Improved hybrid turboprop engine for aircraft

Abstract

The present disclosure relates to a hybrid turboprop engine (100) for an aircraft, comprising: a gas generator (12) carried by a generator shaft (14); a free turbine (11) carried by a turbine shaft (13) and rotationally driven by the gas flow generated by the gas generator (12), the turbine shaft (13) being engaged with the main rotor (60) by a transmission unit (50), the transmission unit (50) comprising a first free wheel (51) oriented such that the main rotor (60) cannot drive the free turbine (11); and a reversible electric machine (30) engageable with the main rotor (60) via the transmission unit (50) to drive the main rotor (60) during an electric or hybrid mode of operation, the hybrid turboprop engine (100) comprising: a single oil pump (40) engageable with the transmission unit (50) to be selectively driven by the turbine shaft (13) or the electric machine (30) according to the mode of operation.

Description

Field of the Invention

[0001] The present invention relates to the field of hybrid aircraft, including turboprop engines for propeller aircraft. Specifically, the present invention relates to a hybrid turboprop engine for an aircraft, and a hybrid aircraft including such a turboprop engine. Background Art

[0002] As is well known, an aircraft turboprop engine includes a gas turbine having a gas generator and a free turbine, and the free turbine is driven to rotate by a gas flow generated by the gas generator. In addition, in a hybrid aircraft, a turboprop engine typically includes an electric motor coupled to a propeller to ensure all-electric (i.e., 100% electric) or hybrid operation. "Hybrid" or "parallel hybrid" in particular means that the power source driving the propulsion propeller can be a turbine engine, an electric motor, or a combination of both, depending on the required operating mode.

[0003] Traditionally, the gas generator includes at least one compressor and a rotatably coupled turbine. The working principle is as follows: Fresh air entering the gas turbine is compressed due to the rotation of the compressor before being fed into the combustion chamber, and is mixed with fuel in the combustion chamber. The combustion gas generated by combustion is then discharged at high speed. Then, the first expansion occurs in the gas generator turbine, during which the gas generator turbine extracts the energy required to drive the compressor. The gas generator turbine does not absorb all the kinetic energy of the combustion gas, and the excess kinetic energy corresponds to the gas flow generated by the gas generator. Therefore, the gas generator supplies kinetic energy to the free turbine, so that the second expansion occurs in the free turbine, and the free turbine converts this kinetic energy into mechanical energy to drive a receiving component, such as the propeller of a turboprop engine.

[0004] In addition, in a conventional turboprop engine, a separate transmission unit is usually used, in particular a power gearbox known by the abbreviation "PGB" and an accessory gearbox known by the abbreviation "AGB". The power gearbox allows power to be transmitted from the free turbine to the propeller, and the accessory gearbox allows power to be transmitted from the gas generator to the accessories.

[0005] The structures in which these "free turbine" shafts and "gas generator" shafts are decoupled and not engaged with each other cannot achieve electric, thermal, or hybrid propulsion while optimally meeting safety requirements, and from a functional perspective, cannot fully exploit the potential of introducing high hybrid power. In addition, in these turboprop engine structures, the layout of the components dedicated to lubrication and the mass of the components are not ideal.

[0006] Therefore, an improved structure is needed to solve at least some of the above disadvantages. Summary of the Invention

[0007] The present disclosure relates to a hybrid turboprop engine for an aircraft. The turboprop engine includes: a gas generator carried by a generator bearing; a free turbine carried by a turbine bearing and rotationally driven by a gas flow generated by the gas generator, the turbine shaft being engaged with a main rotor through a transmission unit including a first freewheel, the first freewheel being oriented such that the main rotor cannot drive the free turbine; a reversible electric machine capable of being engaged with the main rotor through the transmission unit to drive the main rotor during electric or hybrid operation modes. The hybrid turboprop engine includes: a single oil pump engaged with the transmission unit to be selectively driven by the turbine shaft or the electric machine according to the operation mode of the hybrid turboprop engine.

[0008] In the present disclosure, a "freewheel" refers to a device including a hub and a peripheral gear ring rotatably mounted on the hub. The hub can drive the peripheral gear ring to rotate, but not vice versa. In addition, the hub only drives the gear ring when rotating in a predetermined direction (referred to as the "engagement direction"). Otherwise, the hub and the peripheral gear ring rotate freely with respect to each other. In this case, when the hub of the freewheel drives the peripheral gear ring to rotate, the freewheel is activated; conversely, when the hub of the freewheel does not drive the peripheral gear ring to rotate, the freewheel is deactivated. One advantage of the freewheel is that it does not require electronic or mechanical control by an external operator.

[0009] The main rotor may include a propeller of an aircraft (especially an airplane) for propelling the aircraft, the propeller being provided at one end of the turboprop engine, and preferably provided at the front end of the turboprop engine when considering the normal moving direction of the aircraft. Thus, the main rotor is capable of moving about a rotation axis, which may correspond to the main axis of the turboprop engine or be radially offset with respect to the main axis.

[0010] In addition, "being engaged with" means that one component is directly or indirectly mechanically coupled to another component. In the present disclosure, in particular, the end of the turbine shaft is indirectly mechanically coupled to the main rotor through the transmission unit.

[0011] When operating in the electric machine mode, the reversible electric machine provides propulsion energy to the main rotor. In particular, this configuration allows for: full thermal (100% thermal) operation, where the free turbine drives the main rotor through the transmission unit; full electric (100% electric) operation, where on the ground or in flight, the reversible electric machine drives the main rotor through the transmission unit; and hybrid operation, where the main rotor is driven by both the reversible electric machine and the free turbine.

