Propulsion system for fixed-wing aircraft and associated aircraft

Abstract

The invention relates to a propulsion system (20) for a fixed-wing aircraft (3), comprising an alternating current generator (24), at least one wingtip propulsion unit (22) comprising an alternating current motor, and at least one lift-enhancing propulsion unit (23a-23d) comprising an alternating current motor. The generator is connected to the lift-enhancing propulsion unit via an AC / DC converter (261), an intermediate DC distribution stage (260) provided with a power battery (262), and a DC / AC converter (263a-263d). In contrast, the generator is connected to the wingtip propulsion unit in such a way that it supplies the propulsion unit with alternating current without intermediate conversion of the alternating current into direct current. The invention also relates to an aircraft provided with such a propulsion system.

Description

Technical Field

[0001] The invention relates to a propulsion system for a non-rotorcraft, the system comprising a propulsion unit having an electric motor. It also relates to a non-rotorcraft provided with such a propulsion system, in particular a hybrid propulsion aircraft equipped with both a turbopropeller and a propulsion unit having an electric motor. Background Art

[0002] For non-rotorcraft, electric or hybrid propulsion is a particularly beneficial alternative to propulsion achieved solely by turboprops.

[0003] In fact, the use of electric or hybrid propulsion units during the take-off or landing phases can reduce polluting emissions near airports and nearby urban areas.

[0004] In addition, the use of electric propulsion units, as a supplement or alternative to turbopropellers, facilitates the realization of advanced propulsion architectures, comprising, for example, additional wingtip propulsion units, which make it possible to reduce wingtip drag, or comprising, for example, one or more additional rear propulsion units with BLI (boundary layer inhalation).

[0005] In this field, document US 2018 / 0118356 describes an aircraft whose propulsion is of the “turbine-electric distributed” type, entirely relying on electric propulsion units (without turboprops). These propulsion units are distributed along the wings of the aircraft.

[0006] Some of these propulsion units are placed at the wingtips and are used as "flight control" propulsion units to allow the direction of the aircraft to be controlled. Their respective rotational speeds are carefully controlled on a propulsion unit-by-propulsion unit basis. Other propulsion units are called "thrust" propulsion units and are used to supply most of the thrust required for the flight of the aircraft. They are located between the "flight control" propulsion units and the fuselage of the aircraft.

[0007] The aircraft in question further comprises an alternator driven by a turbine (a turbine not provided with a propeller) for supplying power to the electric motor of the propulsion unit.

[0008] The electric motor of the "thrust" propulsion unit is powered directly from this generator, without an intermediate converter, which limits the losses in the power supply circuit.

[0009] As for the "flight control" propulsion units, they are electrically connected to the generator via an intermediate stage operating with DC current. Each "flight control" propulsion unit is connected to this intermediate stage via a DC / AC converter (which converts direct current into alternating current), in such a way that the propulsion unit concerned is finally powered with alternating current. This structure with intermediate conversion in the form of direct current makes it possible to finely control the speeds of rotation of the "flight control" propulsion units, independently of each other (and of the speed of rotation of the turbine), thanks to which control of the direction of the aircraft can be obtained.

[0010] However, in the above-described propulsion systems, the emission of polluting gases is still significant during the take-off, landing and taxiing phases (since during these phases the turbine must be running in order to power the “thrust” propulsion unit which supplies most of the thrust). Summary of the invention

[0011] In this context, a propulsion system for a non-rotorcraft is proposed, comprising:

[0012] - Alternator,

[0013] - at least one wingtip propulsion unit comprising an AC electric motor having a direction of rotation opposite to the formation of the wingtip vortex,

[0014] - at least one lift-increasing propulsion unit comprising an AC motor,

[0015] - a first AC power circuit electrically connecting the generator to the wingtip propulsion unit, and

[0016] - a second AC power supply circuit electrically connecting the generator to the lift augmentation propulsion unit,

[0017] -Wherein the second power supply circuit comprises:

[0018] - Intermediate DC distribution level,

[0019] - one or more power batteries connected to said intermediate DC distribution stage,

[0020] - an AC / DC converter electrically connecting the generator to said intermediate DC distribution stage, and

[0021] - a DC / AC converter electrically connecting said intermediate stage with a lift-increasing propulsion unit,

[0022] - and wherein the first power circuit is configured to deliver AC current generated by the generator to the wingtip propulsion unit without intermediate conversion of the alternating current to direct current.

[0023] Thanks to the intermediate DC distribution stage, and thanks to the converter of the second circuit, one or more lift-increasing propulsion units, whose role in the take-off phase is crucial, can be powered by batteries during this phase. This makes it possible to reduce polluting gas emissions in and near airport areas in a very beneficial way.

[0024] Furthermore, this particular configuration of the second circuit makes it possible to electrically regulate the speed of rotation of the lift-increasing propulsion unit in a very flexible manner, independently of the speed of rotation of the generator (which, in practice, is driven by a turbine). This therefore makes it possible to flexibly regulate the lift increase, thus authorizing rapid, one-time changes in altitude, which increases the agility of the aircraft.

[0025] Furthermore, connecting one or more wingtip propulsion units directly to a generator in a manner that does not require intermediate conversion to direct current allows for very significant fuel savings over a typical flight of an aircraft.

[0026] This reduction in overall consumption may seem surprising at first glance, since the role of the wingtip propulsion units seems a priori to be secondary in the propulsion of the aircraft (in document US 2018 / 0118356, such propulsion units also play a secondary role). But in fact, the wingtip propulsion units make it possible to significantly reduce the wingtip drag (due to the formation of wingtip vortices), a drag that significantly participates in the total drag experienced by the aircraft. It is therefore desirable to have these wingtip propulsion units in almost continuous operation (and to give them a significant role in the propulsion of the aircraft) and, therefore, given that their operation is practically permanent, to minimize the electrical losses in their power supply circuits and thereby increase the yield of the transmission chain and minimize the total mass of this transmission chain. Here, this minimization of losses is achieved by a somewhat direct connection between the generator and the wingtip propulsion unit or units, without the need for AC / DC conversion.

[0027] In particular, it may be provided that each lift-increasing propulsion unit is positioned between, on the one hand, a wingtip propulsion unit or one of the wingtip propulsion units and, on the other hand, a fuselage of the aircraft.

[0028] The propulsion system just proposed may also include a turbopropeller. The generator mentioned above may then be driven, for example, by the turbine of this turbopropeller.

[0029] This configuration makes it possible to further improve the overall energy consumption of the aircraft (for example, consumption throughout a regional flight of several hundred kilometers).

[0030] In fact, this configuration makes it possible to ensure the propulsion of the aircraft by means of the turbopropellers and the wingtip propulsion units, while keeping one or more lift-increasing propulsion units switched off, during the cruising or climbing phases.

[0031] During these particularly long and fuel-intensive flight phases, the losses that would result from the AC / DC conversion in the second power supply circuit are thus avoided.

