# Patent

## Title
Deaerator outlet diffuser

## Abstract

A deaerator includes a case defining a vortex chamber and a fluid inlet for allowing a mixture of lubricating liquid and air to pass through the case into the vortex chamber. An air outlet allows air flow out of the deaerator, and a liquid outlet allows lubricating liquid flow out of the deaerator. A porous diffuser is positioned proximate the liquid outlet for slowing the flow of lubricating liquid.

## Background
BACKGROUND
The present invention relates to lubrication systems, and in particular, to a deaerator for a lubrication system.
Certain lubrication systems function in a way that allows air to enter and be mixed with flow of lubricating liquid. Because it can be undesirable to have air in the lubricating liquid, deaerators are often used to separate air from lubricating liquid. For example, in gas turbine engines, lubrication systems typically use a deaerator to separate a scavenged mixture of air and lubricating liquid and to return the lubricating liquid to a reservoir for later use. It is desirable for the deaerator to supply the lubricating liquid to the reservoir with few or no air bubbles entrained in the lubricating liquid.
However, if the lubricating liquid leaves the deaerator at a relatively fast speed, that flow of lubricating liquid can agitate the surface of the lubricating liquid already in the reservoir, undesirably adding air bubbles to the lubricating liquid. A deaerator can be designed large enough that the lubricating liquid moves relatively slowly when it leaves the deaerator, but a large deaerator adds undesirable weight and also takes up valuable space.
SUMMARY
According to the present invention, a deaerator includes a case defining a vortex chamber and a fluid inlet for allowing a mixture of lubricating liquid and air to pass through the case into the vortex chamber. An air outlet allows air flow out of the deaerator, and a liquid outlet allows lubricating liquid flow out of the deaerator. A porous diffuser is positioned proximate the liquid outlet for slowing the flow of lubricating liquid.
Another embodiment of the present invention is a method of deaerating a lubricating liquid. The method includes flowing a mixture of lubricating liquid and air from a plurality of gas turbine engine components into a vortex chamber of a deaerator, separating air from lubricating liquid in the vortex chamber, flowing separated lubricating liquid through a porous diffuser to a lubricating liquid reservoir, and flowing separated air through an air outlet to flow out of the deaerator. The flow of separated air bypasses the porous diffuser.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a gas turbine engine having a lubrication system.
FIG. 2 is a perspective sectional view of a reservoir and deaerator of the lubrication system of FIG. 1.
FIG. 3A is a perspective sectional view of an embodiment of the deaerator of FIG. 2.
FIG. 3B is a perspective sectional view of another embodiment of the deaerator of FIG. 2.
FIG. 4A is a perspective view an embodiment of a diffuser for use with the deaerator of FIG. 2.
FIG. 4B is a perspective view of another embodiment of a diffuser for use with the deaerator of FIG. 2.



