Gas turbine engine having a clutch assembly

Abstract

The present invention relates to a gas turbine engine having a clutch assembly. Specifically, a gas turbine engine is provided. The gas turbine engine includes: a turbine including a low-speed shaft; a rotor assembly coupled to the low-speed shaft; an electric machine mechanically coupled to the low-speed shaft at a connection point; and a clutch positioned in the torque path of the low-speed shaft between the connection point and the rotor assembly.

Description

[0001] Cross - reference to related applications

[0002] This application is a non - provisional application that claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62 / 915,364, filed on October 15, 2019, which is hereby incorporated by reference in its entirety. Technical field

[0003] The present application is generally directed to a gas turbine engine having an accessory gearbox, an electric machine, or both, configured to improve the responsiveness of the gas turbine engine. Background art

[0004] A turbine engine typically includes a turbine and a rotor assembly. In the case of a turbofan engine, the rotor assembly may be configured as a fan assembly. The turbine typically includes a high - pressure spool and a low - speed spool. A combustion section receives pressurized air that is mixed with fuel and burned in a combustion chamber to generate combustion gases. The combustion gases are first provided to a high - pressure turbine of the high - pressure spool to drive the high - pressure spool and then to a low - speed turbine of the low - speed spool to drive the low - speed spool. The rotor assembly is typically coupled to the low - speed spool.

[0005] Some gas turbine engines also include an accessory gearbox for powering various accessory systems of the gas turbine engine. The accessory gear is coupled to the high - pressure spool. However, as will be appreciated, extracting power from the high - pressure spool can result in a weaker response of the high - pressure spool to engine commands, which in turn can result in a weaker response of the low - speed spool and the rotor assembly to engine commands.

[0006] Accordingly, a gas turbine engine having one or more features (or structural elements) for improving the responsiveness of the gas turbine engine to engine commands would be useful. Summary of the invention

[0007] Aspects and advantages of the present invention will be set forth in part in the following description, or may be apparent from the description, or may be learned by practice of the invention.

[0008] In one aspect of the present disclosure, a gas turbine engine is provided. The gas turbine engine includes: a turbine including a low - speed spool; a rotor assembly coupled to the low - speed spool; an electric machine mechanically coupled to the low - speed spool at a connection point; and a clutch positioned in the torque path of the low - speed spool between the connection point and the rotor assembly.

[0009] Specifically, the present disclosure also provides the following technical solutions.

[0010] Technical Solution 1. A gas turbine engine, comprising:

[0011] A turbine including a low-speed shaft;

[0012] A rotor assembly coupled to the low-speed shaft;

[0013] An electric motor mechanically coupled to the low-speed shaft at a connection point of the low-speed shaft; and

[0014] A clutch positioned in a torque path of the low-speed shaft between the connection point and the rotor assembly.

[0015] Technical Solution 2. The gas turbine engine according to Technical Solution 1, wherein the clutch is a two-stage clutch.

[0016] Technical Solution 3. The gas turbine engine according to Technical Solution 1, wherein the clutch is movable between an engaged position and a disengaged position, wherein in the engaged position the rotor assembly can rotate with the low-speed shaft, and in the disengaged position the rotor assembly can be rotationally disengaged from the low-speed shaft.

[0017] Technical Solution 4. The gas turbine engine according to Technical Solution 3, wherein the clutch includes a first part and a second part, wherein the clutch can also be moved to a transitional position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transitional position.

[0018] Technical Solution 5. The gas turbine engine according to Technical Solution 3, wherein the clutch includes a first part and a second part, wherein the first part includes a first geometric feature, wherein the second part includes a second geometric feature complementary in shape to the first geometric feature, and wherein the first geometric feature engages with the second geometric feature when the clutch is in the engaged position.

[0019] Technical Solution 6. The gas turbine engine according to Technical Solution 5, wherein the clutch can also be moved to a transitional position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transitional position, and wherein the first geometric feature and the second geometric feature are separated when the clutch is in the transitional position.

[0020] Technical solution 7. The gas turbine engine according to technical solution 1, characterized in that the gas turbine engine further comprises:

[0021] An accessory gearbox, the accessory gearbox being coupled to the low-speed shaft at the connection point, and wherein the electric machine is coupled to the low-speed shaft via the accessory gearbox.

[0022] Technical solution 8. The gas turbine engine according to technical solution 1, characterized in that the gas turbine engine is configured as a single non-ducted rotor engine, and wherein the rotor assembly comprises a single non-ducted rotor blade stage.

[0023] Technical solution 9. The gas turbine engine according to technical solution 8, characterized in that the gas turbine engine further comprises:

[0024] A non-ducted guide vane stage positioned downstream of the single non-ducted rotor blade stage.

[0025] Technical solution 10. The gas turbine engine according to technical solution 1, characterized in that the turbine further comprises a core having a high-speed shaft.

[0026] Technical solution 11. A method of operating a gas turbine engine, the gas turbine engine comprising a low-speed shaft, a rotor assembly coupled to the low-speed shaft, and an electric machine coupled to the low-speed shaft at a connection point thereof, the method comprising:

[0027] Moving a clutch positioned within the torque path of the low-speed shaft between the connection point and the rotor assembly to a disengaged position such that the low-speed shaft rotates independently of the rotor assembly; and

[0028] Moving the clutch to an engaged position such that the low-speed shaft rotates with the rotor assembly.

[0029] Technical solution 12. The method according to technical solution 11, characterized in that moving the clutch to the disengaged position comprises: operating the gas turbine engine to generate electricity using an electric machine driven by the accessory gearbox without rotating the rotor assembly of the gas turbine engine.

