Improved turbine for hybrid aircraft

Abstract

The invention relates to a turbine (100) for a hybrid aircraft, comprising: a gas generator (12) carried by a generator shaft (14); at least one free turbine (11) carried by the turbine shaft (13) and rotated by the gas flow generated by the gas generator (12); a main rotor (60); and at least one reversible electric machine (30), the turbine shaft (13) being a through-shaft and extending axially between a first end engaged with the electric machine (30) and a second end engaged with the main rotor (60).

Description

Technical Field

[0001] The present invention relates to the field of hybrid aircraft comprising at least one turbine for a flying machine, such as a turboprop engine for an airplane or a turbine engine for a helicopter. In particular, the present invention relates to a turbine for a hybrid aircraft and to a hybrid aircraft comprising such a turbine. Background Art

[0002] In a known manner, a turbomachine for a helicopter or for an aircraft, such as a turbine engine or a turboprop, comprises a gas turbine with a gas generator and a free turbine driven in rotation by the gas flow generated by the gas generator. In a manner known per se, the free turbine is completely independent of the gas generator and comprises one or two (high-pressure and low-pressure) compressors and one or two (high-pressure and low-pressure) turbines. In particular, the shaft of the free turbine and the shaft of the gas generator (carrying the compressor and the turbine) are not connected. Thus, the free turbine is different from the (high-pressure and low-pressure) turbines carried by the shaft of the gas generator, which are connected to the compressor. Thus, the free turbine turboprop is characterized by the separation of the "engine" (gas generator) and the "power turbine" (or free turbine) elements. Furthermore, in addition to this turbine, the aircraft generally comprises a reversible electric machine, which is coupled to the gas generator in order to rotate the gas generator during the start-up phase of the turbine or in flight to ensure the non-propulsion power needs of the aircraft.

[0003] Traditionally, a gas generator comprises at least one compressor and one turbine coupled in rotation. The operating principle is as follows: the fresh air entering the gas turbine is compressed due to the rotation of the compressor before being sent to a combustion chamber, where it is mixed with fuel. The gases burned due to the combustion are then discharged at high speed. A first expansion then takes place in the gas generator turbine, during which the gas generator turbine extracts the energy required for driving the compressor. The gas generator turbine does not absorb all the kinetic energy of the burned gases, and the excess kinetic energy corresponds to the gas flow produced by the gas generator. The gas generator therefore provides kinetic energy to the free turbine, so that a second expansion takes place in the free turbine, which converts this kinetic energy into mechanical energy in order to drive a receiving member, such as a propeller of a turboprop engine.

[0004] During the start-up phase of the turbomachine, the gas generator must be driven in rotation, ie the compressor coupled to the turbomachine. As mentioned above, this is exactly one of the roles of a reversible electric machine, known elsewhere, which is most often an electric motor that can reversibly operate as a generator.

[0005] In fact, the aircraft in which this turbomachine is particularly intended to be integrated comprises electrical equipment that must be powered by electrical energy. A reversible electric machine is used to provide this electrical equipment with electrical power. To this end, the electric machine (this time operating as a generator) is driven in rotation by the gas generator, the mechanical energy on the gas generator being converted by said machine into electrical energy. Furthermore, the electric machine can be used to achieve internal hybridization, for example by transmitting additional power to the propeller shaft or the engine shaft, or by generating power by extracting it from the free turbine shaft, without affecting the performance of the gas generator.

[0006] To ensure these functions, the electric machine must be sized for a much higher power than the generator / starter usually used, typically one kilowatt or several hundred kilowatts instead of about ten kilowatts. It is therefore desirable to bring together these two types of electric machines (the generator / starter of the turbine and the electric machine connected to the rotor).

[0007] However, existing architectures do not allow electric machines to perform some functions. Moreover, these high-power electric machines involve difficulties in terms of volume. For example, some turboprop architectures feature a rear joint at the level of the free turbine and the hot gas injection nozzle to drive the reducer and propeller of the turboprop, as well as an accessory box in a cold area opposite to the engine to drive the equipment.

[0008] However, it is difficult to integrate high-power electric motors, which would necessarily be bulky on such an architecture. In fact, installing an electric motor driven at high speed by the turbine in a hot area, below the nozzle, would present difficulties in terms of integration, maintainability and thermodynamic environment. Therefore, the only possible solution is to drive the electric motor in a cold area, in particular at the level of the accessory box, thus affecting the performance of the gas turbine during the extraction operation from the gas generator. This contributes to a significant increase in the consumption of the engine. In addition, this increased consumption affects the durability of the aircraft, which is important, however, for example in applications of the drone type.

[0009] There are other types of architectures, in particular by placing the electric machine in a cold area near the propeller cone, when both the mechanical reducer of the propeller and the accessory box are on the same side of the engine. However, these architectures involve increasing the front of the turbine by offsetting the axis of the propeller relative to the main axis of the engine via the mechanical reducer, and / or involve affecting its centering and limiting the possibilities of merging the functions between the generator / starter of the turbine and the high-power electric machine.

