Abstract:
The present invention relates to a wind turbine nacelle. This nacelle comprises a body, and a head. The body comprises a base which is designed to be fastened to the upper end of a wind turbine tower, and a tubular chamber which upwardly extends said base along a vertical axis. The head comprises a cavity which is designed for rotationally mounting blades and for accommodating a generator, and by a shroud which is secured to the cavity and arranged along a vertical axis so as to be pivotally mounted on the tubular chamber. Furthermore, the nacelle comprises pivot connection means which are arranged between the shroud and the tubular chamber and allow the head to be pivotally mounted on the body. Another aspect of the present invention concerns a wind turbine equipped with such a wind turbine nacelle.

Description:
This is a 371 national phase application of PCT/FR2009/050501 filed 24 Mar. 2009, claiming priority to French patent application Ser. No. 08/51914 filed 26 Mar. 2008, the contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a wind turbine nacelle. It thus relates more particularly to the field of wind turbines. 
     BACKGROUND OF THE INVENTION 
     Application of the invention lies with providers and operators of renewable energy and with installers of wind farms whether on dry land or off-shore. 
     The wind turbine nacelle of the invention is made by wind turbine manufacturers, or more generally by metal workers and/or mechanical welding businesses. 
     A wind turbine comprises in particular a tower, often also called a mast, a nacelle arranged at the top end of the tower, blades, and an alternator, said blades serving, under drive from the wind, to drive the rotor of the alternator in order to generate electricity. The blades and the alternator are arranged on the nacelle, which also includes other component elements of the wind turbine, in particular a system for braking the blades, and speed-increasing gearing. 
     Amongst wind turbines, there are upwind turbines; upwind turbines are constituted by blades located in a plane that is more or less vertical and designed to be exposed to face the oncoming wind directly. For this purpose, the wind turbine is fitted with an anemometer for monitoring the direction of the wind and a system for steering the nacelle that enables the direction in which the blades face to be modified depending on the measurements performed by the anemometer. 
     In the known prior art, the nacelle comprises a base and a head secured to the base. The head includes the alternator and the other component elements of the wind turbine, as mentioned above. In addition, it rotatably receives a hub that is secured to the rotor of the alternator and on which the blades are distributed. 
     The base is also mounted to pivot on the top end of the tower. This pivot mounting is achieved by means of a bearing laid flat on the top end of the tower, which bearing receives said base of the nacelle. By way of example, the bearing may be of the type comprising a ball slewing ring capable of supporting the combined loads exerted by the nacelle resting on the top end of the tower. This stewing ring allows the nacelle to pivot about a vertical axis corresponding to the vertical axis of the tower. 
     Furthermore, the system for steering a nacelle on the tower is arranged between the top end of said tower and the base of the nacelle, which nacelle incorporates the component elements of the steering system. 
     Such a design of wind turbine suffers from the drawback of requiring both the base of the nacelle and the top end of the tower that is to receive the ring to present excellent planeness so as to be able to receive between them the ball slewing ring. 
     In the known prior art, document WO 2007/125349 discloses a wind turbine having a nacelle mounted at the top end of a tower. The nacelle comprises a body and a head. The body has a conical top end that is extended upwards by a tubular chamber, said body being received via rolling bearings in a reception zone that is of shape complementary to said body and that is arranged at the end of the tower. The head comprises firstly a dish that enables blades to be mounted to rotate about an axis that is more or less horizontal and that serves to receive an alternator, and secondly a shaft that extends downwards and that is received in the tubular chamber of the body. A pivot connection constituted by the bearing is arranged between said shaft and said tubular chamber. Such a design presents the drawbacks of requiring the use of a tower that is designed specifically to receive such as nacelle. Such a design also increases the cost of making the tower so that it can receive the nacelle. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to mitigate those drawbacks. It is capable of accommodating the cantilevered-out loading that results from the weight of the upwind alternator while also enabling conventional towers to be used, and without increasing the cost of building such towers. The nacelle design of the present invention also presents the advantages of reducing the cost of fabrication and of enabling it to be installed on existing wind turbines as a replacement nacelle, the nacelle of the present invention being very easily fitted to various types of tower by clamping means. 
