WIND TURBINE ROTOR BLADE WITH A SUCTION SIDE WINGLET
A rotor blade for a wind turbine is disclosed. The rotor blade may comprise a root portion, a tip, and a body extending between the root portion and the tip. The body may include a pressure side and a suction side. Additionally, a winglet may be defined by the body. The winglet may terminate at the tip of the rotor blade and extend inwardly in a direction of the suction side of the body. Further, a bend may be defined in the body such that a portion of the body extends outwardly in a direction of the pressure side of the body.
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The present subject matter relates generally to rotor blades for a wind turbine and, more particularly, to wind turbine rotor blades with suction side winglets.
BACKGROUND OF THE INVENTIONWind 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 from wind using known airfoil principles and transmit the kinetic energy through rotational energy 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.
To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size, configuration and capacity of wind turbines. One such modification has been to include a wingtip device, such as a winglet, at the tip of each wind turbine rotor blade. Generally, winglets can be employed to improve the overall efficiency and performance of a wind turbine. For example, a winglet may decrease the amount of spanwise flow generated at the tip of a rotor blade and, thereby, reduce drag on the rotor blade. Winglets may also be installed on rotor blades to reduce the overall diameter of the wind turbine as well as to reduce noise emitted by the blades. Further, winglets may also provide an increase in the power coefficient of a wind turbine and, thus, reduce the cost of energy generated by the wind turbine.
While the various performance advantages, described above, can be provided to a wind turbine by both winglets extending away from the wind turbine tower (i.e., pressure side winglets) and winglets extending towards the tower (i.e., suction side winglets), it is generally understood that the greatest performance advantages can provided by a suction side winglet. However, for wind turbines having rotors upwind of the tower, suction side winglets can be very problematic. Specifically, installing a suction side winglet on a conventional rotor blade reduces the distance between the tip of the rotor blade and the tower. Such a reduction in tower clearance can dramatically increase the risk of one or more of the rotor blades striking the tower. When a tower strike occurs, the rotor blade and the tower can be significantly damaged and, in some instances, a tower strike can even bring down the entire wind turbine. Thus, tower strikes are very costly and require considerable downtime to repair or replace damaged components.
Accordingly, there is a need for a rotor blade that can accommodate a suction side winglet without increasing the likelihood of the rotor blade striking the tower.
BRIEF DESCRIPTION OF THE INVENTIONAspects 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 aspect, the present subject matter discloses a rotor blade for a wind turbine. The rotor blade comprises a root portion, a tip, and a body extending between the root portion and the tip. The body includes a pressure side and a suction side. Additionally, a winglet may be defined by the body. The winglet may terminate at the tip of the rotor blade and extend inwardly in a direction of the suction side of the body. Further, a bend may be defined in the body such that a portion of the body extends outwardly in a direction of the pressure side of the body.
In another aspect, the present subject matter discloses a wind turbine. The wind turbine may include a tower and a nacelle mounted atop the tower. A rotor may be coupled to the nacelle and may include a hub. The wind turbine may also include at least one rotor blade extending from the hub. The rotor blade may define a suction side winglet extending inwardly in a direction of the tower. Additionally, a bend may be defined in the rotor blade such that a portion of the rotor blade extends outwardly in a direction away from the tower.
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.
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:
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.
The rotor blades 22 may generally be spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. Specifically, the hub 20 may be rotatably coupled to an electric generator (not illustrated) positioned within the nacelle 16 to permit electrical energy to be produced. Further, the rotor blades 22 may be mated to the hub 20 by coupling a blade root portion 24 to the hub 20 at a plurality of load transfer regions 26. Thus, any loads induced to the rotor blades 22 are transferred to the hub 20 via the load transfer regions 26.
