Patent Application
20170058866
The present disclosure relates generally to wind turbine rotor blades, and more particularly to thermoplastic pultruded stiffeners for locally reinforcing a wind turbine 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, 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 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 are typically constructed of glass fiber laminate composites and/or carbon fiber laminate composites. The shell of the rotor blade is generally built around the spar caps of the blade by stacking layers of fiber fabrics in a shell mold. The layers are then typically infused together, e.g. with a thermoset resin.
In some instances, additional structural support may be required for the rotor blade. Such support may be provided in the form of ribs, frames, and/or stringers that are typically constructed of thermoset resin composites. Thus, such structural components must be either co-infused into the blade shell during the infusion process or bonded to the blade shell post infusion. Either method, however, can be tedious and potentially expensive given the required surface treatment to effectively bond the components together.
Thus, the present disclosure is directed to thermoplastic pultruded structural components for a wind turbine rotor blade that are configured to locally reinforce the blade that address 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 having improved stiffness. The rotor blade includes a main blade structure, at least one blade segment configured with the main blade structure and defining an internal cavity of the rotor blade, at least one spar cap secured to an internal surface of the at least one blade segment, and at least one pultruded stiffener configured within the internal cavity of the at least one blade segment so as to provide additional stiffness to the rotor blade. In addition, the pultruded stiffener is constructed, at least in part, from a thermoplastic resin system.
In one embodiment, the blade segment(s) may also be constructed, at least in part, from a thermoplastic resin system. In such embodiments, the pultruded stiffener(s) may be easily welded to thermoplastic blade segment(s). In further embodiments, the thermoplastic resin system may also include at least one fiber reinforcement material, including but not limited to glass fibers, carbon fibers, polymer fibers, ceramic fibers, nanofibers, or metal fibers.
In another embodiment, the pultruded stiffener(s) may be secured to the internal surface of the blade segment(s), e.g. via welding. Alternatively, the pultruded stiffener(s) may be secured to the at least one spar cap, e.g. via welding. In additional embodiments, the rotor blade may include opposing spar caps configured on opposing internal surfaces of the blade segment(s) and one or more shear webs configured between the opposing spar caps. In such embodiments, the pultruded stiffener(s) may be secured to at least one of the opposing spar caps and/or the shear web.
In certain embodiments, the pultruded stiffener(s) may include a base portion and a stiffening portion. In such embodiments, the base portion may be welded to the internal surface of the blade segment(s). In addition, the stiffening portion may extend from the base portion within an internal cavity of the rotor blade so as to resist a load through a thickness of the at least one blade segment. For example, in certain embodiments, the load may include a buckling load, a flap-wise deflection, an edge-wise deflection, or similar.
In additional embodiments, the pultruded stiffener may extend in a generally span-wise direction within the internal cavity of the rotor blade when secured to an internal surface thereof. Further, in particular embodiments, the pultruded stiffener(s) may define a cross-section having one of the following shapes: triangle, rectangle, square, T-shaped, L-shaped, U-shaped, J-shaped, C-shaped, Z-shaped, V-shaped, or similar. Thus, the shape of the cross-section effectively locally reinforces the rotor blade, i.e. at the location of the stiffener.
In another aspect, the present disclosure is directed to a rotor blade for a wind turbine having improved stiffness. The rotor blade includes a blade root section, a blade tip section, a plurality of blade segments arranged between the blade root section and the blade tip section, opposing spar caps configured on opposing internal surfaces of the plurality of blade segments and extending in a generally span-wise direction, one or more shear webs configured between the opposing spar caps, and at least one pultruded stiffener. Further, each of the blade segments defines an internal cavity of the rotor blade and includes a thickness defined by an internal surface and an external surface thereof. Thus, the pultruded stiffener(s) are configured within the internal cavity of the rotor blade and are constructed, at least in part, from a thermoplastic resin system. As such, the pultruded stiffener can be easily welded to thermoplastic blade segments.
In yet another aspect, the present disclosure is directed to a method of improving stiffness of a rotor blade. The method includes providing a rotor blade having a main blade structure and at least one blade segment, the blade segment defining an internal cavity. The method also includes locally reinforcing one or more locations on the internal surface of the blade segment with one or more pultruded stiffeners. Further, the pultruded stiffener is constructed, at least in part, from a thermoplastic resin system. As such, the pultruded stiffener can be easily welded to thermoplastic blade segments.
In one embodiment, the method may also include securing opposing spar caps on opposing internal surfaces of the blade segment(s) and securing one or more shear webs between the opposing spar caps. Thus, the location(s) of local reinforcement may include at least one of an internal surface of the at least one blade segment, at least one of the opposing spar caps, the one or more shear webs, and/or any other suitable location within the internal cavity of the blade segment(s).
