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TECHNICAL PAPERS

Effect of Tip and Pressure Side Coolant Injection on Heat Transfer Distributions for a Plane and Recessed Tip

[+] Author and Article Information
Hasan Nasir

Mechanical Engineering Department, Louisiana State University, Baton Rouge, LA 70803

Srinath V. Ekkad1

Mechanical Engineering Department, Louisiana State University, Baton Rouge, LA 70803ekkad@me.lsu.edu

Ronald S. Bunker

 General Electric Global R&D Center, Schenectady, NY

1

Corresponding author.

J. Turbomach 129(1), 151-163 (Feb 01, 2005) (13 pages) doi:10.1115/1.2366540 History: Received October 01, 2004; Revised February 01, 2005

The present study investigates the effects of coolant injection on adiabatic film effectiveness and heat transfer coefficients from a plane and recessed tip of a high pressure turbine first stage rotor blade. Three cases where coolant is injected from (a) five orthogonal holes located along the camber line, (b) seven angled holes located near the blade tip along the pressure side, and (c) combination cases when coolant is injected from both tip and pressure side holes were studied. The pressure ratio (inlet total pressure to exit static pressure for the cascade) across the blade row was 1.2, and the experiments were run in a blow-down test rig with a four-blade linear cascade. The Reynolds number based on cascade exit velocity and axial chord length was 8.61×105 and the inlet and exit Mach numbers were 0.16 and 0.55, respectively. A transient infrared technique was used to measure adiabatic film effectiveness and heat transfer coefficient simultaneously for three blowing ratios of 1.0, 2.0, and 3.0. For all the cases, gap-to-blade span ratio of 1% was used. The depth-to-blade span ratio of 0.0416 was used for the recessed tip. Pressure measurements on the shroud were also taken to characterize the leakage flow and understand the heat transfer distributions. For tip injection, when blowing ratio increases from 1.0 to 2.0, film effectiveness increases for both plane and recessed tip and heat transfer coefficient decreases for both plane and recessed tip. At blowing ratio 3.0, lift-off is observed for both cases. In case of pressure side coolant injection and for plane tip, lift-off is observed at blowing ratio 2.0 and reattachments of jets are observed at blowing ratio 3.0. But, almost no effectiveness is observed for squealer tip at all blowing ratios with pressure side injection with reduced heat transfer coefficient along the pressure side. For combination case, very high effectiveness is observed at blowing ratio 3.0 for both plane and recessed blade tip. It appears that for this high blowing ratio, coolant jets from the tip hit the shroud first and then reattach back onto the blade tip with very high heat transfer coefficients for both plane and recessed blade tip.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Illustration of the blowdown experimental setup

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Figure 2

Cascade geometry

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Figure 3

(a) Pressure test blade and (b) shroud plate with pressure taps

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Figure 4

Film cooled blade geometry

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Figure 5

Pressure side and tip injection holes

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Figure 6

Infrared camera arrangement

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Figure 7

Surface pressure distributions on the blade surface and tip gap with 1% clearance gap (a) pressure surface (b) suction surface

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Figure 8

Effect of blowing ratio on shroud pressure distributions for a plane tip with tip injection only

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Figure 9

Effect of blowing ratio on shroud pressure distributions for a recessed tip with tip injection only

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Figure 10

Detailed film effectiveness distributions with tip injection only

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Figure 11

Detailed heat transfer coefficient distributions with tip injection only

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Figure 12

Detailed film effectiveness distributions with pressure side injection only

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Figure 13

Detailed heat transfer coefficient distributions with pressure side injection only

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Figure 14

Detailed film effectiveness distributions with combined injection

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Figure 15

Detailed heat transfer coefficient distributions with combined injection

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Figure 16

Detailed heat flux ratio distributions for plane and squealer tips with tip injection only

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Figure 17

Detailed heat flux ratio distributions for plane and squealer tips with pressure side injection only

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Figure 18

Detailed heat flux ratio distributions for plane and squealer tips with combined tip and pressure side injection

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