Improved turbomachine for a hybrid aircraft

Abstract

The invention relates to a turbomachine (100) for a hybrid aircraft, the turbomachine comprising a gas generator (12) carried by a generator shaft (14), at least one free turbine (11) carried by a turbine shaft (13) and rotated by a 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

Description Title of the invention: IMPROVED TURBOMACHINE FOR HYBRID AIRCRAFT Technical Field

[0001] The present invention relates to the field of hybrid aircraft, comprising at least one turbomachine for flying machines, such as a turboprop for an airplane or a turboshaft engine for a helicopter. In particular, the invention relates to a turbomachine for a hybrid aircraft, and to a hybrid aircraft comprising such a turbomachine. Previous technique

[0002] A turbomachine, such as a turboshaft engine or turboprop, for a helicopter or airplane, is known to consist of a gas turbine with a gas generator and a free turbine driven by the gas flow generated by the gas generator. The free turbine is completely independent of the gas generator, which comprises one or two compressors (high and low pressure) and one or two turbines (high and low pressure). Specifically, the shaft of the free turbine and the shaft of the gas generator (carrying the compressor(s) and turbine(s)) are not connected. The free turbine is therefore distinct from the turbine(s) (high and low pressure) mounted on the gas generator shaft, which are connected to the compressor. Thus, the defining characteristic of a free turbine turboprop lies in the separation of the "engine" (gas generator) and "power turbine" (or free turbine) components.In addition, an aircraft generally includes, besides this turbomachine, a reversible electric machine coupled to the gas generator, so as to rotate the gas generator during a start-up phase of the turbomachine, or in flight so as to ensure the non-propulsive electrical needs of the aircraft.

[0003] Traditionally, a gas generator consists of at least one compressor and one turbine coupled in rotation. The operating principle is as follows: fresh air entering the gas turbine is compressed by the compressor's rotation before being sent to a combustion chamber where it is mixed with fuel. The exhaust gases from combustion are then expelled at high speed. A first expansion occurs in the gas generator's turbine, during which it extracts the energy necessary to drive the compressor. The gas generator's turbine does not absorb all the kinetic energy of the exhaust gases; the excess kinetic energy corresponds to the gas flow generated by the gas generator.The latter therefore provides kinetic energy to the free turbine so that a second expansion occurs in the free turbine which transforms this kinetic energy into mechanical energy in order to drive a receiving organ, such as a turboprop propeller.

[0004] During the turbomachine's start-up phase, it is necessary to rotate the gas generator, that is, to rotate the compressor coupled to the turbine. As mentioned above, this is precisely one of the roles of the reversible electric machine, which is most often an electric motor capable of operating reversibly as an electric generator.

[0005] Indeed, aircraft, in which such turbomachines are intended to be integrated, contain electrical equipment that requires a power supply. The reversible electric machine is used to provide electricity to this equipment. To do this, the electric machine, now operating as an electric generator, is driven in rotation by the gas generator; the mechanical energy from the gas generator is converted into electrical energy by the machine. Furthermore, the electric machine can be used for internal hybridization, for example, by providing additional power to the propeller shaft or the engine shaft, or by generating power from the free turbine shaft without affecting the performance of the gas generator.

[0006] To perform these functions, the electrical machine(s) must be sized to a power output far exceeding that of the generators / starters usually used, typically one or more hundred kilowatts, instead of around ten kilowatts. It is therefore advisable to combine the two types of electrical machines (the turbine generator / starter and the electric machine connected to the rotor).

[0007] However, existing architectures do not allow electric machines to perform certain functions. Furthermore, these high-power electric machines present challenges in terms of size. For example, some turboprop architectures are characterized by a rear intake at the level of the free turbines and hot exhaust nozzles to drive the turboprop gearbox and propeller, and by an accessory gearbox in the cold section opposite the engine to drive the equipment.

[0008] However, integrating a high-power, and necessarily bulky, electric motor into such an architecture is difficult. Indeed, installing an electric motor driven at high speed by the turbines in the hot section, under the nozzle, would present challenges in terms of integration, maintainability, and thermal environment. The only feasible solution is therefore to drive the electric motor in the cold section, specifically at the accessory gearbox, thus impacting the gas turbine's performance when drawing power from the gas generator. This significantly increases the engine's fuel consumption. Furthermore, this increased consumption impacts the device's endurance, which is crucial in applications such as drones.

