Abstract:
A gearbox oil cooling assembly for a gearbox driving a drive shaft having a drive shaft coupling. The assembly includes a heat exchanger to receive and cool an oil from the gearbox and having an inlet. Also included is an impeller axially disposed between the heat exchanger and the drive shaft coupling, wherein the impeller is operatively coupled to, and rotated by, the drive shaft operatively coupled to the drive shaft coupling. Further included is an exhaust duct operatively coupled to the heat exchanger and disposed radially outwardly around the impeller and defining an airflow pathway through which air passes through the inlet, the impeller and through the exhaust duct according to the rotation of the impeller to cool the oil in the heat exchanger.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a 371 National Stage of International Application No. PCT/US2015/032385, filed on May 26, 2015, which claims priority to U.S. Provisional Application No. 62/031,440, filed on Jul. 31, 2014, the contents of which are incorporated by reference herein in their entirety. 
     
    
     FEDERAL RESEARCH STATEMENT 
       [0002]    This invention was made with Government support under Contract No. N00019-06-C-0081 with the United States Navy. The Government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    The embodiments herein relate to aircrafts and, more particularly, a gearbox oil cooling assembly disposed on aircrafts. 
         [0004]    Gearboxes that generate high levels of heat during operation often require an actively cooled, external heat exchanger to dissipate the heat. Various challenges exist relating to packaging all of the necessary heat dissipating components into a compact envelope while maintaining an efficient and reliable system. A rotary-wing aircraft is an example of an application in which the above-described challenges persist. For example, some rotary-wing aircrafts employ shaft-driven power to impellers through belts, pulleys, and belt-tensioners in order to rotate the impellers. Typically, external oil hoses facilitate transfer of the hot and cooled oil between the gearbox and a heat exchanger. An airflow is facilitated with the impeller and used to cool the heat exchanger, but the heated exhaust air is typically exhausted internally relative to the aircraft and in the vicinity of the gearbox, thereby undesirably leading to operation of the gearbox at an elevated temperature. Furthermore, spinning of the impeller often requires the use of shaft-driven power through belts, pulleys, and belt-tensioners, which increases complexity, thereby leading to potential reliability issues. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    According to one embodiment, a gearbox oil cooling assembly for a gearbox driving a drive shaft having a drive shaft coupling. The assembly includes a heat exchanger to receive and cool an oil from the gearbox and having an inlet. Also included is an impeller axially disposed between the heat exchanger and the drive shaft coupling, wherein the impeller is operatively coupled to, and rotated by, the drive shaft operatively coupled to the drive shaft coupling. Further included is an exhaust duct operatively coupled to the heat exchanger and disposed radially outwardly around the impeller and defining an airflow pathway through which air passes through the inlet, the impeller and through the exhaust duct according to the rotation of the impeller to cool the oil in the heat exchanger. 
         [0006]    According to another embodiment, a gearbox oil cooling assembly for a gearbox driving a drive shaft having a drive shaft coupling. The assembly includes a heat exchanger operatively coupled to the gearbox. Also included is a plurality of tubes disposed at an internal location relative to the gearbox and the heat exchanger, the plurality of tubes comprising a first tube configured to route an oil to the heat exchanger for cooling therein and a second tube configured to return the oil to the gearbox. Further included is an impeller axially disposed between the heat exchanger and the drive shaft coupling, wherein the impeller is operatively coupled to, and rotated by, the drive shaft operatively coupled to the drive shaft coupling. Yet further included is an exhaust duct operatively coupled to the heat exchanger and disposed radially outwardly around the impeller, wherein the impeller, the heat exchanger, and the exhaust duct are concentrically positioned about a central axis of the drive shaft, wherein at least a portion of each of the drive shaft coupling, the impeller, the exhaust duct, the heat exchanger, and the gearbox are disposed in an axially stacked arrangement, wherein the exhaust duct defines an airflow pathway through which air passes through an inlet, the impeller and through the exhaust duct according to the rotation of the impeller to cool the oil in the heat exchanger. 
         [0007]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the drive shaft and the impeller are rotated about a central axis, wherein the heat exchanger is concentrically oriented about the central axis. 
         [0008]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the oil is routed to the heat exchanger within a first tube and the oil is returned to the gearbox within a second tube. 
         [0009]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the first tube and the second tube are disposed at an internal location relative to the gearbox and the heat exchanger. 
         [0010]    In addition to one or more of the features described above, or as an alternative, further embodiments may include a gearbox housing, wherein the heat exchanger is directly coupled to the gearbox housing. 
