Abstract:
A method and apparatus of assembling a rotary machine includes providing at least one component. The component is at least one of a rotating member and a stationary member. The method and apparatus also includes coupling the component to a monocoque nacelle structure. The monocoque nacelle structure includes an outer shell that extends over at least a portion of the component.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to rotary machines and more particularly, to methods and apparatus for assembling and operating wind turbine nacelles. 
   At least some known wind turbine generators (“wind turbines”) include a rotor having multiple blades. The blades are coupled to a rotatable hub to facilitate transforming mechanical wind energy into a mechanical rotational torque that drives one or more generators. Although some known wind turbines include gearless direct drive generators, known wind turbines generally include generators that are rotationally coupled to the rotor through a gearbox. The gearbox facilitates increasing an inherently low rotational speed of the turbine rotor. The generator uses the rotational speed to facilitate efficiently converting the rotational mechanical energy to electrical energy, which is fed into a utility grid. 
   In known wind turbines including a gearbox, the rotor, generator, gearbox and other wind turbine components are typically mounted on a load-bearing bed frame within a housing, or nacelle that is positioned on top of a base that may be a truss or tubular tower. Because the wind turbine components are mounted on the load-bearing bed frame, an outer shell or external skin of the nacelle serves as a non-load bearing protective skin that may be formed as a heavy casting. Therefore, some known nacelle configurations introduce substantial weight at the top of the wind turbine tower to facilitate supporting the wind turbine components positioned within. Further, any associated component supporting features of some known nacelles also facilitate increasing weight at the top of the wind turbine tower. As a result of increased weight, some known nacelles facilitate increasing capital and operational costs of the wind turbine. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method for assembling a rotary machine is provided. The method includes providing at least one component. The component is at least one of a rotating member and a stationary member. The method also includes coupling the component to a monocoque nacelle structure. The monocoque nacelle structure includes an outer shell that extends over at least a portion of the component. 
   In another aspect, a wind turbine generator is provided. The wind turbine generator includes at least one component. The component includes at least one of a rotating member and a stationary member. The wind turbine generator also includes a monocoque nacelle structure coupled to the component. The monocoque nacelle structure includes an outer shell extending over at least a portion of the component. 
   In a further aspect, a monocoque nacelle for a rotary machine is provided. The monocoque structure includes at least one component. The component includes at least one of a rotating member and a stationary member. The monocoque nacelle also includes an outer shell coupled to the component. The outer shell extends over at least a portion of the component. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of an exemplary wind turbine generator including a nacelle; 
       FIG. 2  is a fragmentary cross-sectional axially skewed schematic view of an outer shell of a monocoque nacelle shown in  FIG. 1 ; 
       FIG. 3  is an enlarged fragmentary cross-sectional schematic view of an alternative stamped mounting portion that can be formed into the outer shell shown in  FIG. 2 ; 
       FIG. 4  is an enlarged fragmentary schematic view of another alternative stamped mounting portion that can be formed into the outer shell shown in  FIG. 2 ; and 
       FIG. 5  is an enlarged fragmentary schematic view of further alternative stamped mounting portions that may be formed into and used with the outer shell shown in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The exemplary methods and apparatus described herein overcome the structural disadvantages of known nacelles by providing a monocoque nacelle structure. It should be appreciated that “monocoque” is used throughout this application to refer to a structure that is configured to use a thin outer shell, or external skin, to support a substantial portion of the overall mechanical weight and stress loading of components coupled thereon. More specifically, it should be appreciated that “monocoque nacelle” is used throughout this application to refer to a nacelle structure that is configured to use an outer shell, or external skin, to support a substantial portion of the overall mechanical weight and stress loading of wind turbine components coupled thereon. In one exemplary embodiment, the outer shell is a thin outer shell with little to no internal support features such as, but not limited to, a load-bearing bed frame positioned within the shell. 
     FIG. 1  is a schematic illustration of an exemplary wind turbine generator  100 . In the exemplary embodiment, wind turbine generator (“wind turbine”)  100  is a horizontal axis wind turbine. Alternatively, wind turbine  100  may be a vertical axis wind turbine. Wind turbine  100  includes a tower  102  erected on a supporting surface  104 , a monocoque nacelle  106  coupled to tower  102 , and a rotor  108  coupled to nacelle  106 . Rotor  108  includes a rotatable hub  110  and a plurality of rotor blades  112  coupled to hub  110 . In the exemplary embodiment, tower  102  is fabricated from tubular steel and includes a cavity (not shown) extending between supporting surface  104  and nacelle  106 . In an alternative embodiment, tower  102  is a lattice tower. The height of tower  102  is selected based upon factors and conditions known in the art. In the exemplary embodiment, rotor  108  includes three rotor blades  112 . In an alternative embodiment, rotor  108  may include more or less than three rotor blades  112 . 
