Improved propulsion assembly for multi-engine hybrid aircraft

Abstract

A propulsion assembly (100) comprising: first and second engines (1, 2) each having a gas generator (12, 22) and a free turbine (11, 21); a main rotor (62) coupled to the free turbine (11, 21); the engines (1, 2) each comprise: a first electric machine (30, 40) coupled only to the gas generator (12, 22); and a second electric machine (32, 42) coupled to the gas generator (12, 22) by means of first coupling means (34, 44) when rotating in a first direction and coupled to the free turbine (11, 21) by means of second coupling means (36, 46) when rotating in a second direction, the first electric machine (30, 40) selectively operating in a motor mode or a generator mode, the second electric machine (32, 42) being coupled to the gas generator (12, 22) by means of first coupling means (34, 44) when rotating in a first direction and to the free turbine (11, 21) by means of second coupling means (36, 46) when rotating in a second direction. The second electric machine (32, 42) operates in a motor mode when rotated in a first direction and selectively operates in a motor mode or a generator mode when rotated in a second direction.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of hybrid aircraft, comprising at least two engines, for example turboshaft engines or turboprop engines, for an aircraft, for example a twin-engine helicopter or a twin-engine aircraft. In particular, the present invention relates to a propulsion assembly for a multi-engine hybrid aircraft, in particular a twin-engine aircraft, and to a hybrid aircraft comprising such a propulsion assembly. BACKGROUND

[0002] As is known, turbomachines, for example turboshaft engines, in particular for helicopters, comprise a gas turbine having a gas generator and a free turbine, rotating driven by the flow of gas produced by the gas generator. As is known, the free turbine is completely independent of the gas generator, which comprises one or two (high and low pressure) compressors and one or two (high and low pressure) turbines. In particular, the shaft of the free turbine and the shaft of the gas generator, which carries one or more compressors and one or more turbines, are not coupled. Therefore, the free turbine differs from the (high and low pressure) turbines carried by the shaft of the gas generator, which are coupled with the compressors. Therefore, the particularity of the free turbine turboprop engine lies in the separation of the "engine" (gas generator) and "power turbine" (or free turbine) elements.

[0003] Conventionally, the gas generator comprises at least one compressor and one turbine, coupled in rotation. The working principle is as follows: the fresh air entering the gas turbine is compressed due to the rotation of the compressor and is then sent to the combustion chamber, where it is mixed with the fuel. The combustion gases, produced as a result of the combustion, are then expelled at high speed. A first expansion then occurs in the gas generator turbine, during which the turbine extracts the energy necessary to drive the compressor. The gas generator turbine does not absorb all the kinetic energy of the combustion gases, the excess corresponding to the flow of gas produced by the gas generator. Therefore, the latter provides the kinetic energy to the free turbine, so that, in the latter, a second expansion occurs, which transforms the kinetic energy into mechanical energy, to drive the receiving components, for example the rotors of a helicopter.

[0004] Some aircraft comprise two or more turbomachines, each comprising a gas turbine as described above. This is particularly true in the case of twin-engine or multi-engine helicopters. Such aircraft allow operation in SEO (Single Engine Operation) mode. The SEO mode is a mode of operation of twin-engine architecture in which one gas turbine is intentionally placed in standby, the combustion chamber being unlit or lit, while the other ensures the entire power supply. This mode can optimize the specific fuel consumption / fuel consumption rate, which decreases as the power provided by the turbine decreases. Indeed, since the specific fuel consumption / fuel consumption rate of a turbine decreases as the power provided decreases, it is in fact preferable to use one turbine to provide 100% of the power rather than each turbine providing 50%.

[0005] One of the key points of the SEO mode is to be able to reactivate the standby turbine in the event of a power loss of the operating turbine. To ensure as fast a reactivation as possible, the turbine can be kept in standby (or "super-idle") mode, i.e. using only the electric machine to continue to operate its gas generator, without delivering fuel. The generator is then kept within its "lighting window" (typically 10-30% of the gas generator rated speed) in order to allow the combustion chamber to be immediately lit, or to operate in "super-idle" mode by combustion below the threshold speed and with the help of the mechanical power delivered by the electric machine, in order to benefit from a combustion chamber that is already lit but whose internal temperature is controlled.

