Aircraft propulsion system comprising a gas turbomachine and an electric machine mounted on two rotating shafts

Abstract

A propulsion unit comprising a gas turbomachine and an electric machine (3) comprising a plurality of elementary electric machines (31), positioned circumferentially around a first electric machine shaft (4) and a second electric machine shaft (5) at the same radial distance, the first electric machine shaft (4) and the second electric machine shaft (5) extending along the same longitudinal axis (W), the plurality of elementary electric machines (31) defining at least a first set of elementary electric machines (31A) and a second set of elementary electric machines (31B), the first set of elementary electric machines (31A) being mechanically connected at least to the first electric machine shaft (4) and the second set of elementary electric machines (31B) being mechanically connected at least to the second electric machine shaft (5). Abstract figure: Figure 4

Description

Title of the invention: Aircraft propulsion system comprising a gas turbomachine and an electric machine mounted on two rotating shafts technical field

[0001] The present invention relates to the field of propulsion assemblies used for the propulsion of an aircraft and relates in particular to a propulsion assembly comprising a gas turbomachine associated with an electric machine that can operate in a motor mode to provide electric propulsion or in a generator mode to power, for example, an electric battery or an electrical network of the aircraft.

[0002] In a known manner, an aircraft includes a turbomachine enabling participation in the propulsion of an aircraft from the acceleration of an airflow circulating from upstream to downstream.

[0003] A propulsion assembly is known comprising a gas turbomachine driving a propulsion element, commonly referred to as a "fan", for providing propulsion to an aircraft. The gas turbomachine extends axially along the longitudinal axis and comprises, in a known manner, a low-pressure body and a high-pressure body.

[0004] In order to improve the operability of a turbomachine depending on flight conditions, it is known to provide an electric machine, mounted on one of the components, particularly a high-pressure one, to drive it in rotation. The electric machine can alternatively store energy to power an electrical network or recharge a battery.

[0005] In this respect, an electrical machine is known from document US20170320584A1 enabling the transfer of energy to a shaft of a turbomachine. With reference to [Fig. 1], the electric machine M comprises a plurality of elementary electric machines ME, distributed circumferentially around a shaft A to be driven. Each elementary electric machine ME comprises an elementary rotor and an elementary drive ring CE mounted on the elementary rotor and which cooperates with a toothed ring C mounted on the shaft A. The rotation of all the elementary drive rings CE drives the toothed ring C in rotation and vice versa, according to the operating mode of the electric machine M (motor or generator as described previously).

[0006] In document US20170320584A1, all the elementary electrical machines ME are identical and rotate at the same speed so as to be able to assist the turbomachine, for example, when the latter does not supply enough energy. In other words, the elementary electrical machines function- work together to provide energy in a way that meets a unique, specific need.

[0007] It has been proposed to use the electric machine to drive several independent shafts in order to drive, in particular, accessory equipment of the turbine. Due to its structure, the electric machine can only drive the shafts at the same rotational speed, which is of limited use.

[0008] To eliminate this drawback, one solution would be to use two separate electrical machines or to add a gearbox to the electrical machine. Such arrangements are complex and significantly increase the overall size.

[0009] The invention thus aims to eliminate at least some of these disadvantages by proposing a propulsion unit comprising a turbomachine and an electric machine capable of driving two independent shafts at distinct rotational speeds, while being compact and simple to integrate into an existing propulsion unit. PRESENTATION OF THE INVENTION

[0010] The invention relates to a propulsion system for the propulsion of an aircraft, the propulsion system comprising: • a gas turbomachine comprising at least one first rotating turbomachine shaft and a second rotating turbomachine shaft, • an electrical machine comprising a plurality of elementary electrical machines, the plurality of elementary electrical machines being positioned circumferentially around a first electrical machine shaft and a second electrical machine shaft at the same radial distance, the first electrical machine shaft and the second electrical machine shaft extending along the same longitudinal axis, the first electrical machine shaft being mechanically connected to the first turbomachine shaft, the second electrical machine shaft being mechanically connected to the second turbomachine shaft, the plurality of elementary electrical machines defining at least a first set of elementary electrical machines and a second set of elementary electrical machines.

[0011] The propulsion assembly is remarkable in that the first set of elementary electrical machines is mechanically connected at least to the first electrical machine shaft and the second set of elementary electrical machines is mechanically connected at least to the second electrical machine shaft.

