Abstract:
A wind turbine electrical-generating system with air-directing vanes in the forms of sheaths over structural members crossing the sir discharge opening of the wind turbines. The turbines also have associated shroud assemblies which support the structural members and which cooperate with the vanes to provide superior performance.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    In order to generate sufficient electrical energy wind turbines must be of substantial diameter and supported for operation on towers at considerable elevations. Obviously, structural supporting members for mounting the turbines on the towers must be of substantial size and strength and their location is in most cases if not all at least partially in the path of the discharge flow from the turbines. With axial flow turbines the discharge flow has a swirling component, which is detrimental to turbine performance, and the interaction of this flow with the supporting structure also results in drag and a further detrimental effect on turbine performance. 
         [0002]    Accordingly, it is the general object of the present invention to provide means for reducing the detrimental effect of structural supporting members in the discharge flow of a wind turbine and at the same time reducing swirling in the discharge flow. 
         [0003]    A further object resides in the provision of the foregoing in combination with a shrouded wind turbine. 
         [0004]    A still further object is to provide the foregoing means in an inexpensive yet highly efficient form. 
       SUMMARY OF THE INVENTION 
       [0005]    Stationary vanes for directing the flow of air or other fluids have long been used in a wide variety of different environments. It is believed, however, that they have not been used in composite form in combination with structural supporting members for wind turbines. 
         [0006]    In accordance with the present invention and in fulfillment of the foregoing objects, at least one axial flow wind turbine is provided together with at least one elongated structural member for supporting the same at elevation on a tower. The supporting member extends in a generally radial outward direction relative to the axis of the turbine and rearwardly of the turbine so as to be in the swirling discharge flow of the turbine. An elongated sheath envelops the structural member and has an airfoil configuration in cross section to both reduce the drag of the structural member and straighten the swirling discharge flow. 
         [0007]    Preferably, the structural member takes the form of a metallic truss comprising interconnecting lateral members extending between a pair of parallel elongated tubular members spaced apart and offset axially to fit within a sheath having an optimum cambered airfoil configuration for straightening the swirling discharge air stream. 
         [0008]    The sheath is preferably of lightweight inexpensive extruded thermoplastic construction and both the sheath and the structural member are designed for relative sliding assembly with each other. The sheath is also somewhat shorter than the structural member to accommodate thermal expansion and may have a single point of attachment with the structural member or may be held in place by friction alone again for accommodation of thermal expansion and contraction. 
         [0009]    In an illustrative embodiment of the invention three (3) wind turbines are mounted in pairs on opposite sides of a supporting tower and each turbine has at least one supporting member and an associated sheath for reducing drag and straightening the air stream discharged from its turbine. The supporting member and sheath extend generally radially but are preferably inclined slightly rearwardly from a precisely radial plane in a more or less cone shaped configuration. An accelerator is also preferably provided and divides approaching wind into a pair of diverging air streams respectively entering and passing through the turbines. 
         [0010]    It should also be noted that shrouded turbines are particularly well suited to combination with the present invention and with the enhanced performance from shrouding taken together with performance gains from sheathing of the present invention superior overall turbine performance is achieved. A synergistic result is thus realized when sheathed structural members and turbines are supported by shroud assemblies with a number of structural members extending radially in a common plane and each connected at opposite ends to a shroud assembly and a hub assembly for the turbine. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a front view in elevation showing a tower supporting three (3) pairs of wind turbines, 
           [0012]      FIG. 2  is an enlarged view of an illustrative wind turbine, hub, shroud and exposed structural member assembly, 
           [0013]      FIG. 3  is an enlarged illustrative view of a wind turbine, hub, shroud and completed vane assembly, 
           [0014]      FIG. 4  is an enlarged cross-sectional view of a structural member and sheath forming a vane assembly, 
           [0015]      FIG. 5  is a perspective view of a sheath and, 
           [0016]      FIG. 6  is a fragmentary view showing a sheath and structural member of a vane assembly. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       [0017]    Referring particularly to  FIG. 1 , a tower partially shown and indicated generally at  10  supports three (3) pairs of wind turbine assemblies  12 ,  12 . As more clearly shown in  FIGS. 2 and 3 , each wind turbine assembly comprises an axial flow wind turbine having five (5) blades  14 ,  14  supported in common on a hub assembly  16 . The hub assembly  16  is supported by four (4) structural members  18 ,  18  which extend generally and, more specifically, in a direction inclined rearwardly from the radial, each with an inner end portion connected with and supported by the hub assembly  16 . At their outer end portions the structural members  18 ,  18  are connected with a shroud assembly indicated generally at  20 . The shroud assembly includes a lattice type structure having upper and lower spaced parallel and horizontal members  22 ,  22  that are supported by the tower  10 . More specifically, the members  22 , 22  extend to and are connected with the structural members, not shown, within an accelerator  24  which are in turn supported by main structural members of the tower  10 . The members  22 ,  22  of the shroud assembly support arcuate members  25 , 25  that in turn mount an arcuate shroud, not shown. Short lateral truss members  26 ,  26  extend between the members  22 ,  22  and members  24 ,  24  and support the outer end portions of the aforesaid radial structural members  18 ,  18 . 
         [0018]    The structural members  18 , 18  preferably take the form of trusses with a pair of elongated spaced apart parallel tubular members  28 ,  28  extending longitudinally and connected by transverse truss members  30 ,  30 ,  FIGS. 2 ,  4 , and  6 . The tubular structural members  28 ,  28  are spaced apart axially as illustrated in  FIG. 4  with the turbine axis depicted by broken line  32 . The members  28 ,  28  are also offset axially as illustrated by the relationship between the axis line  32  and the broken centerline  34  of the tubular members, the lines  32  and  34  being angularly displaced as illustrated at  36  in  FIG. 4 . The structural members  18 ,  18  are of metallic construction, and the specific material may vary but is preferably galvanized steel. 
         [0019]      FIGS. 3 ,  5 , and  6  illustrate an elongated sheath  38  in the shape of an airfoil which forms an air-directing vane of the present invention. As best illustrated in  FIG. 4  the sheath  38  has a number of integral strengthening members which extend throughout its length within its interior cavity together with spaced apart elongated and parallel cylindrical openings  39 , 39  which slidably receive the aforementioned parallel tubular members  28 ,  28 . An open channel  41  extending between the two cylindrical openings  39 , 39  receives the transverse truss members  30 ,  30  of the structural member  18 . The sheath is also provided with a camber, which together with the axial offset of the structural members results in an optimum airfoil configuration. 
         [0020]    As will be apparent, the sheaths  38 , 38  and the structural members  18 ,  18  may be readily assembled in a relative sliding operation. The sheaths  38 ,  38  and structural members  18 ,  18  may be maintained in their assembled relationship merely with the aid of friction or, alternatively, a single point of positive attachment may be provided as with a bolt  40  in  FIG. 5  The bolt  40  penetrates the sheath and connects with the structural member  28 . Thus, thermal expansion and contraction of the sheath relative to the structural member is accommodated. Further, in accommodation of thermal expansion the sheath  38  is spaced slightly in a longitudinal direction from the hub  16  as illustrated at  42  in  FIG. 6 . 
         [0021]    As mentioned above, and as will now be apparent, the “anti-swirl” vanes of the present invention eliminate drag otherwise encountered with the support structure for the wind turbines, reduce swirl in the discharge air streams of the turbines, and cooperate with the shrouds to provide superior performance of the wind turbines.