WIND TURBINE BLADE DAMPING DEVICE

Abstract

A blade damping device for damping vibrations during standstill of a wind turbine blade, wherein the blade damping device is adapted to be detachably attached to the pressure side and/or the suction side of the airfoil region of the wind turbine blade, the blade damping device comprising a base plate adapted to conform to the exterior shape of the wind turbine blade when the blade damping device is attached to the wind turbine blade, and a spoiler protruding from the base plate to a spoiler height along a height direction and having a spoiler length along a length direction, the height direction being adapted to extend outwardly from the wind turbine blade, wherein the spoiler height is adapted to be at least 20% of a chord line located at two thirds of the blade length along the longitudinal axis from the root end of the wind turbine blade.

Claims

1. A blade damping device for damping vibrations during standstill of a wind turbine blade having a root region with a root end and an airfoil region with a tip end between which ends a longitudinal axis of the blade extends, a leading edge and a trailing edge between which a chord line extends transversely to the longitudinal axis, and a pressure side and a suction side on opposite sides of the chord line, wherein the blade damping device is adapted to be detachably attached to the pressure side and/or the suction side of the airfoil region of the wind turbine blade, the blade damping device comprising: a base plate adapted to conform to the exterior shape of the wind turbine blade when the blade damping device is attached to the wind turbine blade, and a spoiler, such as a spoiler plate, protruding from the base plate to a spoiler height along a height direction and having a spoiler length along a length direction, the height direction being adapted to extend outwardly from the wind turbine blade, wherein the spoiler height is adapted to be at least 20% of a chord line length located at two thirds of the blade length along the longitudinal axis from the root end of the wind turbine blade.

2. A blade damping device according to claim 1, wherein the base plate is adapted to cover at most 50% of the circumference of the wind turbine blade when the blade damping device is attached to the wind turbine blade.

3. A blade damping device according to claim 1 wherein a resilient material of the base plate is adapted to conform to the exterior shape of the wind turbine blade when the blade damping device is attached to the wind turbine blade.

4. A blade damping device according to claim 1, wherein the blade damping device is adapted to be positioned on the blade at a first chord line so that the spoiler projected onto a plane normal to the first chord line has a distance along the longitudinal axis of the blade of at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, or 150% of the spoiler height.

5. A blade damping device according to claim 1, wherein the blade damping device is adapted to be positioned on the blade at a first chord line so that the height direction forms a second angle with respect to the first chord line of more than 0, 10, 20, 30, 40, 50, 60, 70, or 80 degrees, or the second angle is about 90 degrees.

6. A blade damping device according to claim 1, wherein the base plate is elongated along a longitudinal direction, the base plate being adapted to be arranged so that the longitudinal direction is parallel with respect to the longitudinal axis of the wind turbine blade, and wherein the spoiler is oriented with the length direction at an angle of 0 degrees to less than 90 degrees with respect to the longitudinal direction of the base plate.

7. A blade damping device according to claim 1, wherein the height direction is substantially perpendicular with respect to the base plate.

8. A blade damping device according to claim 1, wherein the blade damping device further comprises a first connector element, such as a first strap, adapted to detachably attach the blade damping device to the wind turbine blade.

9. A blade damping device according to claim 1, wherein the blade damping device further comprises a second connector element, such as a second strap, adapted to detachably attach the blade damping device to an adjacent blade damping device.

10. A blade damping device according to claim 1, wherein the base plate is adapted to extend from the suction or pressure side of wind turbine blade, around the trailing and/or leading edge to the opposite side of the wind turbine blade.

11. A blade damping device according to claim 1, wherein the blade damping device comprises or consists essentially of a foamed polymer material and/or the spoiler comprises one or more stiffening elements, such as one or more stiffening rods, which are optionally made of metal and optionally extending parallel to the

12. A kit of parts comprising: a wind turbine blade having a root region with a root end and an airfoil region with a tip end between which ends a longitudinal axis of the blade extends, a leading edge and a trailing edge between which a chord line extends transversely to the longitudinal axis, and a pressure side and a suction side on opposite sides of the chord line, and one or more blade damping devices according to claim 1.

13. A wind turbine blade comprising: a wind turbine blade having a root region with a root end and an airfoil region with a tip end between which ends a longitudinal axis of the blade extends, a leading edge and a trailing edge between which a chord line extends transversely to the longitudinal axis, and a pressure side and a suction side on opposite sides of the chord line, a first blade damping device according to claim 1, wherein the first blade damping device is detachably attached to the pressure side and/or the suction side of the airfoil region of the wind turbine blade so that the base plate of the first blade damping device conforms to the exterior shape of the wind turbine blade, and so that the height direction extends outwardly from the wind turbine blade, wherein the spoiler height is at least 20% of a chord line length located at two thirds of the blade length along the longitudinal axis from the root end of the wind turbine blade.

