Aeroelastic stable wind turbine blade

Abstract

A wind turbine blade comprising a plurality of spar components extending along the longitudinal axis and providing the main bending stiffness of the wind turbine blade a major principal axis defining a structural pitch angle of at least 1° with respect to a chord line, and including: one or more suction-side spar caps each having a centre line; one or more pressure-side spar caps each having a centre line; and one or more shear webs distributed around a central shear web line and at least one of which being connected to first spar caps, wherein at least one suction-side spar cap centre lines is arranged with a first chordwise distance to the central shear web line, and at least one pressure-side spar cap centre lines is arranged with a second, different, chordwise distance to the central shear web line.

Claims

1. A wind turbine blade extending along a longitudinal axis from a root to a tip, the wind turbine blade comprising a root region and an airfoil region with the tip, the wind turbine blade comprising a chord line extending between a leading edge and a trailing edge, the wind turbine blade comprising: a shell providing an aerodynamic airfoil shape of the wind turbine blade and comprising a pressure side and a suction side; and a plurality of spar components extending along the longitudinal axis and providing the main bending stiffness of the wind turbine blade, and including: one or more suction-side spar caps arranged adjacent to the suction side of the shell and including at least a first suction-side spar cap, the one or more suction-side spar caps each having a centre line; one or more pressure-side spar caps arranged adjacent to the pressure side of the shell and including at least a first pressure-side spar cap, the one or more pressure-side spar caps each having a centre line; and one or more shear webs extending in parallel to and being distributed, preferably equally, around a central shear web line, at least one shear web having a suction-side end connected to the first suction-side spar cap and a pressure-side end connected to the first pressure-side spar cap; wherein the one or more suction-side spar caps and the one or more pressure-side spar caps provide the main bending stiffness of the wind turbine blade along a major principal axis defining a structural pitch angle of at least 1° with respect to the chord line at least in a first region of the wind turbine blade, and wherein at least one centre line of the one or more of suction-side spar caps is arranged with a first chordwise distance to the central shear web line at least in the first region of the wind turbine blade, and wherein at least one centre line of the one or more of pressure-side spar caps is arranged with a second chordwise distance to the central shear web line at least in the first region of the wind turbine blade, the second chordwise distance being different from the first chordwise distance.

2. A wind turbine blade according to claim 1, wherein one or more suction-side spar caps further has an aggregated suction-side centre line being arranged with the first chordwise distance to the central shear web line at least in the first region of the wind turbine blade, and the one or more pressure-side spar caps further has an aggregated pressure-side centre line being arranged with the second chordwise distance to the central shear web line at least in the first region of the wind turbine blade, the second chordwise distance being different from the first chordwise distance.

3. A wind turbine blade according to claim 2, wherein the central shear web line extends through the aggregated suction-side centre line or through the aggregated pressure-side centre line.

4. A wind turbine blade according to claim 1, wherein the first suction-side spar cap has a first suction-side chordwise width at least in the first region of the wind turbine blade, and the first pressure-side spar cap has a first pressure-side chordwise width at least in the first region of the wind turbine blade, the first chordwise widths being different.

5. A wind turbine blade according to claim 1, wherein the one or more suction-side spar caps additionally comprises a second suction-side spar cap arranged adjacent to the suction side of the shell and positioned between the first suction-side spar cap and one of the leading and trailing edges of the wind turbine blade, and/or wherein the one or more pressure-side spar caps additionally comprise a second pressure-side spar cap arranged adjacent to the pressure side of the shell and positioned between the first pressure-side spar cap and the other one of the leading and trailing edges of the wind turbine blade.

6. A wind turbine blade according to claim 5, wherein the first suction-side spar cap and the first pressure-side spar cap are substantially reflection symmetric with respect to the chord line.

7. A wind turbine blade according to claim 1, wherein the second suction-side spar cap is positioned at a first suction-side distance to the first suction-side spar cap at least in the first region of the wind turbine blade, and/or wherein the second pressure-side spar cap is positioned at a first pressure-side distance to the first pressure-side spar cap at least in the first region of the wind turbine blade, wherein the first suction-side distance and/or the first pressure-side distance are in the range of 0% to 50% of the width of the respective second spar cap.

8. A wind turbine blade according to claim 1, wherein the second suction-side spar cap is positioned at a second suction-side distance from the leading and trailing edges at least in the first region of the wind turbine blade, and/or wherein the second pressure-side spar cap is positioned at a second pressure-side distance from the leading and trailing edges at least in the first region of the wind turbine blade, wherein the second suction-side distance and/or the second pressure-side distance is equal to or greater than 100% of the chordwise width of the respective second spar cap.

