Patent Publication Number: US-2012025538-A1

Title: Unitary support frame for use in wind turbines and methods for fabricating same

Description:
BACKGROUND OF THE INVENTION 
     The subject matter described herein relates generally to wind turbines and, more particularly, to a support frame for use in wind turbines and methods for fabricating a support frame. 
     At least some known wind turbine towers include a nacelle fixed atop a tower. The nacelle includes a rotor assembly coupled to a gearbox and to a generator through a rotor shaft. In known rotor assemblies, a plurality of blades extend from a rotor. The blades are oriented such that wind passing over the blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity. 
     Because many known wind turbines provide electrical power to utility grids, at least some wind turbines have larger components (e.g., rotors in excess of thirty-meters in diameter) that facilitate supplying greater quantities of electrical power. However, the larger components are often subjected to increased loads (e.g., asymmetric loads) that result from wind shears, yaw misalignment, and/or turbulence, and the increased loads have been known to contribute to significant fatigue cycles on the gearbox assembly and/or other components of the wind turbine. 
     At least some known wind turbines include a support frame assembly for supporting the rotor assembly, gearbox and/or generator from the tower. Known support frame assemblies include a bedplate frame and at least one bearing support assembly that are coupled together to form the support frame assembly. In addition, at least some known wind turbines include generator support frame or a “rear frame” that is cantilevered from the bedplate frame. At least some known support frame assemblies include a plurality of sections that are coupled together to form the bedplate frame. Known support frame assemblies may be subjected to stresses that cause fatigue cracking and/or failure, particularly at the joints between the bedplate sections. Over time, the joints and fasteners between the bedplate sections may become worn, which may cause damage to the rotor assembly, gearbox, and/or generator. In at least some known wind turbines, the repair of the rotor assembly, gearbox, and/or generator requires the rotor assembly, gearbox, and generator to be removed from the wind turbine prior to repairing and/or replacing the damaged rotor assembly, gearbox, and generator. In some wind turbines, the rotor blades are between 37 and 50 meters in length, and as such, repairing worn or damaged rotor assemblies, gearboxes, and generators can be costly and time-consuming. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a support frame for use in a wind turbine is provided. The wind turbine includes a tower and a rotor that is rotatably coupled to a rotor shaft. The support frame includes an upper portion including an inner surface, an outer surface, and at least one bearing housing that is sized to receive the rotor shaft therethrough. A lower portion is integrally formed with the upper portion and extends from the upper portion. The lower portion includes a support flange that is configured to be coupled to the tower to support the rotor shaft and the rotor from the tower. 
     In another aspect, a wind turbine is provided. The wind turbine includes a tower and a rotor that is rotatably coupled to a rotor shaft. The rotor shaft defines a centerline axis. A support frame is coupled to the rotor shaft for supporting the rotor from the tower. The support frame includes an upper portion including an inner surface, an outer surface, and at least one bearing housing that is sized to receive the rotor shaft therethrough. A lower portion is integrally formed with the upper portion and extends from the upper portion. The lower portion includes a support flange that is configured to be coupled to the tower to support the support frame from the tower. 
     In yet another aspect, a method of fabricating a support frame for use in a wind turbine is provided. The method includes forming a molding assembly that includes a cavity having a shape substantially similar to the support frame. The support frame includes an upper portion and a lower portion that extends from the upper portion. The upper portion includes at least one bearing housing sized to receive a wind turbine rotor shaft therethrough. The lower portion includes a support flange configured to be coupled to a wind turbine tower to support the support frame from the tower. A metal alloy is deposited within the cavity to integrally form the support frame including the upper portion and the lower portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary wind turbine. 
         FIG. 2  is a schematic view of a portion of the wind turbine shown in  FIG. 1  including an exemplary support frame. 
         FIG. 3  is a perspective view of the support frame shown in  FIG. 2 . 
         FIG. 4  is another perspective view of the support frame shown in  FIG. 2 . 