[0009] Other types of architectures exist, notably when the accessory gearbox and the mechanical propeller reduction gear are both on the same side of the engine, placing the electric machine in a cold zone near the propeller cone. These architectures, however, require increasing the turbomachine's frontal area by offsetting (in other words, creating an "offset") the propeller axis relative to the engine's main axis using a mechanical reduction gear, and / or compacting its centering, and limiting the possibilities of sharing functions between the turbine generator / starter and the high-power electrical machine.

[0010] Therefore, there is a need for an architecture that addresses at least some of the aforementioned drawbacks. Description of the invention

[0011] The present presentation relates to a hybrid aircraft turbomachine, comprising a gas generator carried by a generator shaft, at least one free turbine carried by a 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 through and extending axially between a first end in contact with the electric machine, and a second end in contact with the main rotor.

[0012] The turbomachine can be a turboshaft engine or a turboprop. In the following description, we will primarily refer to a turboprop. The main rotor can be a propeller. The aircraft, particularly an airplane, provides propulsion, with the propeller located at one end of the turboprop, preferably at the front end when considering the aircraft's normal direction of travel. The main rotor is thus free to rotate around an axis, which preferably corresponds to the main axis of the turboprop.

[0013] By "through," we mean that the turbine shaft extends axially along the main axis of the turboprop engine, on both sides of it. The turbine shaft thus passes through the high-pressure turbine, the combustion chamber, and the compressor on one side, and the exhaust nozzle on the other. The turbine shaft therefore passes through the thermally cool section, which includes the air intake and the compressor, and the thermally hot section, where temperatures are higher than in the cool section, which includes the combustion chamber and the nozzle. The rotors of this turboprop engine are specifically configured to allow the turbine shaft to pass through them. Furthermore, Preferably, the generator shaft and the turbine shaft are concentric, with the turbine shaft passing through the inside of the generator shaft. This means that the turbine shaft is completely independent of the generator shaft and the compressor(s) it supports.

[0014] Furthermore, the term "engaged with" means that the first end of the turbine shaft is mechanically connected to the electric machine, either directly or indirectly. Thus, the reversible electric machine can drive the turbine shaft in rotation, and conversely, can be driven by the turbine shaft to generate electricity. Similarly, the second end of the turbine shaft is mechanically connected to the main rotor, for example, the propeller, either directly or via a mechanical gearbox.

[0015] Unlike configurations in which the electric machine is located at the accessory box in the cold part, drawing energy from the generator shaft, this architecture, which includes a through turbine shaft, allows the electric machine, in contact with the turbine shaft, to draw energy from the latter, thus limiting the impact on the performance of the gas turbine and on the consumption of the engine.

[0016] Furthermore, this architecture, in which the through-shaft turbine is engaged at both ends—specifically, at its first end with the electric motor and at its second end with the main rotor—allows for a large number of functions to be performed while preferentially maintaining an alignment of the various turboprop components along the same axis, thus limiting the turboprop's frontal area. This configuration notably reduces the turboprop's drag.

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

[0018] In other words, the electric machine is located in the thermally cool part of the turboprop. This makes it easier to integrate the electric machine into the turboprop and improves its maintainability, unlike hotter thermal environments such as under the hot exhaust nozzle on the turbine side.

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

[0020] Unlike a helicopter turboshaft engine application, where the mechanical gearbox and the electric machine are each located on the same side of the gas generator, here they are positioned at opposite ends of the turbine shaft. The electric machine is located at the first end of the turbine shaft, preferably in the colder section, while the mechanical gearbox can be located at the second end, in the hotter section. This allows the electric machine to be kept in a cool thermal environment to improve its reliability, enhances modularity for maintenance, reduces the frontal area of ​​the hybrid turbomachine to improve the aircraft's aerodynamics, and minimizes the impact of the electric machine's center of gravity.

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

[0022] It is understood that the terms "upstream" and "downstream" are defined in relation to the normal direction of gas flow in the turbomachine. In other words, the inlet between the second end of the turbine shaft and the main rotor is located in the thermally hot part of the turbomachine, after the gases have passed through the combustion chamber.

