Bearing current mitigation for electric machines embedded in gas turbine engines

Abstract

A hybrid electric propulsion system is provided. In one example aspect, the hybrid electric propulsion system includes a power converter and a propulsor. The propulsor includes a gas turbine engine having a shaft and one or more bearings supporting the shaft. The propulsor also includes an electric machine electrically coupled with the power converter. The electric machine includes a stator assembly and a rotor assembly. The rotor assembly has a rotor and a rotor connection assembly. The rotor connection assembly operably couples the rotor with the shaft. The rotor connection assembly has an insulating joint to interrupt a common mode current flow from the rotor of the electric machine to the shaft. A grounding device is included to electrically ground the shaft. The power converter includes an electromagnetic interference filter to reduce a common mode voltage reaching the electric machine.

Description

TECHNICAL FIELD

[0001] The present subject matter relates generally to a gas turbine engine equipped with an embedded electric machine. BACKGROUND

[0002] Conventional commercial aircraft generally include a fuselage, a pair of wings, and a propulsion system that provides thrust. The propulsion system generally includes at least two aircraft engines, such as turbofan jet engines. Each turbofan jet engine is typically mounted to a respective one of the aircraft's wings, such as in a pylon position under the wing separate from the wing and fuselage.

[0003] Hybrid-electric propulsion systems are being developed to improve the efficiency of conventional commercial aircraft. Some hybrid-electric propulsion systems include one or more electric machines that are each operably coupled with a rotating component of one of the aircraft engines. The inventors of the present disclosure have developed various configurations and / or methods to improve hybrid-electric propulsion systems. SUMMARY

[0004] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0005] In one example aspect of the present disclosure, a hybrid-electric propulsion system is provided. The hybrid-electric propulsion system includes a power converter and a propulsor. The propulsor includes a gas turbine engine having a shaft and one or more bearings that support the shaft. Further, the propulsor includes an electric machine that is electrically coupled with the power converter. The electric machine includes a stator assembly and a rotor assembly. The rotor assembly has a rotor and a rotor connection assembly. The rotor connection assembly operably couples the rotor with the shaft. The rotor connection assembly has an insulating joint to interrupt a common mode current flow from the rotor to the shaft. A grounding device can be included to electrically ground the shaft.

[0006] These and other features, aspects, and advantages of the present application will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. BRIEF DESCRIPTION OF DRAWINGS

[0007] A complete and enabling disclosure of the application, including the best mode thereof, to one of ordinary skill in the art, is set forth in the specification taken in conjunction with the annexed drawings, in which:

[0008] Figure 1 A schematic top view of an aircraft is provided in accordance with various example embodiments of the present disclosure;

[0009] Figure 2 A schematic top view of an aircraft is provided in accordance with various example embodiments of the present disclosure; Figure 1A schematic cross-sectional view of one of the hybrid electric propulsion systems in an aircraft;

[0010] Figure 3 Provided with Figure 1 A schematic cross-sectional view of the hybrid electric propulsion system implemented together with the aircraft;

[0011] Figure 4 Provides embedding Figure 2 A schematic cross-sectional view of the electric motor in a gas turbine engine with a hybrid electric propulsion system;

[0012] Figure 5 A schematic cross-sectional view of an electric motor having an internal rotor configuration and embedded in a gas turbine engine, according to various exemplary embodiments of the present disclosure, is provided;

[0013] Figure 6 Provided from Figure 4 A close-up cross-sectional view of the insulating joint of the motor rotor assembly, taken from section 5.

[0014] Figure 7 A close-up cross-sectional view of the insulating joint of the rotor assembly of an electric motor according to an example embodiment of the present disclosure is provided;

[0015] Figure 8 A close-up cross-sectional view of the insulating joint of the rotor assembly of an electric motor according to another exemplary embodiment of the present disclosure is provided;

[0016] Figure 9 A schematic cross-sectional view of an electric motor embedded in a gas turbine engine according to various exemplary embodiments of the present disclosure is provided;

[0017] Figure 10 A close-up cross-sectional view of a grounding device integrated into a carbon seal according to an example embodiment of the present disclosure is provided;

[0018] Figure 11 A close-up cross-sectional view of a grounding device integrated into a carbon seal according to another exemplary embodiment of this disclosure is provided;

[0019] Figure 12 A close-up cross-sectional view of a grounding device integrated into a carbon seal according to yet another exemplary embodiment of the present disclosure is provided;

[0020] Figure 13 A close-up view of an example brush seal integrated as a grounding device according to various exemplary embodiments of the present disclosure is provided;

[0021] Figure 14 Flowcharts of methods for operating a hybrid electric thruster according to various exemplary embodiments of the present disclosure are provided; and

[0022] Figure 15 An example computing system according to example embodiments of the present disclosure is provided. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to the present embodiments of the application, one or more examples of which are illustrated in the drawings. The detailed description uses numerical and letter designations

[0024] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, unless otherwise explicitly provided, none of the description of examples should be construed as limiting the scope of the claims.

[0025] As used herein, the terms “first,” “second,” and “third” can be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

[0026] The terms “forward” and “aft” refer to relative positions within a gas turbine engine or vehicle and refer to the normal operating attitude of the gas turbine engine or vehicle. For example, for a gas turbine engine, forward refers to a position closer to the engine inlet and aft refers to a position closer to the engine nozzle or exhaust.

[0027] The terms “upstream” and “downstream” refer to the relative direction with respect to the flow in a path. For example, for a fluid flow, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. However, the terms “upstream” and “downstream” as used herein can also refer to electrical current.

[0028] The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0029] As used throughout the specification and claims, approximate language is applied to modify any quantitative representation that can permit variations without resulting in a change of the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” is not limited to the precise value specified. In at least some instances, the approximate language can correspond to the precision of an instrument used to measure the value, or the precision of a method or machine used to construct or manufacture the component and / or system. In at least some instances, the approximate language can correspond to the precision of an instrument used to measure the value, or the precision of a method or machine used to construct or manufacture the component and / or system. For example, the approximate language can refer to a margin of 1%, 2%, 4%, 5%, 10%, 15%, or 20% within a single value, a range of values, and / or an endpoint of a defined range of values.

[0030] Throughout this document and in the claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges included therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0031] The inventors of the present disclosure have developed various solutions for mitigating current in bearings that support a shaft coupled to an electric machine. As will be appreciated, a common mode voltage can be generated by a sinusoidal power converter power source. In this regard, an electric machine connected to a power converter power source is inherently affected by the common mode voltage. This common mode voltage can induce or drive current in bearings that support a shaft coupled to the electric machine. The current in the bearings can cause pitting of the bearing elements (e.g., balls, rollers, raceways, etc.) and, thus, can cause premature failure of such bearings. Accordingly, it is desirable to mitigate such bearing current.

[0032] Some conventional techniques for mitigating bearing current in an electric machine connected to a power converter involve the use of ceramic bearings to support a shaft coupled to the electric machine. While such ceramic bearings are effective, in certain situations, the use of ceramic bearings is not a viable option, for example, when the bearings are shared with other components. In addition, in addition to ceramic bearings, a ground brush is typically used. However, like ceramic bearings, in certain situations, the use of a ground brush can not be allowed. The bearing current mitigation solutions developed by the inventors of the present disclosure provide an alternative to such conventional techniques.

[0033] According to inventive aspects of the present disclosure, various bearing mitigation solutions are provided. Such solutions can be used individually or in combination with each other. For example, in one example aspect, a three-pronged solution can be implemented. The three-pronged solution can include: 1) reducing the common mode voltage reaching the electric machine from the power converter connected thereto; 2) interrupting the common mode current conduction path between the rotor of the electric machine and the shaft coupled thereto; and 3) grounding at least one of the components connecting the rotor of the electric machine and the shaft.

[0034] In one example aspect, under Aspect One, an electromagnetic interference filter of a power converter electrically coupled to an electric machine can reduce common mode voltage reaching the electric machine. Further, a shielded cable or a shielded bus electrically coupling the power converter and the electric machine can be used to further reduce the common mode voltage reaching the electric machine. Under Aspect Two, a rotor connection assembly coupling a rotor of the electric machine to a shaft can include an insulating joint. The insulating joint includes one or more insulating members strategically arranged to interrupt a flow of common mode current to the shaft. Under Aspect Three, a grounding device is positioned relative to the shaft or a component that can rotate with the shaft to electrically ground the shaft. The grounding device can be integrated into an existing component of the engine. For example, the grounding device can be integrated into a resolver, an encoder, or an existing seal such as a carbon seal or a brush seal. Under this three-aspect approach, bearing current mitigation can be achieved. Advantageously, this can enable specific fuel burn gains through power circulation between low speed spools and high speed spools without shortening the life of bearings supporting the spools. Further, this can mitigate low speed bearing currents without modifying such bearings and with only minimal modifications to the spool rotor structure.

[0035] Figure 1 A schematic top view of an example aircraft 100 that can incorporate one or more inventive aspects of the present disclosure is provided. As shown, the aircraft 100 defines a longitudinal direction LI and a lateral direction L2. The lateral direction L2 is perpendicular to the longitudinal direction LI. The aircraft 100 also defines a longitudinal centerline 114 extending therethrough along the longitudinal direction LI. The aircraft 100 extends, for example, along the longitudinal direction LI between a forward end 116 and an aft end 118. Figure 1

[0036] As shown, the aircraft 100 includes a fuselage 112 extending longitudinally from a forward end 116 of the aircraft 100 to an aft end 118 of the aircraft 100. The aircraft 100 also includes a tail 119 at the aft end 118 of the aircraft 100. Additionally, the aircraft 100 includes a wing assembly including a first port wing 120 and a second starboard wing 122. The first wing 120 and the second wing 122 each extend laterally outward relative to the longitudinal centerline 114. The first wing 120 and a portion of the fuselage 112 together define a first side 124 of the aircraft 100, and the second wing 122 and another portion of the fuselage 112 together define a second side 126 of the aircraft 100. For the depicted embodiment, the first side 124 of the aircraft 100 is configured as a port side of the aircraft 100, and the second side 126 of the aircraft 100 is configured as a starboard side of the aircraft 100.

[0037] ​The aircraft 100 includes various control surfaces. For this embodiment, each wing 120, 122 includes one or more leading edge flaps 128 and one or more trailing edge flaps 130. The aircraft 100 also includes, or more specifically, the tail 119 of the aircraft 100 includes, a vertical stabilizer 132 having a rudder flap (not shown) for yaw control and a pair of horizontal stabilizers 134, each having an elevator flap 136 for pitch control. The fuselage 112 additionally includes an outer surface or skin 138. It should be appreciated that in other example embodiments of the present disclosure, the aircraft 100 can additionally or alternatively include any other suitable configuration. For example, in other embodiments, the aircraft 100 can include any other control surface configuration.

