Patent Application
20070251090
This invention relates generally to blades that may be useful as wind turbine rotor blades, and more specifically to methods and apparatus for fabricating to blades.
Generally, a wind turbine includes a rotor having multiple blades. The rotor is mounted on a housing or nacelle, which is positioned on top of a truss or tubular tower. Utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 30 or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators, generally but not always rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is fed into a utility grid. Gearless direct drive turbines also exist.
At least some known wind turbine rotor blades are fabricated by laminating a stack of layers together, for example layers of fiber, metal, plastic, and/or wood, to form a composite shell having a predetermined aerodynamic shape. The laminated rotor blade shell may also include other components laminated with the layers of fiber, metal, plastic, and/or wood. For example, core material may be sandwiched between two adjacent layers in the stack to strengthen the rotor blade against, for example, buckling from wind loads. Moreover, and for example, portions of the laminated rotor blade shell adjacent internal supporting spars may include one or more supporting layers of fabric, metal, plastic, and/or wood, sometimes referred to as spar caps, to strengthen the portions for connection thereof to the internal spars. Furthermore, and for example, portions of the laminated rotor blade shell adjacent a root section of the rotor blade may include one or more supporting layers of fabric, plastic, metal, and/or wood for strengthening the root section to reduce or eliminate damage thereto from shear forces and/or rotor torque.
At least some known laminated rotor blade shells are fabricated by laminating a stack of the fabric, metal, plastic, and/or wood layers, and any other component layers, together with a resin. For example, the layers may be stacked in a mold having the predetermined aerodynamic shape. Alternatively, and for example, the layers may be wound around a mandrel having the predetermined aerodynamic shape to create the stack. The resin may be infused into the layers, for example using a vacuum bag system, which may also facilitate forming the layers to the mold shape. Alternatively, the layers may each be impregnated and/or coated with resin prior to stacking in the mold or winding around the mandrel. However, it may be difficult and/or time-consuming to form some components of rotor blade shells, for example spar caps, core material, and/or root section supports, such that they will both sufficiently support the rotor blade shell and be formed into the predetermined aerodynamic shape, for example because of a size of the layers, local variations in resin content, local variations in a curvature of the layers, and/or local variations in strains exerted on the shell during fabrication thereof.
In one aspect, a method is provided for fabricating a blade using a mold having a shape corresponding to a predetermined finished shape of at least a portion of the blade. The method includes stacking a plurality of layers of a material in the mold, stacking at least one component with the stack of the plurality of layers, wherein the component is a composite comprising a cured resin and at least one layer of fiber, and laminating the stack of the plurality of layers and the component.
In another aspect, a method is provided for fabricating a blade using a mold having a shape corresponding to a predetermined finished shape of at least a portion of the blade. The method includes stacking a plurality of layers of a material in the mold, stacking at least one component with the stack of the plurality of layers, wherein the component comprises a shape that corresponds to the predetermined finished shape of at least a portion of the blade, and laminating the stack of the plurality of layers and the component.
In another aspect, a method is provided for fabricating a blade using a filament winding process. The method includes providing a mandrel having a shape corresponding to a predetermined finished shape of at least a portion of the blade, winding fiber around the mandrel to form a plurality of layers of the fiber, positioning at least one component adjacent at least one layer of the plurality of layers of fiber, wherein the component comprises at least one of a shape that corresponds to the predetermined finished shape of at least a portion of the blade and at least one layer of fiber infused with a cured resin, and laminating the plurality of fiber layers and the component.
As used herein, the term “blade” is intended to be representative of any device that provides reactive force when in motion relative to a surrounding fluid. As used herein, the term “wind turbine” is intended to be representative of any device that generates rotational energy from wind energy, and more specifically, converts kinetic energy of wind into mechanical energy. As used herein, the term “wind generator” is intended to be representative of any wind turbine that generates electrical power from rotational energy generated from wind energy, and more specifically, converts mechanical energy converted from kinetic energy of wind to electrical power. As used herein, the term “windmill” is intended to be representative of any wind turbine that uses rotational energy generated from wind energy, and more specifically mechanical energy converted from kinetic energy of wind, for a predetermined purpose other than generating electrical power, such as, but not limited to, pumping a fluid and/or grinding a substance.
