BLOWER SECTION WITH DEFORMABLE SEAL

Abstract

A section of an aircraft turbomachine fan (100) comprising a fan (11) configured to be driven in rotation about an axis of rotation (X), a stator (17), and a casing extending circumferentially around the fan (11) and the stator (17), the casing comprising at least a first portion (201, 200), a second portion (200, 202), and a mounting ferrule (203), the first portion of the casing comprising a first flange (201a, 200b) having a first face, the second portion of the casing comprising a second flange (200a, 202b) having a second face extending opposite the first face of the first flange (201a, 200b), and the stator (17) comprising a heel (171) extending opposite the mounting ferrule (203), the fan section (100) being characterized in that it further comprises at least one joint (4) disposed between two parts comprising the first flange (201a,200b) and the second flange (200a,202b) and / or the heel (171) and the fixing ferrule (203), the seal (4) being made of a deformable material (40) such that, during a relative approach of the two parts, the seal (4) compresses to limit the transmission of movement between said parts. Figure for the abbreviation: Fig. 4,

Description

Title of the invention: BLOWER SECTION WITH DEFORMABLE SEAL technical field

[0001] This disclosure relates to the general field of aircraft propulsion systems, and in particular to the fan sections and nacelle assemblies of such propulsion systems. STATE OF THE ART

[0002] When a new propulsion system is developed, numerous tests must be carried out as part of a certification process to ensure its reliability even under critical conditions, and thus to comply with applicable regulations. In particular, the casing surrounding the turbojet engine must withstand high stresses, especially in terms of temperature, load, or impact.

[0003] During the propulsion system certification process, actual fan blade ejection tests (FBOs) are performed. These tests simulate a scenario in which a fan blade of the turbofan engine detaches or breaks in flight. The purpose of these tests is to assess the ability of the housing surrounding the fan, known as the "retention housing," to retain the detached blade, and thus to validate its design. This is necessary to prevent damage to the aircraft fuselage, which could have dramatic consequences for the safety of the crew and passengers, particularly if the detached blade were to strike the fuel-filled wing or the pressurized fuselage, or if the turbofan engine were to separate from the aircraft.

[0004] These actual tests are destructive and therefore very expensive. They can be supported by numerical simulations performed using a numerical model. If a good correlation exists between the numerical and experimental results, the number of actual tests can be reduced while optimizing a large number of parameters. The challenge of the design is to guarantee the integrity of the turbojet engine and therefore of the aircraft, while minimizing the mass of the turbojet engine and therefore fuel consumption.

[0005] Indeed, climate change is a major concern for many legislative and regulatory bodies worldwide, particularly in the aeronautical sector. Technological research efforts are being intensified to improve the environmental performance of aircraft, in all phases of design and development, to obtain propulsion systems that are less energy-intensive, more environmentally friendly, and whose integration and use in aviation civil aircraft have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0006] Furthermore, the design of the propulsion system must not only guarantee blade retention during ejection, but also ensure that it maintains sufficient performance after ejection to achieve a safe return to the ground. In particular, the impact of the detached blade on the retention casing can generate axial displacements resulting in compressive forces. These compressive forces are transmitted through the fan section and can reach the intermediate casing surrounding the turbomachine. They contribute to damaging the turbojet structure, notably by causing plastic deformation. During the return to the ground, the absence of the blade creates an imbalance that can then cause cracks that may propagate in these areas of weakened mechanical strength. It is therefore necessary to maintain the integrity of the turbojet casing after the fan blade detaches. Description of the invention

[0007] One purpose of the present disclosure is to propose a blower section having a structure more resistant to compressive forces that may occur during blower blade ejection, without significantly increasing the mass of the propulsion system.