[0006] Twin-engine applications involve many functions, such as starting or reactivating a gas generator in flight, generating electricity on board, or providing mechanical power to the main rotor. Existing solutions that allow some of these functions to be performed are not fully optimized. In particular, they do not allow the number of executable functions to be maximized while limiting the impact on engine electric power consumption, nor do they allow the number of components included in these architectures to be maximized, thereby limiting the mass. There is therefore a need for a twin-engine or multi-engine aircraft propulsion system whose architecture can at least partially solve the aforementioned drawbacks. SUMMARY

[0007] The present disclosure relates to a propulsion assembly for a hybrid aircraft, in particular a multi-engine helicopter, comprising:

[0008] - at least a first engine and a second engine, each having a gas generator and a free turbine driven in rotation by the flow of gas produced by the gas generator,

[0009] - a main rotor coupled to the free turbines of the first and second engines,

[0010] - the first and second engines each comprise a first electric machine able to be coupled only to the gas generator and a second electric machine able to be coupled to the gas generator through first coupling means when rotating in a first rotation direction and to the shaft of the free turbine through second coupling means when rotating in a second rotation direction opposite to the first rotation direction, said first electric machine being able to be selectively operated in electric motor mode or in electric generator mode and said second electric machine being able to be operated in electric motor mode when rotating in the first rotation direction and being able to be selectively operated in electric motor mode or in electric generator mode when rotating in the second rotation direction.

[0011] It will be appreciated that, according to the present disclosure, each of the first and second engines is equipped with a first electric machine and a second electric machine, both preferably symmetrical.

[0012] It will also be appreciated that the first and second electric machines are reversible so as to be able to be selectively operated in electric motor mode or in electric generator mode. Thus, the first electric machine can be operated in electric motor mode so as to drive the gas generator by providing engine torque or in electric generator mode driven by said gas generator, the electric current thus generated being able to be transmitted to the second electric machine or to a battery to charge it.

[0013] Similarly, the second electric machine can be operated in electric motor mode so as to drive the gas generator when rotating in the first rotation direction or the main rotor when rotating in the second rotation direction. The second electric machine can also be operated in electric generator mode when rotating in the second rotation direction driven by the free turbine, the electric current thus generated being able to be transmitted to the first electric machine of the first and / or second engine or to a battery to charge it.

[0014] Thus, for each of the first and second engines, the first electric machine is able to be operated in two operating quadrants, i.e. in electric motor mode or in electric generator mode while rotating in a single rotation direction, whereas the second electric machine is able to be operated in three operating quadrants, i.e. in electric motor mode when rotating in the first rotation direction and in electric motor mode or in electric generator mode when rotating in the second rotation direction.

[0015] Within the framework of a multiple engine application, the use of such electric machines provides a wide operating range and has the advantage of becoming simple by limiting the number of components and connections, while ensuring a good level of redundancy by performing bidirectional internal hybridization, each electric machine being able to generate and transmit electric power to the other electric machine and both the first and second electric machines being able to operate as electric generators by being able to perform a large number of functions, in particular during SEO mode operation or during rapid reactivation, thereby improving the reliability of the device.

[0016] In some embodiments, the first and second coupling devices are deactivatable coupling devices.

[0017] By "deactivatable coupling device" it is meant a coupling device that can be in an activated position, in which the components connected to said coupling device are coupled, or in a disengaged position, in which said components are decoupled, it being understood that by "components" it is meant the electric machine, the main rotor and the gas generator.

[0018] In some embodiments, the first and second deactivatable coupling devices comprise freewheels.

[0019] The advantage of a freewheel is that it does not require electronic or mechanical control by an external operator. Such a freewheel generally comprises a hub and an outer peripheral ring gear rotatably mounted on the hub. The hub can drive the outer peripheral ring gear in rotation, but not vice versa. Furthermore, the hub can drive the ring gear only when it rotates in a predetermined direction, which will be called the "engaged direction". Otherwise, the hub and the outer peripheral ring gear are free to rotate relative to each other. In this case, when the hub of the freewheel drives the outer peripheral ring gear in rotation, the deactivatable coupling device is activated, and conversely, when the hub of the freewheel does not drive the outer peripheral ring gear in rotation, the deactivatable coupling device is deactivated.

