Aircraft turbine engine and method for restarting same in flight

Abstract

Disclosed is an aircraft turbine engine comprising a restarting electric machine (ME2) configured to use an alternating restart current (CA2) delivered by a power supply system (3) to drive a high-pressure shaft (22) to rotate, the power supply system comprising: - an electrical generator (ME1) for generating an alternating supply current (CAI) through extraction of a torque from a low-pressure shaft, - an electrical rectifier (31) connected to the electrical generator (ME1), - an electrical converter (32) connected to the restarting electric machine (ME2), - an electrical switching device (33) configured to prevent current from flowing between the electrical rectifier (31) and the electrical converter (32) in an open state and to permit it in a closed state (Fl), a control device (4) being configured to command the closed state (FI) and to activate a device (D) for modulating the electrical power of the alternating restart current (CA2) during a restart in flight

Description

Aircraft turbomachine and its in-flight restart process

[0001] The present invention relates to the in-flight restart of an aircraft turbomachine.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the factors that impact 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. Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible to reduce the environmental footprint of its activity.

[0004] This ongoing research and development work focuses in particular on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, and aeronautical biofuels. This work also focuses on the development of the use of electrical technologies for propulsion, including electric machines to inject or extract power from the rotating parts of engines.

[0005] In a known manner and with reference to the, a turbomachine 100 of the twin-spool turbojet type comprises, from upstream to downstream in the direction of gas flow, a propulsion member 110, a low-pressure compressor 111, a high-pressure compressor 112, a combustion chamber 113, a high-pressure turbine 114, a low-pressure turbine 115 and an exhaust nozzle 116. The rotation of the low-pressure turbine 115 makes it possible to drive, via a low-pressure shaft 121, the low-pressure compressor 111 and the propulsion member 110. A reduction gear (not shown) can be conventionally integrated to make it possible to reduce the rotational speed transmitted by the low-pressure turbine 115 to the propulsion member 110. The high-pressure turbine 114 makes it possible to drive the high-pressure compressor 112 via a high-pressure shaft 122.

[0006] In the event of an in-flight shutdown of the turbomachine 100, caused for example by environmental disturbances such as the ingestion of birds, the restart of the turbomachine must be able to be carried out completely independently of the aircraft's power sources, in a certified re-ignition range, characterized by a maximum altitude, of the order of 30,000 feet, and a minimum speed, of the order of 230 knots. The restart must make it possible to ensure the following functions: fuel injection into the combustion chamber, power supply to the computers, power supply to the spark plugs, and preferably control of the blade setting in a position facilitating start-up, in particular on turbomachines with a linked turbine.

[0007] A descent phase of the aircraft from its cruising altitude, of the order of 40,000 feet, is thus conventionally carried out, during which the low pressure shaft 121 and the high pressure shaft 122 unscrew until they stabilize in an autorotation regime, known by the English term "windmilling". In the autorotation regime, the low pressure shaft 121 and the high pressure shaft 122 are driven at low speed, solely under the action of the wind.

[0008] In a known manner, the restart of the turbomachine 100 can be assisted by an electric starter ME mounted in the accessory relay box, known by its name “Accessory Gear Box (AGB)”. The electric starter ME is electrically powered by taking power from the other turbomachines of the aircraft, via the aircraft's electrical network, and is configured to inject torque onto the high-pressure shaft 122 in this example, or onto the low-pressure shaft 121. Such a restart is however not functional during an in-flight shutdown of all the turbomachines 100 (“total engine flame out”).

[0009] In practice, restarting can also be prevented by a phenomenon of blocking of the high-pressure shaft 122 known as “corelock”, which may occur in particular during the descent phase of the aircraft. During this phase, the temperature of the casing of the turbomachine 100 decreases more quickly than that of the rotor of the high-pressure compressor 112, which results in a difference in thermal expansion of the materials and can block the rotation of the rotor blades by friction against the casing. To avoid this phenomenon, one solution consists of maintaining the high-pressure shaft 122 at a sufficient rotational speed to force the wear of the abradable material of the casing by the blades of the rotor of the high-pressure compressor 112 and thus ensure their rotation. This also requires a power supply via the aircraft's electrical network, which is not functional during an in-flight shutdown of all the turbomachines 100.