[0010] Therefore, there is a need for an architecture that satisfies at least some of the above-mentioned disadvantages. Summary of the invention

[0011] The present invention relates to a turbine for a hybrid aircraft, the turbine comprising: a gas generator carried by a generator shaft; at least one free turbine, the at least one free turbine being carried by the turbine shaft and driven in rotation by a gas flow generated by the gas generator; a main rotor; and at least one reversible electric machine, the turbine shaft being a through shaft and extending axially between a first end engaged with the electric machine and a second end engaged with the main rotor.

[0012] The turbomachine may be a turbine engine or a turboprop engine. In the remainder of this description, reference will preferably be made to a turboprop engine. The main rotor may be a propeller allowing the propulsion of an aircraft, in particular an airplane, the propeller being arranged at one end of the turboprop engine, preferably at the front end of the turboprop engine when considering the normal direction of the aircraft displacement. The main rotor can thus be moved around an axis of rotation, preferably corresponding to the main axis of the turboprop engine.

[0013] "Passing through" should be understood as the turbine shaft extending axially on either side of the turboprop along the main axis of the turboprop. Therefore, the turbine shaft passes through the high-pressure turbine, the combustion chamber and the compressor on one side, and through the outlet nozzle on the other side. The turbine shaft therefore passes through a thermodynamically cold region including an air inlet and a compressor, and a thermodynamically geothermal region, in other words, the temperature in the thermodynamically geothermal region is higher than in the cold region, and includes a combustion chamber and a nozzle. The rotor of this turboprop is specifically configured so that the turbine shaft passes through it. In addition, preferably, the generator shaft and the turbine shaft are concentric, and the turbine shaft passes through the gas generator by passing through the inside of the generator shaft. It should therefore be understood that the turbine shaft is completely independent of the generator shaft and the one or more compressors it carries.

[0014] Furthermore, by "engagement", it is understood that the first end of the turbine shaft is mechanically connected directly or indirectly to the electric machine. Thus, the reversible electric machine can drive the turbine shaft to rotate and can be driven inversely by the turbine shaft to generate electricity. Similarly, it is understood that the second end of the turbine shaft is mechanically connected to the main rotor, for example to a propeller, directly or through a mechanical reducer.

[0015] Unlike configurations in which the electric motor is arranged at the level of the accessory box in a cold area, this architecture, which includes a through-turbine shaft, allows the electric motor engaged with the turbine shaft to extract energy from the turbine shaft, thereby limiting the impact on the performance of the gas turbine and on the consumption of the engine.

[0016] Furthermore, according to this architecture in which the through-turbine shaft is joined at its two ends, in particular at a first end where it is joined to the electric machine and at its second end to the main rotor, it is possible to perform a large number of functions while preferably maintaining an aligned arrangement along the same axis of the different parts of the turboprop and thus limiting the front of the turboprop. This configuration makes it possible in particular to reduce the drag of the turboprop.

[0017] In some embodiments, the gas generator includes a compressor and an air inlet configured to supply fresh air to the compressor, and the first end of the turbine shaft engaged with the electric machine is arranged adjacent to the air inlet.

[0018] In other words, the electric machine is arranged in a thermodynamically cold area of ​​the turboprop engine. Thus, it is possible to facilitate the integration of the electric machine in the turboprop engine and improve its maintainability, unlike warmer thermal environments, such as below the hot gas injection nozzle, on the side of the turbine.

[0019] In some embodiments, the second end of the turbine shaft is engaged with the main rotor via a mechanical speed reducer arranged between the free turbine and the main rotor.

[0020] Unlike applications on helicopter turbine engines, where the mechanical reducer and the electric machine are each arranged on the same side of the gas generator, the mechanical reducer and the electric machine are here arranged at opposite ends of the turbine shaft. Thus, the electric machine is arranged at the level of a first end of the turbine shaft, preferably in a cold area, while the mechanical reducer can be arranged at the level of a second end of the turbine shaft, in a hot area. This makes it possible to maintain the electric machine in a cold thermodynamic environment in order to improve its reliability, improve modularity for maintenance, limit the front part of the hybrid turbine in order to improve the aerodynamics of the plane, and limit the impact of the centering of the electric machine.

[0021] In some embodiments, the turbine includes a combustion chamber, and the second end of the turbine shaft is engaged with the main rotor downstream of the combustion chamber.

[0022] It is understood that the terms "upstream" and "downstream" are defined relative to the normal direction of the gas flow in the turbine. In other words, the junction between the second end of the turbine shaft and the main rotor is located in the thermodynamic geothermal region of the turbine after the gas has entered the combustion chamber.

[0023] In some embodiments, the second end of the turbine shaft engages with the main rotor in the vicinity of the combustion chamber and the hot gas injection nozzle. Preferably, the engagement between the second end of the turbine shaft and the main rotor is positioned facing the injection nozzle.

