WO2010022739A2 - A wind turbine generator comprising a rotor with vibration damping properties - Google Patents

A wind turbine generator comprising a rotor with vibration damping properties Download PDF

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Publication number
WO2010022739A2
WO2010022739A2 PCT/DK2009/050220 DK2009050220W WO2010022739A2 WO 2010022739 A2 WO2010022739 A2 WO 2010022739A2 DK 2009050220 W DK2009050220 W DK 2009050220W WO 2010022739 A2 WO2010022739 A2 WO 2010022739A2
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WO
WIPO (PCT)
Prior art keywords
rotor
rotor blade
wind turbine
turbine generator
different
Prior art date
Application number
PCT/DK2009/050220
Other languages
French (fr)
Other versions
WO2010022739A3 (en
Inventor
Carsten Hein Westergaard
Original Assignee
Vestas Wind Systems A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vestas Wind Systems A/S filed Critical Vestas Wind Systems A/S
Publication of WO2010022739A2 publication Critical patent/WO2010022739A2/en
Publication of WO2010022739A3 publication Critical patent/WO2010022739A3/en

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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
    • F03D1/0658—Arrangements for fixing wind-engaging parts to a hub
    • 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
    • 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
    • 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
    • F05B2280/00—Materials; Properties thereof
    • F05B2280/50—Intrinsic material properties or characteristics
    • F05B2280/5001—Elasticity
    • 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
    • F05B2280/00—Materials; Properties thereof
    • F05B2280/60—Properties or characteristics given to material by treatment or manufacturing
    • F05B2280/6003—Composites; e.g. fibre-reinforced
    • 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
    • F05B2280/00—Materials; Properties thereof
    • F05B2280/70—Treatments or modification of materials
    • F05B2280/702—Reinforcements
    • 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