[0010] Furthermore, the autorotation regime of the turbomachine 100 does not allow the lubrication system to be driven, which can cause damage. To remedy this, it is known to use an auxiliary pump powered electrically via the aircraft's electrical network, which has the same drawback as previously and impacts the mass of the turbomachine.

[0011] Application US2021115857A1 discloses a gas turbine engine equipped with an energy storage management system connected to an electric machine coupled to the low-pressure shaft and to an electric machine coupled to the high-pressure shaft to carry out energy transfers during an in-flight restart. This does not ensure the drive of the lubrication system, which is the cause of potential damage.

[0012] The invention thus aims at restarting an aircraft turbomachine in flight, in particular in the event of all the aircraft turbomachines stopping in flight. PRESENTATION OF THE INVENTION

[0013] The invention relates to an aircraft turbomachine comprising a low pressure shaft, a high pressure shaft and an electric restart machine configured, when supplied with a restart alternating current, to rotate the high pressure shaft.

[0014] The invention is remarkable in that the aircraft turbomachine comprises: an electrical power supply system for the restart electrical machine comprising: an electrical generator configured to produce an alternating supply current by drawing a rotary torque from the low-pressure shaft, an electrical rectifier connected to the electrical generator and configured to supply a direct current from the alternating supply current, an electrical converter configured to supply the restart alternating current to the restart electrical machine from the direct current, an electrical switching device configured, in an open state, to prohibit the flow of direct current between the electrical rectifier and the electrical converter, and in a closed state, to allow the flow of direct current between the electrical rectifier and the electrical converter,an electrical power modulation device configured to modulate the restart alternating current from at least one modulation setpoint, and a control device configured, during an in-flight restart of the aircraft turbomachine, to control the closed state of the switching device and emit the modulation setpoint, so that the restart electrical machine rotates the high-pressure shaft.,

[0015] The invention advantageously makes it possible to inject torque onto the high-pressure shaft to facilitate the restart of a turbomachine in flight, from a power draw on the low-pressure shaft. The turbomachine can thus restart autonomously and independently, in particular without drawing power from the aircraft's electrical network or from another turbomachine. The invention is particularly suitable for use during an in-flight shutdown of all turbomachines, where the aircraft's electrical network is unavailable.

[0016] The method according to the invention is thus particularly suitable for a situation of in-flight shutdown of all the aircraft's turbomachines ("total engine flame out"), in that it allows an autonomous and independent restart of the turbomachine, preferably only by taking power from the low pressure shaft.

[0017] Preferably, the modulation setpoint is a function of a measurement of the rotational speed of the high-pressure shaft. Thanks to the electrical power modulation device, it is possible to drive the electric restart machine according to two or more separate speeds. This makes it possible to adapt the power supplied according to the requirements during a restart.

[0018] According to one aspect of the invention, the aircraft turbomachine comprises a lubrication device coupled to the electric restart machine, the electric power modulation device having at least: a low transmission state suitable for driving the lubrication device, a high transmission state suitable for driving the high pressure shaft.

[0019] Advantageously, a low transmission state is commanded during the transient phase where the aircraft is placed in restart conditions, in particular during the autorotation regime of the aircraft turbomachine, known as "windmilling", then a high transmission state is commanded for the restart phase. This makes it possible to continue to ensure the lubrication of the turbomachine during the transient phase and to avoid the occurrence of a phenomenon of blocking of the high pressure shaft in the turbomachine.

[0020] According to one aspect of the invention: the electrical power supply system comprises at least one low electrical resistance and one high electrical resistance connected in parallel between the electrical rectifier and the electrical converter and together forming the electrical power modulation device, and the switching device comprises a first closed state, in which the direct current is modulated by the low electrical resistance, and a second closed state, in which the direct current is modulated by the high electrical resistance.

[0021] Such a binary electrical power modulation device is advantageously not very complex and therefore inexpensive and easy to control.