[0032] Formulated in a different way, the second power supply circuit, which causes additional power losses due to the turboprop (but which in turn allows low-pollution take-off and landing), is used only during a shortened duration, during the take-off or landing phase (or for rapid changes in altitude).

[0033] In addition to the features mentioned above, the propulsion system according to the present invention may have one or more of the following additional features, alone or in any technically permissible combination:

[0034] - the first power supply circuit and the second power supply circuit are connected to each other via an AC distribution stage common to both power supply circuits, the AC distribution stage itself being connected to a generator, the AC / DC converter of the second power supply circuit being connected between the AC distribution stage and an intermediate DC distribution stage;

[0035] - the AC / DC converter is reversible, said converter allowing both the transfer of electric power from the AC distribution stage to the intermediate DC distribution stage and the transfer of electric power from the intermediate DC distribution stage to the AC distribution stage;

[0036] - the DC / AC converter of the second power supply circuit is reversible, said converter allowing both the transfer of electric power from the intermediate DC distribution stage to the lift augmentation propulsion unit and the transfer of electric power from the lift augmentation propulsion unit to the intermediate DC distribution stage;

[0037] - the propulsion system further comprises an electronic control unit comprising at least one processor and a memory, the control unit being programmed to control the electric motor of the lift-increasing propulsion unit during the flight of the aircraft, in particular including the take-off phase, the cruising phase and the landing phase, so that the propulsion unit:

[0038] - delivering mechanical propulsion power during take-off and / or landing phases,

[0039] - but remain closed during most of the cruise phase,

[0040] - the control unit of the propulsion system is programmed to: control the electric motors of the wingtip propulsion units to deliver mechanical propulsion power during most of the flight of the aircraft;

[0041] - lift-increasing propulsion unit including a fixed pitch propeller;

[0042] -Wingtip propulsion units include variable pitch propellers.

[0043] Another aspect of the present invention relates to a non-rotorcraft, comprising:

[0044] - a fuselage, a left wing extending to the left side of the fuselage, and a right wing extending to the right side of the fuselage,

[0045] - a first propulsion system and a second propulsion system as described above,

[0046] - the wing tip propulsion units of the first propulsion system and the second propulsion system are located at the tip of the left wing and the tip of the right wing, respectively, or vice versa,

[0047] - The lift-increasing propulsion units are located between the fuselage and the wingtip propulsion units of the aircraft.

[0048] The aircraft just proposed may also have one or more of the following additional features, either alone or in any technically permissible combination:

[0049] - the first propulsion system and the second propulsion system each comprise a turbopropeller;

[0050] - a turbopropeller of the first propulsion system driving a generator of the first propulsion system is located on the left side of the fuselage, while a wingtip propulsion unit of the first propulsion system is located at the tip of the right wing of the aircraft;

[0051] - the turbopropeller of the second propulsion system driving the generator of the second propulsion system is located on the right side of the fuselage, while the wingtip propulsion unit of the second propulsion system is located at the tip of the left wing of the aircraft;

[0052] - the first propulsion system comprises at least two lift augmentation propulsion units, one located on the left side of the fuselage and the other located on the right side of the fuselage, both lift augmentation propulsion units being electrically connected to the intermediate DC distribution stage of the first propulsion system;

[0053] - the second propulsion system comprises at least two lift augmentation propulsion units, one located on the left side of the fuselage and the other located on the right side of the fuselage, both lift augmentation propulsion units being electrically connected to the intermediate DC distribution stage of the second propulsion system;

[0054] - Each wingtip propulsion unit and each lift increasing propulsion unit is electrically connected to the generator of the first propulsion system on the one hand and to the generator of the second propulsion system on the other hand so as to be powered indifferently by one or the other of these two generators; this makes it possible to continue to supply power to the various electric propulsion units even in the event of a failure of one of the generators or of one of the turbines driving these generators.

[0055] The invention and its various applications will be better understood upon reading the following description and examining the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The drawings are presented for informational purposes and are not intended to limit the invention in any way.

[0057] [ Figure 1 ] Figure 1 A non-rotorcraft according to a first embodiment is schematically shown as seen from above.

[0058] [ Figure 2 ] Figure 2 A non-rotorcraft according to a second embodiment is schematically shown as seen from above.

[0059] [ Figure 3 ] Figure 3 is a partial schematic diagram of a non-rotor aircraft according to a third embodiment showing a first propulsion system of the aircraft as viewed from above.

[0060] [ Figure 4 ] Figure 4 yes Figure 3 A partial schematic diagram of an aircraft of , showing a second propulsion system of the aircraft as seen from above.

[0061] [ Figure 5 ] Figure 5 A non-rotorcraft according to a fourth embodiment is schematically shown as seen from above.

[0062] [ Figure 6 ] Figure 6 For example, Figures 1 to 5 The individual propulsion units of one of the aircraft are schematically shown at what point during a typical flight of the aircraft each of these propulsion units is a motor, a generator, or is switched off. DETAILED DESCRIPTION

[0063] Figures 1 to 5 Four different embodiments 1; 2; 3; 4 of non-rotorcraft implementing the teachings of the present invention are shown.

[0064] Whichever embodiment is considered, the aircraft 1 ; 2 ; 3 ; 4 comprises a fuselage 11 extending along the aircraft's centreline longitudinal axis, a left wing 12 extending to the left of the fuselage 11 and a right wing 13 extending to the right of the fuselage 11 .

[0065] The left wing 12 and the right wing 13 may be separate from each other. However, they may also form together a single-piece wing element which presents to the air a continuous surface extending from the free end 120 of the left wing to the free end 130 of the right wing (in this case, the expression left wing designates the part of the wing element extending to the left side of the fuselage, and the same applies to the expression right wing).

[0066] In each of the embodiments shown, the aircraft 1; 2; 3; 4 has a first propulsion system 20; 20 'and a second propulsion system 20; 30 ', for example a left propulsion system 20 and a right propulsion system 30, such as Figure 1 As in the case of.

[0067] These propulsion systems, which are described in detail below, are, inter alia, particularly well suited for the case where aircraft 1; 2; 3; 4 is a "commuter" type passenger (or cargo) aircraft (typically comprising less than 50 passenger seats and weighing less than 20 tons) intended to carry out regional type flights of several hundred kilometers.

[0068] In any case, these propulsion systems can also equip aircraft with long take-off as well as aircraft with short take-off.

[0069] As shown, the first propulsion system 20; 20' and the second propulsion system 30; 30' of the aircraft each include:

[0070] - turboprop 21, 31,

[0071] - Wing tip propulsion units 22, 32 with AC motors, which are here multi-phase motors.

[0072] at least one, here N, lift-increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d having an AC motor, here a multiphase motor,

[0073] an alternator 24 , 34 , here multiphase, driven by the turboprop 21 , 31 and making it possible to supply power to the electric propulsion unit mentioned above, and

[0074] - An electric power distribution system connecting the generators 24, 34 to the relevant electric propulsion units.