[0023] In some embodiments, the second end of the turbine shaft is engaged with the main rotor in the vicinity of the chamber. combustion and a hot gas ejection nozzle. Preferably, the connection between the second end of the turbine shaft and the main rotor is located opposite the ejection nozzle.

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

[0025] The electric machine, for example with high power density, tends to rotate at speeds comparable to free turbines, and can, for example, be attached directly to the first end of the turbine shaft. This reduces the number of assembly parts required, thus simplifying the turboprop architecture.

[0026] In some embodiments, the electric machine is engaged with the first end of the turbine shaft via a speed-adaptive reducer.

[0027] When the free-spinning turbine cannot directly drive the electric machine, depending on the latter's sizing, the speed-matching gearbox allows the electric machine's rotational speed to be adapted to that of the free-spinning turbine. This makes it possible to separate the optimal sizing of the free-spinning turbine from that of the electric machine.

[0028] In some embodiments, the electric machine is able to be coupled to the generator shaft so as to rotate the gas generator during a start-up phase of the turbomachine, and is able to be coupled to the turbine shaft after the start-up phase in order to generate electrical power.

[0029] This configuration allows the gas turbine to be started by injecting power into the gas generator using the electric machine. Then, when the gas generator speed exceeds a predetermined threshold, the turbine shaft drives the electric machine, which then generates electrical power. This makes it possible to achieve high power generation by drawing power from the turbine shaft without compromising the turbine's performance. gas turbine. This configuration is particularly advantageous for non-hybridized applications requiring high electrical generation, such as applications using drones for example.

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

[0031] It is understood that the first and second freewheels are mounted in opposition. By "mounted in opposition," it is understood that the first freewheel can transmit a rotational torque from the electric machine, but not the other way around, while the second freewheel can transmit a rotational torque to the electric machine, but not the other way around. Preferably, the electric machine is coupled to the generator shaft via the first freewheel and a first speed-matching gearbox, and is coupled to the turbine shaft via the second freewheel and a second speed-matching gearbox. The reduction ratios of the first and second speed-matching gearboxes are determined such that, after the gas generator starts, the first freewheel is desynchronized and the second freewheel is synchronized.

[0032] Freewheels offer the advantage of not requiring electronic or mechanical control by an external operator. Furthermore, they exhibit high reliability. Such a freewheel generally consists of a hub and a peripheral ring mounted to rotate on the hub. The hub can usually drive the peripheral ring, but not the other way around. It should be noted that in some cases, the freewheel is arranged so that the peripheral ring can drive the hub, but not the other way around, without affecting the principle of the present invention. Therefore, the hub can only drive the ring when the hub rotates in a predetermined direction relative to the ring. will be called "direction of engagement". 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, the turbomachine further comprising a second reversible electric machine in contact with the generator shaft, and capable of exchanging electrical power with the first reversible electric machine.

[0034] The first electric machine in contact with the first end of the turbine shaft is then preferably a high-power electric machine, on the order of one or several hundred kilowatts, while the second electric machine is preferably low-power, on the order of 10kW, such as a generator / starter usually used.

[0035] In this configuration, while the second electric machine is used to start the gas turbine, the first electric machine can be used with the generator / starter to achieve internal hybridization. This involves power exchange between the electric machines to limit the aging of the gas turbine by transferring power between the gas generator body and the free turbine. This configuration also allows for the implementation of all desired functions, including power transfer assistance to the turbine shaft or generator shaft during certain transient phases, assistance to the gas turbine during takeoff, and in-flight electricity generation to recharge the batteries.

[0036] In some embodiments, the first electric machine is configured to operate in generator mode, in which it is capable of being driven in rotation by the turbine shaft so as to generate electrical power, or in motor mode in which it is capable of supplying power to the turbine shaft.

[0037] In other words, in engine mode, the first electric machine is capable of supplying power to the propeller in the case of a turboprop, or to the power take-off in the case of a turboshaft engine. The first electric machine can thus generate electrical power without drawing any energy. Power is supplied to the gas generator, which improves the specific fuel consumption of the gas turbine. Furthermore, the engine mode provides power to the turbine shaft during certain flight phases that require it, such as takeoff, transitional phases, or maneuvers.

