Hybrid engine speed regulation

Abstract

A method for operating a hybrid gas turbine engine is provided. The method includes: receiving data indicative of an actual rotational speed of a shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to a fuel flow control loop operable with a fuel delivery system of the hybrid propulsion engine; providing the calculated error to a motor control loop operable with an electric motor of the hybrid propulsion engine, the electric motor being drivingly coupled to the shaft; and modifying, using the electric motor control loop, a torque on the shaft from the electric motor based on the calculated error.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a non-provisional application claiming priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 63 / 072,573, filed on August 31, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present subject matter generally relates to a system and method for a hybrid engine to regulate the rotational speed of the engine. Background Art

[0004] 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 generally mounted on a corresponding one of the wings of the aircraft, such as in a hanging position under the wing, separate from the wing and the fuselage.

[0005] Hybrid propulsion systems are being developed to improve the efficiency of conventional commercial aircraft. Various hybrid propulsion systems include an electric motor driven by one of the aircraft engines. The inventors of the present disclosure have proposed various configurations and / or methods to improve currently known hybrid propulsion systems. Summary of the invention

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] In one exemplary aspect of the present disclosure, a method for operating a hybrid gas turbine engine is provided. The method includes: receiving data indicating an actual rotational speed of a shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to a fuel flow control loop operable with a fuel delivery system of a hybrid propulsion engine; providing the calculated error to a motor control loop operable with an electric motor of the hybrid propulsion engine, the electric motor being drivingly coupled to the shaft; and modifying, using the electric motor control loop, a torque on the shaft from the electric motor based on the calculated error.

[0008] These and other features, aspects and advantages of the present invention 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 present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0010] Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure.

[0011] Figure 2 is a schematic cross-sectional view of a gas turbine engine according to another exemplary embodiment of the present disclosure.

[0012] Figure 3 is a graph that describes the actual axis speed and the commanded axis speed.

[0013] Figure 4 is a schematic diagram of the control scheme used to control the axis speed.

[0014] Figure 5 is a flow chart of a method for operating a gas turbine engine. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to the present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. In the drawings and description, like or similar names are used to refer to like or similar parts of the invention.

[0016] As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and not for the purpose of indicating the position or importance of each component.

[0017] 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, in the case of a gas turbine engine, the front refers to a position near the engine air intake and the rear refers to a position near the engine nozzle or exhaust.

[0018] The terms "upstream" and "downstream" refer to the relative directions of flow in a path. For example, with respect to fluid flow, "upstream" refers to the direction from which the fluid is flowing, while "downstream" refers to the direction to which the fluid is flowing. However, the terms "upstream" and "downstream" as used herein may also refer to the flow of electricity.

[0019] The singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0020] Approximate language used herein throughout the specification and claims is applied to modify any quantitative representation that can be permitted to vary without resulting in a change in the basic function associated therewith. Therefore, the numerical value modified by one or more terms, such as "about", "approximately" and "substantially", is not limited to the precise numerical value specified. In at least some cases, the approximate language may correspond to the precision of the instrument measuring the value, or the precision of the method or machine of building or manufacturing parts and / or systems. In at least some cases, the approximate language may correspond to the precision of the instrument measuring the value, or the precision of the method or machine of building or manufacturing parts and / or systems. For example, the approximate language may refer to within 1, 2, 4, 5, 10, 15 or 20% of a single numerical value, a range of values ​​and / or an endpoint defining a range of values.

[0021] Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein include the endpoints, and the endpoints are independently combinable with each other.

[0022] It will be understood that any reference numbers used in this section may not refer to the same components and features as those associated with the same reference numbers in other sections.

[0023] The present disclosure generally relates to a system and method for regulating the rotational speed of a shaft of a gas turbine engine. For example, the system and method of the present disclosure can regulate the rotational speed of a low-pressure shaft of a gas turbine engine that drives a fan of the gas turbine engine.

[0024] The disclosed systems and methods utilize an electric motor capable of rotating with a shaft, and a control scheme including a fuel flow control loop and a motor control loop. The fuel flow control loop can generally be used to adjust the speed of the shaft by increasing or decreasing the fuel flow to the engine to control the shaft speed. In contrast, the motor control loop can resolve oscillations in shaft speed above and below a set shaft speed by adding or extracting relatively small amounts of power to or from the shaft.

[0025] In certain exemplary aspects, the system and method can receive data indicating an actual rotational speed of a shaft and calculate an error relative to a desired rotational speed of the shaft. The error can be provided to a fuel flow control loop and an electromechanical control loop. The motor control loop can provide a command to, for example, a motor power supply to provide power to the motor to modify the torque from the shaft of the motor based on the calculated error. Additionally or alternatively, the motor control loop can provide a command to, for example, the motor to extract power from the shaft of the motor based on the calculated error.

[0026] The disclosed system and method can normalize the rotational speed of the shaft during operation. This can reduce the cycles of certain components (e.g., within the fuel system) and further can improve the fuel consumption of the engine.

[0027] Reference now Figure 1 , provides a cross-sectional view of an exemplary embodiment of a gas turbine engine that may include one or more inventive aspects of the present disclosure. In particular, Figure 1 The exemplary gas turbine engine of FIG. 1 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. Figure 1 As can be seen, the engine 10 takes the form of an open rotor propulsion system and has a rotor assembly 12 that includes an array of airfoils, and more particularly an array of rotor blades 16, arranged about a central longitudinal axis 14 of the engine 10.

[0028] Moreover, as will be explained in more detail below, the engine 10 additionally includes a non-rotating bucket assembly 18 (i.e., non-rotating relative to the central axis 14) positioned rearward of the rotor assembly 12 and including an array of airfoils also arranged about the central axis 14, and more specifically includes an array of buckets 20 arranged about the central axis 14.