         FIG. 5  is a flow chart illustrating an exemplary method that may be used for fabricating a support frame for use in a wind turbine shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments described herein overcome at least some disadvantages of known wind turbines by providing a support frame that is formed as a unitary component. More specifically, the support frame described herein includes an upper portion having a bearing housing configured to support a rotor shaft, and a lower portion formed integrally with the upper portion and having a support flange configured to support the support frame from a wind turbine tower. The unitary support frame provides an increased structural integrity over known bedplate frames by eliminating the need for bolted and/or welded sections that increase the overall weight of known bedplate frames and increase areas that are subject to stress and fatigue. In addition, by providing a support frame that is a unitary component, the cost of manufacturing and assembling the support frame is reduced. 
       FIG. 1  is a perspective view of an exemplary wind turbine  10 . In the exemplary embodiment, wind turbine  10  is a horizontal-axis wind turbine. Alternatively, wind turbine  10  may be a vertical-axis wind turbine. In the exemplary embodiment, wind turbine  10  includes a tower  12  that extends from a supporting surface  14 , a support frame  16  mounted on tower  12 , and a nacelle  18  coupled to support frame  16 . Wind turbine  10  also includes a gearbox  20  coupled to support frame  16  and positioned within nacelle  18 , a generator  22  coupled to gearbox  20 , and a rotor  24  rotatably coupled to gearbox  20  with a rotor shaft  26 . A generator frame  28  is coupled to support frame  16  such that generator frame  28  is cantilevered from support frame  16 . Generator  22  is coupled to generator frame  28  such that generator  22  is supported from support frame  16  with generator frame  28 . In an alternative embodiment, wind turbine  10  does not include gearbox  20 , and rotor  24  is rotatably coupled to generator  22 . In such an embodiment, wind turbine  10  does not include generator frame  28 , and generator  22  is coupled to support frame  16 . 
     In the exemplary embodiment, nacelle  18  includes a housing  30  coupled to support frame  16  and including an inner surface  32  that defines a nacelle cavity  34 . Tower  12  includes an inner surface  36  that defines a tower cavity  38  extending between supporting surface  14  and nacelle  18 . Support frame  16  is coupled to tower  12  such that tower cavity  38  is in flow communication with nacelle cavity  34 . Rotor  24  includes a rotatable hub  40  coupled to rotor shaft  26 , and at least one rotor blade  42  coupled to and extending outwardly from hub  40 . Wind turbine  10  also includes a yaw drive assembly  44  for rotating rotor  24  about a yaw axis  46 . A yaw bearing  48  is coupled between tower  12  and support frame  16  and is configured to rotate support frame  16  with respect to tower  12  about yaw axis  46 . Yaw drive assembly  44  is coupled to support frame  16  and to yaw bearing  48  to facilitate rotating nacelle  18  and rotor  24  about yaw axis  46  to control the perspective of rotor blades  42  with respect to direction  50  of the wind. Nacelle  18 , generator  22 , gearbox  20 , rotor shaft  26 , and yaw drive assembly  44  are each mounted to support frame  16  for supporting nacelle  18 , generator  22 , gearbox  20 , rotor shaft  26 , and yaw drive assembly  44  from tower  12 . 
     In the exemplary embodiment, rotor  24  includes three rotor blades  42 . In an alternative embodiment, rotor  24  includes more or less than three rotor blades  42 . Rotor blades  42  are spaced about hub  40  to facilitate rotating rotor  24  to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. Rotor blades  42  are mated to hub  40  by coupling a blade root portion  52  to hub  40  at a plurality of load transfer regions  54 . In the exemplary embodiment, rotor blades  42  have a length ranging from about 10 meters (m) (99 feet (ft)) to about 120 m (394 ft). Alternatively, rotor blades  42  may have any suitable length that enables wind turbine  10  to function as described herein. For example, other non-limiting examples of rotor blade lengths include 20 m, 37 m, a length that is greater than 120 m, or a length that is less than 10 m. 
