Energy storage device, propulsion system and associated aircraft

Abstract

The energy storage device comprises a rotary transformer (10), the rotary transformer having a fixed part forming a stator (11) with stator coils (13) connected in series and a rotating part forming a rotor (12) with a cryogenic enclosure (24), and superconducting rotor coils (25) connected in series and arranged within the cryogenic enclosure (24), the rotor and stator being coaxial and separated by an air gap such that a magnetic field generated by the stator coils (13) induces a current in the rotor coils (25) during rotor rotation. The cryogenic enclosure (24) further comprises an electrical energy storage circuit (26) connected to the rotor coils (25). Figure for the abbreviation: Fig 2

Description

Title of the invention: Energy storage device, associated propulsion system and aircraft Technical field

[0001] The invention relates to energy storage devices and, more particularly, to energy storage devices comprising a rotary transformer.

[0002] The invention further relates to an aircraft propulsion system comprising such a device and an aircraft comprising such a system. Previous techniques

[0003] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and those currently in circulation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0004] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0006] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0007] Conventionally, an aircraft may include a propeller to propel the aircraft.

[0008] The propeller is driven by a rotor generally coupled to a turbomachine or an electric machine.

[0009] The aircraft may be a helicopter comprising a propulsion propeller.

[0010] Alternatively, the aircraft may be an airplane powered by at least one turboprop comprising a propeller driven by a turbomachine or by a propeller driven by an electric machine.

[0011] The propeller equipping such a turboprop, as well as the rotor of the helicopter comprising said propeller, are generally equipped with a de-icing system for removing the ice accumulating on the propeller blades. Most current de-icing systems are electrical systems comprising, for example, electrical heating mats fixed to the lower and upper surfaces of each blade, at the leading edge. When powered, these systems create heat for removing the ice formed on the blade, which will then be ejected by centrifugation. This power supply of the heating mats requires a power of several kilowatts delivered by a three-phase electrical network of the aircraft.

[0012] To do this, it is necessary to supply electrical energy to the mats fixed on the blades, via equipment making it possible to transfer this electrical energy from a fixed part in a reference frame linked to the aircraft, to a rotating part in said reference frame, the rotating part comprising the propeller.

[0013] Documents WO 2021 / 099743 and WO 2019 / 215399 disclose a three-phase rotating transformer for transferring electrical power between the fixed part and the rotating part without contact.

[0014] However, the use of a three-phase rotating transformer generates significant Joule losses and iron losses.

[0015] Furthermore, the power factor is less than or equal to 0.5.

[0016] The low efficiency of the defrosting system requires that the three-phase transformer be configured to transfer significant electrical power, increasing the size and mass of said transformer. Statement of the invention

[0017] The aim of the invention is to overcome all or part of these drawbacks.

[0018] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the invention relates to an energy storage device comprising a rotary transformer.

[0019] The rotary transformer comprises a fixed part forming a stator comprising stator coils connected in series, and a moving part forming a rotor.

[0020] The mobile part comprises:

[0021] - two hollow concentric shafts forming a supply duct and a delivery duct repression,

[0022] - a plurality of compartments,

[0023] - a plurality of intake channels connecting the compartments to the duct inlet and a plurality of discharge channels connecting the compartments to the discharge duct,

[0024] the two hollow concentric shafts, the intake and discharge channels and the compartments forming a cryogenic enclosure.

[0025] The moving part further comprises superconducting rotor coils connected in series, each rotor coil being inserted into a compartment so that a cryogenic fluid flowing in the inlet duct cools each rotor coil and the heated cryogenic fluid is discharged into the discharge duct via the inlet and discharge channels.

[0026] The rotor and stator are coaxial and separated by an air gap so that a magnetic field generated by the stator coils induces a current in the rotor coils as the rotor rotates.

[0027] The cryogenic enclosure further comprises an electrical energy storage circuit connected to the rotor coils.