[0008] This objective is achieved by an aircraft turbomachine fan section comprising a fan configured to be driven in rotation about an axis of rotation, a straightener and a casing extending circumferentially around the fan and the straightener, the casing comprising at least a first portion, a second portion and a fixing ferrule, the first portion of the casing comprising a first flange having a first face, the second portion of the casing comprising a second flange having a second face which extends opposite the first face of the first flange, and the straightener comprising a heel extending opposite the fixing ferrule,

[0009] the blower section being characterized in that it further comprises at least one seal disposed between two parts comprising the first flange and the second flange and / or the heel and the fixing ferrule, the seal being made of a deformable material so that, during a relative approach of the two parts, the seal compresses to limit a transmission of movement between said parts.

[0010] The joint of the proposed blower section is located at the interface between two parts and compensates for compressive forces by deforming during relative movement of one part with respect to the other, thus limiting the transmission of compressive forces within the blower section. The joint helps to attenuate the The system transmits compressive forces, not just tensile forces as with conventionally used, self-aligning struts. The deformation of the damping material in the seal attenuates the propagation of a shock wave during an impact caused by a blower blade detachment. This prevents the transmission of axial or radial displacement, which could damage the casing structure and reduce its mechanical strength. Consequently, the risk of subsequent cracking is reduced. Adding the seal does not significantly increase the mass of the blower section, unlike adding material to one of the two components.

[0011] The invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations:

[0012] - the first portion of the envelope comprises an air inlet sleeve and the second portion of the envelope includes a blower housing extending circumferentially around the blower;

[0013] - the casing further comprises an intermediate housing extending circumferentially around the rectifier, the blower housing comprising a third flange having a third face and the intermediate housing comprising a fourth flange having a fourth face configured to extend opposite the third face, the blower section comprising an additional seal disposed between the third flange and the fourth flange, the additional seal being made of a deformable material so that, during a relative approach of the blower housing and the intermediate housing, the additional seal is compressed to limit a transmission of motion between said housings;

[0014] - the first portion of the casing comprises a blower housing, and the second portion of the envelope includes an intermediate casing, the blower casing extending circumferentially around the blower and the intermediate casing extending circumferentially around the rectifier;

[0015] - the fixing ferrule is attached to the intermediate housing, the fixing ferrule being configured to be connected to a pylon;

[0016] - the seal is disposed between the first flange and the second flange, the first flange and the second flange being fixed together by a bolt passing through the joint;

[0017] - the heel comprises a first protruding portion and a second portion In protrusion, the fixing ferrule comprises a first fixing portion and a second fixing portion, the seal being disposed between the first protruding portion and the first fixing portion, the blower section comprising an additional seal disposed between the second protruding portion and the second fixing portion, the additional seal being made of a deformable material so that, during a relative rapprochement of the fixing ferrule and the heel, the additional seal compresses to limit the transmission of movement between the fixing ferrule and the heel,

[0018] the heel and the fixing ferrule can be fixed together at the first fixing portion by a bolt passing through the joint, and at the second fixing portion by an additional bolt passing through the additional joint;

[0019] - the deformable material comprises at least one of the following materials: a viscoelastic polymer, a polymethacrylic imide foam;

[0020] - the deformable material comprises a mesh structure, for example at negative Poisson's ratio; and / or

[0021] -the blower section further comprises a composite material comprising carbon fibers embedded in an organic matrix, the composite material surrounding the seal.

[0022] According to another aspect, an aircraft turbomachine is proposed comprising a fan section as described above. DESCRIPTION OF THE FIGURES

[0023] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0024] Fig. 1 schematically illustrates a propulsion system.

[0025] Fig. 2 is a cross-sectional view of a blower section.

[0026] Fig. 3a schematically represents a connection between two parts of the envelope according to a first embodiment, before displacement.

[0027] Fig. 3b schematically represents the connection between two parts of the envelope according to the first embodiment, after displacement.

[0028] Fig. 4 schematically represents a connection between two parts of the envelope according to a second embodiment.

[0029] Fig. 5 schematically represents a connection between the rectifier and the intermediate housing according to a third embodiment.

