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Research Papers

Effect of In-Hole Roughness on Film Cooling From a Shaped Hole

[+] Author and Article Information
Robert P. Schroeder

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: rschroeder@sargentlundy.com

Karen A. Thole

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

1Present address: Sargent and Lundy, Chicago, IL 60603.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 16, 2016; final manuscript received September 1, 2016; published online November 16, 2016. Editor: Kenneth Hall.

J. Turbomach 139(3), 031004 (Nov 16, 2016) (9 pages) Paper No: TURBO-16-1195; doi: 10.1115/1.4034847 History: Received August 16, 2016; Revised September 01, 2016

Abstract

While much is known about how macrogeometry of shaped holes affects their ability to successfully cool gas turbine components, little is known about the influence of surface roughness on cooling hole interior walls. For this study, a baseline-shaped hole was tested with various configurations of in-hole roughness. Adiabatic effectiveness measurements at blowing ratios up to 3 showed that the in-hole roughness caused decreased adiabatic effectiveness relative to smooth holes. Decreases in area-averaged effectiveness grew more severe with larger roughness size and with higher blowing ratios for a given roughness. Decreases of more than 60% were measured at a blowing ratio of 3 for the largest roughness values. Thermal field and flowfield measurements showed that in-hole roughness caused increased velocity of core flow through the hole, which increased the jet penetration height and turbulence intensity resulting in an increased mixing between the coolant and the mainstream. Effectiveness reductions due to roughness were also observed when roughness was isolated to only the diffused outlet of holes, and when the mainstream was highly turbulent.

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Figures

Fig. 1

Schematic of the film cooling wind tunnel

Fig. 2

Geometry of the shaped hole

Fig. 3

Three-dimensional maps of roughness in metering sections of the (a) smooth hole and (b) rough hole configurations. Note that overall form of the surface has been removed, as done for roughness calculation.

Fig. 4

Laterally averaged adiabatic effectiveness at M = 1.0 for configurations with increasing size of in-hole roughness

Fig. 5

Contours of adiabatic effectiveness for (a) smooth holes, M = 1.5; (b) slightly rough holes, M = 1.5; (c) rough holes, M = 1.5; (d) rough diffuser holes, M = 1.5 and (e) smooth holes, M = 3.0; (f) slightly rough holes, M = 3.0; (g) rough holes, M = 3.0; and (h) rough diffuser holes, M = 3.0. Center hole in the row of five is shown.

Fig. 6

Laterally averaged adiabatic effectiveness at M = 1.5 for different in-hole roughness configurations

Fig. 7

Laterally averaged adiabatic effectiveness at M = 3.0 for different in-hole roughness configurations

Fig. 8

Area-averaged effectiveness for configurations having increasing size of in-hole roughness, plotted as a function of blowing ratio

Fig. 9

Contours of θ in the x/D = 4 crossplane and contours of η on the wall (y/D = 0) at M = 3.0, for the (a) smooth hole and (b) rough hole. To show detail, only the pitchwise range z/D = −2 to 2 is shown.

Fig. 10

Contours of θ in the x/D = 10 crossplane and contours of η on the wall (y/D = 0) at M = 3.0, for the (a) smooth hole and (b) rough hole. To show detail, only the pitchwise range z/D = −2 to 2 is shown.

Fig. 11

Thermal field contours at M = 3.0 in the z/D = 0 centerline plane for the (a) smooth hole and (b) rough hole

Fig. 12

Mean velocity vectors and contours of mean streamwise velocity in the centerline plane at DR = 1.5, M = 3.0 for the (a) smooth hole and (b) rough hole

Fig. 13

Contours of turbulence intensity in the centerline plane at DR = 1.5, M = 3.0 for the (a) smooth hole and (b) rough hole

Fig. 14

Penetration angle of time-mean velocities along y/D = 0.4 in the centerline plane for smooth holes and rough holes, M = 1.0–3.0

Fig. 15

Area-averaged effectiveness for different in-hole roughness configurations. Percent change from smooth hole effectiveness is listed.

Fig. 16

Contours of adiabatic effectiveness at M = 3.0 with high freestream turbulence intensity for the (a) smooth holes and (b) rough diffuser holes

Fig. 17

Area-averaged effectiveness at low and high freestream turbulence intensities for smooth holes and rough diffuser holes. Percent change from smooth hole effectiveness is listed.

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