Sealing gasket with a slippery, hydrophobic coating

Abstract

This sealing gasket (23), configured to be disposed between a first element (17) and a second element (11) of a propulsion unit in an assembled configuration, comprises a longitudinal sector (29) intended to be in contact with the second element (11), the longitudinal sector (29) being formed of a fluid-tight and fire-resistant and substantially elastic material, the sealing gasket comprising a coating of a sliding and hydrophobic material (31) covering the longitudinal sector (29). Figure for the abbreviation: Fig. 3

Description

Description Title of the invention: Sealing gasket comprising a coating slippery and hydrophobic technical field

[0001] = The present invention relates to a sealing gasket for a propulsion assembly, and more specifically a fire and fluid resistant seal for an assembly propulsive.

[0002] = The propulsion system can be, for example, a turbojet-type system and nacelle for aircraft propulsion.

[0003] — In general, the invention applies to any field requiring the implementation of in place of a fluid seal, the seal being likely to be significantly set in motion. Previous techniques

[0004] In the field of aircraft turbojet nacelles, various compartments are positioned close to one another, some of which are likely to include flammable liquids, and others that may be exposed to fire or sparks, the liquid must under no circumstances pass from one compartment to the other.

[0005] By way of example, a gondola 1 is shown in schematic cross-section in [Fig. 1]. of a turbojet engine.

[0006] — The nacelle 1 includes a thrust reverser 3 located downstream, as well as a motor 5 positioned in the center of the gondola on its longitudinal axis 7.

[0007] — Access to the engine 5 is via a first compartment 9, called compartment engine. Access to said first compartment 9 is gained in particular through the opening of a movable hood 11.

[0008] — The gondola also includes a second compartment 13 juxtaposed to the first compartment 9 and including inverter control equipment push 3.

[0009] = The first compartment 9 comprises pipes containing fluids in- flammable. During a pipe bursting incident, the fluids are released. in the first compartment 9 and are liable to ignite. The first com- compartment 9 and the equipment inside the first compartment 9 are also designed to withstand fire, the first compartment 9 including, for example Automatic fire extinguishers are used. The released fluids are also drained outside. by drainage holes, for example positioned in the movable hood 11.