[0022] According to one aspect of the invention, the electrical power supply system comprises at least one variable resistor mounted between the electrical rectifier and the electrical converter and forming the electrical power modulation device. Such an electrical power modulation device makes it possible to adapt the power transmission according to needs, in a simple and practical manner.

[0023] According to one aspect of the invention, the electrical converter is configured to provide an alternating current of restart frequency controllable by the control device and forms the electrical power modulation device. Such a solution is advantageously space-saving. This facilitates integration into the aircraft turbomachine.

[0024] According to one aspect of the invention, the electric generator is of the wound rotor synchronous type and forms the electrical power modulation device, the control device being configured to control the magnetic excitation of the wound rotor of the electric generator. Such a solution is advantageously compact. This facilitates integration into the aircraft turbomachine.

[0025] According to one aspect of the invention, the control device is configured to control the closed state of the switching device when a measurement of the rotational speed of the low pressure shaft is less than a predetermined threshold.

[0026] The invention also relates to a method for restarting an aircraft turbomachine in flight as described previously, in which the switching device is initially in the open state and, during a restart of the aircraft turbomachine in flight: the control device controls the closed state of the switching device, the control device provides at least one modulation instruction to the electrical power modulation device, then the electrical restart machine drives the high-pressure shaft in rotation from the alternating restart current provided by the electrical power system.

[0027] According to one aspect of the invention, the aircraft turbomachine comprises a lubrication device coupled to the electric restart machine and the control device provides:A first modulation setpoint of a low transmission state of the electric power modulation device adapted for driving the lubrication device, thenA second modulation setpoint of a high transmission state of the electric power modulation device adapted for driving the high pressure shaft,

[0028] The high transmission state is preferably operated when the aircraft is at an altitude of 30,000 feet or less and allows the turbomachine to be restarted. The low transmission state is activated during the preparatory phase of restart, to maintain sufficient lubrication and avoid jamming of the high pressure shaft. PRESENTATION OF FIGURES

[0029] 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.

[0030] This is a schematic representation of an aircraft turbomachine according to the prior art.

[0031] This is a schematic representation of an aircraft turbomachine according to one embodiment of the invention.

[0032] This is a schematic representation of a first embodiment of the invention with an open-state switching device and an electrical power modulation device in the form of a low resistance and a high resistance connected in parallel.

[0033] The is a schematic representation of the first embodiment of the with the switching device in a first closed state.

[0034] The is a schematic representation of the first embodiment of the with the switching device in a second closed state.

[0035] This is a schematic representation of a second embodiment of the invention, in which a variable resistor forms the electrical power modulation device.

[0036] This is a schematic representation of a third embodiment of the invention, in which the electrical converter forms the electrical power modulation device.

[0037] This is a schematic representation of a fourth embodiment of the invention, in which the electric generator forms the electric power modulation device.

[0038] This is a schematic representation of an in-flight restart method according to an embodiment of the invention.

[0039] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0040] With reference to the, the invention relates to a twin-spool aircraft turbomachine T conventionally comprising, from upstream to downstream in the direction of gas flow, a propulsion member 10 (fan or propeller), a low-pressure compressor 11, a high-pressure compressor 12, a combustion chamber 13, a high-pressure turbine 14, a low-pressure turbine 15 and an exhaust nozzle 16. The rotation of the low-pressure turbine 15 makes it possible to drive, via a low-pressure shaft 21, the low-pressure compressor 11 and the propulsion member 10. A reduction gear (not shown) conventionally makes it possible to reduce the rotation speed transmitted by the low-pressure turbine 15 to the propulsion member 10. The high-pressure turbine 14 makes it possible to drive the high-pressure compressor 12 via a high-pressure shaft 22.