[0038] Figure 1 The example aircraft 100 also includes a hybrid electric propulsion system 150. For this embodiment, the hybrid electric propulsion system 150 has a first propulsor 200A and a second propulsor 200B, both of which are operable to generate thrust. The first propulsor 200A is mounted to the first wing 120 and the second propulsor 200B is mounted to the second wing 122. Further, for the depicted embodiment, the first propulsor 200A and the second propulsor 200B are each configured in a wing-underslung configuration. However, in other example embodiments, one or both of the first propulsor 200A and the second propulsor 200B can be mounted in any other suitable location in other example embodiments.

[0039] The first propulsor 200A includes a gas turbine engine 210A and one or more electric machines, such as an electric machine 300A operably coupled with the gas turbine engine 210A. The electric machine 300A can be a generator, an electric motor, or a combined generator / motor. For this example embodiment, the electric machine 300A is a combined generator / motor. In this way, when operating as a generator, the electric machine 300A can generate electrical power when driven by the gas turbine engine 210A. When operating as an electric motor, the electric machine 300A can drive or push the gas turbine engine 210A.

[0040] Similarly, the second thruster 200B includes a gas turbine engine 210B and one or more electric motors, such as an electric motor 300B operatively coupled to the gas turbine engine 210B. The electric motor 300B can be a generator, an electric motor, or a combined generator / electric motor. For this example embodiment, the electric motor 300B is a combined generator / electric motor. In this way, when operating as a generator, the electric motor 300B can generate electricity when driven by the gas turbine engine 210B. When operating as an electric motor, the electric motor 300B can drive or propel the spool of the gas turbine engine 210B. The electric motor 300B can be constructed and operated in a manner similar to that of the electric motor 300A described herein.

[0041] The hybrid electric propulsion system 150 also includes an energy storage unit 180 that can be electrically connected to motors 300A and 300B (and in some embodiments, to other electrical loads). Figure 1 (Only one is shown in the text). In some exemplary embodiments, the energy storage unit 180 may include one or more batteries. Additionally or alternatively, the energy storage unit 180 may include one or more supercapacitor arrays, one or more supercapacitor arrays, or both. For the hybrid electric propulsion system 150 described herein, the energy storage unit 180 is configured to store a relatively large amount of electricity. For example, in some exemplary embodiments, the energy storage unit 180 may be configured to store at least about fifty kilowatt-hours of electricity, such as at least about sixty-five kilowatt-hours of electricity, such as at least about seventy-five kilowatt-hours of electricity, and up to about one thousand kilowatt-hours of electricity.

[0042] The hybrid electric propulsion system 150 also includes a power management system with a controller 182 and a power bus 184. The motors 300A and 300B, the energy storage unit 180, and the controller 182 are each electrically connected to each other via one or more wires 186 of the power bus 184. For example, the power bus 184 may include various switches or other movable power electronic devices for selectively electrically connecting various components of the hybrid electric propulsion system 150. Specifically, such as... Figure 1 As shown, a first power converter 188A of the power bus 184 is electrically connected to or can be connected to the motor 300A via one or more wires 186, and a second power converter 188B of the power bus 184 is electrically connected to or can be connected to the motor 300B via one or more wires 186. The power bus 184 may include other power electronic devices (e.g., inverters, converters, rectifiers, etc.) for regulating or converting power within the hybrid electric propulsion system 150.

[0043] The controller 182 is structured to control power electronics to distribute electrical power among various components of the hybrid electric propulsion system 150. For example, the controller 182 can control power electronics of the power bus 184 to provide or draw electrical power to / from various components, such as the electric machines 300A, 300B, to operate the hybrid electric propulsion system 150 among various operating modes and perform various functions. This is schematically depicted as electrical wires 186 of the power bus 184 extending through the controller 182.

[0044] The controller 182 can form part of a computing system 190 of the aircraft 100. The computing system 190 of the aircraft 100 can include one or more processors and one or more memory devices embodied in one or more computing devices. For example, as shown, the computing system 190 includes the controller 182 as well as other computing devices, such as a computing device 192. The computing system 190 can also include other computing devices, such as an engine controller (not shown). The computing devices of the computing system 190 can be communicatively coupled to one another via a communication network. For example, the computing device 192 is located in a cockpit of the aircraft 100 and is communicatively coupled to the controller 182 of the hybrid electric propulsion system 150 via a communication link 194 of the communication network. The communication link 194 can include one or more wired or wireless communication links. Figure 1

[0045] For this embodiment, the computing device 192 is structured to receive and process inputs and / or other information, such as from a pilot or other crew member. In this manner, as one example, one or more processors of the computing device 192 can receive an input indicative of a command to change a thrust output of the first propulsor 200A and / or the second propulsor 200B and can cause the controller 182 to control electrical power drawn from or delivered to one or both of the electric machines 300A, 300B in response to the input to ultimately change the thrust output of one or both of the propulsors 200A, 200B.

[0046] The controller 182 and other computing devices of the computing system 190 of the aircraft 100 can be structured substantially the same as (and can be structured to perform one or more functions of) the example computing devices of the computing system 700 described below with reference to Figure 15

[0047] A schematic view of the first propulsor 200A of the hybrid electric propulsion system 150 of the aircraft 100 is provided in FIG. 1. Although the first propulsor 200A is shown, it should be understood that the second propulsor 200B can be structured in the same or similar manner as the first propulsor 200A depicted in FIG. 1. Figure 2 Figure 1 Figure 2 ​​​​Figure 2 An exemplary gas turbine engine is configured as a single unannular, non-pipeline rotor engine 210A defining an axial direction A, a radial direction R, and a circumferential direction C. The engine 210A also defines a central longitudinal axis 214.

[0048] As shown in Figure 2 The engine 210A takes the form of an open rotor propulsion system and has a rotor assembly 212 including an array of airfoils arranged about the central longitudinal axis 214 of the engine 210A. More specifically, the rotor assembly 212 includes an array of rotor blades 216 arranged about the central longitudinal axis 214 of the engine 210A. In addition, as will be explained in greater detail below, the engine 210A also includes a non-rotating vane assembly 218 positioned aft of the rotor assembly 212 (i.e., not rotating relative to the central axis 214). The non-rotating vane assembly 218 includes an array of airfoils also arranged about the central axis 214. More specifically, the vane assembly 218 includes an array of vanes 220 arranged about the central longitudinal axis 214.

[0049] The rotor blades 216 are arranged in generally equally spaced relationship about the central longitudinal axis 214, and each blade has a root 222 and a tip 224 with a span defined therebetween. Similarly, the vanes 220 are also arranged in generally equally spaced relationship about the central longitudinal axis 214, and each vane has a root 226 and a tip 228 with a span defined therebetween. The rotor assembly 212 also includes a hub 245 positioned forward of the plurality of rotor blades 216.

[0050] In addition, the engine 210A includes a turbomachine 230 having a core (or high pressure / high speed system) 232 and a low pressure / low speed system. It should be understood that the terms "speed" and "pressure" are used interchangeably with respect to the high pressure / high speed system and the low pressure / low speed system as used herein. Moreover, it should be understood that the terms "high" and "low" are used in the same context to differentiate between the two systems and are not meant to imply any absolute speed and / or pressure values.

[0051] The core 232 generally includes a high speed compressor 234, a high speed turbine 236, and a high speed shaft 238 extending between and connecting the high speed compressor 234 and the high speed turbine 236. The high speed compressor 234, the high speed turbine 236, and the high speed shaft 238 can be collectively referred to as a high speed spool 253 of the engine. In addition, a combustion section 240 is positioned between the high speed compressor 234 and the high speed turbine 236. The combustion section 240 can include one or more configurations for receiving a mixture of fuel and air and providing a flow of combustion gases through the high speed turbine 236 to drive the high speed spool 253.

[0052] The low speed system includes a low speed turbine 242, a low speed compressor 244 or booster, and a low speed shaft 246 extending therebetween and connecting the low speed compressor 244 and the low speed turbine 242. The low speed compressor 244, the low speed turbine 242, and the low speed shaft 246 can be collectively referred to as a low speed spool 255 of the engine.

[0053] Although the engine 210A is depicted as having the low speed compressor 244 positioned forward of the high speed compressor 234, in certain embodiments, the compressors 234, 244 can be in a finger-four arrangement. Additionally or alternatively, although the engine 210A is depicted as having the high speed turbine 236 positioned forward of the low speed turbine 242, in certain embodiments, the turbines 236, 242 can similarly be in a finger-four arrangement.

[0054] To support the rotating components of the engine 210A, the engine 210A includes a number of bearings that couple the rotating components to various structural components. In particular, as shown, a bearing 290 supports and facilitates rotation of the low speed shaft 246. Further, a bearing 292 supports and facilitates rotation of the high speed shaft 238. Although the bearings 290, 292 are shown as being located generally at the forward and aft ends of their associated shafts 246, 238, the bearings 290, 292 can be positioned at any desired location along their associated shafts. Further, in some embodiments, one or more additional bearings can be used to support the low speed shaft 246 in addition to the bearing 290 shown in Figure 2 Further, in some embodiments, one or more additional bearings can be used to support the high speed shaft 238 in addition to the bearing 292 shown in Figure 2 For example, in some embodiments, an additional bearing can be positioned at the center or midspan region of the low speed shaft 2462 to provide support thereto. Similarly, one or more additional bearings can be used to support the high speed shaft 238 in addition to the bearing 292 shown in Figure 2 The bearings 290, 290 can be any suitable type of bearing, such as an air bearing, an oil lubricated bearing, etc.

[0055] Still referring to FIG. 2, the engine 210A includes a high speed compressor 234 and a high speed turbine 236. The high speed compressor 234 is in flow communication with the high speed turbine 236 such that working fluid can flow therebetween. The high speed compressor 234 is positioned forward of the high speed turbine 236. The high speed compressor 234 and the high speed turbine 236 are connected to one another by a high speed shaft 238 that extends therebetween. The high speed compressor 234, the high speed turbine 236, and the high speed shaft 238 can be collectively referred to as a high speed spool 232 of the engine 210A. Figure 2, the turbine 230 is generally enclosed in a shroud 248. Further, it should be appreciated that the shroud 248 at least partially defines an inlet 250 and an exhaust 252, and includes a turbomachinery flow path 254 extending between the inlet 250 and the exhaust 252. For the illustrated embodiment, the inlet 250 is an annular or axisymmetric 360-degree inlet 250 that is located between the rotor assembly 212 and the fixed or stationary vane assembly 218 along the axial direction A, and provides a path for incoming atmospheric air to enter the turbomachinery flow path 254 (and the compressor 244, 234, the combustion section 240, and the turbines 236, 242) inside the guide vanes 220 along the radial direction R. Such a location can be advantageous for various reasons, including management of icing performance and protection of the inlet 250 from various objects and materials that can be encountered in operation. However, in other embodiments, the inlet 250 can be positioned at any other suitable location (e.g., aft of the vane assembly 218), arranged in a non-axisymmetric manner, etc.

