WO1997001709A1 - Method and device for reduction of vibrations in a windmill blade - Google Patents
Method and device for reduction of vibrations in a windmill blade Download PDFInfo
- Publication number
- WO1997001709A1 WO1997001709A1 PCT/DK1996/000283 DK9600283W WO9701709A1 WO 1997001709 A1 WO1997001709 A1 WO 1997001709A1 DK 9600283 W DK9600283 W DK 9600283W WO 9701709 A1 WO9701709 A1 WO 9701709A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- blade
- mass
- cylinder
- lift
- lever system
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 18
- 230000001133 acceleration Effects 0.000 claims abstract description 16
- 239000007788 liquid Substances 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 5
- 238000013016 damping Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor
- F03D1/06—Rotors
- F03D1/065—Rotors characterised by their construction elements
- F03D1/0675—Rotors characterised by their construction elements of the blades
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2240/00—Components
- F05B2240/20—Rotors
- F05B2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
- F05B2240/305—Flaps, slats or spoilers
- F05B2240/3052—Flaps, slats or spoilers adjustable
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2260/00—Function
- F05B2260/96—Preventing, counteracting or reducing vibration or noise
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
Definitions
- the invention relates to a method for reduction of vibra ⁇ tions in a windmill blade so that the loads on the blade and on the remaining part of the mill structure are re ⁇ cuted.
- the invention also relates to a device for use in carrying out the method.
- the lift properties of a given blade profile may be changed in various manners. Lowering of a flap close to the rear edge of the profile, lifting a slot above the leading edge of the blade and placing of vortex generators on the suction side of the blade will normally increase the lift of the profile. Presence of a turbulator close to the leading edge of the blade or opening of channels for air flow across the pro ⁇ file will normally reduce the lift of the profile.
- the lift properties of the entire blade may be changed by adjusting the pitch angle of the blade.
- This object is achieved by a method of the kind described in the introduction, said method according to the invention being characteristic in that the aerodynamic properties of the blade are changed as a function of the acceleration and/or speed in the direction of rotation and/or out of the rotor plane of a slideable device.
- the superior principle of the invention is to provide a simple, direct connection between the acceleration and/or speed of the outer part of the blade and the aerodynamic properties of the blade. In a particularly advantageous manner this will reduce any vibrations.
- the basis of the invention is the fact that the accelera ⁇ tion and/or speed of the outer part of a windmill blade is a good indication of how the loads will develop by structural vibrations. As opposed to a measurement of the size of the loads, where the maximum signal is not obtained till the occurrence of the situation itself, which is to be avoided, a measurement of the acceleration and/or speed will provide the maximum signal already at the time when a vibration starts to develop. It should be noted that during rotation the individual parts of the blade are always accelerated inward. This centripetal acceleration is ir ⁇ relevant to the invention, and the term acceleration in this specification means acceleration in the direction of rotation (edgewise acceleration) or out of the rotor plane ( flapwise acceleration) .
- the vibration damping may be achieved by suspending a mass within or on the blade and connect same to one or more de- vices changing the lift properties on the blade.
- the mentioned aerodynamic properties are not only limited to the lift of the blade, but may also refer to the resistance and pitch moment of the blade.
- the lift of the blade may accordingly be increased as well as decreased, for example by the use of a flap which will normally increase the lift when it is lowered.
- the device according to the invention is by a first embodi ⁇ ment characteristic in that the device is a mass which via a lever system is mounted pivotably about an axis extending in the longitudinal direction of the blade so that by pivoting in a direction crosswise of the rotor plane and through the lever system, the mass will move a flap for re ⁇ cuted lift of the blade.
