Wind turbine blade comprising cylindrical metal inserts in a root region thereof

Abstract

A wind turbine blade for a wind turbine is a shell structure of a fiber-reinforced composite and comprises a root region and an airfoil region. The root region has a ring-shaped cross section and comprises a cylindrical insert 7 embedded in the fiber-reinforced polymer so as to substantially follow the circumference of the root region. The cylindrical insert is provided with a number of mutually spaced threaded bores 12, 15 in a first end 9 thereof being accessible from the outside.

Claims

1. A wind turbine blade for a wind turbine rotor comprising a hub from which the wind turbine blade extends when mounted to the hub, the wind turbine blade including a shell structure of a fibre-reinforced composite material comprising fibres embedded in a polymer matrix, the wind turbine blade extending in longitudinal direction and having a profiled contour including a pressure side and a suction side as well as a leading edge and a trailing edge, said edges defining a chord plane therebetween, when seen in the longitudinal direction the profiled contour comprising a root region with a root end face, an airfoil region and a transition region between the root region and the airfoil region, the root region having a ring-shaped cross section with an outer surface and an inner surface, the root region comprising a plurality of fastening means arranged so as to substantially follow the circumference of the root region and allow access from outside to the fastening means being used for mounting the blade to the hub, wherein an at least partly cylindrical metal insert made fully of metal comprising a plurality of said fastening means is at least partially embedded in the root region so as to essentially follow the circumference of the root region with the plurality of said fastening means of the at least partly cylindrical metal insert arranged so as to follow the ring-shaped cross-section of the root region, the at least partly cylindrical metal insert having a first end and a second end, a radially outer surface and a radially inner surface, and wherein the plurality of said fastening means is accessible at the first end of the insert.

2. The wind turbine blade according to claim 1, wherein the insert is a half cylinder, extending over 180 degrees in a circumferential direction.

3. The wind turbine blade according to claim 1, wherein the insert is a full cylinder, extending over 360 degrees in a circumferential direction.

4. The wind turbine blade according to claim 1, wherein the insert tapers from the first end towards the second end.

5. The wind turbine blade according to claim 4, wherein the insert tapers at least over a portion of a length thereof.

6. The wind turbine blade according to claim 4, wherein the insert tapers continuously.

7. The wind turbine blade according to claim 1, wherein the outer and/or inner surface of the insert is corrugated.

8. The wind turbine blade according to claim 1, wherein the insert is made of iron or steel.

9. The wind turbine blade according to claim 1, wherein the insert comprises metal fibres or wires fixed thereto and extending outwardly therefrom and being embedded in the polymer matrix of the fibre-reinforced composite material.

10. The wind turbine blade according to claim 9, wherein the metal fibres or wires are fixed to the outer and/or inner surface of the insert.

11. The wind turbine blade according to claim 9, wherein the metal fibres or wires are firmly fixed to the second end of the insert.

12. The wind turbine blade according to claim 9, wherein the metal fibres or wires are made of iron or steel.

13. The wind turbine blade according to claim 1, wherein the fastening means is a threaded hole.

14. The wind turbine blade according to claim 1, wherein the fastening means is a threaded rod.

15. The wind turbine blade according to claim 1, wherein the fibre-reinforced composite material of the root region comprises metal fibres.

16. The wind turbine blade according to claim 15, wherein the metal fibres are steel fibres or iron fibres.

17. The wind turbine of claim 1, wherein the fastening means are mutually spaced.

18. A wind turbine blade for a wind turbine rotor comprising a hub from which the wind turbine blade extends when mounted to the hub, the wind turbine blade including a shell structure of a fibre-reinforced composite material comprising fibres embedded in a polymer matrix, the wind turbine blade extending in longitudinal direction and having a profiled contour including a pressure side and a suction side as well as a leading edge and a trailing edge, said edges defining a chord plane therebetween, when seen in the longitudinal direction the profiled contour comprising a root region with a root end face, an airfoil region and a transition region between the root region and the airfoil region, the root region having a ring-shaped cross section with an outer surface and an inner surface, the root region comprising a plurality of fastening means arranged so as to substantially follow the circumference of the root region and allow access from outside to the fastening means being used for mounting the blade to the hub, wherein an at least partly cylindrical metal insert made fully of metal comprising a plurality of said fastening means is at least partially embedded in the root region so as to essentially follow the circumference of the root region, the at least partly cylindrical metal insert having a first end and a second end, a radially outer surface and a radially inner surface, and wherein the plurality of said fastening means is accessible at the first end of the insert, and wherein the insert is a half cylinder, extending over 180 degrees in a circumferential direction.

