Patent Application
20220003202
The present disclosure relates generally to wind turbines, and more particularly to wind turbine rotor blade joints constructed of dissimilar materials with adapted coefficients of thermal expansion.
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.
In addition, as wind turbines continue to increase in size, the rotor blades also continue to increase in size. As such, modern rotor blades may be constructed in segments that are joined together at one or more joints. Further, certain jointed rotor blades may utilize pins at the joints to transfer the loads from the blade tip to the blade root. Moreover, the reactions from the pins are transferred to various bearing blocks at the joint locations via one or more bushings. Oftentimes, the bearing blocks may be constructed of polymer composites, whereas bushings within the bearing blocks that receive the pins are generally constructed of metal.
In certain instances, the rotor blades of the wind turbines need to be designed to withstand a wide range of temperatures, e.g. from about −40 degrees Celsius (° C.) to about 60° C. In such instances, the dissimilar materials in the rotor blade joints can cause thermally-induced stresses and/or problems maintaining required clearances between components. More specifically, the different coefficients of thermal of expansion between the dissimilar materials may compromise the structural integrity of the joint.
Accordingly, the present disclosure is directed to methods for joining dissimilar materials in a rotor blade that addresses the aforementioned issues.
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 includes at least one shell member defining an airfoil surface. The rotor blade also includes one or more pin joints for connecting the first and second blade segments at the chord-wise joint. The pin joint(s) includes one or more pin joint tubes received within the pin joint slot(s). Further, the pin joint slot(s) are secured within a load bearing block. Moreover, the pin joint slot(s) are constructed of a first material having a first coefficient of thermal expansion, whereas the load bearing block is constructed of a second material having a second coefficient of thermal expansion. In addition, the first and second coefficients of thermal expansion are substantially equal so as to maintain contact (such as e.g. an interference fit) between the one or more pin joint slots and the load bearing block during operational temperature changes of the wind turbine.
In one embodiment, the first material may be a metal material and the second material may be a composite material. In another embodiment, the pin joint slot(s) may be bushings. In yet another embodiment, the operational temperature changes of the wind turbine may include temperature changes ranging from about −40 degrees Celsius (° C.) to about 60° C.
In further embodiments, the composite material may include a thermoset resin or a thermoplastic resin. In addition, the composite material may optionally be reinforced with one or more fiber materials to achieve a predetermined fiber content. For example, in such embodiments, the predetermined fiber content may be greater than about 55%, such as from about 56% to about 60%. In another embodiment, the fiber material(s) may include, for example, glass fibers, carbon fibers, polymer fibers, wood fibers, bamboo fibers, ceramic fibers, nanofibers, metal fibers, or combinations thereof. In additional embodiments, the metal material may include steel, aluminum, or titanium.
In several embodiments, the first and second coefficients of thermal expansion may be substantially equal plus or minus 20%.
In another aspect, the present disclosure is directed to a method for manufacturing a joint assembly of a rotor blade of a wind turbine. The method includes forming one or more pin joint slots of a first material having a first coefficient of thermal expansion. The method also includes forming at least one load bearing block of a second material such that a second coefficient of thermal expansion of the load bearing block is substantially equal to the first coefficient of thermal expansion so as to maintain contact between the pin joint slot(s) and the load bearing block during operational temperature changes of the wind turbine. Further, the load bearing block having one or more openings. In addition, the method may include placing the one or more pin joint slots within the opening(s) of the load bearing block of the first blade segment and/or the second blade segment.
In one embodiment, forming the load bearing block of the composite material to have the second coefficient of thermal expansion may include reinforcing the composite material with a fiber and/or resin content that will either increase or decrease an original coefficient of thermal expansion of the composite material by a predetermined percentage. It should be understood that the method may further include any of the additional steps and/or features as described herein.
In yet another aspect, the present disclosure is directed to a bearing block assembly. The bearing block assembly includes a bearing block that defines one or more openings. The bearing block assembly also includes one or more pin joint slots received within the one or more openings of the bearing block. The pin joint slot(s) are constructed of a metal material having a first coefficient of thermal expansion, whereas the bearing block constructed of a composite material having a second coefficient of thermal expansion. The first and second coefficients of thermal expansion are substantially equal so as to maintain contact between the one or more pin joint slots and the bearing block during operational temperature changes of the bearing block assembly. It should be understood that the bearing block 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.
Referring now to the drawings,
Referring now to
Referring now to
Moreover, as shown, the first blade segment 30 may include one or more first pin joints towards a first end 54 of the beam structure 40. In one embodiment, the pin joint may include a pin that is in a tight interference fit with a bush. More specifically, as shown, the pin joint(s) may include at least one pin tube 52 located on the beam structure 40. Thus, as shown, the pin tube 52 may be oriented in a span-wise direction. It should be understood that the pin tubes described herein may include any suitable pin, bolt, fastener, or similar.
