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Research Papers

Cooling Effectiveness for a Shaped Film Cooling Hole at a Range of Compound Angles

[+] Author and Article Information
Shane Haydt

Mechanical and Nuclear
Engineering Department,
The Pennsylvania State University,
University Park, PA 16802

Stephen Lynch

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

1Present address: United Technologies—Pratt & Whitney, East Hartford, CT 06108.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 7, 2018; final manuscript received September 27, 2018; published online January 21, 2019. Editor: Kenneth Hall.

J. Turbomach 141(4), 041005 (Jan 21, 2019) (14 pages) Paper No: TURBO-18-1238; doi: 10.1115/1.4041603 History: Received September 07, 2018; Revised September 27, 2018

Shaped film cooling holes are a well-established cooling technique used in gas turbines to keep component metal temperatures in an acceptable range. One of the goals of film cooling is to reduce the driving temperature for convection at the wall, the success of which is generally represented by the film cooling adiabatic effectiveness. However, the introduction of a film cooling jet-in-crossflow, especially if it is oriented at a compound angle, can augment the convective heat transfer coefficient and dominate the flowfield. This work aims to understand the effect that a compound angle has on the flowfield and adiabatic effectiveness of a shaped film cooling hole. Five orientations of the public 7–7–7 shaped film cooling hole were tested, from a streamwise-oriented hole (0 deg compound angle) to a 60 deg compound angle hole, in increments of 15 deg. Additionally, two pitchwise spacings of P/D = 3 and 6 were tested to examine the effect of hole-to-hole interaction. All cases were tested at a density ratio of 1.2 and blowing ratios ranging from 1.0 to 4.0. The experimental results show that increasing compound angle leads to increased lateral spread of coolant and enables higher laterally averaged effectiveness at high-blowing ratios. A smaller pitchwise spacing leads to more complete coverage of the endwall and has higher laterally averaged effectiveness even when normalized by coverage ratio, suggesting that hole to hole interaction is important for compound angled holes. Steady Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) was not able to capture the exact effectiveness levels, but did predict many of the observed trends. The lateral motion of the coolant jet was also quantified, both from the experimental data and the CFD prediction, and as expected, holes with a higher compound angle and higher blowing ratio have greater lateral motion, which generally also promotes hole-to-hole interaction.

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References

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Figures

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Fig. 1

7–7–7 baseline shaped film cooling hole, developed by Schroeder and Thole [1]

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Fig. 2

A shaped film cooling hole oriented at different compound angles, left, and at different pitchwise spacings, right

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Fig. 3

Closed-loop wind tunnel facility

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Fig. 4

The CA30 hole has good periodicity when averaged based on the path of the jet (black lines), rather than a rectangle (white lines)

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Fig. 5

Laterally averaged effectiveness for the case shown in Fig. 4. Solid lines are rectangularly averaged, and dashed lines are averaged based on the path of the coolant jet.

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Fig. 6

Computational domain made in Pointwise for simulated cases run in ANSYS fluent

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Fig. 7

Grid independence study for the 60 deg compound angled hole at M = 2.0

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Fig. 8

Laterally averaged effectiveness for all five compound angled cases at M = 1.0

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Fig. 9

Adiabatic effectiveness contours for all compound angles at M = 1.0

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Fig. 10

Local adiabatic effectiveness versus lateral distance, z'/D, for all compound angle cases at M = 1.0

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Fig. 11

Laterally averaged effectiveness for all five compound angled cases at M = 3.0

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Fig. 12

Adiabatic effectiveness contours for all compound angles at M = 3.0

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Fig. 13

Local adiabatic effectiveness versus lateral distance, z'/D, for all compound angle cases at M = 3.0

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Fig. 14

Laterally averaged effectiveness for all blowing ratios of the 0 deg (solid lines) and 60 deg (dashed lines) cases

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Fig. 15

Adiabatic effectiveness contours for the CA60 hole at all blowing ratios

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Fig. 16

Local adiabatic effectiveness versus lateral distance, z'/D, for all blowing ratio cases of the CA60 hole

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Fig. 17

Local adiabatic effectiveness versus lateral distance, z'/D, for all blowing ratio cases of the streamwise-oriented 7–7–7 hole

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Fig. 18

Area-averaged effectiveness for all P/D = 6 cases, and a CA45 case from Anderson et al. [23], plotted versus the streamwise component of blowing ratio

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Fig. 19

Laterally averaged effectiveness for all P/D = 3 compound angle cases at M = 1.0

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Fig. 20

Adiabatic effectiveness contours for all P/D = 3 compound angle cases at M = 1.0

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Fig. 21

Laterally averaged effectiveness for all P/D = 3 compound angle cases at M = 3.0

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Fig. 22

Adiabatic effectiveness contours for all P/D = 3 compound angle cases at M = 3.0

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Fig. 23

Laterally averaged effectiveness for a CA0 streamwise-oriented hole (solid lines) and a CA45 hole (dashed lines) at all blowing ratios, both with P/D = 3

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Fig. 24

Adiabatic effectiveness contours for the P/D = 3 CA45 hole at all blowing ratios

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Fig. 25

Area-averaged effectiveness normalized by breakout width over pitch for all cases tested, plotted versus blowing ratio. Precision uncertainty is indicated by size of symbols.

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Fig. 26

Adiabatic effectiveness contours for selected examples with the same compound angle and blowing ratio, but different pitch

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Fig. 27

Paths of coolant jet maximum η for selected P/D = 6 cases

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Fig. 28

Paths of coolant jet maximum η for selected P/D = 3 cases

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Fig. 31

CFD simulations for the CA15 and CA45 holes at M = 1.0, contoured with adiabatic effectiveness and with an isosurface at q-criterion of 5000

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Fig. 30

CFD simulations for a sweep of compound angles at M = 2.0, x/D = 0. Contours of normalized x-vorticity overlaid with a line contour of q-criterion = 5000.

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Fig. 29

CFD simulations for a sweep of compound angles at M = 2.0. Contours of adiabatic effectiveness and isosurfaces of q-criterion at a value of 5000.

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