- fig. 1 is a diagram of the dynamic loads on a windmill blade
- fig. 2a-g is a number of examples of known methods for increasing the lift of a blade
- fig. 3a-c is a number of examples of known methods for reducing the lift of a blade
- fig. 4 is an embodiment of a device according to the in- vention where the flapwise acceleration of a sus ⁇ pended mass changes the lift of a blade by means of a flap,
- fig. 5 is an embodiment of a device according to the in- vention where the edgewise acceleration of a sus ⁇ pended mass changes the lift of a blade by means of a turbulator,
- fig. 6 is an embodiment of a device according to the in ⁇ vention where the acceleration of a suspended mass changes the lift of a blade via a viscous medium
- fig. 7 is an embodiment of a device according to the in ⁇ vention where the accelerating mass itself is a viscous medium, which can fill or drain an inflat- able flap of a blade,
- fig. 8 is an embodiment of a device according to the in ⁇ vention where the accelerating mass is connected to a hydraulic valve controlling the pitch angle of the entire windmill blade, and
- fig. 9 is a diagram showing how the dynamic loads on a windmill blade can be reduced by a device according to the invention.
- Fig. 1 is a diagram showing the dynamic loads on a windmill blade.
- the diagram is the result of computerized simulation in terms of the bending moment of the blade root over time.
- a slow vibration 1 which is due to the variation of the wind profile with the altitude above ground level during one rotor rotation, is overlaid by a quicker vibration 2, which is due to a random excitation of the structure emanating from turbulence.
- Fig. 2a-g show examples of known methods for changing the aerodynamic properties of a windmill blade, such as an in ⁇ crease in the blade lift.
- the shown methods comprise various embodiments: Plain flap or aileron 2a, split flap 2b, external airfoil flap 2c, slotted flap 2d, double slotted flap 2e, leading edge slat 2f and vortex generators 2g.
- Fig. 3a-c show examples of known methods for changing the aerodynamic properties of a windmill blade, such as a re ⁇ duction of the blade lift.
- the shown methods comprise turbo tape 10, stall strip 11 and ventilation 12.
- the lift of the blade may accordingly be increased as well as decreased, for example by using a flap, which will nor ⁇ mally increase the lift when it is lowered.
- Fig. 4 shows an embodiment of a device according to the in ⁇ vention.
- a mass 13 is suspended pivotably about a point 14a so as to allow the mass to be moved in a flapwise direction (i.e. crosswise of the chord).
- a lever system 14 By means of a lever system 14 the mass 13 is connected to a flap 15. If the blade is accelerated away from the wind 16, which will be the case when a sudden gust of wind increases the aerodynamic loads, the mass 13 will move towards the driving side 17 of the blade and will thereby take the flap 15 in a direction to- wards lesser lift, whereby the loads on the blade are re ⁇ cuted.
- Fig. 4 shows an embodiment of a device according to the in ⁇ vention.
- a mass 13 is suspended pivotably about a point 14a so as to allow the mass to be moved in a flapwise direction (i.e. crosswise of the chord).
- the mass 13 By means of a lever system 14 the mass 13 is connected to a flap 15. If the blade is accelerated away from
- FIG. 5 shows another embodiment of a device according to the invention, where a mass 18 is suspended pivotably about a point 19a so as to allow the mass to be moved in an edge ⁇ wise direction (i.e. along the chord).
- a lever system 19 By means of a lever system 19 the mass 18 is connected to a turbulator 20. If the blade is accelerated forwards in the direction of rota ⁇ tion 21, which will be the case during edgewise stalling vibrations when the lift varies in an unstable manner due to the proper motion of the blade, the mass 18 will move towards the rear edge 22 of the blade and thereby lift the turbulator 20 above the surface 23 of the blade, whereby the lift is again reduced, and the unstable state ceases.
- Fig. 6 shows a third embodiment of a device according to the invention, where a mass 24 is mounted within a cylinder 25 and centered by to springs 26.
- the cylinder 25 is filled with a viscous medium 27 and is connected by means of a pipe system 28 to a cylinder 29, which can activate a lift changing device 30.
- the mass 24 is designed as a piston in the cylinder 25 and is adapted to allow the viscous medium to pass by and/or through itself from one end to the other, in that the mass 24 for example has a smaller diameter than the internal diameter of the cylinder 25 or is provided with longitudinal bores not shown in the drawing.
- a desired damping may be achieved.
- the advantage of this embodiment is that by stationary conditions the lift changing device 30 will be unloaded by the vibration damper and may position itself in a position being the result of the aerodynamic reaction forces.
- Fig. 7 shows a fourth embodiment of a device according to the invention where a mass consists of a viscous liquid 32, which i ⁇ substantially held within a container 33, and by means of a pipe system 34 connected to a lift damping de ⁇ vice 35 having here the shape of an inflatable flap 36.