[0012] Furthermore, according to this configuration, an oil pump for circulating lubricating oil for various bearings of a turboprop engine is engaged with the transmission unit, and thus can be selectively driven by the turbine shaft in the case of 100% thermal or hybrid operation, or can be driven by an electric motor in the case of 100% electric or hybrid operation.

[0013] Therefore, this configuration allows the use of a single oil pump that can lubricate the bearings of the transmission unit and the bearings of the accessory gearbox engaged with the generator shaft. In other words, the source (electric motor and / or turbine shaft) for driving the single oil pump can be selected according to the operating mode, enabling the components dedicated to lubrication to be optimized, thereby limiting the mass of the assembly and improving the reliability of the device.

[0014] In some embodiments, the electric motor is engaged with the main rotor through a second freewheel of the transmission unit, and the second freewheel is oriented such that the main rotor cannot drive the electric motor.

[0015] In other words, the second freewheel allows the main rotor (especially the propeller) to be driven by the electric motor, but not vice versa. Therefore, according to this configuration, freewheels (the first freewheel and the second freewheel) are provided between each power source (the free turbine and the electric motor) and the main rotor as the sole receiver. Thus, the power sources (thermal and / or electric) can be selected independently of each other.

[0016] In some embodiments, the electric motor can be engaged with the main rotor through a reversible coupling device that can move between a coupling position and a decoupling position. In the coupling position, the electric motor can drive the main rotor during operation in the motor mode, or be driven by the main rotor or the free turbine during operation in the generator mode. In the decoupling position, the electric motor is decoupled from the main rotor.

[0017] Different from the freewheel that only allows power to be transmitted from the electric motor to the main rotor direction, the coupling device, when activated (i.e., in the coupling position), allows the electric motor and the main rotor to be mechanically coupled through the transmission unit, so that the electric motor can drive the main rotor and vice versa. Furthermore, during 100% thermal operation, the coupling device in the decoupling position can prevent the free turbine from driving the electric motor.

[0018] This configuration can increase the number of functional modes that this structure can achieve. In particular, in addition to the 100% electric or hybrid operation mode during which the reversible electric motor operates in the motor mode, the reversible electric motor can be driven by the main rotor or the free turbine during operation in the generator mode to generate electricity, so as to supply electricity to various aircraft equipment or charge a high-voltage battery.

[0019] This power generation can be carried out during flight or on the ground. Then, the electric machine is driven by a free turbine, in other words, by a thermal engine that also drives the main rotor. Additionally, this power generation can also be carried out during an operating mode referred to as the "wind turbine" operating mode, in which the main rotor (such as a propeller) is driven to rotate by the forward movement of the aircraft and drives the electric machine.

[0020] In some embodiments, the reversible coupling device is a clutch. The advantage of a clutch is that it can be remotely controlled, for example, by a monitoring unit, and in particular, it can be moved from the coupled position to the decoupled position at any time during flight. The turboprop engine can include: synchronization means for effecting the transition from the coupled position to the decoupled position.

[0021] In some embodiments, the hybrid turboprop engine includes a coupling shaft having a first end engaged with the transmission unit and a second end engaged with the generator shaft. The second end can be engaged with the generator shaft through gears of an accessory gearbox.

[0022] Different from the configuration of a conventional turboprop engine that is separated from the free turbine and the gas generator, the coupling shaft physically connects the generator shaft to the transmission unit (and thus to the turbine shaft) through the transmission unit. It should be noted that the coupling shaft is preferably flexible to compensate for the alignment deviations of these various components.

[0023] Therefore, it can be understood that this configuration allows the electric machine to drive the generator shaft through the coupling shaft, thereby driving the gas generator. Thus, a reversible electric machine can be used to start the gas generator. This configuration eliminates the need for a starter that is typically required during the start-up phase of the gas generator. In other words, according to this embodiment, the turboprop engine includes a single electric machine, which can reduce the weight of the device and simplify the device. This reversible electric machine is a high-power electric machine, so it can be used in the electric machine mode to drive the main rotor and also to start the gas generator.

[0024] "High power" means that: in order to perform these functions, the electric machine must be sized to have a power far higher than that of a commonly used generator / starter, typically one hundred kilowatts or several hundred kilowatts, rather than about ten kilowatts.

[0025] Furthermore, this structure allows an operating mode in which the main rotor is blocked and the gas generator operates alone to drive the accessories connected to it. In fact, the coupling shaft engaged with the electric machine and the transmission unit allows: driving an oil pump engaged with the transmission unit without the need for a second oil pump coupled to the gas generator, thus being able to optimize the components for lubrication and limit the mass of the device.

[0026] In some embodiments, the coupling shaft includes a coupling freewheel oriented such that the gas generator cannot drive the electric machine.

[0027] Although the presence of the coupling freewheel on the coupling shaft does not enable a functional mode in which the main rotor is blocked and the gas generator drives alone the accessories coupled thereto (since the gas generator cannot drive the oil pump due to the presence of the freewheel), this coupling freewheel can prevent the gas generator from driving the electric machine when it is not required to do so (in particular after the start-up phase or during 100% thermal or hybrid operation).

[0028] In particular, during the start-up phase of a reversible electric machine, when the gas generator reaches an autonomous operating state (about 50% of its rated speed), its rotational speed becomes higher than that of the electric machine, and the freewheel prevents the generator shaft from driving the electric machine. It should also be noted that during the phase started by the electric machine, the reversible coupling device (such as a clutch) is in a decoupled position so that the electric machine is fully used to start the gas generator. The oil pump is driven by the turbine shaft during start-up.

