EP4065284A1

EP4065284A1 - Debris detection system

Info

Publication number: EP4065284A1
Application number: EP20803208.6A
Authority: EP
Inventors: Nicolas Oscar Louis Ghislain RAIMARCKERS; Cédric Louis Marie Ghislain FRIPPIAT; Aurélien Guy Edmond Raoul MEUNIER; Frédéric Vallino
Original assignee: Safran Aero Boosters SA
Current assignee: Safran Aero Boosters SA
Priority date: 2019-11-29
Filing date: 2020-11-12
Publication date: 2022-10-05
Also published as: WO2021104892A1

Abstract

System (45) for detecting ferromagnetic debris in an oil stream (F1, F2), the system comprising a passage (50) through which the stream (F1, F2) is intended to flow and a module (60) for detecting the ferromagnetic debris present in the stream (F1, F2), the detection module (60) comprising: a permanent magnet (66); and a coil (72) suitable for detecting the magnetic field (68) generated by the magnet; characterised in that the detection module (60) is arranged in the passage (50) and the detection module (60) further comprises a casing (62) which is sealed off from the stream (F1, F2) and in which the magnet (66) and the coil (72) are confined.

Description

DEBRIS DETECTION SYSTEM

Technical area

The invention relates to the monitoring of lubricated mechanical parts in a turbomachine. More specifically, the invention relates to the detection of ferromagnetic debris in the oil of a turbomachine. The invention also relates to a turbomachine, in particular an airplane turbojet or an aircraft turboprop.

Prior art

The presence of metallic debris in the oil of a lubrication system indicates the wear of the moving parts of a turbomachine. Thus, by analyzing the amount and size of metallic debris circulating in the oil, it is possible to estimate the health of the engine. In particular, a sharp increase in the number of debris detected can mean that a bearing or gear is wearing prematurely. Therefore, maintenance must be planned in order to avoid mechanical breakdown or breakage.

Document EP 3 363 518 A1 discloses an electrical detection system for the presence of ferrous particles in a fluid. This system has both a magnet and an electric coil. In operation, ferrous particles are attracted to the magnet and electromagnetic field disturbances are measured to infer the presence of debris. To prevent debris from accumulating on the magnet, this system is equipped with magnet protection screens. The strainers can also filter debris of given dimensions so that they are not counted by the detector.

This system has a weakness because it can generate pressure drops, negligible for high pressures and flow rates, but which can alter the fluid flow for low pressure flows.

Summary of the invention

Technical problem

The invention aims to solve at least one of the problems posed by the prior art. More specifically, the invention aims to provide a debris detection system with lower pressure drops.

Technical solution The subject of the invention is a system for detecting ferromagnetic debris in an oil flow of a turbomachine, the system comprising a passage intended to be traversed by the flow and a module for detecting the ferromagnetic debris present in the flow, the detection module comprising: a permanent magnet; and a coil capable of detecting the magnetic field generated by the magnet; remarkable in that the detection module is arranged in the passage and the detection module further comprises a flow-tight envelope in which the magnet and the coil are confined. The envelope may include a cavity in which the magnet and the coil are arranged. The coil can alternatively be embedded in the casing and only the magnet is included in the cavity delimited by the casing.

It is understood that the module may include signal processing electronics, integrated into the enclosure, or remote and connected wired or wireless to the module. The signal is processed in particular to detect variations in the magnetic field perceived by the coil.

By "passage" is meant a volume of the space traversed by the fluid, which may be delimited by a wall or several walls allowing a fluid to flow in at least one direction.

Providing an envelope for the detector elements means that the flow only encounters one element instead of several, resulting in less pressure drop.