   In the exemplary embodiment, blades  112  have a length between 50 meters (m) (164 feet (ft)) and 100 m (328 ft). Alternatively, blades  112  may have any length. Blades  112  are connected to rotor hub  110  to facilitate rotating rotor  108  about a central rotational axis  114  to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, electrical energy. More specifically, blades  112  are mated to hub  110  by coupling a blade root portion  116  of each blade  112  to a plurality of load transfer regions  118  on hub  110 . Load transfer regions  118  include a hub load transfer region (not shown) and a blade load transfer region (not shown). Loads generated by blades  112  are transferred to hub  110  via load transfer regions  118 . 
   During operation of wind turbine  100 , wind strikes blades  112  to facilitate rotation of blades  112 . As blades  112  are rotated, blades  112  are subjected to centrifugal forces, various bending moments, and/or other operational stresses. As such, blades  112  may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position. Therefore, blades  112  may be subjected to associated stresses and/or loads. Moreover, a pitch angle of blades  112 , i.e., the angle that determines a perspective of blades  112  with respect to the direction of the wind, may be changed by a pitch adjustment mechanism (not shown) that rotates the blades about a pitch axis  120 . Specifically, the pitch adjustment mechanism facilitates increasing or decreasing blade  112  speed by adjusting the surface area of blades  112  exposed to wind force vectors. In the exemplary embodiment, the pitches of blades  112  are controlled individually. Alternatively, the pitch of blades  112  may be controlled as a group. 
   In some configurations, one or more microcontrollers in a control system (not shown) are used for overall system monitoring and control including pitch and rotor speed regulation, yaw drive and yaw brake application, and fault monitoring. Alternatively, distributed or centralized control architectures are used in alternate embodiments of wind turbine  100 . 
     FIG. 2  is a fragmentary cross-sectional axially skewed schematic view of an outer shell  200  of monocoque nacelle  106  (shown in  FIG. 1 ). More specifically, in the exemplary embodiment, outer shell  200  is a thin, load-bearing shell that includes an outer surface  202 , an inner surface  204 , and a stamped mounting portion  210 . 
   Outer shell  200  is fabricated from sheets of sturdy, light-weight material such as, but not limited to, aluminum alloys, fiber-reinforced composites or any other materials that facilitate attaining predetermined operational parameters. Operational parameters include, but are not limited to, facilitation of mitigating weight loads at the top of tower  102  (shown in  FIG. 1 ), providing sufficient material strength to withstand local environmental conditions, and collecting and distributing weight and stress loadings from wind turbine components positioned within nacelle  106 . 
   In the exemplary embodiment, the sheets of material are assembled to form outer shell  200  via retention hardware methods that include, but are not limited to, riveting and bolting. Alternatively, welding methods are used to couple the sheets of material. In a further alternative, outer shell  200  is fabricated, cast or forged as a unitary member that adheres to the aforementioned operational parameters. 
   Prior to assembly of outer shell  200 , at least one sheet of material forming outer shell  200  is stamped to form mounting portion  210  therein such that concave/convex portions of outer surface  202  conform to respective concave/convex portions of inner surface  204 . Mounting portion  210  includes an inwardly protruding channel  212  that is defined by a first wall  214 , a second wall  216 , and an intermediate wall  218  positioned therebetween. First wall  214  and second wall  216  are substantially parallel walls that are perpendicular to and project inward towards central rotational axis  114 . In the exemplary embodiment, channel  212  is circumferentially arranged about central rotational axis  114 . Alternatively, channel  212  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   Mounting portion  210  also includes a plurality of spaced projections  220  defined within channel  212 . More specifically, projections  220  protrude outwardly from intermediate wall  218  of channel  212 . Each projection  220  includes a recessed cavity  222  opening towards central rotational axis  114 . It should be appreciated that projections  220  may vary in size, shape, and/or orientation without departing from the scope of the present application. As a result of stamped mounting portion  210 , numerous wind turbine components positioned within outer shell  200  are directly coupled to outer shell  200  via mounting portion  210 . 