[0030] Technical solution 13. The method according to technical solution 12, characterized in that the method further comprises:

[0031] Move the clutch from the disengaged position to a transition position until the rotor assembly rotates at substantially the same speed as the low-speed shaft axis, and wherein moving the clutch to the engaged position such that the low-speed shaft axis rotates with the rotor assembly includes: moving the clutch to the engaged position after moving the clutch from the disengaged position to the transition position until the rotor assembly rotates at substantially the same speed as the low-speed shaft axis.

[0032] Technical solution 14. The method according to technical solution 12, characterized in that the method further comprises:

[0033] Operating the gas turbine engine at a speed equal to at least about 60% of the rated speed when the clutch is in the disengaged position;

[0034] While operating the gas turbine engine at a speed equal to at least about 60% of the rated speed when the clutch is in the disengaged position, converting rotational energy from the low-speed shaft axis into electrical power using the generator.

[0035] Technical solution 15. A gas turbine engine, comprising:

[0036] A turbine including a low-speed shaft axis;

[0037] A rotor assembly coupled to the low-speed shaft axis;

[0038] An accessory gearbox mechanically coupled to the low-speed shaft axis at a connection point of the low-speed shaft axis; and

[0039] A clutch, the clutch being positioned in the torque path of the low-speed shaft axis between the connection point and the rotor assembly.

[0040] Technical solution 16. The gas turbine engine according to technical solution 15, characterized in that the clutch is a two-stage clutch.

[0041] Technical solution 17. The gas turbine engine according to technical solution 15, characterized in that the clutch is movable between an engaged position and a disengaged position, wherein in the engaged position the rotor assembly can rotate with the low-speed shaft axis, and in the disengaged position the rotor assembly can be rotationally disengaged from the low-speed shaft axis.

[0042] Technical solution 18. The gas turbine engine according to technical solution 17, wherein the clutch comprises a first part and a second part, wherein the clutch is further movable to a transition position, wherein the first part comprises a first friction plate, wherein the second part comprises a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position.

[0043] Technical solution 19. The gas turbine engine according to technical solution 15, wherein the gas turbine engine further comprises:

[0044] An electric motor, the electric motor being coupled to the low-speed shaft at the connection point, and wherein the electric motor is coupled to the low-speed shaft via the accessory gearbox.

[0045] Technical solution 20. The gas turbine engine according to technical solution 15, wherein the gas turbine engine is configured as a single unducted rotor engine, wherein the rotor assembly comprises a single stage of unducted rotor blades, and wherein the gas turbine engine further comprises:

[0046] An unducted guide vane stage positioned downstream of the single stage of unducted rotor blades.

[0047] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention, which is a complete and enabling disclosure for the ordinary skilled person in the art (including its best mode), is set forth in the specification with reference to the accompanying drawings, in which:

[0049] Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary aspect of the present disclosure.

[0050] Figure 2 is another schematic cross-sectional view of a gas turbine engine according to another exemplary aspect of the present disclosure.

[0051] Figure 3 is a schematic view of a clutch in a first position according to an exemplary embodiment of the present disclosure.

[0052] Figure 4 is Figure 3 a schematic view of an exemplary clutch in a second position.

[0053] Figure 5Yes Figure 3 Schematic view of an exemplary clutch in the third position.

[0054] Figure 6 Another schematic cross-sectional view of a gas turbine engine according to another exemplary aspect of the present disclosure.

[0055] Figure 7 Flowchart of a method of operating a gas turbine engine according to an exemplary aspect of the present disclosure. Detailed Description

[0056] Reference will now be made in detail to the current embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and alphabetical labels to refer to features in the drawings. The same or similar labels in the drawings and the description are used to refer to the same or similar parts of the present invention.

[0057] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any specific embodiment described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other specific embodiments.

[0058] As used herein, the terms "first", "second", and "third" may be used interchangeably to distinguish one component from another and are not intended to denote the position or importance of individual components.

[0059] The terms "front" and "rear" 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, "front" refers to a position closer to the engine inlet, while "rear" refers to a position closer to the engine nozzle or exhaust port (or exhaust device).

[0060] The terms "upstream" and "downstream" refer to the relative direction of fluid flow in a fluid passage. For example, "upstream" refers to the direction from which the fluid flows, while "downstream" refers to the direction towards which the fluid flows.

[0061] Unless otherwise specified herein, the terms "coupled", "fixed", "attached to", etc. refer to direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment via one or more intermediate components or features.

[0062] The singular forms "a", "an", and "the" include plural meanings, unless clearly specified otherwise in the context.

[0063] As used throughout the specification and claims, approximating language may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, values modified by terms or terms such as "about," "approximately," and "substantially" are not to be limited to the exact values enumerated. In at least some instances, approximating language may correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to fabricate or construct the component and / or system. For example, approximating language may refer to within a margin of 1%, 2%, 4%, 10%, 15%, or 20%.

[0064] Herein and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include the subranges contained therein, unless the context or language indicates otherwise. For example, all ranges disclosed herein include the endpoints, and the endpoints may be combined independently of each other.