In some embodiments, wind generator 12 is mounted on a tower 14, however, in some embodiments wind turbine 10 includes, in addition or alternative to tower-mounted wind generator 12, a wind generator (and/or other type of wind turbine) adjacent the ground and/or a surface of water. The height of tower 14 may be selected based upon factors and conditions known in the art. Wind generator 12 includes a body 16, sometimes referred to as a “nacelle”, and a rotor (generally designated by 18) coupled to body 16 for rotation with respect to body 16 about an axis of rotation 20. Rotor 18 includes a hub 22 and a plurality of blades 24 (sometimes referred to as “airfoils”) extending radially outwardly from hub 22 for converting wind energy into rotational energy. Each blade 24 extends between a root section 26 coupled to rotor hub 22 and a tip section 28. Although rotor 18 is described and illustrated herein as having three blades 24, rotor 18 may have any number of blades 24. Blades 24 may each have any length and/or width (whether described herein). For example, in some embodiments one or more rotor blades 24 are about 0.5 meters long, while in some embodiments one or more rotor blades 24 are about 50 meters long. Other examples of blade 24 lengths include 10 meters or less, about 20 meters, about 34 meters, about 37 meters, and about 40 meters. Examples of blade widths include between about 0.5 meters and about 10 meters.
Despite how rotor blades 24 are illustrated in
Wind generator 12 includes an electrical generator (not shown) coupled to rotor 18 for generating electrical power from the rotational energy generated by rotor 18. The electrical generator 26 may be any suitable type of electrical generator, such as, but not limited to, a wound rotor induction generator. General operation of the electrical generator to generate electrical power from the rotational energy of rotor 18 is known in the art and therefore will not be described in more detail herein. In some embodiments, wind turbine 10 may include one or more control systems (not shown), actuating mechanisms, and/or sensors (not shown) coupled to some or all of the components of wind generator 12 for generally controlling operation of wind generator 12 and/or as some or all of the components thereof (whether such components are described and/or illustrated herein). For example, control system(s), actuating mechanism(s), and/or sensor(s) may be used for, but are not limited to, overall system monitoring and control including, for example, pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application, and/or fault monitoring. Alternative distributed or centralized control architectures may be used in some embodiments. General operation of wind turbine 10, and more specifically wind generator 12, is known in the art and therefore will not be described in more detail herein.
To support and/or strengthen shell 30, blade 24 may include one or more internal structural members 36, sometimes referred to as spars. Although structural member(s) 36 may have any suitable location, orientation, structure, configuration, and/or arrangement that enables member(s) 36 to function as described herein, exemplary structural member 36 of exemplary blade 24 is a box-spar that includes two spar caps 38 and 40 (which may sometimes be considered as components of shell 30) that each extend between two shear webs 42 and 44 that support and/or strengthen shell 30. Spar caps 38 and 40 generally support and/or strengthen shell 30 adjacent shear webs 42 and 44 to, for example, facilitate reducing or eliminating damage to blade shell 30 adjacent where webs 42 and 44 connect thereto. Each spar cap 38 and 40 may include one or more layers (not shown), each of any suitable material(s) that enable spar caps 38 and 40 to function as described herein, such as, but not limited to, metal, plastic, wood, and/or fiber, such as, but not limited to, glass fiber, carbon fiber, and/or aramid fiber. For example, spar caps 38 and 40 may include a layer (not shown) of core material, such as, but not limited to, balsa wood, PVC foam, Styrene Acryl Nitrate (SAN) foam, PE foam, a metal honeycomb, such as, but not limited to, an aluminum honeycomb, and/or a fabric, such as, but not limited to, a polyester core mat, sandwiched between two layers (not shown) of fiber. Although shown as having larger thickness than webs 42 and 44, each spar cap 38 and 40 may have a smaller, larger, or substantially equal thickness as webs 42 and/or 44. Each shear web 42 and 44 may include one or more layers (not shown), each of any suitable material(s) that enables shear webs 42 and 44 to function as described herein, such as, but not limited to, metal, plastic, wood, and/or fiber, such as, but not limited to, glass fiber, carbon fiber, and/or aramid fiber. For example, shear webs 42 and 44 may include a layer (not shown) of core material, such as, but not limited to, balsa wood, PVC foam, Styrene Acryl Nitrate (SAN) foam, PE foam, a metal honeycomb, such as, but not limited to, an aluminum honeycomb, and/or a fabric, such as, but not limited to, a polyester core mat, sandwiched between two layers (not shown) of fiber. Although shear webs 42 and 44 are each illustrated in
