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Research Papers

Effect of Inlet Flow Angle on Gas Turbine Blade Tip Film Cooling

[+] Author and Article Information
Zhihong Gao, Diganta Narzary, Shantanu Mhetras

Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123

Je-Chin Han

Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123jc-han@tamu.edu

J. Turbomach 131(3), 031005 (Apr 08, 2009) (12 pages) doi:10.1115/1.2987235 History: Received July 12, 2007; Revised December 13, 2007; Published April 08, 2009

The influence of incidence angle on film-cooling effectiveness is studied for a cutback squealer blade tip. Three incidence angles are investigated 0deg at design condition and ±5deg at off-design conditions. Based on mass transfer analogy, the film-cooling effectiveness is measured with pressure sensitive paint techniques. The film-cooling effectiveness distribution on the pressure side near tip region, squealer cavity floor, and squealer rim tip is presented for the three incidence angles at varying blowing ratios. The average blowing ratio is controlled to be 0.5, 1.0, 1.5, and 2.0. One row of shaped holes is provided along the pressure side just below the tip; two rows of cylindrical film-cooling holes are arranged on the blade tip in such a way that one row is offset to the suction side profile and the other row is along the camber line. The pressure side squealer rim wall is cut near the trailing edge to allow the accumulated coolant in the cavity to escape and cool the tip trailing edge. The internal coolant-supply passages of the squealer tipped blade are modeled similar to those in the GE-E3 rotor blade. Test is done in a five-blade linear cascade in a blow-down facility with a tip gap clearance of 1.5% of the blade span. The Mach number and turbulence intensity level at the cascade inlet were 0.23 and 9.7%, respectively. It is observed that the incidence angle affects the coolant jet direction on the pressure side near tip region and the blade tip. The film-cooling effectiveness distribution is also altered. The peak of laterally averaged effectiveness is shifted upstream or downstream depending on the off-design incidence angle. The film cooling effectiveness inside the tip cavity can increase by 25% with the positive incidence angle. However, in general, the overall area-averaged film-cooling effectiveness is not significantly changed by the incidence angles in the range of study.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 9

Stream vectors along with dimensionless temperature contours for three cross sections along the tip (9)

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Figure 10

Pressure ratio at the pressure side near tip region at different incidence angles and blowing ratios

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Figure 11

Pressure ratio at the blade rip at different incidence angles and blowing ratios

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Figure 12

Local blowing ratio for various incidence angles

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Figure 13

Film-cooling effectiveness for the near tip pressure side at different incidence angles

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Figure 14

Film-cooling effectiveness on the blade tip at different incidence angles

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Figure 15

Laterally averaged film-cooling effectiveness on the pressure side and cavity floor

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Figure 16

Laterally averaged film-cooling effectiveness on the pressure side rim and suction side rim

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Figure 1

Schematic of the test section and blow-down facility

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Figure 2

Definition of the blade tip and shroud

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Figure 3

(a) Test section and (b) flow angles

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Figure 6

Detailed geometry of a PS shaped hole

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Figure 7

Calibration curve for PSP

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Figure 8

Pressure ratios for different inlet flow angles without coolant injection

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Figure 17

Area averaged film-cooling effectiveness

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Figure 4

Internal passage geometry of the test blade

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Figure 5

Orientation of the tip and PS holes

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