[0065] Now referring to the drawings, Figure 1 there is shown a front cross-sectional view of an exemplary embodiment of a gas turbine engine that may incorporate one or more inventive aspects of the present disclosure. Specifically, Figure 1 the exemplary gas turbine engine is configured as a single non-ducted rotor engine 10 that defines an axial direction A, a radial direction R, and a circumferential direction C (not shown, extending about the axial direction A). As seen from Figure 1 the engine 10 takes the form of an open rotor propulsion system and includes a rotor assembly 12 that comprises an array of airfoils disposed about a central longitudinal axis 14 of the engine 10, and more particularly, an array of rotor blades 16 disposed about the central longitudinal axis 14 of the engine 10. Additionally, as will be explained in more detail below, the engine 10 further includes a non-rotating vane assembly 18 (i.e., not rotating relative to the central axis 14) positioned rearward of the rotor assembly 12, the non-rotating vane assembly including: an array of airfoils also disposed about the central axis 14, and more particularly, an array of vanes 20 disposed about the central axis 14. The rotor blades 16 are typically arranged in equally spaced relationship about the centerline 14, and each blade has a root 22 and a tip 24 and a span defined therebetween. Similarly, the vanes 20 are also typically arranged in equally spaced relationship about the centerline 14, and each has a root 26 and a tip 28 and a span defined therebetween. The rotor assembly 12 further includes a hub 43 located forward of the plurality of rotor blades 16.

[0066] Additionally, engine 10 includes a turbine 30 having a core (or high-speed system) 32 and a low-speed system. Core 32 generally includes a high-speed compressor 34, a high-speed turbine 36, and a high-speed shaft 38 extending therebetween and connecting high-speed compressor 34 and high-speed turbine 36. High-speed compressor 34 (or at least its rotating member), high-speed turbine 36 (or at least its rotating member), and high-speed shaft 38 may be collectively referred to as the high-speed spool 35 of the engine. Additionally, a combustion section 40 is located between high-speed compressor 34 and high-speed turbine 36. Combustion section 40 may include one or more configurations for receiving a mixture of fuel and air and providing a flow of combustion gases through high-speed turbine 36 to drive high-speed spool 35.

[0067] The low-speed system similarly includes a low-speed turbine 42, a low-speed compressor or supercharger 44, and a low-speed shaft 46 extending between and connecting low-speed compressor 44 and low-speed turbine 42. Low-speed compressor 44 (or at least its rotating member), low-speed turbine 42 (or at least its rotating member), and low-speed shaft 46 may be collectively referred to as the low-speed spool 45 of the engine.

[0068] Although engine 10 is depicted as having low-speed compressor 44 positioned in front of high-speed compressor 34, in some embodiments, compressors 34, 44 may be arranged in an interdigitated fashion. Additionally or alternatively, although engine 10 is depicted as having high-speed turbine 36 positioned in front of low-speed turbine 42, in some embodiments, turbines 36, 42 may similarly be arranged in an interdigitated fashion.

[0069] Still referring to Figure 1 , turbine 30 is generally enclosed in a cowl 48. Additionally, it will be appreciated that cowl 48 at least partially defines an inlet 50 and an exhaust port 52 and includes a turbomachinery flow path 54 extending between inlet 50 and exhaust port 52. For the illustrated embodiment, inlet 50 is an annular or axially symmetric 360-degree inlet 50 located between rotor blade assembly 12 and a fixed or stationary vane assembly and provides a path for introduced ambient air to enter turbomachinery flow path 54 (and compressors 44, 34, combustion section 40, and turbines 36, 42) along a radial direction R inside guide vanes 20. This location may be advantageous for a variety of reasons, including managing icing performance and protecting inlet 50 from various objects and materials that may be encountered during operation.

[0070] However, in other embodiments, inlet 50 may be located at any other suitable location, e.g., behind vane assembly 18, arranged in a non-axially symmetric manner, etc.

[0071] As briefly mentioned above, the engine 10 includes a vane assembly 18. The vane assembly 18 extends from the shroud 48 and is positioned rearward of the rotor assembly 12. The vanes 20 of the vane assembly 18 may be mounted to a stationary frame or other mounting structure and do not rotate relative to the central axis 14. For reference purposes, Figure 1 the forward direction is also depicted by an arrow F, which in turn defines the front and rear of the system. As shown in Figure 1 , the rotor assembly 12 is positioned in front of the turbine 30 in a "puller" configuration, and the exhaust port 52 is located rearward of the guide vanes 20. As will be appreciated, the vanes 20 of the vane assembly 18 may be configured to straighten the air flow from the rotor assembly 12 (e.g., reduce swirl in the air flow) to improve the efficiency of the engine 10. For example, the vanes 20 may be sized, shaped, and configured to apply counteracting swirl to the air flow from the rotor blades 16 such that the air flow has a greatly reduced degree of swirl in the downstream direction behind the two rows of airfoils (e.g., blades 16, vanes 20), which can translate into an improved level of induced efficiency.

[0072] Still referring to Figure 1 , it may be desirable for the rotor blades 16, the vanes 20, or both to incorporate pitch change mechanisms such that the airfoils (e.g., blades 16, vanes 20, etc.) can rotate independently or in combination with each other relative to a pitch axis of rotation. Such pitch changes can be used to vary the thrust and / or swirl effects under various operating conditions, including to adjust the magnitude or direction of the thrust generated at the rotor blades 16, or to provide a thrust reversal feature that may be useful under certain operating conditions, such as during aircraft landing, or to desirably adjust the acoustic noise generated at least in part by the rotor blades 16, the vanes 20, or the aerodynamic interaction of the air flow from the rotor blades 16 relative to the vanes 20. More specifically, for the Figure 1 embodiment, the rotor assembly 12 is depicted as having a pitch change mechanism 58 for rotating the rotor blades 16 about their respective pitch axes 60, and the vane assembly 18 is depicted as having a pitch change mechanism 62 for rotating the vanes 20 about their respective pitch axes 64.