[0030] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0031] In this application, upstream and downstream are defined with respect to the normal flow direction of the gas through the turbojet engine. Furthermore, the longitudinal axis X is the axis of rotation of the turbomachine's fan. The axial or longitudinal direction corresponds to the direction of the X axis, and a radial direction is a direction perpendicular to and passing through this axis. Moreover, the direction circumferential (or lateral) corresponds to a direction perpendicular to the X axis and not passing through it.

[0032] Propulsion system

[0033] Fig. 1 schematically represents a section of an aircraft propulsion system or turbomachine, in a plane including the longitudinal axis X.

[0034] The propulsion system comprises a fan section 100 including a fan IL. The fan section 100 forms a thrust generator. The fan 11 comprises a rotor part having a plurality of fan blades, distributed radially around the longitudinal axis X, placed upstream of a stator part 17 comprising a plurality of rectifiers (or OGVs, an acronym for "Outlet Guide Varies"). The propulsion system also includes a power generator or primary body 10 whose role is to rotate the fan 11 around the longitudinal axis X so as to generate an airflow and thus thrust.

[0035] The primary body 10 comprises, from upstream to downstream in the direction of the gas flow, a compressor section 16, a combustion chamber 14 and a turbine section 15, which are housed in an engine casing 21. In operation, an airflow F entering the propulsion system is divided between a primary airflow A and a secondary airflow B, which circulate from upstream to downstream in the propulsion system.

[0036] The secondary airflow B (also called "bypass airflow") flows around the primary body 10. The secondary airflow B cools the periphery of the primary body 10 and is used to generate most of the thrust provided by the propulsion system.

[0037] The primary airflow A flows in a primary channel 13 inside the primary body 10, passing successively through the compressor section 16, the combustion chamber 14 where it is mixed with fuel to serve as an oxidizer, and the turbine section 15. The passage of the primary airflow A through the turbine section 15 receiving energy from the combustion chamber 14 causes the rotor of the turbine section 15 to rotate around an internal ferrule 18, which in turn drives the rotor of the compressor section 16 and the rotor part of the blower section 100 into rotation.

[0038] The propulsion system is enclosed and includes a casing or nacelle surrounding the fan section 100. The casing includes several portions or parts extending circumferentially around the longitudinal axis X, so as to delimit a secondary channel 12, allowing the flow of the bypass flow B. For example, the casing includes, from upstream to downstream in the direction of the airflow, an air inlet sleeve 201, a fan casing 200 and an intermediate casing 202.

[0039] The fan blades 11 and the OGVs 17 extend radially in the secondary flow 12. The OGVs 17 help to reduce turbulence in the secondary flow B and to stabilize the flow, in order to increase the thrust generated and thus improve the performance of the propulsion system.

[0040] The air inlet sleeve 201 extends upstream of the fan 11. It plays an aerodynamic role and is designed to capture and homogenize the incoming airflow F and direct it towards the propulsion system.

[0041] The blower housing 200, also called the "retention card", extends downstream of the air inlet sleeve 201, and surrounds the blower 11. It is designed to retain a blower blade in the event of blade stall or breakage.

[0042] The intermediate casing 202 extends downstream of the fan casing 200 and surrounds the turbomachine 10. It extends circumferentially around the stator part 17 of the fan section 100 and is configured to take forces from the propulsion system and transmit them to a structure on which the turbojet will be fixed, such as a pylon 30.

[0043] Blower section

[0044] With reference to [Fig. 2], the inlet sleeve 201 comprises a first flange 201a having a first face. The first flange 201a forms a protrusion extending radially outward from the longitudinal axis X. The blower housing 200 comprises a second flange 200a, also forming a protrusion extending radially outward from the longitudinal axis X. The first flange 201a has a lateral face extending opposite, i.e., facing, a lateral face of the second flange 200a. The first flange 201a is fixed to the second flange 200a by means of fastening means, for example, bolts distributed radially around the periphery of the blower housing 200.

[0045] Similarly, the blower housing 200 comprises a first flange 200b, one face of which extends opposite a face of a second flange 202b belonging to the intermediate housing 202. The blower housing 200 and the intermediate housing 202 are held fixedly together at their respective flanges by means of a bolt.

