Turbine engine comprising a moveable unducted fan and a static unducted flow straightener

Abstract

The invention relates to an aircraft turbine engine comprising: - an unducted fan; - an unducted flow straightener comprising at least one guide vane (6) with variable pitch about an axis of rotation (Y); - an adjustment system (19) for adjusting the pitch of the guide vane (6), wherein the adjustment system (19) comprises an actuating device (20) intended for actuating the guide vane (6) and comprising an electric motor (21); characterised in that the adjustment system (19) further comprises a braking device (22) configured to occupy an active position in which the braking device (22) prevents the guide vane (6) from rotating about the axis of rotation (Y) when the actuating device (20) is stationary, and a passive position in which the braking device (22) allows the guide vane (6) to rotate about the axis of rotation (Y) when the actuating device (20) is in motion.

Description

[0001] DESCRIPTION

[0002] TITLE: TU RBOMACHINE COMPRISING AN UNCOVERED MOBILE BLOWER AND AN UNCOVERED FIXED RECTIFIER

[0003] Technical field of the invention

[0004] The present invention relates to a turbomachine comprising an unducted mobile fan and an unducted fixed rectifier, and more precisely to the adjustment of the timing of the guide vanes of the rectifier.

[0005] Technical background

[0006] A turbomachine may include an unducted moving fan that is rotated by a turbine associated with a gas generator and an unducted stationary rectifier that is configured to straighten at least a portion of the airflow generated by the fan.

[0007] Such a high bypass ratio turbomachine has the advantage of excellent efficiency, including reduced fuel consumption and carbon dioxide emissions.

[0008] The rectifier comprises an annular row of variable-pitch guide vanes, i.e. guide vanes whose pitch (and more precisely the pitch angle) is adjustable depending in particular on the flight parameters and the operating speeds of the turbomachine.

[0009] To adjust the timing of the guide vanes, the turbomachine includes an adjustment system which can be common to all the guide vanes or specific to each of the guide vanes.

[0010] The adjustment system is placed in a compartment which is delimited in particular by an external fairing which forms the external aerodynamic lines of the turbomachine.

[0011] Traditionally, the adjustment system comprises one or more hydraulic cylinders and a mechanism specific to each of the guide vanes. Each mechanism comprises, for example, several connecting rods and is configured to transform the movement initiated by the hydraulic cylinder(s) into a rotational movement of the corresponding guide vane.

[0012] One disadvantage of such an adjustment system is that it is bulky.

[0013] Engine manufacturers are therefore looking for alternatives to reduce the size of the adjustment system, in particular to be able to integrate additional equipment without having to increase the dimensions of the external aerodynamic lines of the turbomachine.

[0014] One solution could be to have an adjustment system comprising an electric motor specific to each of the guide vanes. The rotor of each electric motor would then be linked directly or indirectly to the corresponding guide vane in order to adjust its setting.

[0015] A major disadvantage of such an embodiment is the requirement to constantly monitor the various electric motors, which is particularly detrimental to the power consumption and the service life of the electric motors.

[0016] The objective of the present invention is to improve the variant stated above which uses electric motors to overcome the aforementioned drawbacks.

[0017] The prior art also includes WO2021 / 165616A1, US5242265A and WO2022 / 263752A1.

[0018] Summary of the invention

[0019] The invention thus proposes a turbomachine for an aircraft comprising:

[0020] - an unducted fan which is rotatable around a longitudinal axis X;

[0021] - an unducted rectifier which is fixed in rotation around the longitudinal axis X, the rectifier being configured to straighten at least a portion of an air flow generated by the unducted fan, the rectifier comprising at least one variable-pitch guide vane around an axis of rotation Y which is substantially perpendicular to the longitudinal axis X, the guide vane being integral with a shaft which is guided in rotation around the axis of rotation Y in a housing, the housing being fixed to a fixed structure of the turbomachine;

[0022] - a system for adjusting the timing of the guide vane, the adjustment system comprising a device for actuating the guide vane around the axis of rotation Y, the actuating device comprising an electric motor; characterized in that the adjustment system further comprises a braking device configured to occupy an active position in which the braking device blocks the rotation of the guide vane around the axis of rotation Y when the actuating device is stopped, and a passive position in which the braking device allows the rotation of the guide vane around the axis of rotation Y when the actuating device is running.

