System for correcting the precession movement of a turbomachine shaft, turbomachine and associated methods

Abstract

A correction system (9) for the precession of a shaft (2) of a turbomachine (T) comprising a magnetic element (7), the shaft (2) being rotatably mounted about a shaft axis (X) in a fixed housing (1), the correction system (9) comprising at least one measuring device (4) configured to determine a precession level (NP) of the shaft (2), at least one electromagnet (5) configured to generate a magnetic force (F) on the magnetic element (7) of the shaft (2) from a control command (COM), and at least one computer (6) configured to determine the control command (COM) as a function of the precession level (NP) so as to generate an overall magnetic force opposing the precession of the shaft (2) in order to dampen it. Abstract figure: Figure 4

Description

Title of the invention: System for correcting a precession movement of a shaft of a turbomachine, turbomachine and associated method Technical field

[0001] The present invention relates to the field of turbomachines. The invention relates more particularly to the correction of a precession movement of a shaft of an aircraft turbomachine.

[0002] In a known manner, with reference to [Fig. 1], there is shown schematically an aircraft turbomachine T comprising a shaft 2 secured to a fan 20 and a plurality of mobile compressor blades 21. The shaft 2 is guided axially around a shaft axis X by one or more bearings RI secured to a fixed casing 1 called stator. The aircraft turbomachine T also comprises rectifier vanes 11, secured to the fixed casing 1, for straightening an air flow A accelerated by the mobile compressor blades 21.

[0003] In practice, the shaft 2 of a turbomachine T undergoes vibrations during its rotation which are likely to induce a precessional movement (also called orbiting) of the shaft 2. With reference to [Fig. 2], a precessional movement of the shaft 2 is shown between successive time instants t1, t2, t3. In this example, the precessional movement P+ is clockwise but it goes without saying that it could also be counterclockwise. Such a precessional movement P+ can lead to a degradation of the performance as well as premature wear of the turbomachine T (fatigue of the parts and / or increased clearances at the moving wheels and seals). In addition, it can be a source of discomfort for the passengers of the aircraft since these precessions transmit vibrations via the bearings RI supporting the shaft 2 in the structures and the aircraft cell.

[0004] To correct the precession movement P+, it is known in the prior art to provide mechanical damping members but these are dimensioned so as to dampen as effectively as possible a predetermined vibration mode of the shaft 2. Such mechanical damping members are thus not very effective on the other vibration modes present in the operating range of the aircraft turbomachine T, which presents a drawback.

[0005] The invention aims to eliminate at least some of these drawbacks. PRESENTATION OF THE INVENTION

[0006] The invention relates to a system for correcting a precession movement of a shaft of a turbomachine comprising a magnetic element, the shaft being rotatably mounted along a shaft axis in a fixed casing, the correction system comprising: • At least one measuring device configured to determine a level of precession of the shaft relative to the fixed casing of the turbomachine, • At least one electromagnet configured to generate a magnetic force on the magnetic element of the shaft from a control command, and • At least one computer configured to determine the control order based on the precession level so as to generate an overall magnetic force opposing the precession movement of the shaft to dampen it.

[0007] Thanks to the invention, a precession movement can be corrected dynamically by applying a magnetic force which makes it possible to dampen the vibration modes of the shaft. Unlike the prior art, the correction system does not correct a single vibration mode. Furthermore, the correction can be calibrated in a practical manner by simply calibrating the control order, which is advantageous. The service life of the turbomachine is improved. Furthermore, this makes it possible to improve the comfort of passengers of an aircraft whose turbomachines are equipped with a correction system.

[0008] Preferably, the correction system comprises a plurality of electromagnets, each being configured to generate a magnetic force on the shaft from a control command, the computer being configured to determine a control command for each electromagnet as a function of the precession level so as to generate an overall magnetic force opposing the precession movement of the shaft to damp it.

[0009] The use of several electromagnets makes it possible to dampen the shaft by a plurality of magnetic forces. In addition, this makes it possible to precisely define the direction of the overall magnetic force opposing the precession movement of the shaft in order to damp it.

[0010] Preferably, the electromagnets are configured to be mounted on the fixed housing peripherally to the shaft, preferably at the same radial distance from the shaft axis.

[0011] Preferably, the electromagnets comprise at least one pair of electromagnets configured to be diametrically opposed relative to the shaft axis. Preferably, the correction system comprises at least 4 electromagnets spaced 90° apart. The direction of the overall magnetic force is defined with great precision.

