Gas turbine engine with clutch system

Abstract

The present invention relates to a gas turbine engine with a clutch system. A gas turbine engine comprises: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in serial flow communication; and a clutch having a disengagement structure and an engagement structure, in which the low-pressure turbine is drivingly disconnected from the low-pressure compressor, so that in the disengagement structure, the clutch disengages the low-pressure turbine from the low-pressure compressor, in the engagement structure, the low-pressure turbine is drivingly connected to the low-pressure compressor, and in both the engagement structure and the disengagement structure of the clutch, the low-pressure turbine is drivingly connected to the output shaft.

Description

Technical Field

[0001] The present application relates generally to gas turbine engines and, more particularly, to multi-spool engine architectures. Background Art

[0002] Many gas turbine engine architectures with multiple stages have a low-pressure compressor, a high-pressure compressor, a high-pressure turbine, and a low-pressure turbine, which are sequentially arranged in this order along the axial direction of the engine. The low-pressure compressor at a first end of the engine is drivingly connected to the low-pressure turbine at the opposite end of the engine via a low-pressure shaft, which extends concentrically through a hollow high-pressure shaft, which in turn drivingly connects the high-pressure turbine to the high-pressure compressor. Summary of the invention

[0003] In one aspect, a gas turbine engine is provided, comprising: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in serial flow communication; and a clutch having a disengaged structure and an engaged structure, in which the low-pressure turbine is drivingly disconnected from the low-pressure compressor, so that in the disengaged structure, the clutch disengages the low-pressure turbine from the low-pressure compressor, and in the engaged structure, the low-pressure turbine is drivingly connected to the low-pressure compressor, and in both the engaged structure and the disengaged structure of the clutch, the low-pressure turbine is drivingly connected to the output shaft.

[0004] On the other hand, a gas turbine engine is provided, comprising: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in serial flow communication; and a system for selectively engaging the low-pressure compressor to one or both of the high-pressure compressor and the low-pressure turbine.

[0005] On the other hand, a method for a gas turbine engine is provided, wherein the gas turbine engine has a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly engaged with the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft, the method comprising: receiving a power request; while maintaining the low-pressure turbine drivingly connected to the output shaft, if the power request is lower than a power threshold, setting the gas turbine engine to a free turbine configuration by disengaging the low-pressure compressor from the low-pressure turbine; while maintaining the low-pressure turbine drivingly connected to the output shaft, if the power request is higher than the power threshold, setting the gas turbine engine to a boost configuration by engaging the low-pressure compressor to the low-pressure turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Reference is now made to the accompanying drawings, in which:

[0007] Figure 1 is a schematic cross-sectional view of a reverse flow gas turbine engine according to one embodiment; and

[0008] Figure 2 is a schematic cross-sectional view of a through-flow engine according to one embodiment. DETAILED DESCRIPTION

[0009] Figure 1 A first example of a multi-spool gas turbine engine 10 of the type described is illustrated, namely: a multi-spool gas turbine engine 10 of the type preferably arranged for use in subsonic flight and generally comprising an engine core having a turbine having a plurality of spools which perform compression to pressurize the atmosphere received through an air intake 13 and extract energy from the combustion gases before the combustion gases leave the engine via an exhaust 17. The engine core also comprises a core gas path 11 to direct the gases from the air intake 13 to the exhaust 17, as shown in FIG. Figure 1 The core gas path 11 may be annular and concentric with respect to the engine centerline CL.

[0010] The term "spool" is intended herein to broadly refer to drivingly connected turbine and compressor rotors, and is therefore not limited to compressor and turbine assemblies on a single shaft. As will be seen below, it also includes rotating assemblies with multiple shafts geared together.

[0011] exist Figure 1In the embodiment shown in , the engine core includes a low pressure (LP) spool 12 and a high pressure (HP) spool 14. The LP spool 12 generally includes: an LP compressor 12a for pressurizing air received from an air intake 13; and an LP turbine 12b for extracting energy from combustion gases discharged from a combustor 15 in which the compressed air is mixed with fuel and ignited to produce an annular flow of hot combustion gases. The LP turbine 12b may be mechanically connected to the LP compressor 12a. The flow communication between the two LP compressors 12a and the low pressure turbine 12b is via the core gas path 11 through the high pressure spool 14 and the combustor 15. According to Figure 1 In one aspect of the embodiment shown in FIG. 1 , the LP compressor 12 a and the LP turbine 12 b are coaxially mounted for rotation about a common axis, which may correspond to an engine centerline CL.