[0075] Here, the number N of lift increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d is equal to four for each of the first propulsion system 20; 20' and the second propulsion system 30; 30'.

[0076] The turbopropeller 21 of the first propulsion system 20; 20' is located on the left side of the fuselage 11, while the turbopropeller 31 of the second propulsion system 30; 30' is located on the right side of the fuselage 11. Here, these turbopropellers are fastened to the left and right wings 12, 13 of the aircraft.

[0077] The propulsion of the aircraft 1 ; 2 ; 3 ; 4 achieved both by the turboprops 12 , 13 and by the electric propulsion units 22 , 23a , 23b , 23c , 23d , 32 , 33a , 33b , 33c , 33d is therefore a hybrid propulsion.

[0078] Among the various propulsion units of the aircraft, the wingtip propulsion units 22, 32 are those which are situated closest to the wingtips 12, 13 of the aircraft (i.e. closest to the free ends 120, 130 of the wings). For example, they may be positioned so that their motor shafts are situated at a distance from the free ends 120, 130 of the wings in question which is smaller than the diameter of the propeller 220, 320 of the propulsion unit, or even smaller than the radius of the propeller. The propeller 220, 320 of the propulsion unit may protrude from the wing (e.g. the shaft of the propulsion unit is then aligned with the free ends 120, 130 of the wing).

[0079] The wingtip propulsion units 22, 32 make it possible to reduce the wingtip drag due to the formation of wingtip vortices. Provision is made here for these propulsion units to be operated during a large part of the flight during a typical flight of an aircraft. Their respective direction of rotation is chosen so as to be opposite to the wingtip vortices formed on the wingtips 12, 13 on which they are mounted.

[0080] As for the lift increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d, they are distributed along the wings 12, 13 of the aircraft between the wing tip propulsion units 22, 32 and the fuselage 11. Here, the lift increasing propulsion units are distributed more precisely between the wing tip propulsion units 22, 32 and the turboprops 21, 31.

[0081] The lift-increasing propulsion units make it possible to increase the lift of the aircraft by changing the airflow above and below the wings 12, 13 of the aircraft (which further explains that they are positioned entirely on the wing under consideration, rather than at its ends). As shown in the figure, the lift-increasing propulsion units drive propellers located upstream of the leading edge of the wing of the aircraft. Alternatively, these propellers can also be located downstream (or to the right) of the leading edge, for example, below the wing in question. It is provided here that during a typical flight of an aircraft, the lift-increasing propulsion units are operated mainly during the take-off, approach and landing phases and during taxiing. It is provided that these propulsion units are closed during most of the climb and cruise phases (although they can be opened for a short period of time during these phases, for example to allow a rapid increase in altitude).

[0082] As shown, the aircraft 1; 2; 3; 4 comprises four lift increasing propulsion units 23a-23d, 33a-33d on each wing 12, 13. However, alternatively, each wing of the aircraft may be provided with a different number of lift increasing propulsion units (e.g., the number N of lift increasing propulsion units equipped with each wing may be equal to 1, 2 or 3 or higher than 4).

[0083] In the embodiment shown, the various electric propulsion units 22, 23a, 23b, 23c, 23d, 32, 33a, 33b, 33c, 33d are distributed along the wings 12, 13 of the aircraft. However, in other embodiments not shown, the aircraft may also include one or more electric propulsion units located somewhere other than the wings, for example at the rear of the fuselage.

[0084] Now that the overall arrangement of the aircraft 1; 2; 3; 4 and the propulsion units has been introduced, the specific power distribution system implemented in the aircraft can be described to power the electric propulsion units 22, 23a, 23b, 23c, 23d, 32, 33a, 33b, 33c, 33d.

[0085] The differences between the first embodiment, the second embodiment, the third embodiment and the fourth embodiment mainly relate to the power distribution system. Here, with respect to the aircraft 1 of the first embodiment, the aircraft 2; 3; 4 of the second embodiment, the third embodiment or the fourth embodiment implements additional left and right cruise and / or redundant arrangements between the two propulsion systems 20, 30; 20', 30', due to which relatively symmetrical thrust can be maintained even in the event of a failure of the left turbopropeller 21 or the right turbopropeller 31.

[0086] However, many technical features are the same for these different embodiments. Therefore, from one embodiment to another, the same or corresponding elements will be marked with the same reference symbols as much as possible, and do not necessarily need to be described every time.

[0087] The propulsion system of the aircraft, in particular the way in which the electric propulsion units 22, 23a, 23b, 23c, 23d, 32, 33a, 33b, 33c, 33d are powered, will now be described in more detail embodiment by embodiment.

[0088] In the first embodiment ( Figure 1 ), the propulsion units 21, 22, 23a, 23b, 23c, 23d of the first propulsion system 20 are located on the left side of the fuselage 11, while the propulsion units 31, 32, 33a, 33b, 33c, 33d of the second propulsion system 30 are located on the right side of the fuselage 11.

[0089] In addition to its propulsion unit and its alternator 24, the first propulsion system 20 (left propulsion system) comprises:

[0090] a first power supply circuit 25 which electrically connects its generator 24 to the wingtip propulsion unit 22 in order to supply it with electrical power, and

[0091] - a second power supply circuit 26 which electrically connects its generator 24 to its various lift-increasing propulsion units 23a, 23b, 23c, 23d so as to be able to supply them with electricity.

[0092] The first power supply circuit 25 and the second power supply circuit 26 are both AC (alternating current) power supply circuits making it possible to power an AC motor of an electric propulsion unit of the aircraft when they each deliver an electrical supply current of the alternating type.

[0093] However, it is worth noting that the second power supply circuit 26 includes:

[0094] - intermediate DC distribution stage 260,

[0095] - an AC / DC converter, 261 , which electrically connects the generator 24 to the intermediate DC distribution stage 260 , and

[0096] - for each lift increasing propulsion unit 23a , 23b , 23c , 23d , a DC / AC converter 263a , 263b , 263c , 263d of inverter type, which converter electrically connects the lift increasing propulsion unit in question with the intermediate DC distribution stage 260 .

[0097] Thus, an intermediate conversion to direct current (DC) is achieved between the generator 24 supplying alternating current (AC) and the lift-increasing propulsion units 23a, 23b, 23c, 23d equipped with electric motors 231a, 231b, 231c, 231d (also AC).

[0098] In contrast, the first power circuit 25 is configured to deliver the AC current generated by the generator 24 to the wingtip propulsion unit 22 without intermediate conversion of the alternating current into direct current.

[0099] Therefore, the first power supply circuit 25 has no AC / DC or DC / AC converter.

[0100] However, like here, the first power supply circuit 25 may include one or more controlled contactors or switches, as well as one or more protection devices (for example to protect against overvoltages), not shown. Note, however, that these protection devices are not current or voltage converters. In fact, they make it possible to establish or suspend electrical connections between different elements of the circuit, but they do not make it possible to convert the amplitude (or value), waveform, direct or alternating nature or frequency of the current or voltage.