[0038] In some embodiments, the second electrical machine is able to be coupled to the generator shaft via a first switchable coupling means, and to be coupled to the turbine shaft via a second switchable coupling means.

[0039] In some embodiments, at least one of the first and second switchable coupling means is a freewheel, preferably lockable, the first switchable coupling means being configured to be activated when the second electric machine rotates in a first direction of rotation, and the second switchable coupling means being configured to be activated when the second electric machine rotates in a second direction of rotation opposite to the first direction of rotation.

[0040] By "switchable coupling means," it is understood that the coupling means can be in an activated position in which the components connected to said coupling means are coupled, or in a deactivated position in which said components are decoupled, it being understood that "component" means the electrical machines, the main rotor, the gas generator, and the free turbine. Switchable coupling means may, in particular, include a freewheel.

[0041] Given this configuration, a large number of functions can be performed, including internal hybridization. More specifically, the second electric machine can provide power from the free turbine, for example by blocking the second switchable coupling, so as not to affect the performance of the gas generator, or it can inject power onto the turbine shaft, and therefore onto the main rotor, to assist it during certain 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 the opposite direction to be mechanically coupled to the turbine shaft and thus to the main rotor. Specifically, the second electric machine rotating in the first direction allows coupling with the gas generator to start it on the ground, but also to supplement the thermodynamic power during certain flight phases, for example, to assist with transient phases or to modify the engine operating point.

[0043] The second electric motor, rotating in the first direction, also allows the gas generator to be restarted in flight, for example, following a failure, without requiring the activation of another mechanical component such as a clutch. Furthermore, the second electric motor, rotating in the opposite direction, drives the main rotor during certain flight phases requiring additional power.

[0044] Therefore, the architecture described herein has the advantage of being simple by limiting the number of components and connections, while allowing a high number of functions to be performed, including internal hybridization, and thus improving the reliability of the device.

[0045] In some embodiments, the turbomachine includes a rotor brake, movable between a braking position, preventing the rotation of the main rotor, and a free position allowing the rotation of the main rotor, the rotor brake being located upstream of the gas generator. In other words, the propeller braking system is located not on the propeller reduction gear side, but on the opposite side of the turbomachine, in its cold section. It should be noted that the rotor braking function can be provided by a lockable freewheel.

[0046] This presentation also relates to a hybrid aircraft comprising a turbomachine according to any of the preceding embodiments. The hybrid aircraft may be an airplane, and the turbomachine may be a turboprop.

[0047] The term "hybrid aircraft" refers to an aircraft comprising a thermal engine capable of driving a main rotor in rotation, and at least one electric machine capable of providing power to the thermal engine. Brief description of the drawings

[0048] The invention and its advantages will be better understood upon reading the detailed description below of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figure pages, on which:

[0049] [Fig. 1] Figure 1 shows a cross-sectional view of a hybridized aircraft turboprop according to the invention,

[0050] [Fig. 2] Figure 2 schematically represents the turboprop engine of Figure 1 according to a first embodiment,

[0051] [Fig. 3] Figure 3 represents the propulsion system of Figure 1, according to a second embodiment,

[0052] [Fig. 4] Figure 4 represents the propulsion system of Figure 1, according to a first operating mode of the second embodiment,

[0053] [Fig. 5] Figure 5 represents the propulsion system of Figure 1, according to a second operating mode of the second embodiment,

[0054] [Fig. 6] Figure 6 represents the propulsion system of Figure 1, according to a third embodiment,

[0055] [Fig. 7] Figure 7 represents the propulsion system of Figure 1, according to a fourth embodiment,

[0056] [Fig. 8] Figure 8 represents the propulsion assembly of Figure 1, according to a fifth embodiment. Description of the implementation methods

[0057] An architecture of a turbomachine, in this example of a turboprop 100 according to different embodiments of the invention will be described in the following description, with reference to figures 1 to 8.

[0058] Figure 1 schematically represents a turboprop 100 of an aircraft, driving in rotation the main rotor 60 of an aircraft comprising 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 suitable for being driven into rotation by a 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. Thus, the turbine shaft 13 is through-shaft, and extends between a first end, conventionally named rear end (on the left in Figure 1), and a second end, conventionally named front end (on the right in Figure 1), passing through the gas generator 12 and the free turbine 11.