[0023] The incorporation of a braking device into the adjustment system means that the electric motor no longer needs to be powered when the actuating device is stopped, thus optimizing its lifespan.

[0024] The braking device also makes it possible to considerably reduce the electrical requirements of the control system, and consequently of the turbomachine.

[0025] The turbomachine according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another:

[0026] - the braking device is mounted in the housing;

[0027] - the shaft is guided in rotation around the axis of rotation Y in the housing via a first bearing and a second bearing, the braking device being arranged between the first bearing and the second bearing;

[0028] - the electric motor is mounted on an internal end of the housing with reference to the longitudinal axis X;

[0029] - the braking device includes:

[0030] -- a caliper secured to the housing; -- a disc secured to the shaft and placed in the caliper;

[0031] -- a piston movable in translation along the axis of rotation Y, the piston being set in motion by an electromagnetic assembly which is carried by the caliper;

[0032] -- a compression spring which bears on both the piston and the electromagnetic assembly; the disc being blocked by the piston under the action of the spring, when the braking device is in the active position, the electromagnetic assembly then not being electrically powered; the disc being released by the piston under the action of the electromagnetic assembly which is electrically powered, when the braking device is in the passive position, the spring then being compressed by the piston;

[0033] - the piston comprises an annular head around the axis of rotation Y and several feet projecting from an internal face of the head, each foot comprising a blind orifice in which an electromagnet of the electromagnetic assembly is housed with play;

[0034] - the piston comprises several tabs projecting from a peripheral face of the head, each tab sliding in a groove formed in the caliper, so as to guide the piston in translation relative to the caliper;

[0035] - the braking device is hydraulic or mechanical or electromagnetic;

[0036] - the actuating device further comprises an epicyclic gear reducer which comprises:

[0037] -- a mobile solar system rotating around the Y axis of rotation and attached to a rotor of the electric motor;

[0038] -- a fixed crown which surrounds the sun and which is attached to the case;

[0039] -- at least one rotating mobile satellite, meshed with both the sun and the crown;

[0040] -- a mobile planet carrier rotating around the Y axis of rotation and secured to the shaft;

[0041] - the reducer is mounted in the housing;

[0042] - the planet carrier is made in one piece with the shaft;

[0043] - the adjustment system comprises a position sensor associated with the shaft or a rotor of the electric motor, so as to measure the timing of the guide vane;

[0044] - the adjustment system is controlled by an electronic control card which is specific to the guide vane;

[0045] - the turbomachine comprises a ducted fan which is rotatable around the longitudinal axis X and which is surrounded by a nacelle, the nacelle internally defining a compartment in which the housing and the adjustment system are located.

[0046] Brief description of the figures

[0047] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0048] [Fig.1] Figure 1 is a schematic view in longitudinal half-section of an aircraft turbomachine according to a first embodiment of the invention;

[0049] [Fig.2] Figure 2 is a schematic view in longitudinal half-section of an aircraft turbomachine according to a second embodiment of the invention;

[0050] [Fig.3] Figure 3 is a front view of a system for adjusting the timing of a guide vane of a rectifier of the turbomachines illustrated in Figures 1 and 2;

[0051] [Fig.4] Figure 4 is a longitudinal sectional view of the adjustment system illustrated in Figure 3;

[0052] [Fig.5] Figure 5 is a cross-sectional view of the adjustment system along the section plane VV of Figure 4, with the housing hidden; [Fig.6] Figure 6 is a perspective view of the adjustment system, with the housing and the braking device hidden;

[0053] [Fig.7] Figure 7 is a detailed view of the braking device of the adjustment system;

[0054] [Fig.8] Figure 8 is a detailed view of the disc of the braking device;

[0055] [Fig.9] Figure 9 is a detail view of the braking device, the electromagnetic assembly of the braking device being shown transparently and the caliper of the braking device being hidden;

[0056] [Fig.10] Figure 10 is a detailed view of the braking device, the electromagnetic assembly and the caliper of the braking device being shown transparently;

[0057] [Fig.11] Figure 11 is a control diagram of one adjustment system; [Fig.12] Figure 12 is a control diagram of several adjustment systems.