[0046] The casing includes a mounting ferrule 203 extending over the intermediate housing 202 opposite the stator blades 17. The mounting ferrule 203 performs both mechanical and aerodynamic functions. It provides a mechanical connection between the stator 17 and the pylon 30, through which the forces are transmitted. In the illustrated embodiment, the mounting ferrule 203 is attached to the intermediate housing 202 and held securely in place by bolts.

[0047] The straightener blades 17 each include a heel 171 extending opposite the fixing ferrule 203. Fixing means, typically bolts, allow the heel 171 and the fixing ferrule 203 to be fixed together.

[0048] In an alternative embodiment not shown, the mounting ferrule 203 comprises a monolithic ring with the intermediate housing, i.e., here it is formed as a single unit with the intermediate housing. The heel 171 of the rectifier 17 is thus directly fixed to the intermediate housing 202 at the level of the mounting ferrule 203.

[0049] The blower section 100 is distinguished by a seal 4 located between two parts. The two parts can be selected from the air inlet sleeve 201, the blower housing 200, and the intermediate housing 202. The blower section 100 may include a single seal 4, or it may include a seal 4 between several pairs or each possible pair of parts.

[0050] The seal 4 is made of a deformable material 40 such that, when the two parts are brought closer together, the seal 4 compresses to limit the transmission of energy and therefore of movement between the parts. For example, when a fan blade 11 detaches, the impact between the fan blade 11 and the casing can generate wave propagation in the casing, resulting in displacement along the longitudinal direction X. In particular, if the detached blade impacts the fan housing 200 or the air inlet sleeve 201, the axial displacement can propagate in the direction of the secondary airflow B towards the intermediate housing 202.A concentration of such axial displacements can take place at the interface between the blower housing 200 and the intermediate housing 202, i.e. at the flanges 200b,202b, or at the interface between the air inlet sleeve 201 and the blower housing 200, i.e. at the flanges 20la,200a. .

[0051] The deformation of the deformable material 40 allows to absorb Fonde at the interface between the air inlet sleeve 201 and the blower housing 200 and / or at the interface between the blower housing 200 and the intermediate housing 202, and thus to reduce or even prevent the transmission of axial displacement to the intermediate housing 202.

[0052] It is advantageous not to transmit axial compressional displacements to the intermediate housing 202. Indeed, the intermediate housing 202 generally comprises a metallic alloy, for example, aluminum- or titanium-based. The manufacturing methods of the metallic intermediate housing 202 can induce non-isotropic properties. The mechanical strength of the intermediate housing 202 is lower in the longitudinal direction X, and axial displacements can contribute to its failure mode, leading to plastic deformation that can result in the appearance of cracks and serious risks to the integrity of the propulsion system.

[0053] For example, the joint 4 can be dimensioned to absorb axial displacements between 1.0 cm and 1.6 cm, and the additional joint can be dimensioned to absorb axial displacements between 1.4 cm and 2.0 cm. During bench tests, it was measured that the axial displacement at the interface between the two parts could be between 0.6% and 0.8% relative to the diameter of the part concerned.

[0054] The blower section 100 may include the seal 4 between all or part of the two parts, i.e., around the entire circumference between the two parts, or over one or more parts of the circumference between the two parts. The seal 4 may be in the form of a circular ring extending around the entire periphery of the casing between the first flange 20a, 200b and the second flange 200a, 202b. The seal 4 may include the deformable material 40 along all or part of its length, i.e., the deformable material 40 may be arranged over all or part of the joint between the two parts.

[0055] The deformable material 40 can deform plastically or elastically. Preferably, the deformable material 40 is chosen to deform elastically during normal operation of the propulsion system, so as to withstand all static and vibrational loads, and to be capable of deforming sufficiently to dissipate energy in the event of extreme transient events such as the ejection of the fan blade. Alternatively, the deformable material 40 can deform plastically, like a fuse, under the effect of axial compression due to the impact of the fan blade on the casing (see [Fig. 3b]).

