Patent Description:
Electric machines generate heat during operation. Accordingly, even when mounted in a cold section of an aircraft engine, it may be necessary to provide cooling to the electric machine. A system and method for cooling an electric machine would be useful. <CIT> discloses plug in fluid cooled electrical connections for a tail cone mounted generator.

The present invention relates to a gas turbine engine comprising an electric machine, according to claim <NUM>. The gas turbine engine defines a radial direction, an axial direction, and an axis extending along the axial direction of the gas. The gas turbine engine includes: a shaft configured to rotate about the axis; an electric machine comprising a rotor coupled to and rotatable with the shaft and a stator, the rotor defining an end along the axial direction; and a cooling manifold rotatable with the rotor and positioned at the end of the rotor, the cooling manifold configured to receive a flow of cooling fluid and provide the cooling fluid to the stator during operation of the gas turbine engine.

For example, the approximating language may refer to being within a <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> percent margin.

Referring now to the Drawings, <FIG> shows an elevational cross-sectional view of an exemplary embodiment of a gas turbine engine as may incorporate one or more inventive aspects of the present disclosure. In particular, the exemplary gas turbine engine of <FIG> is a configured as a single unducted rotor engine <NUM> defining an axial direction A, a radial direction R, and a circumferential direction C (extending about the axial direction A). As is seen from <FIG>, engine <NUM> takes the form of an open rotor propulsion system and has a rotor assembly <NUM> which includes an array of airfoils arranged around a central longitudinal axis <NUM> of engine <NUM>, and more particularly includes an array of rotor blades <NUM> arranged around the central longitudinal axis <NUM> of engine <NUM>. Moreover, as will be explained in more detail below, the engine <NUM> additionally includes a non-rotating vane assembly <NUM> positioned aft of the rotor assembly <NUM> (i.e., non-rotating with respect to the central axis <NUM>), which includes an array of airfoils also disposed around central axis <NUM>, and more particularly includes an array of vanes <NUM> disposed around central axis <NUM>. The rotor blades <NUM> may be arranged in typically equally spaced relation around the centerline <NUM>. The rotor assembly <NUM> further includes a hub <NUM> located forward of the plurality of rotor blades <NUM>.

Referring still to <FIG>, the vane assembly <NUM> extends from the cowl <NUM> and is positioned aft of the rotor assembly <NUM>. The vanes <NUM> of the vane assembly <NUM> may be mounted to a stationary frame or other mounting structure and do not rotate relative to the central axis <NUM>. For reference purposes, <FIG> also depicts the forward direction with arrow F, which in turn defines the forward and aft portions of the system. As shown in <FIG>, the rotor assembly <NUM> is located at a forward end of the engine <NUM> in a "puller" configuration.

Additionally, the engine <NUM> includes a turbomachine <NUM> having a core (or high speed system) <NUM> and a low speed system. The core <NUM> generally includes a high-speed compressor <NUM>, a high speed turbine <NUM>, and a high speed shaft <NUM> extending therebetween and connecting the high speed compressor <NUM> and high speed turbine <NUM>. The high speed compressor <NUM>, the high speed turbine <NUM>, and the high speed shaft <NUM> may collectively be referred to as a high speed spool of the engine. Further, a combustion section <NUM> is located between the high speed compressor <NUM> and high speed turbine <NUM>. The combustion section <NUM> may include one or more configurations for receiving a mixture of fuel and air, and providing a flow of combustion gasses through the high speed turbine <NUM> for driving the high speed spool.

The low speed system similarly includes a low speed turbine <NUM>, a low speed compressor or booster, <NUM>, and a low speed shaft <NUM> extending between and connecting the low speed compressor <NUM> and low speed turbine <NUM>. The low speed compressor <NUM>, the low speed turbine <NUM>, and the low speed shaft <NUM> may collectively be referred to as a low speed spool of the engine.

Although the engine <NUM> is depicted with the low speed compressor <NUM> positioned forward of the high speed compressor <NUM>, in certain embodiments the compressors <NUM>, <NUM> may be in an interdigitated arrangement. Additionally, or alternatively, although the engine <NUM> is depicted with the high speed turbine <NUM> positioned forward of the low speed turbine <NUM>, in certain embodiments the turbines <NUM>, <NUM> may similarly be in an interdigitated arrangement.

