Patent Application
20240293992
The present disclosure relates in general to wind turbine rotor blades, and more particularly to methods of manufacturing shells having stiffening grid structures, for example, for wind turbine rotor blades.
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 one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil 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 exterior 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 are typically constructed of various materials, including but not limited to 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. Accordingly, conventional rotor blades generally have a sandwich panel configuration. As such, conventional blade manufacturing of large rotor blades involves high labor costs, slow through put, and low utilization of expensive mold tooling. Further, the blade molds can be expensive to customize.
Thus, methods for manufacturing rotor blades may include forming the rotor blades in segments. The blade segments may then be assembled to form the rotor blade. For example, some modern rotor blades, such as those blades described in U.S. patent application Ser. No. 14/753,137 filed Jun. 29, 2015 and entitled “Modular Wind Turbine Rotor Blades and Methods of Assembling Same,” which is incorporated herein by reference in its entirety, have a modular panel configuration. Thus, the various blade components of the modular blade can be constructed of varying materials based on the function and/or location of the blade component.
In view of the foregoing, the art is continually seeking improved methods for manufacturing shells having stiffening grid structures, for example, for wind turbine rotor blades.
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 method for manufacturing a shell, such as a shell of a rotor blade. The method includes providing a mold of the shell. The method also includes forming one or more first skins on the mold. Further, the method includes securing at least one three-dimensional (3-D) grid structure onto an inner surface of the one or more first skins. Further, the method includes securing one or more reinforcing members to one or more locations of the grid structure so as to locally increase a stiffness of the shell at the one or more locations by creating one or more localized sandwich structures with the grid structure.
In an embodiment, securing the 3-D grid structure onto the inner surface of the first skin(s) may include placing the mold of the shell relative to a computer numeric control (CNC) device and printing and depositing, via the CNC device, a plurality of rib members that form the grid structure onto the inner surface of the first skin(s) before the one or more first skins have cooled from forming. As such, the grid structure bonds to the first skin(s) as the grid structure is being deposited.
In another embodiment, the location(s) of the reinforcing members may correspond to a center location of the shell, a trailing edge of the shell, and/or one or more locations having a load above a predetermined threshold. In further embodiments, determining the location(s) having the load above the predetermined threshold may include performing, for example, a computer-implemented structural analysis on the shell.
In several embodiments, securing the 3-D grid structure(s) onto the inner surface of the first skin(s) may include forming the grid structure of a core material and securing the grid structure to the inner surface of the first skin(s).
In particular embodiments, securing the one or more reinforcing members to one or more locations of the grid structure may include securing the one or more reinforcing members to a core material and securing at least a portion of the reinforcing member(s) and/or the core material to the inner surface of the first skin(s).
In further embodiments, the method may include securing the reinforcing member(s) to the location(s) of the grid structure via at least one of adhesive bonding, thermoplastic welding, ultrasonic welding, tack welding, laser welding, chemical welding, hot plate welding, and/or combinations thereof. In additional embodiments, the reinforcing member(s) may be constructed of at least one of laminate, polymer, metal, wood, fibers, and/or combinations thereof.
In another embodiment, the method may include bonding one or more second skins to at least one of the one or more reinforcing members of the one or more first skins. In such embodiments, the method may also include securing at least a portion of the grid structure to at least one of the one or more first skins or the one or more second skins.
In another aspect, the present disclosure is directed to a shell. The shell includes one or more fiber-reinforced first skins and at least one shell reinforcement assembly secured to the fiber-reinforced first skin(s). The shell reinforcement assembly includes at least one three-dimensional (3-D) grid structure and one or more reinforcing members secured to one or more locations of the grid structure so as to locally increase a stiffness of the shell at the one or more locations by creating one or more localized sandwich structures with the grid structure. It should be understood that the shell may further include any of the additional features described herein.