[0012] According to one aspect of the invention, the computer is configured to successively activate each electromagnet so as to generate an overall magnetic force rotating opposing the precessional movement over time. The damping is thus synchronized with the precessional movement.

[0013] Preferably, the computer is configured to successively activate each electromagnet according to a phase advance relative to the precession movement. Such a phase advance makes it possible to dampen any future movement of the shaft in its precession movement.

[0014] Preferably, the electromagnets are activated successively in a progressive manner, two electromagnets being able to be active simultaneously.

[0015] According to one aspect of the invention, each electromagnet is configured to generate a magnetic force on the shaft in a radial direction relative to the shaft axis. The precession movement is thus directly corrected to realign the shaft along the shaft axis.

[0016] According to another aspect of the invention, each electromagnet is configured to generate a magnetic force on the shaft in a direction parallel to the shaft axis. The precession movement is thus corrected indirectly by applying a bending moment to the shaft to realign the shaft along the shaft axis.

[0017] Preferably, the correction system comprises at least one moving target configured to be mounted on the shaft and configured to interact with the measuring device, for example, optically, inductively or capacitively. The measurement of the precession level is more accurate, which improves the correction.

[0018] Preferably, the correction system comprises a plurality of measuring devices configured to be mounted on the fixed housing peripherally to the shaft, preferably at the same radial distance from the shaft axis.

[0019] The invention also relates to an aircraft turbomachine comprising a fixed casing and at least one shaft rotatably mounted along a shaft axis in the fixed casing, the shaft comprising at least one magnetic element, the turbomachine comprising a correction system, as presented previously, configured to generate a magnetic force on the magnetic element to oppose the precession movement of the shaft so as to dampen it.

[0020] Preferably, the shaft is integral with a fan and a plurality of movable compressor blades positioned radially outwardly relative to the shaft. The correction system is positioned radially between the shaft and the movable compressor blades.

[0021] The invention also relates to an aircraft comprising a turbomachine as presented previously.

[0022] The invention also relates to a method for correcting a precession movement of a shaft of an aircraft turbomachine comprising a fixed casing and at least one shaft rotatably mounted along a shaft axis in the fixed casing, the shaft comprising at least one magnetic element, the correction method comprising steps consisting of: • determine a level of precession of the shaft relative to the fixed casing of the turbomachine, and • generate a magnetic force on the magnetic element of the shaft, by means of at least one electromagnet, which is a function of the precession level so as to generate a magnetic force opposing the precession movement of the shaft to dampen it.

[0023] Preferably, the method comprises steps consisting of: • record the magnetic forces generated over time and • estimate a state of wear of the turbomachine from the magnetic forces recorded over time.

[0024] Advantageously, by monitoring the evolution of the applied magnetic force, the need for correction and, consequently, a state of wear of the turbomachine is estimated. If the applied magnetic force becomes too high, a maintenance step of the turbomachine must be carried out. PRESENTATION OF FIGURES

[0025] The invention will be better understood on reading the description which follows, 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.

[0026] [Fig.l] is a schematic representation of an aircraft turbomachine comprising a shaft.

[0027] [Fig.2] is a schematic representation of a precessional movement of a tree.

[0028] [Fig. 3] is a schematic representation of an aircraft turbomachine equipped with a correction system according to the invention.

[0029] [Fig.4] is a schematic representation of a correction system according to the invention.

[0030] [Fig. 5] is a schematic representation in axial half-section of an aircraft turbomachine comprising a shaft and a correction system according to a first embodiment of the invention.

[0031] [Fig.6] is a schematic cross-sectional representation of the correction system according to the first embodiment.

[0032] [Fig.7] and [Fig.8] are schematic representations of steps of correction of a precession movement of the shaft by the correction system according to the first embodiment.

[0033] [Fig. 9] is a schematic representation in axial half-section of an aircraft turbomachine comprising a shaft and a correction system according to a variant of the first embodiment of the invention.

[0034] [Fig. 10] is a schematic cross-sectional representation of the correction system according to the variant of the first embodiment.

[0035] [Fig. 11] is a schematic representation in axial half-section of an aircraft turbomachine comprising a shaft and a correction system according to the second embodiment.

[0036] [Fig. 12] is a schematic cross-sectional representation from downstream of the correction system according to the second embodiment.