   For example, as illustrated in  FIG. 2 , a bearing  224  is directly coupled to intermediate wall  218  along a central co-axial circumferential axis  226  of bearing  224  and intermediate wall  218 . Alternatively, other wind turbine components may be directly coupled to outer shell  200  by, for example, welding methods and/or inserting a plurality of fasteners  228  through openings  230  defined in mounting portions such as, but not limited to, first wall  214 , second wall  216 , projections  220 , and/or other portions of outer shell  200 . As a result, mounting portion  210  facilitates easier assembly, less wear, and/or more simple repair as compared to known nacelle structures because rivets and fasteners can be easily inserted and/or removed to mount and/or replace wind turbine components provided within outer shell  200 . 
   In the exemplary embodiment, outer shell  200  of monocoque nacelle  106  is fabricated from thinner sheets of work hardened metals as compared to outer shells of known nacelles including semi-monocoque nacelles. Such work hardened metals may include, but are not limited to, certain types of aluminum with an “H” suffix. More specifically, stamping work hardened materials facilitates increasing the strength of sheet materials as compared to sheet materials that are not stamped. Therefore, the portion of outer shell  200  that includes stamped mounting portion  210  therein is stronger as compared to portions of outer shell  200  that do not include mounting portion  210 . For example, fatigue in stamped mounting portion  210  is more evenly distributed and thus causes less damage in stamped mounting portion  210  than in a non-stamped portion of outer shell  200 . Therefore, mounting portion  210  includes a torsional rigidity that facilitates reduced twisting of outer shell  200 . As a result, internal wind turbine components can operate more efficiently. 
   Moreover, mounting portion  210  facilitates directly disseminating stresses and loads of mounted wind turbine components into outer shell  200 , and such wind turbine components may be directly mounted to outer shell  200 . As set forth in the exemplary embodiment, monocoque nacelle  106  facilitates reducing vibration stresses and reducing a number of structural members required for strength and rigidity to support such stresses and loads without the assistance of additional internal support members and/or load-bearing support frames. In addition, outer shell  200  is a high-energy absorption body including strong mounting portion  210 , and accordingly, monocoque nacelle  106  does not require an internal framework for structural strength, mounting wind turbine components therein, and/or transferring loads of such wind turbine components. As such, in the exemplary embodiment, monocoque nacelle  106  does not include a load-bearing bed frame. 
   Mounting portion  210  also facilitates fabricating nacelle  106  from thinner sheets of material as compared to known nacelle structures, such as semi-monocoque nacelle structures. More specifically, instead of providing thicker sheets of material for mounting strength and/or rigidity, thinner sheets of material may be stamped to form stamped mounting portion  210  at various locations in outer shell  200  where component mounting strength and/or rigidity are desirable. As such, mounting strength and/or rigidity is facilitated by providing thinner, lighter weight materials including bent/stamped mounting portions. 
   Although monocoque nacelle  106  is fabricated from thinner sheets of material, monocoque nacelle  106  facilitates absorbing deflections and vibrations experienced by outer shell  200  and facilitates protecting wind turbine components positioned within outer shell  200 . Because thinner sheets of material are generally lighter in weight as compared to thicker sheets of a same material, monocoque nacelle  106  also facilitates reducing weight and material costs as compared to at least some known nacelles. Therefore, monocoque nacelle  106  is generally stronger, lighter, more durable, and more load and stress absorbing as compared to at least some known nacelles. 
   In the exemplary embodiment, at least one sheet of material forming outer shell  200  is stamped to form a plurality of outwardly projecting dimples  232  therein such that concave/convex portions of outer surface  202  conform to respective concave/convex portions of inner surface  204 . Each outwardly projecting dimple  232  forms a recessed cavity  234  extending away from central rotational axis  114 . At least one sheet of material forming outer shell  200  is also stamped to form a plurality of inwardly projecting dimples  236  therein such that concave/convex portions of outer surface  202  conform to respective concave/convex portions of inner surface  204 . Each inwardly projecting dimple  236  includes a recessed cavity  238  extending toward central rotational axis  114 . It should be appreciated that dimples  232  and  236  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   As discussed above, at least one sheet of material forming outer shell  200  is stamped to form dimples  232  and  236 , mounting portion  210 , and/or projections  220 . As a result, dimples  232  and  236 , mounting portion  210 , and/or projections  220  may provide additional surface area for outer shell  200 . Therefore, at least some stamped portions of outer shell  200  may facilitate conduction of cooling air/wind for cooling wind turbine components positioned within outer shell  200 . 
