Patent Application
20140328688
The present application claims filing benefit of Indian Patent Application 1313/DEL/2013 having a filing date of May 3, 2013, which is incorporated herein by reference in its entirety.
The present disclosure relates in general to wind turbines, and more specifically to rotor blade assemblies therefor which include vortex generators.
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 are the primary elements of wind turbines for converting wind energy into electrical energy. The blades have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to the generator for producing electricity.
The lift force is generated when the flow from the leading edge to the trailing edge creates a pressure difference between the top and bottom surfaces of the blade. Ideally, the flow is attached to the top surface from the leading edge to the trailing edge. However, when the angle of attack of the flow exceeds a certain critical angle, the flow does not reach the trailing edge, but leaves the surface at a flow separation line. Beyond this line, the flow direction is generally reversed, i.e. it flows from the trailing edge backward to the separation line. A blade section extracts much less energy from the flow when it separates.
Flow separation depends on a number of factors, such as incoming air flow characteristics (e.g. Reynolds number, wind speed, in-flow atmospheric turbulence) and characteristics of the blade (e.g. airfoil sections, blade chord and thickness, twist distribution, pitch angle, etc). The detached-flow region also leads to an increase in drag force, mainly due to a pressure difference between the upstream attached-flow region and the downstream detached-flow region. Flow separation tends to be more prevalent nearer the blade root due to the relatively great angle of attack of the blade flow surfaces in this region as compared to the blade tip.
Hence, in order to increase the energy conversion efficiency during normal operation of the wind turbine, it is desired to increase the lift force of the blades while decreasing the drag force. To this purpose, it is advantageous to increase the attached-flow region and to eliminate or at least reduce the detached-flow region by moving flow separation nearer the trailing edge of the blade. This is particularly desirable nearer to the blade root in order to increase the overall lift generated by the blade.
It is known in the art to change the aerodynamic characteristics of wind turbine blades by adding dimples, protrusions, or other structures on the surface of the blade. These structures are often referred to as “vortex generators” and serve to create local regions of turbulent airflow over the surface of the blade as a means to delay flow separation and thus optimize aerodynamic airflow around the blade contour. Conventional vortex generators are typically sheet metal and defined as “fins” or shaped structures on the suction side of the turbine blade.
Conventional vortex generators are not, however, without drawbacks. For example, improper placement and sizing of conventional vortex generators can lead to significant drag as well as ineffectiveness in maintaining and increasing the attached-flow region.
Accordingly, improved wind turbine rotor blades are desired in the art. In particular, rotor blades which utilize vortex generators having specific arrangements and/or sizing which increase attached-flow regions and thus overall wind turbine efficiency, would be advantageous.
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 each extending between a tip and a root. The rotor blade further defines a span and a chord. The rotor blade assembly further includes a plurality of vortex generators configured on at least one of the suction side or the pressure side and disposed within an inboard area of the rotor blade. The plurality of vortex generators include a row of vortex generators extending in a generally span-wise direction, the row comprising a first portion of vortex generators and and a second portion of vortex generators, the second portion of vortex generators spaced apart from the first portion of vortex generators in the span-wise direction. Each first portion vortex generator is disposed at a first chord-wise location, and each second portion vortex generator is disposed at a second chord-wise location different from the first chord-wise location.
In another embodiment, a vortex generator assembly for a wind turbine rotor blade is disclosed. The vortex generator assembly includes a plurality of vortex generators arranged in a single row and configured for mounting on at least one of a suction side or a pressure side of the wind turbine rotor blade. The plurality of vortex generators comprises a first portion of vortex generators and a second portion of vortex generators. The second portion of vortex generators is arranged to be spaced apart from the first portion of vortex generators in a span-wise direction. Each first portion vortex generator is arranged to be disposed at a first chord-wise location, and each second portion vortex generator is arranged to be disposed at a second chord-wise location different from the first chord-wise location.
In another 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 each extending between a tip and a root. The rotor blade further defines a span and a chord. The rotor blade assembly further includes at least one vortex generator configured on at least one of the suction side or the pressure side of the rotor blade, the at least one vortex generator having an aspect ratio between approximately 4 and approximately 10.
In another 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 each extending between a tip and a root. The rotor blade further defines a span and a chord. The rotor blade assembly further includes at least one vortex generator configured on at least one of the suction side or the pressure side of the rotor blade, the at least one vortex generator having a length between approximately 4% and approximately 20% of a local chord.
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.
Referring now to
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 chord 42 and a span 44. As shown in
Additionally, the rotor blade 16 may define an inboard area 52 and an outboard area 54. The inboard area 52 may be a span-wise portion of the rotor blade 16 extending from the root 34. For example, the inboard area 52 may, in some embodiments, include approximately 25%, 33%, 40%, 50%, 60%, 67%, 75% 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 outboard 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 inboard area 52 and the tip 32. Additionally or alternatively, the outboard area 54 may, in some embodiments, include approximately 25% 33%, 40%, 50%, 60%, 67%, 75% 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
Vortex generators 102 can be configured on a surface of the rotor blade 16 through any suitable mounting technique or apparatus. For example, suitable adhesives can be utilized to bond a vortex generator 102 to a surface of the rotor blade 16. Alternatively, suitable mechanical fasteners, such as nails, screws, rivets, nut-bolt combinations, etc., can be utilized to attach a vortex generator 102 to a surface of the rotor blade 16. Still further, in other alternative embodiments, welding, brazing, or other suitable techniques can be utilized to connect a vortex generator 102 to a surface of the rotor blade 16. Additionally, in some embodiments (not shown) a vortex generator 102 may include a mounting plate for mounting of the vortex generator 102 to a surface of the rotor blade 16.