14. A method for damping vibrations of a wind turbine blade during standstill, comprising the steps of: providing a kit of parts according to claim 12, detachably attaching the one or more blade damping devices to the wind turbine blade, installing the wind turbine blade with the one or more blade damping devices on a hub of a wind turbine, and detaching the one or more blade damping devices from the wind turbine blade, preferably before commencing operation of the wind turbine blade.

15. A method according to claim 14, wherein the step of detachably attaching the one or more blade damping devices to the wind turbine blade is performed by attaching a first connector element to each of the one or more blade damping devices so that each first connector element extends around the circumference of the wind turbine blade and tightening each first connector element so as to detachably attach the one or more blade damping devices to the wind turbine blade.

16. A method according to claim 15, wherein the step of detaching the one or more blade damping devices from the wind turbine blade is performed by activating a release device of each first connector element.

17. A method according to claim 14, wherein the one or more blade damping devices include a first blade damping device and a second blade damping device, and wherein the method further comprises detachably attaching the first and second blade damping devices by a second connector element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of this disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0052] FIG. 1 is a schematic perspective view illustrating an exemplary wind turbine,

[0053] FIG. 2 is a schematic perspective view illustrating an exemplary wind turbine blade,

[0054] FIG. 3a is a schematic perspective view illustrating a first embodiment of an exemplary blade damping device with a straight rectangular shaped spoiler,

[0055] FIG. 3b is a schematic perspective view illustrating a first embodiment of an exemplary blade damping device with a straight trapezoidal shaped spoiler,

[0056] FIG. 3c is a schematic perspective view illustrating a first embodiment of an exemplary blade damping device with a straight round shaped spoiler,

[0057] FIG. 3d is a schematic perspective view illustrating a first embodiment of an exemplary blade damping device with a curved rectangular shaped spoiler,

[0058] FIG. 4a is a schematic perspective view illustrating a second embodiment of two second exemplary blade damping devices attached to a section of the airfoil region of a wind turbine blade,

[0059] FIG. 4b is a schematic cross-sectional slice view of the two second exemplary blade damping devices of FIG. 4a,

[0060] FIG. 5 is a schematic pressure side view illustrating the two second exemplary blade damping devices of FIG. 4a attached to a section of the wind turbine blade,

[0061] FIG. 6 is a schematic pressure side view of two pairs of third exemplary blade damping devices,

DETAILED DESCRIPTION OF THE INVENTION

[0062] FIG. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called “Danish concept” with a tower 4, a nacelle 6, and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8, and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.

[0063] FIG. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 extends along a longitudinal axis L.sub.1 with a root end 17 and a tip end 15 and has the shape of a conventional wind turbine blade which comprises a root region 12 closest to the hub, a profiled or an airfoil region 11 furthest away from the hub and a transition region 13 between the root region 12 and the airfoil region 11. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18. The blade 10 comprises a pressure side 22 between the leading edge 18 and the trailing edge 20 facing the incoming wind when mounted on the hub and a suction side (see FIG. 4b) on the opposite side of the blade 10. The airfoil region 11 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 12 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord line) of the root region 12 may be constant along the entire root region 12. The transition region 13 has a transitional profile gradually changing from the circular or elliptical shape of the root region 12 to the airfoil profile of the airfoil region 11. The chord line of the transition region 13 typically increases in length with increasing distance r from the hub. The airfoil region 11 has an airfoil profile with a chord line extending from the leading edge 18 to the trailing edge 20 of the blade 10. The length of the chord line decreases with increasing distance r from the hub. A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 13 and the airfoil region 11. It should be noted that the chord lines of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0064] FIG. 3a illustrates an exemplary blade damping device 41 of a first embodiment comprising a rectangular plate-shaped base part 50 and a spoiler 60. The base part 50 is elongated of about 1.5 metres along a longitudinal direction L.sub.2 which is intended to be arranged in parallel to the longitudinal axis L.sub.1 of the blade 10. The spoiler 60 protrudes perpendicularly from the base part 50 to a spoiler height of about 1 metre along a height direction H. This results in a spoiler height which is least 20% of a chord line located at two thirds of the blade length along the longitudinal axis L.sub.1 from the root end 17 of a typical wind turbine blade 10. The spoiler further extends to a spoiler length along a straight length direction L.sub.3 and to a suitable spoiler thickness to ensure mechanical stability along a thickness direction T. The length direction L.sub.3, thickness direction T, and height direction H are perpendicular. The longitudinal direction L.sub.2 of the base part 50 and the length direction L.sub.3 of the spoiler are arranged at about a 45 degree angle. This results in, when the longitudinal direction L.sub.2 of the base part 50 is positioned parallel to the longitudinal axis L.sub.1 of the blade 10, that the length direction L.sub.3 of the spoiler 60 oriented in a 45 degree angle with respect to the chord line C. The blade damping device comprises a flexible and resilient foamed polymer material so that the base part 50 conforms to the exterior shape of the wind turbine blade 10 when the blade damping device is attached to the wind turbine blade 10. FIG. 3b illustrates a similar blade damping device 41 with a trapezoidal shaped spoiler 60 extending along a straight length direction L.sub.3. FIG. 3c illustrates a similar blade damping device 41 with a round or semi-circular shaped spoiler 60 extending along a straight length direction L.sub.3. FIG. 3d illustrates a similar blade damping device 41 with a rectangular shaped spoiler 60 extending along a curved length direction L.sub.3.