[0056] As shown, the rotor assembly 212 is driven by the turbine 230, and more particularly, by a low speed spool 255 of the turbine 230. More specifically, for this embodiment, the engine 210A includes a power gear box 256. The rotor assembly 212 is driven by the low speed spool 255 of the turbine 230 across the power gear box 256. In this manner, the rotating rotor blades 216 of the rotor assembly 212 can be rotated about the central longitudinal axis 214 and generate thrust to propel the engine 210A, and thus the aircraft 100 associated therewith in the forward direction F. Figure 1 The power gear box 256 can include a set of gears for reducing the rotational speed of the low speed spool 255 relative to the low speed turbine 242, such that the rotor assembly 212 can be rotated at a slower rotational speed than the low speed spool 255.

[0057] As noted above, the engine 210A includes a vane assembly 218. The vane assembly 218 extends from the shroud 248 and is positioned aft of the rotor assembly 212. The vanes 220 of the vane assembly 218 can be mounted to a stationary frame or other mounting structure, and do not rotate relative to the central longitudinal axis 214. For reference purposes, Figure 2 The forward direction is depicted with arrow F, which in turn defines a forward portion and an aft portion of the engine 210A. As Figure 2As shown, the rotor assembly 212 is positioned forward of the turbine 230 in a "puller" configuration, while the exhaust 252 is positioned aft of the guide vanes 220. The vanes 220 of the vane assembly 218 are aerodynamically shaped to streamline the airflow from the rotor assembly 212 (e.g., to reduce swirl in the airflow) to improve the efficiency of the engine 210A. For example, the size, shape, and configuration of the vanes 220 can be designed to impart counter-swirl to the airflow from the rotor blades 216, such that the degree of swirl in the airflow is greatly reduced in a downstream direction aft of the two rows of airfoils (e.g., blades 216, vanes 220), which can translate into an increased level of induced efficiency.

[0058] In some embodiments, it can be desirable for the rotor blades 216, vanes 220, or both, to incorporate a variable pitch mechanism, such that the airfoils (e.g., blades 216, vanes 220, etc.) can be independently or in combination with one another rotated relative to a pitch axis of rotation. Such variable pitch can be used to alter thrust and / or swirl effects under various operating conditions, including to adjust the magnitude or direction of thrust generated at the rotor blades 216, or to provide a reverse thrust feature that can be useful under certain operating conditions (e.g., when the aircraft is landing), or desirably adjust the acoustic noise generated at least in part by the rotor blades 216, vanes 220, or the aerodynamic interaction from the rotor blades 216 relative to the vanes 220. More particularly, for embodiments in which the rotor assembly 212 is depicted as having a variable pitch mechanism 258 for rotating the rotor blades 216 about their respective pitch axes 260, and the vane assembly 218 is depicted as having a variable pitch mechanism 262 for rotating the vanes 220 about their respective pitch axes 264. Figure 2 In some embodiments, it can be desirable for the rotor blades 216, vanes 220, or both, to incorporate a variable pitch mechanism, such that the airfoils (e.g., blades 216, vanes 220, etc.) can be independently or in combination with one another rotated relative to a pitch axis of rotation. Such variable pitch can be used to alter thrust and / or swirl effects under various operating conditions, including to adjust the magnitude or direction of thrust generated at the rotor blades 216, or to provide a reverse thrust feature that can be useful under certain operating conditions (e.g., when the aircraft is landing), or desirably adjust the acoustic noise generated at least in part by the rotor blades 216, vanes 220, or the aerodynamic interaction from the rotor blades 216 relative to the vanes 220. More particularly, for embodiments in which the rotor assembly 212 is depicted as having a variable pitch mechanism 258 for rotating the rotor blades 216 about their respective pitch axes 260, and the vane assembly 218 is depicted as having a variable pitch mechanism 262 for rotating the vanes 220 about their respective pitch axes 264.

[0059] The example single-rotor un ducted engine 210A depicted in FIG. 1 is provided by way of example only. Figure 2 It should be appreciated, therefore, that the engine 210A can have other suitable configurations. For example, in other example embodiments, the engine 210A can have other suitable numbers of shafts or spools, turbines, compressors, etc.; fixed pitch blades 216 or vanes 220 or both; a direct drive configuration (i.e., can not include a gearbox 256); etc. For example, in other example embodiments, the engine 210A can be a three spool engine having a mid-speed compressor and / or turbine. In such configurations, it should be appreciated that the terms "high" and "low" used herein with respect to the speed and / or pressure of the turbines, compressors, or spools are convenient terms to differentiate the components, but do not require any particular relative speed and / or pressure, and do not preclude additional compressors, turbines, and / or spools or shafts.

[0060] Additionally or alternatively, in other example embodiments, any other suitable gas turbine engine can be provided. For example, in other example embodiments, the gas turbine engine can be a turboshaft engine, a turboprop engine, a turbojet engine, etc. Moreover, for example, while the engine is depicted as a single unannular rotor engine, in other embodiments, the engine can include a multi-stage open rotor configuration, and aspects of the present disclosure described below can be incorporated therein.

[0061] Moreover, in other example embodiments, the engine 210A can be configured as a ducted turbofan engine. For example, referring briefly to Figure 3 , an engine 210A according to another example embodiment of the present disclosure is depicted. Except as noted below, the engine 210A can be configured in substantially the same manner as the example engine 210A described above with respect to Figure 3 , the example engine 210A can be configured in substantially the same manner as the example engine 210A described above with respect to Figure 2 , the example engine 210A can be configured in substantially the same manner as the example engine 210A described above with respect to Figure 3 , the example engine 210A can be configured in substantially the same manner as the example engine 210A described above with respect to

[0062] Referring again to Figure 2 As noted above, the first propulsor 200A includes an electric machine 300A operatively coupled with a rotating component thereof. In this regard, the first propulsor 200A is an aerospace hybrid-electric propulsion machine. In particular, as shown in Figure 2 , the electric machine 300A is operatively coupled with the low speed spool 255 of the gas turbine engine 210A, and more particularly, with the low speed shaft 246 of the low speed spool 255. As shown, the electric machine 300A is embedded within the core of the gas turbine engine 210A. In particular, the electric machine 300A is positioned radially inward of the turbomachinery flow path 254 along the radial direction R. Moreover, for this embodiment, the electric machine 300A is positioned generally at the aft end of the gas turbine engine 210A, and at least partially overlaps or aft of the low pressure turbine 242 along the axial direction A. However, in other example embodiments, the electric machine 300A can be positioned at other suitable locations within the gas turbine engine 210A. For example, in some embodiments, the electric machine 300A can be coupled with the low speed spool 255 at other suitable locations. For example, in some embodiments, the electric machine 300A can be positioned forward of the low pressure compressor 244 along the axial direction A, and radially inward of the turbomachinery flow path 254 along the radial direction R. Moreover, as Figure 2As shown, motor 300A, which is operably coupled with low speed shaft 246, is electrically coupled with power bus 184 and is electrically connected to its associated power converter power source 188A.

[0063] In addition to or in lieu of gas turbine engine 210A having motor 300A coupled to low speed spool 255, in some embodiments, gas turbine engine 210A can include motor 302A operably coupled with high speed spool 253 of gas turbine engine 210A, and more particularly, with high speed shaft 238 of high speed spool 253. As shown, Figure 2 As shown, motor 302A is embedded within the core of gas turbine engine 210A and is operably coupled with high speed shaft 238. Motor 302A is positioned radially inward of turbomachinery flow path 254 along radial direction R and is positioned forward of combustion section 140 along axial direction A. However, in other example embodiments, motor 302A can be positioned at other suitable locations within gas turbine engine 210A. Although not shown, motor 302A, which is operably coupled with high speed shaft 238, can be electrically coupled with power bus 184 and can be electrically connected to its own power converter power source.

[0064] Similar to motor 300A, which is mechanically coupled to low speed spool 255, motor 302A, which is mechanically coupled to high speed spool 253, can be an electric motor that is operable to drive or propel high speed shaft 238, for example, during an engine burst. In other embodiments, motor 302A can be a generator that is operable to convert mechanical energy into electrical energy. In this manner, electrical power generated by motor 302A can be directed to various engine and / or aircraft systems. In some embodiments, motor 302A can be a dual function electric motor / generator.

[0065] Figure 4A close-up schematic view of an electric machine 300A embedded within a gas turbine engine 210A is provided. As shown, the electric machine 300A defines a centerline 304 that, in this example embodiment, is aligned with or coaxial to the central longitudinal axis 214 of the gas turbine engine 210A. The electric machine 300A includes a rotor assembly 310 and a stator assembly 340. The rotor assembly 310 includes a rotor 312, and the stator assembly 340 includes a stator 342. The rotor 312 of the rotor assembly 310 and the stator 342 of the stator assembly 340 together define an air gap 306 therebetween. Further, for this embodiment, the rotor 312 includes a plurality of magnets 314 (e.g., a plurality of permanent magnets), and the stator 342 includes a plurality of windings or coils 344. Thus, the electric machine 300A can be referred to as a permanent magnet electric machine. However, in other example embodiments, the electric machine 300A can be constructed in any suitable manner. For example, the electric machine 300A can be constructed as an electromagnetic electric machine (including a plurality of electromagnets and active circuitry), an induction electric machine, a switched reluctance electric machine, a synchronous AC electric machine, an asynchronous electric machine, or any other suitable type of electric machine.

[0066] The rotor assembly 310 also includes a rotor connection assembly 316. Generally, the rotor connection assembly 316 operably couples the rotor 312 with the low speed shaft 246. Because the rotor assembly 310 of the electric machine 300A is coupled with or attached to the low speed shaft 246, the rotor assembly 310 is rotatable with the low speed shaft 246. As shown, the rotor connection assembly 316 has a rotor hub 318 and a rotor connection member 320. The rotor hub 318 is connected to the low speed shaft 246, and the rotor connection member 320 is connected to the rotor 312. The rotor hub 318 and the rotor connection member 320 are mechanically coupled or connected to one another by an insulating joint 322. Notably, the insulating joint 322 of the rotor connection assembly 316 interrupts the flow of common mode current between the rotor 312 and the low speed shaft 246, e.g., from the rotor 312 to the low speed shaft 246. In this way, among other components, the flow of common mode current to one or more bearings that support the low speed shaft 246 is prevented. Reference will be made to the insulating joint 322 below. Figure 6 The insulating joint 322 is further described.