[0029] The rotor blades 16 are arranged in a typically equally spaced relationship about the centerline 14, and each blade has a root 22 and a tip 24 and a span defined therebetween. Likewise, the buckets 20 are also arranged in a typically equally spaced relationship about the centerline 14, and each bucket has a root 26 and a tip 28 and a span defined therebetween. The rotor assembly 12 also includes a hub 44 located forward of the plurality of rotor blades 16.

[0030] In addition, the engine 10 includes a turbine 30 having a core (or high pressure / high speed system) 32 and a low pressure / low speed system. It will be appreciated that, as used herein, the terms "speed" and "pressure" are used interchangeably with respect to the high pressure / high speed system and the low pressure / low speed system. Furthermore, it will be appreciated that the terms "high" and "low" are used in the same context to distinguish between the two systems and are not meant to imply any absolute speed and / or pressure values.

[0031] The core 32 generally includes a high-speed compressor 34, a high-speed turbine 36, and a high-speed shaft 38 extending therebetween and connecting the high-speed compressor 34 and the high-speed turbine 36. The high-speed compressor 34, the high-speed turbine 36, and the high-speed shaft 38 may be collectively referred to as the high-speed spool of the engine. In addition, a combustion section 40 is located between the high-speed compressor 34 and the high-speed turbine 36. The combustion section 40 may include one or more structures for receiving a mixture of fuel and air and providing combustion gases to flow through the high-speed turbine 36 to drive the high-speed spool.

[0032] 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 connected to the low speed compressor 44 and the low speed turbine 42. The low speed compressor 44, low speed turbine 42 and low speed shaft 46 may be collectively referred to as the low speed spool 55 of the engine.

[0033] Although engine 10 is described as having low-speed compressor 44 positioned ahead of high-speed compressor 34, in certain embodiments, compressors 34, 44 may be in a staggered arrangement. Additionally or alternatively, although engine 10 is described as having high-speed turbine 36 positioned ahead of low-speed turbine 42, in certain embodiments, turbines 36, 42 may similarly be in a staggered arrangement.

[0034] Still reference Figure 1 , the turbine 30 is generally encased in a cowling 48. Further, it will be appreciated that the cowling 48 at least partially defines an air inlet 50 and an exhaust 52, and includes a turbomachinery flow passage 54 extending therebetween. The air inlet 50, in the illustrated embodiment, is an annular or axisymmetric 360 degree air inlet 50 that is located between the rotor blade assembly 12 and the stationary or stationary vane assembly 18 and provides a path for incoming atmospheric air to enter the turbomachinery flow passage 54 inboard of the guide vanes 28 (as well as the compressor 44, 34, the combustion section 40, and the turbine 36, 42) along a radial direction R. Such a location may be advantageous for a variety of reasons, including managing icing performance and protecting the air inlet 50 from various objects and materials that may be encountered during operation.

[0035] However, in other embodiments, the air inlet 50 may be positioned at any other suitable location, such as, for example, behind the bucket assembly 18 , arranged in a non-axisymmetric manner, etc.

[0036] As shown, the rotor assembly 12 is driven by the turbine 30, and more specifically, by the low speed spool 55. More specifically, still Figure 1The engine 10 in the illustrated embodiment includes a power gearbox 56, and the rotor assembly 12 is driven by the low speed spool 55 of the turbine 30 through the power gearbox 56. In this manner, the rotating rotor blades 16 of the rotor assembly 12 can rotate about the axis 14 and generate thrust to propel the engine 10, and thus the aircraft associated therewith, in a forward direction F. For example, in some embodiments, the rotor assembly 12 can be driven by a power transmission mechanism similar to the power transmission mechanism 11 of FIG. Figure 1 One or more engines constructed in the manner described in the exemplary engine 10 may be incorporated into Figure 1 , 4 and / or 5's aircraft and utilized.

[0037] The power gearbox 56 may include a gear set for reducing the rotational speed of the low speed spool 55 relative to the low speed turbine 42 so that the rotor assembly 12 may rotate at a slower rotational speed than the low speed spool 55 .

[0038] As mentioned above, the engine 10 includes the bucket assembly 18. The bucket assembly 18 extends from the fairing 48 and is located behind the rotor assembly 12. The buckets 20 of the bucket assembly 18 can be mounted on a fixed 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 arrow F, which in turn defines the front and rear of the system. Figure 1 As shown, the rotor assembly 12 is located in front of the turbine 30 in a "pull" configuration, and the exhaust port 52 is located behind the guide vanes 28. As can be appreciated, the vanes 20 of the vane assembly 18 can be configured to straighten the airflow from the rotor assembly 12 (e.g., reduce swirl in the airflow) to improve the efficiency of the engine 10. For example, the size, shape, and configuration of the vanes 20 can be designed to cause the airflow from the rotor blades 16 to generate a reactionary swirl so that in the downstream direction behind the two rows of airfoils (e.g., blades 16, vanes 20), the swirl of the airflow is greatly reduced, which can translate into an increase in induced efficiency.

[0039] Still reference Figure 1 , it may be desirable for rotor blades 16, vanes 20, or both to include a pitch variation mechanism so that airfoils (e.g., blades 16, vanes 20, etc.) may be rotated independently or in conjunction with one another relative to a pitch axis of rotation. Such pitch variation may be used to vary thrust and / or swirl effects under various operating conditions, including adjusting the magnitude or direction of thrust generated on rotor blades 16, or providing a thrust reversal feature, which may be useful under certain operating conditions, such as during landing of an aircraft, or to desirably adjust acoustic noise generated at least in part by rotor blades 16, vanes 20, or from aerodynamic interactions of rotor blades 16 relative to vanes 20. More specifically, for Figure 1In the embodiment of the present invention, rotor assembly 12 is described as having a pitch change mechanism 58 for rotating rotor blades 16 about their respective pitch axes 60 , while bucket assembly 18 is described as having a pitch change mechanism 62 for rotating buckets 20 about their respective pitch axes 64 .

