Patent Application
20190120203
The present subject matter relates generally to wind turbine rotor blades of and, more particularly, to wind turbine rotor blade components formed using pultruded rods.
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 from wind using known foil 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.
Wind turbine rotor blades generally include a body shell formed by two shell halves of a composite laminate material. The shell halves are generally manufactured using molding processes and then coupled together along the corresponding ends of the rotor blade. In general, the body shell is relatively lightweight and has 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. In addition, wind turbine blades are becoming increasingly longer in order to produce more power. As a result, the blades must be stiffer and thus heavier so as to mitigate loads on the rotor.
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 surfaces of the shell halves. The spar caps may be constructed of various materials, including but not limited to glass fiber laminate composites and/or carbon fiber laminate composites. Such materials, however, can be difficult to control, defect prone, and/or highly labor intensive due to handling of the dry and pre-preg fabrics and the challenges of infusing large laminated structures.
As such, spar caps may also be constructed of pre-fabricated, pre-cured (i.e. pultruded) composites that can be produced in thicker sections, and are less susceptible to defects. In addition, the use of pultrusions in spar caps can decrease the weight thereof and may also increase the strength thereof. Accordingly, the pultruded composites can eliminate various concerns and challenges associated with using dry fabric alone. As used herein, the terms “pultruded composites,” “pultrusions,” “pultruded members” or similar generally encompass reinforced materials (e.g. fibers or woven or braided strands) that are impregnated with a resin and pulled through a stationary die such that the resin cures or undergoes polymerization through added heat or other curing methods. As such, the process of manufacturing pultruded composites is typically characterized by a continuous process of composite materials that produces composite parts having a constant cross-section. A plurality of pultrusions can then be joined together to form the spar caps and/or various other rotor blade components.
Thus, spar caps formed using pultrusions usually include pultrusion-formed layers bonded together via a resin material. More specifically, spar caps are generally formed of a plurality of stacked pultruded plates that are bonded together in a mold.
Though the benefits of using pultruded plates in spar caps have been realized, inherent properties of such plates or layers present design challenges. For example, using plate-shaped pultrusions to form curved-shaped components. More specifically, many pultrusions have a flat cross-section (e.g. are square or rectangular) as such shapes are easy to manufacture. Though the use of flat pultrusions can offer a significant improvement in cost and producibility of rotor blade components, such pultrusions do not typically lay into curved molds without gaps between the pultrusions and the mold shape. Since wind turbine blades are often curved from root to tip, challenges exist to form pultruded layers that curve with the blade shell. When plates containing different fibers are utilized in the same component, modulus mismatch can become problematic. For instance, substantial differences in the elastic modulus between plates can cause delamination to occur between the plates.
Conformance to the mold can be achieved to a certain degree by cutting the pultrusions into thinner strips; however, this increases the cost of the pultrusion process, machining time, and/or the difficulty of placing the pultrusions into the mold. In addition, the use of pultruded layers creates a concern for crack propagation. More specifically, cracks in a pultruded layer tend to migrate from end to end in a relatively short amount of time.
Accordingly, the art is continuously seeking new and improved methods of manufacturing rotor blade components, such as spar caps, using pultrusions. More specifically, methods of manufacturing rotor blade components using pultruded rods that provide more flexibility to the component such that the component can adhere to curved surfaces of the rotor blade would be advantageous. A crack in a rotor blade component utilizing pultruded rods tends to move in a zig-zag manner around the pultruded rods, which leads to a longer propagation life.
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 component for a wind turbine. The rotor blade component includes an enclosed primary outer casing and a plurality of pultruded rods. The enclosed primary outer casing defines a hollow interior. The plurality of pultruded rods is received within the hollow interior of the primary outer casing and secured therein via a first resin material. Further, an arrangement of the plurality of pultruded rods within the primary outer casing and a relationship of a maximum dimension of each of the plurality of pultruded rods and a maximum dimension of the enclosed primary outer casing are configured to maximize flexibility of the rotor blade component.
