Patent Description:
Aircraft engines, such as gas turbine engines, include a lubrication system for distributing a lubricating fluid, such as oil for instance, to portions of the engine. This lubricating oil may be directed to and from a bearing cavity of the aircraft engine, for example. Air may become mixed with the oil due to the compressed air used for pressurizing the bearing cavity, and the amount of air in the lubricating oil may thus increase after the oil has been fed through the bearing cavity. A de-aerator may be used in the lubrication system to remove at least a portion of the air from the oil. In use, such de-aerator may be subject to rotor vibrations, for instance as a result of the turbulent flow of mixed oil and air flowing therethrough. <CIT> relates to an air-oil separator for aerospace lubricant filter disclosing the features of the preamble of claim <NUM>.

In one aspect, there is provided an active de-aerator for an aircraft engine as set forth in claim <NUM>.

In another aspect, there is provided a lubrication system of an aircraft engine as set forth in claim <NUM>.

<FIG> illustrates an aircraft engine <NUM>, such as a gas turbine engine, of a type preferably provided for use in subsonic flight. The gas turbine engine <NUM> generally includes in serial flow communication a fan <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. The fan <NUM>, the compressor section <NUM>, and the turbine section <NUM> are rotatable about a central axis <NUM> of the gas turbine engine <NUM>.

Referring to <FIG> and <FIG>, the gas turbine engine <NUM> includes a lubrication system <NUM> that includes one or more pumps <NUM>, lubrication conduits <NUM> that form a network of conduits, a lubricant reservoir <NUM>, and a de-aerator <NUM>. The lubrication system <NUM> may also include additional components such as valve(s), heat exchangers, filters, etc. The lubricant reservoir <NUM> is hydraulically connected to one or more components C of the engine <NUM> in need of lubrication, such as, for instance, bearing cavity(ies) <NUM>, gearbox(es), and so on. The pump <NUM> is operable to induce a flow of the lubricant from the lubricant reservoir <NUM>, to the one or more components C of the engine <NUM> in need of lubrication. A scavenge pump(s) <NUM> may be present and is operable to draw a scavenge flow of oil back to the reservoir <NUM>. The scavenge pump <NUM> has an inlet hydraulically connected to a scavenge outlet C1 of the component C and an outlet hydraulically connected to the de-aerator <NUM>. In some cases, for instance when the component C is a bearing cavity <NUM>, the oil flows through the bearing cavity <NUM> and is mixed with compressed air injected therein for pressurizing the bearing cavity <NUM>. The oil mixture exiting the bearing cavity <NUM> may thus have a greater air content than the oil mixture entering the bearing cavity <NUM>. The de-aerator <NUM> is operable to remove at least a portion of the air contained within the air-oil mixture it receives before flowing the oil back to the one or more components in need of lubrication. The de-aerator <NUM> has an air-oil inlet 130a hydraulically connected to the scavenge outlet C1 of the component C via the scavenge pump <NUM>; an oil outlet 130b hydraulically connected to the reservoir <NUM> for returning the de-aerated oil back to the reservoir <NUM>; and an air outlet 130c hydraulically connected to a vent <NUM> for expelling the air out to an environment E outside of the gas turbine engine <NUM>. It will be appreciated that the location of some of the parts of the lubrication system <NUM> (e.g., scavenge pump <NUM>, pump <NUM>, vent <NUM>) may differ from what is illustrated in <FIG>. For instance, the scavenge pump <NUM> and the active de-aerator <NUM> may be integrally part of a same pumping system or pumping unit, with the flow passage in between them illustrated in <FIG> defined as part of the scavenge pump <NUM> and/or de-aerator <NUM>.

Any suitable arrangement of the lubrication system <NUM> is contemplated. The de-aerator <NUM> may be included in any lubrication systems.

Referring now to <FIG>, an active de-aerator <NUM>, which may operate as the de-aerator <NUM> in the lubrication system <NUM> of <FIG>, is illustrated according to an embodiment. The de-aerator <NUM> is an "active" de-aerator since it has at least one component (e.g., impeller) that is driven, such as by electrical and/or pneumatic and/or hydraulic or other means (motors, actuators, etc.). A de-aerator is different than a de-oiler. A de-oiler is typically located within a lubricated cavity (e.g., gear box) and is designed to remove oil (e.g., oil droplets/mist) within an air-oil mixture before ejecting air overboard. The de-aerator <NUM> is designed to extract air from an air-oil mixture and to feed oil back to the lubrication system <NUM>. Typically, the de-oiler does not include a housing. In contrast, the housing of the de-aerator <NUM> is used to collect the oil extracted by centrifugation so that the extracted oil is flown back to the oil system. Since the de-oiler is located within the lubricated cavity, it does not need a housing and the oil may simply be ejected via centrifugation against the components in need of lubrication contained within the lubricated cavity (e.g., gears).