9. A wind turbine blade according to claim 1, wherein the first suction-side spar cap, preferably the second suction-side spar cap, the first pressure-side spar cap, and preferably the second pressure-side spar cap comprise a transversely isotropic material, e.g. a unidirectional fibre material, at least in the first region of the wind turbine blade, and wherein the respective centre lines thereof are geometric centre lines.

10. A wind turbine blade according to claim 1, wherein the first spar caps and/or second spar caps are fibre-reinforced laminate structures and each has a respective primary fibre direction oriented at least partially, preferably mainly, along the longitudinal axis of the wind turbine blade.

11. A wind turbine blade according to claim 10, wherein the first suction-side spar cap and/or the first pressure-side spar cap comprise a first material being glass fibres, carbon fibres, natural fibres, wood fibres, and/or a mixture thereof, e.g. a mixture of glass and carbon fibres.

12. A wind turbine blade according to claim 10, wherein the second suction-side spar cap and/or the second pressure-side spar cap comprise a second material being glass fibres, carbon fibres, natural fibres, wood fibres, and/or a mixture thereof, e.g. a mixture of glass and carbon fibres.

13. A wind turbine blade according to claim 11, wherein the second material, e.g. glass fibres, being different from the first material, e.g. carbon fibres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Embodiments of the present disclosure will be described in more detail in the following with regard to the accompanying figures. Like reference numerals refer to like elements throughout. Like elements may, thus, not be described in detail with respect to the description of each figure. 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. In addition, an illustrated embodiment does not need to have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiment even if not so illustrated, or if not so explicitly described.

[0080] FIG. 1 is a schematic diagram illustrating a perspective view of an exemplary wind turbine,

[0081] FIG. 2 is a schematic diagram illustrating a perspective view of an exemplary wind turbine blade illustrating cross-sectional line A-A, and

[0082] FIGS. 3A-7C are schematic diagrams illustrating a cross-sectional view along cross-sectional line A-A of FIG. 2 of different spar cap arrangements of a wind turbine blade.

DETAILED DESCRIPTION OF THE INVENTION

[0083] 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 which may include a tilt angle of a few degrees. 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.

[0084] FIG. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade 10 extending along a longitudinal axis L between a root end 17 and a tip end 15 and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The airfoil region 34 includes a tip region 36 with the tip end 15. 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 8, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0085] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 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) of the root region 30 may be constant along the entire root region 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing radial distance from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing radial distance from the hub.

[0086] 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 32 and the airfoil region 34.

[0087] It should be noted that the chords 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.

[0088] The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together with adhesive, such as glue, along bond lines or glue joints extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 have a semi-circular or semi-oval outer cross-sectional shape. The blade shell parts 24, 26 define the aerodynamic shape of the wind turbine blade and comprise a plurality of spar components extending along the longitudinal axis and provide the main bending stiffness of the blade 10.

[0089] Turning to FIGS. 3A-7C, different arrangements of the plurality of spar components 62, 65, 72, 75, 80 are illustrated. Overall, the plurality of spar components comprises one or more suction-side spar caps 62, 65 arranged adjacent to the suction side of the shell and one or more pressure-side spar caps 72, 75 arranged adjacent to the pressure side of the shell.

[0090] The one or more suction-side spar caps include at least a first suction-side spar cap 62 as shown in all FIGS. 3A-7C but may also further include a second suction-side spar cap 65 as shown in FIGS. 5B-5C, 6B-6C, and 7B-7C. Further, the one or more suction-side spar caps 62, 65 each have a suction-side spar cap centre line 63, 66, respectively, forming part of a plurality of suction-side spar cap centre lines. Further, the one or more suction-side spar caps 62, 65 have an aggregated suction-side centre line 61.

[0091] Correspondingly, the one or more pressure-side spar caps include at least a first pressure-side spar cap 72 as shown in all FIGS. 3A-7C but may also further include a second pressure-side spar cap 75 as shown in FIGS. 3B-3C, 4B-4C, and 7A-7C. Further, the one or more pressure-side spar caps 72, 75 each have a plurality of pressure-side centre lines 73, 76, respectively, forming part of a plurality of suction-side spar cap centre lines. Further, the one or more pressure-side spar caps 72, 75 in combination have an aggregated pressure-side centre line 71.