[0024] In some embodiments, the electric motor is directly engaged with the first end of the turbine shaft so as to rotate at the same speed as the turbine shaft.

[0025] For example, an electric machine with a high power density tends to rotate at a speed comparable to a free turbine and can, for example, be fixed directly to the first end of the turbine shaft. This makes it possible to limit the number of assemblies required and thus simplify the architecture of the turboprop engine.

[0026] In some embodiments, the electric machine is coupled to the first end of the turbine shaft via a speed adaptor reducer.

[0027] When the free turbine does not allow direct engagement of the electric machine for driving, the speed adaptation reducer makes it possible to adapt the rotational speed of the electric machine to the rotational speed of the free turbine, depending on the size of the electric machine. This makes it possible to decouple the optimal size of the free turbine from the optimal size of the electric machine.

[0028] In some embodiments, the electric machine can be coupled to the generator shaft to rotate the gas generator during a startup phase of the turbine and can be coupled to the turbine shaft after the startup phase to generate electricity.

[0029] This configuration makes it possible to inject power into the gas generator, start the gas turbine, and then, when the speed of the gas generator exceeds a predetermined threshold, the turbine shaft then drives the electric motor so that the electric motor generates electricity. It is thus possible to achieve high power generation by extracting power from the turbine shaft without compromising the performance of the gas turbine. This configuration is particularly advantageous for non-hybrid applications that require high power generation, such as in applications using drones.

[0030] In some embodiments, the electric machine is coupled to the generator shaft via a first freewheel configured to transmit rotational torque from the electric machine, and is coupled to the turbine shaft via a second freewheel configured to transmit rotational torque to the electric machine.

[0031] It should be understood that the first freewheel and the second freewheel are mounted relative to each other. By "mounted relative to each other", it should be understood that the first freewheel can transmit the rotational torque from the motor, but not vice versa, and the second freewheel can transmit the rotational torque to the motor, but not vice versa. Preferably, the motor is coupled to the generator shaft via the first freewheel and the first speed adapter reducer, and is coupled to the turbine shaft via the second freewheel and the second speed adapter reducer, the reduction ratios of the first and second speed adapter reducers being determined so that after starting the gas generator, the first freewheel is not synchronized, and the second freewheel is synchronized.

[0032] A freewheel has the advantage of not needing to be electronically or mechanically controlled by an external operator. A freewheel also has a remarkable reliability. Such a freewheel is usually composed of a hub and a peripheral ring rotatably mounted on the hub. The hub can usually drive the peripheral ring in rotation, but not vice versa. It should be noted that in some cases, the freewheel is arranged so that the peripheral ring can drive the hub in rotation, but not vice versa, without questioning the principle of the invention. Moreover, the hub can drive the ring only when the hub rotates in a predetermined direction relative to the ring, the predetermined direction will be referred to as the "engagement direction". Otherwise, the hub and the peripheral ring rotate freely relative to each other.

[0033] In some embodiments, the electric machine is a first reversible electric machine, and the turbine further comprises a second reversible electric machine engaged with the generator shaft and capable of exchanging electric power with the first reversible electric machine.

[0034] Then, the first motor engaged with the first end of the turbine shaft is preferably a high power motor of the order of 1 kW or several hundred kW, while the second motor preferably has a low power of the order of 10 kW, such as a common generator / starter.

[0035] According to this configuration, when the second electric machine is used to start the gas turbine, the first electric machine can be used as a generator / starter to perform internal hybridization, that is, by exchanging power between the electric machines, by exchanging power between the body of the gas generator and the free turbine, in order to limit the aging of the gas turbine. This configuration also makes it possible to perform all the desired functions, in particular assistance in some transient phases through the transmission of power to the turbine shaft or to the generator shaft, assistance to the gas turbine during take-off, or electricity generation in flight in order to recharge the batteries.

[0036] In some embodiments, the first electric machine is configured to operate in a generator mode, in which it can be driven to rotate by the turbine shaft to generate electricity, or in a motor mode, in which it can transmit power to the turbine shaft.

[0037] In other words, in motor mode, the first electric machine is able to transmit power to the propeller in the case of a turboprop engine, or to the power take-off in the case of a turbine engine. The first electric machine is thus able to generate electricity without drawing power from the gas generator, which makes it possible to improve the specific consumption of the gas turbine. Furthermore, motor mode allows power to be transmitted to the turbine shaft during certain flight phases that require it, such as take-off, transient phases or maneuvers.

[0038] In some embodiments, the second electric machine is coupleable to the generator shaft via a first deactuable coupling and is coupleable to the turbine shaft via a second deactuable coupling.

[0039] In some embodiments, at least one of the first releasable coupling device and the second releasable coupling device is a freewheel, preferably a blockable freewheel, the first releasable coupling device is configured to be actuated when the second motor rotates in a first rotational direction, and the second releasable coupling device is configured to be actuated when the second motor rotates in a second rotational direction opposite to the first rotational direction.