[0012] Such a propulsion system in which two sets of electrical machines are connected to two different shafts allows the two shafts to be driven independently to meet, for example, two distinct needs. Two independently driven shafts can also rotate at two different speeds, this which allows it to meet different specific needs. In other words, thanks to the invention, the two sets of electrical machines can be completely separated to operate independently.

[0013] Thanks to the invention, two shafts connected to a propulsion unit can rotate independently by means of two separate sets of electrical machines, mounted in a single electrical machine. The overall size of the propulsion unit according to the invention is thus advantageously limited.

[0014] In addition, two separate sets of electrical machines can allow, for example, the first set of electrical machines to receive energy, for example to recharge a battery, and the second set of electrical machines to supply energy to power a motor, for example.

[0015] In one embodiment, the gas turbomachine comprising a number of rotating shafts strictly greater than two, the plurality of elementary electrical machines of the electrical machine defining a number of sets of electrical machines strictly greater than two, each set of electrical machines is mechanically connected to a separate shaft.

[0016] In one embodiment, the first electric machine shaft is the first turbomachine shaft and the second electric machine shaft is the second turbomachine shaft. In this embodiment, the electric machine is mounted in the immediate vicinity of the turbomachine shafts.

[0017] In a second embodiment, the first electric machine shaft is separate from the first turbomachine shaft, and the second electric machine shaft is separate from the second turbomachine shaft. The first and second electric machine shafts preferably cooperate by means of gears with the first and second turbomachine shafts. In this embodiment, the electric machine is preferably mounted in an accessory gearbox for the turbomachine, or AGB for "Auxiliary Gear Box".

[0018] Preferably, the propulsion assembly comprises a first main drive ring mounted rigidly on the first electric machine shaft and coaxial with the first electric machine shaft, and a second main drive ring mounted rigidly on the second electric machine shaft and coaxial with the second electric machine shaft. This configuration allows the two drive rings to operate independently.

[0019] In one embodiment, the first main drive ring is a first gear ring and the second main drive ring is a second gear ring.

[0020] In a first embodiment, the first main drive ring and the second main drive ring comprise drive teeth, the first main drive ring and the second main drive ring having a similar diameter, the first main drive ring and the second main drive ring have different numbers of teeth, advantageously allowing a different reduction ratio between the two rotating shafts. The two rotating shafts can thus easily rotate at different speeds.

[0021] In a second embodiment, the first main drive ring and the second main drive ring comprise drive teeth, the first main drive ring and the second main drive ring having a similar diameter, and the first main drive ring and the second main drive ring having the same number of teeth. In such a configuration, the two main drive rings can thus rotate at identical speeds while operating independently.

[0022] In a third embodiment, the first main drive ring and the second main drive ring comprise drive teeth, the first main drive ring and the second main drive ring having a different diameter, the first main drive ring and the second main drive ring having the same number of teeth. In such a configuration, the two main drive rings can thus rotate at different speeds while operating independently.

[0023] Preferably, each elementary electric machine in the plurality of elementary electric machines comprises an auxiliary drive ring configured to rotate about an axis of rotation parallel to the longitudinal axis. The auxiliary drive ring of each elementary electric machine in the first set of elementary electric machines cooperates with the first main drive ring mounted on the first electric machine shaft, and the auxiliary drive ring of each elementary electric machine in the second set of elementary electric machines cooperates with the second main drive ring mounted on the second electric machine shaft. Such a configuration allows the auxiliary drive rings of the two sets of electric machines to be connected separately to the two main drive rings mounted on the two different shafts.

[0024] In a preferred embodiment, the electric machine circumferentially comprises an alternation of elementary electric machines belonging to the first The first set consists of elementary electrical machines and elementary electrical machines belonging to the second set of elementary electrical machines. The elementary electrical machines of both sets of electrical machines are thus distributed in a balanced manner around the circumference of the electrical machine, further enabling a drive distributed around the circumference of the electrical machine.

[0025] Preferably, the elementary electrical machines of the first set of elementary electrical machines and the second set of elementary electrical machines are distributed circumferentially in a homogeneous manner around the longitudinal axis. The electrical machine is thus balanced, thanks to the distribution of the masses of the elementary electrical machines, which makes it possible to limit the occurrence of excessive mechanical stresses in the electrical machine.