  • a wind turbine generator comprising a rotor with vibration damping properties
  • the invention relates to a wind turbine generator comprising a rotor having at least two rotor blades, the rotor being arranged to be able to rotate around a substantially horizontal main shaft, where the rotor blades extend radially outwards from the main shaft to which they are attached via a rotor hub.
  • the invention also relates to use of a rotor having two or more rotor blades.
  • Wind turbine generators are well-known and commonly used in major parts of the world for the production of electricity. To optimize the output of the wind turbine generators there is a recent trend to increase the size of the wind turbine generators. However, with increased size of a generator, the load on the rotor and other parts of the generator during operation will increase too.
  • One way of damping vibrations is to control the pitch angles as e.g. described in WO 2007/053031 A1 , which discloses a method for damping tower vibrations in a wind turbine installation by controlling the pitch angle of the rotor blades.
  • An object of the present invention is to provide a wind turbine generator with a rotor having vibration build-in damping properties.
  • a further object is to reduce the load on a wind turbine generator caused by vibrations in a rotating rotor.
  • the invention in a first aspect relates to a wind turbine generator comprising a rotor having at least two rotor blades, said rotor being arranged to be able to rotate around a substantially horizontal main shaft, said rotor blades extending radially outwards from the main shaft to which they are attached via a rotorhub, wherein one of the rotor blades is structurally different from the other one or more rotor blades.
  • the invention provides for a rotor comprising two or more rotor blades, in which rotor blades with different vibration properties are utilized to damp vibrations in rotors for wind turbines.
  • rotor blades for wind turbines are produced in industrial scale in a production line, which means that the produced rotor blades are substantially identical within a narrow range of deviation from a standard blade. This is of course a production method that is cost-effective and un-complicated.
  • the manufacturing process becomes a little more complicated, this may easily be counter-balanced by the advantages achieved in respect of vibration properties. Consequently, during operation the rotor blade will vibrate with a different mode or at other frequencies than the other rotor blade or the other rotor blades, and this will cause a damping of the vibrations in the entire rotor system.
  • the term structurally different is to be understood in the meaning that the rotor blades have an internal different structure that does not substantially affect the external geometry of the rotor blades. Examples of such structural differences, may be different locations of the structural elements within the rotor blades or alternatively structural elements having different properties, e.g. in respect of stiffness.
  • the rotor comprises a first rotor blade, a second rotor blade and a third rotor blade, where the structure of the first rotor blade is different from the structure of the second rotor blade and the structure of the third rotor blade.
  • the first rotor blade will then during operation contribute to the total vibrations of the rotor with vibrations in a different mode, than the vibrations of the second and the third rotor blade. This will induce a damping of the rotor system.
  • the structure of the second rotor blade and the structure of the third rotor blade are substantially identical. This will facilitate production as the second and the third rotor blade can be produced in the same production line.
  • each rotor blade comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, however, in an embodiment of the invention the structural member is placed in a different position in the first rotor blade, in relation to the positions of the structural members in the second and the third rotor blade. The first rotor blade is then made structurally different from the second and the third rotor blade in a relatively simple way.
  • each rotor blade also comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, where the structural member has a different stiffness in the first rotor blade, in relation to the stiffness of the structural members in the second and the third rotor blade.
  • This embodiment can very easy be implemented in a production line to provide rotor blades with different vibrations properties, as the use of structural members with different stiffness is the only change from normal production.
  • the structural member is a spar, which is normally present in rotor blades. The spar can relatively easy be located differently in the rotor blades and thereby serve to provide different vibration properties in the blades to obtain the advantages according to the invention.
  • the spars used in the rotor blades may also have different stiffness to alternatively or further provide different properties in the rotor blades.
  • the different structural properties of the rotor blades are provided by the resin laminates or fibre reinforced members forming the rotor blades.
  • each rotor blade comprises layers of laminates of thermoplastic resin and where the laminates in the first rotor blade are different from the layers in the second rotor blade and the layers in the third rotor blade.
  • the laminates or fibre reinforced members may be different in respect of orientation, thickness and composition.
  • the laminates comprise fibers, and these fibers may have different orientation in the laminates in the structurally different rotor blades.
  • different types of fibres may be used in the structurally different rotor blades.
  • the rotor blades can be produced with relatively un-complicated modifications in the production line. Thus, it is possible to obtain rotor blades with different properties by having resin laminates or fibre reinforced members with different orientations and/or thikness in the rotor blades.
  • the layminates forming the blades are made of strips of thermoplastic resin, preferably including fibers with a certain orientation, and the strips of the first rotor blade are oriented different than the corresponding strips of the second rotor blade and the strips of the third rotor blade.
  • This embodiment provides for rotor blade with different vibration properties that can be produced in a simple and cost-effective manner.
  • the advantage in respect of reducing vibrations in the rotor of the wind turbine generator according to invention may also be obtained by an embodiment where the rotor blades are attached to the rotor by hub attachments, wherein the hub attachment of the first rotor blade is different from the hub attachment of the second rotor blade and the hub attachment of the third rotor blade.
  • the different hub attachment of the first rotor blade may be obtained by a applying a hub extension.
  • each rotor blade on the rotor has in an alternative embodiment, a structure that is different from the structures of the other rotor blades.
  • This embodiment provides for a rotor where all of the rotor blades have a different structure and it is possible to obtain excellent vibration damping properties in the rotor.
  • rotor blades are structurally different in respect of location of the structural member, spar, constitution of the layers in the laminate and hub attachment in any desired combination.
  • the rotor blades according to the invention have different internal structure, however, for improving the visual appearance of the wind turbine generator it is preferred that the external geometry of the rotor blades are substantially identical.
  • the invention also relates to use of a rotor having two or more rotor blades, wherein at least one rotor blade is structurally different from the other rotor blade(s) for damping vibrations in a wind turbine generator during operation.
  • Fig 1 diagrammatically illustrates rotor blades according to the invention with different spar positions.
  • Fig 2 diagrammatically illustrates rotor blades according to the invention with different layers. Detailed description of preferred embodiments
  • a wind turbine generator comprises a tower carrying a nacelle.
  • the nacelle carries the rotor with the rotor blades attached to the mainshaft via a rotor hub.
  • the nacelle further houses the gearbox, generator and other equipment required to operate the wind turbine generator, which equipment is familiar to the person skilled in the art.
  • the rotor blades for a wind turbine generator are normally produced as a shelf of several layers of laminate supported by an internal structural element or spar.
  • the laminate comprises usually resin and fibers.
  • the resin may be an epoxy resin and the fibers may e.g. be based on glass, ceramics or carbon.
  • the structural member or spar may be made from wood or metal.
  • the present invention provides a solution where at least one of the rotor blades is structurally different from the other rotor blades.
  • Fig 1 illustrates an embodiment of the rotor blades according to the invention where the spar has been placed in different positions to obtain structurally different rotor blades.
  • Fig 1 a illustrates a rotorblade 1 a in which the spar 3a is located in a position near the leading edge 4 of the rotor blade 1a.
  • Fig 1 b illustrates a similar rotor blade 1 b, however in this rotor blade the spar 3b is located near the trailing edge 5.
  • Fig 1 a and Fig 1 b illustrates two rotor blades having substantially identical external geometry, although being structurally different, and thereby showing different vibration properties.
  • the spars 3a and 3b may have different stiffness to further improve the vibration properties when the rotor blades are placed in a rotor.
  • Fig 2 illustrates alternative rotorblades according to the invention.
  • the rotor blades have layers of laminate that are orientated different in the two rotor blades.
  • the laminate is made from an epxy resin comprising glass fibers.
  • Fig 2a illustrates a rotorblade 2a with laminated layers 6a and 7a that have orientations with an an angle ⁇ i of 90° between them.
  • Fig 2b a similar rotor blade 2b with laminated layers 6b and 7b that have orientations with an angle ⁇ 2 of 60° between them.
  • the laminates comprises glass fibers that have a substantially uniform orientation in each layer of laminate 6, 7.
  • the orientation of the fibers are also different in the two rotor blades 2a and 2b.
  • the illustrated rotor blades are suitable for use in a wind turbine generator according to the invention.