In further embodiments, the method may include forming the blade segment(s), at least in part, from a thermoplastic resin system and at least one fiber reinforcement material. In such embodiments, the pultruded stiffener(s) may be easily welded to the blade segment(s). More specifically, in additional embodiments, the step of locally reinforcing one or more locations on the internal surface of the blade segment with one or more pultruded stiffeners may include welding one or more pultruded stiffeners to the internal surface of the blade segment.
For example, in certain embodiments, the step of welding one or more pultruded stiffeners to the internal surface of the blade segment may include welding a base portion of the pultruded stiffener to the internal surface of the blade segment such that a stiffening portion of the pultruded stiffener extends from the base portion within an internal cavity of the rotor blade so as to resist a load acting through a thickness of the at least one blade segment. In addition, in another embodiment, the step of welding one or more pultruded stiffeners to the internal surface of the blade segment may include welding one or more of the pultruded stiffeners to the internal surface of the blade segment such that the stiffener extends in a generally span-wise direction within the internal cavity of the rotor blade.
In further embodiments, the method may also include forming the pultruded stiffener so as to define a cross-section comprising one of the following shapes: triangle, rectangle, square, T-shaped, L-shaped, U-shaped, J-shaped, C-shaped, Z-shaped, V-shaped, or similar.
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 disclosure is directed to a rotor blade for a wind turbine having improved stiffness. The rotor blade typically includes a blade root section, a blade tip section, and a plurality of thermoplastic blade segments arranged between the blade root section and the blade tip section. Thus, the blade segments define the outer surface of the rotor blade and an internal cavity therein. Further, the rotor blade may also include opposing spar caps secured to an internal surface of the blade segments and a shear web configure between the opposing spar caps. In addition, the rotor blade includes one or more pultruded stiffener configured within the internal cavity of the blade segments. Further, the pultruded stiffener is constructed, at least in part, from a thermoplastic resin system.
Thus, the present disclosure provides many advantages not present in the prior art. For example, in one embodiment, the present disclosure provides a rotor blade having thermoplastic blade segments and one or more thermoplastic pultruded stiffeners that can be easily welded to the internal surface of the blade segments. Accordingly, the rotor blades as described herein have improved stiffness and may reduce costs, labor time, and/or assembly cycle time of conventional rotor blade production. Further, the reinforced rotor blades of the present disclosure can have a reduced weight by eliminating many of the complex joints of conventional blades.
Referring now to the drawings,
Referring now to
More specifically, as shown, the main blade structure 15 may include any one of or a combination of the following: a pre-formed blade root section 20, a pre-formed blade tip section 22, one or more one or more continuous spar caps 48, 50, 51, 53, one or more shear webs 35 (
More specifically, in certain embodiments, as shown in
In addition, the spar caps 48, 50, 51, 53 may be constructed of any suitable materials, e.g. a thermoplastic material, a thermoset material or combinations thereof. For example, in certain embodiments, one or more of the spar caps 48, 50, 51, 53 may be constructed of a low-cost resin material, e.g. a thermoset polymer, reinforced with one or more fiber materials. In such an embodiment, a thermoplastic resin (also optionally reinforced with a fiber material) may be infused around at least a portion of the already-cured thermoset spar caps. Thus, the thermoplastic resin system is configured to coat the spar cap so as to allow subsequent welding procedures to take place during assembly of the rotor blade 16 (e.g. to allow the thermoplastic blade segments 21 to be welded to one or more of the spar caps 48, 50, 51, 53). Further, the thermoplastic resin may encapsulate the entire spar cap or only certain regions of the spar cap to allow subsequent welding with other blade components. Moreover, such regions may be broken up by span or chord-wise directions and do not necessarily have to be continuous. In still additional embodiments, the spar caps 48, 50, 51, 53 may be constructed entirely of a thermoplastic material or entirely of a thermoset material. Further, in certain embodiments, the spar caps 48, 50, 51, 53 may be pultruded from thermoplastic or thermoset materials, which is discussed in more detail below.
Further, as shown in
In still additional embodiments, as shown in
Referring particularly to
In addition, the blade segments 21 may be constructed of any suitable resin system, including but not limited to a thermoset material or a thermoplastic material, an optional fiber reinforcement material, and/or one or more additives. More specifically, as generally shown in the figures, the blade segments 21 may include any one of or combination of the following blade segments: pressure and/or suction side segments 44, 46, (
For example, as shown in
As shown in
Moreover, as shown in
The thermoplastic materials as described herein 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 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.