[0026] In a preferred embodiment, each elementary electric machine comprising an elementary stator, the electric machine comprising a first stator formed by the plurality of elementary stators of the first set of elementary electric machines and a second stator formed by the plurality of elementary stators of the second set of elementary electric machines, the first stator and the second stator are connected respectively to a first power device and a second power device. Two independent power devices allow the flow of electric current in the two stators to be controlled independently. The rotational speeds of the first and second electric machine shafts can thus be easily controlled independently of each other.

[0027] Preferably, the first stator and the second stator have the same axial position. The first stator and the second stator are preferably advantageously nested one inside the other, thereby reducing the overall size of the electrical machine.

[0028] In one embodiment, each elementary electrical machine of the first set of elementary electrical machines is configured to rotate at a first rotational speed, and each elementary electrical machine of the second set of elementary electrical machines is configured to rotate at a second rotational speed different from the first rotational speed. Each rotating electrical machine shaft can thus rotate at its own rotational speed. The two electrical machine shafts rotating at different speeds make it possible to simultaneously supply two separate energy sources, for example, to two different pieces of equipment with different requirements.

[0029] In one embodiment, each elementary electrical machine of the first set of elementary electrical machines being configured to rotate according to a In the first direction of rotation, each elementary electrical machine in the second set of elementary electrical machines is configured to rotate in a second direction different from the first direction of rotation. Each rotating electrical machine shaft can thus rotate in its own direction of rotation. The two electrical machine shafts can rotate in a counter-rotating manner.

[0030] In one embodiment, the first set of electrical machines is mechanically connected only to the first electrical machine shaft and the second set of electrical machines is mechanically connected only to the second electrical machine shaft, allowing independent operation of the two sets of electrical machines.

[0031] In an alternative embodiment, at least one elementary electric machine from the first set of electric machines or the second set of electric machines is mechanically connected to both the first and second electric machine shafts. Such a configuration allows the elementary electric machine to simultaneously supply power to both electric machine shafts.

[0032] Alternatively, the first set of electrical machines and the second set of electrical machines are mechanically connected to both the first electrical machine shaft and the second electrical machine shaft.

[0033] In one embodiment, each elementary electrical machine is configured to operate in a so-called "motor" mode and in a so-called "generator" mode. Since all the elementary electrical machines in the first set of elementary electrical machines are configured to operate in the same first mode (motor or generator), all the elementary electrical machines in the second set of electrical machines are configured to operate in the same second mode (motor or generator), which is different from the first mode. It is thus possible, by means of a single electrical machine, to both store energy in a first power device and to supply energy from a second power device, for example.

[0034] Alternatively, all the elementary electrical machines of the first set of electrical machines and of the second set of electrical machines are configured to operate in the same mode (motor or generator).

[0035] In a first embodiment, the first main drive ring is positioned axially between the electric machine and the second main drive ring.

[0036] In a second embodiment, the electric machine is positioned axially between the first main drive ring and the second main drive ring.

[0037] The invention also relates to an aircraft comprising at least one propulsion assembly as described above.

[0038] The invention further relates to a method of operating a propulsion assembly as described above, the method comprising: • a rotation stage of the first electrical machine shaft driving the first set of elementary electrical machines, and • a rotation stage of the second electric machine shaft driving the second set of elementary electric machines, the second electric machine shaft rotating independently of the first electric machine shaft.

[0039] Alternatively, the invention relates to a method of operating a propulsion assembly as described above, the method comprising: • an activation step of the first set of elementary electrical machines, driving the first electrical machine shaft into rotation, and • an activation step of the second set of elementary electrical machines, causing the second electrical machine shaft to rotate. PRESENTATION OF THE FIGURES

[0040] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0041] Fig. 1 is a schematic representation of an electrical machine according to the prior art.

[0042] Fig. 2 is a schematic representation of a propulsion assembly comprising an electric machine according to a first embodiment of the invention.

[0043] Fig. 3 is a schematic representation of a propulsion assembly comprising an electric machine according to a second embodiment of the invention.

[0044] Fig. 4 is a schematic representation of the electric machine of figures 2 and 3 according to a first embodiment of the invention.

[0045] Fig. 5 is a partial cross-sectional view of the electrical machine of Fig. 4.