In one embodiment, the plurality of pultruded rods may include a first fiber volume fraction of from about 60% to about 80%. In another embodiment, primary outer casing, the plurality of pultruded rods, and the first resin material together may include a second fiber volume fraction of from about 50% to about 70%. In other embodiments, the maximum diameter of each of the plurality of pultruded rods corresponds to a diameter thereof. Further, the diameter of each of the plurality of pultruded rods may be less than about 10% of a maximum dimension of the enclosed outer casing. More specifically, in one embodiment, the diameter of each of the plurality of pultruded rods may range from about 0.5 millimeters (mm) to about 40 mm. In a further embodiment the enclosed primary outer casing may be constructed of a plurality of fibers joined together via a second resin material.
In additional embodiments, the primary outer casing may include a root end and a tip end, the enclosed primary outer casing being curved between said root end and said tip end. In one embodiment, a cross-sectional area of the primary outer casing may taper between the root end and the tip end. Still, in a further embodiment, the primary outer casing may define a wall thickness that varies between the root end to the tip end.
In further embodiments, a plurality of enclosed additional enclosed casings may be arranged within the primary outer casing. At least a portion of the plurality of rods is received within each of the enclosed additional enclosed casings. In another embodiment, the rotor blade component may include a filler material received and secured within the enclosed primary outer casing via the first resin material.
In yet another embodiment, the primary outer casing may include a plurality of cavities arranged in a side-by-side configuration in a chord-wise direction of the rotor blade. At least two of the plurality of cavities includes at least a portion of the plurality of pultruded rods and at least one of the plurality of cavities includes a filler material.
In a further embodiment, the rotor blade component may further include at least one pultruded plate. The pultruded plate may be joined with the exterior of the primary outer casing and secured there via a third resin material.
In another aspect, the present disclosure is directed to a rotor blade assembly for a wind turbine. The rotor blade assembly includes a rotor blade. The rotor blade includes a suction side, a pressure side, a leading edge, and a trailing edge extending between a blade root and a blade tip. The rotor blade assembly also includes at least one rotor blade component arranged within the rotor blade. The rotor blade component includes an enclosed primary outer casing extending in a span-wise direction of the rotor blade from the blade root towards the blade tip. The enclosed primary outer casing includes at least one cavity and a plurality of pultruded rods. The plurality of pultruded rods is received and secured within the at least one cavity via a first resin material. An arrangement of the plurality of pultruded rods within the primary outer casing and a relationship of a maximum dimension of each of the plurality of pultruded rods and a maximum dimension of the enclosed primary outer casing are configured to maximize flexibility of the rotor blade component.
In additional embodiments, the plurality of pultruded rods may include at least one of carbon or glass fibers. A ratio of pultruded rods formed from glass fibers to pultruded rods formed from carbon fibers may vary along the span-wise direction.
In a further embodiment, the rotor blade assembly may include a plurality of enclosed additional enclosed casings arranged within the primary outer casing. At least a portion of the plurality of rods is received within each of the enclosed additional enclosed casings. In another embodiment, the enclosed primary outer casing may include a plurality of cavities arranged in a side-by-side configuration in a chord-wise direction of the rotor blade.
In yet another aspect, the present disclosure is directed to a method of manufacturing a rotor blade component of a wind turbine. The method includes providing an enclosed outer casing. Another step includes arranging a plurality of pultruded rods within the enclosed outer casing in a plurality of rows and columns. An arrangement of the plurality of pultruded rods within the primary outer casing and a relationship of a maximum dimension of each of the plurality of pultruded rods and a maximum dimension of the enclosed primary outer casing are configured to maximize flexibility of the rotor blade component. Yet another step includes sealing the outer casing at opposing ends thereof. The method also includes infusing at least one resin material into the outer casing to secure the plurality of pultruded rods therein so as to form the rotor blade component.
In other embodiments, the rotor blade component may include at least one of a spar cap, a shear web, a root ring, or an edgewise stiffening reinforcement. Still in further embodiments, the enclosed primary outer casing may be formed via at least one of pultrusion, thermoforming, or infusion.