[0028] The term cryogenic refers to temperatures close to 0 Kelvin, for example 4 Kelvin so that the electrical elements arranged in the cryogenic enclosure have zero electrical resistance.

[0029] The installation of superconducting rotor coils and the electrical energy storage circuit in the cryogenic enclosure makes it possible to store electrical energy in the moving part without losses.

[0030] As the losses are zero, the size of the magnetic cores supporting the stator coils and the rotor coils can be reduced compared to a rotary transformer known from the state of the art, thus reducing the mass of the storage device so that the mass of an aircraft comprising said device is lightened, allowing less energy to be consumed during the different phases of flight.

[0031] Preferably, the electrical energy storage circuit comprises a superconducting storage coil and two superconducting switches, the superconducting switches being configured to store a current in the superconducting storage coil from the induced current.

[0032] Advantageously, the energy storage device further comprises an additional electrical storage means for storing electrical energy delivered by the superconducting storage coil.

[0033] Preferably, a first end of a first superconducting switch and a first end of the superconducting storage coil are connected to a first end of the rotor coil assembly, a first end of the second superconducting switch is connected to the second end of the rotor coil assembly, and the second end of the second superconducting switch is connected to the second end of the first superconducting switch and the second end of the superconducting storage coil.

[0034] Advantageously, the cryogenic enclosure further comprises two holding tori, a first end of each compartment being connected to a first torus and a second end of each compartment being connected to the second torus, the compartments being regularly arranged around the perimeter of the first and second tori.

[0035] Preferably, the fixed part further comprises a cryogenic fluid supply circuit comprising a cryogenic fluid reservoir and a cryogenic pump, the cryogenic pump supplying the supply conduit from the cryogenic fluid stored in the cryogenic fluid reservoir and the delivery conduit delivering the cryogenic fluid delivered by the cryogenic pump into the cryogenic fluid reservoir.

[0036] There is also provided an aircraft propulsion system comprising a main rotor, electrical equipment, and an energy storage device as defined previously, the main rotor being formed by the hollow concentric shafts, the electrical energy storage device powering the electrical equipment.

[0037] Preferably, the propulsion system further comprises blades driven by the main rotor, the electrical equipment comprising heating mats arranged on the blades, the heating mats being powered by the electrical energy storage device to de-ice the blades.

[0038] Advantageously, the propulsion system further comprises a turbomachine or an electric motor driving the main rotor.

[0039] An aircraft comprising a propulsion system as defined above is also proposed. Brief description of the drawings

[0040] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0041] - figure [Fig.l] schematically illustrates an aircraft according to the invention,

[0042] - figure [Fig.2] schematically illustrates a section of the storage device energy according to the invention,

[0043] - figure [Fig.3] schematically illustrates an example of the production of the coils stator according to the invention

[0044] - figure [Fig.4] schematically illustrates an example of the construction of an enclosure cryogenic according to the invention,

[0045] - figure [Fig.5] illustrates an electrical diagram of an exemplary embodiment of a storage circuit according to the invention, and

[0046] - figure [Fig.6] illustrates an example of the temporal evolution of currents circulating in the storage circuit according to the invention. Detailed description

[0047] Reference is made to [Fig.l] which schematically illustrates an aircraft 1 comprising a propulsion system 2.

[0048] The aircraft 1 as shown is a helicopter.

[0049] The propulsion system 2 comprises a main rotor 3, an energy storage device 4, electrical equipment arranged in the main rotor 3, and drive means 5 of the main rotor 3.

[0050] The propulsion system 2 further comprises blades 6 driven by a rotor shaft of said main rotor 3.

[0051] The electrical equipment comprises, for example, electric heating mats 7 fixed to the intrados and the extrados of each blade 6 powered by the energy storage device 4 to defrost the blades 6.

[0052] The electric heating mats 7 powered by the energy storage device 5 create heat enabling the ice formed on the blades 6 to be removed.