[0101] Here, the motor 221 of the wingtip propulsion unit 22 is an AC motor of synchronous type. Therefore, the first power supply circuit 25 is provided with a starting and synchronizing device 251 connected between the motor and the generator 24 to start the motor. In other embodiments, the motor of the wingtip propulsion unit will be a motor of asynchronous type and this starting and synchronizing device can be omitted. In this latter case, the first power supply circuit will not have any type of current or voltage converter.

[0102] The first power circuit 25 and the second power circuit 26 are connected to each other via an AC distribution stage 27 common to the two power circuits 25 and 26. The distribution stage is implemented by contactors, protection devices, busbars (i.e., high-current electrical conductors implemented in the form of a monolithic rod or conductive plate) and other electrical conductors or connectors.

[0103] The generator 24 is connected to the AC distribution stage 27 , for example directly via electrical conductors (without any intermediate devices).

[0104] The activation and synchronization means 251 of the wingtip propulsion units 22 are also connected to this AC distribution stage 27 (for example directly via electrical conductors, without any intermediate means).

[0105] Furthermore, an AC / DC converter 261 of a second circuit is connected between the AC distribution stage 27 and the intermediate DC distribution stage 260 .

[0106] Provision may be made, as here, for the AC / DC converter 261 to be reversible, allowing both the transfer of electrical power from the AC distribution stage 27 to the intermediate DC distribution stage 260 and vice versa.

[0107] Like the AC distribution stage 27, the intermediate DC distribution stage 260 is implemented by contactors, protection devices, busbars and other electrical conductors or connectors.

[0108] As here, the DC / AC current converters 263a, 263b, 263c, 263d electrically connecting the lift-increasing propulsion units 23a, 23b, 23c, 23d with the intermediate DC distribution stage 260 can be reversible, i.e., both authorizing the transmission of electrical power from the intermediate DC distribution stage 260 to the lift-increasing propulsion unit in question and, conversely, allowing the transmission of electrical power from the propulsion unit to the intermediate stage 260.

[0109] Furthermore, the second power supply circuit 26 is provided here with means for storing electrical energy, here a battery or a power battery pack 262 connected to the intermediate DC distribution stage 260 .

[0110] As regards the mechanical aspects, the wingtip propulsion unit 22 has one or more propellers, at least one of which is of variable pitch (i.e. a propeller whose timing can be adjusted during flight). This arrangement is advantageous because the wingtip propulsion unit 22 is intended to operate during most of the flight of the aircraft, therefore operating within a certain extended range of displacement speeds, and because its rotational speed is imposed by the rotational speed of the turboprop 21 (because the electric motor 221 here is of synchronous type).

[0111] As for the lift-increasing propulsion units 23a, 23b, 23c, 23d, they are provided here with fixed-pitch propellers (i.e. the timing of which cannot be adjusted during flight). More precisely, their propellers or all of their propellers (if they contain several propellers) are of fixed pitch. This makes it possible to advantageously simplify the structure of these propulsion units, for which the rotation speed can be adjusted more flexibly than for the wingtip propulsion units 22 (due to the intermediate conversion to direct current).

[0112] Note that the term "propeller" herein generally designates a propulsion member comprising blades fixed to a shaft, whether a streamlined propeller (sometimes called a "fan") or a non-streamlined propeller.

[0113] The second propulsion system 30 (right propulsion system) is here identical (or at least similar) to the first propulsion system 20. In addition to its propulsion units 31, 32, 33a-33d and its alternator 34, the second propulsion system 30 thus comprises:

[0114] - a first power supply circuit 35 which is identical to the first circuit 25 described above, and

[0115] a second power supply circuit 36 ​​identical to the second circuit 26 .

[0116] Thus, the first circuit 35 comprises an AC distribution stage 37 (common to the second circuit 36 ​​), and actuation and synchronization means 351 connected to the wingtip propulsion units 32 .

[0117] Furthermore, the second circuit 36 ​​comprises in particular:

[0118] - Intermediate DC distribution level 360,

[0119] - an AC / DC converter 361 connected between the AC distribution stage 37 and the intermediate DC distribution stage 360, here reversible,

[0120] - for each lift-increasing propulsion unit 33a-33d, here a reversible DC / AC converter 363a-363d, which electrically connects the electric motor 331a-331d (alternating current) of the lift-increasing propulsion unit in question with the intermediate DC distribution stage 360, and

[0121] A power battery pack 362 connected to the intermediate stage 360 ​​.

[0122] The wingtip propulsion unit 32 of the second propulsion system 30 comprises (like the first propulsion system) an alternating current motor 321 , here of synchronous type, which drives one or more propellers, at least one of which 320 is of variable pitch.

[0123] The first propulsion system 20 and the second propulsion system 30 also comprise here a common electronic control unit 14. This control unit 14 communicates with the motors, converters, contactors and other actuators of the two propulsion systems and is able to control them.

[0124] The control unit 14 is here programmed to control the motors of the lift-increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d so that these propulsion units deliver mechanical propulsion power during the take-off, approach, landing phases and even during the taxiing phase, these propulsion units being at least partially, here completely, powered by the power batteries 262, 362 during the flight or displacement phase in question.

[0125] This arrangement makes it possible to reduce the emission of polluting gases during these flight and displacement phases, since part of the power required for the propulsion of the aircraft is then supplied by the power batteries 262, 362, which makes it possible to reduce as much as possible the power that the turbopropellers must supply for take-off or landing of the aircraft. This advantageously reduces atmospheric pollution in the airport area and in the vicinity of the airport.

[0126] The control unit 14 is also programmed to control the motors of the lift-increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d so that these propulsion units remain switched off during most of the cruising phases during flight of the aircraft, even during the climbing phases.

[0127] This arrangement is beneficial in terms of fuel consumption. In fact, in order to operate the lift-increasing propulsion units 23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d throughout the cruise phase, it is necessary to power them through the generators 24, 34, since the storage capacity of the power batteries 262, 362 is necessarily limited (in order to avoid overweighting the aircraft) and since a large part of the initial load of these batteries is consumed during the take-off phase. However, taking part of the mechanical power generated by the turbines 211, 311 of the turboprops 21, 31 in order to convert it into electricity in order to subsequently power the lift-increasing propulsion units is generally much more consuming than using this mechanical power directly to drive the propellers of the turboprops (in any case, throughout the cruise phase, during which the average altitude of the aircraft is constant).

[0128] Furthermore, the control unit 14 is also programmed to control the electric motors 221 , 321 of the wingtip propulsion units 22 , 32 to deliver mechanical propulsion power during most of the cruising phase of the aircraft's flight and even also during most of the climbing phase of this flight.