[0040] By "deactuable coupling device" is meant that the coupling device can be in an actuated position, in which the components connected to the coupling device are coupled, or in a deactuated position, in which the components are decoupled, it being understood that "components" are the electric machine, the main rotor, the gas generator and the free turbine. The deactuable coupling device can in particular comprise a free wheel.

[0041] Given this configuration, it is possible to realize a large number of functions and in particular internal hybridization. More precisely, the second electric machine can ensure the extraction operation from the free turbine, for example by blocking the second deactivatable coupling means, so as not to affect the performance of the gas generator, or the injection of power on the turbine shaft and therefore on the main rotor, in order to assist the latter in some operating phases.

[0042] Furthermore, the second electric machine can be used in one direction of rotation to be mechanically coupled to the gas generator and in another direction of rotation to be mechanically coupled to the turbine shaft and thus to the main rotor. In particular, the second electric machine rotating in the first direction of rotation allows coupling with the gas generator in order to start the gas generator on the ground, but also in order to supplement the thermodynamic power in some flight phases, in order to assist, for example, transient phases or changes in the engine operating point.

[0043] The second electric machine rotating in the first rotational direction also makes it possible to restart the gas generator in flight, for example after a failure of the gas generator, without the need for actuation of another mechanical member, such as a clutch. Furthermore, the second electric machine rotating in the second rotational direction makes it possible to drive the main rotor in some flight phases requiring additional power transmission.

[0044] The architecture according to the present disclosure thus has the advantage of being simple by limiting the number of components and connections, while making it possible to perform a large number of functions, in particular internal hybridization, thus improving the reliability of the device.

[0045] In some embodiments, the turbine comprises a rotor brake that can be moved between a braking position that prevents the main rotor from rotating and a free position that allows the main rotor to rotate, the rotor brake being arranged upstream of the gas generator. In other words, not on the side of the propeller reducer, but opposite the turbine, the propeller brake system is arranged in its cold zone. It should be noted that the rotor braking function can be ensured by a blockable free wheel.

[0046] The present disclosure also relates to a hybrid aircraft comprising a turbine according to any one of the above embodiments. The hybrid aircraft may be an airplane and the turbine may be a turboprop engine.

[0047] A “hybrid-electric aircraft” is an aircraft comprising a heat engine for driving a main rotor in rotation and at least one electric machine for transmitting power to the heat engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention and its advantages will be better understood by reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the attached pages of the drawings, in which:

[0049] Figure 1 A cross-sectional view showing a turboprop engine for a hybrid aircraft according to the invention,

[0050] Figure 2 Schematically showing the first embodiment Figure 1 turboprop engine,

[0051] Figure 3 According to the second embodiment Figure 1 The propulsion components,

[0052] Figure 4 The first operation mode according to the second embodiment is shown in FIG. Figure 1 The propulsion components,

[0053] Figure 5 The second operation mode according to the second embodiment is shown in FIG. Figure 1 The propulsion components,

[0054] Figure 6 According to the third embodiment Figure 1 The propulsion components,

[0055] Figure 7 According to the fourth embodiment Figure 1 The propulsion components,

[0056] Figure 8 According to the fifth embodiment Figure 1 propulsion components. DETAILED DESCRIPTION

[0057] The architecture of the turbine, in this example of a turboprop engine 100 according to various embodiments of the invention, will be referred to Figures 1 to 8 This is described in the rest of the specification.

[0058] Figure 1 A turboprop engine 100 of an aircraft is schematically shown, which rotationally drives a main rotor 60 of the aircraft, which comprises a rotor shaft 61 carrying a propeller 62 .

[0059] The turboprop 100 is of the free turbine type and in this respect comprises a gas turbine 10 having a gas generator 12 and a free turbine 11 which can be driven in rotation by the gas flow generated by the gas generator 12. The free turbine 11 is mounted on a turbine shaft 13 which transmits the rotational motion to the main rotor 60 via a mechanical reducer 50. The turbine shaft 13 is thus a through shaft and is located at what is conventionally called the rear end (at the Figure 1 The first end (on the left) and the traditionally called front end (on the Figure 1 The turbine 10 extends between the second end (on the right side of the center), passing through the gas generator 12 and the free turbine 11.

[0060] A first end of the turbine shaft 13 is engaged with the reversible electric machine 30, and a second end of the turbine shaft 13 is engaged with the mechanical reducer 50. Therefore, according to the present invention, the gas turbine 10 is of a type having a front power take-off and a rear power take-off.

