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Research Papers

Experimental and Numerical Crossover Jet Impingement in a Rib-Roughened Airfoil Trailing-Edge Cooling Channel

[+] Author and Article Information
M. E. Taslim

e-mail: m.taslim@neu.edu

M. K. H. Fong

Mechanical and Industrial Engineering Department,
Northeastern University,
Boston, MA 02115

Manuscript received July 5, 2011; final manuscript received September 17, 2012; published online June 28, 2013. Assoc. Editor: Je-Chin Han.

J. Turbomach 135(5), 051014 (Jun 28, 2013) (10 pages) Paper No: TURBO-11-1100; doi: 10.1115/1.4023459 History: Received July 05, 2011; Revised September 17, 2012

Local and average heat transfer coefficients were measured in a test section simulating a rib-roughened trailing edge cooling cavity of a turbine airfoil. The test rig was made up of two adjacent channels, each with a trapezoidal cross sectional area. The first channel, simulating the cooling cavity adjacent to the trailing-edge cavity, supplied the cooling air to the trailing-edge channel through a row of racetrack-shaped slots on the partition wall between the two channels. Eleven crossover jets, issued from these slots entered the trailing-edge channel, impinged on eleven radial ribs and exited from a second row of race-track shaped slots on the opposite wall in staggered or inline arrangement. Two jet angles of 0 deg and 5 deg and a range of jet Reynolds number from 10,000 to 35,000 were tested and compared. The numerical models contained the entire trailing-edge and supply channels with all slots and ribs to simulate exactly the tested geometries. They were meshed with all-hexa structured mesh of high near-wall concentration. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. The realizable k-ε turbulence model was employed in combination with an enhanced wall treatment approach for the near wall regions. Boundary conditions identical to those of the experiments were applied and several turbulence model results were compared. The numerical analyses also provided the share of each crossover and each exit hole from the total flow for different geometries. The major conclusions of this study were: (a) except for the first and last cross-flow jets, which had different flow structures, other jets produced the same heat transfer results on their target surfaces; (b) tilted crossover jets produced higher heat transfer coefficients on the target surface towards which they were tilted and lower values on the opposite surface, and (c) the numerical predictions of impingement heat transfer coefficients were in good agreement with the measured values for most cases thus CFD could be considered a viable tool in airfoil cooling circuit designs.

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Figures

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Fig. 1

Schematics of the rig

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Fig. 2

Details of the test section

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Fig. 3

A typical mesh for the entire test section with the crossover and exit holes

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Fig. 4

Details of the mesh around a crossover and a trailing-edge slot for inline and staggered flow arrangements

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Fig. 5

Typical CFD contours of velocity magnitude on the rig midplane for inline arrangement with 0 deg tilt angle and for staggered arrangement with 5 deg tilt angle

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Fig. 20

Comparison of the k–ε, k–ω, and v2f turbulence models with the test results for the 5 deg tilt angle, staggered arrangement, and four blocked exit holes

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Fig. 19

Contours of velocity magnitude on the planes cutting the crossover and exit holes in the middle of the trailing-edge channel for the inline and staggered flow arrangements.

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Fig. 18

Comparison of the CFD and test results on the target and opposite walls for the 5 deg tilt angle, inline, and staggered flow arrangements

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Fig. 17

Comparison of the CFD and test results for the 5 deg tilt angle and staggered flow arrangement

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Fig. 16

Comparison of the CFD and test results for the 5 deg tilt angle and inline flow arrangement

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Fig. 15

Comparison of the CFD and test results for the 0 deg tilt angle and staggered flow arrangement

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Fig. 14

Comparison of the CFD and test results for the 0 deg tilt angle and inline flow arrangement

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Fig. 13

Measured Nusselt number variation with local jet Reynolds number on areas 1 through 5 for the 5 deg tilt angle, four blocked exit holes, and open end hole

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Fig. 12

Measured Nusselt number variation with local jet Reynolds number on areas 1 through 5 for the 5 deg tilt angle, 2 blocked exit holes, and open end hole

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Fig. 11

Measured contours of Nusselt numbers on area 6 for 0 deg tilt angle, and for inline and staggered flow arrangements

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Fig. 10

Typical CFD contours of Nusselt numbers on the floor and rib surfaces of area 6 for 0 deg and 5 deg tilt angles, and for inline and staggered flow arrangements

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Fig. 9

Measured versus CFD Nusselt number variation with local jet number on area 6, no blocked exit hole

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Fig. 8

Percentage of mass flow rates through the exit holes

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Fig. 7

Percentage of mass flow rate through the crossover holes with all exit holes open

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Fig. 6

Typical CFD contours of velocity magnitude on the rig midplane for zer, two, and four blocked exit holes, staggered flow arrangement, and 5 deg tilt angle

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Fig. 21

Measured pressure ratios across the crossover holes and across the trailing-edge channel for all geometries and flow arrangements

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