[0037] 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

[0038] The invention will be presented for an aircraft turbomachine comprising a shaft which is subjected to vibrations during its operation. It nevertheless goes without saying that the invention can be applied to any turbomachine, in particular, in the industrial field.

[0039] By way of example, with reference to [Fig. 3], there is shown an aircraft turbomachine T comprising a shaft 2 rotatably mounted along a shaft axis X in a fixed casing 1. The shaft 2 is connected to a fan 20 making it possible to accelerate an air flow A from upstream to downstream. In [Fig. 3], the shaft axis X is oriented from upstream to downstream. Such a shaft 2 is likely to undergo vibrations during its operation generating a precession movement, also called unbalance or orbiting.

[0040] Preferably, the shaft 2 is a low-pressure shaft of a twin-spool turbomachine comprising a low-pressure shaft and a high-pressure shaft 103. In this example, [Fig. 3] also shows schematically a low-pressure compressor 101, a high-pressure compressor 102, a high-pressure turbine 104 and a low-pressure turbine 105.

[0041] According to the invention, the shaft 2 comprises at least one magnetic element configured to interact magnetically with a correction system 9 according to the invention.

[0042] According to a first aspect, the shaft 2 may be intrinsically magnetic, for example, if it comprises a metallic coating. According to a second aspect, the shaft 2 comprises one or more magnetic elements 7 ([Fig.4]) attached to its periphery so as to allow magnetic interactions.

[0043] For example, a peripheral ring or a plurality of independent magnetic elements (permanent magnets, etc.) may be positioned at the periphery of the shaft 2.

[0044] According to the invention, the turbomachine T comprises a correction system 9, shown in [Fig.3] and [Fig.4], configured to generate a magnetic force F on the shaft 2. This makes it possible to oppose a precession movement P+ of the shaft 2 in order to dampen it. Such a correction system 9 advantageously makes it possible to dampen any type of vibration mode, which extends the service life of the turbomachine T and improves passenger comfort.

[0045] As illustrated in [Fig. 4], the correction system 9 comprises at least one measuring device 4 configured to determine a precession level NP of the shaft 2 relative to the fixed casing 1 of the turbomachine T. Preferably, the measuring device 4 is in the form of a distance sensor configured to determine a precession movement P+. As will be presented later, several measuring devices 4 are preferably used to precisely determine a precession level NP. A measuring device 4 may be in the form of a capacitive sensor, an inductive sensor, an accelerometer or the like.

[0046] Precession level NP is understood to mean in particular a direction of precession and a precession intensity, for example, a distance of separation of the shaft 2 from the shaft axis X (eccentricity). Preferably, the precession level NP comprises the current position of the shaft 2 in its precession movement P+, i.e., the precession position. This advantageously makes it possible to dynamically correct a precession movement P+ as a function of the precession position.

[0047] Preferably, the correction system 9 comprises at least two measuring devices 4, preferably at least 4, which are angularly offset relative to each other to precisely measure the precession level NP. An offset of 90° is suitable, for example.

[0048] Still with reference to [Fig.4], the correction system 9 comprises at least one electromagnet 5 configured to generate a magnetic force F on the shaft 2 from a control order COM, in particular, a control current as will be presented later.

[0049] An electromagnet 5 advantageously makes it possible to generate a calibrated magnetic force on the magnetic element 7 of the shaft 2 in order to be able to modify its position and correct the precession movement P+. For the sake of clarity, only a few magnetic elements 7 are shown. Preferably, the magnetic elements 7 cover the periphery substantially uniformly and continuously so as to allow an electromagnet 5 to always be opposite a magnetic element 7.

[0050] Preferably, an electromagnet 5 generates a repulsion force with respect to the magnetic element 7 which aims to separate them from each other. It goes without saying, however, that an attraction force could also be suitable. It goes without saying that the same electromagnet 5 could act during a correction in repulsion then in traction depending on the need.

[0051] Preferably, as will be presented later, the correction system 9 comprises a plurality of electromagnets 5, each being configured to generate a magnetic force F on the shaft 2 from a control order COM. This makes it possible to generate a global magnetic force FGLOB on the shaft 2, the direction of which is precisely controlled to oppose the precession movement P+.