[0040] However, it is understandable that Figure 1 The exemplary single rotor non-ducted engine 10 depicted in FIG. 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 spools, turbines, compressors, etc.; fixed pitch blades 16, 20, or both; a direct drive configuration (i.e., the gearbox 56 may not be included); etc. For example, in other exemplary embodiments, the engine 10 may be a three-spool engine with a medium speed compressor and / or turbine. In such a configuration, it will be understood that the terms "high" and "low" herein with respect to speed and / or pressure of a turbine, compressor, or spool are terms of convenience for distinguishing between components, but do not require any specific relative speeds and / or pressures, and do not exclude additional compressors, turbines, and / or spools or shafts.

[0041] 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 turboshaft engine, a turboprop engine, a turbojet engine, etc. In addition, for example, although the engine is described as a single non-ducted rotor engine, in other embodiments, the engine may include a multi-stage open rotor configuration, and various aspects of the disclosure described below may be incorporated herein.

[0042] Further, in still other exemplary embodiments, the engine 10 may be configured as a ducted turbofan engine. Figure 2 , an engine 10 according to another exemplary embodiment of the present disclosure is described. Figure 2 The exemplary embodiment of the present invention is constructed in the same manner as described above with respect to Figure 1 The exemplary engine 10 of FIG. 1 is substantially the same, and the same or similar reference numerals may refer to the same or similar parts. However, as will be appreciated, for the illustrated embodiment, the engine 10 further includes a nacelle 80 that at least partially circumferentially surrounds the rotor assembly 12 and the turbine 30 to define a bypass passage 82 therebetween.

[0043] Now back to Figure 1, it will be appreciated that for the illustrated embodiment, the exemplary hybrid propulsion system further includes a fuel delivery system 66. The fuel delivery system 66 generally includes a fuel source 68 (which may be, for example, a fuel tank of an aircraft including the engine 10), one or more fuel lines 70 extending between the fuel source 68 and the combustion section 40 of the engine 10, and a fuel valve 72. The fuel valve 72 is in fluid communication with the one or more fuel lines 70 and is configured to regulate the flow of fuel from the fuel source 68 through the one or more fuel lines 70 to the combustion section 40. The fuel valve 72 may be referred to as a fuel metering unit ("FMU"), or may be configured as part of a fuel metering unit ("FMU"), and may generally control the power output of the engine 10.

[0044] Additionally, it will be further appreciated that the engine is integrated with the power system 100. The power system 100 generally includes an electric machine 102 coupled to at least one of a high voltage system (or core 32) or a low voltage system, and an energy storage unit 104.

[0045] Further, for the illustrated embodiment, the power system 100 includes a power bus 108 that electrically connects the various components of the power system 100. The power bus 108 may be, for example, one or more electrical wires arranged in any suitable configuration.

[0046] Still reference Figure 1 Although not depicted in the exemplary embodiments, it is understood that the exemplary power system may also include an auxiliary power unit. The auxiliary power unit, if included, may include an internal combustion engine driving a generator and may be located remotely from the engine 10. For example, in at least some exemplary embodiments, the auxiliary power unit, if provided, may be located within the fuselage of an aircraft using the engine 10, for example, at the rear end of the aircraft, and electrically coupled to the power bus 108.

[0047] Further, still for the illustrated embodiment, the motor 102 of the power system 100 is an LP motor 102A coupled to the low-pressure system of the engine. More specifically, for the illustrated embodiment, the LP motor 102A is embedded within the engine 10, located within or behind the turbine section of the engine 10, and inside the core airflow path 54 through the engine 10 in the radial direction R. However, it will be appreciated that in other exemplary embodiments, the LP motor 102A may be additionally or alternatively constructed in other suitable manners. For example, in other embodiments, the LP motor 102A may be embedded in the compressor section of the engine 10, may be located outside the core airflow path 54 in the radial direction R (and, for example, within the cowling 48), and so on.

[0048] In addition, for the illustrated embodiment, the LP motor 102A is not the only motor 102 of the electrical system 100 that is integrated with the engine 10. More specifically, the electrical system 100 further includes a high-voltage motor 102B that is coupled to the high-voltage system / core of the engine 10 and is electrically connected to the electrical bus 108. In the illustrated embodiment, the HP motor 102B is also embedded in the engine 10 at an inboard position of the core airflow path 54. However, in the illustrated embodiment, the HP motor 102B is located in the compressor section of the engine 10. It will be appreciated that in other embodiments, the HP motor 102B may alternatively be positioned outside the core airflow path 54 along the radial direction R and driven by, for example, a gear connection. For example, in certain embodiments, the HP motor 102B may be coupled to an accessory gearbox (not shown), which in turn is coupled to the high-voltage system of the engine 10.

[0049] In at least some exemplary embodiments, the energy storage unit 104 may include one or more batteries. In addition, or alternatively, the energy storage unit 104 may include one or more supercapacitor arrays, one or more supercapacitor arrays, or both. In at least some embodiments, the energy storage unit 104 may be configured to provide at least 5 kilowatts (kW) of energy to the power system 100, such as at least 50 kilowatts, such as at least 50 kilowatts, such as at least 250 kilowatts, such as at least 300 kilowatts, such as at least 350 kilowatts, such as at least 400 kilowatts, such as at least 500 kilowatts, such as up to 5 megawatts (MW), such as up to 10 megawatts (MW). In addition, the energy storage unit 104 may be configured to provide such electricity for at least two minutes, such as at least three minutes, such as at least five minutes, such as up to one hour.

[0050] Still reference Figure 1 , the exemplary power system 100 is operably connected to a controller 116. The controller 116 may be an engine controller for the engine 10 (eg, a full authority digital engine control controller), may be an aircraft controller, may be a controller dedicated to the power system 100, and so forth.

