Hybrid propulsion system for aircraft

Abstract

The invention relates to a hybrid propulsion system (2) comprising: a turbine engine (3) comprising a high-pressure body (4) and a low-pressure body (5), the low-pressure body (5) comprising a reduction gear (11) forming part of a drive gearbox (12) positioned axially at a front end (13) of the propulsion system (2); -first and second motors (14, 15) mechanically connected to the high and low voltage bodies (4, 5), respectively, the motors (14, 15) being configured to operate in a so-called motor and generator mode, the first and second motors (14, 15) being fixed to the drive gearbox (12); -a control system (16) configured to enable power transfer between the high and low pressure bodies (4, 5) via the first and second motors (14, 15).

Description

Technical Field

[0001] The present invention relates to a hybrid propulsion system for an aircraft. Background Art

[0002] Hybrid electric propulsion of aircraft is one way to significantly reduce the carbon footprint of air transport.

[0003] For example, such propulsion systems combine a thermal turbine with one or more electric machines that can augment or supplement the turbine.

[0004] The combination of thermal and electrical energy significantly reduces the fuel consumption of the turbine and thus reduces the CO2 emissions of the turbine.

[0005] Application FR-B1-3062882 in the name of the Applicant describes a hybrid propulsion system for a helicopter comprising a main turboshaft engine and an electric motor used in emergency situations (for example when the main turboshaft engine fails) to temporarily power the helicopter for certain manoeuvres.

[0006] Improvements to such propulsion systems are possible, and engine manufacturers are investigating various possibilities for integrating the electric motor or motors in the best possible way, in particular to optimize the overall size of the propulsion system, minimize modifications, and facilitate maintenance of the electric motor or motors.

[0007] Therefore, the object of the present invention is to provide a simple, effective and economical solution to the above problems.

[0008] The prior art also includes documents US2020 / 386188A1, US2020 / 182158A1 and GB2589193A. Summary of the invention

[0009] Therefore, the present invention proposes a hybrid propulsion system for an aircraft, the hybrid propulsion system comprising:

[0010] a turboshaft engine comprising a high-pressure body and a low-pressure body capable of rotational movement, the high-pressure body comprising a compressor and an expansion turbine, the compressor and the expansion turbine being mechanically connected to each other via a high-pressure shaft, the low-pressure body comprising a power turbine, the power turbine driving the power take-off in rotation via a reduction gear, the reduction gear forming part of a transmission gearbox arranged axially at the front end of the propulsion system;

[0011] - a first electric machine and a second electric machine, the first electric machine and the second electric machine being mechanically connected to the high-voltage body and the low-voltage body, respectively, the electric machines being configured to operate in so-called motor and generator mode, the first electric machine and the second electric machine being attached to a transmission gearbox;

[0012] - A control system configured to enable power to be transmitted between the high-pressure body and the low-pressure body via the first and second electric machines.

[0013] Positioning the motor in this manner not only optimizes the overall size of the propulsion system, but also minimizes the modifications required to integrate the motor and facilitates maintenance operations since the motor is accessible and positioned in an obstruction-free environment.

[0014] For each motor, a transmission gearbox ensures the transmission of the rotational movement between the body and the motor, while offering the possibility of modifying the parameters associated with the movement (speed, torque, etc.) in order to operate the body and the motor within the desired operating range.

[0015] Transferring power between the high-pressure body and the low-pressure body via the electric machine enables the performance of the propulsion system to be optimized at the operating speed of the propulsion system.

[0016] The propulsion system according to the invention may include one or more of the following features and / or steps, taken independently of each other or in combination with each other:

[0017] - the first motor and the second motor are attached to the front surface of the transmission gearbox;

[0018] - the first motor is connected to the high-voltage body via a first transmission mechanism arranged in a transmission gearbox, the first transmission mechanism is preferably a gear mechanism;

[0019] - the second motor is connected to the low-voltage body via a second transmission mechanism arranged in the transmission gearbox, the second transmission mechanism is preferably a gear mechanism;

[0020] - the power turbine and the reduction gear are mechanically connected to each other via a low-pressure shaft, the low-pressure shaft and the high-pressure shaft are coaxial, and the low-pressure shaft passes through the interior of the high-pressure shaft;

[0021] -The power take-off device is capable of driving the main drive gearbox of the aircraft;

[0022] - the first and second electric machines are high voltage electric machines connected to a high voltage electrical network of the control system;

[0023] - the first electric machine is configured to start the turboshaft engine;

[0024] - The propulsion system is configured to operate in one of the following operating modes:

[0025] a first hybrid operation mode in which the first electric machine operates in generator mode and the second electric machine operates in motor mode, the electric energy generated by the first electric machine being used to supply electric energy to the second electric machine in order to transmit power from the high-voltage body to the low-voltage body;

[0026] - A second hybrid operation mode, in which the first electric machine operates in motor mode and the second electric machine operates in generator mode, the electric energy generated by the second electric machine being used to supply electric energy to the first electric machine to transfer power from the low-voltage body to the high-voltage body.

