Abstract:
An oil cooled generator may have stator windings with first portions in contact with a stator core and second non-contact portions. One or more nozzles may be configured to provide a spray pattern of oil which impinges on the non-contact portions even though the nozzles may have orifices oriented so that the lines projected in alignment with longitudinal axes of the orifices do not intersect the non-contact portions of the stator windings.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to electrical generators in which circulated lubrication oil performs a cooling function. 
         [0002]    In some electrical generating systems, specially-designed compact generators have a small size relative to anticipated electrical loads that may be applied to the generator. Such generators may be designed to be positively cooled with circulating lubrication oil. Generators of this type may be used, for example, to supply electrical power in a vehicle such as an aircraft. 
         [0003]    Typically, such generators may employ spiral grooves within a housing to convey oil around a stator core to achieve cooling. Some portions of stator windings may extend beyond the stator core and these portions may not get effective cooling from the oil in the spiral grooves. 
         [0004]    As can be seen, there is a need for a generator cooling system in which stator windings are effectively cooled by circulated lubrication oil. 
       SUMMARY OF THE INVENTION 
       [0005]    In one aspect of the present invention, an oil cooled generator may comprise: stator windings with first portions in thermally-conductive contact with a stator core and second non-contact portions not in such contact; and one or more nozzles having a cylindrical orifice with a longitudinal axis oriented so that a line projected in alignment with the axis does not intersect the non-contact portions of the stator windings, the one or more nozzles configured to provide a spray pattern of oil which impinges on the non-contact portions. 
         [0006]    In another aspect of the present invention, an oil spray system for cooling selected portions of a generator, may comprise: one or more nozzles with an orifice interconnected with a passageway for oil; the orifice having a diameter large enough to pass an integral stream of oil; the orifice having a longitudinal axis oriented so that a line projected in alignment with the axis does not intersect the non-contact portions of the stator windings that does not intersect the selected portions of the generator; the one or more of the nozzles having a deflection surface configured -to produce a spray pattern of the oil which spray pattern impinges on the selected portions of the generator. 
         [0007]    In still another aspect of the present invention, a method for cooling selected portions of a generator with an oil spray may comprise the steps of: supplying pressurized oil to a passageway in the generator; passing at least a portion of the pressurized oil through at least one nozzle orifice interconnected with the passageway to form a integral stream of oil; projecting the integral stream of oil along a path that does not intersect the selected location; deflecting the integral steam and producing a spray pattern of the oil from the integral stream; directing the spray pattern of the oil to impinge on the selected portions of the generator. 
         [0008]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is an enlarged view of a portion of an oil cooled generator in accordance with an embodiment of the invention; 
           [0010]      FIG. 2  is a perspective view of an oil spray nozzle in accordance with an embodiment of the invention; 
           [0011]      FIG. 3  is a cross-sectional view of the nozzle of  FIG. 2  in accordance with an embodiment of the invention; and 
           [0012]      FIG. 4  is a block diagram of a method for spray cooling a generator in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0014]    Various inventive features are described below that can each be used independently of one another or in combination with other features. 
         [0015]    Broadly, embodiments of the present invention generally provide a generator with a lubrication-oil cooling system that includes oil spray nozzles for propelling oil onto portions of stator windings of the generator. 
         [0016]    Referring now to  FIG. 1 , an exemplary embodiment of an oil-cooled generator  10  may be seen to comprise a housing  12 , a stator  14 , a stator core  16 , stator windings  18 , a spiral groove  24  and nozzles  26 . In operation, lubrication oil may be applied under pressure to the generator  10 . The oil may pass through the spiral grove  24  and emerge into various passages (not shown) in the housing  12  before exiting the generator  10 . 
         [0017]    As the oil passes through the spiral groove  24 , the oil may absorb heat from the stator core  16 . The stator core  16  may, in turn, absorb heat from those portions of the stator windings  18  which may be in thermally-conductive contact with the stator core  16 . Some portions of the stator windings  18  may not be in contact with the stator core  16 . As to these portions, herein referred to as non-contact portions  18 - 1 , there may be ineffective heat transfer to the stator core  16 . In other words, the oil in the spiral grove  24  may not provide effective cooling of the non-contact portions  18 - 1  of the stator windings  18 . 
         [0018]    It may be seen that the nozzles  26  may be positioned to allow some of the oil to emerge from the spiral groove  24  so that an oil spray may be directed to the non-contact portions  18 - 1 . In an exemplary embodiment, the nozzles  26  may be placed into the housing  12  within drilled holes  30 . Multiple nozzles  26  may be spaced circumferentially around the housing at equal angular intervals. In an exemplary embodiment of the generator  10 , three of the nozzles  26  may be spaced at  120  degree angular intervals. 
