Abstract:
A generator includes a housing and a stator arranged within the housing. The stator includes a first end that extends to a second end, and a plurality of axial flow passages extending between the first and second ends. The generator also includes at least one air flow re-direction member provided on at least one of the first and second ends of the stator. The at least one air flow re-direction member fluidly connects adjacent ones of the plurality of axial flow passages. The at least one air flow re-direction member guides an air flow passing though one of the plurality of axial flow passages in a first direction into an adjacent one of the plurality of axial flow passages in a second direction, the second direction being distinct from the first direction.

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to the art of generators and, more particularly, to a generator including a multiple pass axially cooled stator. 
     Some conventional generators utilize a radial air flow to cool internal components. In particular, axial air flows are directed through a stator portion of the generator. The stator includes a plurality of passages that serve as a conduit for a cooling airflow. The cooling air flow is passed, in one direction, through the plurality of passages to conduct heat away from the stator. By lowering internal stator temperatures, generator efficiency is enhanced. 
     Smaller generators, such as those employed in wind turbines, may also employ stators having axial flow passages. However, some generator designs employ a shorter stator length. As such, the cooling airflow is not utilized efficiently. More specifically, the shorter stator length and correspondingly shorter axial flow passage do not provide adequate time for sufficient heat transfer between the stator and the air flow. Accordingly, in shorter generators, exit temperature of the cooling air flow is much lower than the exit temperature of the cooling air flow in larger generators. As a consequence, heat carrying capacity of the cooling air flow is under utilized. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a generator includes a housing and a stator arranged within the housing. The stator includes a first end that extends to a second end, and a plurality of axial flow passages extending between the first and second ends. The generator also includes at least one air flow re-direction member provided on at least one of the first and second ends of the stator. The at least one air flow re-direction member fluidly connects adjacent ones of the plurality of axial flow passages. The at least one air flow re-direction member guides an air flow passing through one of the plurality of axial flow passages in a first direction into an adjacent one of the plurality of axial flow passages in a second direction, the second direction being distinct from the first direction. 
     According to another aspect of the invention, a method of cooling a generator stator includes guiding a cooling air flow into a first end of a first axial flow passage arranged within the generator stator, passing the cooling air flow along the axial flow passage in a first direction towards a second end, re-directing the cooling air flow from the second end of the axial flow passage toward a first end of an adjacent axial flow passage, and passing the cooling air flow along the adjacent axial flow passage in a second direction, the second direction being opposite the first direction to establish a multiple pass axial cooled stator. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a lower left perspective view of a multiple pass axially cooled generator in accordance with an exemplary embodiment; 
         FIG. 2  is an exploded view of a stator including air flow re-direction members in accordance with an exemplary embodiment; 
         FIG. 3  is a partial front perspective view of an air flow re-direction member in accordance with an exemplary embodiment; 
         FIG. 4  is a partial rear perspective view of an air flow re-direction member in accordance with an exemplary embodiment; 
         FIG. 5  is a partial front perspective view of an air flow re-direction member constructed in accordance with another exemplary embodiment; and 
         FIG. 6  is a partial perspective view of a stator including air flow re-direction members in accordance with another exemplary embodiment. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1-4 , a generator constructed in accordance with an exemplary embodiment is indicated generally at  2 . Generator  2  includes a housing  4  that surrounds a stator  6  and a rotor (not shown). Stator  6  includes a first end  10  that extends to a second end  12  through an intermediate portion  14  that defines an inner diametric portion  16  and an outer diametric portion  17 . As shown, stator  6  is formed from a plurality of stacked laminations, one of which is indicated at  18 . Stator  6  includes a plurality of slots/grooves  20  formed on inner diametric portion  16  and a plurality of compression bolt slots  23  formed about outer diametric portion  17 . 
     As best shown in  FIG. 2 , stator  6  includes a plurality of axial flow passages, indicated generally at  28 , that extend between first and second ends  10  and  12 . Axial flow passages  28  provide conduits for a cooling air flow that passes through stator  6 . Stator  6  is also shown to include first and second finger/compression plates  32  and  33 . First compression plate  32  abuts first end  10  while second compression plate  33  abuts second end  12 . Each compression plate includes a plurality of openings  35  and  36  that register with axial flow passages  28 , a plurality of grooves  38  and  39  that register with grooves  20  and a plurality of notches  41  and  42  that register with compression bolt slots  23 . With this arrangement, first and second compression plates  32  and  33  serve to press the plurality of laminations  18  together to form one solid body for structural and vibrational purposes. 
     In accordance with the exemplary embodiment, stator  6  includes a first air flow re-direction member  47  and a second air flow re-direction member  48 . In the exemplary embodiment shown, first air flow re-direction member  47  is mounted to and abuts first compression plate  32  while second air flow re-direction member  48  is mounted to and abuts second compression plate  33 . Air flow re-direction members  47  and  48  are mounted to corresponding ones of compression places  32  and  33  through, for example, the use of a compression ring and or bolting blocks (not shown). As each air flow re-direction member  47 ,  48  is substantially identically formed, a detailed description will follow referencing first air flow re-direction member  47  with an understanding that second air flow re-direction member  48  is similarly constructed. 
