US20120027588A1

US20120027588A1 - Root flap for rotor blade in wind turbine

Info

Publication number: US20120027588A1
Application number: US13/112,148
Authority: US
Inventors: Christian A. Carroll
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2011-05-20
Filing date: 2011-05-20
Publication date: 2012-02-02
Also published as: CN102797624A; DK178360B1; DK201270257A; DE102012104317A1

Abstract

A rotor blade assembly and a method for reducing the separation region of a rotor blade for a wind turbine are disclosed. The rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root. The rotor blade assembly further includes a flap extending in the generally span-wise direction from the root towards the tip. The flap includes an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge, the outer surface and at least one of the pressure side or the suction side defining a generally continuous aerodynamic surface.

Description

FIELD OF THE INVENTION

The present disclosure relates in general to wind turbine rotor blades, and more particularly to flaps mounted on the rotor blades.

BACKGROUND OF THE INVENTION

Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Rotor blades in general are increasing in size, in order to become capable of capturing increased kinetic energy. However, the shape of a typical wind turbine rotor blade results in a relatively large separation region, due to the contour of the rotor blade. Specifically, the contour of the inner portion of the rotor blade adjacent to and including the root may cause such separation. In some cases, this inner portion may include 40%, 50% or more of the rotor blade. The separation region causes relatively significant energy losses by creating drag. Further, these losses are amplified as rotor blade sizes are increased.
Thus, an improved rotor blade assembly would be advantageous. For example, a rotor blade assembly that reduces or eliminates the separation region adjacent to the root of the rotor blade would be desired.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, a rotor blade assembly for a wind turbine is disclosed. The rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root. The rotor blade assembly further includes a flap extending in the generally span-wise direction from the root towards the tip. The flap includes an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge, the outer surface and at least one of the pressure side or the suction side defining a generally continuous aerodynamic surface.
In another embodiment, a method for reducing the separation region of a rotor blade for a wind turbine is disclosed. The method includes mounting a flap to a rotor blade, and rotating the rotor blade on the wind turbine. The rotor blade has exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root. The flap extends in the generally span-wise direction from the root towards the tip. The flap includes an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge, the outer surface and at least one of the pressure side or the suction side defining a generally continuous aerodynamic surface.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 is a side view of a wind turbine according to one embodiment of the present disclosure;

FIG. 2 is a top perspective view of a rotor blade assembly according to one embodiment of the present disclosure;

FIG. 3 is a bottom perspective view of the rotor blade assembly of FIG. 2;

FIG. 4 is a top perspective view of a rotor blade assembly according to another embodiment of the present disclosure;

FIG. 5 is a bottom perspective view of the rotor blade assembly of FIG. 4;

FIG. 6 is a cross-sectional view of a rotor blade assembly according to one embodiment of the present disclosure;

FIG. 7 is a cross-sectional view of a rotor blade assembly according to another embodiment of the present disclosure;

FIG. 8 is a cross-sectional view of a rotor blade assembly according to another embodiment of the present disclosure;

FIG. 9 is a cross-sectional view of a rotor blade assembly according to another embodiment of the present disclosure;

FIG. 10 is a cross-sectional view of a rotor blade assembly according to another embodiment of the present disclosure; and,