DETAILED DESCRIPTION
FIG. 1 is a schematic view of gas turbine engine 10 having lubrication system 12. Lubrication system 12 includes reservoir 14, deaerator 16, supply passage 18, scavenge passage 20, supply pump 22, and scavenge pump 24. Supply pump 22 pumps a lubricating liquid, such as oil, from reservoir 14 to engine components 26A and 26B to cool and lubricate engine components 26A and 26B. Engine components 26A and 26B can be virtually any components on gas turbine engine 10 that benefit from lubricating liquid, such as gears and bearings. Scavenge pump 24 pumps lubricating liquid from engine components 26A and 26B and returns it to deaerator 16 in reservoir 14. Scavenge pump 22 can be sized and configured so as to scavenge air in engine components 26A and 26B in addition to the lubricating liquid. Consequently, a mixture of lubricating liquid and air is passed through fluid inlets 28 of deaerator 16.
Deaerator 16 separates the lubricating liquid from the air, passing the air out through air outlet 30 to the exterior of reservoir 14 and passing the lubricating liquid thorough liquid outlets 32 to interior cavity 34 of reservoir 14. Interior cavity 34 is defined by reservoir wall 36.
In the illustrated embodiment, deaerator 16 has a substantially cylindrical shape. Air outlet 30 is a single outlet on a top of deaerator 16. Fluid inlets 28 include four inlets (two of which are shown in FIG. 1) equally spaced around a perimeter of deaerator 16 near the top of deaerator 16. Fluid inlets 28 are arranged and shaped to impart high speed rotation of the air and oil mixture inside of deaerator 16. Liquid outlets 32 include four outlets (two of which are shown in FIG. 1) equally spaced around a perimeter of deaerator 16 near a bottom of deaerator 16. In alternative embodiments, deaerator 16 can have a different shape, and air outlet 30, fluid inlets 28, and liquid outlets 32 can be included in different numbers and positions as suitable for a particular application. Moreover, lubrication system 12 can also be different, having one or more additional or different connections or components, such as valves, filters, sensors, heat exchangers, etc.
FIG. 2 is a perspective sectional view of reservoir 14 and deaerator 16. Deaerator 16 is installed in socket 40 of reservoir 14 and held in place by retaining ring 42. In the illustrated embodiment, deaerator 16 is positioned substantially inside interior cavity 34 of reservoir 14. In an alternative embodiment, deaerator 16 can be positioned only partially inside interior cavity 34 of reservoir 14.
O-rings 44A and 44B provide seals between socket 40 and cylindrical case 46 of deaerator 14. Inlet plenum 48 is positioned between socket 40 and case 46, sealed by o-ring 44A on top and o-ring 44B on bottom. Inlet plenum 48 receives the mixture of air and lubricating liquid from scavenge passage 20 prior to flowing it through fluid inlets 28 and into vortex chamber 50. Vortex chamber 50 is bounded and defined by inner surface 52 of case 46. Vortex regulator plate 56 is positioned in vortex chamber 50 between fluid inlet 28 and liquid outlet 32. Vortex chamber 50 is separated from bottom chamber 54 by vortex regulator plate 56. Deaerator top 58 provides a top for deaerator 16 and for vortex chamber 50. Deaerator bottom 60 provides a bottom for deaerator 16 and bottom chamber 54. A radial gap between vortex regulator plate 56 and inner surface 52 allows a space for liquid flow from fluid inlets 28 to liquid outlets 32. Vortex regulator plate 56 limits air flow from fluid inlets 28 to liquid outlets 32. Air passage 62 is a substantially cylindrical passage positioned in a center of vortex chamber 50 and includes air inlets 64. Air inlets 64 allow air to flow from vortex chamber 50 through air passage 62 and out air outlet 30. Air passage 62 and vortex regulator plate 56 are spaced from deaerator bottom 60 by center support 66.
Diffuser 68 is positioned in bottom chamber 54. Diffuser 68 is a porous diffuser, having pores 70. In the illustrated embodiment, diffuser 68 is positioned at a bottom of bottom chamber 54, with space between diffuser 68 and vortex regulator plate 56. In an alternative embodiment, diffuser 68 can fill substantially all of the space in bottom chamber 54 between deaerator bottom 60 and vortex regulator plate 56. Diffuser 68 has a substantially toroidal shape, with center support 66 positioned in a center of diffuser 68.