Referring still to <FIG>, the turbomachine <NUM> is generally encased in a cowl <NUM>. Moreover, it will be appreciated that the cowl <NUM> defines at least in part an inlet <NUM> and an exhaust <NUM>, and includes a turbomachinery flowpath <NUM> extending between the inlet <NUM> and the exhaust <NUM>. The inlet <NUM> is for the embodiment shown an annular or axisymmetric <NUM> degree inlet <NUM> located between the rotor blade assembly <NUM> and the fixed or stationary vane assembly <NUM>, and provides a path for incoming atmospheric air to enter the turbomachinery flowpath <NUM> (and compressors <NUM>, <NUM>, combustion section <NUM>, and turbines <NUM>, <NUM>) inwardly of the guide vanes <NUM> along the radial direction R.

However, in other embodiments, the inlet <NUM> may be positioned at any other suitable location, e.g., aft of the vane assembly <NUM>, arranged in a non-axisymmetric manner, etc..

As is depicted, the rotor assembly <NUM> is driven by the turbomachine <NUM>, and more specifically, is driven by the low speed shaft <NUM>. More specifically, still, for the exemplary embodiment of the engine <NUM> depicted in <FIG>, the engine <NUM> includes a power gearbox <NUM>, and the rotor assembly <NUM> is driven by the low speed shaft <NUM> of the turbomachine <NUM> across the power gearbox <NUM>. In such a manner, the rotating rotor blades <NUM> of the rotor assembly <NUM> may rotate around the axis <NUM> and generate thrust to propel engine <NUM>, and hence an aircraft to which it is associated, in a forward direction F.

The power gearbox <NUM> may include a gearset for decreasing a rotational speed of the low speed shaft <NUM> relative to the low speed turbine <NUM>, such that the rotor assembly <NUM> may rotate at a slower rotational speed than the low speed shaft <NUM>.

Further, for the embodiment shown, the engine <NUM> includes an electric machine <NUM> coupled to a shaft of the engine rotatable about the longitudinal axis <NUM> of the engine <NUM>, and located inward of the engine flowpath <NUM> along the radial direction R, and inward of an airflow through the rotor blades <NUM> of the rotor assembly <NUM> along the radial direction R. More specifically, for the embodiment shown, it will be appreciated that the engine <NUM> includes a rotor shaft <NUM> extending from the gearbox <NUM> to the plurality of rotor blades <NUM> of the rotor assembly <NUM> for driving the plurality of rotor blades <NUM> of the rotor assembly <NUM>. The electric machine <NUM>, for the embodiment shown, is coupled to and rotatable with the rotor shaft <NUM>.

As will be described in more detail below, the engine <NUM> includes a cooling system for maintaining a temperature of the electric machine <NUM> within prescribed temperature limits. The cooling system generally includes a liquid cooling system <NUM> in thermal communication with the electric machine <NUM> for cooling the electric machine <NUM> as well as a cooling air system <NUM>. The cooling air system <NUM> may receive an airflow from engine flowpath <NUM> at a location downstream of the inlet <NUM> through one or more ducts <NUM> and valves <NUM>. An inlet of the ducts <NUM> may include features to guide a flow through the ducts <NUM> (e.g., one or more louvers, scoops, slots, etc.) based on, for example, an amount of cooling flow needed, an amount of turning a pressure recovery desired (e.g., to ensure the cooling air system <NUM> is properly pressurized), etc. The ducts <NUM> may also extend through the engine flowpath <NUM> at a location downstream of an inlet guide vane <NUM> of the engine <NUM> and upstream of the low speed compressor <NUM> to the electric machine <NUM>. However, in other embodiments, the ducts <NUM> of the cooling air system <NUM> may extend through the engine flowpath <NUM> at any other suitable location, or any other suitable form of cooling airflow may be provided to the electric machine <NUM>.