According to advantageous embodiments of the invention, the system may include one or more of the following characteristics, taken in isolation or in any technically possible combination:

- the system includes a strainer with a mesh describing a cylinder or a portion of a cylinder and the module is integrated into the strainer, preferably the module is arranged along the axis of the cylinder or the portion of the cylinder. This integration of detection in the strainer makes it possible both to limit pressure drops and to limit the size of the entire device;

- the strainer is made of non-magnetic material. Its influence on the measurements can therefore be limited;

- the strainer has a base and the casing is welded or crimped to the base of the strainer. This type of assembly ensures the tightness of the enclosure, otherwise imprecise measurement or additional pressure drops would occur;

the module comprises a magnetic bar in contact with the magnet and around which the coil is wound; - the magnetic bar is a first magnetic bar, and the module comprises a second coil arranged around a second magnetic bar, preferably coaxial with the first bar, the second bar being separated from the first bar by the magnet and / or by a separator made of polymer material, electromagnetically insulating the first bar from the second bar. This subdivision of the module makes it possible to measure the particles at different locations in the flow, for example for redundant measurements reinforcing the validity of the measurements, or for measurements in different independent portions of the flow;

- The bar or bars is / are cylindrical and are positioned coaxially with the casing by one or more ring-shaped spacers. It is indeed important, especially during aircraft movements, to ensure that the bar does not move within the envelope. As an alternative to spacers, a potting (glue) can seal the position of the bar;

- the passage comprises at least two channels allowing an independent flow of the oil flow in the at least two channels, and the envelope extends in the at least two channels to detect the debris present in the oil passing through each of the channels , the module comprising as many coils as there are channels. This allows the detection of debris independently in multiple oil circuits without requiring multiple detection modules. One circuit can for example lubricate a bearing of the turbojet engine while another circuit communicates with a heat exchanger;

- The module includes an equal number of magnets and coils, one coil and one magnet being provided per channel through which the casing passes. This allows completely independent measurements. Alternatively, a magnet can be common to two contiguous passages to minimize the weight and the complexity of the module;

- the passage comprises at least two contiguous channels and separated from one another by a wall, the wall having an orifice which is crossed by the casing and possibly by a strainer, the magnet being positioned in line with this orifice. Thus, the magnet attracts debris towards the wall and the respective coils in the channels are remote from the wall;

- A seal is arranged between the casing and the wall and / or between the casing and the strainer, and / or between the strainer and the wall. This makes it possible to ensure the tightness of the flows between the two contiguous channels;

- The casing comprises two cylindrical portions of different diameters, the portion of larger diameter receiving the magnet and preferably being embedded in a wall of the passage or in the base of the strainer. This design maximizes the ability of the magnet to attract particles without requiring the presence of an unnecessarily large envelope in the oil flow;

- the magnet and / or the separator has / have a groove accommodating electric cables connected to the coil (s). The passage of cables is an additional difficulty of the confined space of the enclosure. One or more longitudinal grooves along the axis of the casing allows the passage of cables without affecting the quality of detection;

- the bar has a distal end located approximately in the center of the passage or in the center of one of the channels. The end of the bar is the place that attracts the most particles and to increase the probability of picking up all particles suspended in the oil, this end can be located between ¼ and ¾ of the passage;

- The passage comprises an elbow in which the module is arranged. The flow is therefore naturally directed to meet the modulus and the ferromagnetic particles are directed by centrifugal force to the outside of the bend where the modulus may be located. This increases the chances that the module will "see" the particles passing by. Particle counting is therefore made more precise;

- the casing protrudes into the passage by a length which is adjustable and / or the casing is oriented transversely to the main direction of flow of the flow at an angle which is adjustable. Depending on the speed of the flow, the nature of the flow, or the geometry of the passage, this adjustment makes it possible to obtain the most precise detection possible;

- the magnet is not placed in the passage or in one of the passage channels. The magnet can thus be embedded in a wall of the passage or channels;

- the coil is an insert in the manufacture of the envelope. This design allows a module which is particularly compact;