[0020] In some embodiments, the main rotor is coupled to the free turbine of the first and second engines through a first and a second main coupling device, respectively. Furthermore, the free turbine of each of the first and second engines can be directly engaged with the main rotor, or through a mechanical reduction gear.

[0021] In some embodiments, the first and second coupling devices of the first engine are the only coupling devices upstream of the first main coupling device, and the first and second coupling devices of the second engine are the only coupling devices upstream of the second main coupling device.

[0022] The term "upstream" refers to the direction of transmission of the power provided by the first electric machine towards the main rotor. In other words, each of the first and second engines comprises only two coupling devices, for example two freewheels, in addition to the first and second main coupling devices allowing the coupling of the first and second engines with the main rotor. Minimizing the number of coupling devices comprised by each engine allows to simplify the architecture of the assembly, limit its mass and cost, and minimize potential malfunctions that can occur on these coupling devices, such as accidental jamming.

[0023] In some embodiments, the second coupling devices of the first and second engines comprise a locking device movable between a free position, in which the free turbine cannot drive the second electric machine in rotation, and a locked position, in which the free turbine can drive the second electric machine in rotation.

[0024] The locking device is a device for forcing the coupling between the second electric machine and the free turbine shaft. For example, when the coupling device comprises a free wheel and a locking device, the free wheel is called "lockable free wheel" so that in the locked position, the hub of the free wheel is able to drive the rotation of the outer peripheral ring gear of the lockable free wheel. In other words, the free turbine is able to drive the rotation of the second electric machine which can then operate in generator mode.

[0025] In some embodiments, when one of the first or second engines alone drives the main rotor, the gas generator of the other of the first or second engines is kept in standby mode by the first or second electric machine.

[0026] When the aircraft is running in SEO mode, for example the second engine ensures the entire power supply while the first engine is intentionally stopped or preferably placed in standby mode to optimize the specific fuel consumption / fuel consumption rate. The standby mode allows the gas generator of the first engine to be kept in the range of 5% to 40%, preferably 5% to 30% of its rated speed in order to allow a quick relighting if necessary, in particular when the second engine loses power.

[0027] In some embodiments, when the gas generator of one of the first or second engines is kept in standby mode by the first electric machine, the second electric machine of the other of the first or second engines is configured to operate in generator mode by rotating in the second rotation direction and to transmit the generated electric current to the first electric machine which maintains said first or second engine in standby mode.

[0028] According to this configuration, the shaft of the free turbine advantageously drives the rotation of the second electric machine which operates as a generator, so that the kinetic energy intended to be converted into electrical energy is advantageously taken from the shaft of the free turbine, which itself drives the main rotor, and not from the gas generator. This allows the first electric machine to be powered to assist it, thereby allowing redundancy while limiting the impact on the engine efficiency. Thus, the turbine shaft engine according to the invention advantageously allows to provide electrical power without excessively impacting its efficiency.

[0029] In some embodiments, the second electric machine operating in generator mode is also configured to transmit the generated electric current from the first or second engine alone driving the main rotor to the first electric machine.

[0030] Thus, the electric current generated by the second electric machine can also be (as an alternative or in addition) transmitted to the first electric machine of the engine alone driving the main rotor to assist this electric machine.

[0031] In some embodiments, the first electric machine is coupled to the gas generator only by the separable section.

[0032] In some embodiments, the assembly comprises a monitoring unit configured to control the first electric machine and the second electric machine to drive the gas generator and / or the main rotor by selecting a motor mode, or to transmit the electric current generated by one of the first or second electric machines to the other one of the first or second electric machines by selecting a generator mode.

[0033] In some embodiments, the monitoring unit is configured to, after detecting a power loss in one of the first or second engines driving the main rotor alone, control the first electric machine and the second electric machine of the other one of the first or second engines in standby mode to operate them in motor mode, the second electric machine rotating in the first rotation direction in order to drive the gas generator of said first or second engine in standby mode to rotate.

[0034] The monitoring unit thus allows to ensure redundancy by adjusting the control of the different electric machines according to the flight conditions. For example, when a rapid reactivation is required due to a power loss in one of the two engines, the monitoring unit controls the first electric machine and the second electric machine of the other one of the two engines to operate them both in motor mode in order to accelerate the reactivation of the gas generator in standby mode.