[0041] According to the invention and as illustrated in Figures 2 and 3, the aircraft turbomachine T also comprises: an electrical restart machine ME2 coupled to the high-pressure shaft 22 and configured, when supplied by an alternating restart current CA2, to rotate the high-pressure shaft 22, an electrical power supply system 3 of the electrical restart machine ME2 comprising: an electrical generator ME1 coupled to the low-pressure shaft 21 and configured to produce an alternating supply current CA1 by taking a rotary torque from the low-pressure shaft 21, an electrical rectifier 31 electrically connected to the electrical generator ME1 and configured to supply a direct current CC from the alternating supply current CA1,an electrical converter 32 electrically connected to the restart electrical machine ME2 and configured to supply the restart alternating current CA2 to the restart electrical machine ME2 from the direct current CC, an electrical switching device 33 electrically connecting the electrical rectifier 31 and the electrical converter 32 and configured, in an open state O, to prohibit the flow of the direct current CC between the electrical rectifier 31 and the electrical converter 32, and in a closed state F1, F2 (see figures 4 and 5), to authorize the flow of the direct current CC between the electrical rectifier 31 and the electrical converter 32, and an electrical power modulation device D configured to modulate the restart alternating current CA2 from one or more modulation setpoints, and a control device 4 configured, during an in-flight restart of the aircraft turbomachine T,to control the closed state F1, F2 (see figures 4 and 5) of the switching device 33 and emit the modulation instruction(s), so that the electrical restart machine ME2 drives the high pressure shaft 22 in rotation.,

[0042] The invention advantageously makes it possible to inject a mechanical torque R onto the high pressure shaft 22 in order to facilitate the restarting of the aircraft turbomachine T following an in-flight stop, caused for example by environmental disturbances such as the ingestion of birds.

[0043] The invention is particularly advantageous in that the electrical power supply of the electrical restart machine ME2 is provided by taking mechanical power from the low pressure shaft 21, which allows autonomous and independent restart of the turbomachine T, without taking electrical power from the electrical network of the aircraft RA. The sizing of certain equipment, such as the fuel supply system, can advantageously be reduced. The invention is particularly suitable for a situation of in-flight shutdown of all the turbomachines of the aircraft, known to those skilled in the art by the English term "total engine flame out".

[0044] According to a preferred aspect illustrated in the, the electrical restart machine ME2 is also electrically connected to the electrical network of the aircraft RA, in this example by electrical connection to the terminals of the switching device 33. This makes it possible to inject the power taken from the low pressure shaft 21 into the electrical network of the aircraft RA and conversely to electrically supply the electrical restart machine ME2 with the power from the electrical network of the aircraft RA.

[0045] As illustrated in the, the electrical rectifier 31 and the electrical converter 32 make it possible to transfer the power from the electrical generator ME1 to the electrical restart machine ME2 despite their difference in rotation speed. The switching device 33 makes it possible to authorize or prohibit the transfer of power and is controlled by a switching signal S1 from the control device 4, for example in the form of a computer of the aircraft. The closed state F1, F2 is preferably triggered when the speed M of the low pressure shaft 21 decreases below a threshold value, for example measured by a speed sensor 5. Other parameters can be checked, such as the absence of a fire starting or the altitude of the aircraft.

[0046] According to a preferred aspect illustrated in the, the electrical power modulation device D comprises two modulation states, namely a low transmission state adapted for driving the lubrication device 8 of the turbomachine T and a high transmission state adapted for driving the high pressure shaft 22.

[0047] In practice, the high transmission state is suitable for restarting the turbomachine T while the low transmission state is suitable for a transient phase, following the shutdown of the turbomachine T and preceding the restart. The low transmission state is in particular sufficient to drive the aircraft turbomachine according to an autorotation regime known under the English term “windmilling”. The high transmission state makes it possible to drive the high pressure shaft 22 at a sufficient rotational speed allowing restarting and therefore fuel injection. The high transmission state also makes it possible to drive the lubrication device 8.

[0048] During the transient phase, the aircraft is placed in a certified re-ignition domain with conditions suitable for restarting, namely a maximum altitude of the order of 30,000 feet and a minimum speed of the order of 230 knots. This transient phase typically takes the form of a descent phase of the aircraft from its cruising altitude of the order of 40,000 feet, during which the low pressure shaft 21 and the high pressure shaft 22 unscrew until they stabilize at the autorotation speed. The low transmission state of the electrical power modulation device D advantageously allows during this phase for the electrical restart machine ME2 to supply a torque R' to the lubrication device 8 to continue to ensure the lubrication of the turbomachine T.