FIG. 11 is a cross-sectional view of a rotor blade assembly according to another embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
FIG. 1 illustrates a wind turbine 10 of conventional construction. The wind turbine 10 includes a tower 12 with a nacelle 14 mounted thereon. A plurality of rotor blades 16 are mounted to a rotor hub 18, which is in turn connected to a main flange that turns a main rotor shaft. The wind turbine power generation and control components are housed within the nacelle 14. The view of FIG. 1 is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration.
Referring to FIGS. 2 through 11, a rotor blade 16 according to the present disclosure may include exterior surfaces defining a pressure side 22 and a suction side 24 extending between a leading edge 26 and a trailing edge 28, and may extend from a blade tip 32 to a blade root 34. The exterior surfaces may be generally aerodynamic surfaces having generally aerodynamic contours, as is generally known in the art.
In some embodiments, the rotor blade 16 may include a plurality of individual blade segments aligned in an end-to-end order from the blade tip 32 to the blade root 34. Each of the individual blade segments may be uniquely configured so that the plurality of blade segments define a complete rotor blade 16 having a designed aerodynamic profile, length, and other desired characteristics. For example, each of the blade segments may have an aerodynamic profile that corresponds to the aerodynamic profile of adjacent blade segments. Thus, the aerodynamic profiles of the blade segments may form a continuous aerodynamic profile of the rotor blade 16. Alternatively, the rotor blade 16 may be formed as a singular, unitary blade having the designed aerodynamic profile, length, and other desired characteristics.
The rotor blade 16 may, in exemplary embodiments, be curved. Curving of the rotor blade 16 may entail bending the rotor blade 16 in a generally flapwise direction and/or in a generally edgewise direction. The flapwise direction may generally be construed as the direction (or the opposite direction) in which the aerodynamic lift acts on the rotor blade 16. The edgewise direction is generally perpendicular to the flapwise direction. Flapwise curvature of the rotor blade 16 is also known as pre-bend, while edgewise curvature is also known as sweep. Thus, a curved rotor blade 16 may be pre-bent and/or swept. Curving may enable the rotor blade 16 to better withstand flapwise and edgewise loads during operation of the wind turbine 10, and may further provide clearance for the rotor blade 16 from the tower 12 during operation of the wind turbine 10.
The rotor blade 16 may further define a chord 42 and a span 44 extending in chord-wise and span-wise directions, respectively. As shown in FIGS. 2 through 5, the chord 42 may vary throughout the span 44 of the rotor blade 16. Thus, as discussed below, a local chord 46 may be defined for the rotor blade 16 at any point on the rotor blade 16 along the span 44. Further, the rotor blade 16 may define a maximum chord 48, as shown.
Additionally, the rotor blade 16 may define an inner board area 52 and an outer board area 54. The inner board area 52 may be a span-wise portion of the rotor blade 16 extending from the root 34. For example, the inner board area 52 may, in some embodiments, include approximately 33%, 40%, 50%, 60%, 67%, or any percentage or range of percentages therebetween, or any other suitable percentage or range of percentages, of the span 44 from the root 34. The outer board area 54 may be a span-wise portion of the rotor blade 16 extending from the tip 32, and may in some embodiments include the remaining portion of the rotor blade 16 between the inner board area 52 and the tip 32. Additionally or alternatively, the outer board area 54 may, in some embodiments, include approximately 33%, 40%, 50%, 60%, 67%, or any percentage or range of percentages therebetween, or any other suitable percentage or range of percentages, of the span 44 from the tip 32.
As illustrated in FIGS. 2 through 11, the present disclosure may further be directed to a rotor blade assembly 100. The rotor blade assembly 100 may include a flap 110 and the rotor blade 16. The flap 110 is a generally static flap mounted to the rotor blade 16 in the inner board area 52 of the rotor blade 100. The flap 110 extends in the generally span-wise direction from the root 34 towards the tip 32. Thus, one end of the flap 110 is positioned at the root 34, while the other end is positioned between the root 34 and the tip 32 in the inner board area 52. As discussed below, the flap alters the contour of a portion of the rotor blade 16 adjacent to the root 34. This alteration reduces or eliminates any separation region in this portion of the rotor blade 16, and further reduces the drag associated with the rotor blade 16 and increases the performance rotor blade 16.
The flap 110 includes an inner surface 112 and an outer surface 114, as shown in FIGS. 2 through 11. The inner surface 112 is conformingly mounted to at least one of the pressure side 22, the suction side 24, or the trailing edge 28. Thus, the aerodynamic contour of the inner surface 112 conforms to at least one of the pressure side 22, the suction side 24, or the trailing edge 28, such that when the flap 110 is mounted to the rotor blade 16, relatively little or no air may pass between the inner surface 112 and the pressure side 22, the suction side 24, and/or the trailing edge 28.
For example, FIGS. 2 through 7 and 9 illustrate various embodiments of an inner surface 112 conformingly mounted to a pressure side 22, suction side 24, and trailing edge 28 of a rotor blade 16. FIG. 6 illustrates one embodiment of an inner surface 112 mounted to a relatively minimal portion of the pressure side 22 and the suction side 24. FIG. 7 illustrates one embodiment of an inner surface 112 mounted to a relatively substantial portion of the suction side 24 and a relatively minimal portion of the pressure side 22. FIG. 9 illustrates another embodiment of an inner surface 112 mounted to a relatively minimal portion of the pressure side 22 and the suction side 24.
Further, FIG. 8 illustrates one embodiment of an inner surface 112 conformingly mounted to a pressure side 22 and trailing edge 28, wherein the inner surface 112 is mounted to a relatively substantial portion of the pressure side 22. FIGS. 10 and 11 illustrate various embodiment of an inner surface 112 conformingly mounted to a pressure side 22, wherein the inner surface 112 is mounted to a relatively substantial portion of the pressure side 22.