[0012] The HP rotor 14 generally includes an HP compressor 14a, which is connected in flow communication with the LP compressor 12a to receive pressurized air from the LP compressor 12a via the core gas path 11. The HP rotor also includes an HP turbine 14b, which can be located immediately downstream of the combustor 15. The HP turbine 14b is drivingly connected to the HP compressor 14a via an HP shaft 14c. The HP shaft 14c can be coaxial with the engine centerline CL. In the illustrated embodiment, the LP compressor 12a, the LP turbine 12b, the HP turbine 14b and the HP compressor 14a are all mounted for rotation about the engine centerline CL. The HP rotor can be drivingly connected to an accessory gearbox (AGB) 28, which can be side mounted and drivingly connected to the HP pressure rotor via a tower shaft 29. Alternatively, the AGB 28 can be coaxially mounted at the rear end of the engine 10 to provide a drive output to various accessories (e.g., a fuel pump, a starter generator, an oil pump, a scavenge air pump, etc.). For example, the HP shaft 14 c may extend axially beyond the HP compressor 14 a through a central bore of the LP compressor 12 a to provide a drive input to the AGB 28 .

[0013] The LP turbine 12 b is also referred to as a power turbine. The LP turbine 12 b can drive two or more rotatable loads. According to the illustrated embodiment, the first load is a propeller 16 that provides thrust for flight and taxiing in an aircraft application. However, it is to be understood that the first load can be any suitable component capable of receiving rotational drive from the LP turbine 12 b, or any combination of suitable components. For example, in the case where the engine 10 is a turbine shaft rather than a rotor shaft, the first load can be a propeller 16 that provides thrust for flight and taxiing in an aircraft application. However, it is to be understood that the first load can be any suitable component capable of receiving rotational drive from the LP turbine 12 b, or any combination of suitable components. Figure 1In alternative embodiments of the turboprop engine depicted in , the first load may include a helicopter main and / or tail rotor, a pump, a generator, a gas compressor, a marine propeller, or the like.

[0014] exist Figure 1 In the embodiment shown in FIG. 1 , the first load (i.e., the propeller 16) is drivingly coupled to an output shaft 18 extending axially from an output end of a reduction gearbox (RGB) 20. The input end of the RGB 20 is mechanically coupled to the LP turbine shaft 12c, which is drivingly connected to the LP turbine 12b. Figure 1 As shown in , the LP turbine shaft 12c and the output shaft 18 may be coaxial with the engine centerline CL. The RGB 20 processes and outputs the rotational drive transmitted to it from the LP turbine 12b via the LP turbine shaft 12c through known gear reduction techniques. The RGB 20 allows the propeller 16 to be driven at a rotational speed different from the rotational speed of the LP turbine 12b, which can thereby provide better efficiency.

[0015] Still reference Figure 1 , the LP turbine 12b can selectively drive the LP compressor 12a. According to one aspect of the illustrated embodiment, the LP compressor 12a can be selectively drivingly connected to the LP turbine 12b via the LP compressor drive shaft 12d. Figure 1 It will be appreciated that the LP compressor drive shaft 12d is an external shaft. It will be appreciated that the LP compressor drive shaft 12d may be internal, i.e. radially internal to the core gas path 11, and may extend through the engine HP shaft 14c. In the illustrated embodiment, the LP compressor drive shaft 12d is disposed radially external to the engine core, and more specifically, radially external to the outer periphery of the core gas path 11. In other words, the LP compressor drive shaft 12d is radially offset from the core gas path 11. As shown, the external shaft 12d may be parallel to the HP shaft 14c, but radially offset relative thereto. In the illustrated embodiment, the LP compressor drive shaft 12d axially spans the HP rotor 14 including the HP turbine 14b, the HP compressor 14a, and the HP pressure shaft 14c, and is connected to the LP turbine shaft 12c at the input end by a first mechanical coupling 30, and is connected to the LP compressor 12a at its output end via a second mechanical coupling 32. The LP compressor drive shaft 12d may axially overlap the core gas path 11.

