Research Papers

Recent Advances in Manufacturing of Riblets on Compressor Blades and Their Aerodynamic Impact

[+] Author and Article Information
Christoph Lietmeyer

Test Engineer
Volkswagen AG, 38436 Wolfsburg, Germany
e-mail: Christoph.Lietmeyer@volkswagen.de

Berend Denkena

e-mail: Denkena@ifw.uni-hannover.de

Thomas Krawczyk

Research Assistant
e-mail: Krawczyk@ifw.uni-hannover.de
Institute of Production Engineering
and Machine Tools,
Leibniz Universitaet Hannover,
30823 Garbsen, Germany

Rainer Kling

Business Unit Manager Laser Micromachining
Centre Technologique ALPhANOV,
33405 Talence, France
e-mail: rainer.kling@alphanov.com

Ludger Overmeyer

e-mail: ludger.overmeyer@ita.uni-hannover.de

Bodo Wojakowski

Research Assistant
e-mail: b.wojakowski@lzh.de
Laser Zentrum Hannover e.V.,
30419 Hannover, Germany

Eduard Reithmeier

e-mail: sekretariat@imr.uni-hannover.de

Renke Scheuer

Research Assistant
e-mail: renke.scheuer@imr.uni-hannover.de

Taras Vynnyk

Group Leader Industrial and Medical Imaging
e-mail: taras.vynnyk@imr.uni-hannover.de
Institute of Measurement and Automatic Control,
Leibniz Universitaet Hannover,
30167 Hannover, Germany

Joerg R. Seume

Senior Member ASME
Institute of Turbomachinery and Fluid Dynamics,
Leibniz Universitaet Hannover,
30167 Hannover, Germany
e-mail: Seume@tfd.uni-hannover.de

Contributed by International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received July 10, 2012; final manuscript received August 10, 2012; published online June 3, 2013. Assoc. Editor: David Wisler.

J. Turbomach 135(4), 041008 (Jun 03, 2013) (12 pages) Paper No: TURBO-12-1136; doi: 10.1115/1.4007590 History: Received July 10, 2012; Revised August 10, 2012

Since Oehlert et al. (2007, “Exploratory Experiments on Machined Riblets for 2-D Compressor Blades,” Proceedings of International Mechanical Engineering Conference and Exposition 2007, Seattle, WA, IMECE2007-43457), significant improvements in the manufacturing processes of riblets by laser structuring and grinding have been achieved. In the present study, strategies for manufacturing small-scale grooves with a spacing smaller than 40 μm by metal bonded grinding wheels are presented. For the laser-structuring process, significant improvements of the production time by applying diffractive optical elements were achieved. Finally, strategies for evaluating the geometrical quality of the small-scale surface structures are shown and results obtained with two different measuring techniques (SEM and confocal microscope) are compared with each other. The aerodynamic impact of the different manufacturing processes is investigated based upon skin friction reduction data obtained on flat plates as well as the profile-loss reduction of riblet-structured compressor blades measured in a linear cascade wind tunnel. Numerical simulations with MISES embedded in a Monte Carlo simulation (MCS) were performed in order to calculate the profile-loss reduction of a blade structured by grinding to define further improvements of the riblet-geometry. A numerical as well as experimental study quantifying the relevant geometrical parameters indicate how further improvements from the present 4% reduction in skin friction can be achieved by an additional decrease of the riblet tip diameter and a more trapezoidal shape of the groove in order to realize the 8% potential reduction.

Copyright © 2013 by ASME
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Fig. 1

Riblet geometries ground by vitrified bonded grinding wheels

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Fig. 3

Microprofiles on the grinding wheel

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Fig. 4

Wear behavior over the grinding length for different vf and ae

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Fig. 5

Aspect ratio of ground riblets

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Fig. 6

Principal setup for laser machining. The multiaxis translation system positions the area of interest of the blades into the focal plane of the lens, while the scanner deflects the laser beam at high speed.

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Fig. 7

Principle of three spot ablation using beam splitting DOE; the effective spot-to-spot distance is determined by the rotation angle of the DOE

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Fig. 8

Simulated lanewise scanning pattern using a three sport DOE: two lanes are set side by side using three different riblet spacings (from top to bottom).

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Fig. 9

Magnified confocal microscope image of a smooth parameter set transition from 38 μm to 33 μm riblet spacings. The gray arrow marks a beginning bifurcation.

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Fig. 10

Intensity distribution through the image stack for different samples

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Fig. 11

Results of bilinear interpolation (top) and interpolation based on Delaunay triangulation

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Fig. 12

Elimination of the stochastic parts

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Fig. 15

Evaluation of the riblets radii using SEM

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Fig. 16

Wall shear-stress reduction of ground and laser-structured riblets in comparison to riblets with an ideal shape (experimental data measured by the German Aerospace Center, Institute of Propulsion Technology, Engine Acoustics Department); curves obtained by polynomial interpolation; σ = ±0.3%

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Fig. 17

Representative cross sections of ground and laser-structured riblets in comparison to the ideal geometry with a trapezoidal groove

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Fig. 18

Comparison of measured and calculated wall shear-stress reduction for ideal riblets; error bars indicate the standard deviation σ

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Fig. 19

Comparison of measured and calculated wall shear-stress reduction for ground riblets; error bars indicate the standard deviation σ

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Fig. 20

Probability density functions of geometric parameters of a ground riblet structure on a NACA 6510 compressor blade (measured by IMR)

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Fig. 21

Ant-hill-plots of profile-loss reduction

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Fig. 22

Pie chart of profile-loss reduction




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