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Research Papers

Evaluation of CFD Predictions Using Thermal Field Measurements on a Simulated Film Cooled Turbine Blade Leading Edge

[+] Author and Article Information
Sibi Mathew

The University of Texas at Austin,
Austin, TX, 78712
e-mail: sibimathew86@gmail.com

Silvia Ravelli

University of Bergamo,
Bergamo, Italy, 24044
e-mail: silvia.ravelli@unibg.it

David G. Bogard

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

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 12, 2011; final manuscript received August 19, 2011; published online October 30, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011021 (Oct 30, 2012) (10 pages) Paper No: TURBO-11-1133; doi: 10.1115/1.4006397 History: Received July 12, 2011; Revised August 19, 2011

Computational fluid dynamics (CFD) predictions of film cooling performance for gas turbine airfoils are an important part of the design process for turbine cooling. Typically, industry relies on the approach based on Reynolds Averaged Navier Stokes equations, together with a two-equation turbulence model. The realizable k-ɛ (RKE) model and the shear stress transport k-ω (SST) model are recognized as the most reliable. Their accuracy is generally assessed by comparing to experimentally measured adiabatic effectiveness. In this study, the performances of the RKE and SST models were evaluated by comparing predicted and measured thermal fields in a turbine blade leading edge with three rows of cooling holes, positioned along the stagnation line and at ±25 deg. Predictions and measurements were done with high thermal conductivity models which simulated the conjugate heat transfer effects between the coolant flow and the solid. Particular attention was placed on the thermal fields along the stagnation line, and immediately downstream of the off-stagnation line row of holes. Conventional evaluations in terms of adiabatic effectiveness were also carried out. Predictions of coolant flows at the stagnation line were significantly different when using the two different turbulence models. For a blowing ratio of M = 2.0, the predictions with the SST model showed coolant jet separation at the stagnation line, while the RKE predictions showed no separation. Experimental measurements showed that there was coolant jet separation at the stagnation line, but the actual thermal fields obtained from experimental measurements were significantly different from that predicted by either turbulence model. Similar results were seen for predicted and measured thermal fields downstream of the off-stagnation row of holes.

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References

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Figures

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Fig. 1

Schematic of the wind tunnel facility

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Fig. 2

Side view of the leading edge model

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Fig. 3

Schematic of the thermocouple probe with the traverse system

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Fig. 4

Repeatability tests for normalized temperature measurements

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Fig. 5

Schematic of the 3D computational domain

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Fig. 6

Grid resolution at the symmetry plane for the: (a) coarse mesh, (b) fine mesh

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Fig. 7

Predicted versus measured laterally averaged adiabatic effectiveness

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Fig. 8

Predicted surface contours of adiabatic effectiveness according to RKE and SST models compared with experimental data

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Fig. 9

Predicted versus measured adiabatic effectiveness at stagnation line (x/d = 0)

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Fig. 10

Predicted versus measured adiabatic effectiveness at x/d = 5.1

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Fig. 11

Adiabatic versus conducting normalized temperature profile at x/d = 0 and z/d = 2.5

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Fig. 12

Predicted normalized temperature contours along stagnation plane, according to SST model, RKE model compared with experimental data

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Fig. 13

Predicted versus measured normalized temperature profile along stagnation plane at (a) z/d = 0, (b) z/d = 2, (c) z/d = 4

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Fig. 14

Predicted velocity vectors colored by normalized temperature along stagnation plane, according to SST model and RKE model

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Fig. 15

Predicted turbulence intensity contours along stagnation plane, according to SST model and RKE model

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Fig. 16

Predicted normalized temperature contours along x/d = 2 plane according to (a) SST model and (b) RKE model

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Fig. 17

Predicted normalized temperature contours along x/d = 5.1 plane according to SST model, RKE model compared with experimental data

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Fig. 18

Predicted versus measured normalized temperature profile along x/d = 5.1 plane at (a) z/d = 2.9, (b) z/d = 4.9

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