[0016] like Figure 1Schematically depicted in dashed lines in FIG, the first mechanical coupling 30 and the second mechanical coupling 32 may be disposed at various axially spaced locations relative to the LP turbine 12b and the LP compressor 12a. For example, the first mechanical coupling 30 is shown as being adjacent to the RGB 20 downstream of the LP turbine 12b relative to the gas flowing through the core gas path 11. The second mechanical coupling 32 is shown as being adjacent to the AGB 28 on the upstream side of the LP compressor 12a. The LP compressor 12a may be provided with a shaft extension 12a' that protrudes axially from the upstream side of the LP compressor rotor for connection with the mechanical coupling 32. Alternatively, the first mechanical coupling 30 and the second mechanical coupling 32 may be positioned closer to the LP turbine 12b and the LP compressor 12a, respectively, and even positioned on the upstream side of the LP turbine 12b and the downstream side of the LP compressor 12a, respectively. These alternative mechanical locations may be used to reduce the length of the LP compressor drive shaft 12d, or to accommodate different mechanical constraints.

[0017] The mechanical couplings 30, 32 may be arranged in the form of a gear set, thereby allowing the mechanical speed between each section to be varied. Thus, the LP turbine 12b and the LP compressor 12a may have different speeds to optimize performance or accommodate mechanical constraints. In addition, the gears may also be configured so that the direction of rotation of the LP compressor (clockwise or counterclockwise) is opposite to the direction of rotation of the HP compressor 14a. In another version, the configuration may be arranged so that the LP turbine 12b rotates in the opposite direction of the HP turbine 14b. This may allow for reduced flow turning losses in the transition between turbine components.

[0018] Each mechanical coupling 30, 32 may also include a tower shaft or the like to allow the outer LP compressor shaft 12d to be positioned further away from the engine centerline CL. Furthermore, it is to be understood that any suitable type of mechanical coupling suitable for transmitting torque from the LP turbine 12b to the LP compressor 12a may be used (i.e., the mechanical couplings are not limited to gear sets or the like).

[0019] By positioning the LP compressor drive shaft 12d external to the engine core as described herein above, disconnection of the LP compressor drive shaft 12d may be facilitated when it is desired or necessary to perform engine inspection or maintenance operations on a hot engine section of the engine 10. With an external LP compressor shaft 12d, the shaft 12d may simply be disconnected from one of its mechanical couplings 30, 32 and the engine 10 separated by the plane between the LP turbine 12b and the HP turbine 14b. The proposed external shaft architecture may allow for the ability to be maintained to separate the engine 10 in the turbine section while accommodating compressor boost in a compact axial tandem turbine arrangement.

[0020] Figure 1 The engine 10 shown in FIG. 1 is a "reverse flow" engine 10 because the gases flow from the air intake 13 at the rear of the engine to the exhaust 17 at the front thereof through the core gas path 11. This is different from a "through flow" gas turbine engine ( Figure 2 ) In contrast, in this "through-flow" gas turbine engine, gases flow through the core gas path 11 of the engine from the front to the rear. The direction of gas flow through the core gas path 11 of the engine 10 disclosed herein may be better understood by considering that the gases flow through the core gas path 11 in the same direction D as the direction the engine 10 travels during flight. In other words, the gases flow through the engine 10 from the rear end of the engine 10 toward the propeller 16.

[0021] Thus, it will be appreciated that the expressions "front" and "rear" as used herein refer to the relative arrangement of components of the engine 10, which correspond to the "front" and "rear" directions of the engine 10 and the aircraft including the engine 10 as defined relative to the direction of travel. In the illustrated embodiment, components of the engine 10 that are "front" of another component are arranged within the engine 10 such that they are located closer to the propeller 16. Similarly, components of the engine 10 that are "rear" of another component are arranged within the engine 10 such that they are farther away from the propeller 16.

[0022] In view of the foregoing, it can also be appreciated that the LP compressor 12a is disposed behind the LP turbine 12b. Likewise, the HP compressor 14a is disposed behind the HP turbine 14b. The LP turbine 12b and the HP turbine 14b are disposed in close proximity to one another without concentric HP and LP shafts extending therebetween. The use of an external LP compressor drive shaft 12d eliminates the need for a concentric shaft arrangement for interconnecting LP rotor components disposed on axially opposite ends of the HP rotor. This may allow for an engine separation plane to be provided between the LP turbine 12b and the HP turbine 14b. Such a modular approach facilitates engine disassembly and, therefore, facilitates access to internal engine components for inspection purposes, etc.