[0049] The low transmission state also makes it possible to maintain a minimum rotation speed of the high pressure shaft 22, making it possible to prevent the occurrence of a blocking phenomenon of the high pressure shaft 22, known under the English term “corelock”, caused by a difference in thermal expansion of the materials which can block the rotation of the blades.

[0050] The electric restart machine ME2 is for example mounted in the accessory relay box of the turbomachine T (not shown). The electric generator ME1 is for example mounted in the inter-vein compartment, known to those skilled in the art by the English term "compartment core". The electric generator ME1 is for example mechanically coupled to the low-pressure shaft 21 downstream of the combustion chamber 13 and upstream of the low-pressure turbine 15. The electric restart machine ME2 and the electric generator ME1 are for example in the form of permanent magnet or wound rotor synchronous machines.

[0051] According to a first embodiment of the invention illustrated in Figures 3 to 5, the electrical power supply system 3 comprises a low electrical resistance 34 and a high electrical resistance 35 connected in parallel between the electrical rectifier 31 and the electrical converter 32, together forming the electrical power modulation device D. Preferably, the low electrical resistance 34 has an electrical resistance of between 500 Ohms and 10,000 Ohms. The high electrical resistance 35 is greater than the low electrical resistance 34 and preferably of between 1000 Ohms and 10,000 Ohms.

[0052] In this example, the electrical power supply system 3 also comprises a first switch 331 mounted on the branch of the low electrical resistance 34, and a second switch 332 mounted on the branch of the high electrical resistance 35. These two switches together form the switching device 33. The switching device 33 could have been in another form, for example a switch selecting one or none of the parallel branches on which the electrical resistances 34, 35 are arranged.

[0053] With reference to the, the switching device 33 comprises an open state O in which the two switches 331, 332 are open. No direct current then flows between the electrical rectifier 31 and the electrical converter 32, and no alternating restart current CA2 is then transmitted to the electrical restart machine ME2. The open state O is suitable for normal in-flight operation of the aircraft turbomachine T, characterized for example by a measurement M of the rotational speed of the low-pressure shaft 21 greater than a predetermined threshold.

[0054] With reference to the, the switching device 33 comprises a first closed state F1, in which the direct current CC is modulated by the low electrical resistance 34. The direct current CC flowing between the electrical rectifier 31 and the electrical converter 32 is then high, and the restart alternating current CA2 supplied by the electrical converter 32 to the restart electrical machine ME2 is sufficient to drive the high pressure shaft 22 at a restart speed of the aircraft turbomachine T.

[0055] With reference to the, the switching device 33 comprises a second closed state F2, in which the direct current CC is modulated by the high electrical resistance 35. The direct current CC flowing between the electrical rectifier 31 and the electrical converter 32 is then weaker than in the first closed state F1, and the restart alternating current CA2 supplied by the electrical converter 32 to the restart electrical machine ME 2 is sufficient to power the lubrication device 8 and to drive the high pressure shaft 22 at a minimum speed to avoid the occurrence of the phenomenon of blocking of the high pressure shaft 22.

[0056] In the first embodiment of Figures 3 to 5, the control of the switches 331 and 332 ensures both the switching from the open state O to a closed state F1, F2 and the modulation between a low transmission state (first closed state F1) and a high transmission state (second closed state F2).

[0057] According to a second embodiment illustrated in the, the electrical power supply system 3 comprises a variable resistor 36 mounted between the electrical rectifier 31 and the electrical converter 32, as well as a switch forming the switching device 33. The variable resistor 36 forms the electrical power modulation device D and makes it possible to modulate the direct current CC, and therefore the alternating restart current CA2.

[0058] As illustrated in the, the variable resistor 36 is configured, from the modulation signal S2, to select an electrical resistance value over a predetermined range, preferably between 500 Ohms and 10,000 Ohms. Such a variation range advantageously allows the electrical power supply system 3 to provide a restart alternating current CA2 whose value is adapted depending on whether a low transmission state or a high transmission state is desired.