[0056] The deformable material 40 can be chosen from various materials. For example, the deformable material 40 can be a rubber, or more precisely a viscoelastic polymer, for example, a viscoelastic elastomer with high damping capacity such as SMACTANE®. The seal 4 made of viscoelastic polymer has suitable mechanical properties to dissipate loads due to axial compression displacements. The viscoelastic polymer can provide an elastic response and therefore not deform plastically as a result of impacts, dissipating a significant amount of energy. The connection between the two parts is therefore not degraded; that is, the functioning of the connection between the elements after the impact is not compromised. In the event of a larger displacement following an impact of the detached blade near the connection, for example, the elastic limit of the deformable material 40 may be exceeded.Plastic deformation of the seal 4 can occur concurrently with high energy dissipation, so that the integrity of the blower section parts is preserved.

[0057] According to another example, the deformable material 40 may comprise a polymethacrylic imide foam, typically marketed under the name Rohacell®. The seal 4 made of polymethacrylic imide foam has the advantage of having a low density, typically between 20 kg / m³ and 100 kg / m³. Thus, the presence of the seal 4 does not significantly negatively impact the total mass of the propulsion system. Furthermore, the polymethacrylic imide foam presents It possesses excellent mechanical properties, high resistance to elevated temperatures, and low thermal conductivity. It has higher moduli of elasticity and shear strength than other types of foam with the same density. Polymethacrylic imide foam can deform plastically due to the relative movement of two parts, which corresponds to the most efficient absorption mechanism.

[0058] According to another example, the deformable material comprises a lattice structure, that is, a spatially organized lattice structure. The lattice structure can be produced by 3D printing, for example, using powder bed fusion techniques. The lattice structure, that is, the size of the cells forming the lattice and the geometry of the cells corresponding to an elementary geometric pattern, can vary according to the desired mechanical properties of the joint 4. The cells constituting the lattice can undergo geometric deformations depending on their position in space. The lattice structure can be numerically optimized to have a low density and suitable mechanical properties. The lattice structure has open porosity with a high porosity ratio, typically greater than 90%.It can be a non-isotropic structure with a significantly reduced density compared to a conventional solid, homogeneous and isotropic structure. This allows for a reduction in the mass of the seal 4 while improving energy absorption and therefore impact resistance.

[0059] Depending on the material used to form the mesh structure, the deformation of the deformable material resulting from the impact of the blower blade ejection can be plastic or elastic. Preferably, the mesh structure has a negative Poisson's ratio. Such a structure is particularly well-suited for resisting impacts. Indeed, compression leads to an increase in the relative density of the structure, which allows for an increase in the Young's modulus of the deformable material 40 and therefore an increase in the stiffness of the joint 4.

[0060] Preferably, the deformable material 40 of the seal 4 is chosen so that the seal 4 does not cause galvanic corrosion at the contact point with the first or second flange. For example, the flange 200a, 200b of the blower housing 200 or the flange 202b of the intermediate housing 202 typically include glass fibers to prevent galvanic corrosion with the carbon fibers included in the housing structure.

[0061] The deformable material 40 preferably has a coefficient of friction greater than 0.1, so as to allow good friction resistance at the joint between the two parts. The presence of fastening means, typically fixing screws or bolts, between the flanges 200a and 201a or between the flanges 200b and 202b, ensures the static connection between the two parts of the blower section.

[0062] In one embodiment, the two parts correspond to the first flange 200b of the blower housing 200 and the second flange 202b of the intermediate housing 202 (see, for example, [Fig. 3a]). The first flange 200b and the second flange 202b are fastened together by a bolt 5 passing through the gasket 4.

