. 2

Circumferential mass averaged total temperature distribution at the turbine inlet in the radial direction

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Fig. 3

Heat transfer coefficient distributions on blade tips for experimental and predicted results

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Fig. 4

Heat transfer coefficient distributions on blade tips for different meshes

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Fig. 5

Computational domain grids

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Fig. 6

Periodic variation of mass flow, pressure, and temperature separately at four monitoring points: (a) mass flow at the outlet of the stage; (b) tip pressure at the leading and trailing edge (purple line: leading edge, green line: trailing edge); and (c) temperature at the middle of the rotor passage

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Fig. 7

Pressure distribution on the blade surface at 95% of the blade span (AC: axial chord)

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Fig. 8

T distribution in the middle surface of the tip clearance

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Fig. 9

Streamlines and temperature distributions at different ACs at t1 in case no. 2 (left is pressure side)

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Fig. 10

Heat transfer coefficient distribution on the rotor blade tip. (a) The distributions of hq on the rotor blade tip and (b) the distributions of h on the rotor blade tip.

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Fig. 11

Streamline variation with time at 50% AC near the tip region (left is pressure side)

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Fig. 12

Time-space plots of heat transfer coefficient at 50% AC on the rotor blade tip (PS: pressure side, SS: suction side). (a) The distributions of hq on rotor blade tip, and (b) the distributions of h on rotor blade tip.

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Fig. 13

Pressure distribution on the blade surface at 95% of the blade span

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Fig. 14

T distribution in the middle surface of the tip clearance

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Fig. 15

The distributions of hq on rotor blade tip

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