Abstract:
Disclosed herein is a rotating radial scoop used to move fluid from a larger radius to a smaller radius, comprising a blade at least partially circumscribing a central axis from an outer radius of the scoop to an capture radius of the scoop, wherein the inner surface of the blade is curved. A scoop having a blade with a curved inner surface extending from the scoop outer radius to a capture radius is disclosed. A turbine engine comprising the scoop, along with a method of providing a fluid to a bearing utilizing the scoop is also disclosed.

Description:
GOVERNMENT RIGHTS 
     This invention was made with Government support under contract number DAAH10-03-2-0007 awarded by the U.S. Army AATD. The Government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to apparatus and methods for capturing lubrication fluid in a turbine engine and, more specifically, to apparatus and methods of capturing fluid from a fluid nozzle with a scoop rotating about a central axis. 
     Turbine engines and other machinery having components that rotate at several thousand revolutions per minute have bearing assemblies that support rotating shafts. Higher cycle temperatures and air temperatures within these engines may result in temperature increases in the rotor and bearings. As such equipment grows in size, larger bearings may be included within such equipment to provide increased support and performance for turbine engines and other such equipment. 
     To minimize the effects of increased temperatures, friction, and the like, which may occur in a turbine engine, bearing assemblies include lubrication systems that provide lubricant to the bearing assemblies supporting rotor shafts, which may in turn reduce wear to the bearing assemblies and which may provide cooling to the bearing assemblies. A typical bearing assembly may include a split inner ring mounted to a rotor shaft, an outer ring, and a rolling element supported therebetween. The lubrication system may include an oil jet to supply oil to a shaft having a plurality of axial grooves in the shaft for supplying oil to the bearing assembly. 
     In such lubrication systems, the oil is transferred from a stationary location to a rotating shaft. One method to do this is to use a radially rotating scoop in combination with a jet that sprays the oil at a rotating scoop. The scoop may have a plurality of blades that captures at least a portion of the oil being sprayed from the jet. The captured oil may then be directed to a plurality of axial slots disposed in the rotating shaft, which eventually terminate in a location to provide the captured fluid to the bearing. 
     For example, U.S. Pat. No. 6,409,464 (“Fisher 464”) is directed to a method of supplying oil to bearings which includes supplying oil through a plurality of scoops to a rotor shaft groove through at least one opening that extends between the rotor shaft inner and outer surfaces of the scoops. The rotor shaft includes a plurality of scoops extending between the rotor shaft inner and outer surfaces. However, the scoops disclosed are conventional flat blade scoops that merely extend between rotor shaft outer and inner surfaces. This reference does not recite particular scoop geometries which maximizes the capture and distribution of oil. 
     U.S. Pat. No. 6,682,222 (“Fisher 222”) is directed to a bi-directional oil scoop for bearing lubrication. Fisher 222 discloses a scoop having a constriction over which the oil sprayed from a jet into the scoop must pass. The constriction acts as a potential barrier for the oil. The portion of the scoop radially past the constriction is arranged to be downstream of the constriction in a centrifugal sense. This constriction thus prevents oil from flowing back towards the jet once it has passed this constriction. However, similar to “Fisher 464” above, this reference discloses conventional flat blade oil scoops which protrude tangentially from the shaft inner surface to the shaft outer surface. This reference does not recite a particular scoop geometry that maximizes the capture and distribution of oil. 
     Radial oil scoops known in the art are not 100% efficient, and the efficiency can depend on shaft speeds. Low efficiency oil scoops may thus result in extra oil inside bearing sumps of the engine, which may decrease engine efficiency by wasting power due to oil churning. To produce the extra flow of fluid from the jet to compensate for the inefficiency of oil scoops, the oil system components size and weight may be increased relative to the size required for the captured amount of fluid. This may also negatively impact power to weight ratio of the engine. As can be seen, there is a need for an improved apparatus and method to capture fluid using a high efficiency scoop rotating about a central axis, preferably a scoop which at a given shaft speed and fluid jet location and velocity has an increased efficiency relative to known flat blade scoops present in the art. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a scoop comprises a blade at least partially circumscribing a central axis of the scoop from an outer radius of the scoop to a capture radius of the scoop, wherein the blade is curved. 
     In another aspect of the present invention, a scoop comprises a blade having an inner surface located between a central axis and a outer radius of the scoop, the blade inner surface at least partially circumscribing the central axis of the scoop from a scoop inlet to a scoop outlet, the scoop inlet located at the outer radius of the scoop, and said scoop outlet located at a capture radius of the scoop or a larger radius, wherein the inside surface of the blade is curved. 
     In yet another aspect of the present invention, a scoop comprises a blade at least partially circumscribing a central axis from a scoop inlet located at an outer radius, to a scoop outlet located at a capture radius, wherein the blade has an inside blade surface between the central axis and the outer radius, the blade having a blade curvature from the outer radius to a barrier located between the scoop inlet and the scoop outlet, wherein the barrier depends radially inward from the blade towards the central axis to define a capture radius; a capture cavity located circumferentially between the barrier and the scoop outlet, the capture cavity being bounded by the capture radius and by the inner surface of a capture arc, wherein the capture arc is between the capture radius and the outer radius of the scoop, wherein the blade curvature comprises a plurality of points P on the blade circumferentially between the scoop inlet and the barrier, and wherein the plurality of points P are defined by the equation: 
                 Point   ⁢           ⁢   P   ⁢           ⁢   radius       Capture   ⁢           ⁢   radius       =     ⅇ     β   ⁢           ⁢   tan   ⁢           ⁢   α             
wherein: α is an angle between a line tangent to said outer radius and said blade inner surface at the outer radius, β is said angular distance of point P from said capture radius, and e is the exponential function.
 