[0053] The detached ice is then ejected by centrifugation during the rotation of the main rotor 3 driving the blades 6.

[0054] The electrical equipment may comprise a device for orienting the blades 6 comprising, for example, an electric motor.

[0055] The drive means comprise for example a turbomachine 8 driving the main rotor 3 in rotation by means of a reduction gear 9.

[0056] As a variant, the turbomachine 8 is replaced by a hybrid propulsion means comprising a turbomachine and an electric motor powered by an electrical network of the helicopter, the main rotor 3 being driven by the turbomachine and / or the electric motor.

[0057] According to another embodiment, the aircraft 1 comprises an airplane comprising at least one turboprop. The blades of the propeller of the turboprop are connected to a rotor of the turboprop. Electric heating mats are fixed on the lower and upper surfaces of each blade and are powered by the energy storage device 4 located in the rotor of the turboprop to de-ice the blades of the propeller of the turboprop.

[0058] According to yet another embodiment, the aircraft comprises a propeller connected to an electric motor powered by an electrical network of the aircraft, heating mats electric heaters being fixed on the lower and upper surfaces of each blade. The electric heating mats are powered by the energy storage device located in the rotor to de-ice the propeller blades.

[0059] [Fig.2] schematically illustrates a section of the energy storage device 5 along a longitudinal direction of the rotor 4.

[0060] The energy storage device 5 comprises a rotary transformer 10 comprising a fixed part forming a stator 11 and a mobile part 12 forming a rotor secured to the main rotor 3.

[0061] The fixed part of the transformer 10 is fixed relative to the main rotor 3.

[0062] The fixed part of the transformer 10 comprises stator coils 13 connected in series.

[0063] [Fig. 3] schematically illustrates an example of the embodiment of the stator coils 13.

[0064] Each stator coil 13 is wound around an open annular magnetic core 14 made of laminated soft iron having two ends.

[0065] A first end of each core 14 is fixed on a first toric fixing blade 15, and a second end of each core 14 is fixed on a second toric fixing blade 16 parallel to the first blade 15 so that the stator coils 13 are regularly arranged on the perimeter of the blades 15, 16.

[0066] The first and second fixing blades 15, 16 are for example made of carbon fiber and are spaced apart by a distance Ds.

[0067] Referring now again to [Fig.2].

[0068] The set of stator coils 13 connected in series is powered by a power converter 17 connected to an electrical power supply network 18 of the aircraft 1 (the electrical connections between the set of stator coils 13 and the power converter 17 are not shown).

[0069] The power converter 17 provides a low-intensity alternating current, for example 10 A, and comprises, for example, a single-arm inverter.

[0070] The moving part of the transformer 10 comprises two hollow concentric shafts 19, 20 which form a supply duct and a discharge duct.

[0071] A first shaft 19 is inserted into the second shaft 20.

[0072] The central duct of the first shaft 19 forms, for example, the supply duct, and the annular duct formed between the first and second shafts 19, 20 forms the discharge duct.

[0073] The hollow concentric shafts 19, 20 form the rotor shaft of the main rotor 3.

[0074] The rotor of the transformer 10 further comprises compartments 21, intake channels 22, and discharge channels 23.

[0075] Each compartment 21 is connected to a first end of the second shaft 20 by an intake channel 22 such that said compartment 21 is connected to the intake duct, and is connected to the first end of the second shaft 20 by a discharge channel 23 such that said compartment 21 is connected to the discharge duct.

[0076] The two hollow concentric shafts 19, 20, the intake channels 22, the discharge channels 23 and the compartments 21 forming a cryogenic enclosure 24 filled with a cryogenic fluid.

[0077] The rotor of the transformer 10 further comprises a set of superconducting rotor coils 25 connected in series and an electrical energy storage circuit 26 connected to the rotor coils 25 (the electrical connections between the storage circuit 26 and the rotor coils 25 are not shown).

[0078] Each compartment 21 houses a superconducting rotor coil 25.

