Wind turbine rotor and methods of assembling the same

A rotor for coupling to a shaft is provided. The rotor includes a space frame hub having a central portion coupled to the shaft and a first structural member coupled to said central portion, wherein the first structural member has a first length. The rotor further includes a first blade coupled to the first structural member and having a tip end spaced from the shaft at a second length that is longer than the first length.

BACKGROUND OF THE DISCLOSURE

The embodiments described herein relate generally to wind turbines, and more particularly, to methods and systems for improving efficiency of a wind turbine rotor.

Some wind turbines may include a cast iron hub coupled to a shaft of a wind turbine, wherein the blades are coupled to the hub. More particularly, conventional wind turbine rotors may use a three-bladed configuration wherein root ends of the blades are coupled to the hub. These root ends, however, may not be aerodynamically shaped and may not produce power from the wind. More particularly, a portion of the blade near the root end may not produce any appreciable aerodynamic lift.

In order to reach higher energy conversion, the aerodynamic efficiency of the wind turbine may be improved by increasing the blade size of the wind turbine. Increasing the blade size, however, usually involves increasing the size of other components and machinery of the wind turbine which may lead to higher wind turbine costs. More particularly, transportation costs, fabrication costs and/or installation costs can increase for larger sized blades. Moreover, increasing the blade size may result in a higher load on a pitch assembly and a yaw assembly, and in particular, the respective bearings of these assemblies due to bending moments and/or thrust forces created by large rotor blades. More particularly, bending moments and/or thrust forces can override the charging limit of typical bearings.

Moreover, due to the aerodynamic loads experienced during operations, larger blades may experience flap and in-plane bending moments at the root ends which may reduce efficiency of the wind turbine. Aerodynamic loads may cause deflection at the tip ends of large blades, wherein excessive tip deflection can be catastrophic if the blades contact the wind turbine tower.

BRIEF DESCRIPTION OF THE DISCLOSURE

In one aspect, a rotor for coupling to a shaft is provided. The rotor includes a space frame hub having a central portion coupled to the shaft and a first structural member coupled to the central portion, wherein the first structural member has a first length. The rotor further includes a first blade coupled to the first structural member and having a tip end spaced from the shaft at a second length that is longer than the first length.

In another aspect, a wind turbine is provided. The wind turbine includes a tower; a nacelle coupled to the tower; a shaft coupled to the nacelle; and a rotor coupled to the tower. The rotor includes a space frame hub having a central portion coupled to the shaft. A plurality of structural members is coupled to the central portion, wherein each member of the plurality of structural members has a first length. The rotor further includes a plurality of blades, wherein each blade of the plurality of blades is coupled to a respective portion of the plurality of portions and each blade has a tip end spaced from the shaft at a second length that is longer than the first length. A pitch assembly is coupled to each portion of the plurality of portions and to each blade of the plurality of blades.

In another aspect, a method of assembling a rotor to a shaft is provided. The method includes radially coupling a space frame portion to a space frame central portion; coupling a pitch assembly to the space frame portion; coupling a blade to the space frame portion and the pitch assembly; and coupling the space frame central portion to the shaft.

DETAILED DESCRIPTION OF THE DISCLOSURE

The embodiments described herein relate to wind turbines and methods of assembling a wind turbine. More particularly, the embodiments relate to a rotor that is configured to facilitate minimizing bending moments of the rotor blades and minimizing tip deflection of the rotor blades. It should be understood that the embodiments described herein for rotors are not limited to wind turbines, and should be further understood that the descriptions and figures that utilize a rotor and a wind turbine are exemplary only.

FIG. 1is a schematic view of an exemplary wind turbine100. In the exemplary embodiment, wind turbine100is a horizontal-axis wind turbine. Alternatively, wind turbine100may be a vertical-axis wind turbine. In the exemplary embodiment, wind turbine100includes a tower102extending from and coupled to a supporting surface104. Tower102may be coupled to surface104with anchor bolts or via a foundation mounting piece (neither shown), for example. A nacelle106is coupled to tower102, and a rotor108is coupled to nacelle106. Rotor108includes a rotatable hub110and a plurality of rotor blades112coupled to hub110. In the exemplary embodiment, rotor108includes three rotor blades112. Alternatively, rotor108may have any suitable number of rotor blades112that enables wind turbine100to function as described herein. Tower102may have any suitable height and/or construction that enables wind turbine100to function as described herein.

Rotor blades112are spaced about hub110to facilitate rotating rotor108, thereby transferring kinetic energy from wind114into usable mechanical energy, and subsequently, electrical energy. Rotor108and nacelle106are rotated about tower102on a yaw axis116to control a perspective of rotor blades112with respect to a direction of wind114. Rotor blades112are mated to hub110by coupling a rotor blade root portion118to hub110at a plurality of load transfer regions120. Load transfer regions120each have a hub load transfer region (not shown) and a rotor blade load transfer region (not shown). Loads induced to rotor blades112are transferred to hub110via load transfer regions120. Each rotor blade112also includes a rotor blade tip portion122.