[0046] Figure 6 is a schematic representation of an electrical machine according to a second embodiment of the invention.

[0047] Fig. 7 is a schematic representation of the stators of the electric machine according to one embodiment of the invention.

[0048] The [Fig.8] is a diagram of the steps of a method of operation of the propulsion assembly according to an implementation method of the invention.

[0049] It should be noted that the figures explain the invention in detail to put into works the invention, the said figures being of course able to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0050] With reference to [Fig.2] and [Fig.3], the invention relates to a propulsion assembly 1 comprising a gas turbomachine 2 and an electric machine 3.

[0051] The propulsion assembly 1 extends longitudinally along an axis X and includes a propulsion element 9, configured to contribute to the propulsion of the aircraft by accelerating an airflow F flowing from upstream to downstream. The terms "upstream" and "downstream" refer to the axis X extending from the upstream to the downstream end of the propulsion assembly 1. The turbomachine 2 is configured to drive the propulsion element 9 in rotation.

[0052] As shown in [Fig. 2], the gas turbomachine 2 is a twin-body and It comprises a first body C1 and a second body C2. It is understood that the gas turbomachine 2 could have a different shape. The gas turbomachine 2 comprises a first turbomachine shaft 21 and a second turbomachine shaft 22 which are rotatably mounted about the X-axis. In this example, the first turbomachine shaft 21 and the second turbomachine shaft 22 are coaxial. In one embodiment, the second turbomachine shaft 22 extends longitudinally outside the first turbomachine shaft 21, as shown in Figures 2 and 3. It is understood that the first turbomachine shaft 21 and the second turbomachine shaft 22 could equally well extend successively from upstream to downstream along the X-axis. Furthermore, this document presents the example of two turbomachine shafts 21, 22; however, it is understood that the turbomachine 2 could comprise a different number of shafts, in particular more than two.

[0053] In this example, the first turbomachine shaft 21 belongs to the first body C1, which is of the "low pressure" type, while the second turbomachine shaft 22 belongs to the second body C2, which is of the "high pressure" type. In particular, the first turbomachine shaft 21 corresponds in this example to a low-pressure turbine shaft and the second turbomachine shaft 22 corresponds to a high-pressure compressor shaft.

[0054] The electric machine 3 is configured to operate in a so-called "motor" mode to provide electrical assistance (for example to compensate for the aerodynamic instabilities of a compressor or to contribute to the acceleration of the aircraft) or in a so-called "generator" mode to power, for example, an electric battery or an electrical network of the aircraft.

[0055] With further reference to Figures 2 and 3, the electrical machine 3 comprises a first electrical machine shaft 4 and a second electrical machine shaft 5. The first electrical machine shaft 4 is mechanically connected to the first shaft of turbomachine 21 and the second electric machine shaft 5 is mechanically connected to the second turbomachine shaft 22.

[0056] In a first embodiment, shown in [Fig.2], the first electric machine shaft 4 corresponds to the first turbomachine shaft 21 and the second electric machine shaft 5 corresponds to the second turbomachine shaft 22. In other words, in this embodiment, the electric machine 3 is mounted directly in the turbomachine 2, for example in the primary shaft.

[0057] In a second embodiment, shown in [Fig.3], the first electric machine shaft 4 and the second electric machine shaft 5 are separate from the first turbomachine shaft 21 and the second turbomachine shaft 22. In other words, in this embodiment, the electric machine 3 is mounted in the turbomachine 2 externally to the primary flow (for example in the secondary flow) or outside the turbomachine 2.

[0058] According to the invention, the first electric machine shaft 4 and the second electric machine shaft 5 extend along a longitudinal axis W (in this example collinear with the longitudinal axis X of the turbomachine 2). In other words, the first electric machine shaft 4 and the second electric machine shaft 5 are coaxial. In one embodiment, the second electric machine shaft 5 extends longitudinally outside the first electric machine shaft 4, as shown in [Fig. 3]. It is understood that the first electric machine shaft 4 and the second electric machine shaft 5 could just as easily extend successively from upstream to downstream along the longitudinal axis W. Furthermore, this document presents the example of two electric machine shafts 4 and 5; however, it is understood that the electric machine 3 could comprise a different number of shafts, in particular more than two.

