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Research Papers

# Overall Effectiveness for a Film Cooled Turbine Blade Leading Edge With Varying Hole Pitch

[+] Author and Article Information
Thomas E. Dyson

e-mail: tedyson@gmail.com

David G. Bogard

e-mail: dbogard@mail.utexas.edu
The University of Texas at Austin,
Austin, TX 78712

Atul Kohli

Pratt & Whitney,
East Hartford, CT 06108
e-mail: atul.kohli@pw.utc.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 9, 2012; final manuscript received April 17, 2012; published online March 25, 2013. Editor: David Wisler.

J. Turbomach 135(3), 031011 (Mar 25, 2013) (8 pages) Paper No: TURBO-12-1023; doi: 10.1115/1.4006872 History: Received March 09, 2012; Revised April 17, 2012

## Abstract

Overall effectiveness, $φ$, for a simulated turbine blade leading edge was experimentally measured using a model constructed with a relatively high conductivity material selected so that the Biot number of the model matched engine conditions. The model incorporated three rows of cylindrical holes with the center row positioned on the stagnation line. Internally the model used an impingement cooling configuration. Overall effectiveness was measured for pitch variation from 7.6d to 11.6d for blowing ratios ranging from 0.5 to 3.0, and angle of attack from −7.7 deg to + 7.7 deg. Performance was evaluated for operation with a constant overall mass flow rate of coolant. Consequently when increasing the pitch, the blowing ratio was increased proportionally. The increased blowing ratio resulted in increased impingement cooling internally and increased convective cooling through the holes. The increased internal and convective cooling compensated, to a degree, for the decreased coolant coverage with increased pitch. Performance was evaluated in terms of laterally averaged $φ$, but also in terms of the minimum $φ$. The minimum $φ$ evaluation revealed localized hot spots which are arguably more critical to turbine blade durability than the laterally averaged results. For small increases in pitch (from p/d = 7.6 to 9.6) there was only a small decrease in performance, but at p/d = 11.6 a significant reduction was observed.

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## Figures

Fig. 1

Diagram of the TTCRL facility [5]

Fig. 2

Cross section of the leading edge model

Fig. 3

Typical side-view IR image showing an α of 0 deg

Fig. 4

IR calibration data for the P25 camera

Fig. 5

Contours of η for p/d = 7.6 with M = 2.0, DR = 1.5, and α = 0 deg

Fig. 6

Contours of φ for p/d = 7.6 with M = 2.0, DR = 1.5, and α = 0 deg

Fig. 7

Contours of φ for p/d values of 7.6 (a), 8.6 (b), 9.6 (c), and 11.6 (d) with M = 2.0, DR = 1.5, and α = 0 deg

Fig. 8

φ¯ comparison for M = 2.0, DR = 1.5, and α = 0 deg

Fig. 9

φmin comparison for M = 2.0, DR = 1.5, and α = 0 deg

Fig. 10

φ¯ comparison for M = 1.0, DR = 1.5, and α = 0 deg

Fig. 11

φ¯ comparison for M = 3.0, DR = 1.5, and α = 0 deg

Fig. 12

Contours of φ for p/d values of 7.6 (a), 8.6 (b), 9.6 (c), and 11.6 (d) with M = 3.0, DR = 1.5, and α = 0 deg

Fig. 13

φmin comparison for M = 3.0, DR = 1.5, and α = 0 deg

Fig. 14

φ¯ comparison for M = 2.0, DR = 1.5, and α = 4.6 deg

Fig. 15

¯¯φ as a function of the coolant mass flow rate per pitch

Fig. 16

φmin averaged over 0 < x/d < 8

Fig. 17

Local φ at x/d = 2 for all pitches at M = 2, DR = 1.5, and α = 0 deg

Fig. 18

Variations of φ¯ and φmin with pitch between holes at x/d = 2

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