[0063] In another embodiment, the two parts correspond to the first flange 201a of the air inlet sleeve 201 and the second flange 200a of the blower housing 200 (see, for example, [Fig. 4]). This also prevents the transmission of forces and therefore axial displacements between the air inlet sleeve 201 and the blower housing 200, for example, in a situation where a blower blade detaches and impacts the air inlet sleeve 201. The axial forces transmitted to the intermediate housing 202 will consequently also be reduced. More generally, in a situation where the blower blade would impact the blower housing 200, the presence of the seal 4 between the blower housing 200 and the air inlet sleeve 201 helps to avoid or mitigate the transmission of displacements which could seriously damage the air inlet sleeve 201.

[0064] In one embodiment, the blower section 100 includes the seal 4 at the interface between the air inlet sleeve 201 and the blower housing 200, and includes an additional seal at the interface between the blower housing 200 and the intermediate housing 202, more precisely between their respective flanges 200b and 202b. This reduces the transmission of axial forces and displacements at the interface between the different portions of the casing.

[0065] The additional seal may have the same physical characteristics as seal 4, or different physical properties. In particular, the deformable material of the additional seal may be identical to or different from the deformable material 40 of seal 4. The dimensioning of seal 4 and the additional seal can be carried out using numerical simulations. Such simulations make it possible to estimate the axial displacement that seal 4 or the additional seal may have to compensate for following a blower blade ejection.

[0066] Preferably, the blower section 100 further comprises a composite material 41 comprising carbon fibers embedded in an organic matrix. The composite material 41 surrounds the seal 4. For example, the seal 4 comprises a central portion made of the deformable material 40 and an outer portion made of the composite material 4L. The presence of the composite material 41 in contact with the flanges 201a, 200a prevents degradation of the electrical connection at the interface between the two parts (typically in the event of lightning), and also prevents degradation of the fire resistance of the propulsion system.

[0067] The organic material can be an epoxy-type resin. Such a composite material 41 is known for its high strength, rigidity, and lightness. Thus, the thickness of the The density of the composite material 41 is less than that of the deformable material 40, so as to allow the absorption of axial compressive forces. The composite material 41 comprises, for example, 3 to 5 laminated plies.

[0068] The assembly between the deformable material 40 and the composite material 41 can be achieved by draping with layers of organic matrix composite (OMC). The central portion, typically annular, can be produced beforehand, before being placed in a mold with the layers (or pre-impregnated material). After curing in an autoclave at high pressure and high temperature, the pre-impregnated material crosslinks and hardens, thus forming a solid assembly.

[0069] The seal 4 described above can, alternatively or in combination, be arranged between the fixing ferrule 203 and the heel 171.

[0070] In another embodiment, the heel 171 comprises a first protruding portion 171a and a second protruding portion 171b (see [Fig. 5]). The retaining collar 203 comprises a first retaining portion 203a and a second retaining portion 203b, each retaining portion of the retaining collar 203 being arranged opposite a corresponding protruding portion of the heel 171. The gasket 4a is disposed between the first protruding portion 171a and the first retaining portion 203a, and the additional gasket 4b is disposed between the second protruding portion 171b and the second retaining portion 203b.

[0071] The seal 4a and the additional seal 4b are made of a deformable material so that, when the fixing ferrule 203 and the heel 171 are brought together, they compress to limit the transmission of movement between the fixing ferrule 203 and the heel 171. The two seals 4a, 4b may be identical or have different mechanical properties, according to the different embodiments described above.

[0072] The heel 171 and the fixing ferrule 203 are fixed together at the first fixing portion 203a by a bolt 5a passing through the seal 4a, and at the second fixing portion 203b by another bolt 5b passing through the additional seal 4b. The fixing ferrule 203 is attached to the intermediate housing 202, and connected to the pylon 30 by means of a fixing means 5c.

[0073] The present invention is not limited to the illustrated embodiments. In particular, the number of seals 4 and their arrangement may differ. For example, the propulsion system may include an air inlet sleeve 201 integral with the blower housing 200. Similarly, the connection between the mounting ferrule 203 and the heel 171, or between the pylon 30 and the casing, is not limited to the embodiment of [Fig. 5].