     As best shown in  FIG. 3  air flow re-direction member  47  includes a main body  54  having an inner diametric section  56  and an outer diametric section  57  that define a first surface  59  and an opposing second surface  60 . A plurality of grooves  63  radiate along inner diametric section  56  and a plurality of notches  65  are formed at outer diametric section  57 . Grooves  63  are arranged to register with grooves  20  and  38 , while notches  65  are arranged to register with notches  41  and compression bolt slots  23 . In addition, air flow re-direction member  47  includes a plurality of openings indicated generally at  70  that register with select ones of the plurality of axial flow passages  28  to define inlets and outlets (not separately labeled) as will be detailed more fully below. 
     In further accordance with the exemplary embodiment, air flow re-direction member  47  includes a plurality of air flow re-direction components indicated generally at  74 . Each air flow re-direction component includes a first end portion  80  that extends to a second end portion  81  through a guide portion  82 . In addition, each air flow re-direction component includes an arcuate section  86  ( FIG. 4 ) that is concave when viewed from second surface  60 . With this arrangement, first end portion  80  is positioned to register with one of the plurality axial flow passages  28  while second end portion  81  is positioned to register with another one of the plurality of axial flow passages  28 . In this manner, air entering one of the inlet openings (not separately labeled) flows through the one of the plurality of axial flow passages  28  impinges upon air flow re-direction component  74  and is redirected into the another of the plurality of axial flow passages  28  before exiting from one of the outlet openings (not separately labeled) such that the air flow passes multiple times through stator  6 . 
     In accordance with one exemplary embodiment illustrated in  FIG. 5 , an air flow re-direction member  90  is molded from a thermoplastic polymer such as, for example, polyethylene, polypropylene, or a polyamide. Air flow re-direction member  90  may also be molded from a fiber-reinforced polymer, or fiber-reinforced organic compound. Air flow re-direction member  90  includes a plurality of air flow re-direction components  92  as well as a plurality of openings  94  that are configured to register with respective ones the plurality axial flow passages  28 . Air flow re-direction member  90  is added to stator  6  after a resin application process. 
     In accordance with another aspect of the invention, air flow re-direction member  47  constitutes a compression plate. With this arrangement, air flow re-direction components  74  are stamped into the compression plate. In this manner, the stamped air flow re-direction members are employed as compression plates to press the plurality of laminations together to form the one solid body. As such, there is no need for additional compression plates and stator  6  can be formed using fewer components. In any event, the cooling air flow is passed multiple times through stator  6  to enhance heat absorption. That is, cooling air having substantial additional heat carrying capacity is not passed from stator  100 . The multiple axial passes of cooling air flow is particularly advantageous in generators having a thin profile such as used in wind generators and marine/hydro-power applications, however multiple axial passes of cooling air flow can be utilized in a wide array of generator models for various applications. 
     Reference will now be made to  FIG. 5  in describing a stator  100  constructed in accordance with another exemplary aspect of the invention. As shown, stator  100  includes a first end  104  that extends to a second end  106  through an intermediate portion  108  that define an inner diametric portion  111  and an outer diametric portion  112 . As shown, stator  100  is formed from a plurality of stacked laminations, one of which is indicated at  113 . Stator  100  includes a plurality of slots/grooves  115  formed on inner diametric portion  111  and a plurality of compression bolt slots  118  formed about outer diametric portion  112 . 
     In addition, stator  100  includes a plurality of axial flow passages, indicated generally at  122 , that extend between first and second ends  104  and  106 . Select ones of axial flow passages  122  include an inlet, such as indicated at  123  while other select ones of the axial flow passages  122  include an outlet such as indicated at  124 . As will be detailed more fully below, axial flow passages  122  provide conduits for a cooling air flow that passes through stator  100 . Stator  100  is also shown to include first and second finger/compression plates  129  and  130 . First compression plate  129  abuts first end  104  while second compression plate  130  abuts second end  106 . Compression plate  129  includes a plurality of openings one of which is indicated at  135  that register with axial flow passages  122 , a plurality of grooves, such as indicated at  138 , that register with grooves  115  and a plurality of notches  139  that register with compression bolt slots  118 . Of course it should be understood that compression place  130  includes similar structure. In a manner similar to that described above, first and second compression plates  129  and  130  serve to press the plurality of laminations  113  together forming one solid body for structural and vibrational purposes. 
     In further accordance with the exemplary embodiment shown, stator  100  includes a first air flow re-direction member  140  and a second air flow re-direction member  141 . First air flow re-direction member  140  is defined by a first channel  144  formed at first end  104  while second air flow re-direction member  141  is defined by a second channel  145  formed at second end  106 . More specifically, channel  144  is formed within laminations  118  and connects adjacent ones of the plurality of axial flow passages while channel  145  is formed within laminations  118  at second end  106  and connects with one of the plurality of axial flow passages  122  connected to channel  144  and another of the plurality of axial flow passages. Of course it should be understood that while only two channels are shown and described, stator  100  includes a plurality of channels that extend about the outer diametric portion  112 . 
     With this arrangement, the cooling air flow passes in a back and forth pattern throughout stator  100 . That is, the cooling air enters inlet  123  passes along one of the plurality of axial flow passages  122  to channel  145 , transitions to another of the plurality of axial flow passages  122  before flowing through channel  144  to transition to yet another of the plurality of axial flow passages  122  and exiting from outlet  124 . In this manner, the cooling air flow is passed multiple times through stator  100  to enhance heat absorption. That is, cooling air having substantial additional heat carrying capacity is not passed from stator  100 . The multiple axial passes of cooling air flow is particularly advantageous in generators having a thin profile such as used in wind generators and marine/hydro-power applications, however multiple axial passes of cooling air flow can be utilized in a wide array of generator models for various applications. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.