[0023] In operation, the LP compressor 12a pressurizes the air received from the air intake 13. The air is then directed from the LP compressor 12a to the HP compressor 14a via the core gas path 11, which is annular in the illustrated embodiment. The HP compressor 14a further pressurizes the air before the compressed air is mixed with fuel and ignited in the combustor 15. The combustion gases exhausted from the combustor 15 flow through the various stages of the HP turbine 14b, where energy is extracted to drive the HP compressor 14a and the AGB 28. The combustion gases flow from the HP turbine 14b to the LP turbine 12b via the core gas path 11, where the LP turbine 12b extracts further energy from the combustion gases to drive the LP compressor 12a and the RGB 20 and the propeller 16. The combustion gases are then exhausted from the engine 10 via the exhaust port 17.

[0024] It will be appreciated that during operation of engine 10, LP compressor 12a driven by LP turbine 12b supplies pressurized air to HP compressor 14a. Thus, the pressurized air flow produced by LP compressor 12a is provided to HP compressor 14a and contributes to the operation of both LP turbine 12b and HP turbine 14b.

[0025] It can be appreciated, therefore, that the presence of the LP rotor 12 and HP rotor 14 described above provides a "split compressor" arrangement for the engine 10. More specifically, some of the work required to compress the incoming air is transferred from the HP compressor 14a to the LP compressor 12a. In other words, some of the turbine work allocated to compression is transferred from the HP turbine 14b to the LP turbine 12b. This transfer of work can contribute to a higher pressure ratio while maintaining a relatively small number of rotors. In certain embodiments, for a given power, a higher pressure ratio allows for a higher power-to-weight ratio, better engine specific fuel consumption (SFC), and a lower combustor outlet temperature (sometimes referred to as "T4"). For the engine 10, these factors can contribute to a lower overall weight. The transfer of compression work from the HP compressor 14a to the LP compressor 12a contrasts with certain conventional reverse flow engines in which the high pressure compressor (and therefore, the high pressure turbine) performs all of the compression work.

[0026] It will therefore be appreciated that at least some embodiments of the engine 10 disclosed herein provide a mechanical architecture of the turbomachine that allows for a split compressor system and easy disassembly of the engine between the LP turbine 12b and the HP turbine 14b. This split compressor engine arrangement with an externally disposed LP compressor shaft 12d can be used for aircraft nose mounting as well as for wing mounting. It can also be used for industrial applications. The engine architecture also allows for a geared LP compressor, which can be advantageous from an aerodynamic / thermodynamic point of view. Performance gains can also result from a leaner mechanical arrangement, i.e., fewer parasitic losses associated with support bearings and drive gears.

[0027] In certain circumstances, it may be desirable to drivingly disengage the LP compressor 12a from the LP turbine 12b. In certain circumstances, it may be desirable to drivingly engage the LP compressor 12a to the HP compressor 14a. In certain circumstances, it may be desirable to allow the LP compressor 12a to free spin by drivingly disengaging the LP compressor 12a from both the LP turbine 12b and the HP compressor 14a. The engine 10 is operable in the following configurations: a first configuration in which the LP compressor 12a is drivingly disconnected from both the LP turbine 12b and the HP compressor 12b; a second configuration in which the LP compressor 12a is drivingly connected to the HP compressor 14a and drivingly disconnected from the LP turbine 12b; a third configuration in which the LP compressor 12a is drivingly connected to the LP turbine 12b and drivingly disconnected from the HP compressor 14a; and a fourth configuration in which the LP compressor 12a is drivingly connected to both the HP compressor 14a and the LP turbine 12b. Operating the engine 10 in a fourth configuration, also referred to as a single rotor configuration, allows the engine 10 to be operated as a single rotor engine because all rotating components, namely the LP compressor 12a, the HP compressor 14a, the HP turbine 14b, and the LP turbine 12b, rotate at substantially the same rotational speed. In both the first and second configurations, the LP turbine 12b is a free power turbine and can only drive a rotatable load (e.g., the propeller 16). In other words, in both the first and second configurations, the engine 10 operates in a free power turbine mode. In the third configuration, the engine 10 operates in a supercharged mode. In the illustrated embodiment, the low pressure turbine 12b is drivingly connected to the output shaft 18 of the engine 10 in all of the first, second, third, and fourth configurations.

[0028] In the illustrated embodiment, the engine 10 includes a clutch system CS. The clutch system CS may include two clutches, namely a first clutch 40 and a second clutch 42. Both the first clutch 40 and the second clutch 42 may be any suitable type of clutch known in the art. It is to be understood that the configuration of the engine 10 using only one of the two clutches 40, 42 is contemplated.