[0029] In some embodiments, the second end of the coupling shaft is engaged with the generator shaft through a safety disconnect device configured to allow the coupling shaft to disconnect from the generator shaft in the event of a partial or complete blockage of the gas generator.

[0030] The safety disconnect device arranged between the coupling freewheel and the gas generator can avoid the following situation by disconnecting the coupling shaft and the generator shaft: the rotation of the main rotor driven by the electric machine operating in electric machine mode is hindered by the resistance generated by a partially or completely blocked gas generator. Thus, the electric machine can perform its function of driving the main rotor in the event of an engine failure, which can improve the safety of the device. The safety disconnect device can be an active system or a passive system, such as a weakening part.

[0031] In some embodiments, the hybrid turboprop engine includes a coupling shaft having a first end engaged with the transmission unit and a second end engaged with the generator shaft. The coupling shaft includes a coupling freewheel oriented such that the gas generator cannot drive the electric machine. The second freewheel is configured to be activated when the electric machine rotates in a first rotational direction, and the coupling freewheel is configured to be activated when the electric machine rotates in a second rotational direction opposite to the first rotational direction.

[0032] According to this embodiment, the reversible motor is engaged with the transmission unit through the second overrunning clutch and connected to the gas generator through the coupling overrunning clutch. It can be understood that the second overrunning clutch and the coupling overrunning clutch are installed in opposite ways. "Installed in opposite ways" is understood as: the second overrunning clutch can transmit the rotational torque from the motor to the main rotor, but not vice versa, while the coupling overrunning clutch can transmit the rotational torque from the motor to the gas generator, but not vice versa.

[0033] In addition, according to this embodiment, the reversible motor can be used to mechanically couple with the gas generator in one rotational direction (e.g., clockwise direction) (at this time the motor is decoupled from the main rotor), and used to mechanically couple with the main rotor in the other rotational direction (e.g., counterclockwise direction) (at this time the motor is decoupled from the gas generator).

[0034] Specifically, the motor rotating in the second rotational direction allows coupling with the gas generator to start the gas generator on the ground. In addition, the motor rotating in the first rotational direction allows operation in the 100% electric or hybrid motor mode.

[0035] This configuration eliminates the need for a reversible coupling device such as a clutch, which is a complex device. Instead, the advantage of the overrunning clutch is that it does not require electronic or mechanical control by an external operator. The overrunning clutch also has significant reliability. Although this configuration does not allow the motor to be used in the generator mode, it still improves the simplicity and reliability of the device, and there is no longer a need to use a safety disconnect device (such as a weakening part) as described above.

[0036] In some embodiments, the reversible coupling device is a first reversible coupling device, and the second end of the coupling shaft is engaged with the generator shaft through a second reversible coupling device, and the second reversible coupling device can move between a coupling position and a decoupling position. In the coupling position, the motor and the gas generator are coupled, and in the decoupling position, the motor and the gas generator are decoupled.

[0037] The first reversible coupling device and the second reversible coupling device can be, for example, clutches remotely controlled by a monitoring unit. Therefore, the position of the clutch can be controlled according to the operating stage of the turboprop engine. For example, in the start-up stage, the first coupling device (the first clutch) is placed in the decoupling position, and the second coupling device (the second clutch) is placed in the coupling position. On the contrary, during 100% electric or hybrid operation, the first clutch is placed in the coupling position, and the second clutch is placed in the decoupling position.

[0038] This configuration enables a large number of functions to be performed, such as generating electricity by the motor by placing the first clutch in the coupling position, or driving an oil pump by the gas generator through the coupling shaft by placing the coupling overrunning clutch in the coupling position.

[0039] In some embodiments, the generator shaft is engaged with an accessory gearbox different from the transmission unit, and the second end of the coupling shaft is engaged with the accessory gearbox.

[0040] The present disclosure also relates to an aircraft comprising a hybrid turboprop engine according to any one of the foregoing embodiments, the aircraft being a propeller aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention and its advantages will be better understood by reading the following detailed description of different embodiments of the invention given as non - limiting examples. The description refers to the accompanying drawings, in which: Figure 1 shows a cross - sectional view of a turboprop engine for a hybrid aircraft according to the invention, Figure 2 schematically represents Figure 1 the turboprop engine according to the first embodiment, Figure 3 schematically represents Figure 1 the turboprop engine according to the second embodiment, Figure 4 schematically represents Figure 1 the turboprop engine according to the third embodiment, Figure 5 schematically represents a detailed view of the turboprop engine according to the third embodiment, Figure 6 schematically represents Figure 1 the turboprop engine according to the fourth embodiment, Figure 7 schematically represents Figure 1 the turboprop engine according to the fifth embodiment, Figure 8A and Figure 8B schematically represent respectively Figure 1 the turboprop engines in the first operating mode according to the third and fourth embodiments, Figure 9A and Figure 9B schematically represent respectively Figure 1 the turboprop engines in the second operating mode according to the third and fourth embodiments, Figure 10A and Figure 10B schematically represent respectively Figure 1 the turboprop engines in the third operating mode according to the third and fourth embodiments, Figure 11A and Figure 11BSchematically showing respectively the fourth operating mode according to the third and fourth embodiments Figure 1 of a turboprop engine, Figure 12 Schematically showing the fifth operating mode according to the third embodiment Figure 1 of a turboprop engine, Figure 13 Schematically showing the sixth operating mode according to the third embodiment Figure 1 of a turboprop engine. Detailed implementation

[0042] In the remaining part of the description, reference will be made to Figures 1 to 13 to describe the structure of the turboprop engine 100 according to different embodiments of the present invention.