     During operation of wind turbine  10 , as wind strikes rotor blades  42  from wind direction  50 , rotor  24  is rotated about an axis of rotation  56  causing a rotation of rotor shaft  26  about axis  56 . A rotation of rotor shaft  26  rotatably drives gearbox  20  that subsequently drives generator  22  to facilitate production of electrical power by generator  22 . A pitch adjustment system (not shown) adjusts a pitch angle or blade pitch of rotor blades  42  to adjust a perspective of rotor blades  42  with respect to wind direction  50  to control the load imparted to rotor blades  42  from the wind, a rotational speed of rotor  24 , and/or a power generated by wind turbine  10 . Yaw drive assembly  44  adjusts an orientation of rotor  24  with respect to wind direction  50  to control the perspective of rotor blades  42  with respect to wind direction  50 . 
       FIG. 2  is a schematic view of a portion of wind turbine  10  including support frame  16 .  FIG. 3  is a perspective view of support frame  16 .  FIG. 4  is another perspective view of support frame  16 . Identical components shown in  FIG. 3  and  FIG. 4  are labeled with the same reference numbers used in  FIG. 2 . In the exemplary embodiment, rotor shaft  26  includes a substantially cylindrical body  58  that extends between a first end  60  and an opposite second end  62  along a centerline axis  64 . First end  60  is positioned adjacent hub  40  (shown in  FIG. 1 ) and includes a rotor flange  66  coupled to hub  40  such that a rotation of hub  40  facilitates rotating rotor shaft  26  about axis  64 . Second end  62  is rotatably coupled to gearbox  20  such that a rotation of rotor shaft  26  rotatably drives gearbox  20 . A high speed shaft  68  is rotatably coupled between gearbox  20  and generator  22  to enable gearbox  20  to rotatably drive generator  22 . During operation of wind turbine  10 , a rotation of rotor shaft  26  rotatably drives gearbox  20  that subsequently drives high speed shaft  68 . High speed shaft  68  rotatably drives generator  22  to facilitate production of electrical power by generator  22 . 
     In the exemplary embodiment, support frame  16  extends between a forward section  70  and an aft section  72  along a longitudinal axis  74  defined between forward section  70  and aft section  72 . Support frame  16  includes a sidewall  76  that includes an upper portion  78 , a lower portion  80 , and a transition portion  81  that extends between upper portion  78  and lower portion  80 . Lower portion  80  extends from upper portion  78  and is integrally formed with upper portion  78  and transition portion  81  such that support frame  16  is formed as a single, or unitary, component. In the exemplary embodiment, upper portion  78  includes an inner surface  82  and an outer surface  84 . Inner surface  82  includes at least one bearing housing  86  sized and shaped to receive rotor shaft  26  therethrough. Bearing housing  86  includes an inner surface  88  that defines an opening  90  having a substantially cylindrical shape. Opening  90  is configured to receive a support bearing (not shown) therein such that the support bearing is positioned between bearing housing  86  and rotor shaft  26 . The support bearing is configured to enable rotor shaft  26  to rotate with respect to support frame  16 . Bearing housing  86  includes a positioning shoulder  92  that extends radially inwardly from bearing inner surface  88  to facilitate orienting the support bearing with respect to rotor shaft  26 . Bearing housing  86  facilitates radial support and alignment of rotor shaft  26 . Upper portion  78  also includes one or more openings  94  extending through sidewall  76  to provide access to bearing housing  86 . 
     In the exemplary embodiment, upper portion  78  includes a first bearing housing, i.e. a forward bearing housing  96 , and a second bearing housing, i.e. an aft bearing housing  98 . Forward bearing housing  96  is positioned adjacent forward section  70 . Aft bearing housing  98  is oriented substantially coaxially with forward bearing housing  96  along centerline axis  64  and is positioned an axial distance  100  from forward bearing housing  96 . Aft bearing housing  98  has a similar size and shape to forward bearing housing  96  such that forward bearing housing  96  and aft bearing housing  98  are each configured to receive rotor shaft  26  therethrough. Rotor shaft  26  extends through forward bearing housing  96  and aft bearing housing  98  such that first end  60  is adjacent forward bearing housing  96  and second end  62  is adjacent aft bearing housing  98 . 