[0058] Detailed description of the invention

[0059] Figures 1 and 2 show a turbomachine 1a, 1b with longitudinal axis X for an aircraft 2, such as an airplane. The turbomachine 1a, 1b comprises an unducted fan 3 and an unducted rectifier 4.

[0060] The term "unducted" associated with the fan 3 means that the blades 5 of the fan 3 are not surrounded at their free end by a shroud. Similarly, the term "unducted" associated with the rectifier 4 means that the guide vanes 6 of the rectifier 4 are not surrounded at their free end by a shroud.

[0061] As illustrated in Figures 1 and 2, the unducted fan 3 is rotatable about the axis X and driven in rotation by a power turbine 50 associated with a gas generator 7 arranged here downstream of the unducted fan 3. The unducted fan 3 comprises an annular row of variable-pitch blades 5.

[0062] When the turbomachine 1 a, 1 b is in “propulsor” mode, the fan 3 generates an airflow which flows from upstream to downstream around the outer fairings 51 of the streamlined body of the turbomachine 1 a, 1 b, so as to propel or move the aircraft 2 forward. The turbomachine 1 a, 1 b can also operate in “reverser” mode, so as to brake the aircraft 2, at the time of its landing.

[0063] By convention in the present application, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the air flow, when the turbomachine 1 a, 1 b is in “propulsor” mode.

[0064] The power turbine 50 (or low pressure turbine) is intended to drive the unducted fan 3 in rotation. The unducted fan

[0065] 3 can be driven in rotation by the power turbine 50 via a speed reducer. The gas generator 7 conventionally comprises, from upstream to downstream, at least one compressor, a combustion chamber, and at least one expansion turbine (or high-pressure turbine). The compressor and the expansion turbine are connected in rotation to each other via a transmission shaft. The gas generator 7 is supplied with air by an air inlet 8a, 8b which opens between the unducted fan 3 and the unducted rectifier 4.

[0066] As illustrated in Figures 1 and 2, the unducted rectifier 4 is fixed in rotation about the X axis and is configured to straighten at least a portion of the airflow generated by the unducted fan 3. The rectifier 4 is arranged here directly downstream of the unducted fan 3. The rectifier

[0067] 4 comprises a row of guide vanes 6 (stator vanes or OGV vanes for “Outlet Guide Vane”) with variable pitch, each guide vane 6 being pitched around an axis of rotation Y which is substantially perpendicular to the axis X.

[0068] According to the first embodiment illustrated in Figure 1, the air inlet 8a directly feeds the gas generator 7. The air inlet 8a, the gas generator 7, and the power turbine 50 are surrounded by an annular compartment 9 around the axis X which is commonly called the “Core compartment”. The guide vanes 6 are here arranged around this Core compartment 9. According to the second embodiment illustrated in Figure 2, the turbomachine 1b further comprises a ducted fan 10 which is placed in the air inlet 8b, this ducted fan 10 being better known by the English designation “Mid-Fan”. The ducted fan 10 is rotatable around the axis X and is driven in rotation by the power turbine 50 (or low-pressure turbine). The ducted fan 10 is surrounded by a nacelle 11 which internally defines an annular compartment 12 around the X axis which is commonly called a “Mid-Fan compartment”.The gas generator 7 and the power turbine 50 are surrounded by an annular compartment 13 around the axis X which is commonly called the “Core compartment”. The air inlet 8b is divided into a primary vein 14 which feeds the gas generator 7 and into a secondary vein 15 which is defined between the Core and Mid-Fan compartments 12, 13. The guide vanes 6 are here arranged around the Mid-Fan compartment 12, and in other words around the nacelle 11.