- the magnet is cylindrical in shape with two poles separated by a plane which is neither parallel to the axis of the cylinder, nor which is perpendicular thereto. In other words, the north-south axis of the magnet is inclined with respect to the axis defined by the cylindrical shape of the magnet, this inclination excluding perpendicularity. This type of magnet allows a good compromise between the attraction of the particles and their detection by the coil. Alternatively, the north-south axis of the magnet coincides with the axis defined by the cylindrical shape of the magnet. The subject of the invention is also an aircraft turbojet comprising a lubrication unit made of a single-piece body receiving several pumps and filters, several oil inlets and outlets, and a debris detection system, remarkable in that the Debris detection system is according to one of the above embodiments and the debris detection system is disposed in an oil inlet upstream of the pumps and filters. In the present application, the term “filter” designates filtration elements arranged downstream of the pumps to protect the drive components (injectors, enclosures) with filtration of the order of 10 to 150 μm. The filtration of particles upstream of the pumps is carried out by a "strainer" having a "mesh" preventing the largest particles (greater than a size of the order of 500 to 1000 μm) from damaging the particles. pumps.

Benefits provided

The envelope limits the pressure drops of the flow, which only encounters a single, sealed element, instead of several successive elements as is the case in some existing systems.

In addition, the arrangement of an envelope in the heart of the flow makes it possible to accurately measure the quantity of ferromagnetic debris circulating in the oil flow because a detection in the center of the flow reaches more potential particles than a detection on a wall of a passage.

When the envelope extends through several channels, it is possible to independently detect the presence of debris in each of the channels and to precisely infer the mechanical elements that may be the source of this debris. The size and weight of the system of the present invention are also improved.

Brief description of the drawings

Figure 1 shows an axial turbomachine according to the invention;

Figure 2 illustrates an isometric view of the body of a lubrication unit;

Figures 3A and 3B show two examples of debris detection systems according to the invention;

Figures 4A to 4D show four exemplary embodiments of the debris detection module;

Figures 5 and 6 show a module integrated into a strainer;

Figures 7 to 9 show three examples of integration of the module in a dual-channel or triple-channel fluid passage;

Figures 10A-10C show embodiments of the magnet.

Description of the embodiments

In the description which follows, the term “magnet” refers to a permanent magnet. The longitudinal or axial direction is considered according to the South-North orientation of the magnet. The flow of flux in the passage at the level of the magnet proceeds according to a main direction of flow which is transverse (perpendicular or simply secant) to the longitudinal direction. Upstream and downstream are understood in relation to the direction of flow of the flow.

FIG. 1 shows in a simplified manner an axial turbomachine. In this specific case, it is a double-flow turbojet. The turbojet 2 comprises a first level of compression, called low-pressure compressor 4, a second level of compression, called high-pressure compressor 6, a combustion chamber 8 and one or more levels of turbines 10. In operation, the mechanical power of the turbines 10 is transmitted via shafts to the rotor 12 and sets in motion the two compressors 4 and 6. The latter comprise several rows of rotor blades associated with rows of stator blades. The rotation of the rotor around its axis of rotation 14 thus makes it possible to generate a flow of air and to gradually compress the latter until it enters the combustion chamber 8.

A fan 16 is coupled to the rotor 12 and generates an air flow which is divided into a primary flow 18 passing through the aforementioned different levels of the turbomachine, and a secondary flow 20 passing through an annular duct. Reduction means 22 can reduce the speed of rotation of the fan 16 and / or of the low pressure compressor 4 relative to the speed of the associated turbine 10.

The rotor 12 comprises several coaxial shafts 24 supported by bearings 26. The cooling and / or the lubrication of the bearings 26 and of the optional reduction gear 22 are provided by a lubrication circuit 28. The lubrication circuit 28 can incidentally supply actuators. such as jacks (not shown). The lubrication circuit 28 may also include a heat exchanger 30 for cooling the oil, the temperature of which may exceed 200 ° C. These temperatures amplify the aggressiveness of the corrosive oil towards gaskets and polymer parts in general. The lubrication circuit 28 may comprise oil recovery pipes 32 collecting the oil in the lubricating chambers of the bearings 26 and conveying it into the reservoir 34. It may also include a pipe 32 for recovering the lubricating oil. the reducer 22 and returning this oil to the reservoir 34.