[0051] The controller 116 may be configured to receive data indicative of various operating conditions and parameters of the engine 10 during operation of the engine 10. For example, the engine 10 includes one or more sensors 114 configured to sense data indicative of various operating conditions and parameters of the engine 10, such as rotational speed, temperature, pressure, vibration, etc. However, more specifically, for Figure 1In the exemplary embodiment described in , the one or more sensors 114 include a first speed sensor 114A, which is configured to sense data indicating one or more parameters of the rotor assembly 12 (e.g., rotational speed, acceleration, torque on the rotor shaft driving the rotor assembly 12, etc.); a second sensor 114B, which is configured to sense data indicating the high pressure system (e.g., the rotational speed of the high pressure spool 38, the compressor outlet temperature, etc.); a third sensor 114C, which is configured to sense data indicating one or more combustion section parameters (e.g., the temperature within the combustion section 40, the fuel flowing to the combustion section 40, one or more pressures within or around the combustion section 40, etc.), one or more high pressure turbine parameters (such as turbine inlet temperature, the rotational speed of the high pressure turbine 36, etc.), or both; a fourth sensor 114D, which is operable to sense data indicating one or more parameters of the low pressure system (e.g., the rotational speed of the low pressure spool 55); and a fifth sensor 114E, which is configured to sense data indicating one or more variable geometry components (e.g., the position of one or more variable inlet guide vanes, outlet guide vanes, rotor blades 16, guide vanes 20, etc.).

[0052] With particular reference to the operation of the controller 116, in at least some embodiments, the controller 116 may include one or more computing devices 118. The computing devices 118 may include one or more processors 118A and one or more memory devices 118B. The one or more processors 118A may include any suitable processing device, such as a microprocessor, a microcontroller, an integrated circuit, a logic device, and / or other suitable processing device. The one or more memory devices 118B may include one or more computer-readable media, including but not limited to non-transitory computer-readable media, RAM, ROM, a hard disk, a flash drive, and / or other memory devices.

[0053] One or more memory devices 118B may store information accessible to one or more processors 118A, including computer-readable instructions 118C executable by one or more processors 118A. Instructions 118C may be any set of instructions that, when executed by one or more processors 118A, cause one or more processors 118A to perform operations. In some embodiments, instructions 118C may be executed by one or more processors 118A to cause one or more processors 118A to perform operations, such as any operations and functions for which controller 116 and / or computing device 118 are configured, operations for operating power system 100 (e.g., method 300), as described herein, and / or any other operations or functions of one or more computing devices 118. Instructions 118C may be software written in any suitable programming language, or may be implemented in hardware. In addition, and / or alternatively, instructions 118C may be executed on processor 118A in logically and / or virtually independent threads. Memory device 118B may further store data 118D accessible by processor 118A. For example, data 118D may include data indicative of power flow, data indicative of engine 10 / aircraft operating conditions, and / or any other data and / or information described herein.

[0054] The computing device 118 may also include a network interface 118E for communicating, for example, with other components of the engine 10, an aircraft incorporating the engine 10, the power system 100, and the like. For example, in the depicted embodiment, as described above, the engine 10 includes one or more sensors 114 for sensing data indicative of one or more parameters of the engine 10 and various accessory systems, and the power system 100 includes an energy storage unit 104, an LP motor 102A, an HP motor 102B, and an auxiliary power unit. The controller 116 is operably coupled to these components via, for example, the network interface 118E, so that the controller 116 can receive data indicative of various operating parameters sensed by the one or more sensors 114 during operation, various operating conditions of the components, and the like, and further can provide commands to control the amount of current and other operating parameters of the power system 100, for example, in response to the data and other conditions sensed by the one or more sensors 114.

[0055] The network interface 118E may include any suitable components for interfacing with one or more networks, including, for example, transmitters, receivers, ports, controllers, antennas, and / or other suitable components. For example, in the illustrated embodiment, the network interface 118E is configured to communicate wirelessly with these components via a wireless communication network (e.g., Figure 1 (shown by the dashed communication line in the middle).

[0056] The technology discussed herein refers to computer-based systems and actions taken by computer-based systems and information sent to and from them. Those of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for a large number of possible configurations, combinations, and division of tasks and functions between components. For example, the processing discussed herein can be implemented using a single computing device or a combination of computing devices. Databases, memories, instructions, and applications can be implemented on a single system or distributed on multiple systems. Distributed components can operate sequentially or in parallel.

[0057] Still reference Figure 1 It will be appreciated that during operation of the described system, the engine 10 may drive the rotor assembly 12 with the low pressure system, and more specifically, the low pressure turbine 42 via the low pressure shaft 55, and for the illustrated embodiment, further via the gearbox 56 and the rotor shaft / fan shaft (not shown). The low pressure turbine 42 is in turn driven by the flow of combustion gases generated in the combustion section 40 and flowing through the high pressure turbine 36. Therefore, as a general matter, in order to control the rotational speed of the rotor assembly 12, the engine 10 controls the flow of fuel through the fuel delivery system 66 to the combustion section 40 using, for example, the fuel metering unit 72, as this will control the amount / energy within the combustion gases provided through the high pressure turbine 36 and the low pressure turbine 42.

[0058] However, it will be appreciated that controlling the fuel flow alone may not provide the desired level of control over the rotational speed of the rotor assembly 12. For example, the fuel system may include flow dynamics, such as nonlinear flow dynamics, that prevent the desired level of control. For example, referring briefly to Figure 3 , provides a graph depicting the actual rotor speed (line 152) and the rotor speed command (at line 150) when the control scheme commands only fuel flow to control the rotational speed of the rotor assembly 12. In the graph, time is shown on the "X-axis" at 154 (in seconds) and rotational speed is shown on the "Y-axis" at 156 (in revolutions per minute, relative to the rotor speed command at line 150).