[0073] As depicted, the rotor assembly 12 is driven by the turbine 30, and more specifically, by the low-speed shaft 45. More specifically, in Figure 1In the illustrated embodiment, the engine 10 includes a power gearbox 56, and the rotor assembly 12 is driven across the power gearbox 56 by the low-speed shaft 45 of the turbine 30. The power gearbox 56 may include a gear set for reducing the rotational speed of the low-speed shaft 45 relative to the low-speed turbine 42 such that the rotor assembly 12 can rotate at a slower rotational speed compared to the low-speed shaft 45. In this way, the rotating rotor blades 16 of the rotor assembly 12 can rotate about the axis 14 and generate thrust to propel the engine 10 in the forward direction F and thus propel the associated aircraft.

[0074] Still referring to Figure 1 , the exemplary engine 10 includes an accessory gearbox 66 and an electric machine 68, wherein the turbine 30 drives the accessory gearbox 66 and the electric machine 68. For example, in some exemplary embodiments, the accessory gearbox 66 may be coupled to the low-speed shaft 45 (e.g., the low-speed shaft 46) via a suitable gear train, while the electric machine 68 may be coupled to the accessory gearbox 66. However, in other exemplary embodiments, the electric machine 68 may be coupled to the low-speed shaft 45 of the turbine 30 independently of the accessory gearbox 66, and the accessory gearbox 66 may be coupled to the low-speed shaft 45 or the high-speed shaft 35.

[0075] However, it will be appreciated that the exemplary single-rotor ducted fan engine 10 depicted in Figure 1 is merely illustrative, and in other exemplary embodiments, the engine 10 may have any other suitable configuration, including, for example, any other suitable number of shafts or shafts, turbines, compressors, etc. Additionally or alternatively, in other exemplary embodiments, any other suitable gas turbine engine may be provided. For example, in other exemplary embodiments, the gas turbine engine may be a ducted turbofan engine, a turboshaft engine, a turboprop engine, a turbojet engine, etc.

[0076] Now referring to Figure 2 , a schematic view of a gas turbine engine 10 according to an exemplary embodiment of the present disclosure is depicted. Figure 2 The exemplary gas turbine engine 10 of Figure 1 may be constructed in a manner similar to the exemplary engine 10 described above with respect to

[0077] In this way, the accessory gearbox 66 can transfer the rotational power from the low-speed shaft 45 of the engine 10 to one or more accessory systems 70 and the electric machine 68 (which can rotate with the accessory gearbox 66) that are mechanically coupled to the accessory gearbox 66, such as the engine 10 or an aircraft incorporating the engine 10. The engine 10 also includes a rotor assembly 12 and a power gearbox 56, wherein the rotor assembly 12 is driven by the low-speed shaft 45 across the power gearbox 56.

[0078] As will be appreciated, the various electrical and other accessory systems of the gas turbine engine 10 are typically shut down by an accessory gearbox that is driven by the core 32 of the engine 10 or more specifically by the high-speed / high-pressure system of the engine 10. For such a configuration, the engine core 32 is typically sized up to allow these accessory systems to operate throughout the flight envelope. However, it is noted that such a configuration can reduce the responsiveness of the engine 10 due to the additional load and inertia on the core 32 of the engine 10. It will be appreciated that by coupling the accessory gearbox 66 and the electric machine 68 to the low-speed shaft 45 of the engine 10 rather than the high-speed shaft 35, the gas turbine engine 10 can have a more responsive core 32. Moreover, although this may in turn result in a less responsive low-speed system and rotor assembly 12, the inclusion of the electric machine 68 can compensate for the responsiveness, as discussed below.

[0079] Still referring to Figure 2 , it will be appreciated that the electric machine 68 is coupled to the low-speed shaft 45 of the turbine 30 at the connection point 100 of the low-speed shaft 45. More specifically, for the illustrated embodiment, the accessory gearbox 66 is coupled to the low-speed shaft 45 at the connection point 100, and the electric machine 68 is coupled to the low-speed shaft 45 via the accessory gearbox 66. Moreover, for the illustrated embodiment, the turbine 30 includes a gear train 102 that is coupled to the low-speed shaft 45 at the connection point 100 and extends to the accessory gearbox 66. In this way, the accessory gearbox 66 can transfer the rotational power from the low-speed shaft 45 of the engine 10 to one or more accessory systems 70 that are mechanically coupled to the accessory gearbox 66 and the electric machine 68 that can rotate with the accessory gearbox 66.

[0080] Additionally, as depicted in Figure 2 , the exemplary gas turbine engine 10 includes an engine clutch 104 that is positioned in the torque path of the low-speed shaft 45 at a location ahead of the connection point 100 of the low-speed shaft 45 (wherein the accessory gearbox 66 is coupled to the low-speed shaft 45 via the gear train 102). Specifically, for the illustrated embodiment, the engine clutch 104 is positioned in the torque path of the low-speed shaft 45 between the connection point 100 and the rotor assembly 12.

[0081] The engine clutch 104 is movable between an engaged position and a disengaged position, wherein in the engaged position, torque can be transmitted across the engine clutch 104 along the low-speed tube axis 45 to drive the rotor assembly 12 (or vice versa), and in the disengaged position, torque is not transmitted across the engine clutch 104 along the low-speed tube axis 45 to the rotor assembly 12. In this way, the engine clutch 104 can facilitate the operation of the engine 10 without rotating the rotor assembly 12. This can be beneficial, particularly during certain ground operations where it may be desirable to rotate the turbine 30 without generating thrust from the rotor assembly 12.