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.
Generally, the present subject matter is directed to improved pultruded rotor blade components for wind turbines and methods of manufacturing the same. For example, in one embodiment, the rotor blade components described herein may be formed using a plurality of pultruded rods arranged in an enclosed primary outer casing. The enclosed primary outer casing defines a hollow interior extending between a root end and an opposing tip end. Each of the plurality of pultruded rods is received within the enclosed primary outer casing and secured therein via a first resin material. As such, the outer casing acts as both the component mold and part of the finished part. Further, an arrangement of the plurality of pultruded rods within the enclosed primary outer casing and a maximum dimension of the pultruded rods are configured to maximize the flexibility of the rotor blade component.
As such, flexibility of the part can be adjusted by changing the number of pultruded rods, the cross-sectional area of the pultruded rods, the fiber volume fraction of the pultruded rods, and/or the ratio of the cross-sectional area of the pultruded rods to the hollow cross-sectional area of the enclosed primary outer casing.
The present disclosure provides many advantages not present in the prior art. For example, the use of pultruded materials in spar caps and other rotor blade components can reduce defects and increase the strength of the component. Further, rotor blade components of the present disclosure that are formed via pultruded rods are more flexible (as compared to pultruded plates) and therefore more capable of conforming to a curved cavity that can be better incorporated into a curved rotor blade mold. Moreover, rotor blade components of the present invention can have better crack propagation characteristics versus a pultruded plate. In addition, components utilizing rods containing different fibers can avoid the delamination issue possible with plates formed from different fibers. More specifically, the smaller shape and geometry of the rods can prevent extreme modulus jumps that can lead to delamination.
Referring now to the drawings,
Referring to
In several embodiments, the body shell 21 of the rotor blade 16 may be formed as a single, unitary component. Alternatively, the body shell 21 may be formed from a plurality of shell components. For example, the body shell 21 may be manufactured from a first shell half generally defining the pressure side 34 of the rotor blade 16 and a second shell half generally defining the suction side 36 of the rotor blade 16, with such shell halves being secured to one another at the leading and trailing ends 26, 28 of the blade 16. Additionally, the body shell 21 may generally be formed from any suitable material. For instance, in one embodiment, the body shell 21 may be formed entirely from a laminate composite material, such as a carbon fiber reinforced laminate composite or a glass fiber reinforced laminate composite. Alternatively, one or more portions of the body shell 21 may be configured as a layered construction and may include a core material, formed from a lightweight material such as wood (e.g., balsa), foam (e.g., extruded polystyrene foam) or a combination of such materials, disposed between layers of laminate composite material.
Referring particularly to
Referring now to
More specifically, as shown, the spar cap 20 is constructed of an enclosed primary outer casing 42 having a hollow interior 44 configured to receive a plurality of pultruded rods 40 therein. Further, as shown, the pultruded rods 40 are secured within the hollow interior 44 of the primary outer casing 42 via a first resin material 46. In addition, the primary outer casing 42 described herein may be constructed of a plurality of fibers joined together via a second resin material 47. Moreover, as shown particularly in
In some embodiments, the pultruded rods 40 may include a first fiber volume fraction of from about 60% to about 80%. More specifically, in certain embodiments, the first fiber volume fraction may be about 69%. In further embodiments, the combined enclosed primary outer casing 42, the plurality of pultruded rods 40, and the first resin material together may include a second fiber volume fraction of from about 50% to about 70%. More specifically, in certain embodiments, the second fiber volume fraction may be about 58%. As used herein, a fiber volume fraction is generally defined as the ratio of the volume of the fiber strands to the volume of both the fiber strands and resin as a percentage.