[0069] As illustrated in Figures 3 and 4, each guide vane 6 is secured to a shaft 16 which is guided in rotation about the Y axis in a housing 17, the housing 17 being fixed to a fixed structure 18 of the turbomachine 1a, 1b. The turbomachine 1a, 1b comprises a system 19 for adjusting the setting for each guide vane 6. The adjustment system 19 comprises an actuation device 20 for the guide vane 6 about the Y axis, the actuation device 20 comprising an electric motor 21.

[0070] According to the invention, the adjustment system 19 further comprises a braking device 22 configured to occupy an active position in which the braking device 22 blocks the rotation of the guide vane 6 around the Y axis when the actuating device 20 is stopped, and a passive position in which the braking device 22 authorizes the rotation of the guide vane 6 around the Y axis when the actuating device 20 is running.

[0071] The term “in operation” associated with the actuating device 20 means that the actuating device 20 (and in particular the electric motor) generates mechanical power to actuate the guide vane 6 around the Y axis. Conversely, the term “at a standstill” associated with the actuating device 20 means that the actuating device 20 (and in particular the electric motor which is no longer powered) does not generate any mechanical power to actuate the guide vane 6 around the Y axis.

[0072] The incorporation of a braking device into the adjustment system makes it possible to no longer keep the electric motor under voltage and therefore no longer exert torque when the actuating device is stopped, so as to optimize the service life of the device and to reduce to a certain extent the electrical power consumed by the entire system.

[0073] The braking device thus makes it possible to significantly reduce the electrical requirements of the control system, and consequently of the turbomachine. The braking device 22 can be mounted in the housing 17 or outside the housing 17.

[0074] The shaft 16 can be guided in rotation around the Y axis in the housing 17 via a first bearing 23 and a second bearing 24. In the present case, the braking device 22 is advantageously arranged between the first bearing 23 and the second bearing 24. Indeed, such an arrangement of the braking device 22 guarantees optimal alignment between the moving and fixed parts of the braking device 22.

[0075] The electric motor 21 may be a direct current motor, a stepper motor, an alternating current motor, etc.

[0076] The electric motor 21 can be single coil or double coil, in case redundancy is desired.

[0077] The electric motor 21 can be mounted in the housing 17 or outside the housing 17.

[0078] The braking device 22 may be electromagnetic, hydraulic, mechanical, etc.

[0079] The actuating device 20 may further comprise a gear train reducer, and preferably an epicyclic gear train reducer 25. A gear train reducer allows the output speed to be reduced while increasing the output torque.

[0080] A 25 epicyclic gear reducer has the advantage of having a high reduction ratio while being compact.

[0081] The gear reducer may include one or more reduction stages, depending on the desired reduction ratio.

[0082] The adjustment system 19 may comprise a position sensor associated with the shaft 16 or with a rotor 26 of the electric motor 21, so as to measure the setting of the guide vane 6, and thus precisely control the guide vane 6.

[0083] The position sensor can be an angular sensor of the RVDT type for “Rotary Variable Differential Transformer” or a linear sensor of the LVDT type for “Linear Variable Differential Transformer”.

[0084] The different adjustment systems 19 can be controlled independently, in common or in groups (two or three for example).

[0085] According to the embodiment illustrated in Figures 3 to 10, the adjustment system 19 comprises an actuating device 20 which is here a geared motor and an electromagnetic braking device 22.

[0086] The geared motor 20 comprises the electric motor 21 and an epicyclic gear reducer 25.

[0087] The guide vane 6 is here secured to the shaft 16 via fixing means which may be screws.

[0088] As illustrated in Figure 4, the housing 17 internally defines a housing in which are mounted two rolling bearings 23, 24 intended to guide the shaft 16, the electromagnetic braking device 22 arranged between the two rolling bearings 23, 24 and the epicyclic gear reducer 25.