[0061] The gas generator 12 comprises a rotating generator shaft 14 on which at least one centrifugal compressor 15 and at least one turbine 16 are mounted, and a combustion chamber 17 which is arranged axially between the compressor 15 and the turbine 16 when the gas generator 12 is considered in the axial direction of the generator shaft 14. The gas turbine 10 has a casing 18 provided with an air inlet 19 through which fresh air enters the gas generator 12. After its entry into the casing of the gas generator 12, the fresh air is compressed by the compressor 15 which drives it back towards the inlet of the combustion chamber 17 where it is mixed with fuel. The combustion that takes place in the combustion chamber 17 causes the combustion gases to be discharged at a high speed towards the turbine 16, which has the effect of driving the shaft 14 of the gas generator 12 in rotation and therefore the compressor 15 in rotation. The rotation speed of the shaft 14 of the gas generator 12 is determined by the fuel flow rate entering the combustion chamber 17. Since the turboprop 100 is of the free turbine type, it will be understood that the generator shaft 14 is independent of the turbine shaft 13. In other words, unlike the turbine 16 connected to the compressor 15, the free turbine 11 and the turbine shaft 13 are completely independent of the generator shaft 14 and the compressor 15.

[0062] Although the turbine 16 extracts kinetic energy, the gas stream leaving the gas generator has significant kinetic energy. Figure 1 As understood in , the gas flow F is directed towards the free turbine 11 which has the effect of causing an expansion in the free turbine 11 , resulting in the rotation of the turbine wheel and the turbine shaft 13 .

[0063] A reversible electric machine 30, including an electric motor capable of reversibly operating as a generator, is arranged at the end of the shaft, engaged with the first end of the turbine shaft 13, so that it can transmit power to the turbine shaft 13 by operating in motor mode, or extract mechanical power from the turbine shaft 13 by operating in generator mode. Moreover, the electric machine 30 arranged at the rear end of the turboprop engine 100 is therefore located in its thermodynamically cold region, in particular adjacent to the fresh air inlet 19 of the gas generator 12.

[0064] It should be understood that the thermodynamically cold region of the turboprop engine 100 corresponds to its upstream part in the flow direction of the gas flow F, in particular upstream of the combustion chamber 17, and that the thermodynamically hot region of the turboprop engine 100 corresponds to its downstream part, in particular at the level of the combustion chamber 17 and the hot gas injection nozzle F.

[0065] This arrangement of the electric machine 30 is advantageous in view of the considerable volume involved in a high-power electric machine 30 (from one kW to several hundred kW), and also in view of the difficulties of integrating such a device related to thermodynamic constraints in the thermal zone of the turboprop 100 .

[0066] Furthermore, given this architecture, all the equipment, in particular the electric machine 30 , the gas generator 12 , the free turbine 11 , the mechanical reducer 50 and the main rotor 60 are coaxial and centered on the same main axis X. This architecture makes it possible to limit the front part of the turboprop 100 while allowing a large number of functions to be performed, depending on the application envisaged. Figures 2 to 8 Describe these different functions.

[0067] It should generally be noted that for the sake of clarity, Figures 2 to 8 The different operating modes of the device are represented schematically in a functional and simplified manner, without representing all the details of those elements constituting the turboprop engine and the different power transmission members. In particular, the pinions and possible speed ratios are not shown.

[0068] Figure 2 Schematically showing the reverse orientation Figure 1 The turboprop 100, the propeller 62 is oriented towards the left in this figure. The rear part of the turboprop 100, in other words the thermodynamically cold area, comprises an accessory gearbox 20 known by the acronym "AGB". This gearbox comprises in particular a reversible electric machine 30 and different equipment, depending on the selected application.

[0069] In particular, Figure 2 represents an operating mode allowing switching between the gas generator 12 and the free turbine 11. More specifically, the reversible electric machine 30 is mechanically coupled to the generator shaft 14 of the gas generator 12 by means of a first deactivatable coupling device comprising a first free wheel 31 and a first speed adaptation reducer 33 preferably arranged between the electric machine 30 and the first free wheel 31.

[0070] The first freewheel 31 is mounted so that when the reversible motor 30 is operated as a motor (the first coupling device is actuated), the rotation of the reversible motor 30 can drive the generator shaft 14 in rotation, but conversely, the rotation of the generator shaft 14 cannot drive the reversible motor 30 in rotation (the first coupling device is deactivated). In other words, the first freewheel 31 can only transmit torque in the direction of the reversible motor 30 toward the gas generator 12, and not vice versa. Therefore, the rotation of the reversible motor 30 can drive the shaft 14 of the gas generator 12 in rotation in order to start the latter. When the gas generator 12 has been started, the reversible motor 30 no longer drives the gas generator 12 in rotation.

[0071] According to the invention, the reversible electric machine 30 can also advantageously be coupled to the turbine shaft 13 of the free turbine 11 by means of a second coupling device in such a way that the reversible electric machine 30 operating as a generator can be driven in rotation by the free turbine 11 in order to provide electric power. The second coupling device comprises a second free wheel 32 similar to the first free wheel 31, and a second speed adaptation reducer 34 arranged between the second free wheel 32 and the electric machine 30. The second speed adaptation reducer 34 has a reduction factor selected so that the speed of the reversible electric machine 30 is adapted to the speed range required to allow the supply of electric power. The second free wheel 32 is actually installed so that it can only transmit the rotational torque from the shaft 13 of the free turbine 11 to the electric machine 30.