     In this respect, the invention relates to a wind turbine nacelle arranged to be assembled on the top end of a tower and to support the component elements of said wind turbine, in particular an alternator and blades mounted to rotate and driving the rotor of the alternator. 
     The nacelle comprises a body constituted by a base suitable for being fastened to the top end of the tower. In addition, the base also includes a tubular chamber extending said base upwards along a vertical axis. 
     The nacelle also has a head constituted by a dish and a bushing. The dish is arranged for mounting the blades to rotate about a defined axis that is more or less horizontal and for receiving the alternator. The bushing is secured to the dish and is arranged about a vertical axis for pivotally mounted on the tubular chamber of the body. 
     In addition, the nacelle includes pivot connection means arranged between the bushing and the tubular chamber, these pivot connection means enabling the head to be pivotally mounted on the body. 
     Such a design makes it possible to avoid the drawbacks of prior art nacelles, in particular implementing a tower presenting excellent planeness at its end for the purpose of receiving said nacelle. In addition, it can be fitted to any traditional type of tower merely by fastening the nacelle to the end of said tower. 
     Furthermore, the nacelle design of the invention presents the advantage of enabling forces to be shared directly over the nacelle between the bushing and the tubular chamber. 
     Another aspect of the present invention provides a wind turbine comprising a tower extending vertically, a wind turbine nacelle of the invention, blades, and an alternator arranged in the dish of the head, with the base of the body being fastened on the top end of the tower. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The characteristics and advantages of the present invention appear on reading the following description of a preferred design of the nacelle, the description making reference to figures, in which: 
         FIG. 1  is a perspective view of a first design of the wind turbine nacelle of the invention; 
         FIG. 2  is a section view of the component elements of the  FIG. 1  nacelle; 
         FIG. 3  shows a wind turbine fitted with the  FIG. 1  nacelle; 
         FIG. 4  is a perspective view, partially in section, showing a variant design of the nacelle of the invention; 
         FIG. 5  is a rear section view of the  FIG. 4  nacelle; and 
         FIGS. 6 and 7  are two projections showing details VI and VII of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , the wind turbine nacelle  1  of the invention comprises a body  3  and a head  5 . The body is constituted by a base  7  and a tubular chamber  9  extending upwards along a vertical axis X 1  of said base  7 . The head  5  is constituted by a dish  11  and a bushing  13 . The bushing  13  is secured to the dish  11 , said bushing being arranged on a vertical axis so as to be pivotally mounted on the tubular chamber  9  of the body  3 . For this purpose, the bushing  13  has an inside diameter D 1  and the tubular chamber has an outside diameter D 2 , with the inside diameter D 1  being greater than the outside diameter D 2 , thereby enabling the bushing to be engaged on the tubular chamber. 
     In addition, the nacelle has pivot connection means arranged between the bushing  13  and the tubular chamber  9 , the pivot connection means enabling the head  5  to be pivotally mounted on the body  3 . 
     These pivot connection means are constituted by two bearings  15 ,  17  arranged between the inside diameter D 1  of the bushing  13  and the outside diameter D 2  of the tubular chamber  9 . These two bearings  15 ,  17  are designed to support the radial loads exerted by the bushing on the tubular chamber. Such radial loads arise, amongst other reasons, as a result of the blades of wind turbine rotating, and as a result of the thrust exerted by the wind on said blades. 