In order to force the circulation of the oil during its recovery, the lubrication circuit 28 may include a lubrication group 36.

The lubrication group 36 can be directly mounted on an accessory box of the turbojet 2. The lubrication group 36 is a unit made up of a one-piece body which accommodates several hydraulic functions such as, for example, several pumps and filters. It pressurizes the oil taken from the tank and distributes it in the engine components to be lubricated before reconditioning it (cooling and filtering) and returning it to the reservoir 34.

FIG. 2 illustrates an example in isometric view of a body 38 of a lubrication group 36. The body can be manufactured by additive manufacturing and be of particularly complex shape. The body 38 can be in one piece. It may include several oil inlets 40, 42 for sucking the oil from the reservoir or from the components of the turbomachine and several oil outlets 41, 43 for discharging the oil towards the reservoir or towards the components of the turbomachine. . Respective passages connect the inputs to the outputs. Some passages can be completely independent of other passages. Group 36 can be equipped with many functions and contain several pumps and filters. According to the invention, the group 36 may also contain a ferromagnetic debris detection system.

Figures 3A and 3B show schematically two versions of a debris detection system 45 according to the invention. In FIG. 3A, a rectilinear passage 50, for example in the vicinity of the entrance 42, accommodates a detection module 60. The latter projects into the passage 50 and the length from which it protrudes can be adjustable.

In FIG. 3B, an angled passage 50, for example in the vicinity of the entrance 40, accommodates a detection module 60. The latter can have an orientation with respect to the flow which is adjustable and / or a protruding length in the passage. 50 which is adjustable.

The passage 50 is traversed by a flow of oil F. The orientation and the length with which the module protrudes into the passage are adjusted mechanically by appropriate means (electric motor, screw, piston, etc.).

Each detection system 45 makes it possible to detect the presence and / or the circulation of ferromagnetic debris, or ferromagnetic particles, contained in the oil. This debris can in particular result from wear of a bearing or of a gear tooth forming the reducer 22.

Each module 60 can be connected to a signal processing unit (not shown). Therefore, the processing unit manages to identify the presence of debris in each pipe. The debris can be between 50 µm and 1000 µm, or between 150 µm and 750 µm in size.

FIGS. 4A to 4C show three examples of detection module 60. The module 60 comprises an envelope 62 which may be cylindrical and of axis A. The envelope 62 defines a cavity 64 which accommodates various components. The casing 62 is sealed and can be placed in the flow F without allowing oil to penetrate inside the cavity 64. The casing can be made of polymer material 1 mm thick (+/- 0.2 mm ). Alternatively, the casing can be thinner, made of a titanium alloy or be made of stainless steel, and have a thickness of approximately 0.1 mm (+/- 0.02 mm). The envelope is made of a non-magnetic material.

The module is intended to measure the magnetic field in the flux F and more particularly the variations of the magnetic field resulting from the passage or the presence of ferromagnetic debris.

For this purpose, the cavity 64 contains a permanent magnet 66. This magnet can be of the SmCo (Samarium-Cobalt) type and have stable magnetic properties from -54 ° C to 200 ° C. The south-north direction of magnet 66 is along the A axis. A magnetic field 68 is shown schematically in broken lines.

The cavity 64 also includes one or more coils 70, 72. Each coil 70, 72 can be made of a winding of several hundred turns of fine wire (for example about 0.01 mm) with local splices to ensure the strength of the wire. . The magnet 66 has the dual role of attracting the ferromagnetic debris found in the oil flow and of generating a magnetic field detectable by the coil 72. The coil 72, passive, makes it possible to measure the variations of the magnetic field 68 created. by the magnet. The coil 70 can be a "Built-in test" coil making it possible to generate a magnetic field and to check the response of the coil 72, for example before starting up a turbojet. The coil 70 is therefore not essential to the operation of the detection module but allows an integrated verification of its correct operation.