As shown in the illustrated embodiment, the wind turbine 10 may also include a turbine control system or turbine controller 36 centralized within the nacelle 16. However, it should be appreciated that the turbine controller 36 may be disposed at any location on or in the wind turbine 10, at any location on the support surface 14 or generally at any other location. The controller 36 may be configured to control the various operating modes of the wind turbine 10 (e.g., start-up or shut-down sequences). Additionally, the controller 36 may be configured to control a pitch angle or blade pitch of each of the rotor blades 22 (i.e., an angle that determines a perspective of the rotor blades 22 with respect to the direction 28 of the wind) to control the load and power generated by the wind turbine 10 by adjusting an angular position of at least one rotor blade 22 relative to the wind. For instance, the controller 36 may control the blade pitch of the rotor blades 22, either individually or simultaneously, by controlling a pitch adjustment system 32. Pitch axes 34 for the rotor blades 22 are shown. Further, as the direction 28 of the wind changes, the controller 36 may be configured to control a yaw direction of the nacelle 16 about a yaw axis or the center line 38 of the tower 12 to position the rotor blades 22 with respect to the direction 28 of the wind. For example, the controller 36 may control a yaw drive mechanism (not illustrated) of the nacelle 16 in order to rotate the nacelle 16 about the tower center line 38
During operation of the wind turbine 10, wind strikes the rotor blades 22 from a direction 28, which causes the rotor 18 to rotate about an axis of rotation 30. As the rotor blades 22 are rotated and subjected to centrifugal forces, the rotor blades 22 are also subjected to various forces and bending moments. Thus, the rotor blades 22 may deflect from a neutral or non-deflected position to a deflected or loaded position, thereby reducing the tower clearance between the blade 22 and the tower 12. In order to monitor the position of the blades 22 and reduce the likelihood of a tower strike, a predetermined tower clearance threshold 54 (
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The second bend 60 defined in the rotor blade 40 may generally be configured such that the suction side winglet 52 extends inwardly a direction of the suction side 48 of the blade 40 (i.e., in a direction towards the tower 12). Thus, in one embodiment, the second bend 60 may generally define the interface between the angled portion 56 and the suction side winglet 52, with the suction side winglet 52 extending from the second bend 60 to the tip 42 of the rotor blade 40. Additionally, when the transition between the angled portion 56 and the winglet 52 is curved, such as when the second bend 60 is configured as a curved bend, the suction side winglet 52 may generally comprise a hooked winglet and, thus, define a radius (not illustrated) at the interface of the angled portion 56 and the winglet 52.
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X(t)=(1−t)3x1+3t(1−t)2x3+3t2(1−t)x4+t3x2
Y(t)=(1−t)3y1+3t(1−t)2y3+3t2(1−t)y4+t3y2
wherein: t is an independent variable that must take on a value between 0 and 1. However, it should be appreciated that the rotor blade 40 need not be configured as a cubic Bezier curve and, thus, may generally be configured consistent with various other suitable mathematical models known in the art.
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Moreover, it should be appreciated that the bends 58,60 may be configured to account for any variations between the magnitude of deflection exhibited by the rotor blade 40 of the present subject matter due to wind conditions and the typical deflection exhibited by a conventional rotor blade 22. For example, if the rotor blade 40 of the present subject matter is more stiff and, thus, exhibits less deflection than a conventional blade 22, the distance that the rotor blade 40 needs to be bent away from the tower 12 may be reduced. Alternatively, if the rotor blade of the present subject matter is configured such that it deflects further towards the tower 12 due to wind conditions than a conventional blade 22, the bends 58,60 can be designed to account for such additional deflection.
Further, it should be appreciated that the rotor blade 40 of the present subject matter may be manufactured by any suitable means known in the art. In one embodiment, the entire rotor blade 40 may be molded or otherwise formed as a single piece. Alternatively, the rotor blade 40 may be formed in segments. Thus, in one embodiment, the suction side winglet 52 may be formed as a separate component and then secured to the body 44 of the rotor blade 40 by any suitably means. In another embodiment, the angled portion 56 and the suction side winglet 52 may each be molded as separate segments and then combined with any other segments to form the rotor blade 40. In an even further embodiment, the angled portion 56 and suction side winglet 52 may be molded or otherwise formed as one single segment and thereafter combined with the remainder of the body 44 to create the rotor blade 40.