[0082] In at least some exemplary aspects, the engine clutch 104 can be a two-stage clutch for transitioning from the disengaged position to the engaged position. For example, now referring to Figure 3 and Figure 4 , depicted is a sample exemplary embodiment of the engine clutch 104 in accordance with an exemplary embodiment of the present disclosure. For the illustrated embodiment, the engine clutch 104 includes a first portion 108 and a second portion 110 that are movable relative to each other along a longitudinal direction L. In certain exemplary embodiments, the longitudinal direction L can be aligned with the axial direction A of the engine 10. Additionally, in certain exemplary embodiments, the first portion 108 can rotate with the rotor assembly 12, while the second portion 110 can rotate with the low-speed tube axis 45 at and behind the connection point 100.

[0083] As shown in Figure 3 and Figure 4 , the first portion 108 of the engine clutch 104 includes a first friction plate 112 and a first set of geometric features 114 (depicted in dashed lines and located in the inner surface of the first portion 108). The second portion 110 of the engine clutch 104 includes a second friction plate 116 and a second set of geometric features 118, the second set of geometric features 118 being correspondingly shaped relative to the first set of geometric features 114. More specifically, for the illustrated embodiment, the first set of geometric features 114 includes a plurality of protrusions extending along the longitudinal direction L, while the second set of geometric features 118 includes a plurality of grooves extending along the longitudinal direction L. The plurality of protrusions are configured to be slidably received within the plurality of grooves. In this way, the first and second sets of geometric features 114, 118 can be referred to as a spline connection.

[0084] As will be appreciated, when the engine clutch 104 is in the disengaged position ( Figure 3 ), the low-speed tube axis 45 can rotate freely relative to the rotor assembly 12. Conversely, when the engine clutch 104 is in the engaged position ( Figure 4), the low-speed shaft 45 rotates with the rotor assembly 12. The friction plates 112, 116 provide a relatively smooth transition from the disengaged position to the engaged position.

[0085] More specifically, now also referring to Figure 5 , it will be appreciated that the clutch 104 can also be moved to a transition position. In the transition position, the first and second friction plates 112, 116 are in contact with each other, but the first and second sets of geometric features 114, 118 are not in contact. This allows the rotor assembly 12 to accelerate slowly before engaging the first and second geometric features 114, 118 and locking the first and second parts 108, 110 of the clutch 104 together.

[0086] It is noted that, as will be further appreciated for the depicted embodiment, the second friction plate 116 is configured to slide along the longitudinal direction between the transition position and the engaged position. The second friction plate 116 can be biased along the longitudinal direction towards the first friction plate 112 by, for example, one or more spring assemblies (not shown).

[0087] In addition, after the rotor assembly 12 substantially matches the rotational speed of the low-speed shaft 45, the clutch 104 can be moved along the longitudinal direction L from the transition position to the engaged position such that the second geometric feature 118 engages the first geometric feature 114 to fix the first and second parts 108, 110 of the engine clutch 104 together.

[0088] It will also be appreciated that such a configuration can allow for improved operation of the gas turbine engine 10. For example, such a configuration can allow the core 32 of the gas turbine engine 10 to operate during, for example, idle and post-landing operations without participating in rotating the rotor assembly 12. In this way, the electric machine 68 can be sized to accept 100% of the rated engine power such that the gas turbine engine 10 can operate at rated engine power without engaging the rotor assembly 12 (i.e., by moving the engine clutch 104 to the disengaged position) and the electric machine 68 can substantially convert all such power into electrical energy to be provided via the electrical bus 120 (see Figure 2 ) to the aircraft 248 incorporating the gas turbine engine 10, to one or more energy storage units within or in electrical communication with the bus 230 to assist in starting additional engines, their combinations, etc.

[0089] Subsequently, when it is desired to utilize the rotor assembly 12 to generate thrust, the engine clutch 104 can be moved from the disengaged position to the transition position, thus allowing the rotor assembly 12 to accelerate slowly before moving the engine clutch 104 to the engaged position and rotationally locking the rotor assembly 12 to the low-speed shaft 45.

[0090] It will also be appreciated that for the above configuration, once the engine clutch 104 is moved to the engaged position, the electric motor 68 can be used to more quickly accelerate the rotor assembly 12 during pre-flight operation. More specifically, electrical power (or electric power) can be provided to the electric motor 68 and converted into rotational power, which is provided via the accessory gearbox 66 to the low-speed shaft 45 to directly assist in accelerating the rotor assembly 12. This can still ensure that the low-speed shaft 45 has the desired responsiveness even though the accessory gearbox 66 is mounted to the low-speed shaft 45.

[0091] As will also be appreciated, in this way, the electric motor 68 can be used to start or assist in starting the engine 10. Briefly referring back to Figure 2 , it will be recognized that the depicted exemplary engine 10 also includes an intershaft clutch 122 positioned between the low-speed / low-pressure system and the high-speed / high-pressure system of the gas turbine engine 10. In particular for the illustrated embodiment, the intershaft clutch 122 is positioned between the low-speed shaft 45 and the high-speed shaft 35. The intershaft clutch 122 can ensure that the low-speed / low-pressure system does not rotate faster than the high-speed / high-pressure system. The intershaft clutch 122 can be, for example, a one-way clutch, such as a wedge clutch. In this way, the electric motor 68 can operate as a starting motor for the gas turbine engine 10. For example, during a starting operation, the electric motor 68 can receive electrical power via the power bus 230 and convert such electrical power into mechanical power, which is transmitted via the accessory gearbox 66 and the gear train 102 to the low-speed shaft 45, thereby rotating the low-speed shaft 45. The intershaft clutch 122 can be engaged by such rotation, such that the low-speed shaft 45 correspondingly causes the high-speed shaft 35 to rotate across the intershaft clutch 122. Once the gas turbine engine 10 has reached the ignition point such that the combustion section can be ignited to start generating combustion gases to drive the high-speed system, the high-speed shaft 35 can rotate faster than the low-speed shaft 45, and the intershaft clutch 122 can automatically disengage, thereby allowing such a speed difference.