         [0011]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the exhaust duct is directly coupled to the heat exchanger. 
         [0012]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the exhaust duct circumferentially surrounds the impeller and includes a flow path outlet configured to directly exhaust an airflow to the atmosphere. 
         [0013]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the gearbox oil cooling assembly is disposed on a helicopter and the flow path outlet of the exhaust duct is positioned proximate a fairing of the helicopter. 
         [0014]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the impeller, the heat exchanger, and the exhaust duct are concentrically positioned about the drive shaft. 
         [0015]    In addition to one or more of the features described above, or as an alternative, further embodiments may include a portion of the gearbox concentrically positioned about a central axis of the drive shaft. 
         [0016]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that the heat exchanger includes at least one air inlet configured to receive an airflow in a radial direction, wherein the airflow is routed axially through the heat exchanger to the exhaust duct. 
         [0017]    In addition to one or more of the features described above, or as an alternative, further embodiments may include that at least a portion of each of the drive shaft coupling, the impeller, the exhaust duct, the heat exchanger and the gearbox are disposed in an axially stacked arrangement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    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: 
           [0019]      FIG. 1  is a perspective view of a rotary-wing aircraft including a gearbox oil cooling assembly therein; 
           [0020]      FIG. 2  is a perspective view of a gearbox and a gearbox oil cooling assembly in an assembled condition; 
           [0021]      FIG. 3  is a side view of the gearbox oil cooling assembly and a portion of the gearbox; 
           [0022]      FIG. 4  is a partial cross-sectional side view of the gearbox oil cooling assembly and a portion of the gearbox; 
           [0023]      FIG. 5  is a cross-sectional side view of the gearbox oil cooling assembly and a portion of the gearbox; and 
           [0024]      FIG. 6  is a perspective view of an exhaust location of the gearbox oil cooling assembly located proximate an exterior portion of the aircraft. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring to  FIG. 1 , schematically illustrated is a rotary-wing aircraft  10  having a main rotor system  12 . The aircraft  10  includes an airframe  14  having an extending tail  16  which mounts a tail rotor system  18 , such as an anti-torque system. The main rotor assembly  12  is driven through a main power transmission gearbox (referenced generally with numeral  20 ) by one or more engines. Although a particular helicopter configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as ground vehicles, maritime engines, industrial transmissions, jet aircraft, turbofan engines, high speed compound rotary wing aircraft with supplemental translational thrust systems, dual contra-rotating, coaxial rotor system aircraft, turbo-props, tilt-rotors and tilt-wing aircraft, and such like may also benefit from the embodiments described herein. 
         [0026]    The main power transmission gearbox  20  carries torque from the engines through a multitude of gear train paths to a main rotor shaft  22  of the main rotor system  12 . The main gearbox  20  is coupled to at least one nose gearbox output shafts to harness the power from the engines, provide further speed reduction and increase output torque. The main gearbox includes gear sets therein for reducing the shaft speed during the transmission of power from the nose gearbox(es) to the output devices. The gearbox  20  is typically located within a housing which may at least partially support the main rotor shaft  22 . The embodiments described herein are best illustrated by reference to the illustrated rotary-wing aircraft main power transmission gearbox having highly-loaded torque transmitting gears, bearings and shafts, however, it will be appreciated that the inventive teachings are applicable to any gearbox that utilizes an actively cooled heat exchanger where a compact envelope is required. To cool oil required by the nose gearbox, a gearbox oil cooling assembly is included, the location of which is generally referenced with numeral  26 . The gearbox oil cooling assembly  26  will be described more detail below. 
         [0027]    Referring now to  FIGS. 2-5 , various views illustrate the gearbox oil cooling assembly  26 , as well as a portion of the nose gearbox that the gearbox oil assembly  26  is employed in conjunction with. The nose gearbox requires the use of oil therein and the oil is heated during operation. Cooling of the oil is required and the gearbox oil cooling assembly  26  is employed to facilitate such cooling, while being configured to have a compact packaging capability, in combination with the nose gearbox. 