In general, the detection technology used is similar, for example, to the technology disclosed in document WO 2017/157855 A1 or in document EP 3 363 518 A1.

Thus, when a ferromagnetic particle arrives near the envelope, it modifies the magnetic field 68 and creates discontinuities in the intensity of the passive coil 72. When the signal comprises a peak which exceeds a given predefined threshold, the modulus 60 recognizes that a ferromagnetic particle has passed.

FIG. 4B shows a second exemplary embodiment of the module 60. In this example, the casing 62 comprises two portions 62.1, 62.2, including a portion 62.2 of greater diameter than the other portion 62.1. This projection 62.2 facilitates the mounting of the module 60 on a wall of the passage 50.

In the example of FIG. 4B, the detection module 60 comprises a magnetic element 74 in the form of a magnetic bar (for example M50). This magnetic element 74 can pass through the coil (s) 70, 72. It is in contact with the magnet 66 at its proximal end 74.1. The bar 74 thus behaves like the extension of the magnet 66. The magnetic field is maximum at the distal end. 74.2 of the bar 74. The bar 74 preferably has a smaller diameter than the magnet 66. The magnet 66, the bar 74 and the coil 72 are sized to attract and / or detect particles of defined dimensions. A magnet 66 that is too powerful can attract many particles but will generate a magnetic field that is too strong and the variations of which will be difficult to detect by the coil 72. A balance is therefore found.

FIG. 4C illustrates a third exemplary embodiment of the module 60. This example is substantially similar to that of FIG. 4B. Annular spacers 76 are provided to hold the bar in position in the casing 62. In this example, the magnet may not be confined to the projection 62.2.

Figure 4D shows an additional example. In this example, the coil or coils 70, 72 are embedded in the polymer casing, such as manufacturing inserts. To do this, a copper wire is wound and the polymer is injected or molded around the wire.

Figure 5 shows a first implementation of the module 60 in a strainer 80. The strainer includes a filter mesh 82 extending from a base 84 towards a ceiling 86. The module 60 can be welded to the base 84 of the strainer 80. Alternatively, a press fit or crimp can be used. The mesh 82 may take the form of a cylinder or a portion of a cylinder, for example extending over 180 ° around the axis A. The mesh 82 and the module 60 are advantageously coaxial. Figure 6 illustrates these aspects in a sectional sectional view along axis VI: VI of Figure 5.

The mesh size of the mesh 82 may be greater than or equal to 1000 μm, or to 750 μm, in particular in order to protect the pumps downstream of the strainer from the largest debris.

The strainer 80 can be made entirely, including with its mesh 82, by additive manufacturing.

Figure 6 also shows the order of magnitude of the ratio between the diameter of the module 60 and that of the mesh 82 which can be of the order of 3.

The assembly of Figure 5 formed by the module 60 and the strainer 80 can be inserted into an oil passage 50.

The strainer 80 can also be multi-stage, with an intermediate wall between the base 84 and the ceiling 86. FIG. 7 illustrates an implementation of a module 60 with such a two-stage strainer 80 in a passage comprising two channels 52, 54 in which circulate two independent oil flows F1, F2. In this example, the module 60 comprises two magnets 66, two magnetic bars 74 and two pairs of coils 70, 72. A block 78 of magnetic insulating material, for example a polymer, isolates the magnetic field of one magnet from the magnetic field of the other magnet, so that the coils 72 measure a magnetic field coming from their respective magnet 66 without interference from the other magnet 66. Thus, a single module 60 makes it possible to detect the ferromagnetic particles of two independent flows F1, F2 and therefore to deduce therefrom in a distinctive manner the member of the turbojet which emits ferromagnetic particles. The magnets 66, the bars 74 and the coils 72 dedicated to the two channels 52, 54 can be different. Indeed, it may be advantageous to provide particle detection thresholds which are different according to the organs which are respectively connected to each channel 52, 54. Alternatively, or in addition, the detection thresholds can be distinguished on the processing. signals from the two coils 72.