[0029] In the depicted embodiment, the first clutch 40 is located on the LP compressor drive shaft 12d, and the second clutch 42 is axially located between the LP compressor 12a and the HP compressor 14a relative to the engine centerline CL. The first clutch 40 is operable in an engaged configuration, in which the LP compressor 12a is drivingly connected to the LP turbine 12b via the LP compressor drive shaft 12d, and a disengaged configuration, in which the LP compressor 12a is drivingly disconnected from the LP turbine 12b. The second clutch 42 is operable in an engaged configuration, in which the LP compressor 12a is drivingly connected to the HP compressor 14a via the HP shaft 14c, and a disengaged configuration, in which the LP compressor 12a is drivingly disconnected from the HP compressor 14a. It will be appreciated that in the illustrated embodiment, both the first clutch 40 and the second clutch 42 may be in an engaged configuration at the same time. Both the first clutch 40 and the second clutch 42 may be in a disengaged configuration at the same time.

[0030] The engine 10 may be in a first configuration by having both the first clutch 40 and the second clutch 42 in their disengaged configurations. The engine 10 may be in a second configuration by having the first clutch 40 in a disengaged configuration and the second clutch 42 in an engaged configuration. The engine 10 may be in a third configuration by having the first clutch 40 in an engaged configuration and the second clutch 42 in a disengaged configuration. The engine 10 may be in a fourth configuration by having both the first clutch 40 and the second clutch 42 in their engaged configurations.

[0031] In other words, the engine 10 may have two clutches 40, 42. The first clutch 40 is operable to couple the LP compressor 12a to the LP drive shaft 12d, and the second clutch 42 is operable to couple the LP compressor 12a to the HP shaft 14c. The intended operating mode is to have the clutch systems 40, 42 exclusively engaged, or no clutch engaged. If the first clutch 40 is engaged, i.e., the LP turbine 12b is coupled to the LP compressor 12a, a supercharged engine type may be achieved. If the second clutch 42 is engaged, i.e., the LP compressor 12a is coupled to the HP compressor 14a, or if neither of the clutch systems 40, 42 is engaged, a free power turbine engine may be achieved. In other words, a free power turbine configuration is achieved by having the first clutch 40 in a disengaged configuration.

[0032] Disengaging the first clutch 40 to separate the LP compressor 12a from the LP turbine 12b may be beneficial in low output power conditions, such as ground idle / coasting mode, where the LP drive shaft 12d is running at a low rotational speed or may not be rotating. Disengaging the first clutch 40 and engaging the second clutch 42 may allow the LP compressor 12a to run faster than if the second clutch 42 was in a disengaged configuration. Having the second clutch 42 in an engaged configuration and the first clutch 40 in a disengaged configuration may help maintain a higher pressure ratio engine at low output power, which may be desirable for an emissions system of an environmental control system (ECS). Higher compressor work may mean a greater temperature drop across the HP turbine 12b, which may result in a lower temperature at the inlet of the LP turbine 12b, which in turn may result in higher durability.

[0033] In the air idle mode, it may be desirable in certain conditions to operate an aircraft equipped with the engine 10 so as to keep the propeller 16 running at 100% speed. However, if the engine is operated in a supercharged engine mode, the LP shaft 12d may have a fixed rotational speed, which may increase risks to compressor stability and operability. These risks may be reduced using the option of transferring the mechanical coupling of the LP compressor 12a from the LP shaft 12d to the HP shaft 14c, which may have a variable, self-regulating rotational speed. In other words, these risks may be mitigated by having the LP compressor 12a drivingly disconnected from the LP turbine 12b and drivingly connected to the HP compressor 14a.

[0034] Having the ability to drivingly engage the LP compressor 12a and the HP compressor 14a together may allow the engine to have the ability to vary the number of compressor stages drivingly connected to the HP turbine 14b. The arrangement of the two clutches 40, 42 may allow the engine to switch from a free power turbine to a boost configuration.

[0035] It is to be understood that the engine 10 may include only the first clutch 40 to selectively engage or disengage the LP compressor 12a from the LP turbine 12b. Alternatively, the engine 10 may include only the second clutch 42 to selectively engage or disengage the LP compressor 12a from the HP compressor 14a.

[0036] Reference now Figure 2, a gas turbine engine in a through-flow configuration is generally shown at 100. The through-flow configuration corresponds to an engine in which gas flows from a front end 100a of the engine 100 to a rear end 100b thereof through a core gas path 11. In this document, "front" and "rear" are used relative to the flight direction of the engine 100, which is depicted by arrow D. The direction of airflow through the engine 100 is depicted by arrow A. For the sake of brevity, only the above reference to the engine 100 is described below. Figure 1 The engine 10 is described with different components.