     FIG. 3  is an enlarged fragmentary schematic view of an alternative stamped mounting portion  300  that can be formed into outer shell  200  (shown in  FIG. 2 ). Prior to assembly of outer shell  200 , at least one sheet of material forming outer shell  200  is stamped to form mounting portion  300  therein such that concave/convex portions of outer surface  202  conform to concave/convex portions of inner surface  204 . Mounting portion  300  includes a channel  302  that is defined by an inwardly protruding spine  304  and a plurality of inwardly protruding rib portions  306  extending therefrom. In the exemplary embodiment, channel  302  is circumferentially arranged about central rotational axis  114 . Alternatively, channel  302  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   As a result of stamped mounting portion  300 , numerous wind turbine components positioned within outer shell  200  are directly coupled to outer shell  200  via mounting portion  300 . For example, wind turbine components are directly coupled to outer shell  200  by, for example, welding methods and/or inserting a plurality of fasteners  308  through openings  310  defined in mounting portion  300  and/or other outer shell  200  portions. As a result, mounting portion  300  facilitates easier assembly, less wear, simpler repair as compared to known nacelle structures because rivets and fasteners can be easily inserted and/or removed to mount and/or replace wind turbine components provided within outer shell  200 . Moreover, stamped mounting portion  300  also facilitates providing the advantages discussed above with respect to increasing strength, disseminating stresses and loads, reducing vibration stresses, reducing a number of structural members, reducing an overall weight, and/or increasing surface area of outer shell  200  as compared to known nacelle structures. 
     FIG. 4  is an enlarged fragmentary schematic view of another alternative stamped mounting portion  400  that can be formed into outer shell  200  (shown in  FIG. 2 ). Prior to assembly of outer shell  200 , at least one sheet forming material forming outer shell  200  is stamped to form mounting portion  400  therein such that concave/convex portions of outer surface  202  conform to concave/convex portions of inner surface  204 . Mounting portion  400  includes a first channel  402  that is defined by a first wall  404  and a substantially parallel second wall  406  that are perpendicular to and project inward towards central rotational axis  114 . In the exemplary embodiment, first channel  402  is circumferentially arranged about central rotational axis  114 . Alternatively, first channel  402  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   Mounting portion  400  also includes a plurality of spaced projections  408  defined within first channel  402 . Each projection  408  includes a recessed cavity  410  opening towards central rotational axis  114 . It should be appreciated that projections  408  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   Mounting portion  400  also includes a plurality of spaced, inwardly protruding v-shaped channels  412  and  414 . V-shaped channel  412  is partially defined by first wall  404  and an obliquely angled third wall  416 . V-shaped channel  414  is partially defined by second wall  406  and an obliquely angled fourth wall  418 . In the exemplary embodiment, v-shaped channels  412  and  414  are disposed on opposite sides of projections  408 . As a result, v-shaped channels  412  and  414  facilitate increasing the stiffness of outer shell  200 . Moreover, v-shaped channels  412  and  414  each include a recessed cavity opening away from central rotational axis  114 . It should be appreciated that v-shaped channels  412  and  414  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   As a result of stamped mounting portion  400 , numerous components positioned within outer shell  200  may be directly coupled to outer shell  200  via mounting portion  400 . For example, in the exemplary embodiment, stacked laminations of a stator core  420  may be directly coupled to first and second walls  404  and  406  along a central co-axial circumferential axis  422  of stator core  420  and first channel  402 . Alternatively, other wind turbine components may be directly coupled to outer shell  200  by, for example, welding methods and/or inserting a plurality of fasteners (not shown) through openings  424  provided in other mounting portions such as, but not limited to, first wall  404 , second wall  406 , projections  408 , and/or other outer shell  200  portions. As a result, mounting portion  400  facilitates easier assembly, less wear, simpler repair as compared to known nacelle structures because rivets and fasteners can be easily inserted and/or removed to mount and/or replace wind turbine components provided within outer shell  200 . Moreover, stamped mounting portion  400  also facilitates providing the advantages discussed above with respect to increasing strength, disseminating stresses and loads, reducing vibration stresses, reducing a number of structural members, reducing an overall weight, and/or increasing surface area of outer shell  200  as compared to known nacelle structures. 
