Dependence of Film Cooling Effectiveness on 3D Printed

Cooling HolesPresented By:Paul Aghasi

GT2016-56698, June 14th 2016

Paul Aghasi, MScEphraim Gutmark, PhD

David Munday, PhD

Authors, University of Cincinnati:

GT2016-56698 2Outline

• Experimental Approach and Motivation• Relevant Previous Work• Data Quality and Facility Validation• Experimental Results• Discussion and Conclusion • Backup Slides

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Supply System and Wind Tunnel

Facility Capabilities:Air Mass flow: up to 3.0 lbm/sCoolant Mass flow: up to 0.05 lbm/sMainstream Mach: up to 0.8Available Air at Highest Mass Flow: 30 mins

GT2016-56698 4Film Hole Geometry

• (a) CNC Aluminum • (b) SLA • (c) PolyJet• (d-f) FDM, 200-250-

300μ build layer resolutions

1Schroeder R. P., and Thole K. A., 2014. "Adiabatic Effectiveness Measurements For A Baseline Shaped Film Cooling Hole," in Proceedings of ASME Turbo Expo, Düsseldorf, Germany,

1

Objective:Similar performance?

If not why?

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Roughness and Diffusers• Ra/D = 0.005• Added roughness

caused:– Flow separation

prevention– BL thickening at the

throat and effective divergence angle reduction

1Persh and Bailey B. M., 1954."Effect of Surface Roughness Over the Downstream Region of a 23° Conical Diffuser," NACA TN 3066,

1

u/U

GT2016-56698 6Factors Affecting Part Quality• Stair stepping effect• Build orientation• Surface roughness is method

dependent• 90° build angle surface roughness can

be related to the 60° build angle surface roughness – True for SLA and FDM– Inverted for PolyJet

30°

1Ahn D., Kim H., and Lee S., 2009. "Surface roughness prediction using measured data and interpolation in layered manufacturing," Journal of Materials Processing Technology, 209, pp. 664-671, 2Kim G. D., and Oh Y. T., 2008. "A benchmark study on rapid prototyping processes and machines: quantitative comparisons of mechanical properties, accuracy, roughness, speed, and material cost," Journal of Engineering Manufacture, 222 (2), pp. 201-215,

2

2

1

2

GT2016-56698 7Data Quality – PSP Validation

1Baldauf S., Schulz A., and Wittig S., 2001. "High-Resolution Measurements of Local Effectiveness From Discrete Hole Film Cooling," ASME Journal of Turbomachinery, 123 (4), pp. 758-765,

δ/D = 0.4

δ/D = 0.1

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Experimental Flow Conditions

• Mainstream Mach 0.3 for all cases• Approach Rex= 9 X 105 > 5 X 105 • CO2 as coolant, density ratio = 1.5

– Mass transfer analogy• Test conditions:

Blowing Ratio (BR) 1.0 1.5 2.0 2.5 3.0 3.5Momentum flux ratio (I) 0.58 1.18 1.85 2.52 3.16 3.76

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Roughness Measurements-Bruker Contour GT-K1 3D Optical Microscope-White and green light interferometry

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Roughness measurementsBuild Layer

Thickness (μm)

Manufacturing

Technique (qty.)

Material Roughness

Ra/D

Observed

Liftoff (BR)

N/A CNC (1)Bare Al

Painted Al

0.00038

0.006502.5

25 (0.010D) PolyJet (3) RGD525 0.00927 2.0

25 (0.010D) SLA (1) Photo-polymer 0.00545 2.0

200 (0.08D) FDM (1) ABS Plastic 0.00896 >3.5

250 (0.10D) FDM (1) ABS Plastic 0.01077 3.0

300 (0.12D) FDM (1) ABS Plastic 0.01288 3.5

1Ahn D., Kim H., and Lee S., 2009. "Surface roughness prediction using measured data and interpolation in layered manufacturing," Journal of Materials

GT2016-56698 11

Discharge Coefficient• PolyJet Cd < FDM Cd• Highest Cd -> aluminum CNC • FDM roughness correlating

with Cd

FDM 300FDM 250FDM 200 PolyJet SLA Aluminum0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

1.01.52.02.53.03.5

Disc

harg

e Co

effici

ent

BR:

1.0 1.5 2.0 2.5 3.0 3.50.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

AluminumSLAPolyJetFDM 200FDM 250FDM 300

BR

Disc

harg

e Co

effici

ent

Roughness: coarse smooth

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Comparison of various test coupons at BR = 2.0, 1.85

Comparison of various test coupons at BR = 1.5, I = 1.18

Full Field Effectiveness

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Comparison of various test coupons at BR = 3.5, I = 3.76

Full Field η

0 0

0 0

0 0

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Lift off 2.5

Lift off >3.5

Lift off 2.0Lift off 2.0

Lift off 3.0 Lift off 3.5

Span Averaged Results

0 0 0

0 0 0

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Discussion and Conclusion• OSP increased Ra for aluminum • Major differences in η and η̅ for 3D printed coupons

– Care needs to be taken when testing 3D printed film holes.• In-hole coolant separation was delayed for rougher parts

– Most likely due to boundary layer thickening at the diffuser section1

– The exception is the PolyJet coupon • Rougher test coupons showed higher η̅ at BR of 3.5

– Due to the film diffusion on the rough surface that prevents it from penetrating into the mainstream2

• At this scale the roughness produced by additive manufacturing is not comparable to the less rough, standard CNC machined parts.

1Persh and Bailey B. M., 1954."Effect of Surface Roughness Over the Downstream Region of a 23° Conical Diffuser," NACA TN 3066, 2Goldstein, R. J. Eckert, E. R. G. Chiang, H. D. and Elovic, E. 1985. "Effect of Surface Roughness on Film Cooling Performance," Journal of Engineering for Gas Turbines and Power , 107, pp. 111-116,

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Future Work

• Build orientation• Roughness effects from the paint• Hot wire measurements

– Oversized holes• Metal 3D printing and its effect

– Its build orientation• Assess CFD validation

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Thank you!