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Research Papers

Film-Cooling Effectiveness on a Rotating Blade Platform

[+] Author and Article Information
A. Suryanarayanan, S. P. Mhetras, M. T. Schobeiri, J. C. Han

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

J. Turbomach 131(1), 011014 (Oct 28, 2008) (12 pages) doi:10.1115/1.2752184 History: Received September 18, 2006; Revised October 17, 2006; Published October 28, 2008

Film cooling effectiveness measurements under rotation were performed on the rotor blade platform using a pressure sensitive paint (PSP) technique. The present study examines, in particular, the film cooling effectiveness due to purging of coolant from the wheel-space cavity through the circumferential clearance gap provided between the stationary and rotating components of the turbine. The experimental investigation is carried out in a new three-stage turbine facility, recently designed and taken into operation at the Turbomachinery Performance and Flow Research Laboratory (TPFL) of Texas A&M University. This new turbine rotor has been used to facilitate coolant injection through this stator-rotor gap upstream of the first stage rotor blade. The gap was inclined at 25deg to mainstream flow to allow the injected coolant to form a film along the passage platform. The effects of turbine rotating conditions on the blade platform film cooling effectiveness were investigated at three speeds of 2550rpm, 2000rpm, and 1500rpm with corresponding incidence angles of 23.2deg, 43.4deg, and 54.8deg, respectively. Four different coolant-to-mainstream mass flow ratios varying from 0.5% to 2.0% were tested at each rotational speed. Aerodynamic measurements were performed at the first stage stator exit using a radially traversed five-hole probe to quantify the mainstream flow at this station. Results indicate that film cooling effectiveness increases with an increase in the coolant-to-mainstream mass flow ratios for all turbine speeds. Higher turbine rotation speeds show more local film cooling effectiveness spread on the platform with increasing magnitudes.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The overall layout of TPFL-research turbine facility, from Schobeiri (1-3)

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Figure 2

Section view of the modified stator-rotor turbine assembly

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Figure 3

Detailed view of the stator-rotor gap

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Figure 4

Turbine component with the 24-channel slip ring, casing cavity, and the front bearing

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Figure 5

Schematic view of the stator-rotor gap design for the rotating endwall

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Figure 6

Calibration curve for PSP

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Figure 7

Optical components setup for the model turbine and PSP

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Figure 8

Radial distribution of stator exit flow angle for varying rotor speeds

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Figure 9

Radial distribution of total pressure for varying rotor speeds

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Figure 10

Radial distribution of absolute velocity for varying rotor speeds

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Figure 11

Film cooling effectiveness distribution on the rotating platform for 2550rpm

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Figure 12

Velocity triangles and relative inlet and exit flow angles for design and off design rotating speeds

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Figure 13

Numerical prediction of platform static pressure distribution (Pa) along with flow pathlines

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Figure 14

Film cooling effectiveness distribution on the rotating platform for 2000rpm

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Figure 15

Film cooling effectiveness distribution on the rotating platform for 1500rpm

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Figure 16

Pitchwise averaged film cooling effectiveness distribution along axial chord for different turbine rotating speeds (mass flow ratio effect)

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Figure 17

Pitchwise averaged film cooling effectiveness distribution along axial chord for different mass flow ratios (turbine rotation speed effect)

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Figure 18

Comparison of pitchwise average effectiveness with a correlation from Goldstein [48] for different rpm

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