     These bearings  15 ,  17  are arranged on the inside at the top and bottom ends  19  and  21  of the bushing  13 , as can be seen in  FIG. 2 . Furthermore, the bearing  17  arranged at the top end  19  is constituted by a bearing with a brake shoe having the function of slowing down and braking the head  5  of the nacelle relative to the body  3  during turning thereof. In addition, the bearing  15  arranged at the bottom end  21  is constituted by a rolling bearing suitable for transferring both radial and axial loads. The arrangement of the bearings at the top and bottom ends of the bushing  13  serves to optimize the distribution of loads. In preferred manner, the rolling bearing  15  is constituted by a bearing having balls or conical rollers. Furthermore, it is possible to envisage interchanging the bearings  15 ,  17 . 
     As shown in  FIGS. 1 and 2 , the nacelle  1  has a steering system enabling the head  5  to be turned relative to the body  3 . This steering system is arranged between the base  7  of the body and the bottom end of the bushing  13 . It preferably comprises two motors  23 ,  25  symmetrically distributed on the base  7 , as shown in  FIG. 2 . These motors  23 ,  25  are preferably incorporated in part inside the base  7 . These motors  23 ,  25  mesh with an external ring gear  27  arranged at the bottom end of the bushing  13 . Nevertheless, it is possible to envisage having a single motor  26 , as shown in  FIG. 3 , arranged inside the tubular chamber  9  and meshing with an internal ring gear  28  arranged on the bushing  13 . It is also possible for the number is of motors to be greater than two, depending on the dimensions and the power of the wind turbine; under such circumstances, the motors are distributed uniformly around the bushing  3 . 
     In preferred and non-limiting manner, the base  7  of the body  3  has a corolla or domed shape. Similarly, the dish  11  of the head  5  has a corolla or domed shape. This domed-bottom shape serves in particular to make it easier to incorporate the component elements of the wind turbine, as described below. 
     In addition, the head  5  has reinforcing parts  29  arranged between the dish  11  and the bushing  13 , as shown in  FIGS. 1 and 2 . These reinforcing parts  29  are distributed uniformly on either side of the bushing and they are welded between the outside face of the bushing and the rear face  31  of the dish  11 . Such reinforcing parts serve to reinforce the structure of said head  5 , which is subjected to high levels of stress during rotation of the blades of the wind turbine. 
     As shown in  FIGS. 1 to 3 , the tubular chamber  9  of the body  3  includes a slot  33 . Similarly, the bushing  13  includes a slot  35  of shape and position that are substantially identical to the shape and position of the slot in the tubular chamber  9 . Thus, during turning of the bushing  13  on the tubular chamber  9 , the two slots  33  and  35  can come into coincidence with each other, thereby having a function of providing access to the inside  37  of the tubular chamber, which may contain component elements of the wind turbine, such as the motors of the steering system, and electrical cabinets, or a controller for controlling said elements of the wind turbine. 
     In preferred and non-limiting manner, the common portion of the rear face  31  of the dish  11  in contact with the bushing  13  has an opening  38 , shown in  FIGS. 1 and 2 , giving access to the inside of said dish  11  from inside said bushing  13  for maintenance operations on the alternator and on the hub supporting the blades of the wind turbine, which elements are described below. An operator penetrates initially into the inside  37  of the tubular chamber  9  as mentioned above; then, for example, by turning the head  5  through half a turn relative to the body  3 , the slot  33  of the tubular chamber  9  is made to coincide with the opening  38  leading to the dish  11 , thereby enabling said operator situated inside the tubular chamber  9  to access said opening  38 . 
     In addition, the nacelle preferably includes a ladder installed on the inside  37  of the tubular chamber  9  to give access to a top level, as described above, by passing through the top end of said tubular chamber  9 . 
     The nacelle includes a cabin  39 , shown in  FIG. 3 , this cabin being secured to the bushing  13  and being located opposite from the dish  11 , also fastened to the bushing  13 . The cabin  39  communicates with the slot in the bushing. It also has the function of receiving component elements of the wind turbine and of giving people access, in particular for maintenance operations. The cabin  39  preferably includes a bottom floor  40   a  and a top floor  40   b , shown in  FIG. 3 . By way of example, the bottom floor  40   a  is arranged level with the bottom end of the bushing  13 . By way of example, the top floor  40   b  is arranged level with the top end of the tubular chamber and it is provided with an opening communicating with said top end of the tubular chamber so as to give access to the inside  37  thereof. 