[0059] The first electric machine shaft 4 is configured to rotate about the longitudinal axis W at a first rotational speed vA and the second electric machine shaft 5 is configured to rotate about the longitudinal axis W at a second rotational speed vB. The first rotational speed vA and the second rotational speed vB are identical or different depending on the requirements, as will be described in more detail later.

[0060] With reference to [Fig. 4], the electric machine 3 further comprises a first main drive ring 6, fixedly mounted on the first electric machine shaft 4, and a second main drive ring 7 fixedly mounted on the second electric machine shaft 5 (also shown in [Fig. 4]). The first main drive ring 6 and the first electric machine shaft 4 are preferably coaxial, and the second main drive ring 7 and the second electric machine shaft 5 are co-axial. axial, the first main drive ring 6 and the second main drive ring 7 being configured to rotate about the longitudinal axis W. Preferably, the first main drive ring 6 and the second main drive ring 7 are in the form of toothed rings. Each main drive ring 6, 7 extends radially outwards from the electrical machine shaft 4, 5 to which it is rigidly mounted.

[0061] In one embodiment, the first main drive ring 6 and the second main drive ring 7 have a different number of teeth, in order to obtain a different reduction ratio between the two rings 6 and 7, as will be described in more detail later. It is understood that the first main drive ring 6 and the second main drive ring 7 could just as easily have the same number of teeth. In this embodiment, again with reference to [Fig. 4], the first main drive ring 6 and the second main drive ring 7 have the same diameter D. It is understood that the diameters of the first main drive ring 6 and the second main drive ring 7 could be different.

[0062] Alternatively, the first main drive ring 6 and the second main drive ring 7 have the same number of teeth. In this embodiment, the diameter D of the first main drive ring 6 and the second main drive ring 7 are different to obtain a different reduction ratio between the two rings 6,7.

[0063] In a first embodiment, with reference to [Fig.4], the first main drive ring 6 is positioned axially between the electric machine 3 and the second main drive ring 7.

[0064] In a second embodiment, with reference to [Fig.6], the electric machine 3 is positioned axially between the first main drive ring 6 and the second main drive ring 7.

[0065] According to the invention, with reference to [Fig. 4], the electric machine 3 comprises a plurality of elementary electric machines 31 positioned circumferentially around the first electric machine shaft 4 at the same radial distance to allow for distributed drive with a reduced footprint. Preferably, the plurality of elementary electric machines 31 are evenly distributed around the first electric machine shaft 4.

[0066] In a known manner, an electrical machine comprises a rotor that rotates about its axis of rotation and a stator, fixed around the rotor, which makes it possible to create a magnetic field genetics to rotate the rotor. Each elementary electrical machine 31 thus comprises an elementary rotor 32 which rotates around its own axis of rotation A, parallel to the longitudinal axis X and an elementary stator 33.

[0067] In a preferred embodiment, again with reference to Figure 4, each elementary electric machine 31 includes an auxiliary drive ring 34, configured to rotate about the axis of rotation A of the elementary rotor 32. Each auxiliary drive ring 34 includes a plurality of teeth to cooperate with the teeth of the main drive rings 6, 7 as will be shown later.

[0068] According to the invention, the plurality of elementary electrical machines 31 defines a first set of elementary electrical machines 31A and a second set of elementary electrical machines 31B. For the sake of brevity, the expressions "first set of electrical machines" and "second set of electrical machines" are understood to mean "each elementary electrical machine of the first set of elementary electrical machines" and "each elementary electrical machine of the second set of elementary electrical machines." Two sets of electrical machines 31A and 31B are described in this document; however, it is understood that the plurality of elementary electrical machines 31 could just as easily define a different number of sets, in particular more than two sets of elementary electrical machines 31.

[0069] According to the invention, with reference to Figures 4 and 5, the first set of electrical machines 31A is mechanically connected at least to the first electrical machine shaft 4 and the second set of electrical machines 31B is mechanically connected at least to the second electrical machine shaft 5. In particular, in this example shown in [Fig. 4] and [Fig. 5], the first set of electrical machines 31A is mechanically connected only to the first electrical machine shaft 4 and the second set of electrical machines 31B is mechanically connected only to the second electrical machine shaft 5. It is understood that the first set of electrical machines 31A or the second set of electrical machines 31B could be connected to both the first electrical machine shaft 4 and the second electrical machine shaft 5.Similarly, it is self-evident that the first set of electrical machines 31A and the second set of electrical machines 31B could also be connected to both the first electrical machine shaft 4 and the second electrical machine shaft 5.

