PATENT ABSTRACT
An example method of deaerating a mixture of fluid and air includes communicating a mixture of fluid and air directly against a wall of a reservoir to separate the fluid from the air. The method reuses the fluid held within the reservoir after the separating.

PATENT DESCRIPTION
BACKGROUND 
       [0001]    This disclosure relates generally to deaerating a fluid and, more particularly, to deaerating the fluid without requiring a separate assembly dedicated to deaerating. 
         [0002]    Fluid, such as oil, that has been used to cool and lubricate moving components is often recirculated. Fluid mixed with substantial amounts of air is less suitable for cooling and lubricating. Because the fluid mixes with air during use, the fluid is deareated prior to reuse. 
         [0003]    Gearboxes include many rotating components that are cooled and lubricated with a fluid. After circulating through the gearbox, the fluid moves through a cylindrical deaerating structure to remove air. The fluid then flows from the deaerating structure to a holding reservoir where it is stored until being moved back into the gearbox. 
       SUMMARY 
       [0004]    An example method of deaerating a mixture of fluid and air includes communicating a two-phase mixture of fluid and air directly against a wall of a reservoir to separate the air from the fluid. The method recirculates the fluid held within the reservoir after the separating. 
         [0005]    A method of deaerating a mixture of aircraft lubricating fluid and air includes communicating the mixture into an open area of a reservoir. The method includes collecting the aircraft lubricating fluid in a lower portion of the reservoir and collecting the separated air in an upper portion of the reservoir that is different from the first portion. The method uses the aircraft lubricating fluid from the first portion to lubricate an aircraft component. 
         [0006]    An example component lubrication assembly includes a reservoir providing a retention volume. An open, first area of the volume receives a mixture of a fluid that is not deaerated. A second area of the volume receives and holds the fluid that has been deaereated. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0007]    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: 
           [0008]      FIG. 1  is a perspective view of an example rotary wing aircraft. 
           [0009]      FIG. 2  is a perspective view of an example drive system for the  FIG. 1  rotary wing aircraft. 
           [0010]      FIG. 3  is a perspective view of a secondary gearbox within the  FIG. 2  drive system. 
           [0011]      FIG. 4  is a section view in perspective at line  4 - 4  in  FIG. 3 . 
           [0012]      FIG. 5  is a true section view of the  FIG. 4  section view. 
           [0013]      FIG. 6  is a perspective view representing a reservoir volume within the  FIG. 3  secondary gearbox. 
           [0014]      FIG. 7  is a section view at line  4 - 4  in  FIG. 3  in an opposite direction from  FIG. 5 . 
           [0015]      FIG. 8  is a section view at line  8 - 8  in  FIG. 3 . 
           [0016]      FIG. 9  is a perspective view of a nozzle of the  FIG. 3  secondary gearbox. 
           [0017]      FIG. 10  is a perspective view of a portion of the  FIG. 3  secondary gearbox opposite the direction of view in  FIG. 3 . 
           [0018]      FIG. 11  is a section view at line  11 - 11  in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Referring to  FIGS. 1 and 2 , an example high-speed vertical takeoff and landing rotary-wing aircraft  10  has a counter-rotating, coaxial primary rotor system  12  and a secondary rotor system  14 . The aircraft  10  includes an airframe  16  that supports a drive system  18  used to drive the primary rotor system  12  and the secondary rotor system  14 . The primary rotor system  12  rotates about an axis of rotation A. The secondary rotor system  14  rotates about an axis of rotation T. 
         [0020]    The primary rotor system  12  includes an upper rotor assembly  22 A and a lower rotor assembly  22 B. Each rotor assembly  22 A and  22 B includes a plurality of primary rotor blades  24  mounted to a respective upper rotor hub  26 A or lower rotor hub  26 B. The primary rotor blades  24  rotate with the respective hub  26 A or  26 B about the axis A. Any number of blades may be used within the primary rotor system  12 . 
         [0021]    The primary rotor system  12  is driven through a main gearbox  30  by a multi-engine power plant system having an engine package ENG 1  and an engine package ENG 2 . 
         [0022]    The multi-engine power plant system also provides a rotational input into the secondary rotor system  14 . In this example, the secondary rotor system  14  includes a propeller pusher system  34  that provides translational thrust in a direction that is generally parallel to a longitudinal axis L of the aircraft  10 . The secondary rotor system  14  provides thrust for high-speed flight of the aircraft  10 , in this example. 