In the depicted embodiment, and referring to <FIG>, the active de-aerator <NUM> is driven by an oil pump <NUM>. In the depicted embodiment the active de-aerator <NUM> is part of the oil pump <NUM>. In other words, the active de-aerator <NUM> is "built-in" with the oil pump <NUM>, or retrofitted into the oil pump <NUM>. Although shown in isolation in <FIG>, the oil pump <NUM> and active de-aerator <NUM> may function as the scavenge pump <NUM> and de-aerator <NUM> schematically illustrated in <FIG>. In an embodiment, the oil pump <NUM> driving the de-aerator <NUM> in <FIG> may be a scavenge pump, such as pump <NUM> of <FIG>.

As shown in <FIG>, the oil pump <NUM> has a housing H receiving components forming parts of the active de-aerator <NUM>. In other embodiments, the active de-aerator <NUM> may be configured as a standalone device that is coupled to an oil pump, or coupled to any device able to generate a rotational input to the de-aerator <NUM> in yet other embodiments. For instance, the rotational input may be provided by an electric motor, or a shaft of the gas turbine engine <NUM> (<FIG>). As shown, the housing H includes a first housing section H1 and a second housing section H2 securable to each other. The first and second housing sections H1, H2 defines a cavity HC (best seen in <FIG>). A seal(s) S may be provided at an interface between the first and second housing sections H1, H2 to limit leakage of fluid at the interface. In some embodiments, the cavity HC is a sealed cavity, with one or more inlets and outlets allowing fluid flow communication with the sealed cavity.

The oil pump <NUM> includes flow inducing means <NUM>. In this embodiment, the flow inducing means <NUM> are intermeshing gears disposed within a flow path of the pump <NUM> and inducing fluid flow by mutual rotation. Depending on the pump, one or more flow inducing means may be mounted serially or in parallel with one another to form one or more pump stages. The flow inducing means (all or some) may be mounted to a pump shaft <NUM> for rotation therewith. As another example, the flow inducing means <NUM> are blades, etc..

The active de-aerator <NUM> includes an impeller <NUM>. The impeller <NUM> is received within the housing H and may rotate relative to the housing H about a central axis A.

The impeller <NUM> is enclosed within the cavity HC defined by the first and second housing sections H1, H2. The impeller <NUM> has a shaft connecting portion 132a that is drivingly engageable to the oil pump shaft <NUM> for receiving a rotational input therefrom. As shown, the shaft connecting portion 132a extends axially along central axis A, e.g., concentrically. As shown in <FIG>, the shaft connecting portion 132a defines an annular body protruding axially from a remainder of the impeller <NUM>. The shaft connecting portion 132a defines a hollow space SH having sections of different bore sizes sized to receive a complementary end of the pump shaft <NUM>. Other shapes of hollow space for connecting with an end of the pump shaft <NUM> may be contemplated. In the depicted embodiment, the shaft connecting portion 132a and an end 142a of the pump shaft <NUM> have complementary splines SP (see <FIG>) for mutual axial engagement, as a possibility among others to rotatably couple them. The shaft connecting portion 132a and the end of the pump shaft <NUM> may thus be drivingly engaged to each other such that rotational input provided by the pump shaft <NUM> may induce rotation of the impeller <NUM>. The housing H, here housing section H1, defines a bore BH1 supporting the shaft connecting portion 132a. At least part of the shaft connecting portion 132a may be received within the bore BH1.

The impeller <NUM> has a rim 132b, which may be referred to as a ring portion and blades 132c that are circumferentially distributed around the central axis A. The rim 132b extends circumferentially around the central axis A and around the blades 132c. In the embodiment shown, the blades 132c are secured to a fore flange 132d that is secured to the shaft connecting portion 132a and to an aft flange 132e, e.g., they may be a monoblock piece. Both of the first and second flanges 132d, 132e are annular and extend all around the central axis A. The fore flange 132d is used to redirect a flow of oil that enters the de-aerator <NUM> in a substantially axial direction relative to the central axis A to a substantially radial direction relative to the central axis A before the flow of oil meets the blades 132c. The blades 132c have radially inner ends 132f and radially outer ends <NUM>. In the embodiment shown, the radially outer ends <NUM> of the blades 132c are secured to the rim 132b of the impeller <NUM>. In the embodiment shown, the blades 132c and the rim 132b are integral and are defined as a single part, though other constructions are possible. The radially inner ends 132f of the blades 132c are located axially between the fore and aft flanges 132d, 132e.