[0129] The control unit 14 can even be programmed as here to control the electric motors 221, 321 of the wingtip propulsion units 22, 32 to deliver mechanical propulsion power throughout the take-off, climb, cruise and landing phases of the aircraft (during the descent phase, the wingtip propulsion units can, on the other hand, be controlled to operate as mechanical power receivers and therefore as electric generators).

[0130] These arrangements are also beneficial in terms of fuel consumption. In fact, despite the losses associated with the mechanical / electrical conversion (through the generator) and then the electrical / mechanical conversion (through the motors of the wingtip propulsion units), the wingtip propulsion units 22, 32 allow a significant reduction in the wingtip drag, which significantly contributes to the total drag experienced by the aircraft.

[0131] However, the importance of minimizing the power losses in the first circuit 25, 35 connecting the generator 24, 34 and the wingtip propulsion units 22, 32 is understandable, since these propulsion units operate and deliver mechanical propulsion power during most of the flight of the aircraft. Furthermore, in order to limit these losses as much as possible, a somewhat direct electrical connection is used between the generator and the wingtip propulsion units, without AC / DC conversion.

[0132] In summary, the architecture of the first and second propulsion systems 20, 30 enables:

[0133] - reducing overall fuel consumption during the entire flight (particularly relative to an aircraft comprising only turboprops) by operating the wingtip propulsion units with a "direct" generator-propulsion unit connection (without AC / DC conversion) during most of the aircraft's flight, and

[0134] -Through the take-off, landing and taxiing phases Using batteries Powering the lift increasing propulsion units, which is made possible by the structure of the second circuit 26, 36, with an intermediate DC level, reduces atmospheric pollution in the airport area.

[0135] Furthermore, the supply of power to the lift-increasing propulsion units 23a-23d, 33a-33d via the intermediate DC distribution stages 260, 360 and the DC / AC current converters 263a-263d, 363a-363d makes it possible to control the rotation speed of these propulsion units electronically very flexibly, in particular independently of the rotation speed of the turboprops 21, 31. This makes it possible, in particular, to dispense with the need for variable pitch propellers for these propulsion units, thereby simplifying their construction.

[0136] Furthermore, the provision of an intermediate DC distribution stage 260, 360 of a second circuit 26, 36 with a battery, and the reversible nature of the DC / AC current converters 263a-263d, 363a-363d, make it possible to recover mechanical energy during the aircraft's descent phase (by operating the lift-increasing propulsion unit as a mechanical receiver - somewhat like an air turbine, according to the expression "windmill") and to store the recovered energy in electrical form in the power batteries 262, 362, as explained below.

[0137] The different operating modes of the first and second propulsion systems 20 , 30 associated with different flight or operating phases of the aircraft shall now be described in more detail.

[0138] Here, the control unit 14 is specifically programmed to control the first and second propulsion systems 20, 30 so as to implement one or the other of these operating modes (depending on the flight phase of the aircraft). In particular, the control unit 14 can be programmed so that:

[0139] - the selection of one or another of these operating modes as a function of data received by the control unit representing the ongoing flight phase (data specifying, for example, that the ongoing phase is a take-off phase or, on the contrary, a cruising phase) and / or representing a control selection by the pilot of the aircraft or by an onboard computer of the aircraft and / or representing the state of the aircraft (for example the state of charge of its propulsion batteries 262, 362), and

[0140] - Controlling the various actuators of the propulsion system 20 , 30 (motors, converters, contactors, etc.) according to the operating mode thus selected.

[0141] Figure 6 The various phases (reference symbols FP1 to FP8 ) of a typical flight of an aircraft 1 are schematically shown over time t. Figure 6 The phases during which each of these propulsion units is a motor (and possibly a receiver) during the flight are also shown for the various propulsion units of the aircraft by means of a timing diagram.

[0142] As can be seen from the figure, the flights in question include (in this order):

[0143] - FP1 during the taxiing phase,

[0144] - Take-off phase FP2,

[0145] - FP3 during the climb phase,

[0146] - Cruise phase FP4,

[0147] - descent phase FP5,

[0148] - FP6 during the approach phase,

[0149] - Landing phase FP7, and

[0150] - Another sliding phase FP8 for displacement on the ground.

[0151] exist Figure 6 In the diagram, for each phase and for each propulsion unit, a grey disc indicates that the propulsion unit under consideration operates as a "motor" during the phase in question, i.e. supplies mechanical propulsion power. In contrast, a white disc (i.e. a black circle filled with white, which may be dotted or dashed) indicates that the propulsion unit operates as a mechanical power sink (as a generator) during the phase in question, while the absence of a disc indicates that the propulsion unit is switched off (does not exchange energy) for most of the phase.

[0152] A similar convention is used for the sources of electrical energy, namely the generators 24, 34 and the power batteries 262, 362. A grey disc indicates that the source under consideration is outputting during the flight or displacement phase under consideration, a white disc indicates that the source is receiving electrical power (positive), and no disc indicates that the source has no output and is not receiving any electrical power.

[0153] For certain phases (climb phase FP3 and descent phase FP5), a disk surrounded by a dotted line indicates that the associated energy exchange is optional (or it may take place only during a part of the phase considered).

[0154] For the cruising phase FP4, the white disk surrounded by the dotted line indicates that the energy exchange in question (charging of the power battery) takes place only during a part of the cruising phase.

[0155] The operating modes associated with these different flight phases are now described one by one.

[0156] In the operating mode corresponding to the taxiing phase FP1 or FP8 of displacement on the ground, the displacement of the aircraft 1 is provided by the lift-increasing propulsion units 23a-23d, 33a-33d powered by the power batteries 262, 362. As for the turbopropellers 21, 31 and the wingtip propulsion units 22, 32, they are switched off in this operating mode.

[0157] In the operating mode corresponding to the take-off phase FP2, the various propulsion units 21, 22, 23a-23d, 31, 32, 33a-33d of the aircraft participate in its propulsion. The lift-increasing propulsion units 23a-23d, 33a-33d are powered by power batteries 262, 362 and possibly also by generators. The wingtip propulsion units 22, 32 are powered by (turboprop-driven) generators 24, 34.

[0158] In the operating mode corresponding to the climb phase FP3, the propulsion of the aircraft is ensured by the turbopropellers 21, 31 and by the wingtip propulsion units 22, 32, the latter being powered by the generators 24, 34. As for the lift-increasing propulsion units 23a-23d, 33a-33d, they are switched off. In this operating mode, the power batteries (partially depleted during takeoff) are selectively recharged by the generators, or at least these batteries do not output.

[0159] In the operating mode corresponding to the cruising phase FP4, the propulsion of the aircraft is provided by the turbopropellers 21, 31 and by the wingtip propulsion units 22, 32, the latter being powered by the generators 24, 34. As for the lift-increasing propulsion units 23a-23d, 33a-33d, they are switched off (except possibly during brief altitude change phases). In this operating mode, the power batteries (partially depleted during take-off) are recharged by the generators and then, once these batteries are fully charged, they no longer intervene in the energy exchange. It may also be provided that, during the cruising phase or the climbing phase, the charging of the batteries is stopped before they have reached their maximum charge level in order to preserve a storage margin in order to be able to store in electrical form the mechanical energy recovered by the electric propulsion units operating as receivers during descent.