[0072] In other words, thanks to the second freewheel 32, the reversible electric machine 30 can be driven by the free turbine 11 (the second coupling device is actuated), but cannot drive the latter in rotation (the second coupling device is deactivated). When the free turbine 11 drives the reversible electric machine 30 in rotation, the reversible electric machine operates as a generator and generates electricity.

[0073] The first and second freewheels 31, 32 are oppositely mounted. In this case, they have opposite engagement directions. Therefore, when the reversible electric machine 30 operating as a motor drives the shaft 14 of the gas generator 12 to rotate (the first freewheel 31 is engaged, that is, the first coupling device is actuated), the second freewheel 32 does not transmit the rotational torque of the reversible electric machine 30 to the shaft 13 of the free turbine 11 (the second coupling device is deactivated). Conversely, when the shaft 13 of the free turbine 11 drives the reversible electric machine 30 operating as a generator to rotate (the second freewheel 32 is engaged, that is, the second coupling device is actuated), the first freewheel 31 does not transmit the rotational torque of the reversible electric machine 30 to the shaft 14 of the gas generator 12 (the first coupling device is deactivated).

[0074] In this case, the gearbox 20 comprises a reversible electric machine 30, freewheels 31, 32 and speed-adapting reducers 33, 34. It will be noted that a similar function applied to a turbine engine is detailed in document FR 2 929 324, in which the electric machine and the mechanical reducer are arranged on the same side of the turbine engine, unlike the present invention in which the electric machine 30 and the mechanical reducer 50 are arranged at opposite ends of the turboprop 100.

[0075] Figure 31 represents an operating mode in which two reversible electric machines are used as an alternative to freewheels 31 and 32. In this case, the gearbox 20 comprises a reversible electric machine 30 as a first electric machine and also comprises a second reversible electric machine 40 coupled to the generator shaft 14. While the first electric machine 30 is a high-power electric machine, in particular several hundred kilowatts, the second electric machine 40 can be a common starter with a power of the order of 10 kW.

[0076] This configuration makes it possible to perform a large number of functions, in particular to assist the gas turbine 10 in some transient phases, by transferring power to the turbine shaft 13 or to the generator shaft 14, or during take-off, by drawing power from the battery pack, or generating electricity in flight to recharge the batteries. In addition, the power transfer between the two electric machines also makes it possible to advantageously vary the operating point of the turbine by internal hybridization. Figure 4 and 5 Examples of these functions are shown.

[0077] exist Figure 4 and Figure 5 In the diagram, the dashed arrow indicates the direction of mechanical or electrical power transfer between two elements. For example, in Figure 4 In the embodiment, mechanical power is transmitted from the first motor 30 to the turbine shaft 13 and from the generator shaft 14 to the second motor 40 , and electric power is transmitted from the second motor 40 to the first motor 30 .

[0078] Figure 4 represents, for example, an auxiliary mode of the gas generator 12 towards the turbine shaft 13. In this case, while the first electric machine 30 operates in motor mode by transmitting power to the turbine shaft 13, for example to assist the gas turbine during takeoff, the second electric machine 40 operates in generator mode by drawing power from the generator shaft 14 and by transmitting power to the first electric machine 30 via the electrical connection 90, in order to assist the first electric machine 30. Figure 4 and Figure 5 , the "Generator" mode is represented by a small lightning bolt.

[0079] Figure 5 Conversely, the auxiliary mode of the turbine shaft 13 towards the gas generator 12 is represented. In this case, while the second electric machine 40 operates in motor mode by transmitting power to the generator shaft 14, the first electric machine 30 operates in generator mode by extracting power from the turbine shaft 13 and by transmitting power to the second electric machine 40 via the electrical connection 90, for example, in order to change the operating point of the gas generator.

[0080] Alternatively, the second motor 40 may have a higher power, for example, equal to the power of the first motor 30. Figure 6, in which the second electrical machine 40 is mechanically coupled to the shaft 14 of the gas generator 12 via a first deactivatable coupling device and to the turbine shaft 13 via a second deactivatable coupling device.

[0081] The first deactivatable coupling device may specifically include a first freewheel 41, which is mounted so that when the second electric machine is operated in motor mode, the rotation of the second reversible electric machine 40 can drive the shaft 14 of the gas generator 12 to rotate, but when the second electric machine is operated in motor mode, the rotation of the shaft 14 of the gas generator 12 cannot drive the second reversible electric machine 40 if the first freewheel 41 is not blocked. In other words, the first freewheel 41 can only transmit a rotational torque in the direction of the second electric machine 40 toward the gas generator 12, but not vice versa.

[0082] However, if the first free wheel 41 is a blockable wheel, blocking of this wheel allows the generator shaft 14 to drive the second electric machine 40 so that it operates, with the rotor stopped, in generator mode for an "APU" mode, for example, an operating mode in which the gas turbine drives the generator without driving the main rotor, in order to ensure the power supply of electrical devices on the ground, such as batteries, flight equipment, heating or air conditioning.