[0027] The invention also relates to an aircraft comprising a hybrid propulsion system as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will be better understood and other details, features and advantages thereof will become more apparent from the following description given by way of non-limiting example and with reference to the accompanying drawings, in which:

[0029] [ Figure 1 ] Figure 1 is a schematic diagram of an aircraft including a hybrid propulsion system according to the present invention;

[0030] [ Figure 2 ] Figure 2 yes Figure 1 A detailed front perspective view of the propulsion system is shown. DETAILED DESCRIPTION

[0031] Figure 1 A schematic diagram of a helicopter 1 comprising a hybrid propulsion system 2 is shown.

[0032] The example shown is by no means limiting, and the hybrid propulsion system 2 may be used to power an aircraft, a drone, or any other rotary-wing aircraft, such as a gyrocopter.

[0033] According to the present invention, the hybrid propulsion system 2 comprises:

[0034] a turboshaft engine 3 comprising a high-pressure body 4 and a low-pressure body 5 capable of rotational movement, the high-pressure body 4 comprising a compressor 6 and an expansion turbine 7, the compressor and the expansion turbine being mechanically connected to each other by a high-pressure shaft 8, the low-pressure body 5 comprising a power turbine 9 which drives in rotation a power take-off 10 via a reduction gear 11 which forms part of a transmission gearbox 12 arranged axially at the front end 13 of the propulsion system 2;

[0035] a first electric machine 14 and a second electric machine 15, which are mechanically connected to the high-pressure body 4 and the low-pressure body 5, respectively, the electric machines 14, 15 being configured to operate in so-called motor and generator mode, the first electric machine 14 and the second electric machine 15 being attached to the transmission gearbox 12;

[0036] A control system 16 configured to enable power to be transmitted between the high-pressure body 4 and the low-pressure body 5 via the first electric machine 14 and the second electric machine 15 .

[0037] Positioning the motor in this manner not only optimizes the overall size of the propulsion system, but also minimizes the modifications required to integrate the motor and facilitates maintenance operations since the motor is accessible and positioned in an obstruction-free environment.

[0038] For each motor, a transmission gearbox ensures the transmission of the rotational movement between the body and the motor, while offering the possibility of modifying the parameters associated with the movement (speed, torque, etc.) in order to operate the body and the motor within the desired operating range.

[0039] Transferring power between the high-pressure body and the low-pressure body via the electric machine enables the performance of the propulsion system to be optimized at the operating speed of the propulsion system.

[0040] like Figure 1 As shown, the propulsion system 2 drives a main rotor 17 equipped with rotors via a main transmission gearbox 18 (indicated by the acronym BTP) and a tail rotor 19 (also indicated by the acronym RAC for “Anti-Torque Rotor”) via a rear transmission gearbox 20 (indicated by the acronym BTA).

[0041] More specifically, the main transmission gearbox 18 is mechanically connected to the power take-off 10 of the turboshaft engine 3 by means of an upper transmission shaft 21. The rear transmission gearbox 20 is mechanically connected to the main transmission gearbox 18 by means of a lower transmission shaft 22. The lower transmission shaft 22 is vertically positioned below the upper transmission shaft 21.

[0042] As shown, the high-pressure body 4 forms part of the gas generator of the turboshaft engine 3, which includes a compressor 6, a combustion chamber 23 and an expansion turbine 7. The compressor 6 is supplied with air via an air inlet 24, and the compressor includes one or more compression stages, each of which is axial or centrifugal. The air inlet 24 is axially arranged between the transmission gearbox 12 and the compressor 6. The combustion chamber 23 is supplied with compressed air via the compressor 6, and the combustion chamber is supplied with fuel via one or more injectors. The air / fuel mixture is burned by one or more ignition devices. The exhaust gas from the combustion chamber 23 is expanded in the expansion turbine 7. The expansion turbine 7 includes one or more expansion stages, each of which is axial or centripetal. The expansion turbine 7 drives the compressor 6 via a high-pressure shaft 8 that can move around the axis X. The exhaust gas from the turboshaft engine 3 is discharged by means of an exhaust nozzle 25, which is axially arranged at the rear end 26 of the propulsion system 2.