[0160] In the operating mode corresponding to the descent phase FP5, the propulsion of the aircraft is provided here by the turbopropellers 21, 31. During at least a part of the descent, it is provided here that the wingtip propulsion units 22, 32 and the lift-increasing propulsion units 23a-23d, 33a-33d are optionally operated as receivers, and the energy they recover is stored in the battery. This energy recovery in the form of electricity is made possible in particular by the reversible nature of the DC / AC current converters 263a-263d, 363a-363d. During this entire period, the generators 24, 34 have no output. During the descent, when the electric propulsion units are not operated as receivers (for example because the batteries are full), it is provided here that no electrical energy is supplied to them.

[0161] In the operation mode corresponding to the approach phase FP6 and the landing phase FP7, the various propulsion units 21, 22, 23a-23d, 31, 32, 33a-33d of the aircraft participate in its propulsion. During these phases, the lift increase propulsion units 23a-23d, 33a-33d are powered by power batteries 262, 362 and may also be powered by generators. The wingtip propulsion units 22, 32 are powered by (turbopropeller driven) generators 24, 34. During this phase, the lift increase propulsion units 23a-23d, 33a-33d can participate in generating reverse thrust for braking of the aircraft. And the wingtip propulsion units 22 and 32 make it possible to partially compensate for the thrust, so as to control and / or increase the maneuverability of the aircraft, particularly in the case of crosswind or interference by undesirable air movement.

[0162] These different operating modes and the flight phases associated therewith are described by way of example and various modifications may be made thereto.

[0163] Thus, for example, provision can be made for the wingtip propulsion units 22 , 32 to be supplied with power by the generators 24 , 34 during the descent phase or a part of this phase.

[0164] Provision may also be made for the wingtip propulsion units 22 , 32 to be powered by the generators 24 , 34 during the approach and landing phases, or to be switched off.

[0165] The control unit 14 can also be programmed to implement a specific operating mode for starting the wingtip propulsion units 22, 32. In this operating mode, the wingtip propulsion units 22, 32 are started (on the ground) or restarted (in flight) thanks to the power batteries 262, 362 (and due to the reversible nature of the converters 261, 361). This arrangement is beneficial because it makes it possible to simplify the starting and synchronization means 251, 351 (or the structure of the motors of these propulsion units). In fact, by starting the motors of the wingtip propulsion units 22, 32, which are here of the synchronous type, the synchronization problems between these motors and the generators 24, 34 at the time of starting are eliminated thanks to the power batteries 262, 362 and the converters 261, 361. And once the rotation speed of these motors approaches that of the generators, the power supply will be switched to the generators.

[0166] The control unit 14 can also be programmed to implement another specific operating mode for starting the turbopropellers 21, 31, when the generator 24, 34 is reversible and can be operated as a motor (as an electric starter). In this case, due to the reversible nature of the converter 261, 361, the generator is powered by the power battery 262, 362, in this way starting the turbopropeller.

[0167] According to the second embodiment ( Figure 2 ) of the aircraft 2 and the first embodiment ( Figure 1 ) differs from aircraft 1 in that:

[0168] - some of the lift-increasing propulsion units 23c, 23d of the first propulsion system 20 are fixed to the right wing 13 of the aircraft 2, while other propulsion units 21, 23a, 23b, 22 of this first propulsion system 20 are fixed to its left wing 12 (while in the first embodiment all the propulsion units of the first propulsion system are fixed to the same wing, i.e. the left wing), and

[0169] -Some of the lift-increasing propulsion units 33c, 33d of the second propulsion system 30 are fixed to the left wing 12 of the aircraft 2, while other propulsion units 31, 33a, 33b, 32 of the second system 30 are fixed to its right wing 13 (whereas in the first embodiment, all the propulsion units of the first propulsion system are fixed to the same wing, i.e. the left wing) .

[0170] Here, for each of the two propulsion systems 20, 30, of the four lift-increasing propulsion units of the propulsion system under consideration, two are fixed to the right wing 13 and two are fixed to the left wing 12, in such a way that these four propulsion units 23a-23d or 33a-33d form a symmetrical set relative to the sagittal plane of the mid-axis of the aircraft 2 (left-right symmetry, including with regard to the position of the propulsion units relative to the fuselage).

[0171] The arrangement can be implemented in the same way when the number N of lift increasing propulsion units per wing is a number different from 4, preferably an even number (e.g. equal to 2 or equal to 6). In this case, for each of the two propulsion systems, N / 2 lift increasing propulsion units are fixed to the left wing, while N / 2 other lift increasing propulsion units are fixed to the right wing, preferably symmetrically with respect to the N / 2 propulsion units of the left wing.

[0172] This left-right crossover between the two propulsion systems 20 , 30 makes it possible to prevent an excessive asymmetry between the increase in lift and thrust exerted respectively on the left and right sides of the aircraft 2 in the event of a failure of the left turboprop 21 or the right turboprop 31 .

[0173] In fact, if the right turboprop 31 becomes inoperative (no longer rotating), for example, due to this left-right “crossover”, it will still be possible to power part of the propulsion units of the right wing (propulsion units 23c, 23d) using the left generator 24. Therefore, the aircraft can be propelled on the left by the left turboprop 21 and electric propulsion units 22, 23a and 23b, and on the right by electric propulsion units 23c and 23d (even when the power battery 362 is empty), thereby preventing excessive thrust asymmetry between the left and right sides of the aircraft.

[0174] In other respects, the aircraft 2 of the second embodiment is identical to the aircraft 1 of the first embodiment.

[0175] According to the third embodiment, the aircraft 3 ( Figure 3 and Figure 4 ) and the aircraft 2 of the second embodiment ( Figure 2 ) are the same, except that in this third embodiment:

[0176] The wingtip propulsion unit 22 of the first propulsion system 20 (the “left” system) is fixed at the tip of the right wing 13 .

[0177] The wingtip propulsion unit 32 of the second propulsion system 30 (“right” system) is fixed at the tip of the left wing 12 .

[0178] To improve clarity, Figure 3 In FIG. 1 , the aircraft 2 and its first propulsion system 20 are shown, but the second propulsion system 30 is not shown. Figure 4 , the aircraft 2 and its second propulsion system 30 have been shown, but the first propulsion system 20 has not been shown.

[0179] In this third embodiment, the left-right "crossover" between the first propulsion system and the second propulsion system therefore involves more propulsion units than in the second embodiment, which makes it possible to further improve the left-right symmetry of thrust (and lift increase) in the event that one of the turbopropellers 21, 31 becomes inoperative.