It will be appreciated, however, that the exemplary single rotor unducted engine <NUM> depicted in <FIG> is by way of example only, and that in other exemplary embodiments, the engine <NUM> may have any other suitable configuration, including, for example, any other suitable number of shafts or spools, turbines, compressors, etc. Additionally, although the engine <NUM> is depicted as a single unducted rotor engine <NUM>, in other embodiments, the engine <NUM> may further include a nacelle or duct enclosing at least a portion of the rotor assembly <NUM>, the turbomachine, or both. In such a configuration, the outlet guide vanes may connect to the nacelle, and the nacelle and turbomachine may together define a bypass passage. Additionally, or alternatively, still, although the engine <NUM> is depicted as a geared engine <NUM> (i.e., including a gearbox between the low speed shaft <NUM> and rotor assembly <NUM>), in other embodiments, aspects of the present disclosure may additionally or alternatively be applied to a direct drive engine where the low speed shaft <NUM> and a rotor shaft <NUM> of the rotor assembly are connected or unified such that the low speed shaft <NUM> rotates at the same speed as the rotor assembly <NUM>.

Further, still, although the engine <NUM> is depicted having a rotor assembly having a single stage of rotor blades, in other embodiments, the engine <NUM> may include a multi-stage rotor configuration (open or enclosed by a nacelle), and aspects of the disclosure described hereinbelow may be incorporated therein.

Further, still, in other exemplary embodiments, any other suitable gas turbine engine <NUM> may be provided. For example, in other exemplary embodiments, the gas turbine engine <NUM> may be a ducted turbofan engine <NUM>, a turboshaft engine, a turboprop engine, turbojet engine, etc..

Referring now to <FIG>, a close-up, schematic view is depicted of an electric machine <NUM> coupled to and rotatable with an engine shaft <NUM> of an engine <NUM> rotatable about an axis <NUM> of the engine <NUM>. In at least certain exemplary embodiments, the electric machine <NUM> and engine <NUM> depicted in <FIG> may be configured in a similar manner as the exemplary electric machine <NUM> in engine <NUM> described above with reference to <FIG>, and thus the same or similar reference numerals may refer to the same or similar parts. In such a manner, it will be appreciated that in at least certain exemplary embodiments, the engine shaft <NUM> depicted in <FIG> may be the exemplary rotor shaft <NUM> of the engine <NUM> of <FIG> configured to rotate the plurality of rotor blades <NUM> of the rotor assembly <NUM> about the axis <NUM>.

However, in other embodiments, aspects of the present disclosure may be applied to other electric machine <NUM> mounting locations and/or engine configurations, such that the engine shaft <NUM> may be any other suitable engine shaft (such as a low pressure shaft, a high pressure shaft, etc.).

For the embodiment shown, the electric machine <NUM> generally includes a rotor <NUM> coupled to and rotatable with the engine shaft <NUM> and a stator <NUM>. More specifically, for the embodiment shown, the rotor <NUM> is coupled to and rotatable with the engine shaft <NUM> through a rotor mount <NUM>. The rotor mount <NUM> extends, for the embodiment shown, from the engine shaft <NUM> to the rotor <NUM> to couple the rotor <NUM> of the electric machine <NUM> to the engine shaft <NUM>.

The electric machine <NUM> is generally configured as a radial flux electric machine, defining an air gap <NUM> between the rotor <NUM> and the stator <NUM> extending generally along an axial direction A of the engine <NUM>. And further, for the embodiment shown, the electric machine <NUM> is configured as an "in-runner" electric machine <NUM>, such that the rotor <NUM> is located inward of the stator <NUM> along a radial direction R of the engine <NUM>. Notably, however, in other embodiments, the electric machine <NUM> may have other suitable configurations. For example, in other embodiments, the electric machine <NUM> may instead be oriented such that the air gap <NUM> defines an angle with respect to the axial direction A of the engine <NUM>.

As is shown, with embodiment depicted, the rotor <NUM> extends generally along the axial direction A defining a first end <NUM> and a second end <NUM> along the axial direction A. Similarly, the stator <NUM> extends generally along the axial direction A defining a first end <NUM> and a second end <NUM> on the axial direction A. More specifically, the stator <NUM> includes a core <NUM> and a plurality of windings <NUM>, and for the embodiment shown, the plurality of windings <NUM> include portions at the first end <NUM> and the second end <NUM> of the stator <NUM>. It will be appreciated, however, that in other exemplary aspects, any other suitable stator configuration may be provided, such that the first and second ends <NUM> of the stator include any other suitable features.

As with the embodiment described above with reference to <FIG>, the exemplary engine <NUM> depicted in <FIG> includes a cooling system for maintaining a temperature of the electric machine <NUM> within prescribed limits. The cooling system includes a liquid cooling system <NUM> thermally coupled to the electric machine <NUM> and a cooling air system <NUM>. The liquid cooling system <NUM> may more specifically be operable with the stator <NUM> to reduce a temperature of certain aspects of the stator <NUM>.