In the exemplary embodiment, rotor blades112have a length of between approximately 30 meters (m) (99 feet (ft)) and approximately 120 m (394 ft). Alternatively, rotor blades112may have any suitable length that enables wind turbine100to function as described herein. For example, rotor blades112may have a suitable length less than 30 m or greater than 120 m. As wind114contacts rotor blade112, lift forces are induced to rotor blade112and rotation of rotor108about an axis of rotation124is induced as rotor blade tip portion122is accelerated.

FIG. 2is a partial sectional view of nacelle106used with wind turbine100. In the exemplary embodiment, various components of wind turbine100are housed in nacelle106. For example, in the exemplary embodiment, nacelle106includes pitch assemblies130. Moreover, in the exemplary embodiment, rotor108is rotatably coupled to an electrical machine132, for example a generator, positioned within nacelle106via a rotor shaft134(sometimes referred to as either a main shaft or a low speed shaft), a gearbox136, a high speed shaft138, and a coupling140. Rotation of rotor shaft134rotatably drives gearbox136that subsequently drives high speed shaft138. High speed shaft138rotatably drives generator132via coupling140and rotation of high speed shaft138facilitates production of electrical power by generator132. Gearbox136is supported by a support142and generator132is supported by a support144. In the exemplary embodiment, gearbox136uses a dual path geometry to drive high speed shaft138. Alternatively, rotor shaft134may be coupled directly to generator132via coupling140.

Nacelle106also includes a yaw drive mechanism146that rotates nacelle106and rotor108about yaw axis116to control the perspective of rotor blades112with respect to the direction of wind114. Nacelle106also includes at least one meteorological mast148that, in one embodiment, includes a wind vane and anemometer (neither shown inFIG. 2). In one embodiment, meteorological mast148provides information, including wind direction and/or wind speed, to a turbine control system150. Turbine control system150includes one or more controllers or other processors configured to execute control algorithms. As used herein, the term “processor” includes any programmable system including systems and microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), programmable logic circuits (PLC), and any other circuit capable of executing the functions described herein. The above examples are exemplary only, and thus are not intended to limit in any way the definition and/or meaning of the term processor. Moreover, turbine control system150may execute a SCADA (Supervisory, Control and Data Acquisition) program.

Pitch assembly130is operatively coupled to turbine control system150. In the exemplary embodiment, nacelle106also includes forward support bearing152and aft support bearing154. Forward support bearing152and aft support bearing154facilitate radial support and alignment of rotor shaft134. Forward support bearing152is coupled to rotor shaft134near hub110. Aft support bearing154is positioned on rotor shaft134near gearbox136and/or generator132. Nacelle106may include any number of support bearings that enable wind turbine100to function as disclosed herein. Rotor shaft134, generator132, gearbox136, high speed shaft138, coupling140, and any associated fastening, support, and/or securing device including, but not limited to, support142, support144, forward support bearing152, and aft support bearing154, are sometimes referred to as a drive train156.

FIG. 3is a perspective view of rotor108which includes hub110, blades112and a dome158(portions removed for illustrative purposes). Hub110is coupled to shaft134and dome158is coupled to hub110. In the exemplary embodiment, hub110includes a space frame structure160which has a truss-like, lightweight rigid configuration formed by interlocking struts162in a geometric pattern164. Space frame structure160can include any configuration and/or pattern to enable rotor108to function as described herein. Space frame structure160is configured to support the plurality of blades112away from shaft134while minimizing blade length and/or blade mass.

FIG. 4illustrates a perspective view of hub110which includes a central portion166and a plurality of structural members168coupled to central portion166. Central portion166is coupled to shaft134and includes a plurality of strut members170. In the exemplary embodiment, strut members170are configured in a space frame configuration having a polyhedron shape172. More particularly, strut members170can be configured in a tetrahedron shape or a square-pyramid shape. Strut members170can include any shape to enable central portion166to function as described herein. Strut members170are configured to provide a lightweight and rigid configuration for supporting structural members168. Strut members170include materials such as, but not limited to, metals, plastics, alloys, composites and combinations thereof. Moreover, strut members170can include damping elements (not shown) such as, for example, shock absorbers and damping coatings.