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

[0061] The gas generator 12 comprises a rotating generator shaft 14 on which are mounted at least one centrifugal compressor 15 and at least one turbine 16, as well as a combustion chamber 17 arranged axially between the compressor 15 and the turbine 16 when the gas generator 12 is considered along the axial direction of the generator shaft 14. The gas turbine 10 has a casing 18 equipped with an air inlet 19 through which fresh air enters the gas generator 12. After its admission into the enclosure of the gas generator 12, the fresh air is compressed by the compressor 15 which forces it towards the inlet of the combustion chamber 17 where it is mixed with fuel. The combustion which takes place in the combustion chamber 17 causes the burnt gases to be evacuated at high speed towards the turbine 16, which in turn causes the shaft 14 of the gas generator 12 to rotate and, consequently, the compressor 15.The rotational speed of the shaft 14 of the gas generator 12 is determined by the fuel flow rate entering the combustion chamber 17. The turboprop 100 being of the free turbine type,. It will therefore be understood that the generator shaft 14 is independent of the turbine shaft 13. In other words, the free turbine 11 and the turbine shaft 13 are totally independent of the generator shaft 14 and the compressor 15, unlike the turbine 16 which is linked to the compressor 15.

[0062] Despite the extraction of kinetic energy by turbine 16, the gas flow exiting the gas generator possesses significant kinetic energy. As can be seen from Figure 1, the gas flow F is directed towards the free turbine 11, which causes an expansion in the free turbine 11, leading to the rotation of the turbine wheel and the turbine shaft 13.

[0063] The reversible electric machine 30, comprising an electric motor capable of reversibly operating as an electric generator, is arranged at the end of the shaft, meshing with the first end of the turbine shaft 13, such that it can supply power to the turbine shaft 13 when operating in motor mode, or extract mechanical power from the turbine shaft 13 when operating in generator mode. Furthermore, the electric machine 30, located at the rear end of the turboprop 100, is thus situated in a thermally cooled part thereof, specifically adjacent to the fresh air inlet 19 of the gas generator 12.

[0064] It is understood that the thermally cold part of the turboprop 100 corresponds to the upstream part of it according to the direction of flow of the gas flow F, in particular upstream of the combustion chamber 17, and the thermally hot part of the turboprop 100 corresponds to the downstream part of it, in particular at the level of the combustion chamber 17 and the hot gas ejection nozzle F.

[0065] This arrangement of the electric machine 30 is advantageous given the significant size involved by the high-power electric machine 30 (one to several hundred kilowatts), and also given the difficulties of integrating such equipment due to thermal constraints in the hot part of the turboprop 100.

[0066] Furthermore, given this architecture, all the equipment, including the electric machine 30, the gas generator 12, the free turbine 11, the mechanical gearbox 50, and the main rotor 60, are coaxial and centered on the same main axis X. This architecture makes it possible to limit the frontal area of ​​the turboprop 100, while still allowing for a large number of functions, depending on the intended applications. These various functions are described below with reference to Figures 2 to 8.

[0067] It should be noted that, for the sake of clarity, Figures 2 to 8 schematically and functionally represent the different operating modes of the device, without showing all the details of the components of the turboprop engine and the various power transmission elements. In particular, the gears and any speed ratios are not shown.

[0068] Figure 2 schematically represents the turboprop 100 of Figure 1, in an inverted orientation, with the propeller 62 facing left in this figure. The rear section of the turboprop 100, i.e., the thermally cooled section, includes an accessory gearbox 20, known by the acronym "AGB" (for "Accessory GearBox"). This gearbox includes, in particular, the reversible electric motor 30 and various other equipment, depending on the 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 first switchable coupling means, comprising a first free wheel 31 and, preferably, a first speed adaptation reducer 33 disposed between the electric machine 30 and the first free wheel 31.

[0070] The first freewheel 31 is mounted such that the rotation of the reversible electric machine 30 can drive the generator shaft 14 in rotation when the reversible electric machine 30 is operating as an electric motor (first coupling means activated), but conversely, the rotation of the shaft The generator 14 cannot rotate the reversible electric machine 30 (first coupling means deactivated). In other words, the first freewheel 31 can only transfer rotational torque from the reversible electric machine 30 to the gas generator 12, and not the other way around. Thus, the rotation of the reversible electric machine 30 is capable of rotating the shaft 14 of the gas generator 12 in order to start the latter. Once the gas generator 12 has started, the reversible electric machine 30 no longer rotates the gas generator 12.