[0079] The second end of each shaft 19, 20 is connected to a cryogenic fluid supply circuit 27.

[0080] The first and second tubes 19, 20 are connected to each other at their first end by means of a first cryogenic bearing 28.

[0081] Each rotor coil 25 is supplied with cryogenic fluid by the inlet channel 22 of the compartment 21 housing said rotor coil 25, said inlet channel 22 being connected to the supply duct, and the cryogenic fluid heated by said rotor coil 25 is discharged by the discharge channel 23 of the compartment 21 housing said rotor coil 25, said discharge channel 23 being connected to the discharge duct.

[0082] The direction of circulation of the cryogenic fluid is represented by arrows.

[0083] The electrical connections connecting the storage circuit 26 and the rotor coils 25 pass through the intake channels 22 and the discharge channels 23.

[0084] The supply circuit 27 comprises a casing 30, a reservoir 31 of cryogenic fluid, and a cryogenic pump 32.

[0085] The reservoir 31 is for example spherical allowing a uniform distribution of the pressure exerted by the cryogenic fluid on the reservoir.

[0086] The supply circuit 27 may further comprise a thermostatic control unit 33 regulating the temperature of the cryogenic fluid so that said temperature remains, for example, equal to 4 Kelvin or -269.15 degrees Celsius.

[0087] The cryogenic pump 32 is arranged in the casing 30 and comprises a suction duct 34 connected to the reservoir 31 and a discharge duct 35 opening into the central duct of the first shaft 19 to supply the supply duct with the cryogenic fluid stored in the reservoir 31.

[0088] The first tube 19 is connected to the discharge conduit 35 of the cryogenic pump 32 via a second cryogenic bearing 36.

[0089] The second shaft 20 is connected to the casing 30 via a third cryogenic bearing 37.

[0090] The delivery duct formed by the shafts 19, 20 is connected to the reservoir 31 via an annular duct formed between the casing 30 and the pump 32.

[0091] In order to drive the main rotor 4, the second shaft 20 comprises for example on its outer surface a toothed wheel 38 cooperating with a toothed wheel 39 of the reducer 9.

[0092] The cryogenic bearings 28, 36, 37, and the cryogenic pump 32 are sized to operate and withstand the temperature of the cryogenic fluid.

[0093] The hollow concentric shafts 19, 20, the intake channels 22, the discharge channels 23, and the supply circuit 27 comprise a thermal insulator (not shown) limiting the heating of the cryogenic fluid by the medium surrounding the stator 11 and the main rotor 3.

[0094] Each rotor coil 25 wound around the magnetic core 14 connected to the compartment 21 is made of a superconducting material, for example Niobium Tin, Nb3Sn, or Niobium Titanium, NbTi.

[0095] The rotor 12 and the stator 11 of the transformer 10 are coaxial and separated by an air gap so that a magnetic field generated by the stator coils 13 induces a current in the rotor coils 25 during rotation of the rotor 12.

[0096] The rotor coil assembly 25 is inserted between the stator coils 13 in the space separating the toric fixing blades 15, 16.

[0097] The storage circuit 26 comprises a superconducting storage coil 40, and two superconducting switches or cryotrons 41, 42, and is detailed below.

[0098] The storage coil 40 is made of a superconducting material, for example Niobium Tin, Nb3Sn, or Niobium Titanium, NbTi.

[0099] Each superconducting or cryotron switch 41, 42 conventionally comprises two wires made of different superconducting materials, insulated and wound together, each having a different critical temperature.

[0100] A first wire is for example made of tantalum and the second wire is made of niobium.

[0101] The temperature of the cryogenic fluid is chosen so that it is lower than the lowest critical temperature of the superconducting materials of the rotor coils 25, the storage coil 40, and the superconducting switches 41, 42 so that their electrical resistance is zero.

