Abstract:
An exemplary method of controlling fluid flow in a ram air turbine assembly, includes redirecting flow moving in an axial direction against the surface of a drive shaft to flow moving in a radial direction away from the drive shaft to limit flow of the fluid from a hydraulic pump to a generator.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of U.S. patent application Ser. No. 13/430,925 filed Mar. 27, 2012. 
    
    
     BACKGROUND 
     This disclosure relates to ram air turbines utilized to provide emergency power for an aircraft. More particularly, this disclosure relates to controlling fluid within a ram air turbine that supplies both electric and hydraulic power to an aircraft. 
     A ram air turbine is used to generate supplemental power in an aircraft by extracting power from an air stream along the exterior of the aircraft during flight. The ram air turbine includes a turbine that drives an electric motor or hydraulic pump. In operation, the turbine is moved from a stowed position within the aircraft to a position that provides clearance for blades of the turbine and the aircraft. The turbine is mounted at the end of a strut and drives a turbine drive shaft that in turn drives the electric motor or hydraulic pump. Hydraulic fluid from the hydraulic pump may be damaging to generator components. 
     SUMMARY 
     A method of controlling fluid flow in a ram air turbine assembly according to an exemplary aspect of the present disclosure includes, among other things, redirecting flow moving in an axial direction against the surface of a drive shaft to flow moving in a radial direction away from the drive shaft to limit flow of the fluid from a hydraulic pump to a generator. 
     In a further non-limiting embodiment of the foregoing method, the method includes using a radially extending feature of the drive shaft to initiate the redirecting. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes driving the hydraulic pump and the generator using the drive shaft. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes rotating a turbine of a ram air turbine to rotate the drive shaft. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid is a hydraulic fluid. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes moving a strut from a stowed position to a deployed position, and redirecting after the deploying. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes rotating the drive shaft about a drive shaft axis to directly drive the hydraulic pump and the generator when the strut is in the deployed position. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes supporting a turbine within the strut, the strut connected to a turbine shaft that rotates about a turbine shaft axis transverse to the drive shaft axis. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes redirecting flow moving in the axial direction to flow moving in the radial direction into an annular cavity. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes holding at least a portion of both the hydraulic pump and the generator within a housing assembly and providing the annular cavity within the housing assembly. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes draining the fluid from the annular cavity using a conduit. 
     In a further non-limiting embodiment of any of the foregoing methods, the drive shaft, the hydraulic pump, and the generator are axially aligned. 
     In a further non-limiting embodiment of any of the foregoing methods, the generator is axially closer to the turbine than the hydraulic pump. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes redirecting using an interruption in the drive shaft. 
     In a further non-limiting embodiment of any of the foregoing methods, the interruption extends circumferentially and continuously about the entire axis. 
     In a further non-limiting embodiment of any of the foregoing methods, the interruption comprises a first rib extending radially from the drive shaft and a second rib extending radially from the drive shaft, the first rib axially spaced from the second rib. 
     A method of controlling flow in a ram air turbine according to another exemplary aspect of the present disclosure includes, among other things, rotating a turbine to rotate a turbine shaft about a turbine shaft axis when a ram air turbine is in a deployed position, rotating a drive shaft about a turbine shaft axis with the turbine shaft, the turbine shaft rotating about a turbine shaft axis that is transverse to the drive shaft axis, driving a hydraulic pump and a generator with the drive shaft, and redirecting a fluid flowing from the hydraulic pump to a generator into an cavity provided by a housing of the ram air turbine. 
     In a further non-limiting embodiment of the foregoing method, the cavity is an annular cavity. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes redirecting using an interruption in the drive shaft. 
     In a further non-limiting embodiment of any of the foregoing methods, the method includes holding the hydraulic pump, the generator, or both within the housing. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a schematic view of an example ram air turbine including a generator and a hydraulic pump. 
         FIG. 2  is a sectional view of the  FIG. 1  ram air turbine. 
         FIG. 3  is a close-up sectional view of an interface between the generator and the hydraulic pump of the  FIG. 1  ram air turbine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , an example ram air turbine assembly (RAT)  10  is mounted to an airframe  12  and is deployable to provide both electric power and hydraulic pressure. The example RAT  10  includes a turbine  14  that rotates responsive to air flow along the outside of the airframe  12 . The turbine  14  is supported at the end of strut  22  attached to a generator housing  24 . The generator housing  24  is mounted for rotation to the airframe  12  with a swivel post  28 . 
     A generator  32  disposed within the generator housing  24  is coupled to a hydraulic pump  38 . The generator  32  generates electric power that can be supplied to an aircraft system such as is schematically indicated at  40 . The hydraulic pump  38  receives fluid from a fluid supply  44  and pumps the fluid to various systems indicated at  42  that utilize pressurized fluid for operation. 
     The turbine  14  rotates to drive a turbine shaft  46  about an axis  48 . The turbine shaft  46  drives a gearbox  50 . The example gearbox  50  is disposed aft of the turbine  14  and along the axis  48  of rotation of the turbine  14  and turbine shaft  46 . The example gearbox  50  drives a drive shaft  52  that rotates about an axis  54  that is transverse to the axis  48 . The drive shaft  52  extends from the gearbox  16  through the strut  22  to the generator  32 . The drive shaft  52  is coupled to drive the generator  32  at a desired speed. 
     The example gearbox  50  includes gears that provide a desired ratio of rotational speed between the turbine shaft  46  and the drive shaft  52 . In this example, the drive shaft  52  is rotated at a greater speed than the turbine shaft  46 . The gearbox  50  can be configured to provide any desired speed ratio relative to rotation of the turbine  14 . 