[0043] Figure 1 Schematically showing the turboprop engine 100 of an aircraft, which drives the main rotor 60 of the aircraft to rotate, and the main rotor includes a rotor shaft 61 carrying a propeller 62. The turboprop engine 100 includes a gas turbine 10, and the gas turbine 10 has a gas generator 12 and a free turbine 11, and the free turbine 11 can be driven to rotate by the gas flow generated by the gas generator 12.

[0044] The free turbine 11 is mounted on a turbine shaft 13, and the turbine shaft 13 transmits a rotational motion to the main rotor 60 through a transmission unit 50. One end of the turbine shaft 13 engages with the transmission unit 50, and the other end faces the following generator shaft 14 by being decoupled from the generator shaft 14.

[0045] The gas generator 12 includes a rotating generator shaft 14 and a combustion chamber 17. At least one centrifugal compressor 15 and at least one turbine 16 are mounted on the generator shaft 14. When considering the gas generator 12 in the axial direction of the generator shaft 14, the combustion chamber 17 is axially arranged between the compressor 15 and the turbine 16. The gas turbine 10 has a housing 18, and the housing 18 is provided with an air inlet 19, and fresh air enters the gas generator 12 through the air inlet 19. The fresh air is compressed by the compressor 15 after entering the housing of the gas generator 12, and the compressor 15 discharges the fresh air to the inlet of the combustion chamber 17. In the combustion chamber 17, the fresh air is mixed with fuel. The combustion occurring in the combustion chamber 17 causes the combustion gas to be discharged to the turbine 16 at high speed, which has the effect of driving the shaft 14 of the gas generator 12 to rotate, and thus driving the compressor 15 to rotate. The rotational speed of the shaft 14 of the gas generator 12 is determined by the fuel flow rate entering the combustion chamber 17.

[0046] Although the turbine 16 extracts kinetic energy, the gas flow leaving the gas generator 12 still has significant kinetic energy. From Figure 1It can be understood that the gas flow F is directed to the free turbine 11, which causes expansion in the free turbine 11, thereby causing the turbine impeller and the turbine shaft 13 to rotate.

[0047] A reversible electric machine 30 (hereinafter simply referred to as "machine 30") is engaged with the transmission unit 50 and includes an electric motor capable of operating reversibly as a generator. Thus, according to the embodiments described below, the machine 30 can supply power to the main rotor 60 by operating in motor mode, or can obtain mechanical power from the main rotor 60 by operating in generator mode. The machine 30 is a high-power electric machine (one hundred to several hundred kilowatts).

[0048] The rear part of the turboprop engine 100 (i.e., the upstream part including the air inlet 19) includes: an accessory gearbox 20 (known abbreviation "AGB") engaged with the generator shaft 14. Depending on the application selected, this accessory gearbox 20 includes different devices.

[0049] The turboprop engine 100 also includes a single oil pump 40, which is engaged with the transmission unit 50, so the oil pump 40 can be driven by the turbine shaft 13 and / or the machine 30.

[0050] It should be noted that in Figure 1 the example shown, all the devices (in particular the gas generator 12, the free turbine 11, the transmission unit 50 and the main rotor 60) are coaxial and centered on the same main axis X. However, this arrangement is not restrictive, and the present invention is applicable to configurations where the rotor shaft 61 is radially offset with respect to the main axis X of the turboprop engine, as shown later in the description Figure 5 as shown.

[0051] The following describes different embodiments with reference to Figures 2 to 13 to.

[0052] Generally, it should be noted that, for clarity, the following figures schematically represent the different operating modes of the device in a functional and simplified manner, without showing all the details of the elements constituting the turboprop engine 100 and the different power transmission components. In particular, the pinions and possible speed ratios are not shown.

[0053] Figure 2 Shows the structure according to the first embodiment, in which the turbine shaft 13 is engaged with the main rotor 60 through the first freewheel 51 of the transmission unit 50.

[0054] The first overrunning clutch 51 is installed such that when the turboprop engine operates in the 100% thermal or hybrid mode, the rotation of the turbine shaft 13 can drive the main rotor 60 to rotate (the first overrunning clutch 51 is activated), but conversely, the rotation of the main rotor 60 cannot drive the turbine shaft 13 to rotate (the first overrunning clutch 51 is deactivated). In other words, the first overrunning clutch 51 can only transmit rotational torque in the direction of the turbine shaft 13 towards the main rotor 60, and cannot transmit it in the opposite direction.

[0055] In addition, according to this embodiment, the electric machine 30 is engaged with the main rotor 60 through the second overrunning clutch 52 of the transmission unit 50.

[0056] The second overrunning clutch 52 is installed such that when the reversible electric machine 30 operates as a motor, the rotation of the electric machine 30 can drive the main rotor 60 to rotate (the second overrunning clutch 52 is activated), but conversely, the rotation of the main rotor 60 cannot drive the electric machine 30 to rotate (the second overrunning clutch 52 is deactivated). In other words, the second overrunning clutch 52 can only transmit rotational torque in the direction of the electric machine 30 towards the main rotor 60, and cannot transmit it in the opposite direction.

[0057] Therefore, when the turboprop engine 100 operates in the 100% electric or hybrid mode, the rotation of the electric machine 30 can drive the rotor shaft 61 of the main rotor 60 to rotate.

[0058] In addition, when the turboprop engine 100 operates in the 100% electric mode, the electric machine 30 also drives a single oil pump 40 through the transmission unit 50. In the 100% electric mode, only the electric machine 30 supplies power to the main rotor 60 through the transmission unit 50 (the gas generator 12 and the free turbine 11 stop).