[0052] The electromagnets 5 are configured to be mounted on the fixed casing 1 peripherally to the shaft 2, preferably at the same radial distance from the shaft axis X. Mounting the electromagnets 5 on the fixed casing 1 makes it easier to integrate them into the turbomachine T.

[0053] Still with reference to [Fig.4], the correction system 9 comprises a computer 6 configured to determine the control order COM for each electromagnet 5 as a function of the precession level NP so as to generate a magnetic force F opposing the precession movement P+. The computer 6 is connected to each measuring device 4 and to each electromagnet 5.

[0054] Preferably, the computer 6 comprises a database (not shown) associating, for each precession level NP, a control order COM for each electromagnet 5. Preferably, each control order COM is in the form of a control current.

[0055] Preferably, the computer 6 is configured to successively activate each electromagnet 5 so as to generate a global rotating magnetic force FGLOB opposing the precession movement P+ over time. Thus, the global rotating magnetic force FGLOB makes it possible to dampen the precession movement P+ progressively, which is advantageous.

[0056] Furthermore, the computer 6 is configured to successively activate each electromagnet 5 according to a phase advance relative to the precession movement P + so as to limit the mechanical stresses applied to the shaft 2. Thus, when the precession position of the shaft 2 is known, the overall magnetic force FGLOB makes it possible to dampen the precession movement P + in a synchronized manner.

[0057] With reference to [Fig. 5], there is shown schematically an aircraft turbomachine T comprising a shaft 2 secured to a fan 20 and a plurality of movable compressor blades 21. The shaft 2 is a propulsion shaft. The movable compressor blades 21 are positioned radially outwardly relative to the shaft 2. The aircraft turbomachine T also comprises blades of rectifier 11 integral with the fixed casing 1 to straighten the air flow accelerated by the mobile compressor blades 21.

[0058] In this first embodiment, with reference to [Fig.5], the correction system 9 is positioned radially between the shaft 2 and the movable compressor blades 21.

[0059] In this example, with reference to [Fig. 6], the correction system 9 comprises four measuring devices 4a-4d which are spaced apart by 90°. In this example, each measuring device 4a-4d is in the form of a measuring sensor mounted on the fixed casing 1 peripherally to the shaft 2, in particular, at the same radial distance from the shaft axis X. In this example, the measuring devices 4a-4d are mounted on a support part 50 secured to the fixed casing 1.

[0060] In this example, the shaft 2 comprises a plurality of moving targets 42 secured to the shaft 2 configured to interact with the measuring devices 4a-4d to precisely determine the precession level NP, in particular, optically, inductively or capacitively. In this example, as many moving targets 42 are shown as there are measuring devices 4a-4d but it goes without saying that there could be more. As illustrated in [Fig. 6], four moving targets 42 are spaced apart by 90°. In this example, the moving targets 42 are mounted on a support part 70 secured to the shaft 2. The use of support parts 50, 70 allows precise positioning of the measuring devices 4a-4d and the moving targets 42 while taking into account the architecture of the turbomachine T.

[0061] Still with reference to [Fig.6], in this example, the correction system 9 comprises four electromagnets 5a-5d which are spaced apart by 90°, that is to say, two pairs of diametrically opposed electromagnets in order to act precisely on the position of the shaft 2 according to two perpendicular alignment directions (a vertical direction and a horizontal direction in this example). It goes without saying that the number of electromagnets 5a-5d could be different.

[0062] In this first embodiment, with reference to [Fig. 6], each electromagnet 5a-5d is configured to generate a magnetic force Fa-Fd on the shaft 2 in a radial direction relative to the shaft axis X so as to achieve a “direct” correction of the precession movement P+. The forces are radial and directed towards the shaft axis X.

[0063] In [Fig.6], the measuring devices 4a-4d and the electromagnets 5a-5d are shown in the same plane transverse to the shaft axis X in order to enable the impact of the magnetic forces Fa-Fb of the electromagnets 5a-5d on the shaft 2 to be measured precisely. It nevertheless goes without saying that the measuring devices 4a-4d and the electromagnets 5a-5d could be in different transverse planes.

[0064] Preferably, the electromagnets 5a-5d are fixed to the support part 50 of the fixed casing 1. In this example, magnetic elements 7 are fixed to the support part 70 of the shaft 2 opposite the electromagnets 5a-5d. With reference to [Fig.6], the magnetic elements 7 are positioned radially internal to the electromagnets 5a-5d. Preferably, the support part 70 fixed to the shaft 2 is perforated to reduce its mass and allow the passage of services (electricity, oil pipe, etc.). The correction system 9 is thus easily integrated into the turbomachine T.