However, it may be difficult for the liquid cooling system <NUM> to effectively reduce the temperature of other aspects of the stator <NUM> of the electric machine <NUM>, such as the first end <NUM> and second end <NUM> of stator <NUM>, such as for example, portions of the windings <NUM> located at the first end <NUM> and the second end <NUM> of the stator <NUM>. Accordingly, for the embodiment depicted, the cooling air system <NUM> provided may assist with cooling of one or more of such portions of the electric machine <NUM>.

As with the embodiment described above, the exemplary cooling air system <NUM> of the engine <NUM> depicted in <FIG> includes one or more cooling ducts <NUM> for providing a flow of cooling fluid towards the electric machine <NUM> during operation of the engine <NUM>. The one or more ducts <NUM> may more specifically provide for a flow of cooling air <NUM> towards the electric machine <NUM> during operation of the engine <NUM>. For example, in certain exemplary aspects, the one or more cooling ducts <NUM> may receive a flow of cooling air <NUM> from a compressor section of the engine <NUM> as a bleed airflow from the compressor section of the engine <NUM>. For example, the bleed airflow may be provided from a low pressure compressor, from a high pressure compressor, and/or from a location between the low pressure compressor and high pressure compressor. Alternatively, the flow of cooling air <NUM> in the ducts <NUM> may be provided from, e.g., an ambient location, a location over a cowl <NUM> of the engine <NUM>, etc..

Referring still to <FIG>, the one or more cooling ducts <NUM> of the cooling air system <NUM> generally provide a flow of cooling air <NUM> to cool various portions of electric machine <NUM>. Specifically, for the exemplary embodiment depicted, the one or cooling ducts <NUM> of the cooling air system <NUM> define a first cooling air flowpath <NUM> extending to a first end of the electric machine <NUM> (e.g., ends <NUM>, <NUM>) and a second cooling air flowpath <NUM> extending to the second end of the electric machine <NUM> (e.g., ends <NUM>, <NUM>). The first cooling air flowpath <NUM> and second cooling air flowpath <NUM> split at a junction <NUM> within the one or more ducts <NUM>. It will be appreciated that the one or more ducts <NUM> may include one duct <NUM> or a plurality of ducts <NUM> located along the circumferential direction. In such a manner, the junction <NUM> may be a single junction, or there may be multiple junctions <NUM> at various locations along the circumferential direction.

The first cooling air flowpath <NUM> travels through a first opening <NUM> defined within the one or more ducts <NUM> to a plenum <NUM> defined at least in part by the rotating rotor mount <NUM> extending between the engine shaft <NUM> in the rotor <NUM> and the static structure including the ducts <NUM>. The first cooling air flowpath <NUM> further travels through one or more openings <NUM> within the rotor mount <NUM> to a cooling manifold <NUM> that is rotatable with the rotor <NUM> and positioned at the first end <NUM> of the rotor <NUM>. The cooling manifold <NUM> is configured to receive a flow of cooling fluid, and more specifically is configured to provide such cooling fluid to the stator <NUM> during operation of the engine <NUM>. More specifically, still, for the embodiment shown, the flow of cooling fluid is a flow of cooling air <NUM> provided along the first cooling air flowpath <NUM>.

Briefly, it will further be appreciated that the second cooling air flowpath <NUM> travels from the junction <NUM> to a stationary manifold <NUM> located at the second end <NUM> of the rotor <NUM>, at a location inward of the second end <NUM> of the stator <NUM>. The stationary manifold <NUM> may extend in the circumferential direction, having a substantially annular chamber <NUM>. A flow control feature <NUM> may be included at, e.g., a location upstream of the stationary manifold <NUM> to control an amount of airflow <NUM> to the annular chamber <NUM>. The flow control feature <NUM> may be, e.g., a baffle plate or slot to drive the flow into the annular chamber <NUM> to enhance a heat transfer coefficient in the chamber <NUM> to provide additional cooling to a fluid seal component <NUM> (described below). The flow control feature <NUM> could be sized to provide deterministic heat transfer cooling for the fluid seal, prior to delivering the flow through the stationary manifold <NUM> into the upper cavity. The stationary manifold <NUM> defines one or more second openings <NUM> oriented towards the second end <NUM> of the stator <NUM> of the electric machine <NUM>. In such a manner, the flow of cooling air <NUM> through the second cooling air flowpath <NUM> may be provided onto the second end <NUM> of the stator <NUM>, or more specifically onto a portion of the windings <NUM> of the stator <NUM> positioned at the second end <NUM> of stator <NUM>. The second air flowpath <NUM> further extends through the air gap <NUM> of the electric machine <NUM> defined between the rotor <NUM> and the stator <NUM>, such that the flow of cooling air <NUM> through the second air flowpath <NUM> may further provide cooling to the electric machine <NUM> along the air gap <NUM>.

