Research Papers

Quantifying Blowing Ratio for Shaped Cooling Holes

[+] Author and Article Information
D. J. Cerantola

Department of Mechanical
and Materials Engineering,
Queen's University,
Kingston, ON K7 L 3N6, Canada
e-mail: david.cerantola@queensu.ca

A. M. Birk

Department of Mechanical
and Materials Engineering,
Queen's University,
Kingston, ON K7 L 3N6, Canada
e-mail: birk@me.queensu.ca

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 12, 2017; final manuscript received October 22, 2017; published online December 6, 2017. Editor: Kenneth Hall.

J. Turbomach 140(2), 021008 (Dec 06, 2017) (9 pages) Paper No: TURBO-17-1159; doi: 10.1115/1.4038277 History: Received September 12, 2017; Revised October 22, 2017

Effusion cooling has been a popular technology integrated into the design of gas turbine combustor liners. A staggering amount of research was completed that quantified performance with respect to operating conditions and cooling hole geometric properties; however, most of these investigations did not address the influence of the manufacturing process on the hole shape. This study completed an adiabatic wall numerical analysis using the realizable k–ϵ turbulence model of a laser-drilled hole that had a nozzled profile with an area ratio of 0.24 and five additional cylindrical, nozzled, diffusing, and fileted holes that yielded the same hole mass flow rate at representative engine conditions. The traditional methods for quantifying blowing ratio yielded the same value for all holes that was not useful considering the substantial differences in film cooling performance. It was proposed to define hole mass flux based on the outlet y-cross-sectional area projected onto the inclination angle plane. This gave blowing ratios that correlated to better and worse cooling performance for the diffusing and nozzled holes, respectively. The diffusing hole delivered the best film cooling due to having the lowest effluent velocity and greatest amount of in-hole turbulent production, which coincided with the worst discharge coefficient.

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Fig. 1

Hole area profiles

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Fig. 3

Hole geometry schematics. Coolant flow enters at hole bottom: (a) cylindrical, (b) cylindrical with filet, (c) conical nozzle, (d) elliptical nozzle, (e) as-drilled hole, and (f) conical diffuser.

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Fig. 4

Boundary condition schematic

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Fig. 5

z = 0 mesh plane through cylindrical hole

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Fig. 6

Cylindrical hole grid convergence study with adiabatic walls and Rkϵ. Symbols: solid—geometrically similar for grid study, hollow—ten rows in inflation layer, gray-filled—tetra–hex transition moved one-dimensional downstream, black outer—unstructured, lines—polynomial curve fits. Extrapolated relative errors shown at Δx = 0.

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Fig. 7

Grid convergence study wall shear distributions withRkϵ. Error bar shows the chosen grid uncertainty at x = 6.33Deq: (a) hot side centerline x-wall shear and (b) hole TE centerline z-wall shear.

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Fig. 8

Cylindrical hole pressure contours, streamlines, and uniform length vector tangents with Rkϵ. The inset Tu contours were calculated using Uc.

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Fig. 9

Cylindrical hole axial velocity (in y′) contours on z = 0 plane with Rkϵ

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Fig. 10

Hole performance using Rkϵ. Symbols denote the hole shape. Lines drawn to assist in identifying symbols of the same coefficient: (a) loss coefficients and (b) separation lengths.

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Fig. 11

z = 0 axial velocity profiles with Rkϵ: (a) y′=4.5Deq and (b) y = 0

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Fig. 12

Axial (lines) and azimuthal (filled) vorticity contours at y′=4.5Deq using Rkϵ (looking downstream). Positive counterclockwise.

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Fig. 13

x-vorticity and turbulence intensity contours at x = 6.33Deq using Rkϵ. Solid lines with symbols Tu=2/3k/Uh. Dashed line = 0.9Th.

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Fig. 14

Hot wall film cooling effectiveness using Rkϵ. Black lines with symbols show τx/qj.

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Fig. 15

Film cooling effectiveness with Rkϵ. Error bars show uncertainties for the cylindrical hole using the selected grid. (a) Centerline and (b) laterally averaged.

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Fig. 16

Film cooling effectiveness versus blowing ratio using Rkϵ. Lines drawn to assist in identifying similar symbols.



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