[0092] In this way, even though coupled to the low-speed shaft 45, the electric motor 68 can assist in starting the engine 10 by directly rotating the high-speed shaft 35.

[0093] Still referring to Figure 2 the embodiment of, once an aircraft including the gas turbine engine 10 has landed, the engine clutch 104 can be disengaged (i.e., moved to the disengaged position) such that the rotor assembly 12 can be immediately shut down after thrust from such an engine 10 is no longer required. Thus, this allows additional time for the gas turbine engine 10 to cool, allows the gas turbine engine 10 to provide full electrical power on the ground without operating the rotor assembly 12 (and without generating significant thrust), and electric ground taxiing etc. can be achieved.

[0094] However, it will be recognized that in other exemplary embodiments, the engine 10 may have any other suitable configuration. For example, now briefly referring to Figure 6 and depicted is an engine 10 according to another exemplary embodiment of the present disclosure. Figure 6 The exemplary engine 10 of Figure 2 may be constructed in substantially the same manner as the exemplary engine 10 of Figure 6 The exemplary engine 10 of

[0095] Figure 6 The exemplary engine 10 of Figure 6 also includes an accessory gearbox 66 coupled to the low speed shaft 45 and an electric machine 68 coupled to the low speed shaft 45. However, for the Figure 6 embodiment, the electric machine 68 is not coupled to the low speed shaft 45 via the accessory gearbox 66. Instead, for the

[0096] embodiment, the electric machine 68 is coupled to the low speed shaft 45 at an electric machine connection point 100A independent of the accessory gearbox 66. The accessory gearbox 66 is coupled to the low speed shaft 45 at a low speed shaft connection point 100B. Specifically, the electric machine 68 is via an electric machine gear train 102A and the accessory gearbox 66 is via an accessory gearbox gear train 100B. The electric machine connection point 100A is spaced from the accessory gearbox connection point 100B along the axial direction A of the engine 10. Figure 6 It should be noted that the exemplary engine 10 of Figures 2 to 5 also includes an engine clutch 104, which may be constructed in substantially the same manner as the exemplary engine clutch 104 described above with respect to

[0097] Although the electric machine 68 is spaced from the low speed shaft 45 for the embodiment depicted in the figures, it will be recognized that in other exemplary embodiments, the electric machine 68 may alternatively be mounted around the low speed shaft 45 such that it shares a rotational axis with the low speed shaft 45. For such a configuration, the rotor of the electric machine 68 may be mounted around the low pressure shaft 46 of the low speed shaft 45.

[0098] Other configurations are also contemplated.

[0099] Now briefly referring to Figure 7 a method 200 of operating a gas turbine engine is provided. Figure 7The gas turbine engine can be constructed according to Figures 1 to 6 One or more of the exemplary gas turbine engines. Thus, it will be appreciated that the gas turbine engine includes a low-speed spool, a rotor assembly coupled to the low-speed spool, and an electric machine coupled to the low-speed spool at a connection point of the low-speed spool.

[0100] Method 200 includes moving, at (202), a clutch positioned within the torque path of the low-speed spool between the connection point and the rotor assembly to a disengaged position such that the low-speed spool rotates independently of the rotor assembly. For the depicted exemplary aspect, moving the clutch to the disengaged position at (202) can include operating the gas turbine engine to generate electricity using the electric machine, which is coupled to the low-speed spool via an accessory gearbox, without rotating the rotor assembly of the gas turbine engine.

[0101] More specifically, for the depicted exemplary aspect, method (200) includes operating, at (204), the gas turbine engine at a speed of at least about 60% of the rated speed when the clutch is in the disengaged position, and converting, at (206), rotational energy from the low-speed spool into electricity using a generator while operating the gas turbine engine at a speed of at least about 60% of the rated speed when the clutch is in the disengaged position. It will be appreciated that in other exemplary aspects, operating the gas turbine engine at a speed of at least about 60% of the rated speed when the clutch is in the disengaged position at (204) can more specifically include operating the gas turbine engine at a speed of at least about 70% of the rated speed, such as at least about 80% of the rated speed, such as at least about 90% of the rated speed when the clutch is in the disengaged position. For such exemplary aspects, converting rotational energy from the low-speed spool into electricity using a generator at (206) while operating the gas turbine engine at a speed of at least about 60% of the rated speed can include converting rotational energy from the low-speed spool into electricity using a generator while operating the gas turbine engine at a speed of at least about 70% of the rated speed, such as at least about 80% of the rated speed, such as at least about 90% of the rated speed.

[0102] Still referring to Figure 7, method 200 further includes moving the clutch to an engaged position at (208) such that the low-speed tube shaft rotates with the rotor assembly. More specifically, for the depicted exemplary aspect, method 200 further includes moving the clutch from a disengaged position to a transition position at (210) until the rotor assembly rotates at substantially the same speed as the low-speed tube shaft. For such an exemplary aspect, moving the clutch to the engaged position at (208) such that the low-speed tube shaft rotates with the rotor assembly includes moving the clutch to the engaged position after moving the clutch from the disengaged position to the transition position at (212) until the rotor assembly rotates at substantially the same speed as the low-speed tube shaft.

[0103] Additional aspects of the present invention are provided by the subject matter of the following clauses:

[0104] A gas turbine engine, comprising: a turbine including a low-speed tube shaft; a rotor assembly coupled to the low-speed tube shaft; an electric machine mechanically coupled to the low-speed tube shaft at a connection point of the low-speed tube shaft; and a clutch positioned in a torque path of the low-speed tube shaft between the connection point and the rotor assembly.