[0043] As shown in the figure, the power turbine 9 is driven by the exhaust gas generated by the gas generator. Therefore, the power turbine 9 is axially positioned at the rear of the gas generator. The power turbine 9 drives the power output device 10 to rotate via the reduction gear 11. Compared with the rotation speed of the power turbine 9, the reduction gear 11 can reduce the rotation speed of the power output device 10. The power turbine 9 and the reduction gear 11 are mechanically connected to each other through the low-pressure shaft 27. The low-pressure shaft 27 and the high-pressure shaft 8 are coaxial and can move around the axis X. The low-pressure shaft 27 passes through the inside of the high-pressure shaft 8. The reduction gear 11 is part of the transmission gearbox 12, which is axially arranged at the front end 13 of the propulsion system 2. Advantageously, the reduction gear 11 is a gear reducer. The transmission gearbox 12 carries the first motor 14 and the second motor 15, as well as various other accessories, such as oil / fuel auxiliary devices, air / oil separators, etc. Therefore, the transmission gearbox 12 transmits the required power between the accessories of the turboshaft engine 3 and the movable body 4, 5.

[0044] By convention, in this application, the terms "front" and "rear" define the axial position of elements of the propulsion system 2, and it should be understood that the transmission gearbox 12 is axially arranged at the front end 13 of the propulsion system 2 and the exhaust nozzle 25 is axially arranged at the rear end 26 of the propulsion system 2.

[0045] Furthermore, by convention, in this application, the terms “axial” or “axially” refer to any direction parallel to the axis X.

[0046] As described above and shown in the figures, the first electric machine 14 is mechanically connected to the high pressure body 4 of the turboshaft engine 3 and is attached to the transmission gearbox 12 .

[0047] More specifically, the first motor 14 is attached to the front surface 28 of the transmission gearbox 12. The first motor 14 is arranged adjacent to the second motor 15. The first motor 14 is vertically positioned above the second motor 15. The first motor 14 is attached to the transmission gearbox 12 via a flange 29 equipped with screws, but the first motor 14 may be attached to the transmission gearbox 12, for example, via a collar.

[0048] The first motor 14 is connected to the high-voltage body 4 via a first transmission mechanism 30 arranged in the transmission gearbox 12. The first transmission mechanism 30 may have a fixed or variable transmission ratio, which may be equal to 1, less than 1 (reduction gear) or greater than 1 (speed-increasing gear).

[0049] Advantageously, the first transmission mechanism 30 is a gear mechanism. Thus, the transmission gearbox 12 comprises one or more gears of the first transmission mechanism 30 .

[0050] The first transmission mechanism 30 is shared with one or more gear transmission devices associated with other accessories or is separate from one or more gear transmission devices associated with other accessories. In addition, the first transmission mechanism 30 is shared with the gear transmission device of the reduction gear 11 or is separate from the gear transmission device of the reduction gear 11.

[0051] The first electrical machine 14 is configured to operate in motor mode and generator mode, i.e. the first electrical machine 14 is reversible. In motor mode, the first electrical machine 14 introduces mechanical power into the high-pressure body 4 of the turboshaft engine 3. In generator mode, the first electrical machine 14 collects mechanical power from the high-pressure body 4 of the turboshaft engine 3.

[0052] Advantageously, the first electric machine 14 is a high-voltage electric machine, in particular capable of delivering high levels of power.

[0053] The first motor 14 may be a DC motor or an AC motor.

[0054] Advantageously, the first electric machine 14 is also configured to start the turboshaft engine 3 .

[0055] As described above and shown in the figures, the second electric machine 15 is mechanically connected to the low-pressure body 5 of the turboshaft engine 3 and is attached to the transmission gearbox 12 .

[0056] More specifically, the second motor 15 is attached to the front surface 28 of the transmission gearbox 12. The second motor 15 is arranged adjacent to the first motor 14. The second motor 15 is positioned vertically below the first motor 14. The second motor 15 is attached to the transmission gearbox 12 via a flange 29 equipped with screws, but the second motor 15 may be attached to the transmission gearbox 12, for example, via a collar.

[0057] The second motor 15 is connected to the low-pressure body 5 via a second transmission mechanism 31 arranged in the transmission gearbox 12. The second transmission mechanism 31 may have a fixed or variable transmission ratio, which may be equal to 1, less than 1 (reduction gear) or greater than 1 (speed-increasing gear).