In other embodiments, the maximum diameter of each of the plurality of pultruded rods corresponds to a diameter thereof. Further, the diameter of each of the plurality of rods may be less than about 10% of a maximum dimension of the enclosed outer. A used herein, the maximum dimension of the enclosed outer casing is the maximum dimension in the chord-wise direction of the outer casing. In some embodiments, each of the plurality of pultruded rods may have a diameter ranging from about 0.5 mm to about 40 mm. As such, the diameter of each of the pultruded rods 40, which corresponds to the maximum dimension thereof, is configured to maximize the flexibility of the rotor blade component. For example, the diameter of the pultruded rods 40 is generally correlated with the fiber volume fraction of the rods 40. As such, pultruded rods 40 with larger diameters generally tend to have lower fiber volume fractions. In contrast, pultruded rods 40 with smaller diameters generally tend to have higher fiber volume fractions, which, in regard to flexibility, is favorable. Furthermore, in certain embodiments, pultruded rods 40 of varied diameters may be utilized in forming the rotor blade components described herein in order to achieve the desired fiber volume fraction.
Referring now generally to
In addition, as shown particularly in
It should be understood that the pultruded rods 40 described herein may be formed using any suitable pultrusion process. For example, the pultruded rods 40 are generally formed of reinforced materials (e.g. fibers or woven or braided strands) that are impregnated with a resin material and pulled through a stationary die such that the resin material cures or undergoes polymerization through added heat or other curing methods. For example, in certain embodiments, the heated die may include a mold cavity corresponding to the desired shape of pultruded rods 40 such that the mold cavity forms the desired shape in the completed part. Similarly, the enclosed primary outer casing 42 may be formed using any suitable process, including but not limited to pultrusion, thermoforming, or infusion.
As such, in various embodiments, the fibers may include but are not limited to glass fibers, nanofibers, carbon fibers, metal fibers, wood fibers, bamboo fibers, polymer fibers, ceramic fibers, or similar. In addition, the fiber material may include short fibers, long fibers, or continuous fibers.
Further, the resin materials described herein may include a thermoplastic material or a thermoset material. A thermoplastic material as described herein generally encompasses 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 solidify 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, a thermoset material as described herein generally encompasses 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, esters, epoxies, or any other suitable thermoset material.
Thus, in accordance with certain aspects of the present disclosure, the pultruded rods 40 can be then joined together within the outer casing 42 to form the spar cap 20. More specifically, the pultruded rods 40 may be joined and/or secured together via vacuum infusion, adhesive, semi-preg material, pre-preg material, or any other suitable joining method. In addition, as mentioned, the pultruded rods 40 are arranged in the outer casing 42 so as to maximize the flexibility of the spar cap 20.
In addition, it should be understood that the pultruded rods 40 may have any suitable cross-sectional shape. For example, as can be seen in
Referring particularly to
Referring now to
Further, as shown, the additional enclosed casings 142 are secured within the hollow interior 44 of the primary outer casing 42 using an additional resin material 146. Like the primary outer casing 42, the enclosed additional enclosed casings 142 may also be formed via pultrusion, thermoforming, and/or infusion. It should also be recognized that the enclosed primary outer casing 42, the enclosed additional enclosed casing 142, and/or the pultruded rods 40 of some embodiments are pre-cured, pre-fabricated components manufactured using any suitable methods known in the art.
Referring now to
In a further embodiment the filler material 52 may include a matrix of horizontal and/or vertical stiffening ribs configured to receive a portion of the pultruded rods in the each of the spaces between stiffening ribs. For example, the matrix of vertical and horizontal stiffening ribs may fill the hollow interior 44 with the first resin material 46 and the pultruded rods 40 filling the spaces between stiffening ribs.
Referring now to
As such, one or more of the cavities 54 may be filled with the pultruded rods 40. For example, as shown particularly in
Referring now to
The present disclosure is also directed to methods for manufacturing rotor blade components as described herein. For example, as shown in
It should also be understood that the plurality of pultruded rods 40, the primary outer casing 42, and the additional casings 142 as described herein may be used to construct various other rotor blade components, in addition to spar caps. For example, in certain embodiments, the components and methods described herein may be used to construct the shear web 24, a root ring, an edgewise stiffening reinforcement, or any other rotor blade component that can benefit from being constructed of pultruded parts as described herein.
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.
