Patent Application
20140178204
The subject matter disclosed herein relates generally to wind turbines, and more particularly to wind turbine rotor blades with fiber reinforced portions.
Recently, wind turbines have received increased attention as an environmentally safe and relatively inexpensive alternative energy source. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
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, rotationally coupled to the rotor through a gearbox or directly coupled to the rotor. The gearbox, when present, 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.
Known wind turbine blades are fabricated by infusing a resin into a fiber wrapped core. However, because some sections of the blade are thicker to accommodate high loads, known methods of infusing resins into thick parts do not always produce a defect free part within a cycle time that is no longer than the pot life of the infusion resin. One problem that can occur is the formation of dry spots where the infused resin has not reached. Some known solutions to these problems are to use added pre and/or post processes to infuse resin into dry spots. However, these processes typically result in increased direct labor costs, increased part cycle time, and increased facilitation by machines or equipment for the additional processing.
Accordingly, alternative wind turbine rotor blades having fiber reinforced portions, and methods for making the same, would be welcomed in the art.
In one embodiment, a method is disclosed of manufacturing a fiber reinforced portion of a wind turbine rotor blade. The method includes disposing a continuous fiber mat adjacent a prefabricated layer, wherein the continuous fiber mat comprises randomly arranged reinforcing fibers and wherein the prefabricated layer comprises reinforcing fibers and a cured polymeric resin. The method further includes disposing a structural layer adjacent the continuous fiber mat opposite the prefabricated layer, wherein the structural layer comprises reinforcing fibers. The method then includes infusing a polymeric resin through at least the continuous fiber mat and curing the resin to form the fiber reinforced portion of the wind turbine rotor blade.
In another embodiment, a method is disclosed of manufacturing a fiber reinforced portion of a wind turbine rotor blade. The method includes disposing a structural layer adjacent a prefabricated layer, wherein the structural layer comprises reinforcing fibers and wherein the prefabricated layer comprises reinforcing fibers and a cured polymeric resin. The method further includes disposing a continuous fiber mat adjacent the structural layer opposite the prefabricated layer, wherein the continuous fiber mat comprises randomly arranged reinforcing fibers. The method then includes infusing a polymeric resin through at least the continuous fiber mat and curing the resin to form the fiber reinforced portion of the wind turbine rotor blade.
In yet another embodiment, a wind turbine rotor blade comprising a fiber reinforced portion is disclosed. The fiber reinforced portion includes a prefabricated layer comprising reinforcing fibers and a cured polymeric resin, a continuous fiber mat adjacent the prefabricated layer, the continuous fiber mat comprising randomly arranged reinforcing fibers, and a polymer resin infused through at least the continuous fiber mat.
These and additional features provided by the embodiments discussed herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.
The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the inventions defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
A method of fabricating fiber reinforced portions of a wind turbine rotor blade is described below in detail. The method uses the addition of mats formed from randomly arranged reinforcing fibers adjacent preformed layers and/or other structural layers. The random fiber mats facilitate the infusion of a polymeric resin throughout the thickness of the fiber reinforced portion of the blade and the elimination of “dry spots” in the structure. The method reduces cycle times and cost by eliminating the need for secondary processes of building up thick sections of the wind turbine blade, e.g., the root section.
Referring to the drawings,
Various components of wind turbine 100, in the exemplary embodiment, are housed in nacelle 106 atop tower 102 of wind turbine 100. The height of tower 102 is selected based upon factors and conditions known in the art. In some configurations, one or more microcontrollers in a control system are used for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application and fault monitoring. Alternative distributed or centralized control architectures are used in alternate embodiments of wind turbine 100. In the exemplary embodiment, the pitches of blades 114 are controlled individually. Hub 112 and blades 114 together form wind turbine rotor 110. Rotation of rotor 110 causes a generator (not shown in the figures) to produce electrical power.