Abstract

This invention relates to a wind turbine generator comprising a rotor having at least two rotor blades, said rotor being arranged to be able to rotate around a substantially horizontal main shaft, said rotor blades extending radially outwards from the main shaft to which they are attached via a rotorhub, wherein one of the rotor blades is structurally different from the other one or more rotor blades. The invention further relates to use of rotor having two or more rotor blades, wherein at least one rotor blade is structurally different from the other rotor blade(s) for damping vibrations in a wind turbine generator during operation.

Description

A wind turbine generator comprising a rotor with vibration damping properties
Technical field The invention relates to a wind turbine generator comprising a rotor having at least two rotor blades, the rotor being arranged to be able to rotate around a substantially horizontal main shaft, where the rotor blades extend radially outwards from the main shaft to which they are attached via a rotor hub. The invention also relates to use of a rotor having two or more rotor blades.
Background of the invention
Wind turbine generators are well-known and commonly used in major parts of the world for the production of electricity. To optimize the output of the wind turbine generators there is a recent trend to increase the size of the wind turbine generators. However, with increased size of a generator, the load on the rotor and other parts of the generator during operation will increase too.
One kind of load that will appear during operation and rotation of the rotor is caused by the vibration of the rotor blades. Vibration and resonance caused thereby in the blades may lead to high amounts of accumulated energy in the rotor blades and the rotor, which may end up being detrimental for the structure, e.g. by formation of fatigue fractures and subsequent collapse. To avoid such serious damages caused by vibrations on the structure it is desired or necessary to damp the vibrations of the rotor blades. Several methods and means have been proposed for damping vibrations in rotor blades.
One way of damping vibrations is to control the pitch angles as e.g. described in WO 2007/053031 A1 , which discloses a method for damping tower vibrations in a wind turbine installation by controlling the pitch angle of the rotor blades.
Other proposals how to damp vibrations in rotor blades make use of damping material or weights to balance the rotor blades. An example of a solution with damping material is known from e.g. WO 99/43955 A1 , which relates to wind turbine blade with a load bearing structure and a damping material for damping the natural vibrations of the blade. CA 2553896 A1 describes a horizontal wind turbine blade balancing accessory. The accessory is used in a multiblade rotor, balancing the blades by placing weights near the tip of the blades. Although a numerous of damping methods exist there is still a need for an improved damping of the vibrations caused by the rotor blades in a rotating rotor of wind turbine generator.
Summary of the invention
An object of the present invention is to provide a wind turbine generator with a rotor having vibration build-in damping properties.
A further object is to reduce the load on a wind turbine generator caused by vibrations in a rotating rotor.
In a first aspect the invention relates to a wind turbine generator comprising a rotor having at least two rotor blades, said rotor being arranged to be able to rotate around a substantially horizontal main shaft, said rotor blades extending radially outwards from the main shaft to which they are attached via a rotorhub, wherein one of the rotor blades is structurally different from the other one or more rotor blades.
The invention provides for a rotor comprising two or more rotor blades, in which rotor blades with different vibration properties are utilized to damp vibrations in rotors for wind turbines. Normally, rotor blades for wind turbines are produced in industrial scale in a production line, which means that the produced rotor blades are substantially identical within a narrow range of deviation from a standard blade. This is of course a production method that is cost-effective and un-complicated. However, it has now been found that if one of the rotor blades is structurally different from the other rotor blade or the other rotor blades, this rotor blade will also possess a different vibration mode or the eigenfrequencies are shifted to different values. Although the manufacturing process becomes a little more complicated, this may easily be counter-balanced by the advantages achieved in respect of vibration properties. Consequently, during operation the rotor blade will vibrate with a different mode or at other frequencies than the other rotor blade or the other rotor blades, and this will cause a damping of the vibrations in the entire rotor system. The term structurally different is to be understood in the meaning that the rotor blades have an internal different structure that does not substantially affect the external geometry of the rotor blades. Examples of such structural differences, may be different locations of the structural elements within the rotor blades or alternatively structural elements having different properties, e.g. in respect of stiffness.
Contrary to this, if the rotor is equipped with substantially identically rotor blades, these rotor blades will vibrate substantially identical and thereby result in an increase of the total vibration of the rotor and an increase of the total load on the rotor.
Although it is possible to use wind turbine generators having two, three, four, five or more rotor blades, it has proven to be optimally in respects of costs and energy output to use rotors having three rotor blades. Consequently, in an embodiment of the wind turbine generator according to the invention the rotor comprises a first rotor blade, a second rotor blade and a third rotor blade, where the structure of the first rotor blade is different from the structure of the second rotor blade and the structure of the third rotor blade. The first rotor blade will then during operation contribute to the total vibrations of the rotor with vibrations in a different mode, than the vibrations of the second and the third rotor blade. This will induce a damping of the rotor system.
It is preferred that the structure of the second rotor blade and the structure of the third rotor blade are substantially identical. This will facilitate production as the second and the third rotor blade can be produced in the same production line.
In a traditional manner each rotor blade comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, however, in an embodiment of the invention the structural member is placed in a different position in the first rotor blade, in relation to the positions of the structural members in the second and the third rotor blade. The first rotor blade is then made structurally different from the second and the third rotor blade in a relatively simple way.