In this example, the strainer 80 comes flush with the walls 90 of the channels 52, 54. Seals 94 may be provided between the module and the intermediate wall 88 of the strainer 80, as well as between the strainer 80 and the walls. 90. An orifice 92 in the wall 90 is provided to receive the module 60 and the strainer 80.

This figure also illustrates an alternative mounting of the module 60 in the strainer, via the projection (62.2 in FIG. 4B). The module can be inserted axially against a seal 94.

On the right of Figure 7 are shown the magnets 66 in section. The magnets 66 have a longitudinal groove 66.1 (along the axis A) which allows the passage of the cables 72.1 of the coils 72. The upper magnet (in the direction of figure 7) can have a groove 66.1 and the magnet lower which must allow the passage of more numerous son may have two grooves 66.1.

Figure 8 illustrates an alternative to the system of Figure 7. In this case, a single magnet 66 generates a magnetic flux for the two channels 52, 54. The magnet can be confined to the intermediate wall 88.

This figure also illustrates the fact that the casing 62 of the module 60 can be cylindrical without a projection and be crimped or mounted tight in the base 84 of the strainer. FIG. 9 shows an example of module 60 allowing measurement in three contiguous channels 52, 54, 56 two by two. In this example, the strainer 80 which remains optional is not shown. Note that the strainer is not essential for the distinctive measurement of particles in multiple independent channels. The module 60 can be hybrid, that is to say present a magnet for two channels 52, 54 and a magnet for the third channel 56. Alternatively, three magnets can be provided, with three magnetic bars separated two by two from each other. an insulating block. The number of coils 72 for its part always remains equal to the number of channels 52, 54, 56.

Generally speaking, the distal end 74.2 of each bar will be located around the midpoint of the corresponding channel to attract and detect a maximum of particles. The corresponding detection coil 72 will also be placed in the vicinity of the midpoint of the channels. By "midpoint" is meant the middle of the section of the channel, located between ¼ and ¾ of the section of the channel.

Figures 10A to 10C show different magnets. The magnet of Figure 10A is the magnet known in the state of the art to have a strong power of attracting particles. This magnet generates a magnetic field whose field lines are perpendicular to the axis of the magnet. It is impossible to detect magnetic field variations with a coil coaxial with such a magnet.

The magnet used in the invention is therefore that of Figures 10B or 10C. In Figure 10B, the magnetic field is as drawn in Figure 4A. This magnet, on the other hand, has a lower power to attract particles.

The magnet in Figure 10C is a good compromise and has two poles separated by a plane which is inclined with respect to the axis of the cylindrical magnet. The plane P is neither perpendicular nor parallel to the axis of the magnet. This representation is schematic. The magnet can be made of smaller elementary magnets making it possible to obtain a magnet which schematically comprises two opposite poles along a section of a cylinder. Such a magnet not only attracts particles but also creates a magnetic field whose variations are detectable by a coil coaxial with the magnet. The angle between the plane P and the axis of the cylinder may preferably be between 60 ° and 80 °.

Those skilled in the art will understand that the technical details of each embodiment are applicable to the other embodiments. In particular, the assembly of the module in the strainer, the presence or not of a bar, of a projection, of a BIT coil, or the presence of a strainer are optional aspects and can be taken from a mode of achievement and applied to another.

Claims

1. System (45) for detecting ferromagnetic debris in an oil flow (F, F1, F2) of a turbomachine (2), the system comprising a passage (50) intended to be traversed by the flow (F, F1, F2) and a detection module (60) of the ferromagnetic debris present in the flow (F, F1, F2), the detection module (60) comprising:

- a permanent magnet (66); and

- a coil (72) capable of detecting the magnetic field (68) generated by the magnet; characterized in that the detection module (60) is arranged in the passage (50) and the detection module (60) further comprises a casing (62) sealed to the flow (F, F1, F2) in which are confined the magnet (66) and coil (72).