[0059] According to a third embodiment illustrated in the, the electrical power modulation device D is formed by the electrical converter 32, the output frequency of the restart alternating current CA2 of which can be controlled via the modulation signal S2. The switching device 33 is in the form of a switch. Preferably, the control device 4 determines the modulation signal S2 from a measurement M' of the rotational speed of the high-pressure shaft 22, measured for example by a high-pressure rotational speed sensor 6.

[0060] Controlling the frequency of the restart alternating current CA2 advantageously makes it possible to control the slip of the restart electric motor ME2, so as to precisely control the power transferred from the low pressure shaft 21 to the high pressure shaft 22. This makes it possible to adapt the transferred power depending on whether a low transmission state or a high transmission state is desired.

[0061] Alternatively, the electrical power modulation device D is in the form of the electrical rectifier 31, which is then in the form of an electrical converter, i.e. a member comprising a three-phase voltage rectifier with control of the transistors on each of the diode branches. The duty cycle of the transistors in the rectifier is then controlled so as to vary the alternating supply current CA1, and thus indirectly the alternating restart current CA2.

[0062] According to a fourth embodiment illustrated in the, the electric generator ME1 is preferably of the wound rotor synchronous type and forms the electric power modulation device D. The switching device 33 is in the form of a switch. The control device 4 is configured to control the magnetic excitation of the wound rotor of the electric generator ME1, via the modulation signal S2. The control of the magnetic excitation of the wound rotor of the electric generator ME1 makes it possible to control the alternating supply current CA1 generated by the electric generator ME1, and thus to modulate the direct current CC and therefore the alternating restart current CA2.

[0063] The control of the magnetic excitation of the wound rotor of the electric generator ME1 is preferably done by controlling the induction in the electric generator ME1. Preferably, the control device 4 determines the modulation signal S2 from a measurement M' of the rotation speed of the high pressure shaft 22, measured for example by a high pressure rotation speed sensor 6. Preferably, the control device 4 comprises a PID (proportional integral derivative) corrector configured to control the magnetic excitation of the wound rotor of the electric generator ME1 from a predetermined setpoint or given by the regulation computer and from the measurement M'.

[0064] With reference to the, the invention also relates to a method for restarting in flight an aircraft turbomachine T (preferably corresponding to the turbomachine previously described) following an in-flight stoppage, caused for example by environmental disturbances such as the ingestion of birds. As illustrated in the, the switching device 33 is initially in the open state O and the control device 4 controls E1 the closed state F of the switching device 33 and provides E2 one or more modulation setpoints S2 to the electrical power modulation device D.

[0065] The method is in practice implemented during a transient phase, following the shutdown of the turbomachine T and preceding the restart, in particular during the autorotation regime of the turbomachine T, during which the aircraft performs a descent to place itself in a certified re-ignition domain. During such a phase, the low pressure shaft 21 and the high pressure shaft 22 unscrew until they stabilize on an autorotation regime. The low pressure shaft 21 rotating at a speed lower than the predetermined threshold Mref1, the control device 4 determines a switching signal S1 to switch the switching device 33 into a closed state F, F1, F2, and preferably a first modulation signal S2, to command a low transmission state to the power modulation device D.This makes it possible, from the electric restart machine ME2, to supply a torque R' to the lubrication device 8 to continue to ensure the lubrication of the turbomachine T.

[0066] When the aircraft reaches an altitude suitable for restarting the aircraft turbomachine T, the control device 4 provides a second modulation signal S2 to the power modulation device D to control the high transmission state. This makes it possible to drive the restart electric machine ME2 at a speed sufficient to provide a torque R to the high pressure shaft 22 suitable for restarting.

[0067] When the restart of the aircraft turbomachine T is completed, for example when the speed of the low pressure shaft is greater than a second predetermined threshold Mref2, the control device 4 commands E1' the open state O of the switching device 33, so as to stop the drive of the electric restart machine ME2.

[0068] The method according to the invention is particularly suitable for a situation of in-flight shutdown of all the aircraft's turbomachines ("total engine flame out"), in that it allows autonomous and independent restarting of the turbomachine T solely by taking power from the low pressure shaft 21.