[0071] According to the invention, the reversible electric machine 30 is also suitable for coupling to the turbine shaft 13 of the free turbine 11, advantageously by means of second coupling means, such that said reversible electric machine 30, operating as an electric generator, is suitable for being driven in rotation by the free turbine 11 in order to supply electricity. The second coupling means comprise a second free wheel 32, similar to the first free wheel 31, and a second speed-matching gearbox 34 disposed between the second free wheel 32 and the electric machine 30. This second speed-matching gearbox 34 has a reduction ratio chosen such that the speed of the reversible electric machine 30 is adapted to the speed range required to enable the supply of electricity.The second free wheel 32 is indeed mounted in such a way that it can transmit a rotational torque only 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 (second coupling means activated) but cannot rotate the latter (second coupling means deactivated). When the free turbine 11 rotates the reversible electric machine 30, the latter operates as an electric generator and produces electricity.

[0073] The first and second freewheels 31, 32 are mounted in opposition. In this case, they have opposite directions of engagement. Thus, when the reversible electric machine 30, operating as a motor, drives the rotation When the shaft 14 of the gas generator 12 is engaged (first freewheel 31, i.e., first coupling means activated), 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 (second coupling means deactivated). Conversely, when the shaft 13 of the free turbine 11 drives the reversible electric machine 30 operating as an electric generator (second freewheel 32 engaged, i.e., second coupling means activated), 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 (first coupling means deactivated).

[0074] In this case, the housing 20 includes the reversible electric machine 30, the free wheels 31, 32 and the speed adaptation reducers 33, 34. It should be noted that a similar function is detailed in document FR2929324 applied to a turboshaft engine, in which the electric machine and the mechanical reducer are arranged on the same side of the turboshaft engine, unlike the present invention where the electric machine 30 and the mechanical reducer 50 are arranged at opposite ends of the turboprop 100.

[0075] Figure 3 represents an operating mode in which two reversible electric machines are used, replacing the free wheels 31 and 32. In this case, the housing 20 includes the reversible electric machine 30, which is a first electric machine, and also includes 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 commonly used starter, with a power of around 10kW.

[0076] This configuration allows for a wide range of functions, including power transfer assistance to the turbine shaft 13 or generator shaft 14 during certain transient phases, assistance to the gas turbine 10 during takeoff by drawing power from a battery pack, and in-flight electricity generation to recharge the batteries. Furthermore, the power transfer between the two electric machines allows also to advantageously change the operating point of the turbomachine through internal hybridization. Figures 4 and 5 illustrate examples of these functions.

[0077] In Figures 4 and 5, the dashed arrows represent the direction of mechanical or electrical power transmission between two elements. In Figure 4, for example, mechanical power is transmitted from the first electric machine 30 to the turbine shaft 13, and from the generator shaft 14 to the second electric machine 40, and electrical power is transmitted from the second electric machine 40 to the first electric machine 30.

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

[0079] Figure 5 represents conversely a mode of assistance of the turbine shaft 13 to the gas generator 12. In this case, while the second electric machine 40 operates in motor mode by supplying power to the generator shaft 14, the first electric machine 30 operates in generator mode by taking power from the turbine shaft 13, and transferring electrical power to the second electric machine 40 via the electrical connection 90, so as to modify the operating point of the gas generator for example.

[0080] Alternatively, the second electric machine 40 can have a higher power output, for example equivalent to that of the first electric machine 30. This mode of operation is shown in Figure 6, in which the second electric machine 40 is mechanically coupled to the shaft 14 of the gas generator 12 via a first switchable coupling means, and is mechanically coupled to the turbine shaft 13 via a second switchable coupling means.

[0081] The first switchable coupling means may include a first freewheel 41 mounted such that the rotation of the second reversible electric machine 40 can drive the shaft 14 of the gas generator 12 when the second electric machine is operating in electric motor mode, but conversely, 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 locked. In other words, the first freewheel 41 can only transfer rotational torque from the second electric machine 40 to the gas generator 12, but not the other way around.