[0180] Thus, if turboprop 31 becomes inoperative, for example, propulsion of the aircraft can still be provided: on the left, by the left turboprop 21 and the electric propulsion units 23a and 23b, and on the right, by the electric propulsion units 23c, 23d and 22.

[0181] Note that the aircraft may be implemented according to another embodiment not shown, in which:

[0182] - the wingtip propulsion units of the first propulsion system (the "left" system) will be fixed at the tip of the right wing, while the wingtip propulsion units of the second propulsion system (the "right" system) will be fixed at the tip of the left wing (as in the third embodiment),

[0183] - but wherein all the lift-increasing propulsion units of the first system will be located on the left side of the fuselage, and all the lift-increasing propulsion units of the second system will be located on the right side of the fuselage.

[0184] In the fourth embodiment of the aircraft 4 ( Figure 5 ), each electric propulsion unit comprises two inputs (more precisely two sets of input terminals), which makes it possible to power the propulsion unit using one or the other of the two inputs. One of the two inputs is electrically connected to the generator 24 of the first propulsion system 20', while the other input is electrically connected to the generator 34 of the second propulsion system 30', in this way being able to power the propulsion unit via one or the other of the two generators 24, 34.

[0185] Thanks to this arrangement, even if one of the turbopropellers becomes inoperative, all the electric propulsion units of the aircraft 4 can still be powered by the generator of the other propulsion unit, which makes it possible to maintain a relatively symmetrical thrust (and lift increase) between the left and right sides of the aircraft (and even when the power batteries are empty).

[0186] Furthermore, for the first propulsion system, as for the second propulsion system 20', 30', the AC distribution stage 27, 37, the intermediate DC distribution stage 260, 360, the power batteries 262, 362 and the converters 261, 263a-263d, 361, 363a-363d of the propulsion system are duplicated. This redundancy further increases the reliability of the aircraft.

[0187] In addition to the above-mentioned elements, the first propulsion system 20' therefore also includes ( Figure 5 ):

[0188] - Additional AC distribution stage 27',

[0189] - an additional intermediate DC distribution stage 260',

[0190] - one or more additional power batteries 262',

[0191] - Additional AC / DC converter 261 ',

[0192] - for each lift increasing propulsion unit 23a-23d, an additional DC / AC converter 263a'-263d', and

[0193] - Additional starting and synchronization means 251 '.

[0194] In the same way, in addition to the elements already mentioned, the second propulsion system 30' comprises:

[0195] - Additional AC distribution stage 37',

[0196] - additional intermediate DC distribution stage 360',

[0197] - one or more additional power batteries 362',

[0198] - Additional AC / DC converter 361 ',

[0199] - for each lift increasing propulsion unit 33a-33d, an additional DC / AC converter 363a'-363d', and

[0200] - Additional starting and synchronization means 351 '.

[0201] For each lift increasing propulsion unit 23a-23d, 33a-33d, one of the two inputs of the propulsion unit is connected to a DC / AC converter 263a-263d, 363a-363d, while the other input is connected to an additional DC / AC converter 263a'-263d', 363a'-363d'.

[0202] For each wingtip propulsion unit 22 , 32 , one of the two inputs of the propulsion unit is connected to the activation and synchronization means 251 , 351 , while the other input is connected to the additional activation and synchronization means 251 ′, 351 ′.

[0203] As described above, in the first propulsion system 20', the AC distribution stage 27 is connected on the one hand to the generator 24 and on the other hand to the intermediate DC distribution stage 260 (via the converter 261) and to the wingtip propulsion units 22 of the left wing (via the starting device 251). The intermediate DC stage 260 supplies (via the converters 263a, 263b, 363a', 363b') with power the two lift increasing propulsion units 23a, 23b of the left wing 12 and the two lift increasing propulsion units 33a, 33b of the right wing.

[0204] The additional AC distribution stage 27' is also connected to the generator 24. Furthermore, it is connected to the wingtip propulsion unit 32 of the right wing 13 (via an additional starting and synchronizing device 351 ') and to the additional intermediate DC stage 360' (via an additional AC-DC converter 361 ').

[0205] The additional intermediate DC stage 260' is connected to the additional AC distribution stage 37' of the second propulsion system 30' via an additional AC-DC converter 261'. The additional intermediate stage DC 260' supplies (via converters 263c, 263d, 363c', 363d') the two lift increasing propulsion units 23c, 23d of the left wing 12 and the two lift increasing propulsion units 33c, 33d of the right wing.

[0206] The additional starting device 251 ′ of the wingtip propulsion unit 22 of the left wing is also connected to the additional AC distribution stage 37 ′ of the second propulsion system.

[0207] The elements of the second propulsion system 30' are connected together and to the elements of the first propulsion system 20' in the same manner as just presented for the first system 20'.

[0208] Thus, in the second propulsion system 30', the AC distribution stage 37 is connected on the one hand to the generator 34 and on the other hand to the intermediate DC distribution stage 360 ​​(via the converter 361) and to the wingtip propulsion units 32 of the right wing (via the starting device 351). The intermediate DC stage 360 ​​supplies (via the converters 263a', 263b', 363a, 363b) the two lift increasing propulsion units 23a, 23b of the left wing 12 and the two lift increasing propulsion units 33a, 33b of the right wing.

[0209] The additional AC distribution stage 37' is connected to the generator 34. Furthermore, it is connected to the wingtip propulsion unit 22 of the left wing 12 (via the additional starting and synchronizing device 251 ') and to the additional intermediate DC stage 260' (via the additional AC-DC converter 261 ').

[0210] The additional intermediate DC stage 360' is connected to the additional AC distribution stage 27' of the first propulsion system via an additional AC-DC converter 361'. The additional intermediate DC stage 360' supplies (via converters 263c', 263d', 363c, 363d) two lift increasing propulsion units 23c, 23d of the left wing 12 and two lift increasing propulsion units 33c, 33d of the right wing.

[0211] In addition to those already mentioned, different alternatives to the embodiment just described are possible and other embodiments of the aircraft or of the propulsion system are conceivable.

[0212] For example, the first propulsion system and the second propulsion system may include non-propulsion turbines instead of turbopropellers, and then the generator of each propulsion unit is driven by the turbine (non-propulsion) of that system. Then, the way of controlling the propulsion system is different from that proposed above (cf. Figure 6 ). In fact, due to the absence of a turboprop, in this case it is necessary to operate the lift-increasing propulsion units during a significant part of the climb or cruise phases (or even during the entire duration of these phases).

[0213] Furthermore, instead of equipping the aircraft with two propulsion systems, each provided with a turbine, as described above, it is possible to equip the aircraft with a single propulsion system, comprising:

[0214] - exactly one turbine, which may be, for example, the turbine of a turboprop located in the front part of the fuselage,

[0215] - two wingtip thruster units, one fixed at the tip of the left wing and the other fixed at the tip of the right wing,

[0216] - and, on each wing, one or more lift-increasing propulsion units located between the fuselage and the wingtip propulsion units of that wing.