[0089] The electric motor 21 is mounted on an internal end of the housing 17 with reference to the X axis. More precisely, the motor 21 comprises a stator 27 fixed to the internal end of the housing 17 via, for example, an annular row of screws around the Y axis, and a rotor 26 movable in rotation around the Y axis. As illustrated in FIG. 3, the housing 17 externally comprises a fixing lug 28 which is fixed to the fixed structure 18 of the turbomachine 1 a, 1 b via, for example, two bolts.

[0090] As illustrated in particular in Figures 4 and 7, the electromagnetic braking device 22 comprises:

[0091] - a stirrup 29 secured to the housing 17;

[0092] - a disc 30 secured to the shaft 16 and placed in the caliper 29;

[0093] - a piston 31 movable in translation along the Y axis, the piston 31 being set in motion by an electromagnetic assembly 32 which is carried by the caliper 29;

[0094] - a compression spring 33 which bears both on the piston 31 and on the electromagnetic assembly 32.

[0095] The disc 30 is blocked by the piston 31 under the action of the spring 33, when the braking device 22 is in the active position. The electromagnetic assembly 32 is then not electrically powered. The braking device 22 is thus normally in the active position.

[0096] The disc 30 is released by the piston 31 under the action of the electromagnetic assembly 32 which is electrically powered, when the braking device 22 is in the passive position. The spring 33 is then compressed by the piston 31.

[0097] As illustrated in particular in Figures 8 and 9, the disc 30 is secured to the shaft 16 via grooves 34 of complementary shape. The disc 30 is located directly between a wing 35 of the caliper 29 and the piston 31.

[0098] As illustrated in Figures 4, 7 and 9, the piston 31 comprises an annular head 36 around the Y axis and several feet 37 projecting from an internal face of the head 36. The feet 37 are distributed regularly around the Y axis. Each foot 37 comprises a blind orifice 38 in which an electromagnet 39 of the electromagnetic assembly 32 is housed with clearance.

[0099] Each electromagnet 39 comprises an iron core surrounded by a coil which is electrically powered or not, depending on the active or passive position of the braking device 22. As illustrated in FIGS. 9 and 10, the piston 31 further comprises several tabs 40 projecting from a peripheral face of the head 36. The tabs 40 are distributed regularly around the axis Y. Each tab 40 slides in a groove 41 formed in the caliper 29, so as to guide the piston 31 in translation relative to the caliper 29.

[0100] As illustrated in Figures 4 and 5, the epicyclic gear reducer 25 comprises:

[0101] - a solar 42 (or planetary) mobile in rotation around the Y axis and secured to the rotor 26 of the electric motor 21;

[0102] - a fixed crown 43 which surrounds the sun 42 and which is integral with the case 17;

[0103] - three rotating satellites 44, each satellite 44 being meshed with both the sun 42 and the crown 43;

[0104] - a planet carrier 45 movable in rotation around the Y axis and secured to the shaft 16.

[0105] More precisely, as illustrated in Figure 5, the three satellites 44 are distributed regularly around the Y axis. Each satellite 44 is guided in rotation on a finger 46 of the satellite carrier 45 via one or more bearings.

[0106] The rotor 26 of the electric motor 21 is connected in rotation with the solar 42 by connecting means (for example grooves) or by shrinking.

[0107] As illustrated in Figure 4, the planet carrier 45 is made in one piece (or integrally formed) with the shaft 16, the planet carrier 45 and the shaft 16 thus being in one piece. Alternatively, the planet carrier 45 could be attached and fixed to the shaft 16, for example via screws or bolts.

[0108] The control system 19 is electrically powered via an electrical power distribution box (known by the English acronym PMU for “Power Management Unit”) which may already be installed in the turbomachine 1 a, 1 b to power other equipment, namely one or more de-icing devices and / or one or more electrical machines configured to operate in “motor” and “generator” mode, or which may be installed in the turbomachine 1 a, 1 b specifically for the control system 19. The electrical machines are intended to participate in the electrical hybridization of the turbomachine 1 a, 1 b.