     In yet a further aspect of the present invention, a turbine engine comprises a rotor shaft supported by at least two bearings with or without a seal; a fluid nozzle for ejecting a fluid towards a scoop circumscribing the rotor shaft; wherein the scoop comprises a blade at least partially circumscribing a central axis of the rotor shaft from a first radial position an outer radius of the scoop to a second radial position at a capture radius of the scoop, wherein the blade is curved. 
     In yet a further aspect of the present invention, a method of providing a fluid to a bearing comprises the steps of rotating a shaft, the shaft supported by a bearings, and a scoop circumscribing the rotor shaft; spraying the fluid towards the scoop such that at least a portion of the fluid is captured by the scoop; distributing the fluid received by the scoop to the bearing(s) through a conduit disposed in the rotor shaft, the conduit extending axially from the scoop to the bearing(s) wherein the scoop comprises a blade at least partially circumscribing the central axis from an outer radius to an capture radius, wherein the blade is curved. 
     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 
         FIG. 1  shows a cross sectional view of a scoop of the present invention; 
         FIG. 2  shows a perspective view of the scoop shown in  FIG. 1 ; 
         FIG. 3  shows a partial cross-sectional view of a scoop in proximity to a bearing, according to the present invention; 
         FIG. 4  shows a cross-section of a turbine engine detailing possible placement of the present invention; 
         FIG. 5   a  shows a vector representation of the velocities of a fluid flow and a scoop of the present invention; 
         FIG. 5   b  shows a cross sectional view of the scoop of the present invention with a detailed view of an embodiment; and 
         FIG. 6  shows in block diagram form, the steps of a method of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out 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. 
     Broadly, the present invention generally provides a scoop comprising a curved blade  12  at least partially circumscribing a central axis  14 . This is unlike the prior art wherein the scoop blade inner surface  60  is flat. In another embodiment, the present invention provides for a scoop having a blade curved to maximize fluid capture from a stationary fluid nozzle directed towards the scoop. This is also unlike the prior art wherein the flat blades are not dimensioned to maximize fluid capture. The present invention may be useful in turbine engines, and other such devices which have shafts rotating at several thousand revolutions per minute supported by bearings, which need to be lubricated. 
       FIG. 1  depicts a scoop  10  comprising a blade  12  partially circumscribing a central axis  14  (located perpendicular to the plane of the figure). Blade  12  extends from an outer radius  16  of scoop  10  to a capture radius  24  of scoop  10 . In the embodiment shown in  FIG. 1 , blade inner surface  60  may be curved from outer radius  16  to capture radius  24 . Blade  12  may also comprise a barrier  22  which may extend radially inward from blade  12  towards central axis  14  to a capture radius  24 , wherein capture radius  24  defines a location which is radially outward from shaft radius  18 . Barrier  22  and capture radius  24  may be dimensioned and arranged to form a throat  100  through which fluid  26  entering scoop  10  can pass in order to enter capture cavity  74 . Accordingly, scoop  10  may comprise barrier  22  located at downstream end  25  of the said blade between outer radius  16  and capture radius  24 . Barrier  22  may depend radially inward from blade  10  towards central axis  14  to define capture radius  24 . 
     The area within the inner surface  68  of capture arc  102  and the capture radius  24  defines capture cavity  74 . Barrier  22  may be dimensioned and arranged to prevent fluid from flowing backwards from capture cavity  74  towards outer radius  16 . 
     Blade  12  and capture arc  102  jointly define a scoop inlet  28  between outer radius  16  and shaft radius  18 . The rotation of the scoop  10  drives the fluid in the capture cavity  74  towards distribution conduit  38 . 
     In the embodiment shown in  FIG. 1 , scoop  10  may be disposed on a rotor shaft  36 . Rotor shaft  36 , which may include a component on the shaft adjacent to scoop  10  may include one or more conduits  38 , located in proximity to scoop capture cavity  74  that provide fluid communication between capture cavity  74  and a bearing  46  (see  FIG. 3 ) or rolling element cage  78  or any other component on the shaft to which fluid  26  may be directed. Fluid  26  may be directed at scoop  10  from a fluid nozzle  42  which may be positioned to direct fluid  26  towards scoop  10  at a spray angle  76 , for example, between about 90° and −90°, wherein spray angle  76  may be determined relative to a line T tangent to outer radius  16 . In an embodiment, scoop  10  may comprise one blade  12  (see  FIG. 5   b ). In another embodiment, as shown in  FIG. 1 , scoop  10  may comprise a plurality of blades, e.g., two blades, three blades, or more. 