[0217] In this last propulsion system, the two wingtip propulsion units will be connected to a (sole) generator so as to be powered by the latter, without intermediate AD / DC conversion, as described above, and the lift-increasing propulsion units will, in contrast, be connected to this generator via AC / DC and AC converters and via one or more intermediate DC distribution stages provided with power batteries.

Claims

1. A propulsion system (20, 30; 20', 30') for a non-rotorcraft (1; 2; 3; 4), comprising: - an alternating current generator (24, 34), - at least one wingtip propulsion unit (22, 32), said at least one wingtip propulsion unit (22, 32) comprising an AC motor (221, 321), said at least one wingtip propulsion unit (22, 32) having a direction of rotation opposite to the formation of a wingtip vortex, - at least one lift increasing propulsion unit (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) comprising an AC motor, - a first AC power supply circuit (25, 35) electrically connecting the generator (24, 34) to the wingtip propulsion unit (22, 32), and - a second AC power supply circuit (26, 36) electrically connecting the generator (24, 34) to the lift-increasing propulsion unit (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d), - The propulsion system (20, 30; 20', 30') is characterized in that the second AC power supply circuit (26, 36) comprises: Intermediate DC distribution stages (260, 360), one or more power batteries (262, 362) connected to the intermediate DC distribution stage (260, 360), an AC / DC converter (261, 361) electrically connecting the generator (24, 34) to the intermediate DC distribution stage (260, 360), and DC / AC converters (263a, 263b, 263c, 263d, 363a, 363b, 363c, 363d), It electrically connects the intermediate DC distribution stage (260, 360) with the lift increasing propulsion units (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d), - and the first AC power supply circuit (25, 35) is configured to deliver the AC current generated by the generator (24, 34) to the wingtip propulsion unit (22, 32) without intermediate conversion of the alternating current into direct current.

2. The propulsion system (20, 30; 20', 30') according to claim 1, further comprising a turbopropeller (21, 31).

3. The propulsion system (20, 30; 20', 30') according to claim 1, - wherein the first AC power supply circuit (25, 35) and the second AC power supply circuit (26, 36) are connected to each other via an AC distribution stage (27, 37) common to the two AC power supply circuits, the AC distribution stage (27, 37) itself being connected to the generator (24, 34), the AC / DC converter (261, 361) of the second AC power supply circuit (26, 36) being connected between the AC distribution stage (27, 37) and the intermediate DC distribution stage (260, 360), - and among them, The AC / DC converter (261, 361) is reversible and allows both the transfer of electric power from the AC distribution stage (27, 37) to the intermediate DC distribution stage (260, 360) and the transfer of electric power from the intermediate DC distribution stage (260, 360) to the AC distribution stage (27, 37).

4. A propulsion system (20, 30; 20', 30') according to claim 1, wherein the DC / AC converter (263a, 263b, 263c, 263d, 363a, 363b, 363c, 363d) of the second AC power supply circuit (26, 36) is reversible, and the converter allows both the transmission of electrical power from the intermediate DC distribution stage (260, 360) to the lift-increasing propulsion units (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) and the transmission of electrical power from the lift-increasing propulsion units to the intermediate DC distribution stage (260, 360).

5. The propulsion system (20, 30; 20', 30') according to claim 1, further comprising an electronic control unit (14) comprising at least one processor and one memory, the control unit (14) being programmed to control the electric motors of the lift-increasing propulsion units (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) during the flight of the aircraft, in particular including the take-off phase (FP2), the cruising phase (FP4) and the landing phase (FP7), so that the propulsion units: - delivering mechanical propulsion power during take-off (FP2) or landing (FP7), - But remains closed during most of the cruise phase (FP4).

6. A propulsion system (20, 30; 20', 30') according to claim 5, wherein the control unit (14) of the propulsion system is also programmed to: control the electric motors (221, 321) of the wingtip propulsion units (22, 32) to deliver mechanical propulsion power during most of the flight of the aircraft.

7. The propulsion system (20, 30; 20', 30') of claim 1, wherein the lift-increasing propulsion unit (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) comprises a fixed pitch propeller.

8. The propulsion system (20, 30; 20', 30') of claim 1, wherein the wingtip propulsion unit (22, 32) comprises a variable pitch propeller (220, 320).

9. Non-rotorcraft (1; 2; 3; 4), including: - a fuselage (11), a left wing (12) extending to the left side of the fuselage, and a right wing (13) extending to the right side of the fuselage, - a first propulsion system (20; 20') and a second propulsion system (30; 30'), each according to claim 1, - the wing tip propulsion units (22, 32) of the first propulsion system and the second propulsion system are located at the tip of the left wing (12) and the tip of the right wing (13), respectively, or vice versa, - lift-increasing propulsion units (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) are located between the fuselage (11) and the wingtip propulsion units (22, 32) of the aircraft.

10. Aircraft (2; 3; 4) according to the preceding claim, wherein: - the first propulsion system (20; 20') comprises at least two lift-increasing propulsion units (23a, 23b, 23c, 23d), one (23a, 23b) being located on the left side of the fuselage (11) and the other (23c, 23d) being located on the right side of the fuselage (11), both lift-increasing propulsion units (23a, 23b, 23c, 23d) being electrically connected to an intermediate DC distribution stage (260) of the first propulsion system (20; 20'), and wherein - The second propulsion system (30; 30') comprises at least two lift-increasing propulsion units (33a, 33b, 33c, 33d), one (33c, 33d) being located on the left side of the fuselage (11) and the other (33a, 33b) being located on the right side of the fuselage (11), both lift-increasing propulsion units (33a, 33b, 33c, 33d) being electrically connected to an intermediate DC distribution stage (360) of the second propulsion system (30; 30').

11. An aircraft (3; 4) according to claim 9, wherein - the first propulsion system (20; 20') and the second propulsion system (30; 30') each comprise a turbopropeller (21, 31), - a turbopropeller (21) of the first propulsion system (20; 20') driving a generator (24) of the first propulsion system is located on the left side of the fuselage (11), while a wingtip propulsion unit (22; 32) of the first propulsion system is located at the tip of the right wing (13) of the aircraft, and wherein The turbopropeller (31) of the second propulsion system (30; 30') driving the generator (34) of the second propulsion system is located on the right side of the fuselage (11), while the wingtip propulsion unit (32; 22) of the second propulsion system is located at the tip of the left wing (12) of the aircraft.

12. An aircraft (4) according to claim 9, wherein each wingtip propulsion unit (22, 32) and each lift-increasing propulsion unit (23a, 23b, 23c, 23d, 33a, 33b, 33c, 33d) is electrically connected to the generator (24) of the first propulsion system (20') on the one hand and to the generator (34) of the second propulsion system (30') on the other hand so as to be powered indifferently by one or the other of the two generators (24, 34).

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