- a resilient pipe wall 37 will allow for the required change in volume.
- Fig. 8 shows yet another embodiment of a device according to the invention.
- a mass 38 is connected by means of a lever system to a hydraulic valve 39 forming part of a hydraulic system indicated by the letter P.
- the valve 39 leads the hydraulic medium to a cylinder 40, which in its turn adjusts the pitch angle of the entire blade.
- Fig. 9 is a diagram showing the dynamic loads on a windmill blade when a device according to the invention, as shown in fig. 4, has been implemented. It is clearly seen that the quick loads from the random excitation (compare with vibra ⁇ tion 2 in fig. 1) have been reduced. The slow vibration, which is due to the variation of the wind profile with the altitude above ground level during one rotor rotation (com- pare with vibration 1 in fig. 1), has not been noticeably reduced, but is also of less importance to the life of the mill.
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Wind Motors (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU62987/96A AU6298796A (en) | 1995-06-27 | 1996-06-26 | Method and device for reduction of vibrations in a windmill blade |
EP96921911A EP0835380A1 (en) | 1995-06-27 | 1996-06-26 | Method and device for reduction of vibrations in a windmill blade |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DK0742/95 | 1995-06-27 | ||
DK199500742A DK172932B1 (en) | 1995-06-27 | 1995-06-27 | Method and device for reducing vibrations in a wind turbine blade. |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997001709A1 true WO1997001709A1 (en) | 1997-01-16 |
Family
ID=8097017
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/DK1996/000283 WO1997001709A1 (en) | 1995-06-27 | 1996-06-26 | Method and device for reduction of vibrations in a windmill blade |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0835380A1 (en) |
AU (1) | AU6298796A (en) |
DK (1) | DK172932B1 (en) |
WO (1) | WO1997001709A1 (en) |
Cited By (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE29720741U1 (en) * | 1997-11-22 | 1998-05-28 | aerodyn Engineering GmbH, 24768 Rendsburg | Device for detecting vibrations of the rotor blades of a wind turbine |
DE29807874U1 (en) * | 1998-05-04 | 1999-09-30 | Husumer Schiffswerft Inh. Gebrüder Kröger GmbH & Co. KG, 25813 Husum | Rotor blade set for wind power plant for electricity generation |
EP0947693A2 (en) | 1998-03-31 | 1999-10-06 | Tacke Windenergie GmbH | Wind turbine blade profile |
EP1375911A1 (en) * | 2001-03-26 | 2004-01-02 | Hitachi Zosen Corporation | Propeller type windmill for power generation |
US6672837B1 (en) | 1998-05-29 | 2004-01-06 | Neg Micon A/S | Wind turbine with oscillation damping means |
DE102006022266A1 (en) * | 2005-11-04 | 2007-05-10 | Daubner & Stommel GbR Bau-Werk-Planung (vertretungsberechtigter Gesellschafter: Matthias Stommel, 27777 Ganderkesee) | Wind turbine |
WO2007089136A2 (en) * | 2006-02-03 | 2007-08-09 | Pantheon Bv | Wind turbine tower vibration damping |
US7293959B2 (en) | 2003-05-05 | 2007-11-13 | Lm Glasfibeer A/S | Wind turbine blade with lift-regulating means |
WO2008040347A1 (en) * | 2006-10-02 | 2008-04-10 | Vestas Wind Systems A/S | A wind turbine, a method for damping edgewise oscillations in one or more blades of a wind turbine by changing the blade pitch and use hereof |
ES2324002A1 (en) * | 2007-06-22 | 2009-07-28 | GAMESA INNOVATION & TECHNOLOGY, S.L. | Wind turbine blade with deflectable flaps |
WO2010023278A2 (en) * | 2008-08-29 | 2010-03-04 | Vestas Wind Systems A/S | Control system in wind turbine blades |