19. A wind turbine blade for a wind turbine rotor comprising a hub from which the wind turbine blade extends when mounted to the hub, the wind turbine blade including a shell structure of a fibre-reinforced composite material comprising fibres embedded in a polymer matrix, the wind turbine blade extending in longitudinal direction and having a profiled contour including a pressure side and a suction side as well as a leading edge and a trailing edge, said edges defining a chord plane therebetween, when seen in the longitudinal direction the profiled contour comprising a root region with a root end face, an airfoil region and a transition region between the root region and the airfoil region, the root region having a ring-shaped cross section with an outer surface and an inner surface, the root region comprising a plurality of fastening means arranged so as to substantially follow the circumference of the root region and allow access from outside to the fastening means being used for mounting the blade to the hub, wherein an at least partly cylindrical metal insert made fully of metal comprising a plurality of said fastening means is at least partially embedded in the root region so as to essentially follow the circumference of the root region, the at least partly cylindrical metal insert having a first end and a second end, a radially outer surface and a radially inner surface, and wherein the plurality of said fastening means is accessible at the first end of the insert, and wherein the insert is a full cylinder, extending over 360 degrees in a circumferential direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in greater detail below with reference to the drawings in which

(2) FIG. 1 shows a wind turbine,

(3) FIG. 2 is a diagrammatic perspective view of a wind turbine blade according to the invention,

(4) FIG. 3 is a perspective view of a portion of a root region of the first embodiment of a wind turbine blade according to the invention,

(5) FIG. 4 is a perspective view of a portion of a root region of a second embodiment of a wind turbine blade according to the invention,

(6) FIG. 5 is a cross-sectional view of the root region of a third embodiment of a wind turbine blade according to the invention,

(7) FIG. 6 shows a portion of a root region of a first embodiment of a wind turbine blade according to the invention provided with a first embodiment of a pre-made fastening device,

(8) FIG. 7 shows a portion of a root region of a second embodiment of a wind turbine blade according to the invention provided with a second embodiment of a pre-made fastening device,

(9) FIG. 8 shows a portion of a third embodiment of a fastening device formed by mutually connected fastening elements,

(10) FIG. 9 shows an additional embodiment of a fastening element for forming a half-cylindrical fastening element,

(11) FIG. 10 shows a cylindrical fastening element provided with metal fibres firmly attached to a second end thereof, and

(12) FIG. 11 shows a portion of a fastening device formed of mutually connected fastening elements having a convex and a concave lateral side wall.

DETAILED DESCRIPTION OF THE DRAWINGS

(13) FIG. 1 illustrates a conventional, modern upwind wind turbine 24 according to the so-called Danish concept with a tower 36, a nacelle 25 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 23 and three blades 2 extending radially from the hub 23, each having a blade root 31 nearest the hub, and a blade tip 32 furthest from the hub 23.

(14) As evident seen from FIG. 2, the blade 2 comprises a root region 26 with a root end face 29 closest to the hub, an airfoil region 27 furthest away from the hub, and a transition area 28 between the root region 26 and the airfoil region 27. The airfoil region 27 has an ideal or almost ideal blade shape, whereas the root region 26 has a substantially circular cross section, which reduces storm loads and makes it easier and safer to mount the blade 2 to the hub 23. Preferably, the diameter of the blade root 31 is constant along the entire root region 26. The transition region 28 has a shape gradually changing from the circular shape of the root region 26 to the airfoil profile of an airfoil region 27. The width of the transition region 28 increases substantially linearly with increasing distance from the hub 23.

(15) The blade is often made of two blades halves assembled by being glued or bolted together substantially along a chord plane 35 of the blade. In the embodiment described in the following the blade including the root region thereof is made in two blade halves. The blade 2 comprises a leading edge 34 facing the rotational direction of the blade 2 when the blade 2 is mounted on the hub 23 and a trailing edge 33 facing in the opposite direction of the leading edge 34. The chord plane 35 extends between the leading edge 34 and the trailing edge 33 of the blade 2. It should be noted that the chord plane does not necessarily run straight over its entire extent, since the blade may be twisted and/or curved, thus providing a 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. Due to the circular cross section, the root region 26 does not contribute to the production of the wind turbine and, in fact, it lowers the production slightly due to the wind resistance.

(16) As shown in FIG. 3-5 the blade including the root region is formed as a shell structure. The shell structure of the root region is ring-shaped and comprises an outer surface 3 formed by an outer layer 5 of a fibre-reinforced polymer matrix such as glass fibres and/or carbon fibres and/or metal fibres and a resin, such as epoxy, polyester or vinylester, and an oppositely arranged inner surface 4 formed by an inner layer 6 being made of the same material as the outer layer 5.