[0105] The gas turbine engine according to one or more of these clauses, wherein the clutch is a two-stage clutch.

[0106] The gas turbine engine according to one or more of these clauses, wherein the clutch is movable between an engaged position and a disengaged position, wherein in the engaged position the rotor assembly is rotatable with the low-speed tube shaft, and in the disengaged position the rotor assembly is rotatably disengaged from the low-speed tube shaft.

[0107] The gas turbine engine according to one or more of these clauses, wherein the clutch includes a first part and a second part, wherein the clutch is further movable to a transition position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position.

[0108] The gas turbine engine according to one or more of these clauses, wherein the clutch includes a first part and a second part, wherein the first part includes a first geometric feature, wherein the second part includes a second geometric feature complementary in shape to the first geometric feature, and wherein the first geometric feature engages with the second geometric feature when the clutch is in the engaged position.

[0109] A gas turbine engine according to one or more of these clauses, characterized in that the clutch is further movable to a transition position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position, and wherein the first geometric feature and the second geometric feature are spaced apart when the clutch is in the transition position.

[0110] A gas turbine engine according to one or more of these clauses, characterized in that the gas turbine engine further comprises: an accessory gearbox, the accessory gearbox being coupled to the low-speed shaft at the connection point, and wherein the electric machine is coupled to the low-speed shaft via the accessory gearbox.

[0111] A gas turbine engine according to one or more of these clauses, characterized in that the gas turbine engine is configured as a single non-ducted rotor engine, and wherein the rotor assembly includes a single non-ducted rotor blade stage.

[0112] A gas turbine engine according to one or more of these clauses, characterized in that the gas turbine engine further comprises: a non-ducted guide vane stage positioned downstream of the single non-ducted rotor blade stage.

[0113] A gas turbine engine according to one or more of these clauses, characterized in that the turbine further comprises a core having a high-speed shaft.

[0114] A method of operating a gas turbine engine, the gas turbine engine including a low-speed shaft, a rotor assembly coupled to the low-speed shaft, and an electric machine coupled to the low-speed shaft at a connection point of the low-speed shaft, the method comprising: moving a clutch positioned within a torque path of the low-speed shaft between the connection point and the rotor assembly to a disengaged position such that the low-speed shaft rotates independently of the rotor assembly; and moving the clutch to an engaged position such that the low-speed shaft rotates with the rotor assembly.

[0115] The method according to one or more of these clauses, characterized in that moving the clutch to the disengaged position includes: operating the gas turbine engine without rotating the rotor assembly of the gas turbine engine to generate electricity using the electric machine driven by the accessory gearbox.

[0116] The method according to one or more of these clauses, characterized in that the method further comprises: moving the clutch from the disengaged position to a transitional position until the rotor assembly rotates at substantially the same speed as the low-speed shaft, and wherein moving the clutch to the engaged position such that the low-speed shaft rotates with the rotor assembly comprises: moving the clutch to the engaged position after moving the clutch from the disengaged position to the transitional position until the rotor assembly rotates at substantially the same speed as the low-speed shaft.

[0117] The method according to one or more of these clauses, characterized in that the method further comprises: operating the gas turbine engine at a speed equal to at least about 60% of the rated speed when the clutch is in the disengaged position; and converting rotational energy from the low-speed shaft into electrical power using the generator while operating the gas turbine engine at a speed equal to at least about 60% of the rated speed when the clutch is in the disengaged position.

[0118] A gas turbine engine, comprising: a turbine including a low-speed shaft; a rotor assembly coupled to the low-speed shaft; an accessory gearbox mechanically coupled to the low-speed shaft at a connection point thereof; and a clutch positioned in the torque path of the low-speed shaft between the connection point and the rotor assembly.

[0119] The gas turbine engine according to one or more of these clauses, characterized in that the clutch is a two-stage clutch.

[0120] The gas turbine engine according to one or more of these clauses, characterized in that the clutch is movable between an engaged position and a disengaged position, wherein in the engaged position the rotor assembly is rotatable with the low-speed shaft, and in the disengaged position the rotor assembly is rotationally disengaged from the low-speed shaft.

[0121] The gas turbine engine according to one or more of these clauses, characterized in that the clutch includes a first part and a second part, wherein the clutch is further movable to a transitional position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transitional position.

[0122] The gas turbine engine according to one or more of these clauses, characterized in that the gas turbine engine further comprises: an electric machine coupled to the low-speed shaft at the connection point, and wherein the electric machine is coupled to the low-speed shaft via the accessory gearbox.

[0123] A gas turbine engine according to one or more of these clauses, characterized in that the gas turbine engine is configured as a single ducted rotor engine, wherein the rotor assembly includes a single ducted rotor blade stage, and wherein the gas turbine engine further includes: a ducted guide vane stage positioned downstream of the single ducted rotor blade stage.

Claims

1. A gas turbine engine, comprising: a turbine including a low-speed shaft; a rotor assembly coupled to the low-speed shaft; an electric machine mechanically coupled to the low-speed shaft at a connection point thereof; and a clutch positioned in the torque path of the low-speed shaft between the connection point and the rotor assembly; wherein the clutch is movable between an engaged position and a disengaged position, and wherein the electric machine is configured to accelerate the rotor assembly once the clutch is moved to the engaged position during pre-flight operation and to convert rotational energy from the low-speed shaft into electrical energy without engaging the rotor assembly by moving the clutch to the disengaged position during idle and post-landing operation; and wherein the gas turbine engine further includes an inter-shaft clutch positioned between the low-speed shaft and a high-speed shaft, the inter-shaft clutch being configured to be engaged by rotation of the low-speed shaft during a start operation such that the low-speed shaft correspondingly rotates the high-speed shaft across the inter-shaft clutch.