[0082] However, if the first free wheel 41 is a lockable wheel, locking this wheel then allows the generator shaft 14 to drive the second electric machine 40 so that it operates in generator mode for "AP U" modes with the rotor stopped, for example, the "AP U" mode (acronym for "Auxiliary Power Unit" in English) being an operating mode where the gas turbine drives an electric generator without driving the main rotor, to ensure the supply of electrical devices on the ground, such as batteries, flight equipment, heating or air conditioning.

[0083] The second switchable coupling means may in particular include a second free wheel 42, such that the second electric machine 40, operating in motor mode, is able to drive the turbine shaft 13 in rotation.

[0084] The second reversible electric machine 40 is capable of rotating in a first direction of rotation (by convention, a positive direction) in which it is mechanically coupled to the shaft 14 of the gas generator 12 via the first freewheel 41, and in a second direction of rotation (by convention, a negative direction), opposite to the first direction of rotation, in which It is mechanically coupled to the turbine shaft 13 via the second freewheel 42.

[0085] In particular, the element represented by "-1" in Figure 6 and the following figures represents gears, for example pinions, allowing the direction of rotation to be reversed. It will thus be understood that when the second electrical machine 40 rotates in the positive direction, the first switchable coupling means is activated, and the second coupling means is deactivated; and when the second electrical machine 40 rotates in the negative direction, the first switchable coupling means is deactivated, and the second coupling means is activated.

[0086] The second reversible electric machine 40 consists of an electric motor capable of operating reversibly as an electric generator. To achieve this, either the first freewheel 41 or the second freewheel 42 can be locked by means of a locking mechanism, allowing it to be driven in rotation by the main rotor 60 or by the gas generator 12, and thus generate electrical power. This electrical power generated by the second electric machine 40 can then be transferred to other components of the turboprop 100, for example to a battery pack (not shown), or can be exchanged between the electric machines 30 and 40 to achieve internal hybridization.

[0087] In particular, according to this configuration, it is possible to perform a number of functions. 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 onto the turbine shaft 13 by rotating in the negative direction, particularly during the upstroke phase, so as to supplement the power supplied by the first electric machine 30.

[0088] Furthermore, when the gas generator 12 operates autonomously and is no longer driven by the second electric machine 40, the first electric machine 30 can operate in electric generator mode by being driven by the turbine shaft 13. The electrical power thus generated by the first 30 electric machine 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 supply power to the main rotor 60 by both operating in electric motor mode. The second electric machine 40 then rotates in the negative direction. This configuration can be useful during certain flight phases requiring additional power, for example, during takeoff. The first electric machine 30 and the second electric machine 40 thus supplement the power supplied to the main rotor 60 by the free turbine 11.

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

[0091] It is also possible to supply power simultaneously to the main rotor 60 by the first electric machine 30, and to the gas generator 12 by the second electric machine 40, each operating in electric motor mode. The second electric machine 40 then rotates in the positive direction. This allows, in particular, for assistance during rapid transients, in which the first electric machine 30 assists the main rotor 60 to limit the speed drop, while the second electric machine 40 assists the gas generator 12 to improve the power availability time on the free turbine 11.

[0092] A restart of the gas turbine 10 in flight, in the event of its shutdown, is also possible. Immediately after the turboprop shutdown is detected, the first electric machine 30 operates in electric motor mode to provide emergency power to the main rotor 60. The speed of the gas generator 12 then decreases to an ignition window, allowing the turboprop engine to restart. Meanwhile, the second electric machine 40 can advantageously be rotated in the positive direction at a speed slightly lower than the restart speed. This saves time and facilitates the resynchronization of the second freewheel 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 freewheel 41, allowing the gas turbine 10 to restart.

[0093] This architecture is particularly advantageous because it allows, with only two electric machines, the supply of power to the main rotor 60 by the first electric machine 30 and the second electric machine 40, while simultaneously enabling the restart of the gas turbine 10 by the second electric machine 40 during certain operating phases and providing internal hybridization for high and hot flights, for example. It should also be noted that the various stages described above can be carried out by a control unit (not shown), which can detect engine shutdown, the rotational speed of the gas generator and free turbine shafts, and control the electric machines.