In an alternative embodiment of the wind turbine generator according to the invention each rotor blade also comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, where the structural member has a different stiffness in the first rotor blade, in relation to the stiffness of the structural members in the second and the third rotor blade. This embodiment can very easy be implemented in a production line to provide rotor blades with different vibrations properties, as the use of structural members with different stiffness is the only change from normal production. In a further embodiment the structural member is a spar, which is normally present in rotor blades. The spar can relatively easy be located differently in the rotor blades and thereby serve to provide different vibration properties in the blades to obtain the advantages according to the invention. The spars used in the rotor blades may also have different stiffness to alternatively or further provide different properties in the rotor blades.
In an embodiment of the wind turbine generator according to the invention, the different structural properties of the rotor blades are provided by the resin laminates or fibre reinforced members forming the rotor blades. In this embodiment each rotor blade comprises layers of laminates of thermoplastic resin and where the laminates in the first rotor blade are different from the layers in the second rotor blade and the layers in the third rotor blade. The laminates or fibre reinforced members may be different in respect of orientation, thickness and composition. The laminates comprise fibers, and these fibers may have different orientation in the laminates in the structurally different rotor blades. Moreover different types of fibres may be used in the structurally different rotor blades. The rotor blades can be produced with relatively un-complicated modifications in the production line. Thus, it is possible to obtain rotor blades with different properties by having resin laminates or fibre reinforced members with different orientations and/or thikness in the rotor blades.
Preferably the layminates forming the blades are made of strips of thermoplastic resin, preferably including fibers with a certain orientation, and the strips of the first rotor blade are oriented different than the corresponding strips of the second rotor blade and the strips of the third rotor blade. This embodiment provides for rotor blade with different vibration properties that can be produced in a simple and cost-effective manner.
The advantage in respect of reducing vibrations in the rotor of the wind turbine generator according to invention may also be obtained by an embodiment where the rotor blades are attached to the rotor by hub attachments, wherein the hub attachment of the first rotor blade is different from the hub attachment of the second rotor blade and the hub attachment of the third rotor blade. The different hub attachment of the first rotor blade may be obtained by a applying a hub extension. This embodiment is very easy to establish and can even be implemented in existing wind turbine generators.
Although it normally will be sufficient if one of the rotor blades is different from the one or more other rotor blades in the rotor of the wind turbine generator according to the invention, each rotor blade on the rotor has in an alternative embodiment, a structure that is different from the structures of the other rotor blades. This embodiment provides for a rotor where all of the rotor blades have a different structure and it is possible to obtain excellent vibration damping properties in the rotor.
It will also be possible to realize a rotor in which the rotor blades are structurally different in respect of location of the structural member, spar, constitution of the layers in the laminate and hub attachment in any desired combination. The rotor blades according to the invention have different internal structure, however, for improving the visual appearance of the wind turbine generator it is preferred that the external geometry of the rotor blades are substantially identical.
In a further aspect, the invention also relates to use of a rotor having two or more rotor blades, wherein at least one rotor blade is structurally different from the other rotor blade(s) for damping vibrations in a wind turbine generator during operation. By using such a rotor it is possible to reduce the load on the entire wind turbine generator during operation.
Brief description of the drawings
The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:
Fig 1 diagrammatically illustrates rotor blades according to the invention with different spar positions.
Fig 2 diagrammatically illustrates rotor blades according to the invention with different layers. Detailed description of preferred embodiments
Detail description of preferred embodiments
In general a wind turbine generator comprises a tower carrying a nacelle. The nacelle carries the rotor with the rotor blades attached to the mainshaft via a rotor hub. The nacelle further houses the gearbox, generator and other equipment required to operate the wind turbine generator, which equipment is familiar to the person skilled in the art. The rotor blades for a wind turbine generator are normally produced as a shelf of several layers of laminate supported by an internal structural element or spar. The laminate comprises usually resin and fibers. The resin may be an epoxy resin and the fibers may e.g. be based on glass, ceramics or carbon. The structural member or spar may be made from wood or metal.
Today most must wind turbine generator are equipped with rotors carrying three rotorblades, and the three rotor blades are substantially identical. However, as previously described the present invention provides a solution where at least one of the rotor blades is structurally different from the other rotor blades.
Thus, Fig 1 illustrates an embodiment of the rotor blades according to the invention where the spar has been placed in different positions to obtain structurally different rotor blades.
Fig 1 a illustrates a rotorblade 1 a in which the spar 3a is located in a position near the leading edge 4 of the rotor blade 1a.
Fig 1 b illustrates a similar rotor blade 1 b, however in this rotor blade the spar 3b is located near the trailing edge 5.
Accordingly, Fig 1 a and Fig 1 b illustrates two rotor blades having substantially identical external geometry, although being structurally different, and thereby showing different vibration properties. As a further structural difference the spars 3a and 3b may have different stiffness to further improve the vibration properties when the rotor blades are placed in a rotor.
Fig 2 illustrates alternative rotorblades according to the invention. In this embodiment the rotor blades have layers of laminate that are orientated different in the two rotor blades. The laminate is made from an epxy resin comprising glass fibers.
Fig 2a illustrates a rotorblade 2a with laminated layers 6a and 7a that have orientations with an an angle αi of 90° between them.
In Fig 2b is shown a similar rotor blade 2b with laminated layers 6b and 7b that have orientations with an angle α2 of 60° between them.
The laminates comprises glass fibers that have a substantially uniform orientation in each layer of laminate 6, 7. Thus, the orientation of the fibers are also different in the two rotor blades 2a and 2b.
The illustrated rotor blades are suitable for use in a wind turbine generator according to the invention.
The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