       FIG. 3  shows a wind turbine  41  constituted by a nacelle  1  of the invention. The wind turbine has a tower  43 , also known as a mast, that extends vertically, with the height of the tower depending essentially on the power of the wind turbine and of the blades arranged thereon. 
     On this topic,  FIG. 3  shows the blades  45 , preferably three in number, that are arranged on a hub  47  presenting a streamlined nose. The wind turbine has an alternator  49  serving to generate alternating current (AC). The alternator is incorporated inside the hub  47  and it is fastened inside the dish  11  of the head  5  of the nacelle so as to move in rotation therewith, as shown in  FIG. 3 . 
     Furthermore, the hub  47  is secured to the rotor of the alternator  49 , with rotation of the blades and of the hub as generated by the action of the wind serving to drive rotation of the alternator rotor and generate electricity. The diameter of the dish  11  is thus dimensioned as a function of the diameter of the alternator  49  and of the diameter of the elements of the hub  47 , depending on the elements that said dish supports and depending on the design of the alternator. In this respect, it is preferable to select an alternator made up of an external rotor that surrounds the stator symmetrically. The way the hub supporting the blades is assembled with the alternator on the dish enables these elements to be mounted to rotate about a defined axis that is more or less horizontal. 
     The base  7  of the body  3  presents a diameter at its end that corresponds to the diameter of the top end  51  of the tower  43 . This base rests on the top end of the tower and it is fastened thereto. In preferred and non-limiting manner, this fastening is provided by clamping together flanges  53  of these two elements. 
     The wind turbine  1  includes other elements, that are also to be found in wind turbines of the prior art, in particular an anemometer  55  mounted on the cabin  39  that is arranged on the nacelle  1 , as described above. The anemometer is mounted on the top rear portion of said cabin  39 . The anemometer  55  serves to measure the wind and its direction. The anemometer is connected to a controller  57  that, amongst other things, controls the steering system by acting on the motors to turn the head  5  relative to the body  3  so as to change the position of the blades  45  and place them facing the wind. Other elements or accessories are included in the cabin  39 , such as power converters and cooling units  58 . By way of example, these various elements or accessories are arranged on the bottom and top floors  40   a  and  40   b  or on the inside walls  59 ,  60  of said cabin  39 . 
     It can be understood that fastening the base of the nacelle on the top end of the tower makes it possible to avoid the needs for planeness as required in the past on prior art wind turbine towers where it is the base that is movable relative to said tower. 
     Furthermore, the technical characteristics described for the design of the nacelle  1  and the wind turbine  41  fitted with such a nacelle  1 , as shown in  FIGS. 1 to 3 , remain applicable to all variants of that design, without going beyond the ambit of the present invention. 
     Other variants may also be envisaged without going beyond the ambit of the invention. Thus,  FIGS. 4 to 7  show a variant nacelle  101  in which the body  103  comprises firstly a base  107  of circular shape that preferably extends inwards in a horizontal plane as shown in  FIGS. 5 to 7 , said base  107  being arranged to be clamped to the top end of the tower of a wind turbine similar to that shown in  FIG. 3 , and secondly a tubular chamber  109  extending upwards from the base  107  with its top end receiving an internal ring gear  127 , as shown in  FIGS. 5 and 6 . In addition, the head  105  of the nacelle  101  includes a dish  111  and a bushing  113  with reinforcement  129  provided therebetween. The bushing  113  is subdivided into two compartments, namely a bottom compartment  113   a  and a top compartment  113   b . The tubular chamber  109  is engaged in the bottom compartment  113   a , with pivot connection means being arranged between the bottom compartment  113   a  of the bushing and the tubular chamber  109 . 