[0102] When one of the wires of the switches 41, 42 generates a magnetic field greater than a critical magnetic field, the switch is open so that it does not allow a current to pass. Otherwise, the switches 41, 42 immersed in the cryogenic fluid are conductive and have zero electrical resistance.

[0103] The temperature of the cryogenic fluid is for example equal to 4 Kelvin or -269.15 degrees Celsius.

[0104] The cryogenic fluid is for example liquid nitrogen, liquid helium, or liquid hydrogen.

[0105] The energy storage device 26 may further comprise an additional electrical storage means 43 located in the mobile part of the transformer 10 and arranged outside the enclosure 24 to store electrical energy delivered by the superconducting storage coil 40 and for example use the energy stored in the means 43 when the main rotor 3 is not rotating.

[0106] The additional electrical storage means 43 comprises, for example, a battery or a supercapacitor.

[0107] Alternatively, the additional electrical storage means 43 is arranged in the fixed part 3 of the transformer 10 and is electrically connected to the storage circuit 26 via a ring-brush collector device known from the state of the art.

[0108] An energy management circuit 44 located in the mobile part of the transformer 10 and arranged outside the enclosure 24 connects the storage coil 40 to the electrical storage means 26.

[0109] The energy management circuit 44 controls the switches 41, 42, and supplies the electric heating mats 7 from the electrical energy stored in the storage coil 40 and, where appropriate, in the additional electrical storage means 43.

[0110] [Fig.4] schematically illustrates an example of embodiment of the enclosure 17.

[0111] Each compartment 21, for example cylindrical, houses a rotor coil 25.

[0112] The enclosure 24 further comprises two holding toroids 45, 46.

[0113] A first end of each compartment 21 is connected to a first torus 45 and a second end of each compartment 21 is connected to the second torus 46, the compartments 21 being regularly arranged on the perimeter of the tori 45, 46.

[0114] [Fig.5] illustrates an electrical diagram of an exemplary embodiment of the storage circuit 26 arranged inside the cryogenic enclosure 24.

[0115] The set of stator coils 13 connected in series of the rotating transformer 10 is represented by a primary coil 47 and the set of rotor coils 25 connected in series of the rotating transformer 10 is represented by a secondary coil 48.

[0116] The mutual inductance between the primary coil 47 and the secondary coil 48 is denoted M.

[0117] A primary current denoted ii circulates in the primary coil 47, and a secondary current denoted i2 circulates in the secondary coil 48.

[0118] A current denoted i3 flows in the storage coil 40.

[0119] The ends 49, 50 of the primary coil 47 are connected to the power converter 17.

[0120] A first end of a first superconducting switch 41 and a first end of the storage coil 40 are connected to a first end of the secondary coil 48.

[0121] A first end of the second superconducting switch 42 is connected to the second end of the secondary coil 48, and the second end of the second superconducting switch 42 is connected to the second end of the first superconducting switch 41 and to the second end of the storage coil 40.

[0122] The first storage coil end 40 is connected to a first connection 51, and the second storage coil end 40 is connected to a second connection 52.

[0123] The first and second connections 51, 52 of the storage coil 40 are connected to the energy management circuit 44.

[0124] An example of implementation of the energy storage device 4 is now detailed.

[0125] The energy storage device 4 operates according to the principle of a “flux pump” making it possible to store in the storage coil 40 large currents from low currents delivered by the power converter 17 without Joule losses. For example, from a current of 10 A delivered by the power converter 17, the storage coil 40 can store a current of the order of 100 to 160 A after several iterations of the “flux pump”. As superconducting elements can store currents of the order of 1600 A without Joule losses, the storage coil 40 made of a superconducting material stores a current of the order of 100 to 160 A without Joule losses.

[0126] [Fig.6] illustrates an example of the temporal evolution of the primary current ib, the secondary current i2, and the current i3 circulating in the storage coil 40.

[0127] It is assumed that the primary currents ii and secondary currents i2, and that the current i3 are null.