2. System (45) according to claim 1, characterized in that it comprises a strainer (80) with a mesh (82) describing a cylinder or a portion of a cylinder and the module (60) is integrated into the strainer (80). ), preferably the module (60) is arranged along the axis (A) of the cylinder or of the cylinder portion.

3. System (45) according to claim 2, characterized in that the strainer (80) is made of a non-magnetic material.

4. System (45) according to one of claims 2 or 3, characterized in that the strainer (80) comprises a base (84) and the casing (62) of the module (60) is welded or crimped to the base. (84) of the strainer (80).

5. System (45) according to one of claims 1 to 4, characterized in that the module (60) comprises a magnetic bar (74) in contact with the magnet (66) and around which the coil (72) is wound. ).

6. System (45) according to claim 5, characterized in that the magnetic bar (74) is a first magnetic bar, and in that the module (60) comprises a second coil (72) arranged around a second bar magnetic (74), preferably coaxial with the first bar (74), the second bar (74) being separated from the first bar (74) by the magnet (66) and / or by a separator (78) made of polymer material, electromagnetically insulating the first bar (74) of the second bar (74).

7. System (45) according to one of claims 5 or 6, characterized in that the bar (74) or the bars (74) is / are cylindrical and is / are positioned (s) coaxially with the casing (62 ) by one or more spacers (76) of annular shape.

8. System (45) according to one of claims 1 to 7, characterized in that the passage (50) comprises at least two channels (52, 54, 56) allowing flow of the oil flow (F, F 1 , F2) independently in the at least two channels (52, 54, 56), and the casing (62) extends into the at least two channels (52, 54, 56) to detect debris present in the oil traversing each of the channels (52, 54, 56), the module (60) comprising as many coils (72) as there are channels (52, 54, 56).

9. System (45) according to one of claims 1 to 8, characterized in that the passage (50) comprises at least two channels (52, 54, 56) contiguous and separated from one another by a wall. (90), the wall (90) having an orifice (92) which is crossed by the casing (62) and possibly by a strainer (80), the magnet (66) being positioned in line with this orifice ( 92).

10. System (45) according to claim 9, characterized in that a seal (94) is arranged between the casing (62) and the wall (90), and / or between the casing (62) and the strainer (80), and / or between the strainer (80) and the wall (90).

11. System (45) according to one of claims 1 to 10, characterized in that the casing (62) comprises two cylindrical portions (62.1, 62.2) of different diameters, the portion (62.2) of larger diameter receiving the 'magnet (66) and being preferably embedded in a wall (90) of the passage (50) or in the base (84) of the strainer (80).

12. System (45) according to one of claims 1 to 11, characterized in that the magnet (66) and / or the separator (78) has / have a groove (66.1) accommodating electric cables (72.1) connected. to the coil (s) (72).

13. System (45) according to one of the preceding claims in combination with one of claims 5 to 7, characterized in that the bar (74) has a distal end (74.2) located approximately at the center of the passage (50) or in the center of one of the channels (52, 54, 56).

14. System (45) according to one of claims 1 to 13, characterized in that the passage (50) comprises an elbow in which the module (60) is arranged.

15. System (45) according to one of claims 1 to 14, characterized in that the casing (62) projects into the passage (50) by a length which is adjustable and / or the casing (62). ) is oriented transversely to the main flow direction of the flow (F, F 1, F2) at an angle which is adjustable.

16. System (45) according to one of claims 1 to 15, characterized in that the coil (72) is an insert for manufacturing the casing (62).

17. System (45) according to one of claims 1 to 16, characterized in that the magnet (66) is cylindrical in shape with two poles (N, S) separated by a plane (P) which is neither parallel to the axis of the cylinder, nor which is perpendicular to it.

18. Aircraft turbojet (2) comprising a lubrication unit (36) made of a single-piece body (38) receiving several pumps and filters, several oil inlets and outlets (40-43), and a detection system. debris, characterized in that the debris detection system (45) is according to one of claims 1 to 17 and the debris detection system (45) is disposed in an oil inlet (40, 42) in upstream of pumps and filters.