Structural members168are coupled to central portion166and are configured to radially extend therefrom. In the exemplary embodiment, structural members168are radially coupled to central portion166and are orientated about 60% from each other. Alternatively, structural members168can extend from central portion166at any angular relationship. Structural members168include a first member174, a second member176and a third member178. Structural members168may include more than three members or less than three members to enable rotor108to function as described herein. Each first member174, second member176and third member178includes a first end180and a second end182. Second end182includes a pitch bearing support ring184which is configured to couple to pitch assembly130(shown inFIG. 2).

First member174, second member176and third member178include a plurality of primary members186coupled to first end180and second end182. Each first member174, second member176and third member178further includes a plurality of secondary members188coupled to the plurality of primary members186. Primary and secondary members186and188are configured to provide a lightweight and rigid configuration for supporting blades112. Moreover, each structural member168includes a cross strut member190coupled to primary members186and secondary members188. Cross strut member190is configured to facilitate tensioning primary member and secondary members186and188. In one embodiment, structural members168are aerodynamically shaped to receive wind114(shown inFIG. 1) to facilitate rotating shaft134. More particularly, structural members168can include blades and/or vanes (not shown) to receive wind114to facilitate rotating shaft134.

In the exemplary embodiment, primary members186are configured in a space frame configuration having a polyhedron shape172. Moreover, secondary members188are configured in a space frame configuration having polyhedron shape172. Alternatively, primary members and secondary members186and188can include any shape to enable structural members168to function as described herein. Moreover, primary and secondary members186and188include materials such as, but not limited to, metals, plastics, alloys, composites and combinations thereof. Primary and second members186and188can include damping elements (not shown) such as, but not limited to, shock absorbers and damping coatings.

FIG. 5is another perspective view of hub110, blades112and dome158. In the exemplary embodiment, blades112are coupled to the plurality of structural members168. More particularly, blades112includes a first blade192coupled to first member174, a second blade194coupled to second member176and a third blade196coupled to third member178. Blades112may include more than three blades112or less than three blades112. Blades112may include any number of blades112to enable rotor108to function as described herein.

First blade192, second blade194and third blade196include a root end198, a tip end200and blade surface126between root end198and tip end200. Root end198is coupled to second end portion182of each portion168and spaced away from shaft134. Each blade192,194, and196further includes an aerodynamic fairing202coupled to root end198. Fairing202is configured to receive wind114to facilitate rotating shaft134, wherein each fairing202includes an outer surface204and an inner surface206. Outer surface204is configured to receive wind114to increase aerodynamic lift to facilitate rotating shaft134. Inner surface206defines a void208between outer surface204and root end198, wherein void208is configured to reduce weight of fairing202.

Dome158is coupled to at least one of first member174, second member176and third member178. In the exemplary embodiment, dome158is semi-circular shaped and configured to direct wind114toward fairings202to facilitate rotating shaft134. Alternatively, dome158can include other aerodynamic shapes, such as, for example, blades and vanes. Dome158can include any shape to enable rotor108to function as described herein. Dome158includes an outer surface210and an inner surface212, wherein inner surface212is coupled to second end182. Inner surface212is positioned adjacent to fairings202to facilitate minimizing and/or eliminating air gaps between dome158and fairings202to maximize directing wind114toward fairings202.

FIG. 6illustrates a cross sectional view of hub110and blade112. Pitch assembly130is coupled to each blade112and each structural member168, wherein each pitch assembly130is configured to modulate a pitch of associated blade112about pitch axis128. In the exemplary embodiment, pitch assembly130is coupled to bearing support ring184of each second end182. Pitch assembly130includes a pitch motor214and a bearing216, wherein a tube spar218of each blade112is coupled to a bearing housing217.

A pitch angle (not shown) of blades112, i.e., an angle that determines the perspective of blade112with respect to the direction of wind114, may be changed by pitch assembly130. More specifically, increasing a pitch angle of blade112decreases an amount of blade surface area126exposed to wind114and, conversely, decreasing a pitch angle of blade112increases an amount of blade surface area126exposed to wind114. The pitch angles of blades112are adjusted about pitch axis128at each blade112. In the exemplary embodiment, the pitch angles of blades112are controlled individually. Alternatively, the pitch angles of blades112can be controlled in groups.

Each structural member168has a first length L1as measured from second end182to shaft134. Moreover, each blade112is spaced from shaft134at a second length L2as measured from tip end200to shaft134. First length L1is different than second length L2. In the exemplary embodiment, first length L1is shorter than second length L2. More particularly, first length L1is about 10% to about 50% of second length L2. In one embodiment, first length L1is about 20% of second length L2. First and second lengths L2are sized to facilitate maximizing aerodynamic lift of blades112and minimizing blade length and/or blade mass. Moreover, first and second lengths L1and L2are sized to minimize blade bending moments and blade tip deflections. Alternatively, first length L1can be about the same as or longer than second length L2. First and second lengths L1and L2can include any size that enables rotor108to function as described herein.