[0059] Depending on the rotor speed command, the rotor speed command and actual rotor speed may differ by at least approximately + / - 0.06% with a frequency of between 4 and 6 seconds. While such a difference is relatively small in magnitude, this may result in a relatively high number and frequency of control changes, which may reduce part life, consume additional energy, etc. Furthermore, under steady state conditions, such as cruise, this situation may provide an undesirable and / or adverse response to the pilot and / or aircraft.

[0060] To improve upon this architecture, the present disclosure utilizes aspects of a hybrid powertrain system to reduce and possibly effectively eliminate the difference between the rotor speed command and the actual rotor speed. More specifically, reference is now made to Figure 4 , depicts a schematic flow chart of a control scheme 200 that may be implemented by an engine controller to control the rotational speed of a rotor assembly. In certain exemplary embodiments, the control scheme 200 may be implemented using Figure 1 The controller 116 depicted in FIG. 1 is implemented to control the engine 10, particularly Figure 1 The rotor assembly 12.

[0061] As shown, the exemplary control scheme 200 generally includes a fuel flow control loop 202 and an electric motor control loop 204. The control scheme 200 receives a rotational speed command indicated by line 206, which may be received from an operator of an aircraft incorporating an engine being controlled. The control scheme 200 further receives an actual rotational speed indicated at line 208 and calculates an error between the rotational speed command and the actual rotational speed at a summing block 210.

[0062] It is noteworthy that, as used herein, the data indicating the rotational speed may refer to any suitable parameter for controlling the engine power and speed output. For example, the data may be speed data, may be pressure data (e.g., overall pressure ratio, engine pressure ratio, etc.), or similar data.

[0063] For the illustrated embodiment, the rotational speed command and actual rotational speed each refer to the speed of a low-pressure shaft that is drivingly connected to the rotor assembly, e.g. Figure 1 1. However, in other exemplary aspects, the rotational speed command and the actual rotational speed may instead each refer to the speed of the rotor shaft or other suitable shaft of the rotor assembly. For example, in other exemplary embodiments, the rotational speed command and the actual rotational speed may instead each refer to the speed of the high pressure shaft of the engine (e.g., Figure 1 and Figure 2 The speed of the shaft 38 of the engine 10).

[0064] The calculated error between the rotational speed command and the actual rotational speed is provided to the fuel flow control loop 202 and the motor control loop 204 .

[0065] The fuel flow control loop 202 receives the calculated error using a fuel flow controller 212. The fuel flow controller 212 then sends a command to a fuel valve 214 that controls the flow of fuel to the engine. The fuel valve 212 may be, for example, part of a fuel metering unit (see, for example, Figure 1Flow of fuel to the engine generally controls the amount of combustion gases produced within the combustion section and / or the amount of energy in the combustion gases, which in turn controls the rotational speed of the engine's high pressure system (including the high pressure turbine and high pressure shaft), which in turn controls the rotational speed of the low pressure system (including the low pressure turbine and low pressure shaft), which in turn directly controls the rotational speed of the rotor assembly.

[0066] Operating in parallel with the fuel flow control loop 202 is a motor control loop 204. The motor control loop 204 similarly receives a calculated error between a rotational speed command and an actual rotational speed using a motor controller 216. Based at least in part on the calculated error between the received rotational speed command and the actual rotational speed, the motor controller 216 provides a power command, represented at line 218, to a motor power divider 220, which in turn provides the commanded amount of power to the motor, which in turn can convert the received amount of electrical power into mechanical power and provide such mechanical power directly to the low pressure shaft, which in turn controls the rotational speed of the rotor assembly, as previously described.

[0067] Furthermore, for the exemplary aspects described, the motor controller 216 is configured as a multiple-input, single-output controller that is configured to receive feedback of the calculated error and the actual amount of power provided to the motor as shown by line 222. In this manner, the motor controller 216 can provide power to the motor with relatively high accuracy. Furthermore, by being so configured, the controller 216 can minimize the amount of motor power required over time to minimize the amount of power provided or drawn.

[0068] However, in other exemplary embodiments, the motor controller 216 of the motor control loop 204 may be a single-input, single-output controller that does not receive feedback of the actual amount of power being provided. In such a configuration, the primary feedback would be in response to receiving updated actual rotational speed data indicated by line 208 in the form of an updated error value calculated at summation 210.

[0069] As will be appreciated, due to the nature of the fuel flow control loop 202, the fuel flow control loop 202 can operate at a lower frequency than the motor control loop 204. For example, in at least some exemplary aspects, the fuel flow control loop 202 can operate at a first frequency, and the motor control loop 204 can operate at a second frequency, the second frequency being higher than the first frequency. In certain exemplary aspects, the second frequency can be at least about 5 times higher than the first frequency, such as at least about 10 times higher than the first frequency, such as up to 500 times higher than the first frequency. With such a configuration, there is less concern that the fuel flow control loop 202 and the motor control loop 204 will compete with each other to control the rotational speed of the rotor assembly.

[0070] Furthermore, given the relatively small changes required to normalize the rotational speed of the rotor assembly / low pressure shaft relative to the commanded speed, Figure 4 The amount of power added to the low-pressure shaft in the control scheme 200 can be relatively small. For example, in some embodiments, the control scheme 200 can use the motor via the motor control loop 204 to add less than about 30 horsepower ("hp") of power to the low-pressure shaft, such as less than 30 hp, such as less than 25 hp, such as less than 20 hp, such as less than 15 hp, such as at least 1 hp, such as at least 3 hp, such as at least 5 hp, such as at least 10 hp.

[0071] It is understandable that for the above reference Figure 1 The exemplary engine depicted and described may utilize the controlled electric machine during various flight operations. In this manner, when the control scheme 200 is operating to normalize the rotor speed, the electric machine may already be adding power to the engine, or may already be extracting power from the engine. Therefore, it can be appreciated that, at least in certain exemplary aspects, the control scheme 200 may be configured to add power to the low pressure shaft with the electric machine in addition to the power already provided.