[0035] The present disclosure also relates to a hybrid aircraft comprising a propulsion assembly according to any of the preceding embodiments, said hybrid aircraft being a multi-engine helicopter, in particular a two-engine helicopter.

[0036] By "hybrid aircraft", it is meant an aircraft comprising a thermal engine allowing to drive the main rotor in rotation, and at least one electric machine allowing to power the thermal engine. BRIEF DESCRIPTION OF DRAWINGS

[0037] The application and its advantages will be better understood on reading the detailed description of different embodiments of the application given below, which are given as non-restrictive examples. This description makes reference to the pages of the appended drawings, in which:

[0038] Figure 1 represents a cross-sectional view of a two-engine aircraft propulsion assembly according to the application.

[0039] Figure 2 represents a functional block diagram of the propulsion assembly of Figure 1

[0040] Figure 3 represents a functional block diagram of the propulsion assembly of Figure 2 according to a first operating mode.

[0041] Figure 4 represents a functional block diagram of the propulsion assembly of Figure 2 according to a second operating mode. ​Detailed Implementation

[0042] refer to Figures 1 to 4 The architecture of a propulsion component 100 according to an embodiment of the present invention will be described below.

[0043] It is important to note that, for clarity, these figures schematically represent the architecture of the equipment in a functional and simplified manner, without showing all the details that constitute the turbine and various power transmission elements. In particular, the gears that allow the motor to drive shafts 13 and 14 (and vice versa, where appropriate) and the possible speed ratios are not shown.

[0044] Figure 1 The diagram schematically illustrates a propulsion assembly 100 for a twin-engine aircraft, comprising a first engine (in this example, a first turbine 1) and a second engine (in this example, a second turbine 2), which drive a transmission component 60 of a helicopter equipped with a propeller or main rotor 62 to rotate. The turbines can be turboshaft engines or turboprop engines. Although the propulsion assembly described in the remainder of the description includes two turbines, this example is not limiting, and the invention is also applicable to propulsion assemblies for multi-engine aircraft comprising more than two engines.

[0045] The first turbine 1 and the second turbine 2 are preferably identical and have the same characteristics. Similarly, the following description refers to both the first turbine 1 and the second turbine 2.

[0046] The first turbine 1 and the second turbine 2 each include gas turbines 10 and 20, which have gas generators 12 and 22 and free turbines 11 and 21, which are driven to rotate by the gas flow generated by the gas generators 12 and 22. The free turbines 11 and 21 are mounted on shafts 13 and 23, which transmit rotational motion to a receiving component, such as the main rotor 62 of a helicopter, via a transmission component 60. According to this example, Figure 1 The gas turbines 10 and 20 shown are of the front-end power extraction and concentric shaft return type. Without departing from the framework of this invention, one can certainly consider a front-end power extraction type free turbine gas turbine with internal or external shaft return, or a rear-end power extraction type free turbine turbine. Similarly, the free turbine can be directly coupled to the main rotor 62, or integrated with a reduction gear, without affecting the principles of this invention.

[0047] Gas generators 12 and 22 include rotating shafts 14 and 24 on which compressors 15 and 25 and turbines 16 and 26 are mounted, as well as combustion chambers 17 and 27, which are axially positioned between the compressors 15 and 25 and the turbines 16 and 26 when viewed along the axial direction of the rotating shafts 14 and 24. Gas turbines 10 and 20 have housings 18 and 28 with air inlets 19 and 29 through which fresh air enters the gas generators 12 and 22. After entering the chambers of the gas generators 12 and 22, the fresh air is compressed by the compressors 15 and 25, which force the fresh air to the inlets of the combustion chambers 17 and 27, where it mixes with fuel. Combustion occurring in the combustion chambers 17 and 27 causes the combustion gases to be discharged at high speed towards the turbines 16 and 26, which has the effect of driving the shafts 14 and 24 of the gas generators 12 and 22 to rotate, and thus driving the compressors 16 and 26 to rotate. The rotational speed of the shafts 14 and 24 of the gas generators 12 and 22 is determined by the fuel flow rate entering the combustion chambers 17 and 27.