Central portion166structural members168of hub110are sized and shaped to increase strength of rotor108via primary and secondary members186and188between blade root ends198and shaft134to increase efficiency of rotor108. Central portion166and structural members168are configured to minimize bending moments at root ends198by up to 50% as compared to conventional, cantilevered blades (not shown). Moreover, central portion166and structural members168are configured to minimize deflection of blade tip ends200by up to about 50% as compared to conventional, cantilevered blades. More particularly, central portion166and structural members168are configured to reduce bending moments at root ends198by up to about 30% and deflection of tip ends200by up to about 40% as compared to conventional, cantilevered blades.

FIG. 7is a front view of rotor108shown inFIG. 3. Since central portion166and structural members168are configured to extend outward from shaft134and support blades112away from shaft134, blade length can be reduced as compared to conventional blades. Moreover, a reduced blade length results in a lighter and less expensive blade to manufacture due to less material. In the exemplary embodiment, portion first length L1(shown inFIG. 6) is about 20% of second length L2(shown inFIG. 6) to facilitate reducing blade length. Reduced blade length results in a lighter and less expensive pitch assembly130needed due to lesser loads applied by blades112to pitch assembly130, and in particular, pitch assembly bearing216. Moreover, pitch assembly130is coupled to second end182where blade bending moments are up to about 50% less as compared to blade bending moments at first end180. Since pitch assembly130is coupled to second end182and experiences less bending moments, pitch assembly130is lighter and less expensive.

Second length L2reduces material cost, manufacturing cost, transportation costs and/or installation costs for blades112while reducing up-tower mass. With space frame hub110extending from shaft134, rotor diameter RD is substantially the same as compared to conventional rotor diameters (not shown) while rotor108includes reduced sized blades112. Alternatively, rotor diameter RD can be increased by using conventional blades (not shown) since space frame hub110extends blades112beyond shaft134. In the exemplary embodiment, dome158is sized from about 10% to about 30% of rotor diameter RD. More particularly, dome158is sized up to about 20% of rotor diameter RD. Dome158can be any size to enable rotor108to function as described herein. Dome158is sized and shaped to direct wind114toward fairing202. Alternatively, dome158can be removed to expose aerodynamically shaped portions168which are configured to receive wind114to facilitate rotating shaft134.

FIG. 8illustrates an exemplary flowchart illustrating a method800of assembling a rotor, for example rotor108(shown inFIG. 3). Method800includes forming802a space frame central portion, for example central portion166(shown inFIG. 4), from a plurality of struts, such as struts170(shown inFIG. 4). In the exemplary method800, the space frame portion is formed into a polyhedron shape, for example polyhedron shape162(shown inFIG. 3). A space frame portion, such as space frame portion168(shown inFIG. 4), is also formed804from a plurality of members, for example members186and188(shown inFIG. 4). The space frame portion includes a first member, a second member and a third member, for example first member174, second member176and third member178(shown inFIG. 4). The space frame portion is coupled806to the space frame central portion. Method800includes coupling808a pitch assembly, for example pitch assembly130(shown inFIG. 6), to each member.

Method800includes coupling810a blade, such as blade112(shown inFIG. 3), to the space frame portion. In the exemplary embodiment, blade includes a first blade, a second blade and a third blade, for example first blade192, second blade194and third blade196(shown inFIG. 3), which are coupled to the first member, the second member and the third member respectively. Moreover, the blade is coupled812to the pitch assembly.

In the exemplary embodiment, method800includes coupling814an aerodynamic fairing, for example fairing202(shown inFIG. 3), to the blade. More particularly, fairing is coupled to a root end, for example root end198(shown in FIG.3), of the blade. Moreover, method800includes coupling816a dome, such as dome158(shown inFIG. 5), to the space frame portion. More particularly, dome is coupled to a second end, for example, second end182(shown inFIG. 3). Method800further includes coupling818the central portion to a shaft, for example shaft134(shown inFIG. 5).

The embodiments described herein relate to a rotor configured to enhance aerodynamic efficiency of a wind turbine to increase higher energy conversion. The embodiments described herein reduce manufacturing costs, transportation costs and/or installation costs. Moreover, the embodiments described herein reduce blade bending moments and/or blade tip deflection and/or loads applied to turbine components such as pitch assemblies and yaw assemblies.

A technical effect of the systems and methods described herein includes at least one of: a rotor having a space frame hub having a central portion coupled to the shaft and a first member coupled to the central portion, wherein the first member has a first length; and a first blade coupled to the first member and having a second length that is longer than the first length.

Exemplary embodiments of a rotor and methods for assembling the rotor are described above in detail. The methods and systems are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods may also be used in combination with other manufacturing systems and methods, and are not limited to practice with only the systems and methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other electrical component applications.