[0072] Furthermore, it will be appreciated that in certain exemplary aspects of the present disclosure, the control scheme 200 may additionally or alternatively extract power to normalize the rotational speed of the rotor assembly. For example, the control scheme 200 may provide a command to extract an amount of power to provide a similar result, rather than providing power to the motor. Furthermore, for embodiments where the motor is already extracting power from the engine, the control scheme 200 may be configured to reduce the amount of power extracted from the low-pressure shaft with the motor relative to the power already extracted.

[0073] according to Figure 4 Exemplary aspects of the control scheme 200 depicted in the drawings control the rotational speed of the low-pressure shaft to result in a relatively low difference between the actual rotational speed of the rotor assembly or the low-pressure shaft and the commanded rotational speed of the rotor assembly or the low-pressure shaft. For example, in certain exemplary aspects, when the engine is operating in a steady state, and when the low-pressure system rotational speed is greater than about 500 revolutions per minute ("RPM"), such as greater than about 1000 RPM, such as greater than about 1500 RPM, such as greater than about 2000 RPM, such as greater than about 2500 RPM, such as greater than about 3000 RPM, such as greater than about 3500 RPM, such as greater than about 4000 RPM, such as less than about 10000 RPM, according to Figure 4 Exemplary aspects of the control scheme 200 depicted in FIG. 2 may control the rotational speed of the low-pressure shaft resulting in a variance of less than about ±0.05%, such as less than about ±0.02%.

[0074] However, it will be understood that Figure 4 The exemplary control scheme 200 depicted in FIG. 1 is provided by way of example only. In other exemplary aspects, any other suitable control schemes and methods may be provided. For example, although for Figure 4 In the exemplary control scheme 200 depicted in the drawings, the motor is drivingly coupled to the low-pressure shaft, and other exemplary aspects, but the motor controlled according to the disclosed control scheme 200 can be drivingly coupled to, for example, a high-pressure shaft, a fan shaft / rotor shaft, etc. In this way, the control scheme can be configured to control the rotational speed of a shaft drivingly coupled to the motor, or the rotational speed of different shafts. For example, when the motor controlled by the control scheme 200 is coupled to the high-pressure shaft, the control scheme can adjust the rotational speed of the high-pressure shaft and, to a certain extent, the rotational speed of the low-pressure shaft. Data indicating the actual rotational speed received by the control scheme can be used to couple to the shaft of the motor.

[0075] Furthermore, although the exemplary control scheme 200 is described as having separate control loops and controllers (e.g., separate controllers 216, 212, 220), it will be appreciated that in certain exemplary aspects, reference is made to the Figure 4 The commands of the control scheme 200 depicted and described may each be incorporated into any other suitable controller configuration, such as into a single controller, such as the one described above with reference to FIG. Figure 1 An example controller 116 is described, among other things.

[0076] Reference now Figure 5 , a flow chart of a method 300 for operating a hybrid gas turbine engine according to an exemplary aspect of the present disclosure is provided. The exemplary method 300 may be used with reference to Figure 4 The exemplary control scheme 200 described above is used to control Figure 1 An exemplary engine 10 is described in terms of how the engine is constructed.

[0077] The method 300 includes receiving data indicating a commanded rotational speed of a shaft at (302), and receiving data indicating an actual rotational speed of the shaft at (304). It will be appreciated that receiving data indicating a commanded rotational speed of the shaft at (302) may include receiving data from an aircraft controller, an engine controller, etc., of an aircraft including the engine.

[0078] Further, for the described exemplary aspects, receiving data indicating an actual rotational speed of the shaft at (304) may include receiving data indicating a fuel flow to the hybrid gas turbine engine, a rotational speed parameter of a rotor assembly coupled to and driven by the shaft, a rotational speed parameter of the shaft, a torque applied to a rotor shaft of the rotor assembly, a rotational speed parameter of a high pressure system of the hybrid gas turbine engine, a pressure ratio parameter, or a combination thereof at (306). The rotational speed parameter may include a rotational speed, a rotational acceleration, or a combination thereof. The pressure ratio parameter may include an overall pressure ratio, an engine pressure ratio, a compressor pressure ratio, and the like.

[0079] Further, as noted, the method 300 may be used to control a device similar to that described above with reference to Figure 1 The exemplary engine 10 is described as an engine. Thus, it can be appreciated that the shaft can be a low-pressure shaft of a gas turbine engine, and further, the gas turbine engine can include a rotor assembly coupled to and driven by the low-pressure shaft.

[0080] However, in other exemplary aspects, any other suitable engine may be controlled according to exemplary method 300 .

[0081] Still reference Figure 5 The method 300 further includes calculating an error between an actual rotational speed of the shaft and a commanded rotational speed of the shaft at (308), providing the calculated error to a motor control loop operable with an electric motor of the hybrid propulsion engine at (312). For the exemplary aspect being described, the electric motor is drivingly coupled to the shaft.

[0082] Further, for exemplary aspects of method 300, the method further includes controlling the rotational speed of the shaft at least in part with a fuel flow control loop capable of operating with a fuel delivery system of a hybrid propulsion engine. More specifically, for the exemplary aspects described, controlling the rotational speed of the shaft at least in part with a fuel flow control loop capable of operating with a fuel delivery system of a hybrid propulsion engine includes, at (310), providing a calculated error to the fuel flow control loop capable of operating with a fuel delivery system of a hybrid propulsion engine. In addition, for the exemplary aspects described, controlling the rotational speed of the shaft at least in part with a fuel flow control loop capable of operating with a fuel delivery system of a hybrid propulsion engine further includes, at (314), modifying the fuel flow to the hybrid gas turbine engine with the fuel flow loop based on the calculated error provided to the fuel flow loop at (310). In certain exemplary aspects, modifying the fuel flow to the hybrid gas turbine engine at (314) may include modifying the fuel flow using a fuel metering unit.