[0094] Figure 7 shows an alternative architecture according to the invention, in which the housing 20 comprises a single reversible electric machine 30, which drives the generator shaft 14 via a first freewheel 31 when it rotates in the positive direction, and drives the turbine shaft 13 via a second freewheel 32 when it rotates in the negative direction. This configuration allows for most of the functions described above, except for internal hybridization. In this configuration, at least one of the two freewheels 31, 32 can be locked to enable the electrical generation function.

[0095] Figure 8 shows an example of an architecture similar to that of Figure 7, in which a rotor brake 70 is positioned between the electric machine 30 and the second freewheel 32. The rotor brake 70 is movable between a braking position, preventing the rotation of the propeller 62 and the freewheel turbine 11, and a The free position allows the rotation of the propeller 62 and the free turbine 11. The rotor brake 70 thus allows the free turbine 11, and therefore the main rotor 60, to be locked, particularly in the event of a start-up in strong winds. The presence of the through turbine shaft 13 allows this rotor brake 70 to be positioned in a thermally cold zone, on the side of the first end of the turbine shaft 13, at the rear of the turboprop 100.

[0096] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, the use of lockable or non-lockable freewheels can be replaced by any active coupling means such as dog clutches or clutches. Furthermore, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered illustrative rather than restrictive.

Claims

Demands

1. Turbomachine (100) for a hybrid aircraft, 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 into rotation by a gas flow generated by the gas generator (12), a main rotor (60) comprising a propeller (62), and at least one reversible electric machine (30), the turbine shaft (13) being 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. Turbomachine (100) according to claim 1, wherein the gas generator (12) comprises a compressor (15) and an air inlet (19) configured to supply the compressor (15) with fresh air, the first end of the turbine shaft (13) engaged with the electric machine (30) being disposed adjacent to the air inlet (19).

3. Turbopropeller (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) disposed between the free turbine (11) and the main rotor (60).

4. Turbomachine (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 the main rotor (60) downstream of the combustion chamber (17).

5. Turbomachine (100) according to any one of the claims 1 to 4, in which the electrical machine (30) is in direct contact with the first end of the turbine shaft (13), so as to rotate at the same speed as the turbine shaft (13).

6. Turbomachine (100) according to any one of claims 1 to 4, wherein the electric machine (30) is engaged with the first end of the turbine shaft (13) via a speed matching reducer (33, 34).

7. Turbomachine (100) according to any one of claims 1 to 6, wherein the electric machine (30) is able to be coupled to the generator shaft (14) so ​​as to rotate the gas generator (12) during a start-up phase of the turboprop (100), and is able to be coupled to the turbine shaft (13) after the start-up phase in order to generate electrical power.

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

9. Turbomachine (100) according to any one of claims 1 to 6, wherein the electric machine (30) is a first reversible electric machine, the turboprop (100) further comprising a second reversible electric machine (40) meshed with the generator shaft (14), and capable of exchanging electrical power with the first reversible electric machine (30).

10. Turbomachine (100) according to claim 9, wherein the first electric machine (30) is configured to operate in generator mode, in which it is capable of being driven into rotation by the turbine shaft (13) so as to generate electrical power, or in motor mode in which it is capable of supplying power to the turbine shaft (13).

11. Turbomachine (100) according to claim 9 or 10, wherein the second electric machine (40) is able to be coupled to the generator shaft (14) via a first switchable coupling means (41), and to be coupled to the turbine shaft (13) via a second switchable coupling means (42).

12. Turbomachine (100) according to claim 11, wherein at least one of the first and second switchable coupling means (41, 42) is a freewheel, the first switchable coupling means (41) being configured to be activated when the second electric machine (40) rotates in a first direction of rotation, and the second switchable coupling means (42) being configured to be activated when the second electric machine (40) rotates in a second direction of rotation opposite to the first direction of rotation.

13. Turbomachine (100) according to any one of claims 1 to 12, comprising a rotor brake (70) movable between a braking position, preventing rotation of the main rotor (60), and a free position allowing rotation of the main rotor (60), the rotor brake being disposed upstream of the gas generator (12).

14. Hybrid aircraft comprising a turbomachine (100) according to any one of the preceding claims.

Images