In operation, the mixture of lubricating liquid and air flows from scavenge passage 20, through inlet plenum 48, and through fluid inlets 28 into vortex chamber 50. Fluid inlets 28 are angled and aligned substantially tangentially with inner surface 52 of case 46 so as to induce vortex flow in vortex chamber 50. This vortex flow is induced without having to spin deaerator 16, which is substantially stationary with respect to the vortex flow within. That vortex flow separates the mixture of air and lubricating liquid, thus forcing separated air toward a center of vortex chamber 50 and forcing separated lubricating liquid toward a perimeter of vortex chamber 50. The separated air flows through air inlets 64, through air passage 62, and out air outlet 30 to a space outside of deaerator 16 and reservoir 14. Air flows directly from vortex chamber 50 to air passage 62, bypassing bottom chamber 54 and diffuser 68. The separated lubricating liquid flows through the space between vortex regulator 56 and inner surface 52, into bottom chamber 54, thorough diffuser 68, and then out liquid outlets 32 into interior cavity 34 of reservoir 14.
Parts of deaerator 16, including fluid inlets 28 and vortex chamber 50, can be sized and shaped to cause relatively fast fluid flow in vortex chamber 50. This causes the separated lubricating liquid passing through the space between vortex regulator 56 and inner surface 52 of case 46 to also flow relatively fast. The porous structure of diffuser 68 can slow the flow of the separated lubricating liquid as it passes through diffuser 68. This allows deaerator 16 to deliver separated lubricating liquid to reservoir 14 at a relatively slow flow speed. This can be particularly beneficial in situations where the liquid level in reservoir 14 is at or below liquid outlets 32. In such situations, a relatively fast flow of lubricating liquid from deaerator 16 could agitate the surface of the lubricating liquid in reservoir 14, undesirably adding air bubbles to the lubricating liquid in reservoir 14. Thus, use of diffuser 68 to reduce flow speed results in a reduced risk of agitation and a reduced risk of adding air bubbles. Because diffuser 68 can reduce such flow speeds, it allows for deaerator 16 to be designed as a relatively small and high speed deaerator. This can result in weight and space savings.
For example, deaerator 16 can be designed with a length to diameter ratio less than 7:1, such as about 4:1. In the illustrated embodiment, deaerator 16 has a diameter of about 2 inches (about 5 centimeters) and a height of about 8 inches (about 20 centimeters). Diffuser 68 also has a diameter of about 2 inches (about 5 centimeters) and a height of about 0.5 inches (about 1.3 centimeters). In alternative embodiments, deaerator 16 and diffuser 68 can have different sizes and shapes as suitable for a particular application.
FIG. 3A is a perspective sectional view of one embodiment of deaerator 16. Diffuser 68 is positioned inside of deaerator 16 between fluid inlets 28 and liquid outlets 32. Liquid outlets 32 is illustrated in FIG. 3A in phantom, behind diffuser 68.
FIG. 3B is a perspective sectional view of another embodiment of deaerator 16. In this embodiment, diffuser 68 is replaced with diffuser 68′. Diffuser 68′ is similar to diffuser 68 except that diffuser 68′ is larger and is positioned outside of deaerator 16, adjacent liquid outlets 32 on an outer surface of case 46. Accordingly, liquid outlets 32 are fluidically positioned between fluid inlets 28 and diffuser 68′. Liquid outlets 32 are physically positioned through case 46 of diffuser 68 between deaerator top 58 and deaerator bottom 60, nearer to deaerator bottom 60. In the embodiments illustrated in both FIG. 3A and FIG. 3B, both of diffusers 68 and 68′ are positioned proximate liquid outlets 32 for diffusing and slowing the flow of lubricating liquid.
FIG. 4A is a perspective view of an embodiment of diffuser 68 for use with deaerator 16. In the embodiment of FIG. 4A, diffuser 68 is a metal mesh foam having numerous pores 70. Pores 70 are interconnected, allowing and slowing flow through the foam material of diffuser 68. The embodiment of diffuser 68 shown in FIG. 4A is substantially the same as that illustrated in FIGS. 2 and 3A. Diffuser 68′ (shown in FIG. 3B) is also made of a metal mesh foam, but is sized larger than diffuser 68.
FIG. 4B is a perspective view of diffuser 68′′, which is similar to diffuser 68 of FIG. 4A, except diffuser 68′′ is made from wire screen 72 rolled in a spiral shape. When wire screen 72 is rolled in a spiral shape, it effectively results in diffuser 68′′ having a substantially toroidal shape. Wire screen 72 includes a matrix of crossing wires 74. When wire screen 72 is rolled in a spiral shape, diffuser 68′′ effectively has numerous interconnected pores, allowing and slowing flow through diffuser 68′′. The embodiment of diffuser 68′′ shown in FIG. 4B is sized and shaped to replace diffuser 68 as illustrated in FIGS. 2 and 3A. Diffuser 68′′ can also be resized to replace diffuser 68′ as shown in FIG. 3B.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims. For example, a diffuser need not necessarily be made of a metal mesh foam or a wire screen, but could in other embodiments be made of another suitably porous material.