[0067] For this embodiment, the rotor hub 318 of the rotor connection assembly 316 is connected to the low speed shaft 246 by a splined connection. More particularly, the rotor hub 318 includes a connection portion having a plurality of teeth 324. Similarly, the low speed shaft 246 includes a connection portion having a plurality of teeth 247. The plurality of teeth 324 of the rotor hub 318 are configured to engage with the plurality of teeth 247 of the low speed shaft 246, thereby securing the two components to one another. In alternative embodiments, the rotor hub 318 can be coupled to the low speed shaft 246 in any other suitable manner.

[0068] The stator assembly 340 also includes a stator connection assembly 346. The stator connection assembly 346 includes a stator connection member 348 that supports the stator 342. The stator connection member 348 is connected to a structural support member 266 of a turbine section of the gas turbine engine 210A. The structural support member 266 can be configured as part of an aft frame assembly of the gas turbine engine 210A. The aft frame assembly can include aft struts 268 that extend through the turbomachinery flow path 254 in the radial direction R Figure 2 ). The aft frame struts 268 provide structural support for aft ends of the shrouds 248.

[0069] The gas turbine engine 210A also includes a cavity wall 270 that surrounds at least a portion of the electric machine 300A. More specifically, the cavity wall 270 substantially completely surrounds the electric machine 300A, extending in the axial direction A from a location proximate a forward end of the electric machine 300A to a location aft of the electric machine 300A. The cavity wall 270 can function as, for example, a cooling air cavity wall, a sump for a cooling fluid, a protective cover for the electric machine 300A, etc. In some embodiments, the gas turbine engine 210A can also include a second cavity wall (not shown) to form a buffer cavity that surrounds the electric machine 300A. The buffer cavity formed by the second cavity wall can thermally protect the electric machine 300A.

[0070] During certain operations of the gas turbine engine 210A, the low speed shaft 246 rotates the rotor assembly 310 of the electric machine 300A, thereby allowing the electric machine 300A to generate electrical power. Thus, the electric machine 300A can be operated in a generator mode. In some embodiments, in addition to or in lieu of being operable in the generator mode, the electric machine 300A can be operated in a drive mode during certain operations of the gas turbine engine 210A. In the drive mode, the rotor assembly 310 of the electric machine 300A drives the low speed shaft 246. For example, when the electric machine 300A is operated in the drive mode, the power converter 188A Figure 2 ) can be controlled to provide electrical power to the electric machine 300A via the electrical wires 186, and, for example, when the electric machine 300A is operated in the generator mode, electrical power generated by the electric machine 300A can be carried or transmitted via the electrical wires 186 to the power converter 188A Figure 2 ) and ultimately to various electrical loads. As best shown in FIG. 1 1, the electrical wires 186 of the power bus 184 can extend through the turbomachinery flow path 254 (e.g., through the aft frame struts 268) and electrically connect the electric machine 300A to the power converter 188A and ultimately to one or more electrical loads (accessory systems, electric / hybrid electric propulsion devices, etc.), power sources (other electric machines, electrical energy storage units, etc.), or both. Figure 2

[0071] Although the electric machine 300A has been described as being operable in the drive mode, it is contemplated that the electric machine 300A can be operable in other modes. For example, the electric machine 300A can be operable in a brake mode. In the brake mode, the electric machine 300A can be operated to generate a braking torque on the low speed shaft 246. For example, when the electric machine 300A is operated in the brake mode, the power converter 188A Figure 4 ​While described and shown as having a specific construction, it should be understood that the inventive aspects of this disclosure can be applied to motors with alternative constructions. For example, stator assembly 340 and / or rotor assembly 310 may have different constructions or may be configured similarly to... Figure 4 The different arrangements shown are illustrated. As an example, motor 300A can have, for instance, the following configurations. Figure 5 The internal rotor configuration shown is not... Figure 4 The external rotor structure is shown. In, as... Figure 5 In the inner rotor configuration shown, the rotor 312 is positioned inside the stator 342 along the radial direction R. In the outer rotor configuration, as... Figure 4 As shown, the rotor 312 is positioned on the outside of the stator 342 in the radial direction R. As another example, in some embodiments, the motor 300A may have a tapered configuration, wherein the rotor 312 and the stator 342 may extend longitudinally in the axial direction A at an angle relative to the central longitudinal axis 214, for example, such that they are not oriented parallel to the central longitudinal axis 214.

[0072] As previously stated, the inventors of this disclosure have developed various solutions for mitigating current in bearings supporting the shaft of a gas turbine engine connected to an electric motor. Such solutions can be used individually or in combination. For example, in one exemplary aspect, a three-pronged solution can be implemented. The three-pronged solution may include: 1) reducing the common-mode voltage reaching the motor from the connected power converter; 2) interrupting the common-mode current conduction path between the motor's rotor and the shaft connected to it; and 3) grounding at least one of the components connecting the motor's rotor and shaft.

[0073] As an example and reference Figure 2 and Figure 4 In the first aspect, the common-mode voltage from its associated power converter 188A to the motor 300A can be reduced via an electromagnetic interference (EMI) filter. For this embodiment, for example, the power converter 188A has an EMI filter 189A, which is operable to reduce the common-mode voltage from the power converter 188A to the motor 300A. Furthermore, the power converter 188A can be electrically connected to the motor 300A via one or more shielded cables. Specifically, as... Figure 4 As best shown, the wire 186 connecting the motor 300A to the power converter 188A may include one or more shielded cables. In addition to or as a substitute for shielded cables, the power converter 188A may be electrically connected to the motor 300A via one or more shielded busbars.

[0074] In the second aspect, refer to Figure 4 and 5The common mode current conduction path between the rotor 312 of the electric machine 300A and the low speed shaft 246 can be interrupted by the insulating joint 322. Figure 6 A close-up cross-sectional view of the insulating joint 322 taken from section 5 of FIG. 4 is provided. As shown, in this embodiment, the insulating joint 322 is an insulating bolt joint. The insulating joint 322 is formed collectively by a bolt 330, various insulating components, and components of the rotor connection assembly 316. Figure 4 A close-up cross-sectional view of the insulating joint 322 taken from section 5 of FIG. 4 is provided. As shown, in this embodiment, the insulating joint 322 is an insulating bolt joint. The insulating joint 322 is formed collectively by a bolt 330, various insulating components, and components of the rotor connection assembly 316.

[0075] As best shown in FIG. 4, the rotor hub 318 includes a hub flange 326 and the rotor connection member 320 includes a connection flange 328. The hub flange 326 extends in a plane that is orthogonal to the axial direction A. Likewise, the connection flange 328 extends in a plane that is orthogonal to the axial direction A. The hub flange 326 and the connection flange 328 are in communication with one another such that the bolt 330 can extend through the hub flange 326 and the connection flange 328. More specifically, the hub flange 326 defines an aperture that is in communication with an aperture defined by the connection flange 328. The bolt 330 extends through the aperture defined by the hub flange 326 and through the aperture defined by the connection flange 328 to secure the rotor connection member 320 with the rotor hub 318. A nut 338 can be threaded onto the bolt 330 to further secure the rotor connection member 320 with the rotor hub 318. Figure 6 The bolt 330 has a head 332 and a shank 334 extending from the head 332. The head 332 has a larger diameter than the shank 334. For this embodiment, the head 332 of the bolt 330 is positioned on the hub flange side of the insulating joint 322. The shank 334 of the bolt 330 extends through the hub flange 326 and the connection flange 328, and a distal end of the shank 334 is positioned on the connection flange side of the insulating joint 322. As shown, the nut 338 is secured to the portion of the shank 334 that is positioned on the connection flange side of the insulating joint 322. In this regard, the head 332 of the bolt 330 and the nut 338 clamp or otherwise couple the rotor hub 318 and the rotor connection member 320 together. The bolt 330 and the nut 338 can be formed of an electrically conductive material, such as a suitable metallic material. In other embodiments, the head 332 of the bolt 330 and the nut 338 can be positioned on opposite sides as shown in FIG. 4.

[0076] Figure 6 As further shown in FIG. 4, the insulating joint 322 includes a plurality of insulating members. Each of the insulating members is formed of an electrically insulating material, such as a ceramic material. Generally, the insulating members electrically isolate the rotor connection member 320 and the rotor hub 318, and thus, the rotor 312 from the low speed shaft 246. In this regard, the common mode current conduction path between the rotor 312 of the electric machine 300A and the low speed shaft 246 can be interrupted by the insulating joint 322.

[0077] As further shown in FIG. 4, the insulating joint 322 includes a plurality of insulating members. Each of the insulating members is formed of an electrically insulating material, such as a ceramic material. Generally, the insulating members electrically isolate the rotor connection member 320 and the rotor hub 318, and thus, the rotor 312 from the low speed shaft 246. In this regard, the common mode current conduction path between the rotor 312 of the electric machine 300A and the low speed shaft 246 can be interrupted by the insulating joint 322. Figure 6 As further shown in FIG. 4, the insulating joint 322 includes a plurality of insulating members. Each of the insulating members is formed of an electrically insulating material, such as a ceramic material. Generally, the insulating members electrically isolate the rotor connection member 320 and the rotor hub 318, and thus, the rotor 312 from the low speed shaft 246. In this regard, the common mode current conduction path between the rotor 312 of the electric machine 300A and the low speed shaft 246 can be interrupted by the insulating joint 322.​

[0078] for Figure 6 In the illustrated embodiment, the insulating components include a hub gasket 333, a mating gasket 335, and a connecting gasket 337. As described above, each insulating component, including the hub gasket 333, mating gasket 335, and connecting gasket 337, is formed of an insulating material. The hub gasket 333 is positioned, for example, along the axial direction A between the head 332 of the bolt 330 and the hub flange 326. The hub gasket 333 extends a distance along the radial direction R such that the head 332 of the bolt 330 does not physically contact the hub flange 326 of the rotor hub 318, as... Figure 6 As shown.

[0079] Typically, the engagement shim 335 is positioned between the rotor hub 318 and the rotor connecting member 320 such that they do not physically contact each other. Specifically, as shown, the engagement shim 335 is positioned, for example, along the axial direction A between the hub flange 326 of the rotor hub 318 and the connecting flange 328 of the rotor connecting member 320. Furthermore, in this embodiment, the engagement shim 335 is also positioned, for example, along the radial direction R between the outer member 329 of the hub flange 326 and the rotor connecting member 320. In this way, in this example embodiment, the engagement shim 335 has an L-shaped cross-section. However, in other example embodiments, the engagement shim 335 can have any suitable cross-sectional shape.