(17) As shown in FIG. 3-5 a half-cylindrical metal insert 7 is arranged between the outer 5 and inner 6 layer, i.e. embedded in the fibre-reinforced composite material formed by the above fibres and the above polymer.

(18) The semi-cylindrical metal insert 7 has a first end 9 and an opposite second end 10. The first end 9 of the insert 7 is arranged at a root end face 29 of the wind turbine blade. The insert 7 further has an outer surface 11 and an inner surface 14. Mutually spaced fastening means which in the shown embodiments are formed by inner threads 15 in a bore 12 extending into the insert from the first end 9 thereof.

(19) As seen from FIG. 3-5, the insert 7 is arranged so as to substantially follow the circumference of the root region. Correspondingly, the bores 12 with the threads 15 are arranged mutually spaced apart, so as to also substantially follow the circumference of the root region, and further so as to allow access thereto from the outside, so as to be able to engage bolts in the threads for mounting the blade to the hub of the wind turbine.

(20) In FIGS. 3 and 4 the semi-cylindrical insert 7 has a circular cross-section and a constant wall thickness over the entire length thereof. Further, in respect to FIGS. 3 and 4 it should be mentioned that these figures only disclose a portion of a root region of a blade half of a blade, which is manufactured by assembling two blade halves.

(21) FIG. 4 discloses an insert essentially corresponding to that shown in FIG. 3, however, being additionally provided with metal fibres 13, preferably steel or iron fibres or wires. As shown in FIG. 4, the metal fibres 13 have a first end 16 being firmly fixed to the second end 10 of the insert 7, and an outwardly extending portion 17 ending in a second end 18. The outwardly extending portion 17 of the fibres or wires is embedded in the fibre-reinforced composite material of the root region formed by the above mentioned fibres and polymer matrix. The outwardly extending fibres 13 assist in retaining the insert in the root region. Although it is not shown in FIG. 4, metal fibres may also be firmly fixed to the outer and/or inner surface 3, 4 of the insert 7 in order to thereby further improve the retention of the insert 7.

(22) FIG. 5 discloses a longitudinal sectional view of a portion of the root region of a wind turbine blade formed of two blade halves being mutually assembled. The insert 7 shown in FIG. 5 differs from those shown in FIGS. 3 and 4 in that the outer surface 11 thereof tapers as seen in the direction from the first end 9 of the insert, towards the second end 10 of the insert 7. Thereby, the thickness of the wall of the insert decreases from the first to the second end thereof. Metal fibres 13 are firmly fixed to the outer surface 11 of the insert 7, the inner surface 14 of the insert and to the second end 10 of the insert 7. The metal fibres extend outwardly from the mentioned surfaces and are embedded in the polymer matrix of the fibre-reinforced composite material of the root region. Finally, the insert 7 is provided with a number of mutually spaced bores 12 with an inner thread 15.

(23) Although it is not shown in any of the embodiments, the outer and inner surface of the insert may be corrugated or provided with another surface structure so as to improve the adherence between the mentioned surfaces and the polymer matrix.

(24) Additionally, it should be mentioned that the outer and/or inner surface may generally taper over the entire length thereof, or only over a portion thereof.

(25) Finally, it should be noted that the insert, instead of being a semi-cylindrical insert as shown in FIG. 3-5, could be a full cylindrical insert, i.e. extend over 360 degrees as seen in circumferential direction.

(26) FIG. 6 shows an embodiment similar to the one shown in FIG. 3. Therefore like parts are marked with the same reference numeral. In the embodiment shown in FIG. 6, the root region of the blades comprises a half-cylindrical fastening device 8, being formed by a number of elongated fastening members 7. Each fastening member comprises an outer periphery 11 comprising a radially outer surface 11a, an opposite radially inner surface 11b, a first lateral face 11c, and an opposite second lateral face 11d. Further, each fastening element is provided with a bore 12 with an inner thread 22. The fastening elements have a first end 9 and an opposite second end 10. The first ends of the fastening elements are arranged at the root end face 29 of the wind turbine blade.

(27) The elongated fastening elements 7 have an essentially rectangular or trapezium-shaped cross section and are mutually connected at lateral surfaces 11c, 11d thereof by said surfaces being welded together so as to form the semi-cylindrical fastening device 8. The semi-cylindrical fastening device 8 is arranged between an outer layer 5 of a fibre-reinforced polymer matrix advantageously of glass fibres and/or carbon fibres and an inner layer 6 formed of the same material as the outer layer 5. The outer layer 5 has an outer surface 3, and the inner layer 6 has an inner surface 4.

(28) In addition to comprising glass and/or carbon fibres, the inner and outer layer 6, 5 of the root region may also comprise other fibres such as metal fibres, preferably iron or steel fibres.