DE102008061838A1 (en) * | 2008-12-15 | 2010-06-17 | Repower Systems Ag | Rotor blade of a wind turbine with a turbulator |
DE102006034831B4 (en) * | 2005-07-29 | 2011-03-31 | General Electric Co. | Method and device for generating wind energy with reduced noise of the wind turbine |
DE202012005356U1 (en) | 2012-05-30 | 2012-07-10 | Petra Staude | Rotor blade for wind turbines with profiles in tandem arrangement |
WO2011147422A3 (en) * | 2010-05-27 | 2012-07-19 | Vestas Wind Systems A/S | Method and apparatus for reducing fluid flow induced forces produced by vortex shedding on a wind turbine rotor blade |
WO2012093022A3 (en) * | 2011-01-06 | 2012-08-30 | Siemens Aktiengesellschaft | Load mitigation device for wind turbine blades |
US8678746B2 (en) | 2006-06-09 | 2014-03-25 | Vestas Wind Systems A/S | Wind turbine blade and a pitch controlled wind turbine |
EP2851557A1 (en) * | 2013-09-24 | 2015-03-25 | LM WP Patent Holding A/S | A wind turbine blade with root end aerodynamic flaps |
EP2711542A3 (en) * | 2012-09-19 | 2015-09-02 | Senvion GmbH | Damping system and rotor blade |
CN105134482A (en) * | 2015-07-22 | 2015-12-09 | 扬州大学 | Gray combined modeling and optimized vibration controlling method of large intelligent draught fan blade system |
CN112196727A (en) * | 2020-10-28 | 2021-01-08 | 山东科技大学 | Stall nonlinear flutter suppression type wind turbine blade and flutter suppression system |
EP4310318A1 (en) * | 2022-07-21 | 2024-01-24 | Siemens Gamesa Renewable Energy A/S | Wind turbine rotor blade |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1990007646A1 (en) * | 1988-12-23 | 1990-07-12 | Helge Petersen | Aerodynamic brake on a wind rotor for a windmill |
-
1995
- 1995-06-27 DK DK199500742A patent/DK172932B1/en not_active IP Right Cessation
-
1996
- 1996-06-26 EP EP96921911A patent/EP0835380A1/en not_active Withdrawn
- 1996-06-26 WO PCT/DK1996/000283 patent/WO1997001709A1/en not_active Application Discontinuation
- 1996-06-26 AU AU62987/96A patent/AU6298796A/en not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1990007646A1 (en) * | 1988-12-23 | 1990-07-12 | Helge Petersen | Aerodynamic brake on a wind rotor for a windmill |
Cited By (33)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE29720741U1 (en) * | 1997-11-22 | 1998-05-28 | aerodyn Engineering GmbH, 24768 Rendsburg | Device for detecting vibrations of the rotor blades of a wind turbine |
EP0947693A2 (en) | 1998-03-31 | 1999-10-06 | Tacke Windenergie GmbH | Wind turbine blade profile |
EP0947693A3 (en) * | 1998-03-31 | 2001-11-14 | Tacke Windenergie GmbH | Wind turbine blade profile |
DE29807874U1 (en) * | 1998-05-04 | 1999-09-30 | Husumer Schiffswerft Inh. Gebrüder Kröger GmbH & Co. KG, 25813 Husum | Rotor blade set for wind power plant for electricity generation |
US6672837B1 (en) | 1998-05-29 | 2004-01-06 | Neg Micon A/S | Wind turbine with oscillation damping means |
EP1375911A4 (en) * | 2001-03-26 | 2005-11-23 | Hitachi Shipbuilding Eng Co | Propeller type windmill for power generation |
EP1375911A1 (en) * | 2001-03-26 | 2004-01-02 | Hitachi Zosen Corporation | Propeller type windmill for power generation |
US7293959B2 (en) | 2003-05-05 | 2007-11-13 | Lm Glasfibeer A/S | Wind turbine blade with lift-regulating means |
DE102006034831B4 (en) * | 2005-07-29 | 2011-03-31 | General Electric Co. | Method and device for generating wind energy with reduced noise of the wind turbine |
DE102006022266A1 (en) * | 2005-11-04 | 2007-05-10 | Daubner & Stommel GbR Bau-Werk-Planung (vertretungsberechtigter Gesellschafter: Matthias Stommel, 27777 Ganderkesee) | Wind turbine |