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 for a wind turbine, the rotor blade comprising:
- a root portion;
- a tip; and,
- a body extending between said root portion and said tip, said body comprising a pressure side and a suction side, said body including a first bend and a second bend, said first bend being defined in said body between 0% and about 80% of a total length of the rotor blade such that a portion of said body extends outwardly in a direction of said pressure side; and,
- a suction side winglet formed in said body between said second bend and said tip, said suction side winglet extending inwardly in a direction of said suction side such that said tip is substantially aligned with a pitch axis of the rotor blade or is disposed between said pitch axis and a tower of the wind turbine.
2. (canceled)
3. The rotor blade of claim 1, wherein said portion of said body extends outwardly in a direction of said pressure side between said first bend and said second bend.
4. (canceled)
5. The rotor blade of claim 1, wherein said first bend defines a bend angle of less than about 60 degrees.
6. (canceled)
7. The rotor blade of claim 1, wherein said first bend is defined in said body between 0% and about 60% of the total length of the rotor blade.
8. The rotor blade of claim 1, wherein said suction side winglet has a height equal to less than about 20% of the total length of the rotor blade.
9. The rotor blade of claim 1, wherein said body defines a curved profile between said first bend and said tip.
10. (canceled)
11. A wind turbine, comprising:
- a tower;
- a nacelle mounted atop said tower;
- a rotor coupled to said nacelle, said rotor comprising a hub; and,
- at least one rotor blade extending from said hub, said at least one rotor blade comprising: a root portion; a tip; and, a body extending between said root portion and said tip, said body including a first bend and a second bend, said first bend being defined in said body between 0% and about 80% of a total length of said at least one rotor blade such that a portion of said body extends in a direction away from said tower; and,
- a suction side winglet formed in said body between said second bend and said tip, said suction side winglet extending inwardly in a direction towards said tower such that said tip is substantially aligned with a pitch axis of said at least one rotor blade or is disposed between said pitch axis and said tower.
12. The wind turbine of claim 11, wherein said at least one rotor blade is configured to maintain said tip at or beyond a tower clearance threshold during operation of the wind turbine.
13. (canceled)
14. The wind turbine of claim 11, wherein said portion of said body extends in a direction away from said tower between said first bend and said second bend.
15. (canceled)
16. The wind turbine of claim 11, wherein said first bend defines a bend angle of less than about 60 degrees.
17. (canceled)
18. The wind turbine of claim 11, wherein said suction side winglet has a height equal to less than about 20% of said total length of said at least one rotor blade.
19. The wind turbine of claim 11, wherein said at least one rotor blade defines a curved profile between said first bend and said tip.
20. (canceled)
21. The rotor blade of claim 1, wherein said suction side winglet extends inwardly in a direction of said suction side substantially perpendicularly to a centerline of the tower.
22. The rotor blade of claim 5, wherein said bend angle ranges from about 10 degrees to about 45 degrees.
23. The rotor blade of claim 8, wherein said height ranges from about 5% to about 20% of the total length of the rotor blade.
24. The rotor blade of claim 9, wherein said curved profile is configured as a cubic Bezier curve.
25. The wind turbine of claim 11, wherein said first bend is defined in said body between 0% and about 60% of said total length of said at least one rotor blade.
26. The wind turbine of claim 11, wherein said suction side winglet extends inwardly in a direction of said tower substantially perpendicularly to a centerline of said tower.
27. The wind turbine of claim 16, wherein said bend angle ranges from about 10 degrees to about 45 degrees.
28. The wind turbine of claim 19, wherein said curved profile is configured as a cubic Bezier curve.
Type: Application
Filed: Jul 16, 2010
Publication Date: Jun 16, 2011
Applicant: GENERAL ELECTRIC COMPANY (Schenectady, NY)
Inventors: Klaus Ulrich Koegler (Rheine), Ramesh Vedula (Bangalore), Ariane Myriam Daisy Frère (Muenster)
Application Number: 12/837,529
International Classification: F03D 11/00 (20060101);