Referring still <FIG>, and now back to the cooling manifold <NUM>, it will be appreciated that the cooling manifold <NUM> is, for the embodiment shown, coupled to the first end <NUM> of the rotor <NUM> of the electric machine <NUM>, to the rotor mount <NUM> coupling the rotor <NUM> of the electric machine <NUM> to the engine shaft <NUM>, or both. For the embodiment shown, the cooling manifold <NUM> is coupled to both the rotor <NUM> and the rotor mount <NUM>. However, in other embodiments, the cooling manifold <NUM> may be coupled to only the rotor <NUM> or only the rotor mount <NUM>.

More specifically, referring now to <FIG>, a prospective, cross-sectional view of the cooling manifold <NUM> and a portion of the electric machine <NUM> of <FIG> is provided. As will be appreciated from the view of <FIG>, the cooling manifold <NUM> is, for any embodiment shown, coupled to the rotor mount <NUM> and rotor <NUM> using a plurality of fasteners <NUM> spaced along a circumferential direction C of the engine <NUM>. More specifically, still, for the embodiment shown, the cooling manifold <NUM> is coupled to the rotor mount <NUM> at a first position <NUM> along the radial direction R and a second position <NUM> along the radial direction R using a plurality of fasteners <NUM>, the plurality of fasteners <NUM> spaced along the circumferential direction C at each of the first and second positions <NUM>, <NUM> along the radial direction R. Although for the embodiment depicted the cooling manifold <NUM> is not coupled directly to the rotor <NUM> of the electric machine <NUM>, it will be appreciated that the cooling manifold <NUM> is positioned adjacent to the first end <NUM> of the rotor <NUM> of the electric machine <NUM>, and in the embodiment shown, is directly contacting the rotor <NUM> of the electric machine <NUM>. Moreover, as will be further appreciated from the discussion hereinbelow, the cooling manifold <NUM> is located inward of the second end <NUM> of the stator <NUM> along the radial direction R (at the same location or overlapping locations along the axial direction A).

As will also be appreciated from the view of <FIG>, the cooling manifold <NUM> is configured as a substantially annular manifold defining a substantially annular airflow chamber <NUM> configured to receive the flow of cooling air <NUM> from the first air flowpath <NUM> of the cooling air system <NUM>. Referring briefly to the cross-sectional, schematic views of <FIG>, it will be appreciated that the cooling manifold <NUM> defines a plurality of embossments <NUM> extending inwardly along the axial direction A to allow for the cooling manifold <NUM> to be coupled to the rotor <NUM> at the second location <NUM> along the radial direction R using the plurality of fasteners <NUM>. More specifically, <FIG> shows a cross-sectional view of the cooling manifold <NUM> at one of these embossments <NUM>, and <FIG> provides a cross-sectional view of the cooling manifold <NUM> at a different circumferential location, between embossments <NUM>. As shown in <FIG>, the cooling manifold <NUM> defines a clear flowpath between the openings <NUM> in the rotor mount <NUM> and the substantially annular airflow chamber <NUM> of the cooling manifold <NUM> despite the embossments <NUM>.

Referring still generally to <FIG>, it will be appreciated that the cooling manifold <NUM> further defines one or more impingement openings <NUM> oriented outwardly along the radial direction R. More specifically, the cooling manifold <NUM> defines one or more impingement openings <NUM> oriented towards the stator <NUM> for providing the flow of cooling air <NUM> received by the cooling manifold <NUM> and within the substantially annular airflow chamber <NUM> onto the stator <NUM>. The one or more impingement openings <NUM> may include a plurality of impingement openings <NUM> spaced along the circumferential direction C of the engine <NUM>. Alternatively the one or more impingement openings <NUM> may include a continuous or substantially continuous impingement opening <NUM> extending along the circumferential direction C.