2. The gas turbine engine according to claim 1, wherein, the clutch is a two-stage clutch.

3. The gas turbine engine according to claim 1, wherein, in the engaged position, the rotor assembly is rotatable with the low-speed shaft, and in the disengaged position, the rotor assembly is rotationally disengaged from the low-speed shaft.

4. The gas turbine engine according to claim 3, wherein, the clutch includes a first part and a second part, wherein the clutch is further movable to a transition position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position.

5. The gas turbine engine according to claim 3, wherein, the clutch includes a first part and a second part, wherein the first part includes a first geometric feature, wherein the second part includes a second geometric feature complementary in shape to the first geometric feature, and wherein the first geometric feature meshes with the second geometric feature when the clutch is in the engaged position.

6. The gas turbine engine according to claim 5, wherein, the clutch is further movable to a transition position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position, and wherein the first geometric feature and the second geometric feature are spaced apart when the clutch is in the transition position.

7. The gas turbine engine according to claim 1, wherein, the gas turbine engine further includes: an accessory gearbox coupled to the low-speed shaft at the connection point, and wherein the electric machine is coupled to the low-speed shaft via the accessory gearbox.

8. The gas turbine engine according to claim 1, wherein, the gas turbine engine is configured as a single non-ducted rotor engine, and wherein the rotor assembly includes a single non-ducted rotor blade stage.

9. The gas turbine engine according to claim 8, wherein, the gas turbine engine further includes: a non-ducted guide vane stage positioned downstream of the single non-ducted rotor blade stage.

10. The gas turbine engine according to claim 1, wherein, the turbine further includes a core having a high-speed shaft.

11. A method of operating a gas turbine engine, the gas turbine engine including a low-speed shaft, a rotor assembly coupled to the low-speed shaft, and an electric machine coupled to the low-speed shaft at a connection point of the low-speed shaft, the method comprises: moving a clutch positioned within a torque path of the low-speed shaft between the connection point and the rotor assembly to a disengaged position such that the low-speed shaft rotates independently of the rotor assembly to convert rotational energy from the low-speed shaft into electrical energy via the electric machine; moving the clutch to an engaged position such that the low-speed shaft rotates with the rotor assembly; and providing electrical power to the electric machine and converting it into rotational power to accelerate the rotor assembly; wherein the gas turbine engine further includes an inter-shaft clutch positioned between the low-speed shaft and the high-speed shaft, the inter-shaft clutch configured to engage by rotation of the low-speed shaft during a start operation such that the low-speed shaft correspondingly rotates the high-speed shaft across the inter-shaft clutch.

12. The method according to claim 11, wherein, moving the clutch to the disengaged position includes: operating the gas turbine engine without rotating the rotor assembly of the gas turbine engine to generate electrical energy using an electric machine driven by an accessory gearbox of the gas turbine engine.

13. The method according to claim 12, wherein, the method further includes: moving the clutch from the disengaged position to a transition position until the rotor assembly rotates at substantially the same speed as the low-speed shaft, and wherein moving the clutch to the engaged position such that the low-speed shaft rotates with the rotor assembly includes: moving the clutch to the engaged position after moving the clutch from the disengaged position to the transition position until the rotor assembly rotates at substantially the same speed as the low-speed shaft.

14. The method according to claim 12, wherein, the method further includes: operating the gas turbine engine at a speed equal to at least 60% of a rated speed when the clutch is in the disengaged position; operating the gas turbine engine at a speed equal to at least 60% of the rated speed when the clutch is in the disengaged position while converting rotational energy from the low-speed shaft into electrical energy using a generator.

15. A gas turbine engine, comprising: a turbine including a low-speed shaft; A rotor assembly coupled to the low-speed shaft; An accessory gearbox mechanically coupled to the low-speed shaft at the connection point of the low-speed shaft; An electric machine, the electric machine being coupled to the low-speed shaft via the accessory gearbox; And A clutch positioned in the torque path of the low-speed shaft between the connection point and the rotor assembly; Wherein the clutch is movable between an engaged position and a disengaged position, and wherein the electric machine is configured to accelerate the rotor assembly once the clutch is moved to the engaged position during pre-flight operation and to convert rotational energy from the low-speed shaft into electrical energy without engaging the rotor assembly by moving the clutch to the disengaged position during idling and post-landing operation; and Wherein the gas turbine engine further includes an inter-shaft clutch positioned between the low-speed shaft and the high-speed shaft, the inter-shaft clutch being configured to be engaged by rotation of the low-speed shaft during a start operation, such that the low-speed shaft correspondingly rotates the high-speed shaft across the inter-shaft clutch.

16. The gas turbine engine according to claim 15, Characterized in that The clutch is a two-stage clutch.

17. The gas turbine engine according to claim 15, Characterized in that In the engaged position, the rotor assembly is rotatable with the low-speed shaft, and in the disengaged position, the rotor assembly is rotationally disengaged from the low-speed shaft.

18. The gas turbine engine according to claim 17, Characterized in that The clutch includes a first part and a second part, wherein the clutch is further movable to a transition position, wherein the first part includes a first friction plate, wherein the second part includes a second friction plate, and wherein the first friction plate and the second friction plate are in contact with each other when the clutch is in the transition position.

19. The gas turbine engine according to claim 15, Characterized in that The gas turbine engine is configured as a single unducted rotor engine, wherein the rotor assembly includes a single stage of unducted rotor blades, and wherein the gas turbine engine further includes: An unducted guide vane stage positioned downstream of the single stage of unducted rotor blades.

Images