[0080] A connecting washer 337 is positioned, for example, axially between the connecting flange 328 and the nut 338. The connecting washer 337 extends radially R a certain distance so that the nut 338 does not physically contact the connecting flange 328 of the rotor connecting member 320. Figure 6 As shown.

[0081] Hub washer 333, mating washer 335, and connecting washer 337 may each define an orifice. The orifices defined by washer 333, 335, and 337, and the orifices defined by hub flange 326 and connecting flange 328, may communicate with each other. In this way, bolt 330 may extend through hub washer 333, hub flange 326, mating washer 335, connecting flange 328, and connecting washer 337. Bolt 330 may also extend through nut 338 and may be threadedly engaged with nut 338.

[0082] Furthermore, in this embodiment, the threads or circumference of the shank 334 of the bolt 330 are coated with an insulating coating 339, such as a ceramic coating. Figure 6As shown, the insulating coating 339 can extend substantially along the axial length of the shank 334. The shank 334 can engage (e.g., threaded engagement) the hub flange 326, the connecting flange 328, and the nut 338, all of which can be formed of a conductive material. The insulating coating 339 on the bolt 330 prevents current from flowing between these conductive elements. Thus, the insulating coating 339 on the bolt 330, together with the insulating members including the hub gasket 333, the engagement gasket 335, and the connecting gasket 337, electrically isolates the rotor connecting member 320 from the rotor hub 318. As a result, the common-mode current conduction path between the rotor 312 of the motor 300A and the low-speed shaft 246 can be interrupted by the insulating joint 322. Advantageously, among other benefits, this prevents common-mode current from reaching the bearing 290 supporting the low-speed shaft 246. Figure 2 ).

[0083] In some alternative embodiments, the entire outer surface of the bolt 330 may be coated with an insulating coating 339. In still other embodiments, instead of an insulating coating 339, an insulating sleeve (not shown) may extend circumferentially around the shank 334 of the bolt 330 and axially along the shank 334 of the bolt 330, such that the bolt 330 does not engage with other conductive parts of the insulating connector 322.

[0084] In some further embodiments, the hub flange 326 and connecting flange 328 may be coated with an insulating coating 339, particularly around the circumference of the bores 317, 319 through which the bolt 330 extends. In addition to or instead of the bolt 330 being coated with the insulating coating 339, the hub flange 326 and connecting flange 328 may be coated with the insulating coating 339. In yet another embodiment, the insulating joint 322 does not include any insulating components; instead, the bolt 330, nut 338, and flanges 326, 328 are all coated with the insulating coating 339, where they are physically joined to each other. The insulating coating 339 can be applied using suitable techniques, such as by electrophoretic deposition or via electrostatic coating treatment. Such techniques can provide an insulating powder coating on the desired surface, ultimately electrically isolating the rotor connecting member 320 and the rotor hub 318, thereby electrically isolating the rotor 312 from the low-speed shaft 246. In this way, the common-mode current conduction path between the rotor 312 and the low-speed shaft 246 of the motor 300A can be interrupted by the insulating joint 322.

[0085] In some further embodiments, the rotor hub 318 and / or rotor connecting member 320 may include one or more insulating layers. For example, for Figure 7 In the illustrated embodiment, the hub flange 326 includes multiple double-layer insulation layers, including a hub-side insulation layer, a mating-side insulation layer, and an orifice insulation layer. Figure 7 For clarity, bolt 330 and associated nut 338 have been removed (see [link]).Figure 6 The hub-side insulation layer includes an outer layer 400 and an inner layer 402. The outer layer 400 forms the outer surface of the hub side of the hub flange 326. A metal layer 404 is sandwiched or positioned between the outer layer 400 and the inner layer 402, for example, along the axial direction A. The mating-side insulation layer includes an outer layer 410 and an inner layer 412. The outer layer 410 forms the outer surface of the mating side of the hub flange 326. The outer layer 410 and the inner layer 412 may also extend along the outer member 329 of the hub flange 326. A metal layer 414 is sandwiched or positioned between the outer layer 410 and the inner layer 412, for example, along the outer member 329 of the hub flange 326 in the axial direction A and the radial direction R. Furthermore, the orifice insulation layer includes an outer layer 420 and an inner layer 422. The orifice insulation layer generally extends circumferentially around the orifice 317 defined by the hub flange 326 of the rotor hub 318. Metal layer 424 is sandwiched or positioned, for example, in the radial direction R, between outer layer 420 and inner layer 422. In some embodiments, the orifice insulation layer may consist of only a single layer (e.g., outer layer 420) extending circumferentially along the circumference defining orifice 317. Each insulation layer of rotor hub 318 may be formed of an electrically insulating material (e.g., ceramic material).

[0086] like Figure 7 As further described, the connecting flange 328 includes a connecting-side insulating layer, a mating-side insulating layer, and an orifice insulating layer. The connecting-side insulating layer includes an outer layer 430 and an inner layer 432. The outer layer 430 forms the outer surface of the connecting side of the connecting flange 328. A metal layer 434 is sandwiched or positioned, for example, along the axial direction A, between the outer layer 430 and the inner layer 432. The mating-side insulating layer includes an outer layer 440 and an inner layer 442. The outer layer 440 forms the outer surface of the mating side of the connecting flange 328. The outer layer 440 and the inner layer 442 may also extend longitudinally along the axial direction A to complement the mating insulating layers 410, 412 extending along the outer member 329 of the hub flange 326. The metal layer 444 is sandwiched or positioned between the outer layer 440 and the inner layer 442. Furthermore, the orifice insulating layer includes an outer layer 450 and an inner layer 452. The orifice insulation layer typically extends circumferentially around the orifice 319 defined by the connecting flange 328 of the rotor connecting member 320. A metal layer 454 is sandwiched or positioned, for example, radially R, between the outer layer 450 and the inner layer 452. In some embodiments, the orifice insulation layer may consist of only a single layer (e.g., the outer layer 450) extending circumferentially along the circumference defining the orifice 319. Each insulation layer of the rotor connecting member 320 may be formed of an electrically insulating material, such as a ceramic material.

[0087] Notably, the strategic arrangement of the insulating layers of the rotor hub 318 and the rotor connecting member 320 can electrically isolate the rotor connecting member 320 and the rotor hub 318, and thus, the rotor 312 from the low speed shaft 246. In this regard, the common mode current conduction path between the rotor 312 and the low speed shaft 246 of the electric machine 300A can be interrupted by the insulating joint 322. Moreover, in such embodiments, the bolts 330 and corresponding nuts 338 Figure 7 (not shown; see Figure 6 ) can, but need not, be coated with an insulating material. Furthermore, in such embodiments, insulating members (e.g., insulating washers of Figure 6 ) can, but need not, be arranged between components as shown in Figure 6 . Moreover, among other benefits, Figure 7 the double layer arrangement of the insulating layers shown in allows for easy replacement of the outer layer upon wear and also provides an additional insulating layer.

[0088] In some alternative embodiments, as shown in Figure 8 , both the hub flange 326 and the connecting flange 328 include a plurality of single layer insulating layers. In particular, the hub flange 326 includes a hub side insulating layer 460, a joint side insulating layer 462, and an aperture insulating layer 464. The connecting flange 328 includes a connecting side insulating layer 466, a joint side insulating layer 468, and an aperture insulating layer 470. Each of the insulating layers of the rotor hub 318 and the rotor connecting member 320 can be formed of an electrically insulating material, such as a ceramic material. In Figure 8 , the bolts 330 and associated nuts 338 (see Figure 6 ) are removed for clarity of illustration.

[0089] Notably, due to the strategic arrangement of the insulating layers 460, 462, 464, 466, 468, 470, the rotor hub 318 and the rotor connecting member 320 can electrically isolate the rotor connecting member 320 and the rotor hub 318, and thus, the rotor 312 from the low speed shaft 246. In this regard, the common mode current conduction path between the rotor 312 and the low speed shaft 246 of the electric machine 300A can be interrupted by the insulating joint 322. Moreover, the bolts 330 and corresponding nuts 338 Figure 8 (not shown; see Figure 6 ) can, but need not, be coated with an insulating material. Furthermore, in such embodiments, insulating members (e.g., insulating washers of Figure 6 ) can, but need not, be arranged between components as shown in Figure 6 .

[0090] In a third aspect for mitigating bearing currents, again referring to Figure 4 , at least one of the members connecting the rotor 312 of the electric machine 320A and the low speed shaft 246 is electrically grounded by a grounding device 360. For example, as shown inFigure 4 As shown, the grounding device 360 is shown as electrically grounding the rotor hub 318, which, as previously mentioned, is a member that connects the rotor 312 of the electric machine 320A and the low speed shaft 246. Among other benefits, by electrically grounding the rotor hub 318, the bearings 290 supporting the low speed shaft 246 can be protected from common mode current surges or electrical overloads associated with the electric machine 310A. Figure 2 ) from common mode current surges or electrical overloads associated with the electric machine 310A.

[0091] As Figure 4 shown, the grounding device 360 can be electrically connected to the rotor hub 318 and the transmission cable 352 can electrically connect the grounding device 360 and a ground point, such as a grounding system 350 (shown schematically in FIG. 3B). The grounding system 350 can be any suitable grounding system, such as an aircraft grounding system. For example, on an aircraft having a highly conductive fuselage (e.g., an aluminum fuselage), the grounding system 350 can be the fuselage itself. On an aircraft having a fuselage with an insulated or low conductive fuselage (e.g., a carbon fiber fuselage), internal metal structures within the fuselage or other components of the aircraft (e.g., the wings, the cone, or the tail of the aircraft) can be used for the grounding system 350. Figure 4 For this embodiment, the grounding device 360 includes a stationary component 362 connected to a structure of the engine 210A, a rotating component 364 operably coupled with and rotatable with the rotor hub 318, and one or more electrical contacts 366 connected to one or both of the stationary component 362 and the rotating component 364. The electrical contacts 366 can be grounding brushes formed of a conductive material, such as a metal or carbon. The electrical contacts 366 allow current to flow between the stationary component 362 and the rotating component 364 to facilitate grounding of the rotor hub 318. The transmission cable 352 is electrically connected to the electrical contacts 366, and thus, the electrical contacts 366 are electrically coupled with the grounding system 350.