As mentioned above, in some embodiments, the inner surface 112 may be mounted to a relatively substantial portion of the pressure side 22 and/or suction side 24. This portion may be defined relative to the local chord 46. For example, the inner surface may be mounted to between approximately 20% and approximately 60%, such as between approximately 20% and approximately 50%, such as between approximately 20% and approximately 40%, such as between approximately 20% and approximately 30%, of the local chord 46 on the pressure side 22 and/or suction side 24. In other embodiments, the inner surface 112 may be mounted to a relatively minimal portion of the pressure side 22 and/or the suction side 24. This portion may also be defined relative to the local chord 46. For example, the inner surface may be mounted to between approximately 0% and approximately 20%, such as between approximately 0% and approximately 15%, such as between approximately 0% and approximately 10%, such as between approximately 0% and approximately 5%, of the local chord 46 on the pressure side 22 and/or suction side 24.
It should be understood that the inner surface 112 may be conformingly mounted to any one or more of the pressure side 22, the suction side 24, or the trailing edge 28, and further that the inner surface 112 may be mounted to a relatively substantial portion or a relatively minimal portion of any one or more of the pressure side 22, the suction side 24, or the trailing edge 28. Further, it should be understood that the relatively substantial portion and relatively minimal portion discussed above are not limited to the above disclosed ranges, and rather that any suitable range or percentage is within the scope and spirit of the present disclosure.
As shown in FIGS. 2 through 11, the outer surface 114 of the flap 110 defines a generally continuous aerodynamic surface with one or more of the exterior surfaces of the rotor blade 16. For example, the outer surface 114 and at least one of the pressure side 22 or the suction side 24 define a generally continuous aerodynamic surface. A generally continuous aerodynamic surface is a surface that has a generally continuous aerodynamic contour. Thus, when two surfaces define a generally continuous aerodynamic surface, there is relatively little interruption in the aerodynamic contour at the intersection of the two surfaces. As shown in FIGS. 2 through 7 and 9, for example, the outer surface 114 and the suction side 24 define a generally continuous aerodynamic surface. Further, in FIGS. 2 through 11, the outer surface 114 and the pressure side 22 define a generally continuous aerodynamic surface.
The outer surface 114 of the flap 110 may include a pressure side portion 122 and/or a suction side portion 124. The pressure side portion 122 may define a generally aerodynamic surface with the pressure side 22 of the rotor blade 16, as discussed above, while the suction side portion 124 may define a generally aerodynamic surface with the suction side 24, as discussed above. In some embodiments, the outer surface 114 of the flap 110 may include only the pressure side portion 122 and suction side portion 124, which may meet at both generally chord-wise ends of the flap 110, as shown in FIG. 11.
In other embodiments, however, the outer surface 114 may further include additional surfaces. For example, in some embodiments, as shown in FIGS. 2 through 10, the outer surface 114 may further include a planer portion 126. The planer portion 126 may extend between the pressure side portion 122 and the suction side portion 124, or between one of the pressure side portion 122 or suction side portion 124 and the inner surface 112.
The planer portion 126 in exemplary embodiments extends in the generally span-wise direction. Thus, in some embodiments the planer portion 126 may extend generally parallel to the span 44 of the rotor blade 16. Alternatively, however, the planer portion 126 may extend at any suitable angle to the span 44, as desired or required. In further alternative embodiments, the planer portion 126 may extend in any suitable angle relative to the rotor blade 16.
Further, as shown, the planer portion 126 in some embodiments is generally perpendicular to the local chord 46 of the rotor blade 16. Thus, as the planer portion 126 extends, such as in the generally span-wise direction, the planer portion 126 at any location may be generally perpendicular to the local chord 46 at that location. Alternatively, however, the planer portion 126 may be positioned at any suitable angle to perpendicular, or have any other suitable angle relative to the rotor blade 16.
In some embodiments, as shown in FIGS. 2 through 10, the flap 110 may extend in the generally chord-wise direction no further than the maximum chord 48 of the rotor blade 16. In these embodiments, at no location along the flap 110 in the generally span-wise direction does the flap 110 extend further than the maximum chord 48 of the rotor blade 16. In embodiments wherein the flap 110 includes a planer portion 126, the planer portion 126 may extend no further than the maximum chord 48 of the rotor blade 16. In embodiments wherein the flap 11 only includes a pressure side portion 122 and a suction side portion 124, neither the pressure side portion 122 nor the suction side portion 124 extends any further than the maximum chord 48 of the rotor blade 16. In other embodiments, as shown in FIG. 11, however, the flap 110 may extend in the generally chord-wise direction further than the maximum chord 48 of the rotor blade 16, as desired or required. In these embodiments, at any location along the flap 110 in the generally span-wise direction, the flap 110 may extend further than the maximum chord 48 of the rotor blade 16.
In some embodiments, as shown in FIGS. 2 through 5, the flap 110 may have a generally decreasing cross-sectional area in the span-wise direction towards the tip 32. Alternatively, however, the flap 110 may have a generally increasing cross-sectional area in the span-wise direction towards the tip 32, or may have a generally constant cross-sectional area.
The present disclosure may further be directed to a method for reducing the separation region of a rotor blade 16 for a wind turbine 10. The method includes the step of mounting a flap 110 to a rotor blade 16, as discussed above. The method further includes rotating the rotor blade 16 on the wind turbine 10.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A rotor blade assembly for a wind turbine, the rotor blade assembly comprising:

a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root; and,

a flap extending in the generally span-wise direction from the root towards the tip, the flap comprising an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge, the outer surface and at least one of the pressure side or the suction side defining a generally continuous aerodynamic surface.

2. The rotor blade assembly of claim 1, wherein the flap has a generally decreasing cross-sectional area in the span-wise direction towards the tip.

3. The rotor blade assembly of claim 1, wherein the flap extends in a generally chord-wise direction no further than a maximum chord of the rotor blade.

4. The rotor blade assembly of claim 1, wherein the outer surface of the flap comprises a pressure side portion and a suction side portion.

5. The rotor blade assembly of claim 4, wherein the outer surface of the flap further comprises a planer portion extending between the pressure side portion and suction side portion.

6. The rotor blade assembly of claim 5, wherein the planer portion extends in the generally span-wise direction.

7. The rotor blade assembly of claim 5, wherein the planer portion is generally perpendicular to a local chord of the rotor blade.

8. The rotor blade assembly of claim 5, wherein the planer portion extends no further than the maximum chord of the rotor blade.

9. The rotor blade assembly of claim 1, wherein the inner surface is conformingly mounted to the pressure side and the trailing edge.

10. The rotor blade assembly of claim 1, wherein the inner surface is conformingly mounted to the suction side and the trailing edge.

11. The rotor blade assembly of claim 1, wherein the inner surface is conformingly mounted to the pressure side, the suction side, and the trailing edge.

12. The rotor blade assembly of claim 1, wherein the outer surface and the pressure side define a generally continuous aerodynamic surface.

13. The rotor blade assembly of claim 1, wherein the outer surface and the suction side define a generally continuous aerodynamic surface.

14. A wind turbine, comprising:

a plurality of rotor blades, each of the plurality of rotor blades having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root; and,

a flap extending in the generally span-wise direction from the root towards the tip of at least one of the plurality of rotor blades, the flap comprising an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge of the at least one of the plurality of rotor blades, the outer surface and at least one of the pressure side or the suction side of the at least one of the plurality of rotor blades defining a generally continuous aerodynamic surface.

15. The wind turbine of claim 14, wherein the flap has a generally decreasing cross-sectional area in the span-wise direction towards the tip.

16. The wind turbine of claim 14, wherein the flap extends in a generally chord-wise direction no further than a maximum chord of the rotor blade.

17. The wind turbine of claim 14, wherein the outer surface of the flap comprises a pressure side portion and a suction side portion.

18. The wind turbine of claim 17, wherein the outer surface of the flap further comprises a planer portion extending between the pressure side portion and suction side portion.

19. The wind turbine of claim 14, wherein the inner surface is conformingly mounted to the pressure side, the suction side, and the trailing edge.

20. A method for reducing the separation region of a rotor blade for a wind turbine, the method comprising:

mounting a flap to a rotor blade, the rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending in a generally span-wise direction between a tip and a root, the flap extending in the generally span-wise direction from the root towards the tip, the flap comprising an inner surface and an outer surface, the inner surface conformingly mounted to at least one of the pressure side, the suction side, or the trailing edge, the outer surface and at least one of the pressure side or the suction side defining a generally continuous aerodynamic surface; and,

rotating the rotor blade on the wind turbine.