[0065] In this example, the shaft 2 rotates in the clockwise direction R+. In the absence of precession movement P+, with reference to [Fig.6], the computer 6 does not issue any control order COM to the electromagnets 5a-5d so as to generate an overall magnetic force FGLOB of zero value. Alternatively, the computer 6 issues an identical control order COM to each electromagnet 5a-5d so as to generate magnetic forces Fa-Fd of identical value in order to generate an overall magnetic force FGLOB of zero value. Thus, the shaft 2 is not moved magnetically in the absence of precession movement P+.

[0066] During operation of the turbomachine T, the measuring devices 4a-4d carry out distance measurements to determine the precession level NP of the shaft 2, in particular, by monitoring the eccentricity of the shaft 2, the direction of precession and the precession position via the measuring devices 4a-4d and the moving targets 42.

[0067] In this example, with reference to Figures 7 and 8, due to the vibrations, the shaft 2 has a precession movement P+. In this example, the precession level NP corresponds to a clockwise precession (direct precession P+) with a degree of precession which corresponds to the separation of the shaft 2 from the shaft axis X (eccentricity). Preferably, the step of determining the precession level NP of the shaft 2 is only implemented when the vibrations measured on the shaft 2 exceed a predetermined threshold. This makes it possible to avoid monitoring the precession level NP continuously.

[0068] With reference to [Fig.7], if the precession level NP exceeds a predetermined threshold, the electromagnets 5a-5d generate magnetic forces Fa-Fd on the magnetic elements 7 of the shaft 2. The magnetic forces Fa-Fd are a function of the precession level NP so as to generate an overall magnetic force FGLOB opposing the precession movement P+ of the shaft 2. In particular, an overall magnetic force FGLOB is applied which opposes a precession movement P+ in the clockwise direction with an amplitude which is a function of the eccentricity.

[0069] As an example, with reference to [Fig.7], at a first instant t1, the shaft 2 is offset relative to the shaft axis X and is located at 12 o'clock, i.e. close to the electromagnet 5a. Such a precession position is for example determined by the measuring devices 4a, 4d located near the electromagnet 5a. As the shaft 2 follows a clockwise precession movement P+, it will move at a second time t2 at 3h towards the electromagnet 5b. In other words, the shaft 2 will move to the right with reference to [Fig.7].

[0070] To take into account the precession level NP, the computer 6 of the correction system 9 determines a control order COM for the electromagnet 5b which generates a magnetic force Fb directed radially inwards, that is to say, towards the shaft axis X. The other electromagnets 5a, 5c, 5d do not receive a control order and this results in an overall magnetic force FGLOB which tends to move the shaft 2 to the left, that is to say, in a manner opposite to the precession movement P+. The precession movement P+ of the shaft 2 is damped.

[0071] Advantageously, a new overall magnetic force FGLOB is determined each time the shaft 2 passes in front of an electromagnet 5a-5d. For this purpose, with reference to [Fig.8], at the second instant t2, the shaft 2 is offset relative to the shaft axis X and is located at 3 o'clock, i.e. close to the electromagnet 5b. As the shaft 2 follows a clockwise precession movement, it will move at the third instant t3 at 6 o'clock towards the electromagnet 5c. In other words, the shaft 2 will move downwards.

[0072] To take into account the precession level NP, the computer 6 of the correction system 9 determines a control order COM for the electromagnet 5c which generates a magnetic force Fc directed radially inwards, that is to say, towards the shaft axis X. The other electromagnets 5a, 5b, 5d do not receive a control order and this results in an overall magnetic force FGLOB which tends to move the shaft 2 upwards, that is to say, in a manner opposite to the precession movement P +. The precession movement P + of the shaft 2 is damped.

[0073] Advantageously, each time the shaft 2 approaches an electromagnet 5a-5d, the precession movement P+ can be compensated.

[0074] Thus, in this example, the computer 6 is configured to successively activate each electromagnet 5a-5d so as to generate a global rotating magnetic force FGLOB opposing the precession movement P+ over time. Thus, the global rotating magnetic force FGLOB makes it possible to compensate for the precession movement P+ in a progressive and synchronized manner, which is advantageous. In this example, the global rotating magnetic force FGLOB follows the precession movement P+, that is to say, rotates in a clockwise direction.