Any suitable vortex generators 102 are within the scope and spirit of the present disclosure. In exemplary embodiments, as shown in the figures, a vortex generator 102 includes a fin 110. The fin 110 may be configured on a rotor blade 16 surface such that it extends therefrom, thus defining a height 112 (such as a maximum height). The fin 110 may further define a length 114 (such as a maximum length) as shown, which may be defined between a forward end 116 and an aft end 118. In exemplary embodiments as shown, the fin 110 may extend generally linearly between the forward end 116 and the aft end 118, although in alternative embodiments the fin 110 may so extend in a generally curvilinear fashion or otherwise. Further, the fin 110 may have any suitable cross-sectional shape. For example, in some embodiments, a fin 110 may have a square or rectangular cross-sectional shape. In other embodiments, the fin 110 may have a trapezoidal cross-sectional shape, with the sidewalls tapering inwards from a bottom of the fin to a top of the fin or, alternatively, tapering outwards. In other embodiments, only portions of the sidewalls of a fin 110 may taper. In still other embodiments, a fin 110 may have an oval, triangular, or other suitable polygonal shaped cross-section.
A vortex generator 102 may further be configured on a rotor blade 16 at any suitable orientation. For example, a vortex generator 102 may be aligned with a local chord 46, such that for example, a length 114 thereof is parallel to the local chord 46, or a vortex generator 102 may be angled to the local chord 46.
Vortex generators 102 according to the present disclosure are oriented and/or sized to advantageously increase the overall performance and efficiency of the rotor blade assembly 100 and wind turbine 10 in general. The present inventors have discovered that conventional vortex generators are relatively inefficient and, in some cases, adversely affect the performance of rotor blade assemblies 100. Further, the present inventors have discovered that particular orientations and/or sizing of vortex generators 102 as discussed herein advantageously increase rotor blade assembly 100 and wind turbine 10 performance and efficiency, in some cases surprisingly increasing wind turbine efficiency by 1-2%.
For example,
It should be noted that span-wise and chord-wise locations according to the present disclosure are determined based on the position of the forward end 116 of the vortex generator 102. Thus, a disclosure of a vortex generator 102 disposed at a particular chord-wise location and/or span-wise location means that the forward end 116 of the vortex generator 102 is positioned at that location.
As further illustrated in
In some embodiments, the first portion 130 and second portion 132 are discrete from each other in the chord-wise direction, such that no other vortex generators 102 are between the portions 130, 132 in the span-wise or chord-wise direction and such that there is no transition between the portions 130, 132, as shown in
Referring again to
It should be noted, referring now to
Referring now to
Referring still to
Additionally or alternatively, one or more vortex generators 102 may have particular heights 112 and/or lengths 114 that provide such advantageous performance and efficiency benefits. For example, a vortex generator 102 may have a height 112 between approximately 0.5% and approximately 4% of the local chord 46 for that vortex generator 102, such as between approximately 0.5% and approximately 3% of the local chord 46 for that vortex generator 102, such as between approximately 1.0% and approximately 4% of the local chord 46 for that vortex generator 102, such as between approximately 1.5% and approximately 4% of the local chord 46 for that vortex generator 102, such as between approximately 1.0% and approximately 3% of the local chord 46 for that vortex generator 102, such as between approximately 1.5% and approximately 3% of the local chord 46 for that vortex generator 102. Further, a vortex generator 102 may have a length 114 between approximately 4% and approximately 20% of the local chord 46 for that vortex generator 102, such as between approximately 7% and approximately 15% of the local chord 46 for that vortex generator 102.
Further, referring to
It should be understood that the above-disclosed heights and lengths are not limited to use in first portion 130 vortex generators 102, and rather may apply to any suitable vortex generators 102. As shown in
In some embodiments, as shown in
It should be noted that the present disclosure is further directed to vortex generator assemblies. Such assemblies include the plurality of vortex generators 102 as discussed herein, which may be arranged in a row having various orientations and/or sizes. Such vortex generators 102 may thus be arranged to be disposed at orientations as discussed herein and/or may be sized relative to a rotor blade 16 as discussed herein. A vortex generator assembly may thus include the plurality of vortex generators 102, and may further in some embodiments include one or more mounting plates. Such mounting plates may mount the vortex generators 102 on the rotor blade 16, and may further serve to locate and orient the vortex generators 102 relative to the rotor blade 16.
As discussed, vortex generators 102, rotor blade assemblies 100, and wind turbines 10 according to the present disclosure may have orientations and/or sizes that advantageously improve the performance and efficiency thereof. In some embodiments, the relative offset positioning of various portions of vortex generators 102 provides such advantageous performance characteristics. In additional or alternative embodiments, the relatively larger sizing of the vortex generators 102 as compared to conventional vortex generators provides such advantageous performance characteristics. These advantages may be particularly pronounced in embodiments wherein these vortex generators 102 are disposed in the inboard area 52, such as in embodiments wherein at least a portion of these vortex generators 102 are between the root 34 and the span-wise maximum chord 48 location.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1313/DEL/2013 | May 2013 | IN | national |