## Claims

1. A lubrication system, comprising:
a reservoir having an interior cavity for holding lubricating liquid; and
a deaerator positioned at least partially inside the interior cavity, the deaerator comprising:
a fluid inlet for receiving a mixture of lubricating liquid and air to be deaerated;
an air outlet for allowing air flow out of the deaerator;
a liquid outlet connecting the deaerator to a portion of the interior cavity outside of the deaerator; and
a porous diffuser positioned proximate the liquid outlet for slowing the flow of lubricating liquid.

2. The lubrication system of claim 1, and further comprising:
a supply passage connecting the reservoir to a supply pump;
a scavenge passage connecting the fluid inlet to a scavenge pump; and
a plurality of gas turbine engine components connected to both the supply pump and the scavenge pump via the supply passage and the scavenge passage, respectively.

3. The lubrication system of claim 1, wherein the porous diffuser has a substantially toroidal shape.

4. The lubrication system of claim 1, wherein the porous diffuser is positioned inside the deaerator between the fluid inlet and the liquid outlet.

5. The lubrication system of claim 1, wherein the porous diffuser is positioned outside the deaerator, adjacent the liquid outlet.

6. The lubrication system of claim 1, wherein the porous diffuser comprises a metal mesh foam.

7. The lubrication system of claim 1, wherein the porous diffuser comprises a wire screen rolled in a spiral shape.

8. A deaerator, comprising:
a case defining a vortex chamber;
a fluid inlet for allowing a mixture of lubricating liquid and air to pass through the case into the vortex chamber;
an air outlet for allowing air flow out of the deaerator;
a liquid outlet for allowing lubricating liquid flow out of the deaerator; and
a porous diffuser positioned proximate the liquid outlet for slowing the flow of lubricating liquid;
wherein the porous diffuser is positioned outside the deaerator, adjacent the liquid outlet.

9. The deaerator of claim 8, and further comprising:
a vortex regulator plate positioned in the vortex chamber between the fluid inlet and the liquid outlet.

10. The deaerator of claim 9, wherein a radial gap is disposed between the vortex regulator plate and an inner surface of the case.

11. The deaerator of claim 8, wherein the fluid inlet is one of a plurality of fluid inlets aligned substantially tangentially with an inner surface of the case.

12. The deaerator of claim 8, wherein the case is substantially cylindrical.

13. The deaerator of claim 8, wherein the porous diffuser has a substantially toroidal shape.

14. The deaerator of claim 8, wherein the porous diffuser is positioned inside the deaerator between the fluid inlet and the liquid outlet.

15. The deaerator of claim 8, wherein the porous diffuser comprises a metal mesh foam.

16. The deaerator of claim 8, wherein the porous diffuser comprises a wire screen rolled in a spiral shape.

17. A method of deaerating a lubricating liquid, the method comprising:
flowing a mixture of lubricating liquid and air from a plurality of gas turbine engine components into a vortex chamber of a deaerator;
separating air from lubricating liquid in the vortex chamber;
flowing separated lubricating liquid through a porous diffuser to a lubricating liquid reservoir; and
flowing separated air through an air outlet to flow out of the deaerator, bypassing the porous diffuser.

18. The method of claim 17, and further comprising:
flowing the separated lubricating liquid through a space between a vortex regulator and an inner surface of the vortex chamber prior to flowing the separated lubricating liquid through the porous diffuser.

19. The method of claim 17, wherein air is separated from lubricating liquid by virtue of the mixture of lubricating liquid and air flowing through one or more deaerator inlets angled so as to induce vortex flow in the vortex chamber whereby the air is forced toward a center of the vortex chamber and the lubricating liquid is forced toward a perimeter of the vortex chamber.