         [0023]    To rotate the propeller pusher system  34 , a secondary gearbox  38  steps down a rotational input from a main shaft  42  to rotate a secondary drive shaft  44  at a lower speed. The multi-engine power plant system drives the main shaft  42 . 
         [0024]    In this example, the secondary rotor system  14  is mounted to the rear of the airframe  16  with the rotational axis T oriented substantially horizontal and parallel to the axis L. Other configurations of the secondary rotor system  14 , such as a propeller system mounted to each side of the airframe  16  may alternatively be used. 
         [0025]    The following examples are disclosed with reference to the secondary gearbox  38  of the aircraft  10 . Although a particular aircraft and environment is illustrated and described, other configurations, machines, or both may incorporate rotatable components suitable for use with the examples disclosed herein. For example, other moving components, and other gearboxes, may benefit from the following examples. Other types of aircraft, and other types of machines may also benefit. 
         [0026]    Referring now to  FIGS. 3-11  with continuing reference to  FIGS. 1 and 2 , the secondary gearbox  38  includes a secondary driveshaft housing  48  and a gear housing  50 . Fluid, such as a lubricating oil, circulates through the gear housing  50  to cool and lubricate the gears and bearings (not shown) within the gear housing  50 . As known, the fluid becomes mixed with air when cooling and lubricating the gears and bearings. It is further blended and mixed during the fluid recovery process, where the scavenge pumps pull the oil and air in varying proportions from the bottom of the gear cavity. 
         [0027]    Fluid that exits the gear housing  50  is collected and recirculated. However, the reused fluid re-entering the gear housing  50  is typically reasonably void of air content. Fluid mixed with significant amounts of air is less suitable for cooling and lubricating the gears and bearings as is known. Circulation systems employing other details such as control circuits and valves are more sensitive to air content due to the compressibility of that media. 
         [0028]    To remove air from the mixed fluid, the fluid is deaerated prior to circulation back to the gear housing  50 . A person having skill in this art and the benefit of this disclosure would understand how much air would need to be separated from the fluid to make the fluid suitable for lubricating and cooling gears within the gear housing  50 . 
         [0029]    In this example, a nozzle  58  introduces the mixture of fluid and air to the reservoir  54 . The mixture is collected using a scavenge pump within the gear housing  50  and is communicated directly from the gear housing  50  to the reservoir  54 . The manner in which the mixture is introduced to the reservoir  54  encourages air to separate from the fluid. 
         [0030]    The example reservoir  54  includes an outer curved wall  62  and an inner curved wall  64 . The outer wall  62  is “outer” relative to the inner wall  64  with reference to axis T. Radially extending walls  66  and  68  connect the outer wall  62  to the inner wall  64 . Axially facing end walls  70  and  72  complete the reservoir  54 . 
         [0031]    As can be appreciated from the Figures, the outer wall  62  and the inner wall  64  are curved such that a volume established by the reservoir  54  extends circumferentially around a portion of the axis T. Notably, the volume is continuous and uninterrupted. That is, other than the walls, inlet structures, and outlet structures, there are no additional structures or features extending into, or disposed within, the volume of the reservoir. The reservoir  54  is integrated within the secondary driveshaft housing  48 . 
         [0032]    In this example, the radial wall  68  is located at a vertical bottom of the reservoir  54  and the radial wall  66  is located near a vertical top of the reservoir  54 . Relative vertical positions, in this example, refer to the aircraft  10  being on the ground or in straight (or level) flight. Since the aircraft  10  maintains a relatively consistent attitude during flight, the relative vertical positions of the end wall  68  and  66  are maintained during flight. Where flight angles might vary from that vertical orientation, the nature of the coordinated maneuvers generates a G-vector on the fluids that emulates the relative orientation for the fluid volumes. 
         [0033]    Fluid pools at the vertical bottom of the reservoir  54  due to gravity. The wall  68  is thus typically submersed by fluid. The radial wall  66  is, in this example, located vertically above the normal maximum level of fluid held within the reservoir  54 . Accordingly, during normal operation, the wall  66  is in an open area of the reservoir  54 . (The open area is an area without pooled fluid.) Notably, the vertical form of the reservoir  54  improves separation and stratification of varying densities of flow mixture, such as fine air entrainment that can lead to foaming. 