[0070] As shown in [Fig. 4], each auxiliary drive ring 34 of the first set of electrical machines 31A cooperates with the first main drive ring 6 mounted on the first electrical machine shaft 4, and each auxiliary drive ring 34 of the second set of machines The electrical components 31B cooperate with the second main drive ring 7 mounted on the second electrical machine shaft 5. Thus, when the first electrical machine shaft 4 rotates about its own axis W, the set of auxiliary drive rings 34 of the first set of electrical machines 31A is driven in rotation according to the first rotational speed vA of the first electrical machine shaft 4. Similarly, when the second electrical machine shaft 5 rotates about its own axis W, the set of auxiliary drive rings 34 of the second set of electrical machines 31B is driven in rotation according to the second rotational speed vB of the second electrical machine shaft 5.Conversely, when the auxiliary drive rings 34 of the first set of electrical machines 31A rotate, the first main drive ring 6 is configured to be driven in rotation, in order to drive the first electrical machine shaft 4. Similarly, when the auxiliary drive rings 34 of the second set of electrical machines 31B rotate, the second main drive ring 7 is configured to be driven in rotation, in order to drive the second electrical machine shaft 5. In other words, each set of electrical machines 31A, 31B can be completely dissociated so as to operate independently.

[0071] More specifically, thanks to the invention, it is thus possible to separate the two sets of electrical machines 31 A, 31 B to drive the two electrical machine shafts 4, 5 independently and thus allow, for example, the power supply of two separate pieces of equipment which would each be connected to one of the electrical machine shafts 4, 5. It goes without saying that each elementary electrical machine 31 could include more than one auxiliary drive ring 34, so as to cooperate both with the first main drive ring 6 and with the second main drive ring 7.

[0072] In this example, with reference to the schematic [Fig. 7], the electric machine 3 comprises a first stator SA formed by the set of elementary stators 33 of the first set of electric machines 31A and a second stator SB formed by the set of elementary stators 33 of the second set of electric machines 31B. The first stator SA and the second stator SB have the same axial position and are advantageously nested one inside the other so as to reduce the overall size of the electric machine 3. As illustrated in [Fig. 7], the first stator and the second stator are advantageously connected respectively to a first power device DPA and a second power device DPB in order to independently control the flow of electric current in each stator and, consequently, the rotational speed vA, vB of the elementary rotors. 32 of each set of electrical machines 31 A, 31B. Preferably, the power devices DPA and DPB are connected to the same set of batteries and the use of two stators SA, SB allows the same set of batteries to be powered from two different speeds.

[0073] In a first embodiment, with reference to [Fig.4], the first main drive ring 6 being positioned axially between the electric machine 3 and the second main drive ring 7, the auxiliary drive rings 34 of the first set of electric machines 31A extend axially between the electric machine 3 and the auxiliary drive rings 34 of the second set of electric machines 31B.

[0074] In a second embodiment, with reference to [Fig. 6], the electric machine 3 being positioned axially between the first main drive ring 6 and the second main drive ring 7, it also extends between the auxiliary drive rings 34 of the first set of electric machines 31A and the auxiliary drive rings 34 of the second set of electric machines 31B. In other words, the auxiliary drive rings 34 of the first set of electric machines 31A extend upstream of the electric machine 3 and the auxiliary drive rings 34 of the second set of electric machines 31B extend downstream of the electric machine 3, so as to extend axially on either side of the electric machine 3 to cooperate respectively with the first main drive ring 6 and with the second main drive ring 7.

[0075] Preferably, the elementary rotor 32 of each elementary electric machine 31 is configured to rotate at a rotational speed. In particular, the first set of electric machines 31A is configured to rotate at a first rotational speed vA and the second set of electric machines 31B to rotate at a second rotational speed vB. In one embodiment, the first rotational speed vA is different from the second rotational speed vB, allowing the first electric machine shaft 4 and the second electric machine shaft 5 to be driven at two different rotational speeds. Such a configuration advantageously allows two separate energy sources to be supplied simultaneously, for example, to two different pieces of equipment with different requirements.