[0083] Similarly, the exemplary method 300 further includes, at (316), modifying, using the motor control loop, the torque on the shaft from the motor based on the calculated error provided to the motor control loop at (312). In the described exemplary aspect, modifying, at (316), the torque on the shaft from the motor includes adding torque from the motor to the shaft at (318). More specifically, in the described exemplary aspect, modifying, at (316), the torque on the shaft from the motor includes adding, at (320), 5 horsepower to 30 horsepower to the shaft using the motor.

[0084] Notably, in certain exemplary aspects, modifying the torque at the shaft from the electric machine at (316) may include modifying the torque at the shaft from the electric machine relative to a baseline amount of torque added to or extracted from the shaft. For example, the electric machine may be part of a hybrid engine that operates at a baseline level of operating conditions (e.g., a cruise operating mode) and adds a baseline amount of torque to or extracts a baseline amount of torque from the shaft.

[0085] As can be appreciated, the process of controlling the rotational speed of a shaft using a fuel flow control circuit can be relatively slow. For example, in order to control the rotational speed of a shaft using a fuel flow control circuit, the amount of fuel provided to the engine must be modified, and such modification requires time to change the amount of energy provided to the high pressure system of the engine, which in turn translates into a change in the rotational speed of the low pressure system of the engine (e.g., the low pressure shaft of the engine).

[0086] In contrast, the motor control loop can operate relatively quickly because (theoretically at least) commanded modifications to the torque of the shaft using the motor control loop can be implemented at the speed of the electrical power passing through the motor control loop to the motor drivingly coupled to the shaft. Accordingly, for example, it will be appreciated that for Figure 5 In an exemplary aspect of the method 300 depicted in FIG. 1 , the fuel flow control loop may be operated at a first frequency and the motor control loop may be operated at a second frequency. The second frequency may be higher than the first frequency, such as at least about 5 times higher than the first frequency, such as at least about 10 times higher than the first frequency, such as up to one thousand times higher than the first frequency.

[0087] according to Figure 5 The exemplary aspects of the method 300 depicted in FIG. 1 control the rotational speed of a rotor assembly drivingly coupled to a shaft to effectively reduce or eliminate the difference between the actual rotational speed of the shaft and the commanded rotational speed of the shaft. For example, in Figure 5In an exemplary aspect of the method 300 depicted in , the method 300 further includes, at (322), rotating the rotor assembly with the shaft at a rotational speed defined as a difference of less than ±0.005%, such as a difference of less than about ±0.002%. Rotating the rotor assembly with the shaft at (322) may include rotating the rotor assembly with the shaft at a rotational speed of at least 500 RPM, such as at least 1000 RPM, such as at least 1500 RPM, such as at least 2000 RPM, such as at least 2500 RPM, such as at least 3000 RPM, such as at least 3500 RPM, such as at least 4000 RPM.

[0088] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include 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 language of the claims.

[0089] Further aspects of the invention are provided by the subject matter of the following clauses:

[0090] A method for operating a hybrid gas turbine engine, comprising: controlling the rotational speed of a shaft at least in part with a fuel flow control loop capable of operating with a fuel delivery system of the hybrid propulsion engine; receiving data indicating an actual rotational speed of the shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to a motor control loop capable of operating with an electric motor of the hybrid propulsion engine, the electric motor being drivingly connected to the shaft; and modifying the torque on the shaft from the electric motor using the motor control loop based on the calculated error.

[0091] Method according to one or more of these clauses, wherein said shaft is a low pressure shaft of said gas turbine engine.

[0092] The method according to one or more of these clauses, wherein the gas turbine engine further comprises a rotor assembly coupled to and driven by the shaft.

[0093] A method according to one or more of these clauses, wherein the fuel flow control loop operates at a first frequency, wherein the motor control loop operates at a second frequency, and wherein the second frequency is higher than the first frequency.

[0094] A method according to one or more of these clauses, wherein the second frequency is at least five times faster than the first frequency.

[0095] A method according to one or more of these clauses, wherein the second frequency is at least about 10 times faster than the first frequency.

[0096] A method according to one or more of these clauses, wherein modifying the torque on the shaft from the electric machine comprises adding torque from the electric machine to the shaft.

[0097] The method of one or more of these clauses, modifying the torque at the shaft from the electric machine comprises adding 5 to 30 horsepower to the shaft using the electric machine.

[0098] A method according to one or more of these clauses, wherein receiving data indicating the actual rotational speed of the shaft includes receiving data indicating a fuel flow to the hybrid gas turbine engine, a rotational speed parameter of a rotor assembly coupled to and driven by the shaft, a rotational speed parameter of the shaft, a torque applied to a rotor shaft of the rotor assembly, a rotational speed parameter of a high pressure system of the hybrid gas turbine engine, or a combination thereof.

[0099] A method according to one or more of these clauses, wherein controlling the rotational speed of the shaft at least partially with the fuel flow control circuit further comprises: providing the calculated error to the fuel flow control circuit capable of operating with a fuel delivery system of the hybrid propulsion engine; and based on the calculated error, utilizing the fuel flow circuit to modify the fuel flow to the hybrid gas turbine engine.

[0100] A method according to one or more of these clauses, wherein the motor control loop includes a multi-input, single-output controller, the multi-input, single-output controller is constructed to receive the calculated error and provide a power command output, the multi-input, single-output controller is constructed to receive the calculated error and a motor power feedback signal, and is further constructed to provide a power command to control the power of the motor.

[0101] A method according to one or more of these clauses, wherein the motor control loop includes a single-input, single-output controller, which is configured to receive an output of the calculated error and provide a power command to control the power of the motor.

[0102] The method according to one or more of these clauses, wherein the gas turbine engine is a non-ducted rotor turbofan engine.

[0103] A method according to one or more of these clauses, wherein the gas turbine engine is a single non-ducted rotor turbofan engine.