[0128] It is further assumed that at a time t0 the switches 41, 42 are open so that that they do not let any current pass.

[0129] Between time t0 and time tb the switches 41, 42 are open. The power converter 17 delivers a current so that the primary current ii increases from zero to a positive current value II. The variation of the primary current induces a voltage across the terminals of the secondary coil 48.

[0130] At time ti When the primary current ii has reached the current value II and the voltage induced across the terminals of the secondary coil is zero 48, the second switch 42 is closed so that a current flows through said switch.

[0131] Between the instant ti and an instant t2, the primary current h decreases from the current value Il to the current value -II. The variation of the primary current h induces the secondary current i2 equal to a positive current value 122, the current value 122 being equal to twice the current value II multiplied by the mutual inductance M.

[0132] At time t2, the primary current ii is equal to the current value -II. The voltage across the terminals of the first switch 41 becomes zero. When the voltage across the terminals of the first switch 41 is zero, the first switch 41 is closed, allowing the secondary current i2 equal to the current value 122 to be stored in the circuit formed by the secondary coil 48 (the set of rotor coils 25 connected in series), and the storage circuit 26 comprising the switches 41, 42, and the storage coil 40.

[0133] Between time t2 and time t3, the primary current ii varies from the value -II to a negative current value -111 greater than the negative current value -II allowing the current in the second switch 42 to be cancelled. When said current is zero, the second switch 42 is open.

[0134] A current of value 121 is stored in the storage coil 40 so that the current i3 is equal to 121.

[0135] From time to to time t3, a first cycle T1 of charging the storage coil 40 has been carried out.

[0136] Generally the current i3 stored in the storage coil 40 is insufficient to power the electrical equipment, several charging cycles of the storage coil 40 are repeated successively.

[0137] A second charging cycle T2 is now described following the first charging cycle TL.

[0138] At time t3, the first switch 41 is closed and the second switch 42 is open.

[0139] Between time t3 and time t4, the primary current ii varies from the negative current value -II 1 to the negative current value II inducing a voltage across the terminals of the secondary coil 48.

[0140] At time t4, the primary current ii is equal to the negative current value II. The voltage across the secondary coil 48 becomes zero. When the voltage across the secondary coil 48 is zero, the second switch 42 is closed.

[0141] Between the instant t4 and an instant t5, the primary current ii decreases from the current value Il to the positive current value II 1 less than the negative current value II so that the current in the secondary coil 48 and in the first and second switches 41, 42 is equal to a negative current value 121. The current flowing through the first switch 41 is cancelled out, allowing the first switch 4L to open.

[0142] At time t5, the first switch 41 is open.

[0143] Between time t5 and time t6, the primary current h decreases from the current value 111 to the current value -11 inducing a flux variation equal to M(I1+I11).

[0144] The flux variation induces in the secondary coil 48 the secondary current i2 equal at a current value 122 greater than the current value 121.

[0145] At time t6, when the primary current ii is equal to the current value -II, the voltage across the terminals of the first switch 41 becomes zero. When the voltage across the terminals of the first switch 41 is zero, the first switch 41 is closed.

[0146] Between time t6 and time t7, the primary current ii increases from the current value -Il to a negative current value -112 greater than the current value -Il 1 so that the current flowing in the second switch 42 is zero.

[0147] At time t7, when the current flowing in the second switch 42 is zero, the second switch 42 is open allowing the current i3 equal to the current value 122 to be stored in the storage coil 40, the current value 122 being greater than the current value 121.

[0148] The intensity of the current stored in the storage coil 40 is determined by the number of successive charging cycles and the rotation speed of the main rotor 4.

[0149] By successively carrying out several charging cycles, high intensity currents can be stored in the storage coil 40 from a low intensity current, making it possible in particular to de-ice the blades 6 synchronously.

[0150] Since the temperature of the cryogenic fluid is lower than the critical temperature of the superconducting materials of the rotor coils 25, the storage coil 40, and the switches 41, 42, the currents stored in the storage coil 40 are stored without losses.