     Rotor shaft  26  includes a rotor locking disk  102  coupled to first end  60 . Rotor locking disk  102  defines a plurality of openings  104  each extending through rotor locking disk  102  and positioned circumferentially about rotor locking disk  102 . Support frame  16  includes a rotor lock assembly  106  that extends outwardly from upper portion  78  and is positioned adjacent forward section  70 . Rotor lock assembly  106  includes a support plate  108  that extends radially outwardly from upper portion outer surface  84  and a locking pin housing  110  that extends axially from support plate  108  towards rotor locking disk  102 . Locking pin housing  110  defines an opening  112  sized and shaped to receive a locking pin  114  therethrough. Locking pin housing  110  is positioned adjacent rotor locking disk  102  such that locking pin  114  is inserted through opening  112  and extends into a corresponding opening  104  of rotor locking disk  102  to facilitate locking rotor shaft  26  by limiting a rotation of rotor shaft  26  about axis  64 . Upper portion  78  also includes a plurality of mounting flanges  116  extending outwardly from outer surface  84 . Each mounting flange  116  is configured to support various components of wind turbine  10  including, but not limited to, access ladders, electrical and communication cable supports, electrical and control panels, and/or HVAC equipment. 
     In the exemplary embodiment, lower portion  80  includes a support flange  118  that extends outwardly from sidewall  76  and is configured to be coupled to tower  12  to enable support frame  16  to be supported from tower  12 . Support flange  118  includes an inner surface  120  and an outer surface  122 . Inner surface  120  is positioned adjacent tower  12 . Support flange  118  is oriented substantially parallel with yaw bearing  48  and includes a plurality of openings  124  that extend through support flange  118  from inner surface  120  to outer surface  122 . Each opening  124  is sized to receive a fastener therethrough to enable support flange  118  to be coupled to yaw bearing  48 . Support flange  118  includes a radially inner surface  126  that includes a substantially cylindrical shape and defines an opening  128  that extends through support flange  118  to provide access between nacelle cavity  34  and tower cavity  38 . 
     Forward and aft bearing housings  96  and  98  are positioned above support flange  118  such that rotor shaft first end  60  is supported a radial distance  130  from support flange  118 . In one embodiment, forward bearing housing  96  extends a distance  132  from support flange  118  along longitudinal axis  74 . In the exemplary embodiment, forward and aft bearing housings  96  and  98  are oriented such that rotor shaft  26  extends along centerline axis  64  at an oblique angle with respect to support flange outer surface  122 . Alternatively, forward and aft bearing housings  96  and  98  are oriented such that rotor shaft  26  is oriented substantially parallel with respect to support flange outer surface  122 . 
     In the exemplary embodiment, lower portion  80  includes a sidewall  134  that extends outwardly from support flange  118  between a lower section  136  and an upper section  138 . Lower section  136  is positioned adjacent support flange  118 . Upper section  138  extends from lower section  136  and includes a first support member  140  and an opposite second support member  142 . First and second support members  140  and  142  each extend along longitudinal axis  74  from forward section  70  to aft section  72 . First and second support members  140  and  142  are each configured to support gearbox  20  from sidewall  134 . More specifically, gearbox  20  includes a first torque arm  144  and a second torque arm (not shown) that is opposite first torque arm  144 . First torque arm  144  and the second torque arm each extend radially outwardly from an outer surface  148  of gearbox  20 . First torque arm  144  is coupled to first support member  140  and the second torque arm is coupled to second support member  142  to facilitate supporting gearbox  20  from support frame  16 . 
