Patent Application
20220065218
The present disclosure relates generally to wind turbines, and more particularly to segmented rotor blades for wind turbines having a maximized pre-bend via an increased pre-bend in the blade tip segment thereof.
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, a generator, a gearbox, a nacelle, and a rotor having a rotatable hub with 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 rotor blades generally include a suction side shell and a pressure side shell typically formed using molding processes that are bonded together at bond lines along the leading and trailing edges of the blade. Further, the pressure and suction shells are relatively lightweight and have structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation. Thus, to increase the stiffness, buckling resistance and strength of the rotor blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web configured therebetween) that engage the inner pressure and suction side surfaces of the shell halves. The spar caps and/or shear web may be constructed of various materials, including but not limited to glass fiber laminate composites and/or carbon fiber laminate composites.
As wind turbines continue to increase in size, the rotor blades also increase in size. Thus, larger rotor blades may be constructed in segments that can be assembled on site via one or more pin joints. Increasing the blade length requires additional blade support because gravity pulls along the increased length to create a larger bending moment than in shorter rotor blades.
In addition, wind turbine rotor blades typically have a pre-bend in the flap-wise direction to ensure that the rotor blade does not contact the tower under loading. As such, the spar caps are primarily sized to prevent the rotor blade from contacting the tower. More specifically, the spar cap thickness of the rotor blade is often sized to meet tower clearance requirements. However, the mass of the rotor blades (which is desired to be as low as possible) is driven by the mass of the structural spar caps.
For a typical single-piece rotor blade, the amount of pre-bend is dictated due to shipping limits of the blade itself. More specifically, a rotor blade during transport must be oriented to fit within certain transportation limitations, such as a maximum height of transport and a minimum clearance to the ground. Therefore, such requirements potentially limit the amount of pre-bend in the rotor blade. However, a jointed rotor blade (specifically the tip segment of the blade) is not bound to the same transportation limitations as the blade tip segment is generally much shorter than the remaining portion of the blade.
Accordingly, the present disclosure is directed to blade tip segments for jointed rotor blades having an increased pre-bend so as to maximize the overall or overall pre-bend in the rotor blade so as to allow for lighter and less expensive spar caps.
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 aspect, the present disclosure is directed to a rotor blade for a wind turbine. The rotor blade includes a first blade segment and a second blade segment extending in opposite directions from a chord-wise joint. Each of the first and second blade segments has at least one shell member defining an airfoil surface and an internal support structure. The first blade segment defines a first pre-bend in a flap-wise direction. The second blade segment defines a different, second pre-bend in the flap-wise direction. Further, the first pre-bend is greater than the second pre-bend. In addition, the first and second pre-bends provide an overall pre-bend in the flap-wise direction away from a tower of the wind turbine that allows for a predetermined deflection of the rotor blade towards the tower.
In one embodiment, the first pre-bend may be greater than about 3 meters. More specifically, in one embodiment, the first pre-bend of the first blade segment may be greater than about 4 meters. In another embodiment, the second pre-bend of the second blade segment may be less than about 2 meters. As such, in certain embodiments, the overall pre-bend of the rotor blade may range from about 4 meters to about 6 meters. In another embodiment, the predetermined deflection of the rotor blade towards the tower may be greater than an allowed deflection for a non-jointed rotor blade, such as greater than about 5% of the total length of the rotor blade.
In further embodiments, due to the increased first pre-bend, a weight of the internal support structures of the first and second blade segments may be less than a weight of an internal support structure for the non-jointed rotor blade, such as a weight reduction of from about 1% to about 10% as compared to non-jointed rotor blades. In addition, the location of the weight (i.e. the mass moment) may also change which is further advantageous).
In additional embodiments, the chord-wise joint may be located from about 70% to about 90% of a span of the rotor blade from a blade root thereof, such as at about 85% span of the rotor blade from the blade root. In addition, in such embodiments, the first blade segment may correspond to a blade tip segment of the rotor blade, whereas the second blade segment may correspond to a blade root segment of the rotor blade.
In several embodiments, the first blade segment may include a beam structure having a receiving end with at least one span-wise extending pin extending therefrom. The second blade segment may include a receiving section that receives the beam structure of the first blade segment. The receiving section includes a chord-wise member having a pin joint slot defined therethrough. As such, the pin joint slot receives the span-wise extending pin at the receiving end of the beam structure so as to secure the first and second blade segments together.