[0076] In order to obtain two different rotational speeds vA, vB, in a first embodiment, the reduction ratio between the first main drive ring 6 and the auxiliary drive ring 34 of the first set of electrical machines 31A and the reduction ratio between the second main drive ring 7 and the auxiliary drive ring 34 of the second The 31B electrical machine assemblies differ due to the different number of teeth between the first main drive ring 6 and the second main drive ring 7. In this case, the diameters D of the first main drive ring 6 and the second main drive ring 7 may be similar or different. In a second embodiment, different reduction ratios are obtained by using different diameters of the first main drive ring 6 and the second main drive ring 7 with a similar number of teeth, as described above.

[0077] Alternatively, the main drive rings 6, 7 could comprise the same number of teeth and the auxiliary drive rings 34 could comprise a different number of teeth between the first set of electrical machines 31A and the second set of electrical machines 31B to allow each to rotate at different rotational speeds vA, vB.

[0078] In a third embodiment, the auxiliary drive rings 34 of the first set of electrical machines 31A and the auxiliary drive rings 34 of the second set of electrical machines 31B could have different diameters G (shown in [Fig.6]) so as to allow different reduction ratios between the two sets of electrical machines 31A, 31B.

[0079] As described above, each elementary electrical machine 31 is configured to operate in either a "motor" or a "generator" mode, depending on the requirements. Preferably, the first set of electrical machines 31A operates in the same first mode (motor or generator), and the second set of electrical machines 31B operates in the same second mode (motor or generator), thus providing two separate sets of electrical machines 31A and 31B, capable of operating independently of each other. Thanks to the invention, several configurations are then possible: • the first set of electrical machines 31A and the second set of electrical machines 31B operate in motor mode, so as to generate enough power to contribute to the drive of the propulsion unit 9; • the first set of electrical machines 31A and the second set of electrical machines 31B operate in generator mode, so as to supply one or more separate pieces of equipment with energy, for example; • The first set of electrical machines 31A operates in motor mode and the second set of electrical machines 31B operates in generator mode, so as to both supply energy to the turbine bomachine 2 and to power equipment, for example to recharge a battery, these two actions being able to be carried out simultaneously thanks to the invention.

[0080] A method of operating the propulsion assembly according to a first embodiment of the invention will now be described, with reference to [Fig.8].

[0081] According to the invention, the method comprises a first step of rotating the first electrical machine shaft 4 at a first rotational speed vA. The first electrical machine shaft 4 then drives the first set of electrical machines 31A via the first main drive ring 6, thereby supplying the first set of electrical machines 31A with energy.

[0082] Simultaneously, the method includes a second step E2 of rotating the second electrical machine shaft 5 at a second rotational speed vB. The second electrical machine shaft 5 then drives the second set of electrical machines 31B via the second main drive ring 7, thereby supplying the second set of electrical machines 31B with energy. The first set of electrical machines 31A and the second set of electrical machines 31B are thus powered independently.

[0083] The first rotational speed vA and the second rotational speed vB are identical, so as to supply each set of electrical machines 31 A, 31B with a similar amount of energy to power, for example, two pieces of equipment with similar requirements, or different, so as to supply each set of electrical machines 31 A, 31B with a different amount of energy to power, for example, two pieces of equipment with different requirements. The power supply to the two pieces of equipment is thus achieved simultaneously for both sets of electrical machines 31 A, 31B, which is efficient.

[0084] According to a second embodiment, the method may include a first step of activating the first set of electrical machines 31A by rotating the auxiliary drive ring 34 of each elementary electrical machine 31 of the first set of electrical machines 31A, at a first rotational speed vA. The first main drive ring 6 is then rotated, in turn driving the first electrical machine shaft 4. Simultaneously, in a second step, the second set of electrical machines 31B may be activated, causing the auxiliary drive ring 34 of each elementary electrical machine 31 of the second set of electrical machines 31B to rotate at a second rotational speed vB. The second main drive ring 7 is then rotated, in turn driving the second electrical machine shaft 5.