[0058] Advantageously, the second transmission mechanism 31 is a gear mechanism. Thus, the transmission gearbox 12 comprises one or more gears of the second transmission mechanism 31 .

[0059] The second transmission mechanism 31 is shared with one or more gear transmission devices associated with other accessories or is separate from one or more gear transmission devices associated with other accessories. In addition, the second transmission mechanism 31 is shared with the gear transmission device of the reduction gear 11 or is separate from the gear transmission device of the reduction gear 11. Finally, the second transmission mechanism 31 is shared with the first transmission mechanism 30 or is separate from the first transmission mechanism 30.

[0060] In the same way as the first electric machine 14, the second electric machine 15 is configured to operate in so-called motor and generator mode, in other words, the second electric machine 15 is reversible. In motor mode, the second electric machine 15 introduces mechanical power into the low-pressure body 5 of the turboshaft engine 3. In generator mode, the second electric machine 15 collects mechanical power from the low-pressure body 5 of the turboshaft engine 3.

[0061] Advantageously, the second electric machine 15 is a high-voltage electric machine, in particular capable of delivering a high level of power.

[0062] The second motor 15 can be a DC motor or an AC motor.

[0063] As shown, the transmission gearbox 12 is axially arranged at the front end 13 of the propulsion system 2. The transmission gearbox 12 is formed by two parts 32 that abut against each other in a transverse joint plane (a plane perpendicular to the axis X) and are held in place by attachment means such as screws. The transmission gearbox 12 includes a first transmission mechanism 30 and a second transmission mechanism 31 associated with the first motor 14 and the second motor 15, transmissions associated with other accessories, and the gear transmission of the reduction gear 11.

[0064] The control system 16 of the propulsion system 2 comprises a turboshaft engine computer, called FADEC, a low-voltage electrical network 33 and a high-voltage electrical network 34 , these networks 33 , 34 being able to be connected to one another or independent of one another.

[0065] In particular, the high voltage electrical network 33 is used to transfer large amounts of electrical power between the first and second electrical machines 14, 15, and is often referred to as an "internal hybrid electrical network". Thus, advantageously and as described above, the first and second electrical machines 14, 15 are high voltage electrical machines connected to the high voltage electrical network 33.

[0066] In particular, the low-voltage electrical network 34 is used to supply power to the propulsion system 2 and to various accessories of the helicopter 1 .

[0067] The control system 16 notably implements operating modes for the propulsion system 2 according to the different flight phases of the helicopter 1 (take-off, cruise, landing, search, obstacle, standby, emergency situations (for example turboshaft engine failure)).

[0068] In particular, the control system 16 can implement a hot operating mode in which the propulsion mechanical energy required to drive the rotors 17 , 19 is supplied solely by the turboshaft engine 3 .

[0069] The control system 16 can also implement a hybrid operating mode in which the propulsion mechanical energy required to drive the rotors 17 , 19 is supplied by the turboshaft engine 3 and the first and / or second electrical machines 14 , 15 operating in motor mode.

[0070] As described above, the control system 16 is configured to enable power to be transmitted between the high-pressure body 4 and the low-pressure body 5 via the first motor 14 and the second motor 15 .

[0071] Therefore, the propulsion system 2 can operate in a first hybrid operation mode, in which the first motor 14 operates in a generator mode and the second motor 15 operates in a motor mode, and the electric energy generated by the first motor 14 is used to supply power to the second motor 15 to transfer power from the high-pressure body 4 to the low-pressure body 5.

[0072] The propulsion system 2 can also operate in a second hybrid operation mode, in which the first motor 14 operates in an electric motor mode and the second motor 15 operates in a generator mode, and the electric energy generated by the second motor 15 is used to supply power to the first motor 14 to transfer power from the low-pressure body 5 to the high-pressure body 4.

[0073] Advantageously, the control system 16 comprises one or more electrical energy storage devices 35, each of which is configured to store electrical energy generated by the first motor 14 and / or the second motor 15. For example, each electrical energy storage device 35 comprises one or more batteries or supercapacitors. The stored electrical energy is used, for example, to supply power to the first motor 14 and / or the second motor 15 operating in motor mode during certain flight phases, or to supply power to the propulsion system 2 and / or electrical accessories of the helicopter 1.

[0074] The control system 16 may include one or more power converters configured to convert alternating current to direct current (or vice versa). Such converters are used, for example, to enable power to be transferred between the electric machines 14, 15 via a high voltage direct current bus, known as an HVDC bus.