In another aspect, the present disclosure is directed to a method of maximizing an overall blade pre-bend of a rotor blade. The method includes providing a first blade segment defining a first pre-bend in a flap-wise direction. The method also includes providing a second blade segment defining a different, second pre-bend in the flap-wise direction. Further, the first pre-bend is greater than the second pre-bend. Moreover, the method includes securing the first and second blade segments together in opposite directions from a chord-wise joint such that the first and second pre-bends provide an overall pre-bend in the flap-wise direction away from a tower of the wind turbine that allows for a predetermined deflection of the rotor blade towards the tower.
In one embodiment, as mentioned, the first blade segment may include a beam structure having a receiving end with at least one span-wise extending pin extending therefrom. The second blade segment may include a receiving section that receives the beam structure of the first blade segment. The receiving section includes a chord-wise member having a pin joint slot defined therethrough. In such embodiments, securing the first and second blade segments together in opposite directions from the chord-wise joint may include inserting the beam structure of the first blade segment into the receiving section of the second blade segment and securing the span-wise extending pin of the receiving end of the beam structure within the pin joint slot of the receiving section. It should be understood that the method may further include any of the additional features and/or steps as described herein.
In yet another aspect, the present disclosure is directed to a rotor blade for a wind turbine. The rotor blade includes a first blade segment and a second blade segment extending in opposite directions from a chord-wise joint. Each of the first and second blade segments include at least one shell member defining an airfoil surface and an internal support structure. Further, the first blade segment defines a first pre-bend in a flap-wise direction. The second blade segment is absent of a pre-bend in the flap-wise direction such that the first pre-bend defines an overall pre-bend in the flap-wise direction away from a tower of the wind turbine that allows for a predetermined deflection of the rotor blade towards the tower. It should be understood that the rotor blade may further include any of the additional features as described herein.
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.
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In one embodiment, the first pre-bend 68 may be greater than about 3 meters. More specifically, in one embodiment, the first pre-bend 68 of the first blade segment 30 may be greater than about 4 meters, such as about 4.5 meters. In another embodiment, the second pre-bend 74 of the second blade segment 32 may be less than about 2 meters. As such, in certain embodiments, the overall pre-bend 64 of the rotor blade 28 may range from about 4 meters to about 6 meters. In another embodiment, the predetermined deflection 76 of the rotor blade 28 towards the tower 12 may be greater than an allowed deflection for a non-jointed rotor blade, such as greater than about 5% of the total length of the rotor blade 28. In alternative embodiments, as shown in
In further embodiments, due to the increased first pre-bend 68 of the first blade segment 30, the weight of the internal support structures (e.g. such as the spar caps and shear web) of the first and second blade segments 30, 32 may be less than a weight of an internal support structure for a non-jointed rotor blade. For example, in one embodiment, the weight of rotor blades 28 of the present disclosure may be less than the weight of non-jointed rotor blades by about 1% to about 10%. In other words, due to the segmented configuration of the rotor blade 28, it is possible to have an exaggerated pre-bend in the first blade segment 30 (e.g. the blade tip segment), thereby allowing for more total deflection of the rotor blade 28. As such, since the rotor blade 28 can deflect more than a standard single-piece blade, the structural spar thickness can be decreased and the mass can also be reduced.
Referring now to
As shown at (102), the method 100 may include providing the first blade segment 30 defining the first pre-bend 68 in the flap-wise direction 72 away from the tower 12 of the wind turbine 10. As shown at (104), the method 100 may include providing the second blade segment 32 defining the different, second pre-bend 74 in the flap-wise direction 72. As shown at (106), the method 100 may include securing the first and second blade segments 30, 32 together in opposite directions from the chord-wise joint such that the first and second pre-bends 68, 74 provide the overall pre-bend 64 in the flap-wise direction 72 away from the tower 12 that allows for the predetermined deflection 76 of the rotor blade 28 towards the tower 12. For example, in one embodiment, securing the first and second blade segments 30, 32 together in opposite directions from the chord-wise joint 34 may include inserting the beam structure 40 of the first blade segment 30 into the receiving section 60 of the second blade segment 32 and securing the span-wise extending pin 52 of the receiving end 54 of the beam structure 40 within the pin joint slot 56 of the receiving section 60.
The skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
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.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/064851 | 12/11/2018 | WO | 00 |