     In preferred manner, in this variant nacelle  101 , three motors  123 ,  124 , and  125  are distributed uniformly and engage the internal ring  127 , as shown in  FIGS. 4 to 6 , together constituting a system for steering the head  105  relative to the body  103 . These motors  123 ,  124 , and  125  are housed in the top compartment  113   b  of the bushing  113 , as shown in  FIG. 4 , and they are mounted directly on the separator wall  113   c  separating the bottom compartment  113   a  and the top compartment  113   b.    
     Furthermore, in this variant nacelle  101 , the dish  111  has an opening  138 , as shown in  FIGS. 4 and 5 , communicating with the top compartment  113   b  of the bushing  113 , thereby giving to the inside of said dish  111 . In order to facilitate access via the opening  138  to the elements of the alternator of the wind turbine, the top end  161  of the top compartment  113   b  of the bushing  113  presents a chamfered shape in section, as can be seen in  FIGS. 4 and 5 . In addition, the separation wall  113   c  between the bottom compartment  113   a  and the top compartment  113   b  includes an opening  162 , shown in  FIG. 5 , giving access to said bottom compartment  113   a , in particular for maintenance operations on the internal ring  127  and the pinions of the motors  123 ,  124 , and  125  meshing with said internal ring gear  127 . 
     In this variant embodiment of the nacelle  101 , the pivot connection means between the tubular chamber  109  and the bottom compartment  113   a  of the bushing  113  are provided by bearings  115 ,  117  arranged between the inside diameter of the bottom compartment  113   a  of the bushing  113  and the outside diameter of the tubular chamber  109  level with the top and bottom ends  119  and  121  of said bottom compartment  113   a , as shown in  FIGS. 4 to 7 . These bearings  115 ,  117  are constituted by shoes  115   n ,  117   n  shown in detail in  FIGS. 6 and 7  that are distributed uniformly around the bushing level with the top and bottom ends  119  and  121 , as shown in  FIG. 4 . Each bearing  115  and  117  is preferably constituted by eight shoes  115   n ,  117   n  that are uniformly distributed. 
     Likewise, as shown in  FIG. 6 , shoes  116   n  similar to the shoes  115   n ,  117   n  are also provided; these shoes  116   n  are secured to the separator wall  113   c  and they bear against the top end of the tubular chamber  109  either directly or indirectly via the internal ring gear  127 , said shoes  116   n  then bearing against the top face  167  of said internal ring gear  127 . These shoes  116   n  are preferably eight in number and uniformly distributed around the separator wall  113   c  of the bushing  113 , as shown in  FIG. 4 . Thus, the bushing  113  of the head  105  rests on the tubular chamber  109  of the body  103 . 
     Preferably, such shoes  115   n ,  116   n , and  117   n  are of the trademark Eternum®. Furthermore, such shoes  115   n ,  116   n , and  117   n  may be envisaged for the nacelle  1  shown in  FIGS. 1 to 3 . 
     Such a pivot connection presents the advantage of avoiding the use of rolling bushings, which are expensive, and ensures long life for the pivot connection implemented between the bushing  113  and the tubular chamber  109 . 
     In this variant nacelle  101 , a braking system is arranged between the separator wall  113   c  of the bushing  113  and the top end of the tubular chamber  109 . The braking system is preferably constituted by a brake caliper  168   a ,  168   b  secured to the bottom face  166  of the separator wall  113   c  and a brake disk  169  secured to the top end of the tubular chamber  109 , as shown in  FIGS. 5 and 6 . It is nevertheless possible for other embodiments to be envisaged for the braking system between the bushing  113  and the tubular chamber  109 . 
     Naturally, the nacelle  101  shown in  FIG. 4  has a cabin secured to the bushing  113  and may be installed on the wind turbine  47  as shown in  FIG. 3 .