         [0028]    As shown, the nose gearbox is mounted to, and within, a housing  28  (partially illustrated), a portion of which is in axial abutment with the nose gearbox. The gearbox oil cooling assembly  26  is operatively coupled to the housing  28  portion that is illustrated. The gearbox oil cooling assembly  26  includes a heat exchanger  30  employed to cool the oil of the nose gearbox, an impeller  32 , and an exhaust duct  34 . The above-noted components of the gearbox oil cooling assembly  26  are disposed in a substantially axially stacked arrangement with each other and with the housing  28 , as well as at least a portion of the nose gearbox. As will be appreciated from the description herein, such an axially stacked arrangement facilitates the ability to package the assembly in a compact space. Additionally, the need for belts, pulleys, and related components is eliminated due to the concentric disposition of the components relative to a central axis  36  of a drive shaft  38 . The drive shaft  38  extends in an axial direction about the central axis  36 . 
         [0029]    The heat exchanger  30  is an annular heat exchanger that is situated concentric relative to the drive shaft  38  and is axially disposed between the housing  28  of the nose gearbox and the exhaust duct  34 . The heat exchanger  30  is operatively coupled to both the nose gearbox and the exhaust duct  34 . In some embodiments, the heat exchanger  30  is directly coupled to the housing  28  of the nose gearbox and to the exhaust duct  34 . At least two oil transfer tubes extend between the nose gearbox to the heat exchanger  30  for routing of the oil to the heat exchanger for cooling therein. The oil transfer tubes are located substantially within internal locations of both the gearbox housing  28  and the heat exchanger  30 . For example, a first tube  40  is configured to route hot oil  44  from the nose gearbox to the heat exchanger  30  and a second tube  42  is configured to route relatively cooled oil  46  back to the nose gearbox. The first tube  40  and the second tube  42  are oriented in a substantially parallel arrangement relative to each other, as shown, however, one can appreciate that alternative relative orientations may be suitable. 
         [0030]    The drive shaft  38  is operatively coupled to a drive shaft coupling  48 , which is also coupled to the impeller  32 . This arrangement “sandwiches” the impeller  32  between the drive shaft coupling  48  and the heat exchanger  30 . As such, rotation of the impeller  32  is directly driven by the drive shaft coupling  48  and the drive shaft  38 . Both the impeller  32  and the drive shaft  38  rotate about the central axis  36  of the drive shaft  38 . Disposed radially outwardly of the impeller  32  is the exhaust duct  34 . The exhaust duct  34  circumferentially surrounds at least a portion of, but typically surrounds the entirety of the impeller  32  circumference. 
         [0031]    As noted above, the exhaust duct  34  includes an annular passage  50  that is in fluid communication with an impeller path  52  and a heat exchanger path  54 . In combination, the annular passage  50 , the impeller path  52  and the heat exchanger path  54  form a single, continuous passage for an airflow  56  to pass through. The airflow  56  is facilitated during operation of the impeller  32 , as the airflow  56  is drawn into the heat exchanger path  54  in a radial direction through at least one air inlet  55 . The airflow  56  cools the hot oil  44  passing through the first tube  40  via heat transfer. During the process, the airflow  56  is heated as a result of the heat transfer and is routed through the heat exchanger path  54  to the impeller path  52  and into the annular passage of the exhaust duct  34 . 
         [0032]    The exhaust duct  34  includes at least one flow path outlet  58 . As shown in  FIG. 6 , the at least one flow path outlet  58  is oriented such that direct expulsion of the airflow  56  is made to an exterior location of the aircraft  10 . In particular, the flow path outlet  58  is positioned to expel the airflow  56  through a fairing  60  of the aircraft  10  to the atmosphere. Advantageously, expulsion to an exterior location reduces heating of the nose gearbox and the oil associated therewith, in comparison to expulsion at an interior location proximate the nose gearbox. 
         [0033]    As described in detail above, the components of the gearbox oil cooling assembly  26  are disposed in an axially stacked arrangement and are concentrically located about the central axis  36  of the drive shaft  38 . Specifically, the drive shaft coupling  48 , the impeller  32 , the exhaust duct  34 , and the heat exchanger  30  are axially stacked with respect to each other and are concentrically disposed about the central axis  36 . Additionally, at least a portion of the nose gearbox, including the housing  28 , is disposed in the stacked arrangement and concentrically about the central axis  36 . Such an arrangement facilitates compact packaging of the overall assembly and functions within a restrictive envelope situated between the nose gearbox, drive shaft  38 , diaphragm coupling and fairings. The direct-drive configuration of the impeller  32  with the drive shaft  38  reduces part count and complexity, thereby increasing its reliability over alternative impeller drive arrangements, including electric arrangements and belt-pulley designs. Furthermore, the use of short, internally disposed oil transfer tubes provides for a more compact, lightweight and reliable system. 
         [0034]    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.