In yet another aspect, the present disclosure is directed to a method for manufacturing a shell. The method includes forming one or more fiber-reinforced first and second skins, such as via vacuum forming or additive manufacturing. The method also includes providing and heating a mold. Further, the method includes placing one or more reinforcing members on the heated mold. Moreover, the method includes printing and depositing, via the CNC device, a plurality of rib members that form the grid structure onto an inner surface of the one or more reinforcing members while the one or more reinforcing members are heated. As such, the grid structure bonds to the reinforcing member(s) as the grid structure is being deposited so as to form a shell reinforcement assembly. In addition, the method includes securing the shell reinforcement assembly between the one or more fiber-reinforced first and second skins. It should be understood that the method may further include any of the additional steps and/or features 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.
Generally, the present disclosure is directed to methods for manufacturing grid structures for shells, such as wind turbine rotor blade shells using automated deposition of materials via technologies such as 3-D Printing, additive manufacturing, automated fiber deposition, as well as other techniques that utilize CNC control and multiple degrees of freedom to deposit material. In addition, the grid structures can be further reinforced with additional reinforcing members secured thereto, which provide additional structural stiffness at certain locations. As such, the grid structures of the present disclosure are useful for reinforcing such shells. The grid shape can also be optimized for maximum buckling load factor versus weight and print speed. Further, additive manufacturing allows for more customized reinforcement compared to conventional sandwich panels.
Thus, the methods described herein provide many advantages not present in the prior art. For example, the methods of the present disclosure provide the ability to easily customize shells having various curvatures, aerodynamic characteristics, strengths, stiffness, etc. As such, where the shells are used in rotor blade shells, the grid structures of the present disclosure can be designed to match the stiffness and/or buckling resistance of existing sandwich panels for rotor blades. More specifically, in certain embodiments, the shells of the present disclosure can be more easily customized based on the local buckling resistance needed. Still further advantages include the ability to locally and temporarily buckle to reduce loads and/or tune the resonant frequency of the rotor blade shells to avoid problem frequencies. Moreover, the grid structures described herein can be manufactured with less fiber reinforcement as the fiber may no longer necessary due to the additional laminate material.
Referring now to the drawings,
Referring now to
The thermoplastic rotor blade components and/or 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 components and/or 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.
In addition, as mentioned, the thermoplastic and/or the thermoset material as described herein may optionally be reinforced with a fiber material, including but not limited to glass fibers, carbon fibers, polymer fibers, wood fibers, bamboo fibers, ceramic fibers, nanofibers, metal fibers, or similar or combinations thereof. In addition, the direction of the fibers may include multi-axial, unidirectional, biaxial, triaxial, or any other another suitable direction and/or combinations thereof. Further, the fiber content may vary depending on the stiffness required in the corresponding blade component, the region or location of the blade component in the rotor blade 16, and/or the desired weldability of the component.
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 (
Referring particularly to
More specifically, as shown in
In specific embodiments, as shown in
Similarly, the blade tip section 22 may include one or more longitudinally extending spar caps 51, 53 infused therewith. More specifically, as shown, the spar caps 48, 50, 51, 53 may be configured to be engaged against opposing inner surfaces of the blade segments 21 of the rotor blade 16. Further, the blade root spar caps 48, 50 may be configured to align with the blade tip spar caps 51, 53. Thus, the spar caps 48, 50, 51, 53 may generally be designed to control the bending stresses and/or other loads acting on the rotor blade 16 in a generally span-wise direction (a direction parallel to the span 23 of the rotor blade 16) during operation of a wind turbine 10. In addition, the spar caps 48, 50, 51, 53 may be designed to withstand the span-wise compression occurring during operation of the wind turbine 10. Further, the spar cap(s) 48, 50, 51, 53 may be configured to extend from the blade root section 20 to the blade tip section 22 or a portion thereof. Thus, in certain embodiments, the blade root section 20 and the blade tip section 22 may be joined together via their respective spar caps 48, 50, 51, 53.