[0075] Preferably, each electromagnet 5a-5d is activated with a phase advance relative to the precession position of the shaft 2 in order to dampen its precession movement P+ and limit the mechanical stresses applied to the shaft 2. Preferably, the phase advance corresponds to the angular spacing between two consecutive electromagnets 5a-5d. Preferably, the phase advance is determined as a function of the response time of the complete system, in particular, the displacement measurement time, the data processing time (acquisition, filtering, etc.), the information transmission time to the computer, the computer processing time, the command transmission time to the electromagnets 5, the electromagnet activation time, etc.

[0076] In this example, the correction system 9 is configured to control one electromagnet 5a-5d at a time but it goes without saying that several electromagnets 5a-5d could be controlled simultaneously to obtain the desired overall magnetic force FGLOB.

[0077] The precession level NP is preferably continuously monitored during the correction in order to dynamically adapt the control commands COM and the resulting overall magnetic force FGLOB. Preferably, as soon as the precession level NP is below a predetermined threshold, the correction is stopped. Preferably, a control loop is implemented to allow the correction to be adapted.

[0078] Preferably, the control commands COM are recorded as well as the associated rotation speeds of the shaft 2. This makes it possible to determine, at a given speed, whether the overall magnetic force FGLOB is consistent with past corrections. Advantageously, a malfunction of the turbomachine T can be determined if the overall magnetic force FGLOB is higher than anticipated. Advantageously, a state of wear of the turbomachine T can be estimated by knowing the overall magnetic force FGLOB, which makes it possible to carry out predictive maintenance operations.

[0079] A variant of the first embodiment is shown in Figures 9 and 10. For the sake of clarity and conciseness, the elements common to Figures 5 and 6 are not described again. In this variant, the magnetic elements 7 are positioned radially external to the electromagnets 5a-5d. Furthermore, the number of magnetic elements 7 is greater than the number of electromagnets 5 as illustrated in [Fig. 10]. In this embodiment, the magnetic elements 7 cover the periphery substantially uniformly so as to allow an electromagnet 5 to always be opposite a magnetic element 7. For the sake of conciseness, the moving targets 42 have not been shown.

[0080] It goes without saying that the number of magnetic elements 7 can also be greater than the number of electromagnets 5 when the magnetic elements 7 are positioned radially inside the electromagnets 5a-5d.

[0081] In a second embodiment, with reference to [Fig.l 1], each electromagnet 5a-5d is configured to generate a magnetic force Fa-Fd on the shaft 2 in a direction parallel to the shaft axis X. This advantageously makes it possible to generate a bending torque FLEX on the shaft 2 so as to carry out an “indirect” correction of the precession movement P+. Thus, advantageously, the flexibility of the shaft 2 is taken advantage of to correct its precession movement P+.

[0082] Preferably, the electromagnets 5a-5d are fixed to the fixed casing 1 via a support part 50 and the magnetic elements 7 are fixed to the shaft 2, opposite the electromagnets 5a-5d, via a support part 70, for example, a crown. In this example, with reference to [Fig. 12], the magnetic elements 7 are positioned upstream of the electromagnets 5a-5d. The support part 70 may be perforated to reduce its mass and allow the passage of services. The correction system 9 can thus be easily integrated into the turbomachine T.

[0083] Preferably, in both embodiments, the support parts 50, 70 have shapes adapted to the structure of the turbomachine T and are mounted at existing mounting interfaces.

[0084] With reference to [Fig. 12] representing the correction system 9 seen from downstream, four electromagnets 5a-5d are shown angularly offset by 90° to control an overall force FGLOB generating a bending moment FLEX on the shaft 2. In a manner similar to the first embodiment, measuring devices 4 (not shown) determine the precession level NP and the computer 6 (not shown) determines the magnetic forces Fa-Fd determining the bending moment FLEX as a function of said precession level NP. Such an embodiment is advantageous in terms of space requirement. Preferably, the correction system 9 is independent of the guide bearings of the shaft 2.

[0085] Thanks to the correction system 9 according to the invention, a precession movement of a shaft 2 can be measured and corrected dynamically and this, independently of its vibration mode. The service life and reliability of a shaft 2 are advantageously improved. The same applies to the fixed casing 1 which receives the vibrations. The invention is of significant interest for a shaft 2 secured to a fan 20 whose vibrations can present a nuisance for aircraft passengers.