[0048] Since the propulsion assembly 100 is of the free turbine type, it should be understood that the generator shafts 14 and 24 are independent of the turbine shafts 13 and 23. In other words, unlike the turbines 16 and 26 connected to the compressors 15 and 25, the free turbines 11 and 21 and the turbine shafts 13 and 23 are completely independent of the generator shafts 14 and 24 and the compressors 15 and 25.

[0049] Although turbines 16 and 26 extract kinetic energy, the exhaust gas stream from the gas generator still possesses significant kinetic energy. Figure 1 It is understandable that the gas flow F is directed to the free turbines 11 and 21, causing expansion in the free turbines 11 and 21, which in turn causes the turbine impellers and shafts 13 and 23 to rotate.

[0050] The main rotor 62 is coupled to the shaft 13 of the free turbine 11 of the first gas turbine 10 via a transmission component 60 and by means of a first main coupling device 51. The main rotor 62 is also coupled to the shaft 23 of the free turbine 21 of the second gas turbine 20 via a transmission component 60 and by means of a second main coupling device 52.

[0051] Preferably, the first and second main coupling devices 51 and 52 include freewheels, which are mounted in a manner that allows the rotation of shafts 13 and 23 to drive the main rotor 62, but conversely, the rotation of the main rotor 62 cannot drive the shafts 13 and 23 of the free turbines 11 and 21 to rotate. In other words, the freewheels of the first and second main coupling devices 51 and 52 can only transmit rotational torque in the direction from the free turbines 11 and 21 toward the main rotor 62, and vice versa. On helicopters, such freewheels are commonly referred to as "engine freewheels" or "power freewheels." It should be noted that the use of freewheels in the main coupling devices 51 and 52 is not restrictive; freewheels can be replaced by any claw clutch or friction clutch system.

[0052] Turbines 1 and 2 also each include a first motor 30 and 40, which comprises an electric motor capable of reversibly operating in electric motor mode or generator mode. The first motors 30 and 40 are mechanically coupled only to the shafts 14 and 24 of the gas generators 12 and 22, preferably via separable sections (or breakable shaft sections) 91 and 92, thereby allowing irreversible release of the motor in the event of jamming. In other words, the separable sections 91 and 92 are configured to allow disconnection of the first motors 30 and 40 from the generator shafts 14 and 24 in the event of jamming of the gas generators 12 and 22, such as during unexpected shutdown or malfunction.

[0053] Turbines 1 and 2 each include a second motor 32 and 42, which also includes an electric motor capable of reversibly operating in electric motor mode or generator mode. The second motors 32 and 42 are mechanically coupled to the shafts 14 and 24 of the gas generators 12 and 22 via first deactivation coupling devices 34 and 44, which include freewheels (hereinafter referred to as freewheels 34 and 44).

[0054] The mounting arrangement of the freewheels 34 and 44 allows the rotation of the second motors 32 and 42, which operate in electric motor mode, to drive the rotation of the gas generators 12 and 22. Conversely, the rotation of the gas generators 12 and 22 cannot drive the second motors 32 and 42. In other words, the freewheels 34 and 44 can only transmit rotational torque in the direction from the second motors 32 and 42 toward the gas generators 12 and 22.

[0055] The second motors 32 and 42 are also mechanically coupled to the shafts 13 and 23 of the free turbines 11 and 21 via second deactivation coupling devices 36 and 46, which include free wheels (hereinafter referred to as free wheels 36 and 46).

[0056] The mounting arrangement of the freewheels 36 and 46 allows the rotation of the second motors 32 and 42, which subsequently operate in electric motor mode, to drive the free turbines 11 and 21. Conversely, the rotation of the free turbines 11 and 21 cannot drive the second motors 32 and 42, unless the freewheels 36 and 46 are locked according to the configuration described below. In other words, the unlocked freewheels 36 and 46 can only transmit rotational torque in the direction from the second motors 32 and 42 toward the free turbines 11 and 21.

[0057] According to the device disclosed herein, the second motors 32, 42 are rotatable in a first rotational direction—wherein they are mechanically coupled to the shafts 14, 24 of the gas generator 12—and are rotatable in a second rotational direction opposite to the first rotational direction—wherein the second motors are mechanically coupled to the shafts 13, 23 of the free turbines 11, 21, and thus can drive the main rotor 62 through the shafts 13, 23 of the free turbines 11, 21.