1. A wind turbine generator comprising a rotor having at least two rotor blades, said rotor being arranged to be able to rotate around a substantially horizontal main shaft, wherein one of the rotor blades is structurally different from the other one or more rotor blades.
2. A wind turbine generator according to claim 1 , wherein the rotor comprises a first rotor blade, a second rotor blade and a third rotor blade, wherein the structure of the first rotor blade is different from the structure of the second rotor blade and the structure of the third rotor blade.
3. A wind turbine generator according to claim 2, wherein the structure of the second rotor blade and the structure of the third rotor blade are substantially identical.
4. A wind turbine generator accordong to claim 1 , 2 or 3, wherein the the rotor comprises a first rotor blade, a second rotor blade and a third rotor blade, wherein the structure of the each rotor blade is different from the structure of the other rotor blades.
5. A wind turbine generator according to claim 1 , 2 or 3 wherein each rotor blade comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, and wherein said structural member is placed in a different position in the first rotor blade, in relation to the positions of the structural members in the second rotor blade and the third rotor blade.
6. A wind turbine generator according to claim 1 , 2 or 3 wherein each rotor blade comprises at least one oblong structural member extending in the longitudinal direction of the rotor blade, said structural member has a different stiffness in the first rotor blade, in relation to the stiffness of the structural members in the second rotor blade and the third rotor blade.
7. A wind turbine generator according to claim 5 or 6, wherein the structural member is a spar.
8. A wind turbine generator according to anyone of the preceding claims, wherein each rotor blade comprises at least one fibre reinforced member and where the fibre reinforced member in the first rotor blade is different from the fibre reinforced member in the second rotor blade and/or the fibre reinforced member in the third rotor blade.
9. A wind turbine generator according to claim 7, wherein the fibre reinforced member of the first rotor blade comprises fibres which are oriented different than the corresponding fibres of the fibre reinforced member of the second rotor blade and/or the corresponding fibres of the fibre reinforced member of the third rotor blade
10. A wind turbine generator according to any of the preceding claims, wherein the rotor blades are attached to a hub by hub attachments, and wherein the hub attachment of the first rotor blade is different from the hub attachment of the second rotor blade and/or the hub attachment of the third rotor blade.
11. A wind turbine generator according to any of the preceding claims, wherein each rotor blade on the rotor has a structure different from the structures of the other rotor blades.
12. A wind turbine generator according to any of the preceding claims, wherein the external geometry of the rotor blades are substantially identical.
13. Use of rotor having two or more rotor blades, wherein at least one rotor blade is structurally different from the other rotor blade(s) for damping vibrations in a wind turbine generator during operation.
PCT/DK2009/050220 2008-08-29 2009-08-28 A wind turbine generator comprising a rotor with vibration damping properties WO2010022739A2 (en)