     The speed at which the drive shaft  52  is rotated is determined to provide the desired rotational speed required to drive the generator  32  and produce a desired amount of electrical energy at the desired frequency. The electrical energy produced by the generator  32  is then transmitted to the aircraft system schematically indicated at  40 . 
     A second drive shaft  56  couples the hydraulic pump  38  in rotation with the generator  32  such that the hydraulic pump  38  rotates at the same speed as the generator  32 . As the hydraulic pump  38  and the generator  32  are coupled to rotate together, the hydraulic pump  20  communicates pressurized fluid to the aircraft systems  40  at the same time as the generator  18  produces electric power. 
     The generator  18  is supported within the generator housing  24  at an end distal from the turbine  14 . The generator housing  24  includes a mounting bracket  60  and an integral swivel bracket  58 . The mounting bracket  60  attaches to an actuator  62 . The actuator  62  drives movement of the RAT  10  between a stowed position within the airframe  12  and the deployed position schematically shown in  FIG. 1 . 
     The swivel bracket  58  mounts to the swivel post  28  to support the RAT  10 . The strut  22  is attached to the generator housing  24  and therefore moves with the pivoting movement of the generator housing  24 . The hydraulic pump  20  is mounted to the generator housing  24  and therefore also rotates with the generator housing  24  during movement to the deployed position. 
     Referring to  FIG. 3 , the second drive shaft  56  is rotated by the main drive shaft  52  through a spline connection  66 . The second drive shaft  56  couples rotation of rotors within the generator  32  with rotation of the hydraulic pump  38 . In other examples, the second drive shaft  56  is not a separate shaft but is instead a continuation of the drive shaft  52 . 
     The hydraulic pump  38  is mostly vertically above the generator  32  when the RAT  10  is deployed. When deployed, some of the face seal leakage flows from the hydraulic pump  38  against an exterior surface  68  of the second drive shaft  56 , and toward the generator  32 . The example fluid is hydraulic fluid such as Skydrol® or some other type of phosphate ester hydraulic fluid. The fluid can damage components of the generator  32  as is known. When not deployed, the fluid is not in a position to flow downward along the exterior surface  68 . 
     The example second drive shaft  56  includes an interruption  70  that limits flow of fluid from the hydraulic pump  38  to the generator  32 . The interruption  70  is axially between the hydraulic pump  38  and the generator  32 . The example interruption  70  includes two ribs  72  extending radially from the exterior surface  68  positioned axially between the generator  32 . The ribs  72  are axially spaced from each other, and each of the ribs  72  extends circumferentially and continuously about the entire axis  54 . 
     In one specific example, the diameter of the second drive shaft  56  is about 0.65 inches (1.65 centimeters), and the ribs  72  each extend more than about 0.005 inches (0.127 millimeters) from the exterior surface  68 . In some examples, the ribs extend about 0.039 inches (1 millimeter) from the exterior surface  68 . 
     The ribs  72  may be considered slinger rings. Other examples of the interruption  70  may include other numbers of ribs or other features. 
     The example interruption  70  redirects fluid flowing from the hydraulic pump  38  to the generator  32  when the second drive shaft  56  is rotated. In some examples, the second drive shaft  56  rotates at about 12,000 rotations per minute. As the fluid flow moves over the interruption  70 , the fluid is moved radially outward, which causes the fluid to separate from the drive shaft  56  and to move radially outward due to the increased centrifugal force. The fluid moves from the second drive shaft  56  into a cavity  74  that extends about the axis  54 . One of the ribs  72   a  is located radially inside of a pump ring  82  to direct leakage away from shaft  56  at the first opportunity. Most of the leakage will encounter the inner diameter of the pump ring  82 , and gravity will cause it to flow from there to drain passage  78  (since the generator shaft  56  is not quite vertical when deployed). 
     Fluid that gets by the rib  72   a  will encounter the rib  72   b , which will expel the fluid into cavity  74 . Fluid that somehow passes both ribs  72   a  and  72   b  and enters the region between the rib  72   b  and the splined portion of the shaft  56  will be centrifugally expelled to the inner diameter of the shaft  52 , where it can then be flung out into cavity  74 . 
     The generator  18  is constructed from materials that can withstand the occasional splash of hydraulic fluid. But full immersion or sustained contact would be undesirable. The fluid exclusion features described are designed to prevent this. An air gap exists between the second drive shaft  56  and a shield  80  to avoid seal drag or seal friction heating with unreliable lubrication that could occur on a rapidly rotating shaft. 
     The example cavity  74  is an annular cavity in this example. A portion of the cavity  74  is provided by a housing  76  of the hydraulic pump  38 , and another portion of the cavity  74  is provided by the generator housing  24 . A conduit  78  drains the fluid from the cavity  74  into an ecology bottle (not shown) that can be removed from the RAT  10 . 
     The example generator  18  includes a shield  80  that is integral with a bearing liner of the RAT  10 . Fluid that lands on the shield  80  tends to move toward the conduit  78  due to gravity. The shield  80  has a raised flange on the inside of the shield  80  that keeps fluid from dripping into bearing areas  86  of the generator  18 . Gravity keeps fluid from travelling over the flange. The flange is located axially away from an end  84  of the drive shaft  52  so fluid from inside the drive shaft  52  can spray harmlessly past the gap to the bearing areas  86 . 
     In some examples, an O-ring (not shown) may surround the second drive shaft  56  between the hydraulic pump  20  and the generator  18 . 
     Features of the disclosed examples include providing inline power generation with a single gearbox  16  that drives both the generator  18  and the hydraulic pump  20  while limiting leakage flow from the hydraulic pump  20  to the generator. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.