     As shown in  FIG. 2 , blade  12  may have a blade width  30  indicated by a line that may be substantially parallel with central axis  14 . In an embodiment, blade width  30  may be essentially parallel with central axis  14 . 
       FIG. 3  shows an axial cross section along central axis  14 , and depicts part of scoop  10  having a blade width  30 . As shown in  FIG. 3 , fluid nozzle  42  (e.g., fluid jet, spray nozzle, or the like) may be positioned to direct a stream of fluid  26  from an oil supply  44 . At least a portion of fluid  26  may be intercepted by scoop  10  at scoop inlet  28  located between blade  12  at outer radius  16  and shaft radius  18 . Rotation of rotor shaft  36  produces a relative velocity which propels the fluid  26  inboard along the blade inner surface  60  from outer radius  16  through throat  100  past barrier  22 . Centrifugal force of rotating rotor shaft  36  then propels fluid  26  into capture cavity  74  along the inner surface  68  of capture arc  102  and further to distribution conduit  38 . For controlled flow distribution among various conduits  38 , there may be a fluid reservoir between capture cavity  74  and various conduits  38 . The conduits  38  may distribute the fluid  26  to various components of turbine engine  48 . Fluid  26  may comprise a lubrication fluid such as an oil, a cooling fluid, or the like. 
       FIG. 4  shows a cross section of turbine engine  48 . The arrows indicate possible component locations  50  of a bearing assembly  46  as shown in  FIG. 3 , or other components, which may require lubrication or cooling wherein scoop  10  of the present invention may be located. Taking a turbine engine as an example, scoop  10  may be located in a compressor section, under the combustor, in a turbine section, or the like. Accordingly, a plurality of scoops  10  may be located in a single turbine engine  48 . 
     In an embodiment of the present invention shown in  FIG. 5   b , scoop  10  may have a direction of rotation  70  about central axis  14  which defines the blade velocity vector  56 . Blade velocity vector  56  representing the velocity of the blade inner surface  60  at a particular radius (e.g., radius  16 , radius  24 , or at another radius of choice). As shown in vector representation in  FIG. 5   a , the fluid velocity relative to scoop  10 , represented by relative velocity vector  52 , is the vector sum of the velocity of fluid  26  from fluid nozzle  42 , represented by fluid velocity vector  54 , and the blade velocity vector  56 . The impact angle  58  is the angle between blade velocity vector  56  and relative velocity vector  52  ( FIG. 5   a ). Scoop capture efficiency may be maximized wherein the relative velocity vector  52  is essentially tangent to blade inner surface  60  at the point or points of contact between curved inner surface  60  and fluid  26 . Shape of the curved inner surface  60  may be dimensioned in such a way so as to minimize energy loss as the fluid moves along the inner surface towards the capture radius  24 . 
     In an embodiment, capture radius  24  may be defined as the radius at the point on barrier  22  that may be closest to central axis  14 . In an embodiment, blade  12  may have a curved inner surface  60  over a portion of the length of blade  12  shown ( FIG. 1 ), wherein inner surface  60  may extend from close to the outer radius  16  to barrier  22 . To minimize loss of kinetic energy of fluid  26  being directed into scoop  10 , blade inner surface  60  of blade  12  may comprise a plurality of points P ( FIG. 5   b ) where in the curve defined by points P along blade inner surface  60 , from scoop inlet  28  to barrier  22 , may be a segment of a logarithmic spiral to allow for a uniform transition of fluid  26  from outer radius  16  to capture radius  24 . In other alternative embodiments, points P along inner surface  60  may vary non-uniformly from outer radius  16  to barrier  22 ; points P in inner surface  60  may vary continuously from outer radius  16  to barrier  22 ; points P in inner surface  60  may vary non-continuously from outer radius  16  to barrier  22 ; points P in inner surface  60  may vary eccentrically from outer radius  16  to barrier  22 ; points P in inner surface  60  may vary exponentially from outer radius  16  to barrier  22 . In other alternative embodiments, points P along inner surface  60  may vary on a radius with its center offset from center axis  14  from outer radius  16  to barrier  22  such that the points P form an arc that is a best fit approximation of a logarithmic spiral segment starting from outer radius  16  and ending at center axis  14 . 
     In an embodiment, points P on inner surface  60  may be defined by equation 1: 
     