The flow of mixed air-oil passing through the impeller <NUM> may be turbulent and may create uneven loads as a density of the oil or air within the mixture may continuously vary over instant times. Such uneven loads may induce vibrations. Vibrations and/or shaft impeller shaft deflection may be limited by proper supporting means and configuration within the housing H. In the depicted embodiment, a periphery of the shaft connecting portion 132a and a surface of the bore BH1 facing the periphery of the shaft connecting portion 132a define a journal bearing JB1. A film of oil or other lubricant may be present between the surface of the bore BH1 facing the periphery of the shaft connecting portion 132a and the periphery of the shaft connecting portion 132a. The bore BH1 may thus be referred to as a portion of the housing H supporting the impeller <NUM> and/or as defining part of the journal bearing JB1. The journal bearing JB1 may be defined by a separate part interfacing with the bore BH1 and the periphery of the shaft connecting portion 132a in other embodiments. For instance, the journal bearing JB1 may be an annular insert slidingly engaged within the bore BH1, which may be replaced when worn out. The active de-aerator <NUM> has an inlet side I and an opposed outlet side O, which may respectively be referred to as a fore side and an aft side. As opposed to being cantilevered from the end of the pump shaft <NUM>, the impeller <NUM> is further supported on the outlet side O. As shown, the impeller <NUM> is rotatably supported within the housing H, here second housing section H2, via another journal bearing JB2. As discussed above, the bore BH1 and the shaft connecting portion 132a of the impeller define the journal bearing JB1, which may be referred to as a first journal bearing for rotatably supporting the shaft connecting portion 132a of the impeller <NUM> on the inlet side I. The impeller <NUM> may thus be supported by a pair of journal bearings JB1, JB2 disposed respectively on the inlet and outlet sides I, O of the impeller <NUM>, as opposed to being cantilevered to the pump shaft <NUM>, for instance. The dual journal bearings JB1, JB2 mounting of the impeller <NUM> within the housing H may increase stability and/or reduce shaft deflection.

The housing H, here the second housing section H2, defines a bore BH2. In the depicted embodiment, the bore BH2 is concentric with the bore BH1 discussed above. The bore BH2 is surrounded by an annular wall BHW. In the depicted embodiment, the second flange 132e defines a flange wall <NUM> extending axially along the central axis A. The flange wall <NUM> has a surface facing an outer periphery of the annular wall BHW. As shown, the journal bearing JB2 on the outlet side O of the impeller <NUM> is defined by the flange wall <NUM> and the annular wall BHW. A film of lubricant of the journal bearing JB2, between the flange wall <NUM> and the annular wall BHW may allow lower friction to facilitate rotation. The bore BH2 is thus referred to as another portion of the housing H supporting the impeller <NUM> and as defining part of the journal bearing JB2. Stated differently, the bores BH1, BH2 are two portions of the housing H that contribute to the support of the impeller <NUM> and that are adapted to allow rotation of the impeller <NUM> within the housing H.

The journal bearing JB2 may also be a separate part interfacing between the flange wall <NUM> and the annular wall BHW in other embodiments. For instance, the journal bearing JB2 may be an annular insert slidingly engaged around the annular wall BHW, which may be replaced when worn out.

The flange wall <NUM> may be located radially inwardly relative to the annular wall BHW in other examples, such that the journal bearing JB2 may be defined between an outer periphery of the flange wall <NUM> and an inner periphery of the annular wall BHW, for instance.

In the depicted embodiment, the journal bearings JB1, JB2 are delimited (delimited or defined) by cylindrical (cylindrical or substantially cylindrical) surfaces facing each other. Also, as shown, such cylindrical surfaces are extending substantially in an axial direction along central axis A. The journal bearings JB1, JB2 may be defined by uneven surfaces and/or between surfaces angled (or "oblique") relative to the central axis A in other embodiments. For instance, the journal bearings JB1, JB2 may be conical when viewed in a cross-section as in <FIG>.