[0104] The method according to one or more of these clauses, further comprising rotating the rotor assembly with the shaft at a rotational speed defining a variance of less than ±0.005%.

[0105] The method according to one or more of these clauses, further comprising rotating the rotor assembly with the shaft at a rotational speed defining a variance of less than ±0.002%.

[0106] A controller for a gas turbine engine, comprising a memory and one or more processors, the memory storing instructions that, when executed by the one or more processors, perform the following control steps: controlling the rotational speed of a shaft at least in part using a fuel flow control loop capable of operating with a fuel delivery system of the hybrid propulsion engine; receiving data indicating an actual rotational speed of the shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to a motor control loop capable of operating with a motor of the hybrid propulsion engine, the motor being drivingly connected to the shaft; and modifying the torque on the shaft from the motor using the motor control loop based on the calculated error.

[0107] A controller according to one or more of these clauses, wherein the fuel flow control loop is configured to operate at a first frequency, wherein the motor control loop is configured to operate at a second frequency, and wherein the second frequency is higher than the first frequency.

[0108] A controller according to one or more of these clauses, wherein the second frequency is at least five times faster than the first frequency.

[0109] A controller according to one or more of these clauses, wherein the controller is further configured to modify fuel flow to the hybrid gas turbine engine using the fuel flow circuit based on the calculated error.

[0110] A controller according to one or more of these clauses, wherein the controller is further configured to perform one or more steps of the method of one or more of these clauses.

[0111] An aerial vehicle comprising a controller in accordance with one or more of these clauses, operable in accordance with a method in accordance with one or more of these clauses, or both.

Claims

1. A method of operating a hybrid gas turbine engine, characterized in that include: controlling a rotational speed of the shaft at least in part with a fuel flow control circuit operable with a fuel delivery system of the hybrid gas turbine engine; receiving data indicative of an actual rotational speed of the shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to an electric machine control loop operable with an electric machine of the hybrid gas turbine engine, the electric machine drivingly coupled to the shaft; as well as modifying, using the motor control loop, a torque on the shaft from the motor based on the calculated error; Wherein the fuel flow control loop operates at a first frequency, wherein the motor control loop operates at a second frequency, and wherein the second frequency is higher than the first frequency.

2. The method according to claim 1, characterized in that Wherein the shaft is a low pressure shaft of the hybrid gas turbine engine.

3. The method according to claim 1, characterized in that The hybrid gas turbine engine further includes a rotor assembly coupled to the shaft and driven by the shaft.

4. The method according to claim 1, characterized in that Wherein the second frequency is at least five times faster than the first frequency.

5. The method according to claim 1, characterized in that The second frequency is at least 10 times faster than the first frequency.

6. The method according to claim 1, characterized in that Wherein modifying the torque on the shaft from the electric machine comprises adding torque from the electric machine to the shaft.

7. The method according to claim 1, characterized in that Modifying the torque at the shaft from the electric machine includes adding 5 horsepower to 30 horsepower to the shaft using the electric machine.

8. The method according to claim 1, characterized in that Wherein receiving data indicating the actual rotational speed of the shaft includes receiving data indicating a fuel flow to the hybrid gas turbine engine, a rotational speed parameter of a rotor assembly coupled to and driven by the shaft, a rotational speed parameter of the shaft, a torque applied to a rotor shaft of the rotor assembly, a rotational speed parameter of a high pressure system of the hybrid gas turbine engine, or a combination thereof.

9. The method according to claim 1, characterized in that: Wherein controlling the rotational speed of the shaft at least in part with the fuel flow control circuit further comprises: providing the calculated error to the fuel flow control loop operable with a fuel delivery system of the hybrid gas turbine engine; and The fuel flow circuit is utilized to modify fuel flow to the hybrid gas turbine engine based on the calculated error.

10. The method according to claim 1, characterized in that The motor control loop includes a multi-input, single-output controller, which is configured to receive the calculated error and provide a power command output. The multi-input, single-output controller is configured to receive the calculated error and a motor power feedback signal and is further configured to provide a power command to control the power of the motor.

11. The method according to claim 1, characterized in that: The motor control loop includes a single-input, single-output controller configured to receive an output of the calculated error and provide a power command to control the power of the motor.

12. The method according to claim 1, characterized in that The hybrid gas turbine engine is a non-ducted rotor turbofan engine.

13. The method according to claim 1, characterized in that The hybrid gas turbine engine is a single non-ducted rotor turbofan engine.

14. The method according to claim 1, characterized in that Further including: The rotor assembly is rotated using the shaft at a rotational speed defined within ±0.005%.

15. The method according to claim 1, characterized in that Further including: The shaft is used to rotate the rotor assembly at a rotational speed defined within ±0.002%.

16. A controller for a hybrid gas turbine engine, characterized in that: The invention comprises a memory and one or more processors, wherein the memory stores instructions, and when the instructions are executed by the one or more processors, the following control steps are performed: controlling a rotational speed of the shaft at least in part with a fuel flow control circuit operable with a fuel delivery system of the hybrid gas turbine engine; receiving data indicative of an actual rotational speed of the shaft; calculating an error between the actual rotational speed of the shaft and a commanded rotational speed of the shaft; providing the calculated error to an electric machine control loop operable with an electric machine of the hybrid gas turbine engine, the electric machine drivingly coupled to the shaft; as well as modifying, using the motor control loop, a torque on the shaft from the motor based on the calculated error; Wherein the fuel flow control circuit is configured to operate at a first frequency, wherein the motor control circuit is configured to operate at a second frequency, and wherein the second frequency is higher than the first frequency.

17. The controller according to claim 16, characterized in that: Wherein the second frequency is at least five times faster than the first frequency.

18. The controller according to claim 16, characterized in that: Wherein the controller is further configured to modify fuel flow to the hybrid gas turbine engine using the fuel flow circuit based on the calculated error.

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