     First and second support members  140  and  142  each include a planar outer surface  150  configured to support a plurality of mounting pads  152  thereupon such that each mounting pad  152  is positioned between gearbox  20  and support frame  16 . Each mounting pad  152  is configured to selectively adjust a position and orientation of gearbox  20  with respect to support frame  16  and rotor shaft  26 . Planar outer surfaces  150  of first and second support members  140  and  142  are each oriented substantially parallel to support flange outer surface  122 . In the exemplary embodiment, first and second support members  140  and  142  are oriented at an oblique angle with respect to rotor shaft  26  and centerline axis  64 . Alternatively, first and second support members  140  and  142  may be oriented substantially parallel to centerline axis  64 . In an alternative embodiment, wind turbine  10  does not include gearbox  20  and first and second support members  140  and  142  are each configured to support generator  20  from sidewall  134 . 
     In the exemplary embodiment, support flange  118  includes a yaw support  154  that extends outwardly from sidewall outer surface  84 . Yaw support  154  defines one or more openings  156  that extend between inner and outer surfaces  120  and  122 , and are each sized to receive yaw drive assembly  44  therethrough. Yaw support  154  is configured to at least partially support yaw drive assembly  44  from support flange  118 . Yaw drive assembly  44  is positioned within opening  156  and is coupled to yaw support  154  to at least partially support yaw drive assembly  44  from support flange  118 . In the exemplary embodiment, sidewall  76  includes one or more nacelle mounting flanges  158  that extend outwardly from sidewall outer surface  84 . Nacelle  18  is coupled to nacelle mounting flange  158  such that nacelle  18  is supported from support frame  16  with nacelle mounting flange  158 . In one embodiment, lower portion  80  includes one or more mounting flanges  158 . Alternatively, upper portion  78  includes mounting flanges  158 . 
     Lower portion  80  also includes at least one generator support assembly  160  that extends outwardly from sidewall  134  towards generator  22  along longitudinal axis  74 . Generator support assembly  160  includes an upper flange  162  that extends outwardly from support members  140  and  142 , and a lower flange  164  that extends between upper flange  162  and support flange  118 . Upper flange  162  is oriented at an oblique angle with respect to support members  140  and  142 . In the exemplary embodiment, lower flange  164  includes a planar outer surface  166  that extends between support flange  118  and upper flange  162 , and is oriented substantially perpendicularly with respect to support flange outer surface  122 . Upper and lower flanges  162  and  164  are oriented such that an opening  168  is defined between generator support assembly  160  and sidewall  134  to facilitate reducing a weight of support frame  16 . 
     In the exemplary embodiment, lower portion  80  includes a first generator support assembly  170  and an opposite second generator support assembly  172  each extending outwardly from aft section  72  along longitudinal axis  74 . Each first and second generator support assemblies  170  and  172  is configured to be coupled to generator frame  28  such that generator frame  28  is cantilevered from first and second generator support assemblies  170  and  172 . 
     In the exemplary embodiment, transition portion  81  includes an arcuate outer surface  176  that transitions from upper portion  78  to lower portion  80 . Transition portion outer surface  176  is substantially smooth and does not include connection joints, such as for example, a bolted connection and/or a welded connection, such that such that support frame  16  is formed as a single, or unitary, component. 
       FIG. 5  is a flow chart illustrating an exemplary method  200  for fabricating support frame  16 . In the exemplary embodiment, method  200  includes forming  202  a molding assembly including a cavity having a shape substantially similar to support frame  16  such that support frame  16  includes upper portion  78  and lower portion  80  extending from upper portion  78 . Upper portion is formed to include at least one bearing housing  86  sized to receive rotor shaft  26  therethrough. Lower portion is formed to include support flange  118  configured to be coupled to tower  12  such that support frame  16  is supported from tower  12 . A metal alloy is deposited  204  within the cavity to integrally form support frame  16  including upper portion  78  and lower portion  80 . In the exemplary embodiment, the molding assembly is formed  206  to include upper portion  78  including forward bearing housing  96  and aft bearing housing  98  such that aft bearing housing  98  is positioned distance  100  from forward bearing housing  96 . The molding assembly is further formed  208  to include lower portion  80  including sidewall  76  extending outwardly from support flange  118  such that sidewall  76  includes first support member  140  and second support member  142  that is opposite first support member  140 . Each first and second support members  140  and  142  are configured to support gearbox  20 . The molding assembly is further formed  210  to include lower portion  80  including generator support assembly  160  such that generator support assembly  160  extends outwardly from support flange  118  and is configured to support generator  22  from support frame  16 . 