[0037] In the illustrated embodiment, the engine 100 includes a low pressure shaft 120d and a high pressure shaft 14c. Here, both the low pressure shaft 120d and the high pressure shaft 14c are located radially inward of the core gas path 11 relative to the engine centerline CL of the engine 100. In the illustrated embodiment, the low pressure shaft 120d and the high pressure shaft 14c are concentric. The high pressure shaft 120d may be located radially inward of the high pressure shaft 14c relative to the centerline CL. It will be appreciated that the through-flow configuration 100 may implement an external shaft, such as described above with reference to Figure 1 The shaft 12d.

[0038] In this embodiment, the clutch system CS has two clutches, namely, a first clutch 140 and a second clutch 142. Figure 2 As shown in FIG. 1 , both the first clutch 140 and the second clutch 142 are located axially between the LP compressor 12a and the HP compressor 14a relative to the centerline CL. The first clutch 140 is located forward of the second clutch 142. However, other configurations are also contemplated.

[0039] The first clutch 140 is operable in an engaged configuration, in which the LP turbine 12b is drivingly engaged with the LP compressor 12a via the LP shaft 120d, and in a disengaged configuration, in which the LP compressor 12a is drivingly disconnected from the HP pressure turbine 12b. The second clutch 142 is operable in an engaged configuration, in which the LP compressor 12a is drivingly engaged with the HP compressor 14a via the HP shaft 14c, and in a disengaged configuration, in which the LP compressor 12a is drivingly disconnected from the HP compressor 14a.

[0040] It is important to understand that Figure 1-2 Both engines 10, 100 may be operated as shown in the drawings, i.e., by having the propeller 16 in front of the rest of the engine with respect to the direction of travel depicted by arrow D. Alternatively, Figure 1-2Both engines 10, 100 may be operated in a "thruster" configuration, wherein the propeller 16 is located behind the rest of the engine 10, 100 relative to the direction of travel D. This may be achieved by rotating the engine 10, 100 180 degrees so that Figure 1 The engine 10 becomes a through-flow engine, and makes Figure 2 The engine 100 becomes a reverse flow engine. It is to be understood that this reversal of the engine will require some modifications.

[0041] The disclosed engines 10, 100 are capable of operating in both a supercharged configuration and an unsupercharged configuration. As explained herein above, the supercharged configuration corresponds to a configuration in which the LP turbine 12b drivingly engages the LP compressor 12a, and the unsupercharged configuration corresponds to a configuration in which the LP turbine is free. The disclosed engines 10, 100 are capable of allowing a variable work-split between the stages of the compressor section of the engine by selectively coupling or decoupling the LP compressor 12a and the HP compressor 14a.

[0042] To operate the engine, a power request is received; while keeping the low-pressure turbine 12b drivingly connected to the output shaft 18, if the power request is below a power threshold, the gas turbine engine 10, 100 is set to a free turbine configuration by disengaging the low-pressure compressor 12a from the low-pressure turbine 12b; and while keeping the low-pressure turbine 12b drivingly connected to the output shaft 18, if the power request is below a power threshold, the gas turbine engine 10, 100 is set to a supercharged configuration by engaging the low-pressure compressor 12a to the low-pressure turbine 12b. Setting the engine 10, 100 to the free turbine configuration and the supercharged configuration can be accomplished based on the power request and the rotational speed of the propeller.

[0043] In some cases, while maintaining the low-pressure turbine 12b drivingly connected to the output shaft 18, if the power request is below the power threshold, the low-pressure compressor 12a is engaged to the high-pressure compressor 14a. This can be done based on the power request and the rotational speed of the propeller. In the disclosed embodiment, drivingly engaging the low-pressure compressor 12a to the high-pressure compressor 14a includes setting the second clutch 42 to an engaged configuration, the second clutch 42 is operatively connected to the high-pressure shaft 14c, and the high-pressure shaft 14c drives the high-pressure compressor 14a to the high-pressure turbine 14b. In the illustrated embodiment, setting the gas turbine engine 10, 100 to a free turbine configuration includes setting the first clutch 40 to a disengaged configuration, wherein the low-pressure turbine 12b is drivingly disconnected from the low-pressure compressor 12a. In the illustrated embodiment, setting the gas turbine engine 10, 100 to a supercharged configuration includes setting the first clutch 40 to an engaged configuration, wherein the low-pressure turbine 12b is drivingly connected to the low-pressure compressor 12a.

