Patent Application
20120027615
The present disclosure is directed in general to rotor blades, and more particularly to apparatus for allowing movement, such as twist, of the rotor blade with respect to inner structural members of the rotor blade.
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.
The construction of a modern rotor blade generally includes shell components, spar caps, and one or more shear webs. The shell components, typically manufactured from layers of fiber composite and a lightweight core material, forms the exterior aerodynamic foil shape of the rotor blade. The spar caps provide increased rotor blade strength by integrating one or more structural elements running along the span of the rotor blade on both interior sides of the rotor blade. Shear webs are structural beam-like components running essentially perpendicular between the top and bottom spar caps and extending across the interior portion of the rotor blade between the shell components.
The size, shape, and weight of rotor blades are factors that contribute to energy efficiencies of wind turbines. An increase in rotor blade size increases the energy production of a wind turbine, while a decrease in weight furthers the efficiency of a wind turbine. Furthermore, as rotor blade sizes grow, extra attention needs to be given to the structural integrity of the rotor blades. Presently, large commercial wind turbines in existence and in development are capable of generating from about 1.5 to about 12.5 megawatts of power. These larger wind turbines may have rotor blade assemblies larger than 90 meters in diameter. Additionally, advances in rotor blade shape encourage the manufacture of a forward swept-shaped rotor blade having a general arcuate contour from the base to the tip of the blade, providing improved aerodynamics. Accordingly, efforts to increase rotor blade size, decrease rotor blade weight, and increase rotor blade strength, while also improving rotor blade aerodynamics, aid in the continuing growth of wind turbine technology and the adoption of wind energy as an alternative energy source.
Rotor blades with such increases and improvements in size, shape, and weight may, however, have various disadvantages. For example, these rotor blades must be relatively flexible in order to prevent damage when experiencing high loading. Thus, for example, many such rotor blades may be formed from materials that allow bending towards the tower when experiencing high loading from, for example, high wind speeds. However, too much bending may cause a rotor blade to strike the tower, potentially causing damage to both the rotor blade and tower. Some blades are thus curved, as discussed above, to allow twisting of the rotor blade. Twisting of the rotor blade may allow for shedding of loads when high loads are experienced, which may help prevent a rotor blade from striking the tower. However, curving in many cases does not allow for sufficient twisting.
Thus, a rotor blade that can twist sufficiently to allow desirable levels of load shedding would be desired in the art.
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 for a wind turbine is disclosed. The rotor blade includes an outer shell having exterior surfaces and interior surfaces, the exterior surfaces defining a pressure side and a suction side each extending between a leading edge and a trailing edge, the interior surfaces defining a rotor blade interior. The rotor blade further includes a structural member extending through at least a portion of the interior, and a generally elastic material connecting the structural member to an interior surface. The generally elastic material allows movement of the outer shell with respect to the structural member.
In another embodiment, a rotor blade for a wind turbine is disclosed. The rotor blade includes an outer shell having exterior surfaces and interior surfaces, the exterior surfaces defining a pressure side and a suction side each extending between a leading edge and a trailing edge, the interior surfaces defining a rotor blade interior. The rotor blade further includes a structural member extending through at least a portion of the interior, the structural member movably connected to an interior surface such that passive movement of the outer shell is allowed with respect to the structural member.
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 to
The shell 20 may further have interior surfaces. The interior surfaces may define an interior 40 of the rotor blade 16. Further, the interior surfaces may include a pressure side interior surface 42, suction side interior surface 44, leading edge interior surface 46, and trailing edge interior surface 48.
The rotor blade 16 according to the present disclosure may include a plurality of individual rotor blade sections aligned in a generally span-wise, end-to-end, order between the blade tip 32 and the blade root 34. Each of the individual rotor blade sections may be uniquely configured so that the plurality of rotor blade sections define a complete rotor blade 16 having a designed aerodynamic profile, length, and other desired characteristics. For example, each of the rotor blade sections may have an aerodynamic profile that corresponds to the aerodynamic profile of adjacent rotor blade sections. Thus, the aerodynamic profiles of the rotor blade sections may form a continuous aerodynamic profile of the rotor blade 16.
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 52 and a span 54 extending in chord-wise and span-wise directions, respectively. As shown, the chord 52 may vary throughout the span 54 of the rotor blade 16.
In some embodiments, the outer shell 20 may additionally include a spar cap or spar caps (not shown). The spar caps may extend through at least a portion of the rotor blade 16, such as in the generally span-wise direction along at least a portion of the span 54. For example, in some embodiments, the outer shell 20 may include a pressure side spar cap and a suction side spar cap.
