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Research Papers

Experimental/Numerical Crossover Jet Impingement in an Airfoil Leading-Edge Cooling Channel

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

Mechanical and Industrial
Engineering Department
Northeastern University
Boston, MA 02115

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 27, 2011; final manuscript received August 7, 2011; published online October 31, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011037 (Oct 31, 2012) (12 pages) Paper No: TURBO-11-1163; doi: 10.1115/1.4006420 History: Received July 27, 2011; Revised August 07, 2011

Technological advancement in the gas turbine field demands high temperature gases impacting on the turbine airfoils in order to increase the output power as well as thermal efficiency. The leading edge is one of the most critical and life limiting sections of the airfoil which requires intricate cooling schemes to maintain a robust design. In order to maintain coherence with a typical external aerodynamic blade profile, cooling processes usually take place in geometrically-complex internal paths where analytical approaches may not provide a proper solution. In this study, experimental and numerical models simulating the leading-edge and its adjacent cavity were created. Cooling flow entered the leading-edge cavity through the crossover ports on the partition wall between the two cavities and impinged on the internal surface of the leading edge. Three flow arrangements were tested: (1) and (2) being flow entering from one side (root or tip) of the adjacent cavity and emerging from either the same side or the opposite side of the leading-edge cavity, and (3) flow entering from one side of the adjacent cavity and emerging from both sides of the leading-edge cavity. These flow arrangements were tested for five crossover-hole settings with a focus on studying the heat transfer rate dependency on the axial flow produced by upstream crossover holes (spent air). Numerical results were obtained from a three-dimensional unstructured computational fluid dynamics model with 1.1 × 106 hexahedral elements. For turbulence modeling, the realizable k-ε was employed in combination with the enhanced wall treatment approach for the near wall regions. Other available RANS turbulence models with similar computational cost did not produce any results in better agreement with the measured data. Nusselt numbers on the nose area and the pressure/suction sides are reported for jet Reynolds numbers ranging from 8000 to 55,000 and a constant crossover hole to the leading-edge nose distance ratio, Z/Dh, of 2.81. Comparisons with experimental results were made in order to validate the employed turbulence model and the numerically-obtained results. Results show a significant dependency of Nusselt number on the axial flow introduced by upstream jets as it drastically diminishes the impingement effects on the leading-edge channel walls. Flow arrangement has immense effects on the heat transfer results. Discrepancies between the experimental and numerical results averaged between +0.3% and −24.5%; however, correlation between the two can be clearly observed.

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References

Figures

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Fig. 1

Schematic of the test rig

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Fig. 2

Tested crossover-holes geometries

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Fig. 3

Schematic of the tested flow arrangements

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Fig. 4

Numerical grid including nine crossover holes and inlet/outlet ports

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Fig. 5

Detailed mesh around the root end

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Fig. 6

CFD results on the symmetry plane, parallel flow arrangement

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Fig. 7

Percentage of total flow through each crossover hole, parallel flow arrangement

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Fig. 8

Pressure ratios across the crossover holes and across the leading-edge channel for the parallel flow arrangement

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Fig. 9

Comparison between the measured versus CFD heat transfer results on nose and side areas under crossover holes no. 5 for the parallel flow arrangement

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Fig. 10

CFD heat transfer results for the parallel flow arrangement with five experimental data points for area 5

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Fig. 11

CFD contours of Nusselt number for the five crossover hole geometries and the parallel flow arrangement

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Fig. 12

CFD streamlines for the five crossover hole geometries and the parallel flow arrangement

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Fig. 13

Iso-surfaces of the Y and Z velocities

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Fig. 14

Percentage of total flow through each crossover hole, circular flow arrangement

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Fig. 15

Pressure ratios across the crossover holes and across the leading-edge channel for the circular flow arrangement

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Fig. 16

Comparison between the measured versus CFD heat transfer results on nose and side areas under crossover hole no. 5 for circular flow arrangement

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Fig. 17

Contours of Nusselt number in the circular flow arrangement for all tested geometries

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Fig. 18

CFD heat transfer results for the circular flow arrangement with five experimental data points for area 5

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Fig. 19

Percentage of total flow through each crossover hole, 1inlet-2outlet flow arrangement

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Fig. 20

Pressure ratios across the crossover holes and across the leading-edge channel for the 1inlet-2outlet flow arrangement

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Fig. 21

Comparison between the measured versus CFD heat transfer results on nose and side areas under crossover hole no. 5 for 1 inlet-2 outlet flow arrangement

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Fig. 22

Contours of Nusselt number in the 1inlet-2outlet flow arrangement for all tested geometries

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Fig. 23

CFD heat transfer results for the 1inlet-2outlet flow arrangement with five experimental data points for area no. 5

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