[0109] The geared motor 20 and the electromagnetic braking device 22 are thus connected to the electrical power distribution box via one or more electrical harnesses. It is possible to use a single electrical harness for different power supplies, for example an electric motor and a defrosting device, so as to minimize the space requirement.

[0110] According to the embodiment illustrated in Figure 1, the housing 17 and the adjustment system 19 associated with each of the guide vanes 6 are located in the Core compartment 9.

[0111] According to the embodiment illustrated in Figure 2, the housing 17 and the adjustment system 19 associated with each of the guide vanes 6 are located in the Mid-Fan compartment 12.

[0112] Concerning the assembly, the complete housings 17 are assembled before sending the turbomachine 1a, 1b to the aircraft manufacturer. Thus, when the turbomachine 1a, 1b arrives at the aircraft manufacturer, all that remains is to secure each guide vane 6 to the corresponding shaft 16.

[0113] As illustrated in Figure 11, each adjustment system 19 is controlled by an electronic control card 47 which is specific to the guide vane 6. Each electrical control card 47 is associated with an identifier which is unique in order to know the mounting position on the turbomachine of each adjustment system 19.

[0114] As illustrated in Figure 12, the various electronic control cards are connected to a control box 48 which is common to all the guide vanes 6, via a communication network 49. The control box 48 is connected to one or more engine computers (better known by the English acronym EEC for “Electronic Engine Control”).

[0115] When the electronic control card 47 receives a setting instruction, the braking device 22 switches to the passive position and the actuating device 20 starts up, to obtain the desired setting. Once the adjustment has been made, the braking device 22 returns to the active position and the control box 48 is informed of this new angular position via the communication network 49.

[0116] The control unit 48 can send either a common timing instruction to all the electronic control cards (in absolute or relative mode) or a specific timing instruction to one or more electronic control cards using their identifier. The control unit 48 confirms the new angular positions to the engine computer(s), generally on the two channels of each of the computers.

[0117] As an alternative to the embodiment illustrated in Figures 11 and 12, the adjustment systems 19 can be controlled directly by one or more engine computers (better known by the English acronym EEC for “Electronic Engine Control”). The adjustment systems 19 can then be electrically powered in whole or in part by the engine computer(s). Such an alternative embodiment makes it possible to control the guide vanes 6 jointly. To enhance the safety of the turbomachine, the rotors 26 of the electric motors 21 can be connected to each other by flexible shafts (flexshaft in English), so as to synchronize all of the guide vanes 6 even if one of the electric motors 21 is faulty.

[0118] The embodiments illustrated in Figures 1 and 2 are in no way limiting. For example, with reference to Figure 1, the unducted fan 3 could be arranged downstream of the gas generator 7 and the power turbine 50, the unducted rectifier 4 would then be located upstream of the unducted fan 3.

Claims

CLAIMS 1. Turbomachine (1 a, 1 b) for an aircraft (2) comprising: - an unducted fan (3) which is rotatable around a longitudinal axis (X); - an unducted rectifier (4) which is fixed in rotation about the longitudinal axis (X), the rectifier (4) being configured to straighten at least a portion of an air flow generated by the unducted fan (3), the rectifier (4) comprising at least one guide vane (6) with variable pitch about an axis of rotation (Y) which is substantially perpendicular to the longitudinal axis (X), the guide vane (6) being integral with a shaft (16) which is guided in rotation about the axis of rotation (Y) in a housing (17), the housing (17) being fixed to a fixed structure (18) of the turbomachine (1 a, 1 b); - a system (19) for adjusting the setting of the guide vane (6), the adjustment system (19) comprising a device (20) for actuating the guide vane (6) around the axis of rotation (Y), the actuating device (20) comprising an electric motor (21); characterized in that the adjustment system (19) further comprises a braking device (22) configured to occupy an active position in which the braking device (22) blocks the rotation of the guide vane (6) around the axis of rotation (Y) when the actuating device (20) is stopped, and a passive position in which the braking device (22) allows the rotation of the guide vane (6) around the axis of rotation (Y) when the actuating device (20) is running.