Referring particularly to <FIG>, it will be appreciated that for the embodiment shown, the one or more impingement openings <NUM> of the cooling manifold <NUM> are oriented towards the first end <NUM> of the stator <NUM> for providing the flow of cooling air <NUM> received by the cooling manifold <NUM> and within the substantially annular airflow chamber <NUM> onto first end <NUM> of the stator <NUM>. More specifically, for the embodiment depicted, the one or more impingement openings <NUM> of the cooling manifold <NUM> are oriented towards at least a portion of the plurality of windings <NUM> of the stator <NUM>, located at the first end <NUM> of the stator <NUM> for providing the flow of cooling air <NUM> received by the cooling manifold <NUM> and within the substantially annular airflow chamber <NUM> onto the portion of the plurality of windings <NUM> located at the first end <NUM> of the stator <NUM>.

It will be appreciated, however, that in other exemplary embodiments of the present disclosure, the cooling air system <NUM> may have any other suitable configuration. For example, the cooling air manifold <NUM> may have any other suitable configuration. For example, manifold <NUM> may define one or more impingement openings <NUM> oriented outwardly along the radial direction R in any other suitable manner, such as not directly along the radial direction R.

Referring now briefly to <FIG>, a cooling manifold <NUM> in accordance with another exemplary embodiment of the present disclosure is provided. The exemplary cooling manifold <NUM> depicted includes a local thickness <NUM> that defines one or more impingement openings <NUM>. Inclusion of the local thickness <NUM> (which may have a maximum thickness at least two times as thick as a surrounding portion of the cooling manifold <NUM> and up to <NUM> times as thick as the surrounding portion of the cooling manifold <NUM>) may allow for the impingement opening(s) <NUM> to direct the cooling air <NUM> in a more precise manner.

For example, referring now to <FIG>, providing a schematic, cross-sectional view of an impingement opening(s) <NUM> in <FIG>, along Line <NUM>-<NUM> in <FIG>, it will be appreciated that in certain exemplary aspects, the impingement opening(s) <NUM> may be oriented towards the stator <NUM>, at an angle <NUM> relative to a radial direction R to impart a circumferential velocity to the cooling air <NUM> through the impingement opening(s) <NUM>. The angle <NUM> may be between <NUM> degrees and <NUM> degrees, such as at least <NUM> degrees, such as at least <NUM> degrees, such as at least <NUM> degrees, such as at least <NUM> degrees, such at least <NUM> degrees, such as up to <NUM> degrees. Further, it will be appreciated that the exemplary impingement opening <NUM> depicted in <FIG> defines a length <NUM> and a diameter <NUM> (or maximum width for non-circular openings). A ratio of the length <NUM> to diameter <NUM> may be greater than <NUM>:<NUM> and less than <NUM>:<NUM>, such as less than <NUM>:<NUM>, such as less than <NUM>:<NUM>. Such a configuration may allow for more effective cooling of the stator <NUM>, despite a rotation of the rotor <NUM>.

Inclusion of a cooling manifold <NUM> in accordance with one or more these exemplary embodiments may allow for the cooling air system <NUM> of the engine <NUM> to provide a desired amount of cooling for the portions of the plurality of windings <NUM> positioned at the first end <NUM> of the stator <NUM>.

Referring now back to <FIG>, it will be appreciated that the exemplary engine <NUM> depicted in <FIG> further includes a fluid seal <NUM> adjacent to the electric machine <NUM>, and more specifically, adjacent to the second end <NUM> of the rotor <NUM> of the electric machine <NUM>. The fluid seal <NUM> provides a stationary-to-rotating fluid seal <NUM> between the first cooling air flowpath <NUM> and the second cooling air flowpath <NUM>, and as such, the fluid seal <NUM> is in airflow communication with the first cooling air flowpath <NUM> and the second cooling air flowpath <NUM>. In at least certain exemplary aspects, a pressure of the flow of cooling air <NUM> through the first cooling air flowpath <NUM> may be different than the pressure of the flow of cooling air <NUM> through the second cooling air flowpath <NUM>. In such a manner, the fluid seal <NUM> may prevent or minimize leakage of airflow between the first cooling air flowpath <NUM> and the second cooling air flowpath <NUM>.