[0092] Notably, the grounding device 360 can be integrated into existing components of the gas turbine engine 210A. For example, in some embodiments, the grounding device 360 is integrated into a resolver that is operable to measure the rotational degrees or angular position of the rotor hub 318 and the low speed shaft 246 operably coupled thereto. Further, as the low speed shaft 246, the rotor hub 318, and the rotating component 364 rotate about the central longitudinal axis 214, the electrical contacts 366 connected to the stationary component 362 can contact the rotating component 364 coupled with the rotor hub 318 to provide an electrical grounding path. In this manner, the rotor hub 318 and the low speed shaft 246 can be electrically grounded. As mentioned above, the electrical contacts 366 can be grounding brushes. In this regard, the grounding brushes can be integrated into the resolver.

[0093]

[0094] ​Accordingly, in such embodiments, the resolver has a dual function in that it is operable to provide a ground connection point for electrically grounding the rotor hub 318 and the low speed shaft 246, and it measures the number of rotations or angular position of the rotor hub 318 and the low speed shaft 246. Integrating the electrical grounding function into the resolver can reduce the number of parts required to electrically ground the rotor hub 318 and the low speed shaft 246, can reduce the weight of the first propulsor 200A Figure 1 ), thereby reducing the weight of the aircraft 100( Figure 1 ), and can efficiently utilize space.

[0095] In alternative example embodiments, the grounding device 360 can be integrated into other suitable components. For example, in some embodiments, the grounding device 360 can be integrated into an encoder that is operable to measure the rotational speed of the rotor hub 318 and the low speed shaft 246 that is operably coupled thereto. Further, as the low speed shaft 246, the rotor hub 318, and the rotating component 364 rotate about the central longitudinal axis 214, the electrical contact 366 of the stationary component 362 that is connected to the encoder can contact the rotating component 364 of the encoder that is coupled with the rotor hub 318 to provide an electrical ground path. In this manner, the rotor hub 318 and the low speed shaft 246 can be electrically grounded. As noted above, the electrical contact 366 can be a grounding brush. In this regard, the grounding brush can be integrated into the encoder.

[0096] Accordingly, in such embodiments, the resolver has a dual function in that it is operable to provide a ground connection point for electrically grounding the rotor hub 318 and the low speed shaft 246, and it measures the number of rotations or angular position of the rotor hub 318 and the low speed shaft 246. Integrating the electrical grounding function into the resolver can reduce the number of parts required to electrically ground the rotor hub 318 and the low speed shaft 246, can reduce the weight of the first propulsor 200A Figure 1 ), thereby reducing the weight of the aircraft 100( Figure 1 ), and can efficiently utilize space.

[0097] As further depicted in Figure 4 , in some embodiments, the shaft current and / or shaft voltage can be measured by one or more sensors (represented by the sensors 380). For example, the sensors 380 can be integrated into the grounding brush circuit of the grounding device 360. The measured shaft current and / or shaft voltage can be provided to the controller 182 and / or other computing or control devices, for example, to facilitate control of the electric machine 300A and / or the gas turbine engine 210A.

[0098] Furthermore, in some embodiments, the grounding device 360 ​​can be integrated into existing seals of the gas turbine engine 210A. The grounding device 360 ​​can be integrated into any suitable type of existing seal, such as carbon seals, including face and radial carbon seals, finger seals, brush seals, labyrinth seals, etc. For example, as an example of integrating the grounding device 360 ​​into... Figure 4 As shown in the example of a rotary transformer or encoder, the grounding device 360 ​​can be integrated into the carbon seal 370, such as... Figure 9 As shown. The carbon seal 370 can be configured to seal the fluid (e.g., oil or air) within the chamber. The carbon seal 370 may include a stationary component and a rotating component. In this embodiment, the stationary component is a stationary carbon element 372 connected to a stationary structure of the engine 210A, and the rotating component is a ring 374 rotatable with a rotating shaft, which in this example embodiment is a low-speed shaft 246. The ring 374 may be formed of a conductive material (e.g., a metallic material). Similarly, the carbon element 372 may be state such that it is also conductive. In some alternative embodiments, the grounding element (carbon element 372 in this example embodiment) may be formed of a material other than carbon. For example, the grounding element may be formed of any suitable material that is conductive and has wear characteristics similar to carbon. For example, the grounding element may be formed of a suitable composite material, mixture, alloy, metal, or other material.

[0099] In addition, such as Figure 9 As shown, the carbon element 372 and / or the stationary structure on which the carbon element 372 is mounted can be electrically connected to a dedicated grounding system, such as grounding system 350. Transmission line 352 can be electrically connected to the carbon element 372 or an adjacent structure electrically connected to the carbon element 372. In this way, grounding system 350 can be used to electrically ground the low-speed shaft 246. In yet another embodiment, the carbon element 372 and / or its adjacent structure can provide a grounding system.

[0100] Therefore, when the low-speed shaft 246, rotor hub 318, and ring 374 rotate about the central longitudinal axis 214, an electrical grounding path (a current path that can extend through the fluid flowing therebetween) is created between the ring 374 and the carbon element 372. Thus, current can flow between the ring 374 and the carbon element 372. In this way, the low-speed shaft 246 and the rotor hub 318 can be electrically grounded. Therefore, in such an embodiment, the carbon seal 370 has a dual function, as it is operable to provide a grounding connection point for electrically grounding the low-speed shaft 246 and the rotor hub 318 operably connected to it, and operable to seal the fluid within the chamber. Among other benefits, integrating the electrical grounding function into the carbon seal 370 reduces the number of parts required to electrically ground the rotor hub 318 and the low-speed shaft 246, and can reduce the number of parts required for the first thruster 200A ( Figure 1 The weight of the aircraft is reduced by 100 (Figure 1 ) and can effectively utilize space.

[0101] Figure 10 A close-up cross-sectional view of another example grounding arrangement 360 integrated into a carbon seal 370 is provided in accordance with one example embodiment of the present disclosure. For this embodiment, the carbon seal 370 is an end face carbon seal. As shown, the carbon seal 370 includes a plurality of stationary components and rotating components. In particular, for this example embodiment, the stationary components include a first carbon element 480 and a second carbon element 482. Both the first carbon element 480 and the second carbon element 482 can be formed of an electrically conductive carbon material. In some alternative embodiments, the grounding elements (first carbon element 480 and second carbon element 482 in this example embodiment) can be formed of materials other than carbon. For example, the grounding elements can be formed of any suitable material that is electrically conductive and has similar wear characteristics to carbon. For example, the grounding elements can be formed of suitable composite materials, mixtures, alloys, metals, or other materials.

[0102] The second carbon element 482 is positioned radially outward of the first carbon element 480 along the radial direction R. For example, the first carbon element 480 and the second carbon element 482 can be carbon rings. The first carbon element 480 and the second carbon element 482 can be carried or held in place by a seal retainer 484, which is also a stationary component. The second carbon element 482 is positioned between two flanges of the seal retainer 484 along the radial direction R, while the first carbon element 480 is positioned radially inward of the two flanges of the seal retainer 484 along the radial direction R.

[0103] The rotating components are a seal runner 486, which is coupled to and rotates with the low speed shaft 246. In some alternative embodiments, the seal runner 486 can be coupled with the rotor hub 318. The seal runner 486 can be formed of an electrically conductive material, such as a metallic material. As shown, a spring 488 is positioned between the seal retainer 484 and a seal housing 494, for example, along the axial direction A. The spring 488 exerts a force on the seal retainer 484 that biases the first carbon element 480 and the second carbon element 482 into contact with the seal runner 486. As shown, a face 490 of the first carbon element 480 engages the seal runner 486, and a face 492 of the second carbon element 482 engages the seal runner 486. The face 492 of the second carbon element 482 engages a surface area of the seal runner 486 that is greater than the surface area of the face 490 of the first carbon element 480 that engages the seal runner 486. Figure 10

[0104] Thus, when the low speed shaft 246 and the seal runner 486 rotate about the central longitudinal axis 214 (FIG. 1), the first carbon element 480 and the second carbon element 482 rotate with the seal runner 486. The first carbon element 480 and the second carbon element 482 are biased into contact with the seal runner 486 by the spring 488. The first carbon element 480 and the second carbon element 482 are electrically conductive and thus provide an electrical path between the seal runner 486 and the seal housing 494. The first carbon element 480 and the second carbon element 482 also provide a mechanical path between the seal runner 486 and the seal housing 494. Thus, the first carbon element 480 and the second carbon element 482 provide an electrical and mechanical path between the seal runner 486 and the seal housing 494. Figure 9 ​) rotates, a first electrical ground path is created between the seal runner 486 and the first carbon element 480, and a second electrical ground path is created between the seal runner 486 and the second carbon element 482. Thus, electrical current can flow between the seal runner 486 and the first and second carbon elements 480, 482 along these paths. In some embodiments, the seal housing 494 can provide a ground system, or alternatively, the seal housing 494 can be electrically connected to the dedicated ground system 350 via the transmission line 352. In this way, the low speed shaft 246, and the rotor hub 318 Figure 9 ) to which it is operably coupled can be electrically grounded.

[0105] Thus, in such embodiments, the carbon seal 370 has a dual function in that it is operable to provide a ground connection point for electrically grounding the low speed shaft 246 and the rotor hub 318 operably coupled thereto, and is operable to seal the fluid within the chamber. The engagement of the first carbon element 480 with the seal runner 486 provides the sealing function as well as the first ground path, while the engagement of the second carbon element 482 provides the second ground path and increases the number of electrical connection points with the seal runner 486, which can provide improved electrical grounding of the low speed shaft 246. Among other benefits, integrating the electrical grounding function into the carbon seal 370 Figure 10 can reduce the number of parts required to electrically ground the rotor hub 318 and the low speed shaft 246, can reduce the weight of the first propulsor 200A Figure 1 ), thereby reducing the weight of the aircraft 100 Figure 1 ), and can efficiently utilize space.

[0106] Figure 11 A close-up cross-sectional view of a ground device 360 integrated into a carbon seal 370 according to another example embodiment of the present disclosure is provided. For this embodiment, the carbon seal 370 is a radial carbon seal. As shown, the carbon seal 370 includes a carbon element 500 having a face 502 that directly engages the low speed shaft 246. In alternative embodiments, the face 502 can engage the rotor hub 318 of the rotor connection assembly 316 Figure 9 ). The carbon element 500 can be formed of an electrically conductive carbon material. The carbon element 500 is carried or held by a seal retainer 504, which can be mechanically coupled with various support structures. A spring 506 is positioned between the seal retainer 504 and the carbon element 500. The spring 506 biases the carbon element 500 to a desired axial position.