[0058] As a convention, in the remainder of the description, the positive direction will be understood as the direction in which the free wheels 34 and 44 are activated, within the rotational directions of the second motors 32 and 42, and the negative direction as, for example, the direction in which the free wheels 36 and 46 are activated, within the rotational directions of the second motors 32 and 42. Specifically, Figure 2 The elements indicated by "-1" in the following diagrams represent gears that allow the rotation direction to be reversed, such as pinions.

[0059] Therefore, it can be understood that when the second motors 32 and 42 rotate in the positive direction, the free wheels 34 and 44 can be activated, while the free wheels 36 and 46 are deactivated; when the second motors 32 and 42 rotate in the negative direction, the free wheels 34 and 44 are deactivated, while the free wheels 36 and 46 can be activated.

[0060] According to this embodiment, the free wheels 36 and 46 are lockable. Specifically, the second coupling device also includes locking devices 38 and 48. Locking devices 38 and 48 are movable between a free position and a locked position. In the free position, due to the orientation of the free wheels 36 and 46, the free turbines 11 and 21 cannot drive the second motors 32 and 42 to rotate. Figure 2 (As shown in the diagram), in the locked position, the freewheels 36 and 46 can be locked, thereby forcing the coupling between the freewheels 11 and 21 and the second motors 32 and 42. Figure 3(The configuration shown for locking device 48 is illustrated in the diagram). In other words, when locking devices 38 and 48 are in the locked position, the second coupling device acts as a shaft, allowing the free turbines 11 and 21 to drive the second motors 32 and 42 to rotate despite the presence of free wheels 36 and 46. The second motors 32 and 42 can therefore operate in generator mode by drawing power from the shafts 13 and 23 of the free turbines 11 and 21. It should be noted that changes in the position of locking device 46 can be performed by electric, pneumatic, or hydraulic components and controlled by the user or monitoring unit.

[0061] In this respect, the components according to the invention also include: a current storage device, such as a battery 70 or a "battery pack"; and a monitoring unit 80.

[0062] Battery 70 is capable of storing the current generated when the motors operate in generator mode and providing the necessary current when these motors operate in motor mode. It should be noted that although the electrical connection between battery 70 and the motors is not shown in all figures for clarity, this connection is indeed always present.

[0063] The monitoring unit 80 is typically a calculator or electronic control unit, often abbreviated as ECU. It controls the first motors 30 and 40 and the second motors 32 and 42 of each of the engines 1 and 2, allowing them to operate selectively in engine or generator mode; controls the battery 70 to transfer current from the battery to the motors when necessary and to measure its state of charge; and also controls the locking devices 38 and 48 to switch them from the free position to the locked position and vice versa. The monitoring unit 80 and its connections to these different components are only... Figure 1 As shown in the figure, it also exists in other figures, but is omitted for the sake of simplicity.

[0064] Therefore, the first motors 30 and 40 can operate in two operating quadrants (operating in motor mode or generator mode under the control of the monitoring unit 80), while the second motors 32 and 42 can operate in three operating quadrants (acting in motor mode to the gas generators 12 and 22 when rotating in the positive direction, or acting in motor mode to the main rotor 62 when rotating in the negative direction, and operating in generator mode when rotating in the negative direction, with the locking device 38 / 48 in the locked position).

[0065] This simple architecture of the propulsion assembly 100, which uses only two freewheels 34, 44 and 36, 46 located upstream of the main coupling devices 51, 52 for each engine 1, 2, allows for the efficient execution of the different operating modes described below in the specification, thereby allowing for the optimization of the operation of the propulsion assembly 100.

[0066] Figure 3This indicates operation in SEO (single-engine operation) mode, made possible by the presence of two turbines 1 and 2. In this mode, only the second turbine 2 (in this example) is running, ensuring full power is supplied to the main rotor 62, while the first turbine 1 is intentionally placed in standby mode. When SEO mode is activated, the gas generator 12 is placed in standby mode (or auxiliary over-idle mode), meaning it no longer supplies power to the main rotor 62. On the other hand, to reactivate as quickly as possible, the gas generator 12 is driven by the first motor 30 in this example within the ignition window (within 5% to 30% of its rated speed, e.g., 10%). It should be noted in this respect that... Figure 3 (and the description below) Figure 4 In the diagram, the bold lines and arrows indicate the direction of transmission of mechanical power provided or obtained by the motor.