The air-oil inlet 130a of the active de-aerator <NUM> is located on the inlet side I; and the oil outlet 130b and the air outlet 130c are located on the outlet side O of the de-aerator <NUM>. In the embodiment shown, the air-oil inlet 130a, the oil outlet 130b, and the air outlet 130c are defined by the housing H. In operation, for separating the air from the air-oil flow, the air-oil mixture is received via the air-oil inlet 130a of the de-aerator <NUM> in a generally axial direction relative to the central axis A of the impeller <NUM>. The received air-oil flow is redirected in a radial direction relative to the central axis A and the air is separated from the air-oil flow by centrifugation within the impeller <NUM>. Stated differently, oil is directed radially outward of the second flange 132e by centrifugal forces and follows the path to the oil outlet 130b. Air may on the other hand follow the more central path to flow instead to the air outlet 130c. The extracted air may thus be expelled out from the impeller <NUM> at a radially inward location relative to the oil flowing out from the impeller <NUM>. The journal bearings JB1, JB2 are hydraulically connected with the air-oil inlet 130a and the oil outlet 130b, which may allow constant lubrication of the journal bearings JB1, JB2 in operation. Oil leaking from the journal bearings JB1, JB2 may thus be flushed with the air-oil mixture as the air-oil flow passes through the impeller <NUM> and/or flushed with the oil exiting the impeller <NUM> via the oil outlet 130b. Such dual journal bearings JB1, JB2 mounting of the impeller <NUM> may thus be advantageous in the context of oil and/or air-oil environment, whereas such dual journal bearings JB1, JB2 mounting of impeller <NUM> may not be desirable in other environment without such oil or air-oil interaction.

The impeller <NUM> may further have a tube 132i connected to the second flange 132e. As shown, the tube 132i is integral with the second flange 132e. The tube 132i is concentric with the central axis A. The tube 132i has an internal passage P4 which is fluidly connected to the air outlet 130c. The separated air from the mixture of air-oil may thus be channeled through the tube 132i and expelled into the air outlet 130c. The tube 132i defines an axial end of the impeller <NUM> that is opposite the shaft connecting portion 132a discussed above. The tube 132i is located on one axial side of the blades 132c of the impeller <NUM>, opposite to the axial side of the blades 132c where the shaft connecting portion 132a is located. In the depicted embodiment, at least part of the tube 132i is radially aligned with the journal bearing JB2 along the central axis A.

The tube 132i is received within the bore BH2. A seal(s), here a lip seal LS, interfaces with a periphery of the tube 132i and the wall BHW of the bore BH2. As shown, the lip seal LS is secured between the outer periphery of the tube 132i and an inner periphery of the wall BHW. The lip seal LS may prevent or limit oil leakage through the air outlet 130c, which may in turn limit oil contamination of the air outlet 130c and other components downstream thereof, if applicable. The lip seal LS is typically resilient and/or flexible to allow proper sealing at the interface of opposite surfaces (here radial surfaces). While the lip seal LS interfaces between the tube 132i and the wall BHW, it may not serve the function of radially supporting the impeller <NUM>, as opposed to the journal bearings JB1, JB2 discussed above, as the lip seal LS may radially deflect, for instance as a result of its low radial rigidity and/or its geometry. The journal bearings JB1, JB2 typically allow for a limited radial deflection, as a consequence of the gap sized to allow a thin film of lubricant between the journal bearings surfaces. For instance, in an embodiment, a radial dimension of the gap and/or lubricant film is between <NUM> to <NUM> inch (<NUM> to <NUM>). Other types of seals may be contemplated in other embodiments.

In the depicted embodiment, the journal bearing JB2 is radially outward relative to the lip seal LS. The journal bearing JB2 is fluidly connected to the oil outlet 130b radially outward from the lip seal LS, while the lip seal Ls may prevent or at least limit interaction of the air flowing out from the impeller <NUM> through the tube 132i with the journal bearing JB2. The lip seal LS may thus act as a "air barrier" between the tube 132i by which air may exit the impeller <NUM> and the journal bearing JB2. While the journal bearing JB2 is located between the outer periphery of the wall BHW and the inner periphery of the flange wall <NUM> in the embodiment shown, the journal bearing JB2 may be disposed at the location of the lip seal LS in other embodiments. For instance, the journal bearing JB2 in embodiments that are not shown herein may be between the outer periphery of the tube 132i and the inner periphery of the wall BHW, in series with the lip seal LS, if the lip seal LS is present in such embodiments.