As shown in
In some embodiments, the structural member 60 may extend in a generally span-wise direction through at least a portion of the interior 40, and thus through at least a portion of the span 54. In other embodiments, however, the structural member 60 may extend in a generally chord-wise direction through at least a portion of the interior 40, or may extend in at any suitable angle or in any suitable direction through at least a portion of the interior.
A structural member 60 may be connected to the outer shell 20, such as to one or more interior surfaces of the outer shell 20. For example, a structural member 60 may be connected to any one or more interior surfaces adjacent to the pressure side 22, suction side 24, leading edge 26, and/or trailing edge 28, such as to any one or more of the pressure side interior surface 42, suction side interior surface 44, leading edge interior surface 46, and/or trailing edge interior surface 48. In some embodiments as shown, for example, a structural member 60 is connected to the interior surfaces adjacent to the pressure side 22 and the suction side 24, such as connected to the pressure side interior surface 42 and suction side interior surface 44. Further, the shear web may in some embodiments be connected to the spar caps of the outer shell 20.
The structural members 60 according to the present disclosure may allow passive movement of the outer shell 20 with respect to the structural members 60. Passive movement according to the present disclosure means movement due to external forces, such as high speed winds, rather than active movement, such as mechanical movement, of a structural member 60 to move the outer shell 20. Thus, the outer shell 20 may passively move linearly or rotate with respect to the structural member 60. This movement may generally occur due to loading of the rotor blade 16, such as from high speed winds or other forces. Further, after such loading has decreased or discontinued, the outer shell 20 to return to its approximate original position with respect to the structural member 60.
In some embodiments, for example, passive twisting of the outer shell 20 with respect to the structural member may occur. Twist is generally defined as rotation in twist direction 72, such as about an axis generally defined as extending in the direction of the span 54. However, it should be understood that the present disclosure is not limited to twist, and rather that any suitable movement, linearly and/or rotationally, is within the scope and spirit of the present disclosure.
For example, the rotor blade 16 according to the present disclosure may further include a generally elastic material 70. The material 70 connects a structural member 60 to an interior surface of the outer shell 20, as discussed above. The material 70 thus adheres the structural member 60 to the outer shell 20, allowing the structural member 60 to provide structural rigidity to the rotor blade 16.
The generally elastic material 70 may be, for example, an elastomer, such as a rubber. For example, the material 70 may be a saturated rubber, an unsaturated rubber, a thermoplastic elastomer, a resilin, an elastin, a polysulfide rubber, or any other suitable elastomer. Alternatively, the generally elastic material 70 may be any suitable material that allows movement of the outer shell 20 with respect to the structural member 60, as discussed below.
As mentioned, the generally elastic material 70 advantageously allows movement of the outer shell 20, such as any portion thereof, with respect to the structural member 60. Thus, the outer shell 20 may move linearly or may rotate with respect to the structural member 60 due to the generally elastic material 70. This movement may generally occur due to loading of the rotor blade 16, such as from high speed winds or other forces. Further, after such loading has decreased or discontinued, the generally elastic material 70 may allow the outer shell 20 to return to its approximate original position with respect to the structural member 60.
In some embodiments, for example, the material 70 may allow twist of the outer shell 20 with respect to the structural member. Twist is generally defined as rotation in twist direction 72, such as about an axis generally defined as extending in the direction of the span 54. However, it should be understood that the present disclosure is not limited to twist, and rather that any suitable movement, linearly and/or rotationally, is within the scope and spirit of the present disclosure.
In some embodiments, the material 70 may only allow the outer shell 20 to move within a certain specified range, and up to a certain maximum movement. For example, in some embodiments, the material 70 may only allow a specified twist of the outer shell 20 with respect to the structural member 60. For example, the material 70 may allow a maximum twist 74 of approximately 30 degrees, approximately 20 degrees, approximately 15 degrees, approximately 10 degrees, or any other suitable maximum twist range. It should be understood that the specified range, such as maximum twist, is a range in any direction from an original position. Thus, for example, with a maximum twist of approximately 30 degrees, for example, the outer shell 20 may be allowed to twist approximately 30 degrees in one twist direction as well as 30 degrees in the opposite twist direction.
As shown in
In some embodiments, as shown in
In other embodiments, as shown in
A stop 80 according to the present disclosure may extend throughout at least a portion of the structural member 60 in the direction that the structural member 60 extends with respect to the rotor blade 16. For example, in embodiments wherein the structural member 60 extends in a generally span-wise direction, the stop 80 may extend throughout at least a portion of the structural member in the span-wise direction.
It should be understood that the present disclosure is not limited to stops 80 as disclosed above, and rather that any suitable stop device that may prevent movement of the outer shell 20 with respect to the structural member 60 past a maximum movement is within the scope and spirit of the present disclosure.
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.