[0075] Advantageously, the control system 2 comprises protection means making it possible to protect the electrical networks 33 , 34 from short circuits, overvoltages and overcurrents.

[0076] The various movable elements of the propulsion system 2 may be rotationally connected to each other by coupling means such as splines (floating or fixed), threaded flanges or by shrink-fit shafts. The coupling means may include a clutch or an elastically deformable device known as a flexible coupling.

[0077] Advantageously, the first 14 and second 15 electric machines are cooled and lubricated via a cooling and lubrication circuit of the propulsion system 2 . Such a circuit is already used for cooling and lubricating the transmission gearbox 12 .

[0078] This means that the cooling and lubrication devices associated with the various elements of the propulsion system 2 can be consolidated in order to optimize the overall weight of the propulsion system 2 .

[0079] For the first and second electric machines 14, 15, the cooling and lubrication circuits are used in particular to cool the rotors and stators of the electric machines 14, 15, but also to lubricate the dynamic seals and the bearings guiding the rotors. In the case of the transmission gearbox 12, the cooling and lubrication circuits are used in particular to cool and lubricate the gears and rolling bearings in the housing 12.

[0080] For example, the cooling and lubrication circuits are supplied with oil.

Claims

1. A hybrid propulsion system (2) for an aircraft (1), the hybrid propulsion system comprising: - a turboshaft engine (3), comprising a high-pressure body (4) and a low-pressure body (5) capable of rotational movement, the high-pressure body (4) comprising a compressor (6) and an expansion turbine (7), the compressor and the expansion turbine being mechanically connected to each other via a high-pressure shaft (8), the low-pressure body (5) comprising a power turbine (9) driving a power take-off (10) in rotation via a reduction gear (11), the reduction gear (11) forming part of a transmission gearbox (12), the transmission gearbox being arranged axially at the front end (13) of the propulsion system (2); - a first electric machine and a second electric machine (14, 15), the first electric machine and the second electric machine being mechanically connected to the high-pressure body and the low-pressure body (4, 5), respectively, the electric machines (14, 15) being configured to operate in so-called motor and generator mode, the first electric machine and the second electric machine (14, 15) being attached to the transmission gearbox (12); - a control system (16) configured to enable power to be transmitted between the high-pressure body and the low-pressure body (4, 5) via the first and second electric machines (14, 15).

2. The propulsion system (2) according to claim 1, characterized in that The first and second motors (14, 15) are attached to a front surface (28) of the transmission gearbox (12).

3. A propulsion system (2) according to any one of the preceding claims, characterized in that The first motor (14) is connected to the high-pressure body (4) via a first transmission mechanism (30) arranged in the transmission gear box (12), and the first transmission mechanism (30) is preferably a gear mechanism.

4. A propulsion system (2) according to any one of the preceding claims, characterised in that The second motor (15) is connected to the low-pressure body (5) via a second transmission mechanism (31) arranged in the transmission gear box (12), and the second transmission mechanism (31) is preferably a gear mechanism.

5. A propulsion system (2) according to any one of the preceding claims, characterised in that The power turbine (9) and the reduction gear (11) are mechanically connected to each other via a low-pressure shaft (27), the low-pressure shaft and the high-pressure shaft (27, 8) are coaxial, and the low-pressure shaft (27) passes through the interior of the high-pressure shaft (8).

6. A propulsion system (2) according to any one of the preceding claims, characterised in that The power output device (10) is capable of driving a main transmission gearbox (18) of the aircraft (1).

7. A propulsion system (2) according to any one of the preceding claims, characterised in that The first and second electric machines (14, 15) are high-voltage electric machines connected to a high-voltage electrical network (33) of the control system (16).

8. A propulsion system (2) according to any one of the preceding claims, characterised in that The first electric machine (14) is configured to start the turboshaft engine (3).

9. A propulsion system (2) according to any one of the preceding claims, characterised in that The propulsion system is configured to operate in one of the following operating modes: a first hybrid operation mode, in which the first electric machine (14) operates in generator mode and the second electric machine (15) operates in motor mode, the electric energy generated by the first electric machine (14) being used to supply electric energy to the second electric machine (15) in order to transmit power from the high-voltage body (4) towards the low-voltage body (5); - A second hybrid operation mode, in which the first motor (14) operates in motor mode and the second motor (15) operates in generator mode, and the electric energy generated by the second motor (15) is used to supply electric energy to the first motor (14) to transmit power from the low-voltage body (5) to the high-voltage body (4).

10. An aircraft (1) comprising a hybrid propulsion system (2) according to any one of the preceding claims.

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