         [0019]    In some generators, the housing  12  may be configured such that the holes  30  may only be drilled with a line  32  that passes through a region of the generator  10  which may not be coincident with location of the non-contact portions  18 - 1 . This condition is illustrated in  FIG. 1  wherein a line  32  that may represent a projection of the axis of the hole  30  does not intersect the non-contact portions  18 - 1 . 
         [0020]    In such a generator, for example the generator  10 , the nozzles  26  may be configured to produce an fan-shaped oil spray pattern directed along a line  34 - 1 . When the oil strikes the non-contact portions it may cover the non-contact portions in a spray region  34 . In other words, the spray pattern  34 - 1  may have an orientation different from that of the line  32  even though the oil may flow out of the spiral groove  24  along the line  32 . 
         [0021]    Within the generator  10 , the desired spray region  34  and desired spray pattern orientation may be achieved with the nozzle  26  configured as shown in  FIGS. 2 and 3 . The nozzle  26  may have a generally cylindrical shape and may have an axis  38 . A cylindrical orifice  40  may be formed coaxially with the nozzle  26 . The nozzle  26  may have an orifice section  26 - 1 , a cutout section  26 - 2  with a reduced cross-section and a deflection section  26 - 3 . 
         [0022]    A deflection surface  42  may be formed on the deflection section  26 - 3 . In an . exemplary embodiment, the nozzle  26  may be provided with a threaded outer surface that may correspond to a threaded inner surface of the hole  30  in the housing  12 . When the nozzle  26  is in position in the housing  12 , the axis  38  of the nozzle  26  may be coincident with the line  32  of the hole  30 . 
         [0023]    Referring now to  FIG. 3 , a cross-sectional view of the nozzle  26  may illustrate that the cutout section  26 - 2  has a thickness less than half of the diameter of the orifice section  26 - 1 . Consequently, oil emerging from the orifice  40  may flow unimpeded from the orifice  40  to the deflection surface  42 . A diameter of the orifice  40  may be large enough to allow the oil to flow through and emerge from the orifice  40  as an integral steam  44 . Thus, even though the spray pattern  34  is a desired output from the nozzle  26 , the orifice  40  may be large enough so that here may be little or no risk of clogging of the orifice  40 . In an exemplary embodiment, the orifice  40  may have a diameter of about 0.020 inch or larger. 
         [0024]    As may be seen in  FIG. 4 , the integral stream  44  of the oil may pass unimpeded for a distance D before striking the deflection surface  42 . The distance D may be about 5 to about 8 times as great as the diameter of the orifice  40 . Upon striking the deflection surface  42 , after traveling the distance 
         [0025]    D, the integral stream  44  of oil may break into a spray and the spray pattern  34  may form (see  FIG. 2 ). In an exemplary embodiment, the defection surface  42  may be oriented at an angle A of about 30° to about 45° relative to the axis  38 . The deflection surface  42  may be oriented orthogonally to a radius of the generator  10 . A screwdriver slot  46  may be provided in the nozzle to allow an assembler of the generator  10  to produce the desired orthogonal orientation. 
         [0026]    Referring now to  FIG. 4 , a flow chart  500  may illustrate an exemplary method which may be employed to cool selected portions a generator with an oil spray. In a step  502 , pressurized oil may be supplied to a passageway in a generator (e.g., oil may be supplied to the spiral groove  24  in the housing  12  of the generator  10 ). In a step  504 , a portion of the pressurized oil may be passed through a nozzle orifice interconnected with the passageway to form a integral stream of oil (e.g., the oil may be passed through the orifice  40  of the nozzle  26  to form the integral stream  44 ). In a step  506 , the integral stream of oil may be projected along a path that does not intersect the selected location (e.g., the stream  44  may be projected along the line  32  which does not intersect with the non-contact portions  18 - 1  of the stator windings  18 ). In a step  508 , the integral steam may be deflected to produce a spray pattern of the oil from the integral stream (e.g., the integral stream  44  may impinge on the deflection surface  42  and the spray pattern  34 - 1  may form). In a step  510 , the spray pattern of the oil may be directed to impinge on the selected portions of the generator (e.g., the deflection surface  42  may be oriented to direct the spray pattern region  34 - 1  onto the non-contact portions  18 - 1  of the stator windings  18 ). 
         [0027]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.