Further, the first blade segment 30 may also include a pin joint slot 50 located on the beam structure 40 proximate to the chord-wise joint 34. Moreover, as shown, the pin joint slot 50 may be oriented in a chord-wise direction. In one example, there may be a bushing within the pin joint slot 50 arranged in a tight interference fit with a pin tube or pin (shown as pin 53 in
It is to be noted that the pin tube 52 located at the first end of the beam structure 40 may be separated span-wise with the multiple second pin joint tubes 56, 58 located at the chord-wise joint 34 by an optimal distance D. This optimal distance D may be such that the chord-wise joint 34 is able to withstand substantial bending moments caused due to shear loads acting on the chord-wise joint 34. In another embodiment, each of the pin joints connecting the first and second blade segments 30, 32 may include an interference-fit steel bushed joint.
Referring now to
Referring now to
Referring now to
Referring to
In the present disclosure, however, the first and second coefficients of thermal expansion of the dissimilar materials are substantially equal so as to maintain contact between the pin joint slot(s) 62, 64 and the bearing block 68 during operational temperature changes of the wind turbine 10. In several embodiments, the first and second coefficients of thermal expansion may be substantially equal, e.g. plus or minus 20%. In other words, the bearing block 68 of the present disclosure may be custom designed for the operational temperature of the wind turbine 10 to avoid the aforementioned issues. In one embodiment, the operational temperature changes of the wind turbine 10 may include temperature changes ranging from about −40 degrees Celsius (° C.) to about 60° C. Thus, the bearing block 68 may be designed to withstand the entire ranges of potential temperatures.
For example, in one embodiment, the composite material of the bearing block 68 may include a thermoset resin or a thermoplastic resin. In addition, the composite material of the bearing block 68 may optionally be reinforced with one or more fiber materials to achieve a predetermined fiber content. For example, in such embodiments, the predetermined fiber content may be greater than about 55%, such as from about 56% to about 60%. Thus, by increasing the fiber content of the composite material, the coefficient of thermal expansion of the composite material is reduced. Accordingly, by knowing the coefficient of thermal expansion of the metal material of the pin joint slot(s) 62, 64, the materials of the bearing block 68 can be specifically chosen such that the coefficient of thermal expansion therefore substantially matches the metal.
The metal material of the bushing(s) 62, 64 described herein may include, for example, steel, aluminum, titanium, or any other suitable metal or metal alloy. The thermoplastic materials described herein may generally encompass a plastic material or polymer that is reversible in nature. For example, thermoplastic materials typically become pliable or moldable when heated to a certain temperature and returns to a more rigid state upon cooling. Further, thermoplastic materials may include amorphous thermoplastic materials and/or semi-crystalline thermoplastic materials. For example, some amorphous thermoplastic materials may generally include, but are not limited to, styrenes, vinyls, cellulosics, polyesters, acrylics, polysulphones, and/or imides. More specifically, exemplary amorphous thermoplastic materials may include polystyrene, acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), glycolised polyethylene terephthalate (PET-G), polycarbonate, polyvinyl acetate, amorphous polyamide, polyvinyl chlorides (PVC), polyvinylidene chloride, polyurethane, or any other suitable amorphous thermoplastic material. In addition, exemplary semi-crystalline thermoplastic materials may generally include, but are not limited to polyolefins, polyamides, fluropolymer, ethyl-methyl acrylate, polyesters, polycarbonates, and/or acetals. More specifically, exemplary semi-crystalline thermoplastic materials may include polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polypropylene, polyphenyl sulfide, polyethylene, polyamide (nylon), polyetherketone, or any other suitable semi-crystalline thermoplastic material.
Further, the thermoset materials as described herein may generally encompass a plastic material or polymer that is non-reversible in nature. For example, thermoset materials, once cured, cannot be easily remolded or returned to a liquid state. As such, after initial forming, thermoset materials are generally resistant to heat, corrosion, and/or creep. Example thermoset materials may generally include, but are not limited to, some polyesters, some polyurethanes, esters, epoxies, or any other suitable thermoset material.
In addition, the fiber materials described herein may include but are not limited to glass fibers, carbon fibers, polymer fibers, wood fibers, bamboo fibers, ceramic fibers, nanofibers, metal fibers, or combinations thereof. In addition, the direction or orientation of the fibers may include quasi-isotropic, multi-axial, unidirectional, biaxial, triaxial, or any other another suitable direction and/or combinations thereof
Referring now to
As shown at (102), the method 100 may include providing the pin joint slot(s) 62, 64 of a metal material having a first coefficient of thermal expansion. As shown at (104), the method 100 may include forming the bearing block 68 of a composite material such that a second coefficient of thermal expansion of the bearing block 68 is substantially equal to the first coefficient of thermal expansion so as to maintain contact between the pin joint slot(s) and the bearing block 68 during operational temperature changes of the wind turbine 10. Further, the bearing block 68 has one or more openings 65, 67. For example, in one embodiment, the bearing block 68 may be formed by reinforcing the composite material with a fiber content that will either increase or decrease an original coefficient of thermal expansion of the composite material by a predetermined percentage. Thus, the resulting coefficient of thermal expansion of the composite material substantially matches that of the metal material of the pin joint slot(s) 62, 64. As shown at (106), the method 100 may include securing the pin joint slot(s) 62, 64 within the openings 65, 67 of the bearing block 68.
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/US2018/058680 | 11/1/2018 | WO | 00 |