Referring to <FIG>, a plurality of flow passages P are defined circumferentially between each two circumferentially adjacent ones of the blades 132c. The flow passages P have passage inlets P1 extending radially between a periphery of the first flange 132d and the rim 132b, extending circumferentially between each two adjacent ones of the blades 132c, and extending axially between the rim 132b and the fore flange 132d. In the depicted embodiment, the inlets P1 of the flow passages P face a direction which has a radial component relative to the central axis A. In the embodiment shown, the radial component of the inlets P1 of the flow passages P is oriented away from the central axis A. The flow passages P have air outlets P2 proximate the central axis A. The air outlets P2 of the flow passages P are defined circumferentially between each of two adjacent ones of the radially inner ends 132f of the blades 132c and axially between the fore and aft flanges 132d, 132e.

The flow passages P further have oil outlets P3 located axially between an axial end of the rim 132b and the aft flange 132e. More specifically, a portion 132c1 of the blades 132c extends radially beyond and curves around a radially outer edge of the aft annular flange 132e when viewed in a cross-section as in <FIG>. The portions 132c1 of the blades 132c that extend radially outwardly around the aft flange 132e have radially inner ends 132c2 that are located on a downstream side of the aft flange 132e. The oil outlets P3 are defined circumferentially between each two adjacent ones of the radially inner ends 132c2 of the portions 132c1 of the blades 132c.

The flow passages P further include the internal passage P4 defined by the hollow tube 132i. The internal passage P4 is fluidly connected to the air outlets P2 of the flow passages P defined between the blades 132c of the impeller <NUM>.

In use, an air-oil mixture is received into the de-aerator <NUM> via the air-oil inlet 130a along arrow A1. The oil is diverted radially outwardly away from the central axis A by the fore flange 132d. The oil is then divided between the flow passages P upon rotation of the fore flange 132d and enters those flow passages P via their respective inlets P1. The oil is then impinged by the blades 132c of the impeller <NUM>. Such impingement may cause separation of the air contained in the air-oil mixture from the oil. The separated oil flows within the flow passages P defined between the blades 132c, around the periphery of the second flange 132e along arrow A2 and exits the flow passages P via the oil outlet P3 defined axially between the aft flange 132e and the rim 32b and circumferentially between the radially-inner ends 132c2 of the portions 132c1 of the blades 132c that extend aft of the aft flange 132e. The oil then exits the de-aerator <NUM> via the oil outlet 130b thereof along arrow A3. As shown in <FIG>, the extracted oil is then flown back to the reservoir <NUM>, through which it is circulated to the components (e.g., bearing cavity <NUM>) in need of lubrication. The air extracted from the air-oil mixture flows around a periphery of the first flange 132d along flow path A4, moves radially inwardly toward the central axis A, and exits the flow passages P via their air outlets P2 defined circumferentially between the radially-inner ends 132f of the portions of the blades 132c that are located between the fore and aft flanges 132d, 132e. The extracted air then flows into the passage P4 of the hollow tube 132i along arrow A5 and out of the de-aerator <NUM> via the air outlet 130c.

Claim 1:
An active de-aerator (<NUM>) for an aircraft engine (<NUM>), comprising:
a housing (H) having an air-oil inlet (130a), an oil outlet (130b) and an air outlet (130c);
an impeller (<NUM>) received within and rotatable relative to the housing (H) about a central axis (A);
a first journal bearing (JB1) on a first side of the impeller (<NUM>) for rotatably supporting the impeller (<NUM>) relative to the housing (H); and
a second journal bearing (JB2) on a second side of the impeller (<NUM>) for rotatably supporting the impeller (<NUM>) relative to the housing (H), the second side being opposite the first side; wherein
the housing (H) has a portion defining a first bore (BH1) supporting the impeller, characterized by
the housing also defining a second bore (BH2) defining an annular wall (BHW), the first and second bores (BH1, BH2) located respectively on the first and the second sides of the impeller (<NUM>), the impeller (<NUM>) defining a tube (132i) extending along the central axis (A) and received within the second bore (BH2) and a flange wall (<NUM>) extending about the tube (132i) and axially along the central axis (A), the annular wall (BHW) located radially between the tube (132i) and the flange wall (<NUM>), a seal (LS) interfacing with a periphery of the tube (132i) and an inner periphery of the annular wall (BHW), the flange wall (<NUM>) and an outer periphery of the annular wall (BHW) defining the second journal bearing (JB2).