Claims

1. Claims Propulsion assembly (1) for propelling an aircraft, the propulsion assembly (1) comprising: • a gas turbomachine (2) comprising at least a first rotating turbomachine shaft (21) and a second rotating turbomachine shaft (22), • an electric machine (3) comprising a plurality of elementary electric machines (31), the plurality of elementary electric machines (31) being positioned circumferentially around a first electric machine shaft (4) and a second electric machine shaft (5) at the same radial distance, the first electric machine shaft (4) and the second electric machine shaft (5) extending along the same longitudinal axis (W), the first electric machine shaft (4) being mechanically connected to the first turbomachine shaft (21), the second electric machine shaft (5) being mechanically connected to the second turbomachine shaft (22), each elementary electric machine (31) of the plurality of elementary electric machines (31) comprising an auxiliary drive ring (34) configured to rotate along an axis of rotation (A) parallel to the longitudinal axis (X),the plurality of elementary electrical machines (31) defining at least a first set of elementary electrical machines (31 A) and a second set of elementary electrical machines (31B), the electrical machine (3) circumferentially comprising an alternation of elementary electrical machines (31) belonging to the first set of elementary electrical machines (31 A) and of elementary electrical machines (31) belonging to the second set of elementary electrical machines (31B), • a first main drive ring (6) mounted securely on the first electric machine shaft (4) and coaxial with the first electric machine shaft (4) and a second main drive ring (7) mounted securely on the second electric machine shaft (5) and coaxial with the second electric machine shaft (5), • propulsion unit (1) characterized in that the first set of elementary electrical machines (31 A) is mechanically connected at least to the first electric machine shaft (4) and the second set of elementary electrical machines (31B) is mechanically connected at least to the second electric machine shaft (5), the auxiliary drive ring gear (34) of each elementary electric machine (31) of the first set of elementary electrical machines (31 A) cooperates at least with the first main drive ring gear (6) mounted on the first electric machine shaft (4), and the auxiliary drive ring gear (34) of each elementary electric machine (31) of the second set of elementary electrical machines (31B) cooperates at least with the second main drive ring gear (7) mounted on the second electric machine shaft (5),the first set of elementary electrical machines (31 A) and the second set of elementary electrical machines (31B) being configured to be dissociated from one another, so as to each operate independently.

2. Propulsion assembly (1) according to claim 1, wherein the first main drive ring (6) is positioned axially between the electric machine (3) and the second main drive ring (7).

3. Propulsion assembly (1) according to claim 1, wherein the electric machine (3) is positioned axially between the first main drive ring (6) and the second main drive ring (7).

4. Propulsion assembly (1) according to one of claims 1 to 3, in which the elementary electrical machines (31) of the first set of elementary electrical machines (31 A) and of the second set of elementary electrical machines (31B) are distributed circumferentially in a homogeneous manner around the longitudinal axis (W).

5. Propulsion assembly (1) according to one of claims 1 to 4, in which, each elementary electrical machine (31) comprising an elementary stator (33), the electrical machine (3) comprising a first stator (SA) formed by the plurality of elementary stators (33) of the first set of elementary electrical machines (31 A) and a second stator (SB) formed by the plurality of elementary stators (33) of the second set of elementary electrical machines (31B), the first stator (SA) and the second stator (SB) are respectively connected to a first power device (DPA) and to a second power device (DPB).

6. Propulsion assembly (1) according to one of claims 1 to 5, in which each elementary electrical machine (31) of the first set of elementary electrical machines (31 A) being configured to rotate according to a first rotation speed (vA), each elementary electrical machine (31) of the second set of elementary electrical machines (31B) is configured to rotate according to a second rotation speed (vB) different from the first rotation speed (vA).

7. Propulsion assembly (1) according to one of claims 1 to 6, in which each elementary electrical machine (31) is configured to operate in a mode called "motor" and in a mode called "generator", all the elementary electrical machines (31) of the first set of elementary electrical machines (31 A) being configured to operate in the same first mode (motor or generator), all the elementary electrical machines (31) of the second set of elementary electrical machines (31B) are configured to operate in the same second mode (motor or generator) different from the first mode.

8. Aircraft comprising at least one propulsion unit (1) according to one of claims 1 to 7.

9. Method of operating a propulsion unit (1) according to one of claims 1 to 7, the method comprising: • a step of rotating the first electric machine shaft (4) driving the first set of elementary electric machines (31 A), and • a step of rotating the second electric machine shaft (5) driving the second set of elementary electric machines (31B), the second electric machine shaft (5) rotating independently of the first electric machine shaft (4).

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