Referring now to
As used herein, the term “pultruded” or similar generally encompasses reinforced materials (e.g. fibers or woven or braided strands) that are impregnated with a resin (e.g. a thermoplastic polymer) and pulled through a stationary die such that the resin cures or undergoes polymerization. As such, the process of manufacturing pultruded components (e.g. such as the pultruded stiffeners 60) is typically characterized by a continuous process of composite materials that produces composite parts having a constant cross-section. In addition, the pultruded components may be produced from rovings, which generally encompass long and narrow bundles of fibers that are not combined until joined by a cured resin.
Thus, the pultruded stiffeners 60 as described herein may be constructed, at least in part, from a thermoplastic resin system. A thermoplastic resin system generally encompasses a thermoplastic material, optionally one or more fiber reinforcement materials, and/or one or more additives as necessary. In certain embodiments, the fiber reinforcement material may include glass fibers, carbon fibers, polymer fibers, ceramic fibers, nanofibers, metal fibers, or similar. Thus, in such embodiments, the pultruded stiffener(s) 60 may be easily welded to the thermoplastic blade segment(s) 21 and/or various other components within the internal cavity 56 of the rotor blade 16. In addition, the pultruded stiffener 60 may generally extend in a generally span-wise direction within the internal cavity 56 of the rotor blade 16 when secured therein.
For example, as shown in
Further, as shown particularly in
Further, the loads as described herein may include a buckling load, a flap-wise deflection, an edge-wise deflection, or any other similar load acting on the rotor blade 16. More specifically, the stiffening portion 64, which generally defines the shape of the stiffener 60, typically generates the stiffness for a buckling load through the blade skin, as well as, most of the stiffness to resist flap-wise deflection of the blade 16. Thus, the shape of the pultruded stiffener 60 may be chosen based on the moment of inertia of the shape and/or the direction of the load being resisted. More specifically, the shape of the stiffening portion 64 may include a shape that extends generally perpendicular to the internal surfaces 27, 29. Alternatively, the shape of the stiffening portion 64 may be angled relative to the internal surfaces 27, 29, e.g. at a 45-degree angle. In addition, the shape of the stiffening portion 64 may be curved. Accordingly, the pultruded stiffener(s) 60 may define any suitable cross-sectional shape, including but not limited to the following: a triangle, a rectangle, a square, T-shaped, L-shaped, U-shaped, J-shaped, C-shaped, Z-shaped, V-shaped, or similar. Thus, the cross-sectional shape of the pultruded stiffener(s) 60 may include an open cross-section or a closed cross-section. Further, in certain embodiments, the cross-sectional shape may include a solid cross-section (
Referring now to
As shown at 104, the method 100 also includes locally reinforcing one or more locations on one or more of the internal surfaces 27, 29 of the blade segment(s) 21 with one or more pultruded stiffeners 60. In certain embodiments, for example, the location(s) may include one or more of the internal surfaces 27, 29 of the blade segment(s) 21, one or more of the opposing spar caps 48, 50, and/or the shear web(s) 35. Thus, in certain embodiments, the pultruded stiffener(s) 60 may be easily welded to the thermoplastic blade segment(s) 21. More specifically, in additional embodiments, the step of locally reinforcing one or more additional locations on one or more of the internal surfaces 27, 29 of the blade segment(s) 21 with one or more pultruded stiffeners 60 may include welding one or more pultruded stiffeners to one or more of the internal surfaces 27, 29 of the blade segment 21.
For example, in certain embodiments, the step of welding one or more pultruded stiffeners 60 on one or more of the internal surfaces 27, 29 of the blade segment(s) 21 may include welding a base portion 62 of the pultruded stiffener 60 to the internal surface of the blade segment 21 such that a stiffening portion 64 of the pultruded stiffener 60 extends from the base portion 62 within an internal cavity 56 of the rotor blade 16 so as to resist a load through a thickness of the at least one blade segment 21. In addition, in another embodiment, the step of welding one or more pultruded stiffeners 60 to one or more of the internal surfaces 27, 29 of the blade segment(s) 21 may include welding one or more of the pultruded stiffeners 60 to one or more of the internal surfaces 27, 29 of the blade segment(s) 21 such that the stiffener 60 extends in a generally span-wise direction within the internal cavity 56 of the rotor blade.
In further embodiments, the method 100 may also include forming the pultruded stiffener(s) 60 so as to define a cross-section having one of the following shapes: triangle, rectangle, square, T-shaped, L-shaped, U-shaped, J-shaped, C-shaped, Z-shaped, V-shaped, or similar.
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.