[0107] When the low speed shaft 246 rotates about the central longitudinal axis 214 Figure 9 ), an electrical ground path is created between the low speed shaft 246 and the carbon element 500. Thus, electrical current can flow between the low speed shaft 246 and the carbon element 500. In some embodiments, the seal retainer 504 can provide a ground system, or alternatively asFigure 11 As shown, the seal retainer 504 can be electrically connected to the dedicated ground system 350 via the transmission line 352. In this way, the low speed shaft 246 and the rotor hub 318( Figure 9 ) can be electrically grounded. Among other benefits, integrating the electrical grounding function into the carbon seal 370 of the Figure 11 can reduce the number of parts required to electrically ground the rotor hub 318 and the low speed shaft 246, can reduce the weight of the first propulsor 200A( Figure 1 ), and thus the aircraft 100( Figure 1 ), and can efficiently utilize space.

[0108] Figure 12 A close-up cross-sectional view of the grounding device 360 integrated into the finger seal 510 according to example embodiments of the present disclosure is provided. As shown, the finger seal 510 includes a stack or plurality of finger elements 512. The plurality of finger elements 512 are positioned, for example, along the axial direction A between a first plate 514 and a second plate 516. The finger elements 512, the first plate 514, and the second plate 516 can be clamped or secured together in any suitable manner, for example, by one or more mechanical fasteners. The plates 514, 516 can be formed of an electrically conductive material, such as a metallic material. The finger elements 512 extend along the radial direction R to contact the low speed shaft 246. In alternative embodiments, the finger elements 512 can extend to contact other rotating elements coupled with the low speed shaft 246, for example, the rotor hub 318( Figure 9 ). The finger elements 512 can be formed of a flexible material. In this way, the finger elements 512 can accommodate displacement and / or deformation of the low speed shaft 246 while maintaining contact therewith. Further, the flexible material used for the finger elements 512 can also be an electrically conductive material.

[0109] In this regard, when the low speed shaft 246 is rotated about the central longitudinal axis 214( Figure 9 ), an electrical ground path is created between the low speed shaft 246 and the finger elements 512 of the finger seal 510. Accordingly, electrical current can flow between the low speed shaft 246 and the finger elements 512. In some embodiments, the plates 514, 516 can provide a ground system, or alternatively, the plates 514, 516 can be electrically connected to the dedicated ground system 350 via the transmission line 352, as Figure 12 shown. In this way, the low speed shaft 246 and the rotor hub 318( Figure 9 ) can be electrically grounded. Among other benefits, integrating the electrical grounding function into the finger seal 510 of the Figure 12 can reduce the number of parts required to electrically ground the rotor hub 318 and the low speed shaft 246, can reduce the weight of the first propulsor 200A( Figure 1 ), and thus the aircraft 100( Figure 1It weighs less and can make efficient use of space.

[0110] In other embodiments, as described above, the grounding device 360 ​​can be integrated into the brush seal, for example... Figure 13 The brush seal 520 is depicted. The brush seal 520 can be configured to seal the fluid (e.g., oil or air) within the chamber. Figure 13 As shown, the brush seal 520 includes a housing 522 spaced apart from the low-speed shaft 246, for example, in a radial direction R. The brush seal 520 also includes one or more brushes. In this embodiment, the brush seal 520 includes a plurality of brushes 524. Each brush 524 includes a plurality of filaments. The filaments may be formed of a conductive material, such as a metallic material. A wall 526 may be positioned, for example, in an axial direction A between adjacent brushes 524. Furthermore, each brush 524 extends, for example, in a radial direction R between a proximal end 528 and a distal end 530. The brushes 524 are attached to the housing 522 at their respective proximal ends 528. The brushes 524 engage with the low-speed shaft 246 at their respective distal ends 530. Notably, the low-speed shaft 246 may include a wear-resistant coating 249 along its outer circumference, such as… Figure 13 As shown. The wear-resistant coating 249 prevents damage to the low-speed shaft 246 due to the brush 524 engaging with it. In some embodiments, the brush 524 may be electrically connected to the grounding system 350 via a transmission line 352.

[0111] Therefore, when the low-speed shaft 246 and the rotor hub 318 are about the central longitudinal axis 214 ( Figure 2 When the brush 524 rotates and engages the low-speed shaft 246, an electrical grounding path is created between the brush 524 and the low-speed shaft 246. Therefore, current can flow between the low-speed shaft 246 and the brush 524. In this way, the low-speed shaft 246 and the rotor hub 318 can be electrically grounded. Therefore, in such an embodiment, the brush seal 520 has a dual function, as it is operable to provide a grounding connection point for electrically grounding the low-speed shaft 246 and the rotor hub 318 operably connected to it, and operable to seal the fluid within the chamber. Among other benefits, integrating the electrical grounding function into the brush seal 520 reduces the number of parts required to electrically ground the rotor hub 318 and the low-speed shaft 246, and can reduce the number of parts required for the first thruster 200A (…). Figure 1 The weight of the aircraft is reduced by 100 ( Figure 1 It weighs less and can make efficient use of space.

[0112] Figure 14A flowchart of a method (600) of operating a hybrid electric propulsor is provided in accordance with one example embodiment of the present disclosure. For example, the method (600) can be used to operate one or both of the propulsors 200A, 200B disclosed herein, or any other propulsor having a gas turbine engine equipped with an embedded electric machine operably coupled with a shaft of the engine. It should be appreciated that the method (600) is discussed herein to describe exemplary aspects of the subject matter and is not intended to be limiting.

[0113] At (602), the method (600) includes operating a propulsor having a gas turbine engine equipped with an electric machine operably coupled with a shaft of the gas turbine engine, the electric machine being electrically coupled with a power converter. For example, the propulsor can be the first propulsor 200A disclosed herein. The electric machine can be embedded within a core of the gas turbine engine, can be mechanically coupled with a shaft (e.g., a low speed shaft, a high speed shaft, or any other suitable shaft of the gas turbine engine). One or more bearings can support the shaft. During operation, the shaft rotates about its rotational axis, and when a rotor of the electric machine is operably coupled with the shaft, the rotor rotates in unison with the shaft. In some embodiments, the electric machine can operate in a drive or motor mode. In the drive mode, the power converter provides power to the electric machine, thereby causing the electric machine to drive the shaft. In some embodiments, the electric machine can operate in a generator mode. In the generator mode, the shaft drives the rotor, causing the electric machine to generate power. The generated power can then be provided to the power converter and ultimately to one or more electrical loads. When power is transferred between the power converter and the electric machine, a common mode voltage can drive a common mode current through the electric machine and through electrically conductive components associated with the electric machine.

[0114] At (602A), in some embodiments, while operating the propulsor at (602), the method (600) includes reducing the common mode voltage reaching the electric machine from the power converter via an electromagnetic interface filter of the power converter. For example, an EMI filter of the power converter associated with the propulsor can reduce the common mode voltage reaching the electric machine. Further, in some embodiments, one or more shielded cables or busbars can further reduce the common mode voltage reaching the electric machine.

[0115] At (602B), while operating the thruster at (602) in some embodiments, the method (600) includes interrupting, via an insulating joint operably coupling a rotor of the electric machine to a rotor connection assembly of the shaft, a common mode current driven by the power converter to the electric machine from the rotor to the shaft. For example, the insulating joint can be embodied in any of the configurations provided herein. As one example, the insulating joint can mechanically couple a rotor connection member connected to the rotor of the electric machine and a rotor hub connected to the shaft. The insulating joint can not only mechanically couple the rotor connection member and the rotor hub, but also electrically isolate the rotor and the shaft. In this regard, the insulating joint interrupts the common mode current from the rotor to the shaft. Advantageously, this prevents the common mode current from reaching one or more bearings supporting the shaft.

[0116] At (602C), while operating the thruster at (602) in some embodiments, the method (600) includes electrically grounding the shaft through a grounding device. For example, the grounding device can be embodied in any of the configurations provided herein. As one example, the grounding device can be as shown in the configuration. Figure 4 In particular, the grounding device can have a stationary component, a rotating component connected to the shaft or some other component that can rotate with the shaft, and one or more electrical contacts providing an electrical ground path between the rotating component and the stationary component. In some embodiments, the grounding device is integrated into a resolver operable to measure an angle of the shaft. In other embodiments, the grounding device is integrated into an encoder operable to measure a rotational speed of the shaft. In some further embodiments, the grounding device is integrated into a carbon seal. In some further embodiments, the grounding device is integrated into a brush seal.

[0117] Accordingly, during operation of the thruster at (602), the method (600) can collectively include reducing the common mode voltage reaching the electric machine at (602A), interrupting the common mode current reaching the shaft coupled to the electric machine at (602B), and electrically grounding the shaft coupled to the electric machine at (602C). In this way, a three-pronged solution to bearing current mitigation is achieved. Advantageously, this can enable specific fuel burn gains through power cycling between low speed and high speed spools without shortening the life of the spool bearings. Moreover, this can mitigate spool bearing currents without modifying such bearings and with only minimal modifications to the spool rotor structure.

[0118] Figure 15 An example computing system 700 according to example embodiments of the present disclosure is provided. For example, the computing systems and devices described herein can include various components and perform various functions of the computing system 700 described below.

[0119] As Figure 15As shown, computing system 700 can include one or more computing devices 710. Computing device 710 can include one or more processors 710A and one or more memory devices 710B. One or more processors 710A can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and / or other suitable processing device. One or more memory devices 710B can include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and / or other memory devices.

[0120] One or more memory devices 710B can store information accessible by one or more processors 710A, including computer-readable instructions 710C that can be executed by one or more processors 710A. Instructions 710C can be any set of instructions that when executed by one or more processors 710A, cause one or more processors 710A to perform operations. In some embodiments, instructions 710C can be executed by one or more processors 710A to cause one or more processors 710A to perform operations, such as any operations and functions of computing system 700 and / or computing device 710 for which one or more processors 710A are configured. Instructions 710C can be software written in any suitable programming language or can be implemented in hardware. Additionally, and / or alternatively, instructions 710C can be executed in logically and / or virtually separate threads on processor 710A. Memory devices 710B can further store data 710D that can be accessed by processors 710A. For example, data 710D can include models, databases, and the like.

[0121] Computing device 710 can also include network interface 710E for communicating with other components of system 700 (e.g., via a communication network). Network interface 710E can include any suitable components for interfacing with one or more networks, including for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components. One or more devices can be configured to receive one or more commands from computing device 710 or provide one or more commands to computing device 710.

[0122] The technology discussed herein makes reference to computer-based systems, actions taken by and information sent to and from computer-based systems. One of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for a great variety of possible configurations, combinations, and divisions of tasks and functionality between and among components. For instance, processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memories, programs, routines, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel.

[0123] While specific features of various embodiments can be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any of the features of a drawing can be referenced and / or claimed in combination with any of the features of any of the other drawings.