Referring now also to <FIG>, a close up, cross-sectional view of the fluid seal <NUM> is provided. As shown, the fluid seal <NUM> generally includes a first member <NUM> rotatable with the rotor <NUM> of the electric machine <NUM> and a second member <NUM> coupled to or formed integrally with a static structure, such as a static structure including the one or more ducts <NUM> of the cooling air system <NUM> or the circumferential manifold defining the openings <NUM> (see <FIG>). The first member <NUM> generally includes a first set <NUM> of seal teeth <NUM> and the second member <NUM> generally includes a second set <NUM> of seal teeth <NUM> the first and second sets <NUM>, <NUM> of seal teeth <NUM>, <NUM> are alternatingly spaced along a length L of the fluid seal <NUM>.

More specifically, for the embodiment shown, the first set <NUM> of seal teeth <NUM> includes at least three seal teeth <NUM> and the second set <NUM> of seal teeth <NUM> also includes at least three seal teeth <NUM>. More specifically, for the embodiment show, the first set <NUM> of seal teeth <NUM> includes five seal teeth <NUM> and the second set <NUM> of seal teeth <NUM> includes four seal teeth <NUM>. As will be appreciated, each seal tooth <NUM>, <NUM> is generally an annular seal tooth extending <NUM>° the circumferential direction C about the axis <NUM> of the engine <NUM> (see <FIG>). Although for the embodiment shown, the first set <NUM> of seal teeth <NUM> includes five seal teeth <NUM> and the second set <NUM> of seal teeth <NUM> includes four seal teeth <NUM>, in other embodiments, the first set <NUM> of seal teeth <NUM>, the second set <NUM> of seal teeth <NUM>, or both may have any other suitable number of seal teeth <NUM> within their respective sets. For example, in another example embodiment, the first set <NUM> of seal teeth <NUM>, the second set <NUM> of seal teeth <NUM>, or both may include <NUM> seal tooth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, <NUM> seal teeth, or up to <NUM> seal teeth. The first set <NUM> of seal teeth <NUM> may include the same number of seal teeth <NUM> as the second set <NUM>, or alternatively, the first and second sets <NUM>, <NUM> of seal teeth <NUM>, <NUM> may have a different number of seal teeth <NUM>.

Further, for the embodiment shown, each of the seal teeth <NUM> within the first and second sets <NUM>, <NUM> of seal teeth <NUM>, <NUM> extend generally in a direction perpendicular to the length L of the fluid seal <NUM>. More specifically, for the embodiment shown, the length L of the fluid seal <NUM> is generally aligned with, and defined along, the radial direction R of the engine <NUM>. In such a manner, it will be appreciated that the first and second sets <NUM>, <NUM> of seal teeth <NUM>, <NUM> generally extend on the axial direction A of the engine <NUM>.

It will be appreciated, however, that in other exemplary embodiments, the fluid seal <NUM> may be oriented in any other suitable direction (e.g., defining an angle with respect to the radial direction R of the engine <NUM>), and/or the plurality of seal teeth <NUM> of the first and second sets <NUM>, <NUM> of seal teeth <NUM>, <NUM> may not extend directly perpendicularly to the length L of the fluid seal <NUM>.

Referring still to <FIG>, it will be appreciated that the first member <NUM> of the fluid seal <NUM> further defines a first plurality of valleys <NUM> between adjacent seal teeth <NUM> of the first set <NUM> of seal teeth <NUM>, and similarly, the second member <NUM> defines a second plurality of valleys <NUM> between adjacent seal teeth <NUM> of the second set <NUM> of seal teeth <NUM>. In the embodiment shown, the first set <NUM> of seal teeth <NUM> defines gaps <NUM> with the second plurality of valleys <NUM> along the axial direction A, and similarly, the second set <NUM> of seal teeth <NUM> defines gaps <NUM> with the first plurality of valleys <NUM> along the axial direction A. Such a configuration may allow for any natural variances along the axial direction A during operation of the engine <NUM> between the rotor <NUM> of the electric machine <NUM> and the static structure surrounding the rotor <NUM> of the electric machine <NUM>.