       
         
           
             
               
                 
                   
                     
                       Point 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       P 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       radius 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       64 
                     
                     
                       Capture 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       radius 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       24 
                     
                   
                   = 
                   
                     ⅇ 
                     
                       β 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       tan 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       α 
                     
                   
                 
               
               
                 
                   Equaton 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     wherein e is the exponential function, angle α (angle  108  in  FIG. 5   b ) is the same as impact angle  58  ( FIG. 5   a ) and angle β (represented in  FIG. 5   b  by reference numeral  66 ) is the angle between barrier  22  and point P. For clarity,  FIG. 5   b  shows only a single point P having a point P radius  64 , however, point P may comprise an infinite number of points along inside blade surface  60  from scoop inlet  28  to barrier  22 . Blade curvature  20  may thus be obtained by solving Equation 1 for different values of β starting from 0, and increasing till point P lies on outer radius  16 . β max  would then approximate the total angle subtended by inner surface  60 , as is represented by reference numeral  106  in  FIG. 5   b.    
     In another embodiment, β max  may be constrained to a certain range of values to obtain a desired size of capture arc  102 . In such a case, for a given outer radius  16 , and capture radius  24 , Equation 1 may be solved for α. 
     Scoop  10  may further comprise a capture cavity  74  partially circumscribing central axis  14  between barrier  22  and end point  34 . Capture cavity  74  may be bounded between capture radius  24  and inner surface of capture arc  68 . 
     Inner surface of capture arc  68  may be centrifugally downhill of barrier  22  such that fluid  26  may be retained within capture cavity  74 . In operation, scoop  10  can intercept fluid  26  being directed (e.g., sprayed) from fluid nozzle  42  towards blade  12 . Fluid  26  can enter scoop inlet  28  and flow radially past barrier  22 . Centrifugal force may then direct fluid  26  outward, in a direction away from central axis  14 , to Inner surface of capture arc  68  and thus within capture cavity  74 , wherein barrier  22  can prevent fluid  26  from flowing back towards scoop inlet  28 . Fluid  26  may then be directed into one or more conduits  38  located proximate to a scoop outlet  32 , which are positioned to provide fluid communication between scoop  10  and bearing  40 , or to other components (not shown) requiring lubrication, cooling, or the like. 
     Accordingly, in an embodiment, the present invention includes a method  200  of providing a fluid to a bearing, comprising a step  202  of rotating a rotor shaft  36  supported by a bearing assembly  40 , wherein scoop  10  circumscribes rotor shaft  36 . In a further step  204 , fluid  26  may be directed, e.g., sprayed, towards scoop  10  such that at least a portion of fluid  26  may be received by scoop  10 . Thereafter, in step  206  fluid received by scoop  10  may be distributed to bearing assembly  40  through conduit  38  disposed between scoop  10  and bearing assembly  40 , which may provide fluid communication between scoop  10  and bearing assembly  40 . In an embodiment, method  200  may further comprise a step  208  of rejecting, or failing to capture, a portion of the fluid, representing inefficiency of the process. Fluid  26  may be sprayed at scoop  10  from fluid nozzle  42  positioned to direct fluid  26  towards scoop  10  at a spray angle  76  between about 90° and about 10°, relative to a line T tangent to outer radius  16 . In an embodiment, spray angle  76  may be between about 70° and about 20°. The method may also include a step  210  of lubricating bearing assembly  40 , rotor shaft  36 , as well as other components requiring lubrication, wherein fluid  26  may be lubrication oil. The method may also include a step  212  of cooling bearing assembly  40 , rotor shaft  36 , as well as other components requiring cooling. As can be appreciated by those skilled in the art, the present invention provides a scoop, which maximizes fluid capture. By providing a scoop comprising a curved blade, the kinetic energy loss of the fluid may be minimized. Thus, the need for increased fluid flow to overcome scoop inefficiency may be reduced or eliminated by the present invention. 
     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.