         [0034]    The example radial wall  66  is curved and has a general C-shape. The radial wall  66  is curved relative to an axis C that is parallel to the axis T. 
         [0035]    The nozzle plug  58 , which is aluminum in this example, includes a conduit portion  74  that creates a nozzle jet which directs the mixture from the nozzle  58  in the direction D toward the radial wall  66 . The mixture is introduced into an open area of the reservoir  54 . 
         [0036]    The nozzle  58  receives the mixture from the gear housing  50  via a flow conduit  76 . In this example, the nozzle  58  is located on an opposite axial end of the secondary driveshaft housing  48  from the gear housing  50 , thus the conduit  76  extends axially across the entire length of the reservoir section of the secondary driveshaft housing  48 . 
         [0037]    In this example, the mixture of oil and air from the gear housing  50  is introduced to the reservoir  54  at a relatively high flow rate so that the mixture exits from the nozzle  58  at a suitable velocity and impinges onto the radial wall  66 . The curvature of the radial wall  66  is paired with the flow velocities to ensure suitable centrifugal forces and adequate separation. Notably, the direction D has a vector component D A  that is parallel to the axis C, and a vector component D T  that is tangential to the partial cylinder about axis C ( FIG. 9 ). 
         [0038]    The mixture flows along path P after impinging upon the end wall  66 . The mixture moves tangentially and axially relative to the axis C as the mixture is centrifuged by the contour of the wall. 
         [0039]    Primary separation of the air from the fluid is encouraged by the curved contour and the contact with the curved radial wall  66 . This half-curl centrifuge causes the denser fluid to be flung outward onto the outer wall and coalesced, which displaces the less dense air and prompting it to move inward toward the rotational center of the curved flow. The principally separated and coalesced fluid flows downward within the reservoir  54  along the sloped portion of the wall  66 , against the inner wall  64 , and into the fluid collected at the vertical bottom of the reservoir  54 . The principally separated fluid flows as a widening sheet against the end wall  66  and the inner wall  64 . The progressively widening of the sheet flow permits the flow to get thinner, and further encourages the separation of the finer air bubbles within the principally separated fluid. The increased contact area of the flow reduces its velocity, providing for more peaceful entry into the collected fluid volume. The separated air rises and collects within the open area. 
         [0040]    In this example, the sheet flow improves separation of the fluid and the air. The sheet flow is relatively thin, which shortens the travel path for the air to separate from the fluid. The relatively thin sheet means even smaller bubbles are released compared to thicker layers of flow. Further, the sheet flow, in this example, is spread across a relatively wide surface area, which provides more of a boundary layer against the walls, yields reduced velocity of flow, and eases entry into solid oil volume. Because the entry is eased, there is less agitation related to entry into the separated and collected fluid. Thus, less air is re-introduced. 
         [0041]    Typical prior art deaerators sustain flow velocity thru to discharge, leaving a very active spray and potential for churn, which can introduce air back into the fluid. 
         [0042]    During operation of the secondary gearbox  38 , air collected in the open area of the reservoir  54  vents back to the gear housing  50  through an air conduit  78 . 
         [0043]    During operation of the secondary gearbox, fluid is pumped from a vertical bottom of the reservoir and reintroduced into the gear housing  50 . The reintroduced fluid is used for cooling, lubrication, or both. 
         [0044]    A fluid pump may be used to communicate fluid from the reservoir  54  to the gear housing  50 . Positioning the reservoir fluid outlet  82  (pump inlet) near the vertical bottom of the reservoir  54  further improves separation of the air bubbles from the fluid, and helps lessen the chance that air becomes part of the cooling flow and is reintroduced to the gear housing  50  through the fluid outlet  82 . 
         [0045]    Features of the disclosed examples include introducing a mixture of air and fluid into an open area of a reservoir in a way that encourages the separation of air from the fluid. Notably, no separate deaerating structure is required to encourage such separation. Also, no such separate deaerating structure is positioned within the reservoir. Further, secondary aeration of separated fluid is minimized by easing flow entry into the collected fluid volume. 
         [0046]    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.