Moreover, in order to further accommodate these natural variances, it will be appreciated that the first member <NUM> further includes an abradable coating <NUM> on the first plurality of valleys <NUM> defined between adjacent seal teeth <NUM> of the first set <NUM> of seal teeth <NUM>, and similarly, the second member <NUM> also includes an abradable coating <NUM> on the second plurality of valleys <NUM> defined between adjacent seal teeth <NUM> of the second set <NUM> of seal teeth <NUM>. The abradable coatings <NUM>, <NUM> are positioned on the surface of the valleys <NUM>, <NUM> to interface with the opposing seal teeth <NUM>, <NUM>. In such a manner, in the event the relative movement between the rotor <NUM> of the electric machine <NUM> and the static structure surrounding the rotor <NUM> of the electric machine <NUM> exceeds the length of the gaps <NUM>, <NUM>, the respective seal teeth <NUM> may not cause unnecessary damage to the first member <NUM>, the second member <NUM>, or both, and further may not substantially disrupt operation of, e.g., the electric machine <NUM>.

Notably, although not depicted, it will be appreciated that in at least certain exemplary aspects, the sides of the teeth <NUM>, <NUM> may also include an abradable coating to accommodate relative movement, e.g., along the radial direction R.

Referring again to <FIG>, it will be appreciated that in certain exemplary embodiments, the flow of cooling air <NUM> from the cooling air system <NUM> may additionally provide further benefits and serve additional functions for the engine <NUM>. For example, for the embodiment shown, the cooling air system <NUM> further defines a third cooling air flowpath <NUM> branching off from the first cooling air flowpath <NUM> to provide flow of cooling air <NUM>/pressurized air to a sump. More specifically, the engine <NUM> defines a bearing sump <NUM> enclosing a bearing <NUM> that supports rotation of the engine shaft <NUM>. Further, the engine <NUM> includes a seal <NUM> (which is represented schematically, and may be, e.g., a labyrinth seal) that defines at least in part the bearing sump <NUM> surrounding the bearing <NUM>. A flow of cooling air <NUM> through the third cooling air flowpath <NUM> may pressurize the bearing sump <NUM> by providing pressurized air to the seal <NUM>, and may also provide a measure of cooling through any of the cooling <NUM> provided to the bearing sump <NUM>.

Further, as is depicted schematically in <FIG>, the flow of cooling air <NUM> from the first cooling air flowpath <NUM>, the second cooling air flowpath <NUM>, and/or the third cooling air flowpath <NUM> (or at least a portion of the flow of cooling air <NUM> from the third cooling air flowpath <NUM>) after imparting a measure of cooling may be provided to an engine flowpath <NUM> of the engine <NUM>. For example, the flow of cooling air <NUM> through the first cooling air flowpath <NUM> and the second cooling air flowpath <NUM> may be provided to the engine flowpath <NUM> after having been provided to/impinged upon the stator <NUM> of electric machine <NUM>. For example, in the embodiment shown, the flow of cooling air <NUM> is provided to the engine flowpath <NUM> at a location upstream of a compressor of the engine <NUM> (see also, e.g., <FIG>), and more specifically, at a location upstream of an inlet guide vane <NUM> of the engine <NUM>. In particular, for the embodiment shown, the flow of cooling air <NUM> is provided to the engine flowpath <NUM> at the location where the arrow representing the flow of cooling air (labeled <NUM>) reaches the flowpath <NUM>.

In such a manner, the flow of cooling air <NUM> provided through the cooling air system <NUM> may be utilized to reduce a temperature of one or more exemplary aspects of the electric machine <NUM> and/or other components of the engine <NUM>, and may subsequently be provided to the engine flowpath <NUM>, increasing an amount of energy and the airflow through the engine flowpath <NUM>.

Claim 1:
A gas turbine engine (<NUM>) defining a radial direction, an axial direction, and an axis (<NUM>) extending along the axial direction of the gas, the gas turbine engine (<NUM>) comprising:
a shaft configured to rotate about the axis (<NUM>);
an electric machine (<NUM>) comprising a rotor (<NUM>) coupled to and rotatable with the shaft and a stator (<NUM>), the rotor (<NUM>) defining an end along the axial direction; characterized in that the gas turbine engine further comprises
a cooling manifold (<NUM>) rotatable with the rotor (<NUM>) and positioned at the end of the rotor (<NUM>), the cooling manifold (<NUM>) configured to receive a flow of cooling fluid and provide the cooling fluid to the stator (<NUM>) during operation of the gas turbine engine (<NUM>).