     FIG. 5  is an enlarged fragmentary schematic view of further alternative stamped mounting portions that may be formed into and used with outer shell  200  (shown in  FIG. 2 ). Prior to assembly of outer shell  200 , at least one sheet of material forming outer shell  200  is stamped to form mounting portion  500  such that concave/convex portions of outer surface  202  conform to concave/convex portions of inner surface  204 . Mounting portion  500  includes a channel  502  that is defined by an undulating projection  504  having a first wall  506  and a substantially parallel second wall  508 . In the exemplary embodiment, channel  502  is circumferentially arranged about central rotational axis  114 . Alternatively, channel  502  may vary in size, shape, and/or orientation without departing from the scope of the present application. In the exemplary embodiment, at least one sheet of material forming outer shell  200  is also stamped to form a spaced mounting blister  510 . 
   As a result of stamped mounting portion  500  and/or stamped mounting blister  510 , numerous components positioned within outer shell  200  may be directly coupled to outer shell  200  via mounting portion  500  and/or mounting blister  510 . For example, wind turbine components may be directly coupled to outer shell  200  by, for example, welding methods and/or inserting a plurality of fasteners (not shown) through openings (not shown) defined in mounting portion  500 , mounting blister  510 , and/or other outer shell  200  portions. As a result, mounting portion  500  and/or mounting blister  510  facilitates easier assembly, less wear, simpler repair as compared to known nacelle structures because rivets and fasteners can be easily inserted and/or removed to mount and/or replace wind turbine components provided within outer shell  200 . Moreover, stamped mounting portion  500  and/or mounting blister  510  also facilitates providing the advantages discussed above with respect to increasing strength, disseminating stresses and loads, reducing vibration stresses, reducing a number of structural members, reducing an overall weight, and/or increasing surface area of outer shell  200  as compared to known nacelle structures. 
   After assembly of outer skin  200 , a thicker and stiffer local portion of outer shell  200  may be desirable. In the exemplary embodiment, at least one separate sheet of material is stamped to form an additional nesting mounting portion  520 . Nesting mounting portion  520  includes a channel  522  including a first wall  524  and a spaced, substantially parallel second wall  526 . First and second walls  524  and  526  include outwardly extending flanges  528  and  530 , respectively. Moreover, first and second walls  524  and  526  are joined by an intermediate wall  532  positioned therebetween. Further, intermediate wall  532  includes a plurality of mounting blisters  534  stamped into intermediate wall  532 . It should be appreciated that nesting mounting portion  520  and/or mounting blisters  534  may vary in size, shape, and/or orientation without departing from the scope of the present application. 
   In the exemplary embodiment, nesting mounting portion  520  may be coupled to at least one of outer shell  200  and mounting portion  500  to facilitate reinforcing outer shell  200  locally. For example, nesting mounting portion  520  may be coupled to outer shell  200  via welding methods or providing fasteners (not shown) through openings  536  defined in nesting mounting portion  520  and/or opening defined in portions of outer shell  200 . Subsequently, wind turbine components may be coupled to nesting mounting portion  520  via openings  538  defined in mounting blisters  534  and/or other areas of nesting mounting portion  520 . As a result, outer shell portions may be partially reinforced to facilitate increasing localized material strength capable of withstanding localized environmental conditions. Because nesting mounting portion  520  facilitates increasing strength of stamped outer shell  200  at localized areas when desirable, reducing weight and costs of entire outer shell  200  is still facilitated as compared to some known nacelles. 
   In general, any combination of mounting portions as described herein may be formed into and/or used with outer shell  200  of monocoque nacelle  106  to attain predetermined operational parameters as also described herein. 
   The methods and apparatus for a wind turbine generator nacelle described herein facilitate operation of a wind turbine generator. More specifically, the wind turbine generator monocoque structure as described above facilitates an efficient and effective mechanical load and stress transfer scheme. Also, the lighter weight monocoque nacelle structure facilitates decreased capital construction costs. Such monocoque nacelle structure also facilitates wind turbine generator reliability, and reduced maintenance costs and wind turbine generator outages. 
   Exemplary embodiments of monocoque wind turbine nacelle structures as associated with wind turbine generators are described above in detail. The methods, apparatus and systems are not limited to the specific embodiments described herein nor to the specific illustrated wind turbine generators. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.