     In one embodiment, support frame  16  is formed using sand casting. In such an embodiment, during fabrication of support frame  16 , the molding assembly includes a plurality of mold sections. A first pattern assembly is formed having a shape substantially similar to upper portion  78 . The first pattern assembly is formed including wood, plastic, ceramic, and/or any suitable material to enable the first pattern assembly to function as described herein. A flask is coupled to the first pattern assembly such that a cavity is defined therebetween. A mixture of sand and resin is injected into the cavity and compressed to form an upper portion mold having a shape substantially similar to upper portion  78 . After the mold has been set, the upper portion mold is coupled to a gating system and the first pattern assembly is removed. A second pattern assembly is formed having a shape substantially similar to lower portion  80 . A flask is coupled to the second pattern assembly such that a cavity is defined therebetween. The sand/resin mixture is deposited within the cavity and compressed to form a lower portion mold having a shape substantially similar to lower portion  80 . After the mold has been set, a gating system is coupled to the lower portion mold and the second pattern assembly is removed. Upper portion mold and lower portion mold are coupled together to form the molding assembly that defines a cavity including a shape that is substantially similar to support frame  16  including upper and lower portions  78  and  80 . The gating system is configured to inject a metal alloy into the cavity. The metal alloy is deposited into the cavity through the gating system and is cooled to form a unitary support frame casting. After the metal alloy has been cooled, the upper and lower molds are removed and the casting is machined to form a unitary support frame  16 . 
     The orientation and position of upper and lower portions  78  and  80  of support frame  16  is selected to facilitate supporting rotor  24 , gearbox  20 , generator  22 , and nacelle  18  from a unitary component. By fabricating support frame  16  as a unitary component, support frame  16  provides an increased stiffness and structural integrity over known bedplate frames by eliminating bolted and/or welded connections between bedplate sections. In addition, by providing a unitary support frame  16  to support the components of wind turbine  10 , the cost of repairing damaged wind turbine components is significantly reduced as compared to known wind turbines because failures caused by structural fatigue of the bolted and/or welded connections is reduced. 
     The embodiments described herein overcome at least some disadvantages of known wind turbines by providing a support frame formed as a unitary component. More specifically, the support frame described herein includes a upper portion that includes a bearing housing configured to support a rotor shaft, and a lower portion formed integrally with the upper portion and including a support flange configured to support the support frame from a wind turbine tower. The unitary support frame provides an increased stiffness and structural integrity over known bedplate frames by eliminating the need for bolted and/or welded sections that increase the overall weight of known bedplate frames and increase areas that are subject to stress and fatigue. In addition, by providing a support frame that is a unitary component, the cost of manufacturing and assembling the support frame is facilitated to be reduced. 
     The above-described systems and methods overcome at least some disadvantages of known wind turbines by providing a support frame formed as a unitary component. More specifically, the support frame described herein includes a upper portion that includes a bearing housing to support a rotor shaft, and a lower portion that includes a support flange to support the support frame from a wind turbine tower. By providing a support frame including a unitary component, the rotor, gearbox, generator, and nacelle are supported from a support frame that does not include a plurality of jointed sections that are subject to fatigue during operation of the wind turbine that may cause damage to the rotor, gearbox, generator, and/or nacelle. In addition, by providing a support frame that is a unitary component, the cost and manpower required to manufacture and assemble the support frame is significantly reduced. Reducing such costs extends the operational life expectancies of wind turbine systems. 
     Exemplary embodiments of systems and methods for fabricating a support frame for use in a wind turbine are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the assemblies 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 wind turbine components, and are not limited to practice with only the wind turbine components as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other wind turbine applications. 
     Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     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 have 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 language of the claims.