[0044] Embodiments disclosed herein include:

[0045] A. A gas turbine engine, comprising: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in serial flow communication; and a clutch having a disengaged configuration and an engaged configuration, in which the low-pressure turbine is drivingly disconnected from the low-pressure compressor, so that in the disengaged configuration the clutch disengages the low-pressure turbine from the low-pressure compressor, in the engaged configuration the low-pressure turbine is drivingly connected to the low-pressure compressor, and in both the engaged and disengaged configurations of the clutch the low-pressure turbine is drivingly connected to the output shaft;

[0046] B. A gas turbine engine comprising: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in series flow communication; and a system for selectively engaging the low-pressure compressor to one or both of the high-pressure compressor and the low-pressure turbine.

[0047] Embodiments A and B may include any of the following elements in any combination:

[0048] Element 1: A second clutch having a second engaged configuration and a second disengaged configuration, in which the low-pressure compressor is drivingly connected to the high-pressure compressor and in which the high-pressure compressor is drivingly disconnected from the low-pressure compressor. Element 2: The gas turbine engine is operable in a single-rotor configuration, in which the low-pressure turbine is drivingly connected to the low-pressure compressor via the clutch in the engaged configuration, and in which the low-pressure compressor is drivingly connected to the high-pressure compressor via the second clutch in the second engaged configuration. Element 3: Having a low-pressure shaft for drivingly engaging the low-pressure compressor to the low-pressure turbine, the clutch being operatively connected to the low-pressure shaft. Element 4: The low-pressure shaft is offset from a core gas path of the engine core relative to a centerline of the gas turbine engine. Element 5: The gas turbine engine is a reverse flow gas turbine engine. Element 6: The low-pressure shaft is concentric with the high-pressure shaft, the high-pressure shaft drivingly connecting the high-pressure compressor to the high-pressure turbine. Element 7: A low-pressure shaft for drivingly engaging the low-pressure compressor to the low-pressure turbine, the clutch being operatively connected to the low-pressure shaft, and wherein the high-pressure compressor is drivingly engaged with the high-pressure shaft, and the second clutch being operatively connected to the high-pressure shaft. Element 8: The system includes a first clutch and a second clutch, the first clutch being operable to selectively engage the low-pressure compressor to the low-pressure turbine, and the second clutch being operable to selectively engage the low-pressure compressor to the high-pressure compressor. Element 9: The first clutch and the second clutch are operable simultaneously in an engaged configuration to engage the low-pressure compressor to both the low-pressure turbine and the high-pressure compressor. Element 10: The low-pressure compressor is selectively drivingly connected to the low-pressure turbine via a low-pressure shaft, the first clutch being operatively connected to the low-pressure shaft, and wherein the high-pressure compressor is drivingly engaged with the high-pressure shaft, and the second clutch being operatively connected to the high-pressure shaft. Element 11: The low-pressure shaft is offset from the core gas path of the engine core relative to a centerline of the gas turbine engine. Element 12: The low-pressure shaft is concentric with the high-pressure shaft. Element 13: The gas turbine engine is a turboshaft or turboprop reverse flow engine.

[0049] The embodiments described herein provide non-limiting examples of possible implementations of the present technology. After reviewing this disclosure, one of ordinary skill in the art will recognize that the embodiments described herein may be changed without departing from the scope of the present technology. In view of this disclosure, one of ordinary skill in the art may implement further modifications that will fall within the scope of the present technology.

Claims

1. A gas turbine engine, comprising: an engine core having in serial flow communication a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft; a first clutch having a first disengaged configuration and a first engaged configuration, in which the low-pressure turbine is drivingly disconnected from the low-pressure compressor, such that in the first disengaged configuration, the first clutch disengages the low-pressure turbine from the low-pressure compressor, in which the low-pressure turbine is drivingly connected to the low-pressure compressor, and in both the first engaged configuration and the first disengaged configuration of the first clutch, the low-pressure turbine is drivingly connected to the output shaft; as well as The second clutch has a second engagement structure and a second disengagement structure. In the second engagement structure, the low-pressure compressor is drivingly connected to the high-pressure compressor. In the second disengagement structure, the high-pressure compressor is drivingly disconnected from the low-pressure compressor.

2. The gas turbine engine according to claim 1, wherein: The gas turbine engine is capable of operating in a single-rotor configuration, in which the low-pressure turbine is drivingly connected to the low-pressure compressor via the first clutch in the first engagement configuration, and in the single-rotor configuration, the low-pressure compressor is drivingly connected to the high-pressure compressor via the second clutch in the second engagement configuration.