2. Turbomachine (1a, 1b) according to claim 1, characterized in that the braking device (22) is mounted in the housing (17).

3. Turbomachine (1a, 1b) according to claim 2, characterized in that the shaft (16) is guided in rotation around the axis of rotation (Y) in the housing (17) via a first bearing (23) and a second bearing (24), the device of braking (22) being arranged between the first bearing (23) and the second bearing (24).

4. Turbomachine (1a, 1b) according to one of the preceding claims, characterized in that the electric motor (21) is mounted on an internal end of the housing (17) with reference to the longitudinal axis (X).

5. Turbomachine (1a, 1b) according to one of the preceding claims, characterized in that the braking device (22) comprises: - a stirrup (29) secured to the housing (17); - a disc (30) secured to the shaft (16) and placed in the caliper (29); - a piston (31) movable in translation along the axis of rotation (Y), the piston (31) being set in motion by an electromagnetic assembly (32) which is carried by the stirrup (29); - a compression spring (33) which bears both on the piston (31) and on the electromagnetic assembly (32); the disc (30) being blocked by the piston (31) under the action of the spring (33), when the braking device (22) is in the active position, the electromagnetic assembly (32) then not being electrically powered; the disc (30) being released by the piston (31) under the action of the electromagnetic assembly (32) which is electrically powered, when the braking device (22) is in the passive position, the spring (33) then being compressed by the piston (31).

6. Turbomachine (1a, 1b) according to claim 5, characterized in that the piston (31) comprises a head (36) annular around the axis of rotation (Y) and several feet (37) projecting from an internal face of the head (36), each foot (37) comprising a blind orifice (38) in which is housed with play an electromagnet (39) of the electromagnetic assembly.

7. Turbomachine (1a, 1b) according to claim 6, characterized in that the piston (31) comprises several tabs (40) projecting from a peripheral face of the head (36), each tab (40) sliding in a groove (41) formed in the caliper (29), so as to guide the piston (31) in translation relative to the caliper (29).

8. Turbomachine (1a, 1b) according to one of claims 1 to 4, characterized in that the braking device (22) is hydraulic or mechanical or electromagnetic.

9. Turbomachine (1a, 1b) according to one of the preceding claims, characterized in that the actuating device (20) further comprises an epicyclic gear reducer (25) which comprises: - a solar (42) mobile in rotation around the axis of rotation (Y) and secured to a rotor (26) of the electric motor (21); - a fixed crown (43) which surrounds the sun (42) and which is integral with the housing (17); - at least one satellite (44) mobile in rotation, and meshed with both the sun (42) and the crown (43); - a planet carrier (45) movable in rotation around the axis of rotation (Y) and secured to the shaft (16).

10. Turbomachine (1a, 1b) according to claim 9, characterized in that the reducer (25) is mounted in the housing (17).

11. Turbomachine (1 a, 1 b) according to claim 9 or 10, characterized in that the planet carrier (45) is made in one piece with the shaft (16).

12. Turbomachine (1a, 1b) according to one of the preceding claims, characterized in that the adjustment system (19) comprises a sensor of position associated with the shaft (16) or with a rotor (26) of the electric motor (21), so as to measure the timing of the guide vane (6).

13. Turbomachine (1a, 1b) according to one of the preceding claims, characterized in that the adjustment system (19) is controlled by an electronic control card (47) which is specific to the guide vane (6).

14. Turbomachine (1 b) according to one of the preceding claims, characterized in that the turbomachine (1 b) comprises a ducted fan (10) which is rotatable about the longitudinal axis (X) and which is surrounded by a nacelle, the nacelle (11) internally defining a compartment (12) in which the housing (17) and the adjustment system (19) are located.

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