[0067] Conversely, the first motor 40 of the second turbine 2 drives only the main rotor 62, providing power to the gas generator 22 to operate at its rated speed in order to drive the free turbine 21 and its shaft 23, and thus drive the main rotor 62 through the transmission component 60.

[0068] Simultaneously, the second motor 42 of the second turbine 2 is used to obtain mechanical power from the shaft 23 of the free turbine 21. For this purpose, the second motor 42 is manipulated to rotate in the negative direction and operate in generator mode (in...). Figure 3 (Represented by a small lightning bolt in the middle), locking device 48 is operated in the locked position to lock freewheel 46.

[0069] The electricity generated by the second motor 42 passes through Figure 3 The electrical connection, indicated by the dashed line, transmits power to the first motor 40 of the second turbine 2. This first motor operates in electric motor mode, thereby injecting mechanical power into the high-pressure body of the gas generator 22. This battery-free internal hybridization allows for improved service life of the second turbine 2.

[0070] The electricity generated by the second motor 42 is also transmitted electrically to the first motor 30 of the first turbine 1, which operates in standby mode. The first motor 30 operates in electric motor mode and also injects mechanical power into the high-pressure body of the gas generator 12, but the power is lower than that of the first motor 40 of the second turbine 2 (approximately 10% of the rated speed of the first turbine 1).

[0071] Figure 4 This indicates the operation under rapid reactivation conditions. In fact, starting with SEO mode operation, in emergency situations, when the second turbine 2, which is running at full power to supply power solely to the main rotor 62, loses power, or when the power demand of the main rotor 62 rapidly becomes greater than the power that a single turbine shaft engine can provide, it may be necessary to rapidly reactivate the first turbine 1.

[0072] In this scenario, the first motor 30 and the second motor 32 of the first turbine 1 are controlled to operate in electric motor mode and provide mechanical power to the gas generator 12. The second motor 32 rotates in the positive direction. Since internal hybridization of electricity is not possible in this situation, the first motor 30 and the second motor 32 are powered by the battery 70.

[0073] More specifically, this method of reactivating the optimized propulsion assembly 100 may initially include the detection by the monitoring unit 80 of a power loss in the second turbine 2 or a significant drop in the rotational speed of the main rotor 62. Then, the high-pressure main body of the gas generator 12 of the first turbine 1 is kept within the ignition rate window by a first motor 30 until ignition of the combustion chamber 17 is detected, wherein the first motor is powered by the battery 70.

[0074] When ignition is detected in combustion chamber 17, the first motor 30 and the second motor 32 of the first turbine 1 are then controlled to operate in electric motor mode, powered by battery 70, to assist gas generator 12, thereby quickly reactivating the first turbine 1. It should be noted that the above steps also apply to the normal reactivation of either turbine 1 or 2, except in emergency situations.

[0075] It should also be noted that the first motors 30 and 40 and the second motors 32 and 42 are preferably high-power motors, particularly those in the tens of kilowatts range, enabling the turbines to be started much faster than a starter with a power of approximately 10 kilowatts. Therefore, each of the first and second motors can ensure rapid reactivation of the turbines 1 and 2 when they are in standby mode. This rapid reactivation function is therefore redundant and remains possible even in the event of a failure of one of the first motors 30 and 40 or the second motors 32 and 42, thus ensuring high availability.

[0076] However, it should be noted that this configuration is not limiting; the first motor can have higher power than the second motor, or vice versa, without departing from the framework of this invention. Furthermore, the first and second motors can operate sequentially or synchronously.

[0077] Although the invention has been described with reference to specific exemplary embodiments, it will be apparent that modifications and variations can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

[0078] It is equally evident that all features described in the reference method can be applied individually or in combination to the device, and conversely, all features described in the reference device can be applied individually or in combination to the method.