[0065] FIGS. 4a, 4b, and 5 illustrates two exemplary blade damping devices 41a, 41b of a second embodiment including a pressure side blade damping device 41a and a suction side blade damping device 41b similar to the blade damping device of the first embodiment shown in FIG. 3a but with a base part elongated in a direction perpendicular to the longitudinal direction L.sub.2 so that the base part 50 of the pressure side blade damping device 41a extends from the pressure side 22 of the wind turbine blade 10 around the leading edge 18 to the suction side 24 of the wind turbine blade 10, and so that the base part 50 of the suction side blade damping device 41b extends from the suction side 24 of the wind turbine blade 10 around the trailing edge 20 to the pressure side 22 of the wind turbine blade 10. The blade damping devices 41a, 41b are positioned on the blade at a first chord line C.sub.1 located at a spanwise location of the blade as best seen in FIG. 4b. An adjacent chord line C is also shown in FIGS. 4a, 5 and 6. The base part 50 of each blade damping device 41a, 41b is oriented with the longitudinal direction L.sub.2 parallel to the longitudinal axis L.sub.1 so that the length direction L.sub.3 of the spoiler 60 forms a first 45 degree angle a.sub.1 with respect to the chord line C as best seen in FIG. 5, and so that the height direction H of the spoiler 60 forms a second 45 degree angle a.sub.2 with respect to a first chord line C.sub.1 as best seen in FIG. 4b. Further, the spoiler 60 projected onto a plane normal to the first chord line C has a length along the longitudinal axis L.sub.1 of the blade of about 1.5 times the spoiler height. A first connector element 70 in the form of a strap attaches the blade damping devices 41a, 41b to the wind turbine blade 10 by extending through the first attachment device 42 of each blade damping device 41a, 41b and around the circumference of the wind turbine blade 10 as best seen in FIG. 4b. The first connector element 70 can be detached by means of a release device (not shown), which upon activation, detaches the blade damping devices 41a, 41b from the wind turbine blade 10 e.g. by detaching ends of the first connector element 70.

[0066] FIG. 6 illustrate four exemplary blade damping devices 41c, 41d, 41e, 41f of a third embodiment similar to the blade damping devices 41a, 41b of FIGS. 4a, 4b, and 5 of the second embodiment only differing in that the length direction L.sub.3 of each spoiler 60 oriented parallel to the longitudinal direction L.sub.2 of each base part 50 and thus to the longitudinal axis L.sub.1 of the blade 10. The four blade damping devices 41c, 41d, 41e, 41f are divided in a first blade damping device pair 41c, 41d arranged at a first spanwise location of the blade 10 and a second blade damping device pair 41e, 41f arranged at a second spanwise location of the blade 10. One of the blade damping devices 41c, 41e of each pair is arranged on the pressure side 22 of the blade 10 and the other blade damping devices 41d, 41f of each pair is arranged on the suction side 24 of the blade 10. The first blade damping device pair 41c, 41d and the second blade damping device pair 41e, 41f are each attached to the blade 10 by first connector element 70a, 70b similar to the blade damping devices 41a, 41b of FIGS. 4a, 4b, and 5. The first blade damping device pair 41c, 41d is attached to the second blade damping device pair 41e, 41f by a second connector element 80 in the form of a strap attached to the second attachment devices 43c, 43e in the form of holes of each adjacent pressure side blade damping devices 41c, 41e. A third connector element 81 attaches the blade damping devices to the hub of the wind turbine. A fourth connector element 82 is attached to the blade damping devices and may act as a recovery line for recovering the blade damping devices when detaching them from the blade 10.

LIST OF REFERENCES

[0067] 2 wind turbine [0068] 4 tower [0069] 6 nacelle [0070] 8 hub [0071] 10 blade [0072] 11 airfoil region [0073] 12 root region [0074] 13 transition region [0075] 14 blade tip [0076] 15 tip end [0077] 16 blade root [0078] 17 root end [0079] 18 leading edge [0080] 20 trailing edge [0081] 22 pressure side [0082] 24 suction side [0083] 40 shoulder [0084] 41 blade damping device [0085] 41a pressure side blade damping device [0086] 41b suction side blade damping device [0087] 42 first attachment device [0088] 43 second attachment device [0089] 50 base part [0090] 60 spoiler [0091] 70 first connector element [0092] 72 release device [0093] 80 second connector element [0094] 81 third connector element [0095] 82 fourth connector element [0096] a.sub.1 first angle [0097] a.sub.2 second angle [0098] C chord line [0099] C.sub.1 first chord line [0100] H height direction [0101] L.sub.1 longitudinal axis [0102] L.sub.2 longitudinal direction [0103] L.sub.3 length direction [0104] T thickness direction