Details
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the ASME International Mechanical Engineering Congress and Exposition, IMECE 2007 |
| Pages | 25-39 |
| Number of pages | 15 |
| Publication status | Published - 22 May 2009 |
| Event | ASME International Mechanical Engineering Congress and Exposition, IMECE 2007 - Seattle, WA, United States Duration: 11 Nov 2007 → 15 Nov 2007 |
Publication series
| Name | ASME International Mechanical Engineering Congress and Exposition, Proceedings |
|---|---|
| Volume | 1 |
Abstract
During the last decades, riblets have shown a potential for viscous drag reduction. Several investigations and measurements of skin-friction in the boundary layer over flat plates and on turbomachinery type blades with ideal riblet geometry have been reported in the literature. The purpose of the present study is to investigate whether laser machined and ground riblet-like structures could be successfully employed on conventional 2-D (NACA) compressor blades in order to assess the potential of industrial machining processes for the creation of the riblet effect. Perfectly trapezoid riblets were designed specifically for the flow parameters in the wind tunnel. Parameters describing the geometry and the deviation from ideal riblets are developed. Riblet machining by high precision material ablation has the potential of achieving micro-machining quality. In comparison to ns-laser processing using either Q-switched solid-state lasers or excimer lasers, the results for high precision material ablation show the enormous potential of ps-laser radiation and achieve the required quality, free of thermally induced defects and, consequently, with high reproducibility. For grinding riblets, geometrically defined microprofiles must firstly be generated via a profile dressing process and then ground onto the work piece surface. A precise adjustment of the grinding wheel system (grit, bonding) and the dressing/grinding conditions is necessary, in order to satisfy the opposing requirements at both dressing and grinding. The blade specimens were geometrically measured with a confocal microscope as well as secondary electron microscope using a specially developed riblet-oriented analysis. For verifying the measurement results, an Atomic Force Microscope was used. The specimens, i.e. flat plates and compressor blades, are aerodynamically tested in a cascade wind tunnel and properly scaled model surfaces were tested in an oil channel in order to quantify skin-friction reduction. Wake measurements of a cascade with NACA-profiles which have the resulting riblet-like structured surface show that the laser shaped as well as ground riblets reduce skin-friction almost as well as the ideal ones, which means a skin friction reduction of up to 7%.
ASJC Scopus subject areas
- Engineering(all)
- General Engineering
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Proceedings of the ASME International Mechanical Engineering Congress and Exposition, IMECE 2007. 2009. p. 25-39 (ASME International Mechanical Engineering Congress and Exposition, Proceedings; Vol. 1).
Research output: Chapter in book/report/conference proceeding › Conference contribution › Research › peer review
}
TY - GEN
T1 - Exploratory Experiments on Machined Riblets for 2-D Compressor Blades
AU - Oehlert, Karsten
AU - Seume, Joerg R.
AU - Wang, Bo
AU - Denkena, Berend
AU - Hage, Wolfram
AU - Knobloch, Karsten
AU - Meyer, Robert
AU - Siegel, Frank
AU - Ostendorf, Andreas
AU - Vynnyk, Taras
AU - Reithmeier, Eduard
PY - 2009/5/22
Y1 - 2009/5/22
N2 - During the last decades, riblets have shown a potential for viscous drag reduction. Several investigations and measurements of skin-friction in the boundary layer over flat plates and on turbomachinery type blades with ideal riblet geometry have been reported in the literature. The purpose of the present study is to investigate whether laser machined and ground riblet-like structures could be successfully employed on conventional 2-D (NACA) compressor blades in order to assess the potential of industrial machining processes for the creation of the riblet effect. Perfectly trapezoid riblets were designed specifically for the flow parameters in the wind tunnel. Parameters describing the geometry and the deviation from ideal riblets are developed. Riblet machining by high precision material ablation has the potential of achieving micro-machining quality. In comparison to ns-laser processing using either Q-switched solid-state lasers or excimer lasers, the results for high precision material ablation show the enormous potential of ps-laser radiation and achieve the required quality, free of thermally induced defects and, consequently, with high reproducibility. For grinding riblets, geometrically defined microprofiles must firstly be generated via a profile dressing process and then ground onto the work piece surface. A precise adjustment of the grinding wheel system (grit, bonding) and the dressing/grinding conditions is necessary, in order to satisfy the opposing requirements at both dressing and grinding. The blade specimens were geometrically measured with a confocal microscope as well as secondary electron microscope using a specially developed riblet-oriented analysis. For verifying the measurement results, an Atomic Force Microscope was used. The specimens, i.e. flat plates and compressor blades, are aerodynamically tested in a cascade wind tunnel and properly scaled model surfaces were tested in an oil channel in order to quantify skin-friction reduction. Wake measurements of a cascade with NACA-profiles which have the resulting riblet-like structured surface show that the laser shaped as well as ground riblets reduce skin-friction almost as well as the ideal ones, which means a skin friction reduction of up to 7%.
AB - During the last decades, riblets have shown a potential for viscous drag reduction. Several investigations and measurements of skin-friction in the boundary layer over flat plates and on turbomachinery type blades with ideal riblet geometry have been reported in the literature. The purpose of the present study is to investigate whether laser machined and ground riblet-like structures could be successfully employed on conventional 2-D (NACA) compressor blades in order to assess the potential of industrial machining processes for the creation of the riblet effect. Perfectly trapezoid riblets were designed specifically for the flow parameters in the wind tunnel. Parameters describing the geometry and the deviation from ideal riblets are developed. Riblet machining by high precision material ablation has the potential of achieving micro-machining quality. In comparison to ns-laser processing using either Q-switched solid-state lasers or excimer lasers, the results for high precision material ablation show the enormous potential of ps-laser radiation and achieve the required quality, free of thermally induced defects and, consequently, with high reproducibility. For grinding riblets, geometrically defined microprofiles must firstly be generated via a profile dressing process and then ground onto the work piece surface. A precise adjustment of the grinding wheel system (grit, bonding) and the dressing/grinding conditions is necessary, in order to satisfy the opposing requirements at both dressing and grinding. The blade specimens were geometrically measured with a confocal microscope as well as secondary electron microscope using a specially developed riblet-oriented analysis. For verifying the measurement results, an Atomic Force Microscope was used. The specimens, i.e. flat plates and compressor blades, are aerodynamically tested in a cascade wind tunnel and properly scaled model surfaces were tested in an oil channel in order to quantify skin-friction reduction. Wake measurements of a cascade with NACA-profiles which have the resulting riblet-like structured surface show that the laser shaped as well as ground riblets reduce skin-friction almost as well as the ideal ones, which means a skin friction reduction of up to 7%.
UR - http://www.scopus.com/inward/record.url?scp=44349120584&partnerID=8YFLogxK
U2 - 10.1115/IMECE2007-43457
DO - 10.1115/IMECE2007-43457
M3 - Conference contribution
AN - SCOPUS:44349120584
SN - 0791842959
SN - 9780791842959
T3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings
SP - 25
EP - 39
BT - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, IMECE 2007
T2 - ASME International Mechanical Engineering Congress and Exposition, IMECE 2007
Y2 - 11 November 2007 through 15 November 2007
ER -