[0092] In all of the shown embodiments except for FIG. 7C, the plurality of spar components further comprises a single shear web 80 extending along a central shear web line 81 and having a suction-side end 82 connected to the first suction-side spar cap 61 and a pressure-side end 83 connected to the first pressure-side spar cap 71. However, more shear webs 80 may be included and distributed around the central shear web line 81 as shown in FIG. 7C. The central shear web line 81 extends perpendicularly to the chord line C.

[0093] The one or more suction-side spar caps 62, 65 and one or more pressure-side spar cap 72, 75 are arranged asymmetrically so as to provide the main bending stiffness of the wind turbine blade along a major principal axis P defining a structural pitch angle α of at least 1° (shown exaggerated in FIGS. 3A-7C for illustrative purposes) with respect to the chord line C at least in a first region of the wind turbine blade 34. In these cases, the first section is equivalent to the airfoil region 34 as shown in FIG. 2 but in other embodiments the first section may be a subset of the airfoil region 34.

[0094] Common for all the illustrated embodiments is that at least one of the plurality of suction-side centre lines 61, 63, 66 is arranged with a first chordwise distance to the central shear web line 81, and that at least one of the plurality of pressure-side centre lines 71, 73, 76 is arranged with a second chordwise distance to the central shear web line 81, and the second chordwise distance is different from the first chordwise distance. For instance in FIG. 3A, the aggregated suction-side centre line 61 (which coincides with the first suction-side spar cap centre line) is arranged with a chordwise distance of zero to the central shear web line 81 while the aggregated pressure-side centre line 71 is distanced from the central shear web line 81 due to the increased width of the first pressure-side spar cap 72 relative to the first suction-side spar cap 62. Correspondingly in FIG. 7B, the chordwise distance of the second suction-side spar cap centre line 66 is different from the chordwise distance of both the aggregated 71 and the first pressure-side spar cap centre line 63, both with respect to the central shear web line 81.

[0095] Further, the first 62, 72 and second spar caps 65, 75 are fibre-reinforced laminate structures each consisting essentially of a transverse isotropic composite material in the form of layers of unidirectional fibres embedded in a resin matrix: unidirectional carbon fibres for the first spar caps 62, 72 and unidirectional glass fibres for the second spar caps 65, 75. The unidirectional fibres are oriented along the longitudinal axis L.

[0096] FIGS. 3A-6C, 7A, and 7C illustrate embodiments with a difference in chordwise distances of respective aggregated spar cap centre lines 61, 71 and FIGS. 3A-6C illustrate embodiments in which the central shear web line 81 extends through the aggregated suction-side spar cap centre line 61 or the aggregated pressure-side spar cap centre line 71.

[0097] FIGS. 3B-3C, 4B-4C, 5B-5C, 6B-6C, and 7C illustrate embodiments in which the first suction-side spar cap 62 and the first pressure-side spar cap 72 are substantially reflection symmetric with respect to the chord line C. In these embodiments, the central shear web line 81 also extends through both centre lines 63, 73 of the first spar caps 62, 72 (which coincide with the corresponding aggregated centre line in embodiments with a single respective spar cap, e.g. on the suction side in FIGS. 3A-4C).

[0098] In FIGS. 3B, 4B, 5B, 6B, 7A, and 7B the second spar caps 65, 75 are arranged adjacent or even in contact with the first spar caps 62, 72 and thus have a corresponding first chordwise distance of approximately 0% of the chordwise width of the respective second spar cap 65, 75.

[0099] In FIGS. 3C, 4C, 5C, 6C, and 7C the second spar caps 65, 75 are distanced from the first spar caps 62, 72.

TABLE-US-00001 LIST OF REFERENCES 2 wind turbine 4 tower 6 nacelle 8 hub 10 blade 11 root blade segment 12 tip blade segment 13 shell 14 blade tip 15 tip end 16 blade root 17 root end 18 leading edge 20 trailing edge 24 pressure side 26 suction side 30 root region 32 transition region 34 airfoil region 36 tip region 40 shoulder 50 plurality of spar components 61 aggregated suction-side centre line 62 first suction-side spar cap 63 first suction-side spar cap centre line 65 second suction-side spar cap 66 second suction-side spar cap centre line 71 aggregated pressure-side centre line 72 first pressure-side spar cap 73 first pressure-side spar cap centre line 75 second pressure-side spar cap 76 second pressure-side spar cap centre line 80 shear web 81 central shear web line 82 suction-side end 83 pressure-side end L longitudinal axis C chord line P major principal axis α structural pitch angle