[0059] Similarly, when the turboprop engine 100 operates in the 100% thermal mode, the free turbine 11 also drives a single oil pump 40 through the transmission unit 50. In the 100% thermal mode, only the free turbine 11 (which is driven by the gas generator 12) supplies power to the main rotor 60 through the transmission unit 50 (the electric machine 30 stops).

[0060] When the turboprop engine 100 operates in the hybrid (thermal and electric) mode, the oil pump 40 is driven by the free turbine 11 and / or the electric machine 30. In the hybrid (thermal and electric) mode, the main rotor 60 is driven by both the free turbine 11 and the electric machine 30.

[0061] It should be noted that according to this embodiment, the starting phase of the gas generator 12 requires less power than the starter-type electric machine of the electric machine 30.

[0062] Figure 3Shows the structure according to the second embodiment, which differs from the first embodiment in that the second freewheel 52 of the transmission unit 50 is replaced by a reversible coupling device. In this example, the reversible coupling device is the first clutch 54. This example is not restrictive, and the reversible coupling device can be a manually detachable connector, which has lower technical complexity than a clutch. However, the advantage of the clutch 54 is that it can be remotely controlled, for example, by a control unit (not shown), including during flight.

[0063] The clutch 54 is capable of moving between a coupled position (or "closed clutch" or "clutch position") and a decoupled position (or "open clutch" or "decoupled position"), in which coupled position, the motor 30 is mechanically coupled to the rotor shaft 61 via the transmission unit 50 and can drive the main rotor 60 during operation in motor mode, or be driven by the main rotor 60 or the free turbine 11 during operation in generator mode, and in which decoupled position (which is the Figure 3 position shown in), the motor 30 is decoupled from the main rotor 60.

[0064] Different from the first embodiment including the second freewheel 52, the clutch 54 can mechanically couple the motor 30 and the main rotor 60 when closed (i.e., in the coupled position), so that the motor 30 can drive the main rotor 60 and vice versa. In addition, during 100% thermal operation, the clutch 54 in the decoupled position can prevent the free turbine 11 from driving the motor 30.

[0065] This configuration allows: in addition to the motor mode during the above-mentioned 100% electric or hybrid operation, the motor 30 can also operate in generator mode by being driven by the main rotor 60, so as to generate electricity on the ground or during flight, to supply this electricity to different devices of the aircraft or to charge the high-voltage battery.

[0066] Figure 4 and Figure 5 Shows the structure according to the third embodiment, which differs from the second embodiment in that the turboprop engine 100 includes a coupling shaft 70, which has a first end and a second end, the first end being engaged with the transmission unit 50 and the second end being engaged with the accessory gearbox 20 and thus with the generator shaft 14. In other words, according to this embodiment, the transmission unit 50 and the accessory gearbox 20 are physically coupled to each other. The coupling shaft 70 is preferably flexible to compensate for the alignment deviation between the transmission unit 50 and the accessory gearbox 20.

[0067] Figure 5 Shows a detailed view of the turboprop engine 100 according to the third embodiment, and in addition, certain devices are hidden, such as the free turbine 11, the main rotor 60, the oil pump 40 or any freewheel. In particular, Figure 5Shows in detail the running gear included in the transmission unit 50, which includes various wheels 51, 52 that engage with each other and may be free wheels. It should be noted that in this example, the rotation axis Y of the main rotor 60 (i.e., the rotor shaft 61) is radially offset relative to the main axis X of the turboprop engine 100, and the main axis X of the turboprop engine 100 is schematically represented in a simplified manner. This arrangement facilitates the physical connection between the transmission unit 50 and the accessory gearbox 20 through the coupling shaft 70.

[0068] According to this embodiment, the coupling shaft 70 may include a coupling free wheel 72, which is oriented such that the gas generator 12 cannot drive the transmission unit 50 or the electric motor 30 through the coupling shaft 70.

[0069] More specifically, the coupling free wheel 72 is installed such that: when the reversible electric motor 30 operates towards the gas generator 12 in the motor mode, the rotation of the electric motor 30 can drive the gas generator 12 to rotate through the transmission unit 50 and the coupling shaft 70 (the coupling free wheel 72 is activated), but conversely, the rotation of the gas generator 12 cannot drive the electric motor 30 to rotate (the coupling free wheel 72 is deactivated). In other words, the coupling free wheel 72 can only transmit the rotational torque in the direction of the electric motor 30 towards the gas generator 12, and cannot transmit it in the opposite direction.

[0070] According to a modified example of this embodiment, the coupling free wheel 72 may not exist. This structure will allow an operating mode in which the main rotor 60 is blocked, the gas generator 12 operates alone to drive the accessories of the accessory gearbox 20, and in addition, the electric motor 30 stops. In fact, the coupling shaft 70 engaged with the transmission unit 50 can drive the oil pump 40 engaged with the transmission unit 50 without the need for a second oil pump connected to the gas generator 12.

[0071] According to this third embodiment, the electric motor 30 can drive the generator shaft 14 through the coupling shaft 70, thereby driving the gas generator 12. Therefore, the electric motor 30 can be used to start the gas generator 12. Therefore, different from the first embodiment and the second embodiment, a starter is not required. In other words, according to this embodiment, the turboprop engine 100 includes a single electric motor, which is the high-power reversible electric motor 30, and thus can be used to drive the main rotor 60 in the motor mode and also to start the gas generator 12.