[0083] The second deactuable coupling device can in particular comprise a second freewheel 42 , so that the second electrical machine 40 operating in motor mode can drive the turbine shaft 13 in rotation.

[0084] The second reversible motor 40 is capable of rotating in a first rotational direction (conventionally, a positive direction) and a second rotational direction (conventionally, a negative direction), in which the second reversible motor is mechanically coupled to the shaft 14 of the gas generator 12 via a first free wheel 41, and in the second rotational direction, which is opposite to the first rotational direction, the second reversible motor is mechanically coupled to the turbine shaft 13 via a second free wheel 42.

[0085] Specifically, Figure 6 The elements indicated by "-1" in the following figures represent gears, such as pinions, that allow the direction of rotation to be reversed. It will therefore be understood that when the second motor 40 rotates in the positive direction, the first deactivatable coupling device is actuated and the second coupling device is deactivated, and when the second motor 40 rotates in the negative direction, the first deactivatable coupling device is deactivated and the second coupling device is actuated.

[0086] In this case, the second reversible electric machine 40 is constituted by an electric motor capable of reversibly operating as a generator. To this end, either the first freewheel 41 or the second freewheel 42 can be blocked by a blocking device so as to be driven in rotation by the main rotor 60 or by the gas generator 12 and thus generate electricity. This electricity generated by the second electric machine 40 can then be transmitted to other elements of the turboprop engine 100, for example to a "battery pack" (not shown) or can be exchanged between the electric machines 30, 40 to achieve internal hybridization.

[0087] In particular, according to this configuration, a number of functions can be performed. For example, the second electric machine 40 can be used to perform a rapid start of the gas turbine 10 by rotating in the positive direction, and also to inject power into the turbine shaft 13 by rotating in the negative direction, in particular in the ramp-up phase, in order to supplement the power delivered by the first electric machine 30.

[0088] Furthermore, when the gas generator 12 operates autonomously and is no longer driven by the second motor 40, the first motor 30 can operate in generator mode by being driven by the turbine shaft 13. Thus, the electricity generated by the first motor 30 can be used to power onboard electrical accessories or charge the battery.

[0089] The first electric machine 30 and the second electric machine 40 can also transmit power to the main rotor 60 by both operating in motor mode. The second electric machine 40 then rotates in the negative direction. This configuration can be used in some flight phases where additional power transmission is required, for example, during takeoff. The first electric machine 30 and the second electric machine 40 thus make it possible to supplement the power transmitted to the main rotor 60 by the free turbine 11.

[0090] Furthermore, the first electric machine 30 can be operated in generator mode and allow power to be transmitted to the gas generator 12 via the second electric machine 40, which then rotates in the positive direction. This configuration can be useful in some flight phases, for example to assist the gas generator during rapid acceleration, or to modify the engine operating point in "high altitude-hot weather" flight use conditions.

[0091] It is also possible to transmit power to the main rotor 60 through the first electric machine 30 and to deliver power to the gas generator 12 through the second electric machine 40, the first electric machine and the second electric machine each operating in motor mode. The second electric machine 40 then rotates in the positive direction. This allows in particular to help fast transients, wherein the first electric machine 30 helps the main rotor 60 to limit the rotation drop, while the second electric machine 40 helps the gas generator 12 to improve the power availability time on the free turbine 11.

[0092] It is also possible to restart the gas turbine 10 in flight in the event of its shutdown. After detecting the shutdown of the turboprop engine, the first electric machine 30 operates in motor mode to provide emergency power to the main rotor 60. Then, the speed of the gas generator 12 is reduced to the ignition window, allowing the turboprop engine to be restarted. At the same time, the second electric machine 40 can advantageously rotate in the positive direction at a speed slightly lower than the re-ignition speed. This saves time and facilitates the resynchronization of the second free wheel 42. When the ignition window is reached, the second electric machine 40 rotating in the positive direction then drives the gas generator 12 via the first free wheel 41, making it possible to restart the gas turbine 10.

[0093] This architecture is particularly advantageous since it allows the main rotor 60 to be powered by only two electric machines, through the first electric machine 30 and the second electric machine 40, while allowing, for example, restarting the gas turbine 10 in some operating phases through the second electric machine 40, and allowing internal hybridization for high and hot flights. It should also be noted that the various steps described above can be implemented by a monitoring unit (not shown), making it possible to detect the shutdown of the engine, the rotation speed of the shafts of the gas generator and the free turbine, and monitoring the electric machines.

[0094] Figure 7 An alternative embodiment of the architecture according to the invention is shown, in which the gearbox 20 comprises a single reversible electric machine 30 which, when rotating in the positive direction, drives the generator shaft 14 in rotation via a first freewheel 31 and, when rotating in the negative direction, drives the turbine shaft 13 via a second freewheel 32. This configuration makes it possible to perform most of the functions described above, in addition to internal hybridization. In this configuration, at least one of the two freewheels 31, 32 can be blocked to allow the power generation function.