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DKPA200801205 2008-08-29
DKPA200801205 2008-08-29
US9384908P 2008-09-03 2008-09-03
US61/093,849 2008-09-03

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015158346A1 (en) * 2014-04-14 2015-10-22 Envision Energy (Denmark) Aps Asymmetric blade damper
EP3093485A1 (en) * 2015-05-11 2016-11-16 Blade Dynamics Limited A wind turbine blade

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3716326A1 (en) * 1987-05-15 1988-12-01 Schempp Hirth Gmbh & Co Kg Propeller
NL1014719C2 (en) * 2000-03-22 2001-09-25 Aerpac Holding B V Wind turbine, has asymmetrically arranged turbine vanes to reduced stall induced vibrations
US20050249586A1 (en) * 2004-04-20 2005-11-10 Snecma Moteurs Method for introducing a deliberate mismatch on a turbomachine bladed wheel, bladed wheel with a deliberate mismatch

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3716326A1 (en) * 1987-05-15 1988-12-01 Schempp Hirth Gmbh & Co Kg Propeller
NL1014719C2 (en) * 2000-03-22 2001-09-25 Aerpac Holding B V Wind turbine, has asymmetrically arranged turbine vanes to reduced stall induced vibrations
US20050249586A1 (en) * 2004-04-20 2005-11-10 Snecma Moteurs Method for introducing a deliberate mismatch on a turbomachine bladed wheel, bladed wheel with a deliberate mismatch

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015158346A1 (en) * 2014-04-14 2015-10-22 Envision Energy (Denmark) Aps Asymmetric blade damper
EP3093485A1 (en) * 2015-05-11 2016-11-16 Blade Dynamics Limited A wind turbine blade
US10184448B2 (en) 2015-05-11 2019-01-22 Blade Dynamics Limited Wind turbine blade

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