(29) The welded connection between the fastening elements 7 may be provided by providing a current to the fastening elements. The amperage of the current may be in the range between 1,500-2,500 Amps, in the range between 1,800-2,200 Amps, or in the range between 1,900-2,100 Amps. In this way, the adjacent surfaces of the adjacent fastening elements are directly connected to each other. It should, however, be noted that the adjacent surfaces of the fastening elements may also be connected by using a filler material.

(30) FIG. 7 shows an embodiment similar to the one shown in FIG. 4. Therefore like parts are marked with the same reference numeral. In the second embodiment shown in FIG. 7, the elongated fastening elements 7 being mutually connected to form the fastening device 8 are provided with metal fibres, preferably iron or steel fibres 13 firmly fixed thereto. As shown, the metal fibres 13 have a first fibre end 201 being firmly connected to the second end 10 of the fastening elements and an outwardly extending portion 203 having a second fibre end 202. The outwardly extending portion of the metal fibres is embedded in the polymer of the fibre-reinforced composite material of the root region.

(31) As shown in FIG. 7, the metal fibres extend from the second end 10 of the fastening elements 7 so as to form a fan, whereby the distance between the second end 202 of adjacent fibres on average is smaller than the distance between the first end of adjacent fibres. In an alternative embodiment the fibres extend substantially unidirectionally from the second end 10 of the fastening device 7. The fibres may be individual fibres or filaments or form a fabric.

(32) In the previously described embodiments, the fastening elements 7 of the fastening device 8 are provided with a constant cross-sectional area over the entire extend thereof.

(33) FIG. 8 discloses a portion of a third embodiment of a fastening device 108 formed of mutually connected fastening elements 107. In FIG. 8, two elongated fastening elements 107 are shown. They are abutting each other along lateral faces 111c, 111d and bonded to each other along these faces, such as by welding. Each elongated element 107 has a first end 109 and an opposite second end 110 and additionally a bore 112 provided with an inner thread 122. As seen in FIG. 8, the elongated elements 107 are tapering stepwise from the first end 109 thereof towards the second end 110 thereof. Further, it should be noted that the fastening elements 107 are provided with means illustrated by openings 114 for connecting metal fibres, preferably steel or iron fibres, to the second end 110 of the fastening elements 107.

(34) FIG. 9 illustrates an embodiment of an elongated fastening element 207 for forming a fastening device by mutually connecting a number of said fastening elements, the fastening element being shown as a constantly tapering second end 210 and a bore 212 provided with an inner thread 222.

(35) FIG. 10 discloses a fastening element 307 for forming a fastening device by connecting a number thereof so as to form the half-cylindrical fastening device. The elongated fastening element 307 has a circular cross section and is, at the second end 310 thereof, provided with a number of metal fibres preferably steel or iron fibres 13. The first fibre end 201 is firmly fixed to the second end 310 of the elongated fastening element 307, and a portion 203 of the metal fibres extends outwardly from said second end so as to be embedded in the polymer matrix of the fibre-reinforced composite material.

(36) FIG. 11 shows a portion of a fastening device 408 formed of mutually spaced elongated fastening elements 407. The fastening elements 407 are provided with a first lateral face 411c being convex, advantageously circular cylindrical, in a cross-sectional view and an opposite second lateral face 411c being concave, advantageously circular cylindrical, in a cross-sectional view. The first and the second lateral face abut each other and are mutually permanently connected such as by welding. Further, each fastening element 407 provided with a bore with a thread.

LIST OF REFERENCE NUMERALS

(37) 2 Wind turbine blade 3 Outer surface of root 4 Inner surface of root 5 Outer layer 6 Inner layer 7 Insert 7, 107, 207, 307, 407 Elongated fastening element 8, 108, 408 Fastening device 9 First end of insert 9, 109 First end of fastening element 10 Second end of insert 10, 210, 310 Second end of fastening element 11 Outer surface of insert/fastening element 11a Radially outer surface 11b Radially inner surface 11c, 111c, 411c First lateral face 11d, 111d, 411d Second lateral face 12, 112, 212, 412 Bore 13 Metal fibres 14 Inner surface of insert 15 Thread in bore 16 First end of fibres 17 Outwardly extending portion of fibres 18 Second end of fibres 22, 122, 222, 422 Inner thread 23 Hub 24 Wind turbine 25 Nacelle 26 Root region 27 Airfoil region 28 Transition region 29 Root end face 31 Blade root 32 Blade tip 33 Trailing edge 34 Leading edge 35 Chord plane 36 Tower 114 Opening 201 First fibre end 202 Second fibre end 203 Outwardly extending portion of metal fibres