Claims

Aircraft turbomachine (T) comprising a low pressure shaft (21), a high pressure shaft (22) and an electrical restart machine (ME2) configured, when supplied by an alternating restart current (CA2), to rotate the high pressure shaft (22), the aircraft turbomachine (T) being characterized in that it comprises: an electrical power supply system (3) for the electrical restart machine (ME2) comprising: an electrical generator (ME1) configured to produce an alternating supply current (CA1) by taking a rotary torque from the low pressure shaft (21), an electrical rectifier (31) connected to the electrical generator (ME1) and configured to supply a direct current (DC) from the alternating supply current (CA1), an electrical converter (32) configured to supply the alternating restart current (CA2) to the electrical restart machine (ME2) from the direct current (DC),an electrical switching device (33) configured, in an open state (O), to prohibit the flow of direct current (DC) between the electrical rectifier (31) and the electrical converter (32), and in a closed state (F, F1, F2), to allow the flow of direct current (DC) between the electrical rectifier (31) and the electrical converter (32), and an electrical power modulation device (D) configured to modulate the restart alternating current (CA2) from at least one modulation setpoint (S2), a control device (4) configured, during an in-flight restart of the aircraft turbomachine (T), to control the closed state (F, F1, F2) of the switching device (33) and emit the modulation setpoint (S2), so that the restart electrical machine (ME2) rotates the high-pressure shaft (22)., Aircraft turbomachine (T) according to claim 1, in which the modulation setpoint (S2) is a function of a measurement (M') of the rotation speed of the high pressure shaft (22). Aircraft turbomachine (T) according to one of claims 1 and 2, comprising a lubrication device (8) coupled to the electric restart machine (ME2), the electric power modulation device (D) having at least: a low transmission state suitable for driving the lubrication device (8), a high transmission state suitable for driving the high pressure shaft (22). Aircraft turbomachine (T) according to one of claims 1 to 3, in which:the electrical power system (3) comprises at least one low electrical resistance (34) and one high electrical resistance (35) mounted in parallel between the electrical rectifier (31) and the electrical converter (32) and together forming the electrical power modulation device (D), andthe switching device (33) comprises a first closed state (F1), in which the direct current (DC) is modulated by the low electrical resistance (34), and a second closed state (F2), in which the direct current (DC) is modulated by the high electrical resistance (35). Aircraft turbomachine (T) according to one of claims 1 to 3, in which the electrical power supply system (3) comprises at least one variable resistor (36) mounted between the electrical rectifier (31) and the electrical converter (32) and forming the electrical power modulation device (D). Aircraft turbomachine (T) according to one of claims 1 to 3, in which the electrical converter (32) is configured to provide a restart alternating current (CA2), of frequency controllable by the control device (4), and forms the electrical power modulation device (D). Aircraft turbomachine (T) according to one of claims 1 to 3, in which the electric generator (ME1) is of the wound rotor synchronous type and forms the electric power modulation device (D), the control device (4) being configured to control the magnetic excitation of the wound rotor of the electric generator (ME1). Aircraft turbomachine (T) according to one of claims 1 to 7, in which the control device (4) is configured to control the closed state (F, F1, F2) of the switching device (33) when a measurement (M) of the rotation speed of the low pressure shaft (21) is lower than a predetermined threshold (Mref1). Method for restarting an aircraft turbomachine (T) in flight according to one of claims 1 to 8, in which the switching device (33) is initially in the open state (O) and, during a restart in flight of the aircraft turbomachine (T): the control device (4) controls (E1) the closed state (F) of the switching device (33), the control device (4) provides (E2) a modulation setpoint (S2) to the electrical power modulation device (D), then the electrical restart machine (ME2) drives the high pressure shaft (22) in rotation from the alternating restart current (CA2) provided by the electrical power supply system (3). In-flight restart method according to claim 9, wherein the aircraft turbomachine (T) comprises a lubrication device (8) coupled to the electric restart machine (ME2) and the control device (4) provides (E2): A first modulation setpoint (S2) of a low transmission state of the electric power modulation device (D) adapted for driving the lubrication device (8), then A second modulation setpoint (S2) of a high transmission state of the electric power modulation device (D) adapted for driving the high pressure shaft (22),

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