[0072] In addition, the second end of the coupling shaft 70 is engaged with the generator shaft 14 through a safety disconnect device, which is the weakening portion 24 in this example, and is configured to: in the case of blockage of the gas generator 12 (such as during its accidental shutdown or failure), allow the coupling shaft 70 to disconnect from the generator shaft 14.

[0073] In fact, under flight conditions and in the event of an engine failure that causes the gas generator 12 to shut down or even jam, by electrically driving the main rotor 60 by the electric motor 60 after placing the clutch 54 in the coupled position, it is possible to retain part of the thrust and improve the maneuverability of the aircraft. However, in such a structure including the coupling shaft 70, the electric motor 30 will subsequently drive the gas generator 12 simultaneously with the main rotor 60, which may represent a significant drag load.

[0074] The weakening part 24 arranged between the coupling freewheel 72 and the gas generator 12 can avoid this situation by disconnecting the coupling shaft 70 and the generator shaft 14. Therefore, the electric motor 30 can perform its function of driving the main rotor 60 in the event of an engine failure (including in the case where the failure causes the generator to jam).

[0075] Figure 6 Shows the structure according to the fourth embodiment, which is different from the third embodiment in that the clutch 54 is replaced by a second freewheel 52 similar to the first embodiment. The second freewheel 52 and the coupling freewheel 72 are installed in opposite ways to each other.

[0076] The reversible electric motor 30 is capable of rotating in a first rotation direction (usually the positive direction), in which direction the electric motor 30 is mechanically connected to the main rotor 60 through the second freewheel 52, and the electric motor 30 is capable of rotating in a second rotation direction opposite to the first rotation direction (usually the negative direction), in which direction the electric motor 30 is mechanically connected to the gas generator 12 through the coupling freewheel 72 of the coupling shaft 70.

[0077] In particular, in Figure 6 and the following figures, the elements indicated by "-1" represent gears (such as pinions), which allow the reversal of the rotation direction. Therefore, it can be understood that when the electric motor 30 rotates in the positive direction, the second freewheel 52 is activated and the coupling freewheel 72 is deactivated; while when the electric motor 30 rotates in the negative direction, the second freewheel 52 is deactivated and the coupling freewheel 72 is activated. In this embodiment, the weakening part 24 is not required.

[0078] Figure 7 Shows the structure according to the fifth embodiment, which is different from the third embodiment in that the coupling freewheel 72 is replaced by a second clutch 74 similar to the first clutch 54.

[0079] Depending on the operating phase of the turboprop engine 100, the first clutch 54 and the second clutch 74 can be remotely controlled, for example, by a monitoring unit. For example, during the start-up phase, the first clutch 54 is placed in the decoupled position, while the second clutch 74 is placed in the coupled position. Thus, the electric machine 30 can drive the gas generator 12 without driving the main rotor 60. Conversely, during 100% electric or hybrid operation, the first clutch 54 is placed in the coupled position while the second clutch 74 is placed in the decoupled position. Thus, the electric machine 30 can drive the main rotor 60 without driving the gas generator 12.

[0080] The turboprop engine structures according to these different embodiments allow a large number of functions to be performed while optimally meeting safety requirements and also optimizing the arrangement of components dedicated to lubrication and the mass of the assembly. The following refers to Figures 8A to 13 These different functions are described based on the structures corresponding to the third and fourth embodiments described above.

[0081] It should generally be noted that, for the sake of clarity, Figures 8A to 13 the different operating modes of the device are schematically represented in a functional and simplified manner without representing all the details of the elements constituting the turboprop engine and the different power transmission components. In particular, the pinions and any gear ratios are not represented. In addition, it should be noted that in the following description Figures 8A to 13 the arrows indicate the direction of power transfer from one component to another, while the crossed-out arrows indicate that the power transfer in the direction indicated by these arrows is blocked (e.g., when the clutch is open).

[0082] Figure 8A and Figure 8B represent the operating modes that allow the start-up of the turboprop engine 100 based on the structures corresponding to the third embodiment ( Figure 4 ) and the fourth embodiment ( Figure 6 ) respectively.

[0083] In the third embodiment ( Figures 8A to 8B in Figure 8A ), during start-up, the clutch 54 is placed in the decoupled position, preventing power from being transferred from the electric machine 30 to the main rotor 60, and this power is then transferred to the gas generator 12 through the overrunning clutch 72. When the gas generator 12 reaches the self-sustaining operating state (about 50% of its rated speed), the overrunning clutch 72 disengages, the electric machine 30 stops, and the free turbine 11 drives the propeller 62. The free turbine 11 also drives the oil pump 40 during start-up.

[0084] In the fourth embodiment ( Figures 8A to 8B in Figure 8B), during startup, the electric motor 30 is controlled, for example by a monitoring unit (not shown), so as to rotate in the negative direction. The gas generator 12 is thus driven by the activated coupling freewheel 72, thereby allowing the gas generator 12 to be started. The second freewheel 52 is then deactivated. During startup, the hot gases drive the free turbine 11. The free turbine 11, which is connected to the main rotor 60 via the first freewheel 51, drives the main rotor 60, in particular the propeller 62. Similarly, when the gas generator 12 reaches an autonomous operating state, the coupling freewheel 72 is disengaged, the electric motor 30 is stopped, and the free turbine 11 thus autonomously drives the propeller 62. During startup, the free turbine 11 also drives the oil pump 40.

[0085] Figures 9A to 9B The representations are based on the third embodiment ( Figure 4 ) and the fourth embodiment ( Figure 6 ) corresponding structure allows an operating mode of 100% thermal operation of the turboprop engine 100.