[0124] This written description uses examples to disclose the application, including the best mode, and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0125] Further aspects of the application are provided by the subject matter of the following clauses:

[0126] 1. A hybrid-electric propulsion system comprising: an electric power converter; and a propulsor comprising: a gas turbine engine having a shaft and one or more bearings supporting the shaft; and an electric machine electrically coupled with the electric power converter and comprising a stator assembly and a rotor assembly, the rotor assembly having a rotor and a rotor connection assembly operably coupling the rotor with the shaft, the rotor connection assembly having an insulated joint for interrupting flow of common mode current between the rotor and the shaft.

[0127] 2. The hybrid-electric propulsion system of any preceding clause, wherein the rotor connection assembly has a rotor hub connected to the shaft and a rotor connection member connected to the rotor, the rotor hub and the rotor connection member being mechanically coupled with one another by the insulated joint.

[0128] 3. The hybrid-electric propulsion system of any preceding clause, wherein the insulated joint comprises a hub flange of the rotor hub, a connection flange of the rotor connection member, a bolt extending through the hub flange and the connection flange, and one or more insulating members electrically isolating the rotor connection member from the rotor hub.

[0129] 4. The hybrid electric propulsion system of any preceding clause, wherein the one or more insulating members comprise: a hub washer positioned between the hub flange and one of a head and a nut of the bolt, the nut being fixed to the bolt opposite the head; a joint washer positioned between the hub flange and the connection flange such that the hub flange and the connection flange are not in physical contact with each other; and a connection flange positioned between the hub flange and one of the head and the nut of the bolt, the nut being fixed to the bolt opposite the head.

[0130] 5. The hybrid electric propulsion system of any preceding clause, wherein at least a portion of the bolt is coated with an insulating coating, the portion being in physical contact with at least one of the hub flange and the connection flange.

[0131] 6. The hybrid electric propulsion system of any preceding clause, wherein the power converter has an electromagnetic interference filter operable to reduce common mode voltage reaching the electric machine from the power converter.

[0132] 7. The hybrid electric propulsion system of any preceding clause, wherein the power converter is electrically coupled to the electric machine by one or more shielded cables.

[0133] 8. The hybrid electric propulsion system of any preceding clause, wherein the gas turbine engine further comprises a grounding device having a stationary component, a rotating component connected to the shaft, and one or more electrical contacts providing an electrical ground path between the rotating component and the stationary component, the stationary component being electrically coupled to a ground system.

[0134] 9. The hybrid electric propulsion system of any preceding clause, wherein the grounding device is integrated into a resolver operable to measure an angle of the shaft or an encoder operable to measure a rotational speed of the shaft.

[0135] 10. The hybrid electric propulsion system of any preceding clause, wherein the grounding device is integrated into a carbon seal or a brush seal.

[0136] 11. The hybrid electric propulsion system of any preceding clause, wherein the propulsor defines a radial direction, and wherein the rotor is positioned inside a stator of the stator assembly along the radial direction.

[0137] 12. The hybrid electric propulsion system of any preceding clause, wherein the propulsor defines a radial direction, and wherein the rotor is positioned outside a stator of the stator assembly along the radial direction.

[0138] 13. The hybrid-electric propulsion system of any preceding clause, wherein the gas turbine engine includes a low speed shaft and a high speed shaft, and wherein the shaft is the low speed shaft.

[0139] 14. The hybrid-electric propulsion system of any preceding clause, wherein the gas turbine engine includes a low speed shaft and a high speed shaft, and wherein the shaft is the high speed shaft.

[0140] 15. A method comprising: operating a propulsor having a gas turbine engine equipped with an electric machine operably coupled with a shaft of the gas turbine engine, the electric machine being electrically coupled with a power converter, and wherein operating the propulsor includes: i) reducing a common mode voltage reaching the electric machine from the power converter via an electromagnetic interface filter of the power converter; ii) interrupting a flow of a common mode current driven by the power converter to the electric machine between a rotor of the electric machine and the shaft via an insulating joint of a rotor connection assembly operably coupling the rotor with the shaft; and iii) electrically grounding the shaft by a grounding device.

[0141] 16. A propulsor comprising: a gas turbine engine having a shaft; and an electric machine having a stator assembly and a rotor assembly, the rotor assembly having a rotor and a rotor connection assembly having a rotor connection member connected to the rotor and a rotor hub connected to the shaft, the rotor connection member and the rotor being mechanically coupled and electrically isolated by an insulating joint; and a grounding device operable to electrically ground the shaft.

[0142] 17. The propulsor of any preceding clause, wherein the grounding device has a stationary component, a rotating component connected to the shaft, and one or more electrical contacts providing an electrical ground path between the rotating component and the stationary component.

[0143] 18. The propulsor of any preceding clause, wherein the grounding device is integrated into a resolver operable to measure an angle of the shaft or an encoder operable to measure a rotational speed of the shaft.

[0144] 19. The propulsor of any preceding clause, wherein the grounding device is integrated into at least one of a carbon seal and a brush seal.

[0145] 20. The propeller of any preceding clause, wherein the rotor connection assembly has a rotor hub connected to the shaft and a rotor connection member connected to the rotor, the rotor hub and the rotor connection member are mechanically coupled to each other by the insulated joint, and wherein the insulated joint comprises a hub flange of the rotor hub, a connection flange of the rotor connection member, a bolt extending through the hub flange and the connection flange, and wherein at least one of the hub flange and the connection flange has one or more insulating layers.

Claims

1. A hybrid electric propulsion system, characterized by Comprising: a power converter; and a propulsor, the propulsor comprising: a gas turbine engine having a shaft and one or more bearings supporting the shaft; and an electric machine electrically coupled with the power converter and comprising a stator assembly and a rotor assembly, the rotor assembly having a rotor and a rotor connection assembly operably coupling the rotor with the shaft, the rotor connection assembly having an insulated joint for interrupting flow of common mode current between the rotor and the shaft; wherein the rotor connection assembly has a rotor hub connected to the shaft and a rotor connection member connected to the rotor, the rotor hub and the rotor connection member being mechanically coupled with each other through the insulated joint, wherein the insulated joint comprises a hub flange of the rotor hub, a connection flange of the rotor connection member, a bolt extending through the hub flange and the connection flange, and one or more insulating members electrically isolating the rotor connection member from the rotor hub.

2. The hybrid electric propulsion system of claim 1, wherein, wherein the one or more insulating members comprise: a hub spacer positioned between the hub flange and one of a head and a nut of the bolt, the nut being fixed to the bolt opposite the head; an interface spacer positioned between the hub flange and the connection flange such that the hub flange and the connection flange are not in physical contact with each other; and a connection flange positioned between the hub flange and one of the head and the nut of the bolt, the nut being fixed to the bolt opposite the head.

3. The hybrid electric propulsion system of claim 2, wherein, wherein at least a portion of the bolt is coated with an insulating coating, the portion being in physical contact with at least one of the hub flange and the connection flange.

4. The hybrid electric propulsion system of claim 1, wherein, wherein the power converter has an electromagnetic interference filter operable to reduce common mode voltage reaching the electric machine from the power converter.

5. The hybrid electric propulsion system of claim 1, wherein, wherein the power converter is electrically coupled with the electric machine by one or more shielded cables.

6. The hybrid electric propulsion system of claim 1, wherein, wherein the gas turbine engine further comprises a grounding device having a stationary component, a rotating component connected to the shaft, and one or more electrical contacts providing an electrical ground path between the rotating component and the stationary component, the stationary component being electrically coupled with a ground system.

7. The hybrid electric propulsion system of claim 6, wherein, wherein the grounding device is integrated into a resolver operable to measure an angle of the shaft or an encoder operable to measure a rotational speed of the shaft.

8. The hybrid electric propulsion system of claim 6, wherein, wherein the grounding device is integrated into a carbon seal or a brush seal.

9. The hybrid electric propulsion system of claim 1, wherein, wherein the propulsor defines a radial direction, and wherein the rotor is positioned inside a stator of the stator assembly along the radial direction.

10. The hybrid electric propulsion system of claim 1, wherein, wherein the propulsor defines a radial direction, and wherein the rotor is positioned outside a stator of the stator assembly along the radial direction.

11. The hybrid electric propulsion system of claim 1, wherein, wherein the gas turbine engine comprises a low speed shaft and a high speed shaft, and wherein the shaft is the low speed shaft.

12. The hybrid electric propulsion system of claim 1, wherein, wherein the gas turbine engine comprises a low speed shaft and a high speed shaft, and wherein the shaft is the high speed shaft.

13. A method characterized by, Comprising: Operating a propulsor having a gas turbine engine equipped with an electric machine operably coupled with a shaft of the gas turbine engine, the electric machine being electrically coupled with a power converter, and wherein operating the propulsor includes: i) reducing a common mode voltage from the power converter to the electric machine via an electromagnetic interface filter of the power converter; ii) interrupting a flow of a common mode current driven by the power converter to the electric machine between a rotor of the electric machine and the shaft via an insulating joint of a rotor connection assembly operably coupling the rotor with the shaft; and iii) electrically grounding the shaft by a grounding device; wherein the rotor connection assembly has a rotor hub connected to the shaft and a rotor connection member connected to the rotor, the rotor hub and the rotor connection member being mechanically coupled to each other by the insulating joint, and wherein the insulating joint includes a hub flange of the rotor hub, a connection flange of the rotor connection member, a bolt extending through the hub flange and the connection flange, and wherein at least one of the hub flange and the connection flange has one or more insulating layers.

14. A propeller characterized by including: a gas turbine engine having a shaft; and an electric machine having a stator assembly and a rotor assembly, the rotor assembly having a rotor and a rotor connection assembly, the rotor connection assembly having a rotor connection member connected to the rotor and a rotor hub connected to the shaft, the rotor connection member and the rotor being mechanically coupled and electrically isolated by an insulating joint; and a grounding device operable to electrically ground the shaft; wherein the rotor connection assembly has a rotor hub connected to the shaft and a rotor connection member connected to the rotor, the rotor hub and the rotor connection member being mechanically coupled to each other by the insulating joint, and wherein the insulating joint includes a hub flange of the rotor hub, a connection flange of the rotor connection member, a bolt extending through the hub flange and the connection flange, and wherein at least one of the hub flange and the connection flange has one or more insulating layers.

15. The propulsor of claim 14, wherein, wherein the grounding device has a stationary component, a rotating component connected to the shaft, and one or more electrical contacts providing an electrical ground path between the rotating component and the stationary component.

16. The propulsor of claim 14, wherein, wherein the grounding device is integrated into a resolver operable to measure an angle of the shaft or an encoder operable to measure a rotational speed of the shaft.

17. The propulsor of claim 14, wherein, wherein the grounding device is integrated into at least one of a carbon seal and a brush seal.

Images