WO2007089136A2 (en) * | 2006-02-03 | 2007-08-09 | Pantheon Bv | Wind turbine tower vibration damping |
WO2007089136A3 (en) * | 2006-02-03 | 2007-09-27 | Pantheon Bv | Wind turbine tower vibration damping |
EP2027390B2 (en) † | 2006-06-09 | 2020-07-01 | Vestas Wind Systems A/S | A wind turbine blade and a pitch controlled wind turbine |
US8678746B2 (en) | 2006-06-09 | 2014-03-25 | Vestas Wind Systems A/S | Wind turbine blade and a pitch controlled wind turbine |
AU2007304633B2 (en) * | 2006-10-02 | 2011-02-24 | Vestas Wind Systems A/S | A wind turbine, a method for damping edgewise oscillations in one or more blades of a wind turbine by changing the blade pitch and use hereof |
US7854589B2 (en) | 2006-10-02 | 2010-12-21 | Vestas Wind Systems A/S | Wind turbine, a method for damping edgewise oscillations in one or more blades of a wind turbine by changing the blade pitch and use hereof |
WO2008040347A1 (en) * | 2006-10-02 | 2008-04-10 | Vestas Wind Systems A/S | A wind turbine, a method for damping edgewise oscillations in one or more blades of a wind turbine by changing the blade pitch and use hereof |
ES2324002A1 (en) * | 2007-06-22 | 2009-07-28 | GAMESA INNOVATION & TECHNOLOGY, S.L. | Wind turbine blade with deflectable flaps |
CN102165185A (en) * | 2008-08-29 | 2011-08-24 | 维斯塔斯风力系统有限公司 | Control system in wind turbine blades |
WO2010023278A3 (en) * | 2008-08-29 | 2011-03-10 | Vestas Wind Systems A/S | Control system in wind turbine blades |
US8851840B2 (en) | 2008-08-29 | 2014-10-07 | Vestas Wind Systems A/S | Control system in wind turbine blades |
WO2010023278A2 (en) * | 2008-08-29 | 2010-03-04 | Vestas Wind Systems A/S | Control system in wind turbine blades |
DE102008061838A1 (en) * | 2008-12-15 | 2010-06-17 | Repower Systems Ag | Rotor blade of a wind turbine with a turbulator |
WO2011147422A3 (en) * | 2010-05-27 | 2012-07-19 | Vestas Wind Systems A/S | Method and apparatus for reducing fluid flow induced forces produced by vortex shedding on a wind turbine rotor blade |
WO2012093022A3 (en) * | 2011-01-06 | 2012-08-30 | Siemens Aktiengesellschaft | Load mitigation device for wind turbine blades |
DE202012005356U1 (en) | 2012-05-30 | 2012-07-10 | Petra Staude | Rotor blade for wind turbines with profiles in tandem arrangement |
EP2711542A3 (en) * | 2012-09-19 | 2015-09-02 | Senvion GmbH | Damping system and rotor blade |
EP2851557A1 (en) * | 2013-09-24 | 2015-03-25 | LM WP Patent Holding A/S | A wind turbine blade with root end aerodynamic flaps |
CN105134482B (en) * | 2015-07-22 | 2018-03-06 | 扬州大学 | Large-scale intelligent fan blade System Grey color compositional modeling and the method for optimization vibration control |
CN105134482A (en) * | 2015-07-22 | 2015-12-09 | 扬州大学 | Gray combined modeling and optimized vibration controlling method of large intelligent draught fan blade system |
CN112196727A (en) * | 2020-10-28 | 2021-01-08 | 山东科技大学 | Stall nonlinear flutter suppression type wind turbine blade and flutter suppression system |
EP4310318A1 (en) * | 2022-07-21 | 2024-01-24 | Siemens Gamesa Renewable Energy A/S | Wind turbine rotor blade |
WO2024017673A1 (en) * | 2022-07-21 | 2024-01-25 | Siemens Gamesa Renewable Energy A/S | Wind turbine rotor blade |
Also Published As
Publication number | Publication date |
---|---|
EP0835380A1 (en) | 1998-04-15 |
AU6298796A (en) | 1997-01-30 |
DK172932B1 (en) | 1999-10-11 |
DK74295A (en) | 1996-12-28 |
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