Claims

Claims

1. Correction system (9) of a precession movement (P+) of a shaft (2) of a turbomachine (T) comprising a magnetic element (7), the shaft (2) being rotatably mounted along a shaft axis (X) in a fixed casing (1), the correction system (9) comprising: • a plurality of measuring devices (4a-4d) configured to be mounted on the fixed casing (1) peripherally to the shaft (2) to determine a precession level (NP) of the shaft (2) relative to the fixed casing (1) of the turbomachine (T), • a plurality of moving targets (42) configured to be mounted integrally on the shaft (2) and configured to interact with the measuring devices (4a-4d), • At least one electromagnet (5) configured to generate a magnetic force (F) on the magnetic element (7) of the shaft (2) from a control order (COM),and • At least one computer (6) configured to determine the control order (COM) as a function of the precession level (NP) so as to generate an overall magnetic force (FGLOB) opposing the precession movement (P+) of the shaft (2) to dampen it.,

2. Correction system (9) according to claim 1, comprising a plurality of electromagnets (5a-5d), each being configured to generate a magnetic force (Fa-Fd) on the shaft (2) from a control order (COM), the computer (6) being configured to determine a control order (COM) for each electromagnet (5a-5d) as a function of the precession level (NP) so as to generate a global magnetic force (FGLOB) opposing the precession movement (P+) of the shaft (2) to damp it.

3. Correction system according to claim 2, wherein the electromagnets (5a-5d) are configured to be mounted on the fixed casing (1) peripherally to the shaft (2), preferably at the same radial distance from the shaft axis (X).

4. Correction system (9) according to one of claims 2 to 3, wherein the electromagnets (5a-5d) comprise at least one pair of electromagnets (5a,5c;5b,5d) configured to be diametrically opposed relative to the shaft axis (X).

5. Correction system (9) according to one of claims 2 to 4, in which the computer (6) is configured to successively activate each electromagnet (5a-5d) so as to generate a global rotating magnetic force (FGLOB) opposing the precession movement (P+) over time.

6. Correction system (9) according to one of claims 2 to 5, in which the computer (6) is configured to successively activate each electromagnet (5a-5d) according to a phase advance relative to the precession movement (P+).

7. Correction system (9) according to one of claims 2 to 6, in which each electromagnet (5) is configured to generate a magnetic force (F) on the shaft (2) in a radial direction relative to the shaft axis (X).

8. Correction system (9) according to one of claims 2 to 6, in which each electromagnet (5) is configured to generate a magnetic force (F) on the shaft (2) in a direction parallel to the shaft axis (X).

9. Correction system (9) according to one of claims 1 to 8, in which the measuring devices (4a-4d) are mounted on the fixed casing (1) at the same radial distance from the shaft axis (X).

10. Aircraft turbomachine (T) comprising a fixed casing (1) and at least one shaft (2) rotatably mounted along a shaft axis (X) in the fixed casing (1), the shaft (2) comprising at least one magnetic element (7), the turbomachine comprising a correction system (9) according to one of claims 1 to 9 configured to generate a magnetic force (F) on the magnetic element (7) to oppose the precession movement (P+) of the shaft (2) so as to dampen it.

11. Aircraft turbomachine (T) according to claim 10 in which, the shaft (2) being integral with a fan (20) and a plurality of mobile compressor blades (21) positioned radially outwardly relative to the shaft (2), the correction system (9) is positioned radially between the shaft (2) and the mobile compressor blades (21).

12. Aircraft comprising a turbomachine according to one of claims 10 to 11.

13. Method for correcting a precession movement (P+) of a shaft (2) of an aircraft turbomachine (T) according to one of claims 10 to 11, the correction method comprising steps consisting of: • determining a precession level (NP) of the shaft (2) relative to the fixed casing (1) of the turbomachine (T), and • generating a magnetic force (F) on the magnetic element (7) of the shaft (2), by means of at least one electromagnet (5), which is a function of the precession level (NP) so as to generate a magnetic force (F) opposing the precession movement (P+) of the shaft (2) to damp it.

14. Correction method according to claim 13, comprising steps consisting of: • Recording the magnetic forces (F) generated over time and • estimating a state of wear of the turbomachine (T) from the magnetic forces (F) recorded over time.

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