Research Papers

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

[+] Author and Article Information
Shane Haydt

Mechanical and Nuclear
Engineering Department,
The Pennsylvania State University,
University Park, PA 16802
e-mail: shane.haydt@psu.edu

Stephen Lynch

Mechanical and Nuclear
Engineering Department,
The Pennsylvania State University,
University Park, PA 16802
e-mail: splynch@psu.edu

Scott Lewis

Turbine Durability,
United Technologies—Pratt & Whitney,
400 Main Street,
East Hartford, CT 06108
e-mail: Scott.Lewis@pw.utc.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received November 18, 2016; final manuscript received February 28, 2017; published online May 2, 2017. Editor: Kenneth Hall.

J. Turbomach 139(9), 091012 (May 02, 2017) (10 pages) Paper No: TURBO-16-1299; doi: 10.1115/1.4036199 History: Received November 18, 2016; Revised February 28, 2017

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining (EDM), and occasionally, an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady Reynolds-averaging Navier–Stokes (RANS) predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset's improved performance.

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Fig. 1

Schematic of wind tunnel facility used in current study [17]

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Fig. 2

Baseline 7-7-7 hole geometry [6]

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Fig. 3

Meter-diffuser offset directions tested in this study

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Fig. 4

The metering section is created first, and then the diffuser is offset from the its centerline

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Fig. 5

(a) Centerline and laterally averaged effectiveness for three meshes of the same geometry and (b) five different monitors are plotted versus CFD iterations to show solution convergence

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Fig. 6

CFD domain with boundary conditions and a depiction of the mesh resolution at the centerline

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Fig. 7

Adiabatic effectiveness contours for the baseline 7-7-7 hole at DR = 1.2, measured in this study

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Fig. 8

Baseline 7-7-7 hole laterally averaged effectiveness, with data from Schroeder and Thole [6]

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Fig. 9

Effectiveness contours for all 1/4D offset directions, at M = 1.0

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Fig. 10

Laterally averaged effectiveness for all 1/4D offset directions, at M = 1.0

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Fig. 11

Adiabatic effectiveness contours for representative offset cases at M = 1.0 and DR = 1.2

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Fig. 12

Laterally averaged effectiveness for representative cases at M = 1.0

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Fig. 13

Area-averaged effectiveness, averaged from x/D = 3 to 15, for three offset directions at all blowing ratios

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Fig. 14

Adiabatic effectiveness contours for the left 1/4D offset

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Fig. 15

Area-averaged effectiveness, averaged from x/D = 3 to 15, for all cases (experimental uncertainty indicated)

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Fig. 16

Adiabatic effectiveness contours for CFD and experimental data, at M = 2.0

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Fig. 17

Laterally averaged effectiveness for three cases, both experimental and CFD, all at M = 2.0

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Fig. 18

Area-averaged effectiveness for both CFD and experimental data at M = 2.0

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Fig. 19

Contour plots of nondimensionalized velocity magnitude at the centerline plane of the hole

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Fig. 20

Contour plots of nondimensionalized velocity magnitude at the exit plane of the film cooling hole

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Fig. 21

Contours of time-mean streamwise velocity, and u′v′¯ turbulent shear stress in the centerline plane for DR = 1.5, M = 3.0 for the baseline 7-7-7 hole, from Schroeder and Thole [20]

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Fig. 22

Predicted nondimensional temperature contours at the centerline plane for each 1/4D offset case at M = 2.0

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Fig. 23

Predicted contours of nondimensional temperature and streamlines of in-plane velocity plotted on a plane normal to the main flow direction at x/D = 5 downstream from the hole trailing edge, for all 1/4D offsets at M = 2.0



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