[0086] In the third embodiment ( Figures 9A to 9B In Figure 9A ), during 100% thermal operation, the clutch 54 is placed in the decoupled position, preventing power from being transmitted from the main rotor 60 to the motor 30, which stops. Only the gas generator 12 transmits power to the free turbine 11 and thus to the main rotor 60. Due to the orientation of the coupling freewheel 72, this power cannot be transmitted to the motor 30. During this operation, the free turbine 11 also drives the oil pump 40.

[0087] In the fourth embodiment ( Figures 9A to 9B In Figure 9B ), during 100% thermal operation, the electric machine 30 is stopped, and both the second freewheel 52 and the coupling freewheel 72 are deactivated. Therefore, only the gas generator 12 transmits power to the free turbine 11 and thus to the main rotor 60. The free turbine 11 also drives the oil pump 40 during this operation.

[0088] Figures 10A to 10B The representations are based on the third embodiment ( Figure 4 ) and the fourth embodiment ( Figure 6 ) corresponding structure allows a 100% electric operation mode of the turboprop engine 100.

[0089] In the third embodiment ( Figures 10A to 10B In Figure 10A), during 100% electric operation, the clutch 54 is placed in the coupled position, allowing power to be transmitted from the electric motor 30 to the main rotor 60. Only the electric motor 30 transmits power to the main rotor 60. In the case of a blockage of the gas generator 12, the breakage of the weakening portion 24 prevents power from being transmitted from the electric motor 30 to the gas generator 12. Additionally, due to the orientation of the first freewheel 51, power transmission from the main rotor 60 to the free turbine 11 is avoided. During this operation, the electric motor 30 drives the oil pump 40.

[0090] In the fourth embodiment ( Figures 10A to 10B in Figure 10B ), the electric motor 30 is controlled to rotate in the positive direction. Thus, the electric motor 30 drives the main rotor 60 through the activated second freewheel 52, allowing the rotation of the propeller 62. The coupled freewheel 72 is then deactivated. Similarly, due to the orientation of the first freewheel 51, power transmission from the main rotor 60 to the free turbine 11 is avoided, and during this operation, the electric motor 30 drives the oil pump 40.

[0091] Figures 11A to 11B represent operating modes that allow hybrid operation of the turboprop engine 100 based on the structures corresponding to the third embodiment ( Figure 4 ), respectively, and the fourth embodiment ( Figure 6 ).

[0092] In the third embodiment ( Figures 11A to 11B in Figure 11A ), during hybrid operation, the clutch 54 is placed in the coupled position, allowing power to be transmitted from the electric motor 30 to the main rotor 60. Both the electric motor 30 and the free turbine 11 transmit power to the main rotor 60. Due to the orientation of the coupled freewheel 72, power cannot be transmitted from the gas generator 12 to the electric motor 30.

[0093] Additionally, since the gas generator 12 also transmits power to the main rotor 60, the electric motor 30 rotates at a speed lower than that of the free turbine 11 and the gas generator 12. Therefore, the electric motor 30 cannot drive the gas generator 12 through the coupled freewheel 72. In particular, preferably, the electric motor 30 is sized such that: the maximum rotational speed of the electric motor 30 in the motor mode remains lower than the minimum rotational speed of the gas generator 12 during flight operation (excluding start-up or shut-down phases). Additionally, during this operation, the oil pump 40 can be driven by the electric motor 30 and / or the free turbine 11.

[0094] In the fourth embodiment ( Figures 11A to 11B in Figure 11B), the electric motor 30 is controlled to rotate in the positive direction. Thus, the electric motor 30 drives the main rotor 60 through the activated second freewheel 52, thereby allowing the rotation of the propeller 62. The coupling freewheel 72 is then deactivated. Thus, both the electric motor 30 and the free turbine 11 transfer power to the main rotor 60. Similarly, during this operation, the oil pump 40 can be driven by the electric motor 30 and / or the free turbine 11.

[0095] Figure 12 represents an operating mode that allows power generation by the electric motor 30 based on the structure corresponding to the third embodiment ( Figure 4 ).

[0096] In the third embodiment ( Figure 12 ), during power generation by the electric motor 30, the clutch 54 is placed in the coupled position, allowing power to be transferred from the main rotor 60 to the electric motor 30. Only the gas generator 12 transfers power to the free turbine 11 and thus to the main rotor 60. The main rotor 60 itself transfers power to the reversible electric motor 30, which operates in generator mode and can thus supply power to different devices, such as charging a battery.

[0097] Due to the orientation of the coupling freewheel 72, power cannot be transferred from the gas generator 12 to the electric motor 30. Furthermore, preferably, the electric motor 30 is sized such that: the maximum rotational speed of the electric motor 30 in generator mode remains lower than the minimum rotational speed of the gas generator 12 during flight operation (excluding start-up or shut-down phases), such that the rotation of the electric motor 30 cannot drive the gas generator 12 through the coupling freewheel 72. Additionally, during this operation, the free turbine 11 also drives the oil pump 40.

[0098] It should also be noted that due to the orientation of the second freewheel 52, the structure corresponding to the fourth embodiment ( Figure 6 ) does not allow an operating mode of power generation by the electric motor 30.

[0099] Figure 13 represents an operating mode called the "wind turbine" operating mode based on the structure corresponding to the third embodiment ( Figure 4 ), which allows power generation. In this operating mode, the propeller 62 is driven to rotate by the forward movement of the aircraft, and the main rotor 60 thus drives the electric motor 30.