[0074] According to another aspect of the invention, an aircraft turbomachine is proposed comprising the fan section 100 as described above.

Claims

Demands

1. A section of an aircraft turbomachine fan (100) comprising a fan (11) configured to be driven in rotation about an axis of rotation (X), a stator (17), and a casing extending circumferentially around the fan (11) and the stator (17), the casing comprising at least a first portion (201, 200), a second portion (200, 202), and a mounting ferrule (203), the first portion of the casing comprising a first flange (201a, 200b) having a first face, the second portion of the casing comprising a second flange (200a, 202b) having a second face extending opposite the first face of the first flange (201a, 200b), and the stator (17) comprising a heel (171) extending opposite the mounting ferrule (203), the section of blower (100) being characterized in that it further comprises at least one seal (4) disposed between two parts comprising the first flange (20la,200b) and the second flange (200a, 202b) and / or the heel (171) and the fixing ferrule (203), the seal (4) being made of a deformable material (40) so that, during a relative approach of the two parts, the seal (4) compresses to limit the transmission of movement between said parts.

2. Blower section according to claim 1, wherein the first portion of the envelope comprises an air inlet sleeve (201) and the second portion of the envelope comprises a blower housing (200) extending circumferentially around the blower (11).

3. A blower section according to claim 2, wherein the housing further comprises an intermediate casing (202) extending circumferentially around the rectifier (17), the blower casing (200) comprising a third flange having a third face and the intermediate casing (202) comprising a fourth flange having a fourth face configured to extend opposite the third face, the blower section (100) comprising an additional seal disposed between the third flange and the fourth flange, the additional seal being made in a deformable material such that, during a relative approach of the blower housing (200) and the intermediate housing (202), the additional seal is compressed to limit a transmission of movement between said housings.

4. Blower section according to claim 1, wherein the first portion of the envelope comprises a blower housing (200), and the second portion of the envelope comprises an intermediate housing (202), the blower housing (200) extending circumferentially around the blower (11) and the intermediate housing (202) extending circumferentially around the rectifier (17).

5. Blower section according to any one of claims 3 and 4, wherein the fixing ferrule (203) is attached to the intermediate casing (202), the fixing ferrule (203) being configured to be connected to a pylon (30).

6. Blower section according to any one of claims 1 to 5, wherein the joint (4) is disposed between the first flange (20la,200b) and the second flange (200a,202b), the first flange (20la,200b) and the second flange (200a,202b) being fixed together by a bolt (5) passing through the joint (4).

7. A blower section according to any one of claims 1 to 5, wherein the heel (171) comprises a first protruding portion (171a) and a second protruding portion (171b), the retaining ring (203) comprises a first retaining portion (203a) and a second retaining portion (203b), the seal (4a) being disposed between the first protruding portion (171a) and the first retaining portion (203a), the blower section (100) comprising an additional seal (4b) disposed between the second protruding portion (171b) and the second retaining portion (203b), the additional seal (4b) being made of a deformable material such that, during relative rapprochement of the retaining ring (203) and the heel (171), the additional seal (4b) compresses to limit the transmission of motion between the retaining ring and the heel. (203) and the heel (171),the heel (171) and the fixing ferrule (203) can be fixed together at the first fixing portion (203a) by a bolt (5a) passing through the joint (4a), and at the second portion, fixing (203b) by an additional bolt (5b) passing through the additional joint (4b).

8. Blower section according to any one of claims 1 to 7, wherein the deformable material (40) comprises at least one of the following materials: a viscoelastic polymer, a polymethacrylic imide foam.

9. Blower section according to any one of claims 1 to 8, wherein the deformable material (40) comprises a mesh structure that may have a negative Poisson's ratio.

10. Blower section according to any one of claims 1 to 9, further comprising a composite material (41) comprising carbon fibers embedded in an organic matrix, the composite material (41) surrounding the joint (4).

11. Aircraft turbomachine comprising a fan section (100) according to any one of claims 1 to 10.