[0095] Figure 8 Represents something like Figure 7 An embodiment of the architecture of an embodiment of an embodiment in which a rotor brake 70 is arranged between the electric machine 30 and the second free wheel 32. The rotor brake 70 is movable between a braking position preventing the propeller 62 and the free turbine 11 from rotating and a free position allowing the propeller 62 and the free turbine 11 to rotate. The rotor brake 70 thus makes it possible to block the free turbine 11 and, therefore, the main rotor 60, in particular in the case of starting with strong winds. The presence of a through-turbine shaft 13 makes it possible to position this rotor brake 70 in a thermodynamically cold region to the rear of the turboprop 100, on the first end side of the turbine shaft 13.

[0096] Although the invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these embodiments without departing from the general scope of the invention as defined by the claims. In particular, the use of a stopperable or non-stopperable freewheel may be replaced by any active coupling device, such as a stopper or a clutch. In particular, individual features of the different embodiments illustrated / mentioned may be combined in further embodiments. Therefore, the description and the drawings must be considered in an illustrative and not restrictive sense.

Claims

1. A turbine (100) for a hybrid aircraft, the turbine comprising: A gas generator (12) carried by a generator shaft (14), at least one free turbine (11) carried by a turbine shaft (13) and driven in rotation by the gas flow generated by the gas generator (12), a main rotor (60) including a propeller (62), and at least one reversible electric machine (30), the turbine shaft (13) being a through shaft extending axially between a first end engaged with the electric machine (30) upstream of the gas generator (12) and a second end engaged with the main rotor (60) downstream of the gas generator (12).

2. The turbine (100) according to claim 1, wherein: The gas generator (12) comprises a compressor (15) and an air inlet (19) configured to supply fresh air to the compressor (15), and a first end of a turbine shaft (13) engaged with an electric motor (30) is arranged adjacent to the air inlet (19).

3. The turboprop engine (100) according to claim 1 or 2, wherein: The second end of the turbine shaft (13) is engaged with the main rotor (60) via a mechanical reducer (50) arranged between the free turbine (11) and the main rotor (60).

4. The turbine (100) according to any one of claims 1 to 3, comprising a combustion chamber (17), the second end of the turbine shaft (13) being engaged with a main rotor (60) downstream of the combustion chamber (17).

5. The turbine (100) according to any one of claims 1 to 4, wherein: The motor (30) is directly coupled to the first end of the turbine shaft (13) so as to rotate at the same speed as the turbine shaft (13).

6. The turbine (100) according to any one of claims 1 to 4, wherein: The electric motor (30) is coupled to the first end of the turbine shaft (13) via a speed adaption reducer (33, 34).

7. The turbine (100) according to any one of claims 1 to 6, wherein: The electric machine (30) can be coupled to the generator shaft (14) in order to rotate the gas generator (12) during the starting phase of the turboprop engine (100) and can be coupled to the turbine shaft (13) after the starting phase in order to generate electricity.

8. The turbine (100) according to claim 7, wherein: The electric motor (30) is coupled to the generator shaft (14) via a first freewheel (31) configured to transmit a rotational torque from the electric motor (30), and the electric motor is coupled to the turbine shaft (13) via a second freewheel (32) configured to transmit a rotational torque to the electric motor (30).

9. The turbine (100) according to any one of claims 1 to 6, wherein: The electric machine (30) is a first reversible electric machine, and the turbine engine (100) further comprises a second reversible electric machine (40) which is engaged with the generator shaft (14) and is capable of exchanging electric power with the first reversible electric machine (30).

10. The turbine (100) according to claim 9, wherein: The first electric machine (30) is configured to operate in a generator mode or a motor mode. In the generator mode, the first electric machine can be driven to rotate by the turbine shaft (13) to generate electricity. In the motor mode, the first electric machine can transmit power to the turbine shaft (13).

11. The turbine (100) according to claim 9 or 10, wherein: The second electric machine (40) is coupleable to the generator shaft (14) via first deactivatable coupling means (41) and is coupleable to the turbine shaft (13) via second deactivatable coupling means (42).

12. The turbine (100) according to claim 11, wherein: At least one of the first releasably actuatable coupling device and the second releasably actuatable coupling device (41, 42) is a freewheel, the first releasably actuatable coupling device (41) being configured to be actuated when the second motor (40) rotates in a first rotational direction, and the second releasably actuatable coupling device (42) being configured to be actuated when the second motor (40) rotates in a second rotational direction opposite to the first rotational direction.

13. The turbine (100) according to any one of claims 1 to 12, comprising a rotor brake (70) which is movable between a braking position preventing the main rotor (60) from rotating and a free position allowing the main rotor (60) to rotate, the rotor brake being arranged upstream of the gas generator (12).

14. A hybrid aircraft comprising a turbine (100) according to any one of the preceding claims.

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