3. The gas turbine engine of claim 1, having a low-pressure shaft for drivingly engaging the low-pressure compressor to the low-pressure turbine, the first clutch being operatively connected to the low-pressure shaft.

4. The gas turbine engine according to claim 3, wherein: The low pressure shaft is offset from a core gas path direction of the engine core relative to a centerline of the gas turbine engine.

5. The gas turbine engine according to claim 4, wherein: The gas turbine engine is a reverse flow gas turbine engine.

6. The gas turbine engine according to claim 3, wherein: The low-pressure shaft is concentric with a high-pressure shaft, and the high-pressure shaft drivingly connects the high-pressure compressor to the high-pressure turbine.

7. The gas turbine engine according to claim 1, having a low-pressure shaft for drivingly engaging the low-pressure compressor to the low-pressure turbine, the first clutch being operatively connected to the low-pressure shaft, and wherein: The high-pressure compressor is in driving engagement with a high-pressure shaft, and the second clutch is operatively connected to the high-pressure shaft.

8. A gas turbine engine comprising: an engine core having a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor, and a low-pressure turbine drivingly connected to an output shaft in series flow communication; a system for selectively engaging the low-pressure compressor to one or both of the high-pressure compressor and the low-pressure turbine, Therein, the system includes a first clutch and a second clutch, the first clutch being operable to selectively engage the low-pressure compressor to the low-pressure turbine, and the second clutch being operable to selectively engage the low-pressure compressor to the high-pressure compressor.

9. The gas turbine engine according to claim 8, wherein: The first clutch and the second clutch are simultaneously operable in an engaged configuration to engage the low-pressure compressor to both the low-pressure turbine and the high-pressure compressor.

10. The gas turbine engine according to claim 8, wherein: The low-pressure compressor is selectively drivingly connected to the low-pressure turbine via a low-pressure shaft, the first clutch is operatively connected to the low-pressure shaft, and wherein the high-pressure compressor is drivingly engaged with a high-pressure shaft, the second clutch is operatively connected to the high-pressure shaft.

11. The gas turbine engine according to claim 10, wherein: The low pressure shaft is offset from a core gas path direction of the engine core relative to a centerline of the gas turbine engine.

12. The gas turbine engine according to claim 10, wherein: The low-pressure shaft is concentric with the high-pressure shaft.

13. The gas turbine engine according to claim 8, wherein: The gas turbine engine is a turboshaft or turboprop reverse flow engine.

14. A method for a gas turbine engine having a low pressure compressor, a high pressure compressor, a high pressure turbine drivingly engaged with the high pressure compressor, and a low pressure turbine drivingly connected to an output shaft, the method comprising: receiving a power request; placing the gas turbine engine in a free turbine configuration by decoupling the low-pressure compressor from the low-pressure turbine if the power request is below a power threshold while maintaining the low-pressure turbine drivingly connected to the output shaft; while maintaining the low-pressure turbine drivingly connected to the output shaft, placing the gas turbine engine in a boost configuration by engaging the low-pressure compressor to the low-pressure turbine if the power request is above the power threshold; and While maintaining the low-pressure turbine drivingly connected to the output shaft, the low-pressure compressor drivingly engages the high-pressure compressor if the power request is below the power threshold.

15. The method according to claim 14, wherein: The gas turbine engine has: a low-pressure shaft for drivingly coupling the low-pressure turbine to the low-pressure compressor; and a first clutch operatively connected to the low-pressure shaft, and wherein placing the gas turbine engine into the free turbine configuration includes placing the first clutch into a disengaged configuration in which the low-pressure turbine is drivingly disconnected from the low-pressure compressor.

16. The method according to claim 14, wherein: The gas turbine engine comprises: a low-pressure shaft for drivingly engaging the low-pressure turbine to the low-pressure compressor; and a first clutch operatively connected to the low-pressure shaft, and wherein setting the gas turbine engine to the boost configuration comprises setting the first clutch to an engaged configuration in which the low-pressure turbine is drivingly connected to the low-pressure compressor.

17. The method according to claim 14, wherein: Drivingly engaging the low-pressure compressor to the high-pressure compressor includes placing a second clutch in an engaged configuration, the second clutch operatively connected to a high-pressure shaft drivingly engaging the high-pressure compressor to the high-pressure turbine.

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