Claims

1. A propulsion assembly (100) for use in hybrid-electric aircraft, particularly for multi-engine helicopters, said propulsion assembly comprising: At least a first engine (1) and a second engine (2), each having a gas generator (12, 22) and a free turbine (11, 21) driven to rotate by the gas flow generated by the gas generator. The main rotor (62) is coupled to the free turbines (11, 21) of the first engine and the second engine (1, 2). Each of the first engine (1) and the second engine (2) includes: a first motor (30, 40) that can be coupled only to the gas generator (12, 22); and a second motor (32, 42) that, when rotating in a first direction of rotation, can be coupled to the gas generator (12, 22) via a first coupling device (34, 44), and when rotating in a second direction of rotation opposite to the first direction of rotation, can be coupled to the shaft (23) of the free turbine (11, 21) via a second coupling device (36, 46). The first motor (30, 40) can be selectively operated in electric motor mode or generator mode, and the second motor (32, 42) can be operated in electric motor mode when rotating in the first direction of rotation and can be selectively operated in electric motor mode or generator mode when rotating in the second direction of rotation.

2. The propulsion assembly (100) according to claim 1, wherein the first coupling device (34, 44) and the second coupling device (36, 46) are deactivatable coupling devices.

3. The propulsion assembly (100) according to claim 2, wherein the first deactivatable coupling device (34, 44) and the second deactivatable coupling device (36, 46) comprise freewheels.

4. The propulsion assembly (100) according to any one of claims 1 to 3, wherein the main rotor (62) is coupled to the free turbines (11, 21) of the first engine (1) and the second engine (2) via a first main coupling device and a second main coupling device (51, 52), respectively.

5. The propulsion assembly (100) according to claim 4, wherein the first coupling device and the second coupling device (34, 44) of the first engine (1) are the only coupling devices upstream of the first main coupling device (51), and the first coupling device and the second coupling device (36, 46) of the second engine (2) are the only coupling devices upstream of the second main coupling device (52).

6. The propulsion assembly (100) according to any one of claims 1 to 5, wherein the second coupling device (36, 46) of the first engine and the second engine (1, 2) includes a locking device (38, 48) movable between a free position and a locked position, wherein in the free position the free turbine (11, 21) cannot drive the second motor (32, 42) to rotate, and in the locked position the free turbine (11, 21) can drive the second motor (32, 42) to rotate.

7. The propulsion assembly (100) according to any one of claims 1 to 6, wherein, When one of the first engine or the second engine (1, 2) drives the main rotor (62) alone, the gas generator (12, 22) of the other of the first engine or the second engine (1, 2) remains in standby mode via the first motor (30, 40) or the second motor (32, 42).

8. The propulsion assembly (100) according to claim 7, wherein, When the gas generator (12, 22) of one of the first or second engines (1, 2) is kept in the standby mode by the first motor (30, 40), the second motor (32, 42) of the other of the first or second engines (1, 2) is configured to operate in generator mode by rotating in a second rotation direction and transmit the generated current to the first motor (30, 40) that keeps the first or second engine (1, 2) in the standby mode.

9. The propulsion assembly (100) according to claim 8, wherein, The second motor (32, 42), which operates in generator mode, is configured to also transmit the generated current from the first engine or the second engine (1, 2) that separately drives the main rotor (62) to the first motor (30, 40).

10. The propulsion assembly (100) according to any one of claims 1 to 9, wherein the first motor (32, 42) is coupled to the gas generator (12, 22) only through a separable segment (91, 92).

11. The propulsion assembly (100) according to any one of claims 1 to 10 includes a monitoring unit (80) configured to control the first motor (30, 40) or the second motor (32, 42) to drive the gas generator (12, 22) and / or the main rotor (62) by selecting a motor mode, or to select a generator mode to transmit current generated by one of the first motor (30, 40) or the second motor (32, 42) to the other of the first motor (30, 40) or the second motor (32, 42).

12. The propulsion assembly (100) according to claim 11, wherein the monitoring unit (80) is configured to, upon detecting a power loss in one of the first or second engines (1, 2) that individually drives the main rotor (62), control the first and second motors (30, 40, 32, 42) of the other of the first or second engines (1, 2) in standby mode to operate in electric motor mode, causing the second motor (32, 42) to rotate in a first rotation direction to drive the gas generator (12, 22) of the first or second engine (1, 2) in standby mode to rotate.

13. A hybrid-powered aircraft comprising a propulsion assembly (100) according to any one of the preceding claims, wherein the hybrid-powered aircraft is a multi-engine helicopter, particularly a twin-engine helicopter.

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