[0100] In the third embodiment ( Figure 13In ( ), during the so-called "wind turbine" operating mode, the clutch 54 is placed in the coupled position, allowing power to be transmitted from the main rotor 60 to the electric machine 30. The gas generator 12 and the free turbine 11 operate at idle speed during flight, and if the rotational speed of the propeller 62 caused by the forward movement of the aircraft is greater than the rotational speed of the free turbine 11, no power is transmitted to the main rotor 60. On the contrary, if the propeller 62 cannot recover sufficient power from the forward movement of the aircraft, it can be driven by the free turbine 11 operating at idle speed. Due to the orientation of the overrunning freewheel 72, power cannot be transmitted from the gas generator 12 to the electric machine 30. In addition, as long as the rotational speed of the electric machine 30 remains lower than the rotational speed of the gas generator 12, the electric machine 30 does not drive the gas generator 12 and the overrunning freewheel 72 is not engaged.

[0101] In addition, due to the orientation of the first freewheel 51, the transmission of power from the main rotor 60 to the free turbine 11 is avoided. Thus, even though the gas generator 12 and the free turbine 11 operate at idle speed during flight, the rotation of the propeller 62 generated by the forward movement of the aircraft allows the actuation of the main rotor 60, and the main rotor 60 itself thus transmits power to the reversible electric machine 30 operating in the generator mode. During this operation, the main rotor 60 also drives the oil pump 40.

[0102] It should also be noted that due to the orientation of the second freewheel 52, the structure corresponding to the fourth embodiment ( Figure 6 ) does not allow an operating mode called the "wind turbine" operating mode, which allows power generation by the electric machine 30.

[0103] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes can be made to these examples without departing from the overall scope of the invention defined by the claims. In particular, the individual features of the various illustrated / described embodiments can be combined in additional embodiments. Therefore, the specification and the drawings should be regarded as exemplary rather than restrictive.

Claims

1. A hybrid turboprop engine (100) for an aircraft, the hybrid turboprop engine (100) comprising: A gas generator (12) carried by a generator shaft (14); a free turbine (11) carried by a turbine shaft (13) and rotationally driven by a gas flow generated by the gas generator (12), the turbine shaft (13) being engaged with a main rotor (60) through a transmission unit (50), the transmission unit (50) including a first freewheel (51), the first freewheel (51) being oriented such that the main rotor (60) cannot drive the free turbine (11); a reversible motor (30) capable of being engaged with the main rotor (60) through the transmission unit (50) to drive the main rotor (60) during an electric or hybrid operation mode, the turboprop engine (100) including: a single oil pump (40) engaged with the transmission unit (50) to be selectively driven by the turbine shaft (13) or the motor (30) according to the operation mode of the turboprop engine (100).

2. The hybrid turboprop engine (100) according to claim 1, wherein, The motor (30) is engaged with the main rotor (60) through a second freewheel (52) of the transmission unit (50), the second freewheel (52) being oriented such that the main rotor (60) cannot drive the motor (30).

3. The hybrid turboprop engine (100) according to claim 1, wherein, The motor (30) is capable of being engaged with the main rotor (60) through a reversible coupling device (54), the reversible coupling device (54) being capable of moving between a coupling position and a decoupling position, in the coupling position, the motor (30) can drive the main rotor (60) during operation in motor mode, or be driven by the main rotor (60) or the free turbine (11) during operation in generator mode, in the decoupling position, the motor (30) is decoupled from the main rotor (60).

4. The hybrid turboprop engine (100) according to claim 3, wherein, The reversible coupling device (54) is a clutch.

5. The hybrid turboprop engine (100) according to claim 3 or 4, the hybrid turboprop engine (100) including a coupling shaft (70) having a first end engaged with the transmission unit (50) and a second end engaged with the generator shaft (14).

6. The hybrid turboprop engine (100) according to claim 5, wherein, The coupling shaft (70) includes a coupling freewheel (72), the coupling freewheel (72) being oriented such that the gas generator (12) cannot drive the motor (30).

7. The hybrid turboprop engine (100) according to claim 5 or 6, wherein, The second end of the coupling shaft (70) is engaged with the generator shaft (14) through a safety disconnect device (24), the safety disconnect device (24) being configured to: in the case of partial or complete blockage of the gas generator (12), allow the coupling shaft (70) to disconnect from the generator shaft (14).

8. The hybrid turboprop engine (100) according to claim 2, wherein the hybrid turboprop engine (100) includes a coupling shaft (70) having a first end engaged with the transmission unit (50) and a second end engaged with the generator shaft (14), the coupling shaft (70) including a coupling freewheel (72) oriented such that the gas generator (12) cannot drive the electric machine (30), the second freewheel (52) configured to be activated when the electric machine (30) rotates in a first rotational direction, and the coupling freewheel (72) configured to be activated when the electric machine (30) rotates in a second rotational direction opposite to the first rotational direction.

9. The hybrid turboprop engine (100) according to claim 5, wherein, The reversible coupling device (54) is a first reversible coupling device, and the second end of the coupling shaft (70) is engaged with the generator shaft (14) through a second reversible coupling device (74) that is movable between a coupling position and a decoupling position, in which the electric machine (30) and the gas generator (12) are coupled in the coupling position and decoupled in the decoupling position.

10. The hybrid turboprop engine (100) according to any one of claims 5 to 9, wherein, The generator shaft (14) is engaged with an accessory gearbox (20) different from the transmission unit (50), and the second end of the coupling shaft (70) is engaged with the accessory gearbox (20).

11. An aircraft, comprising: The hybrid turboprop engine (100) according to any one of the preceding claims, wherein the aircraft is a propeller aircraft.

Images