[0151] Furthermore, since the losses are zero, the size of the magnetic cores supporting the stator coils 13, the rotor coils 25, and the storage coil 40 can be reduced compared to a rotary transformer known from the state of the art, thus reducing the mass of the rotary transformer 10 and the storage device 4.

[0152] The value of the current stored in the storage coil 40 is determined by the rotation speed of the main rotor 3.

Claims

Claims

1. An energy storage device (4) comprising a rotary transformer (10), the rotary transformer comprising a fixed part forming a stator (11) comprising stator coils (13) connected in series, and a moving part forming a rotor (12) and comprising: - two hollow concentric shafts (19, 20) forming a supply duct and a discharge duct, - a plurality of compartments (21), - a plurality of inlet channels (22) connecting the compartments (21) to the inlet duct and a plurality of discharge channels (23) connecting the compartments to the discharge duct, the two hollow concentric shafts (19, 20), the inlet and discharge channels, and the compartments forming a cryogenic enclosure (24), the moving part further comprising superconducting rotor coils (25) connected in series,each rotor coil being inserted into a compartment so that a cryogenic fluid flowing in the intake duct cools each rotor coil and the heated cryogenic fluid is discharged into the discharge duct via the intake and discharge channels, the rotor and the stator being coaxial and separated by an air gap so that a magnetic field generated by the stator coils (13) induces a current in the rotor coils (25) during rotation of the rotor, characterized in that the cryogenic enclosure (24) further comprises an electrical energy storage circuit (26) connected to the rotor coils (25).,

2. The device of claim 1, wherein the electrical energy storage circuit (26) comprises a superconducting storage coil (40) and two superconducting switches (41, 42), the superconducting switches being configured to store a current in the superconducting storage coil from the induced current.

3. A device according to claim 2, further comprising an ancillary electrical storage means (43) for storing electrical energy delivered by the superconducting storage coil (40).

4. A device according to one of claims 2 and 3, wherein a first end of a first superconducting switch (41) and a first end of the superconducting storage coil (40) are connected to a first end of the set (48) of ro- coils toroidal coils (25), a first end of the second superconducting switch (42) is connected to the second end of the set (48) of rotor coils (25), and the second end of the second superconducting switch (42) is connected to the second end of the first superconducting switch (41) and to the second end of the superconducting storage coil (40).

5. Device according to any one of claims 1 to 4, in which the cryogenic enclosure (24) further comprises two holding tori (45, 46), a first end of each compartment (21) being connected to a first torus (45) and a second end of each compartment (21) being connected to the second torus (46), the compartments (21) being regularly arranged on the perimeter of the first and second tori.

6. Device according to any one of claims 1 to 5, in which the fixed part further comprises a cryogenic fluid supply circuit (27) comprising a cryogenic fluid reservoir (31) and a cryogenic pump (32), the cryogenic pump (32) supplying the supply conduit from the cryogenic fluid stored in the cryogenic fluid reservoir (31) and the delivery conduit delivering the cryogenic fluid delivered by the cryogenic pump (32) into the cryogenic fluid reservoir (31).

7. Propulsion system (2) for aircraft (1) comprising a main rotor (3), electrical equipment, and an energy storage device (4) according to any one of claims 1 to 6, the main rotor (3) being formed by the hollow concentric shafts (19, 20), the electrical energy storage device (4) powering the electrical equipment.

8. A propulsion system according to claim 7, further comprising blades (6) driven by the main rotor (3), the electrical equipment comprising heating mats (7) arranged on the blades (6), the heating mats (7) being powered by the electrical energy storage device (4) to de-ice the blades (6).

9. Propulsion system according to one of claims 7 or 8, further comprising a turbomachine (8) or an electric motor driving the main rotor (3).

10. Aircraft (1) comprising a propulsion system (2) according to any one of claims 7 to 9.

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