In use, blades 114 are positioned about rotor hub 112 to facilitate rotating rotor 110 to transfer kinetic energy from the wind into usable mechanical energy. As the wind strikes blades 114, and as blades 114 are rotated and subjected to centrifugal forces, blades 114 are subjected to various bending moments. As such, blades 114 deflect and/or rotate from a neutral, or non-deflected, position to a deflected position. Moreover, a pitch angle of blades 114 can be changed by a pitching mechanism (not shown) to facilitate increasing or decreasing blade 114 speed, and to facilitate reducing tower 102 strike.
Referring now to
The continuous fiber mat 220 comprises randomly arranged reinforcing fibers. The randomly arranged reinforcing fibers allow the infusion of resin so that the resin can be better distributed throughout the entirety of the fiber reinforced portion 200 during manufacturing. Similar to above, the reinforcing fibers of the continuous fiber mat 220 can comprise any fibers suitable for providing structural support to a wind turbine 100 rotor blade 114. For example, reinforcing fibers include, but are not limited to, glass fibers, graphite fibers, carbon fibers, polymeric fibers, ceramic fibers, aramid fibers, kenaf fibers, jute fibers, flax fibers, hemp fibers, cellulosic fibers, sisal fibers, coir fibers and combinations thereof. In some embodiments, the reinforcing fibers in the continuous fiber mat 220 can comprise the same type of reinforcing fibers in the prefabricated layer 210. In other embodiments, the reinforcing fibers in the continuous fiber mat 220 can comprise different types of reinforcing fibers than in the prefabricated layer 210.
Referring to
The structural layer 230 can have a higher reinforcing fiber density than the continuous fiber mat 220. The reinforcing fiber density refers to the amount of reinforcing fiber present in a given volume. Thus, structural layers 230 comprising woven, stitched or otherwise aligned reinforced fibers can have a higher reinforcing fiber density than the continuous fiber mat 220 with its randomly arranged reinforcing fibers. The lower reinforcing fiber density of the continuous fiber mat 220 can allow for increased infusion of resin into the fiber reinforced portion 200 and 201 while the higher reinforcing fiber density of the structural layer 230 can provide greater structural support to the fiber reinforced portion 200 and 201. The combination of the prefabricated layer 210, continuous fiber mat 220 and structural layer 230 allows for the quicker and more efficient manufacturing of thicker fiber reinforced portions 200 and 201 while still providing sufficient infusion of resin and sufficient strength in the final product.
As illustrated in
In other embodiments, such as that illustrated in
With reference to
While specific embodiments of fiber reinforced portions have been disclosed herein (e.g.,
Referring now also to
The method 300 then comprises infusing polymeric resin in step 330 and subsequently curing in step 340. The resin may be infused in step 330 using any suitable process that allows the resin to fully infuse throughout the at least continuous fiber mat such as using vacuum bags, pressure differentials or the like. In some embodiments, where the structural layer comprises glass fibers or carbon fibers, the resin may also be infused into said structural layer. In some embodiments, where a prefabricated layer (already comprising cured resin) is present in the fiber reinforced portion, the resin infused in step 330 may infuse up to the surface of the prefabricated layer to effectively bond the different layers together upon curing in step 340. Curing can then occur in step 340 at any temperature and for any amount of time that allows infused polymeric resin to harden thereby providing a fiber reinforced portion having a solid structure. The curing in step 340 may also occur at any ramp rate (including both increases and decreases in temperature, or combinations thereof) and can occur in any suitable environment (e.g., an open or inert atmosphere).
It should now be appreciated that fiber reinforced portions may be manufactured using a variety of combinations of continuous fiber mats, structural layers and/or prefabricated layers. The combination of such layers can both allow for suitable infusibility of polymeric resin during manufacturing while also providing the necessary structural strength once the fiber reinforced portion is cured. The fiber reinforced portions may thereby build up thickness and strength through a more efficient and reproducible manufacturing process. Furthermore, the reinforced portion may then be utilized for a variety of different portions of a wind turbine rotor blade or wherever the increased strength may be employed.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