To support and/or strengthen shell 30 adjacent root section 26, blade 24 may include one or more additional layers 46 and 48 of material in addition to layers 32 and core material 34. Although two layers 46 and 48 are shown, shell 30 may include any number of additional layers for supporting and/or strengthen shell 30 adjacent root section 26. Moreover, layers 46 and 48 may extend along any portion of blade span length SL. In the exemplary blade 24, layers 46 and 48 extend along a length 50. Layers 46 and 48 provide additional support and/or strength to shell 30 at blade root section 26 to, for example, facilitate reducing or eliminating damage to blade shell 30 adjacent where shell connects to rotor hub 22 (shown in
The pre-fabricated component(s) may be a portion or all of any component of shell 30 and/or a portion or all of any component having any location within, on, and/or adjacent shell 30. In the exemplary embodiment method 100 includes stacking 106 a pre-fabricated spar cap 38 and/or 40 with layers 32 and core material 34 along the portion 108 (shown in
Once stacked, layers 32, core material 34, spar cap(s) 38 and/or 40, and layers 46 and 48 are laminated 110 with a resin to bond them together. Any suitable lamination process may be used, such as, but not limited to, a resin transfer molding (RTM) process, a resin film infusion (RFI) process, heating the stack for any suitable time at any suitable temperature, drying the stack at room temperature and atmospheric pressure for any suitable time, and/or the application of pressure to the stack. In some embodiments, the resin is infused into the stack using pressure, heat, and/or a vacuum bag system (not shown) such as that used with a resin transfer molding process. The pressure and/or vacuum bag system may also facilitate forming the stack into the shape of the mold. In some embodiments, layers 32 and/or core material are prepregged with resin before stacking in the mold. Moreover, in some embodiments layers 32, core material 34, spar cap(s) 38 and/or 40, and/or layers 46 and/or 48 are coated with resin prior to stacking.
The pre-fabricated component(s) may be a portion or all of any component of shell 30 and/or a portion or all of any component having any location within, on, and/or adjacent to shell 30. In the exemplary embodiment, method 200 includes positioning 206 a pre-fabricated spar cap 38 and/or 40 adjacent one or more layers 32 and/or core material 34 along the portion 108 (shown in
Once stacked (wound and positioned), layers 32, core material 34, spar cap(s) 38 and/or 40, and layers 46 and 48 are laminated 110 with a resin to bond them together. Any suitable lamination process may be used, such as, but not limited to, a resin transfer molding (RTM) process, a resin film infusion (RFI) process, heating the stack for any suitable time at any suitable temperature, drying the stack at room temperature and atmospheric pressure for any suitable time, and/or the application of pressure to the stack. In some embodiments, the resin is infused into the stack using pressure, heat, and/or a vacuum bag system (not shown) such as that used with a resin transfer molding process. The pressure and/or vacuum bag system may also facilitate forming the stack into the shape of the mandrel. In some embodiments, layers 32 and/or core material are prepregged with resin before winding and/or positioning on the mandrel. Moreover, in some embodiments layers 32, core material 34, spar cap(s) 38 and/or 40, and/or layers 46 and/or 48 are coated with resin prior to winding and/or positioning.
The herein-described methods are cost-effective and reliable for fabricating rotor blades. For example, by stacking and/or positioning pre-fabricated components with layers of other material(s), the methods described and/or illustrated herein may facilitate increasing a structural integrity of fabricated rotor blades and/or may facilitate increasing quality control over fabricated rotor blades. Moreover, and for example, such pre-fabricated components may facilitate decreasing a fabrication time of rotor blades, which may facilitate increasing a number of rotor blades fabricated within a predetermined amount of time and/or by a single fabrication entity.
Although the methods described and/or illustrated herein are described and/or illustrated herein with respect to rotor blades, and more specifically wind turbine rotor blades, the methods described and/or illustrated herein are not limited to wind turbine rotor blades, nor rotor blades generally. Rather, the methods described and/or illustrated are applicable to fabricating any blade or airfoil.
Exemplary embodiments of methods are described and/or illustrated herein in detail. The methods are not limited to the specific embodiments described herein, but rather, steps of each method may be utilized independently and separately from other steps described herein. Each method's steps can also be used in combination with other method steps, whether described and/or illustrated herein.
When introducing elements of the methods described and/or illustrated herein, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that embodiments (whether described and/or illustrated herein) of the present invention can be practiced with modification within the spirit and scope of the claims.