In addition, the spar caps 48, 50, 51, 53 may be constructed of any suitable materials, e.g. a thermoplastic or thermoset material or combinations thereof. Further, the spar caps 48, 50, 51, 53 may be pultruded from thermoplastic or thermoset resins. As used herein, the terms “pultruded,” “pultrusions,” 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. As such, the process of manufacturing pultruded members is typically characterized by a continuous process of composite materials that produces composite parts having a constant cross-section. Thus, the pre-cured composite materials may include pultrusions constructed of reinforced thermoset or thermoplastic materials. Further, the spar caps 48, 50, 51, 53 may be formed of the same pre-cured composites or different pre-cured composites. 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.
Referring to
In addition, as shown in
Referring now to
As shown at (102), the method 100 includes providing a mold 58 of the shell 21. As shown at (104), the method 100 includes forming one or more first skins 56 on the mold 58. In an embodiment, it should be understood that the first skins 56 may be curved. In such embodiments, the method 100 may include forming the curvature of the first skins 56. Such forming may include providing one or more generally flat fiber-reinforced outer skins, forcing the first skins 56 into a desired shape corresponding to a desired contour, and maintaining the first skins 56 in the desired shape during printing and depositing. As such, the first skins 56 generally retain their desired shape when the first skins 56 and the grid structure 62 secured thereto (described below) are released.
As shown in
Referring back to
It should be understood that the grid structure 62 can be formed to have any suitable shape and/or configuration. For example, in another embodiment, as shown in
As such, depending on the desired stiffness of the grid structure 62 and/or the location therefore, the method 100 may include forming the grid structure(s) 62 using various manufacturing methods. For example, in one embodiment, the method 100 may include forming the grid structure(s) 62 via additive manufacturing, such as 3-D printing. 3-D printing, as used herein, is generally understood to encompass processes used to synthesize three-dimensional objects in which successive layers of material are formed under computer control to create the objects. As such, objects of almost any size and/or shape can be produced from digital model data. It should further be understood that the methods of the present disclosure are not limited to 3-D printing, but rather, may also encompass more than three degrees of freedom such that the printing techniques are not limited to printing stacked two-dimensional layers, but are also capable of printing curved shapes.
More specifically, in such embodiments, as shown in
For example, in one embodiment, the CNC device 60 is configured to print and deposit the rib members 64 onto the inner surface of the one or more fiber-reinforced first skin(s) 56 after the formed skin(s) 56 reach a desired state that enables bonding of the printed rib members 64 thereto, i.e. based on one or more parameters of temperature, time, and/or hardness. Therefore, in certain embodiments, wherein the skin(s) 56 and the grid structure 62 are formed of a thermoplastic matrix, the CNC device 60 may immediately print the rib members 64 thereto as the forming temperature of the skin(s) 56 and the desired printing temperature to enable thermoplastic welding/bonding can be the same).
More specifically, in particular embodiments, before the skin(s) 56 have cooled from forming, (i.e. while the skins are still hot or warm), the CNC device 60 is configured to print and deposit the rib members 64 onto the inner surface of the one or more fiber-reinforced first skins 56. For example, in one embodiment, the CNC device 60 is configured to print and deposit the rib members 64 onto the inner surface of the first skins 56 before the skins 56 have completely cooled. In addition, in another embodiment, the CNC device 60 is configured to print and deposit the rib members 64 onto the inner surface of the first skin(s) 56 when the skins 56 have partially cooled. Thus, suitable materials for the grid structure 62 and the first skins 56 can be chosen such that the grid structure 62 bonds to the first skins 56 during deposition. Accordingly, the grid structure 62 described herein may be printed using the same materials or different materials.
For example, in one embodiment, a thermoset material may be infused into the fiber material on the mold 58 to form the first skins 56 using vacuum infusion. As such, the vacuum bag is removed after curing and the one or more thermoset grid structures 62 can then be printed onto the inner surface of the skins 56. Alternatively, the vacuum bag may be left in place after curing. In such embodiments, the vacuum bag material can be chosen such that the material would not easily release from the cured thermoset fiber material. Such materials, for example, may include a thermoplastic material such as polymethyl methacrylate (PMMA) or polycarbonate film. Thus, the thermoplastic film that is left in place allows for bonding of thermoplastic grid structures 62 to the thermoset skins with the film in between.
In still further embodiments, the first skin(s) 56 may be formed of a reinforced thermoplastic resin with the grid structure 62 being formed of a thermoset-based resin with optional fiber reinforcement. In such embodiments, depending on the thermoset chemistry involved-the grid structure 62 may be printed to the first skin(s) 56 while the skins 56 are still hot, warm, partially cooled, or completely cooled.
In addition, the methods of the present disclosure may include treating the first skin(s) 56 to promote bonding between the first skin(s) 56 and the grid structure 62. More specifically, in certain embodiments, the first skin(s) 56 may be treated using flame treating, plasma treating, chemical treating, chemical etching, mechanical abrading, embossing, elevating a temperature of at least areas to be printed on the first skin(s) 56, and/or any other suitable treatment method to promote said bonding. In additional embodiments, the method may include forming the first skin(s) 56 with more (or even less) matrix resin material on the inside surface to promote said bonding. In additional embodiments, the method may include varying the outer skin thickness and/or fiber content, as well as the fiber orientation.
Accordingly, the method 100 of the present disclosure can also include varying the design of the grid structure 62 (e.g. materials, width, height, thickness, shapes, etc., or combinations thereof) to match a desired stiffness of the shell. As such, the grid structure 62 may define any suitable shape so as to form any suitable reinforcement component for the shell 21. For example, as shown in
In several embodiments, the cycle time of printing the grid structure 62 can also be reduced by using a rib pattern that minimizes the amount of directional change. For example, 45-degree angled grids can likely be printed faster than 90-degree grids relative to the chord direction of the proposed printer, for example. As such, the present disclosure minimizes printer acceleration and deceleration where possible while still printing quality grid structures 62.
In alternative embodiments, rather than printing the grid structure 62, the grid structure 62 may be formed of a prefabricated core material having the honeycomb configuration (or similar) described herein with respect to
Referring back to
For example, as shown in
As such, the reinforcing members 74 may be efficiently placed at any suitable location that may otherwise be difficult to provide additional reinforcement to the grid structure 62. For example, in some areas of the rotor blade (such as near the trailing edge), the grid structure 62 cannot be made taller because of space limitations. Thus, the reinforcing member(s) 74 can be placed in the grid structure 62 at such locations to improve stiffness without requiring a taller grid structure. Such reinforcing member(s) 74 can generally be more weight and/or cost efficient than without. This can be especially true in areas of the rotor blade that have higher loading as very tall grid structures will be less weight efficient versus adding the reinforcing members to particular locations of the grid structure 62.
In addition, as shown particularly in
In additional embodiments, the method 100 may include securing the reinforcing member(s) 74 to various location(s) of the grid structure 62 via adhesive bonding (as mentioned), thermoplastic welding, ultrasonic welding, tack welding, laser welding, chemical welding, hot plate welding, and/or combinations thereof.
In further embodiments, the method 100 may also include securing one or more second skins 57 to the reinforcing member(s) 74 so as to form the rotor blade shell 21. It should be understood that the one or more second skins 57 can be configured and formed similar or identical to the one or more first skins 56 described herein. Further,
In further embodiments, the method 100 may include securing at least a portion of the grid structure(s) 62 to the first skin(s) 56 and/or the second skin(s) 57. In particular embodiments, the method 100 may include printing the grid structure 62 such that a first side of the grid structure 62 bonds directly to the first skin(s) 56. In such embodiments, the method 100 may also include bonding a second side of the grid structure 62 to the second skin(s) 57 via an adhesive.
Referring now to
As shown at (202), the method 200 includes forming one or more first 56, such as via vacuum forming or additive manufacturing. As shown at (204), the method 200 includes providing a mold 58. In one embodiment, for example, the mold 58 could be a linear flat mold, as shown in
Referring back to
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/US2019/056188 | 10/15/2019 | WO |