[0010] — The second compartment 13 includes equipment that is not di- mentioned to withstand contact with the fluids of the first compartment 9, and further less to withstand a fire in said second compartment 13. A fluid and fire-resistant seal 15 is therefore placed between these two compartments 9 and 13, one end of the seal being in particular in contact with the movable cover 11 when it is closed. However, the movable hood 11, and more generally the whole of the nacelle 1, being subject to vibrations and movements, a coating of sliding material can be placed on the seal 15, thus allowing it to slide in contact with the movable hood 11, and therefore not to damage it at the risk of reducing the seal by creating leaks. Figure 2 schematically represents a sealing gasket 15 attached to a first element 17 and in contact with a second element 11, for example, the movable cover 11. The gasket separates, for example, a first compartment 9 from a second compartment 13. A sliding material coating 19 is applied to the gasket 15 to facilitate sliding contact between the gasket 15 and the second element 11. The material coating 19 is, for example, meta-aramid, more commonly known as Nomex®. However, in the event of a burst pipe or a leak from the engine, a portion of the material coating 19 may become saturated with fluids 21 from the first compartment 9. By capillary action, the fluids 21 are likely to move along the gasket 15 and into the second compartment 13. This is exacerbated by a pressure difference between the first compartment 9 and the second compartment 13.Consequently, the equipment in the second compartment 13 may be damaged by this infiltration of flammable fluid, or may find itself exposed to a fire risk in a non-fire zone. Description of the invention The present invention aims to overcome the aforementioned drawbacks and to provide a fire- and fluid-tight seal that also facilitates the sliding of said seal by preventing the passage of fluids by capillary action against the seal. The present invention relates to a sealing gasket configured to be placed between a first element and a second element of a propulsion assembly in an assembled configuration. The sealing gasket comprises a longitudinal sector intended to be in contact with the second element. This longitudinal sector is made of a fluid- and fire-tight, substantially elastic material and includes a coating of a sliding, hydrophobic material covering the longitudinal sector. Thus, the sealing gasket is watertight, in frictionless sliding contact with the second element, and prevents the passage of fluid by capillary action at the frictionless contact point. Advantageously, the material coating has a cor- wettability criterion responding to a contact angle greater than or equal to 90°. In one embodiment, the material coating comprises a carbon fiber impregnated with resin and / or silicone. Advantageously, the material coating includes a hydrophobic layer produced by graphene spraying. Advantageously, the waterproof material comprises an elastomer binder and a ceramic, glass, or carbon fabric reinforcement material. In some embodiments, the material coating is partially embedded in the waterproofing material or covers the waterproofing material. In one embodiment, the joint comprises an "omega" type cross-section including a first substantially flat part fixed to the first element and a second rounded part including the longitudinal sector. The present invention also relates to a propulsion assembly of an aircraft comprising a first compartment capable of being exposed to fire and a second compartment, the propulsion assembly comprising a sealing joint as defined above between the first compartment and the second compartment. The present invention also relates to an aircraft comprising a propulsion assembly as defined above and / or a joint as defined above. Brief description of the drawings Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which: [Fig.1] which has already been mentioned, is a schematic cross-sectional view of a nacelle of an aircraft propulsion assembly according to the state of the art; [Fig.2] which has already been mentioned, is a schematic cross-sectional view of a sealing joint according to the state of the art; [Fig.3] is a schematic cross-sectional view of a sealing gasket according to the invention; and [Fig.4] is a schematic cross-sectional view of a drop of liquid on a weakly wettable surface. Detailed description of at least one embodiment A sealing gasket 23 according to the invention has been schematically represented in [Fig.3]. The sealing gasket 23 is configured to be arranged between a first element 17 and a second element 11 in an assembled configuration. The sealing gasket 23, for example, has an elongated shape and comprises a cross-section of type "©" (omega) including a first substantially flat portion 25 fixed to the first element 17 and a second rounded portion 27, and more particularly substantially tubular with a longitudinal direction extending along the axis of this tube, and a transverse direction extending perpendicularly to the longitudinal direction. The first substantially flat portion 25 may include notches and / or deformations intrinsic to the first portion 25 and / or due to reliefs of the first element 17. The sealing gasket 23 can also have other shapes depending on its use. The first element 17 is for example a wall separating a first compartment 9 from a second compartment 13 and illustrated in [Fig.1]. Thus, for example, the first compartment 9 gives access to an engine and is accessible from the outside by a movable hood and the second compartment 13 which is juxtaposed to the first compartment includes a servo equipment for the thrust reverser of a nacelle of a turbojet engine. In particular, the sealing gasket 23 is fixed to the first element 17 and is intended to be positioned in contact with a second element 11 in the assembled configuration. The second element 11 is, for example, the movable cover 11 mentioned in Figures 1 and 2. The sealing gasket 23 provides a hermetic seal between the first compartment 9 and the second compartment 13. Specifically, the sealing gasket 23 is fluid-tight and fire-resistant. The sealing gasket is, for example, part of an aircraft propulsion system. Fluid-tight means that the sealing gasket 23, once in contact with the second element 11, does not allow the passage of any fluid from one compartment to the other, and that the sealing gasket 23 is impermeable and does not allow the passage of any fluid by capillary action. Fire-resistant means that flames cannot propagate from one compartment 9 to the other 13, and that the sealing gasket 23 must not contribute to ignition on the rear face of the compartment 13. In other words, the sealing gasket 23 is fire-resistant. The second part 27 is substantially tubular but is deformable so that the support of the second part 27 on the second element 11 ensures the sealing of the joint without destroying the sealing joint 23. The second part 27 of the sealing gasket 23 is flexible and includes a longitudinal sector 29 intended to be in contact with the second element 11. The longitudinal sector 29 is shown flat in [Fig. 3] so that the sealing gasket 23 is shown in an assembled configuration. In a con- In the unassembled figure, the longitudinal sector is not in contact with the second element 11 and forms a bump. The second part 27 of the sealing joint 23, and consequently also the longitudinal sector 29, is formed from a substantially elastic, fire-resistant, and / or high-temperature material exceeding 250°C. The sealing material comprises a binder material, for example an elastomer such as silicone, and a reinforcing material, for example a ceramic, glass, or carbon fabric. A material that is substantially elastic is understood to be a material that can be deformed by pressure and returns to its original shape when said pressure is no longer exerted. Silicone ensures a fluid-tight seal and offers some resistance to high temperatures. In some embodiments, the sealing material comprises glass fabric and / or carbon fabric and / or aramid fabric and / or ceramic fabric, and / or boron fabric, preferably a layered combination of glass and carbon plies. Such materials, as well as ceramic fabrics in general, provide structural reinforcement for the seal 23 and ensure fire resistance. They are preferably combined with an elastomer such as silicone. The sealing gasket 23 includes a material coating 31 covering the longitudinal sector 29, i.e., positioned and visible on the outside of the longitudinal sector. The material coating 31 is slippery and hydrophobic. In particular, the material coating does not require the addition of lubricant. The term coating refers to the fact that the coating of material 31 is disposed on the surface of the sealing joint 23, and intended to be in contact with the second element 11 in the assembled configuration. Furthermore, the sealing joint 23 can take all sorts of joint shapes, including shapes other than an "omega" shape, the sealing joint in all cases comprising a coating of material 31 intended to be in contact with the second element 11. Sliding means that the material coating 31 minimizes friction during contact between the material coating 31 and the second element 11. In particular, the second element 11 can slide in contact with the sealing gasket 23 and especially in contact with the material coating 31 without damaging and / or carrying away any part of the sealing gasket 23 in the case of relative movements between the sealing gasket 23 and the second element 11. Sliding also means that the coefficient of friction, also called the coefficient of friction between the material coating 31 and the second element 11, is, for example, lower than the coefficient of friction between the second element 11 and the material of the longitudinal sector 29 not covered by the material coating 31. Hydrophobic means that the coating of material 31 is not wettable and, in particular, that the propagation of a fluid by capillary action along the coating of material 31 is not possible, or very low compared to the use of Nomex®. Specifically, the coating of material 31 has a wettability criterion preferably corresponding to a contact angle greater than or equal to 90°. The wettability criterion corresponds to the quantification of wetting, which is the ability of a liquid to spread on a surface. The contact angle allows for the measurement of wettability and is equivalent, for a liquid droplet 33 represented in [Fig. 4], to the angle A between the surface 35 in contact with the droplet 33, and the tangent 37 to the wall 39 of the liquid droplet 33 at the point of contact P between the surface 35, the droplet 33, and the surrounding medium 41. If the contact angle A is less than 90°, the droplet 33 spreads and the surface is said to be wettable. Conversely, if the contact angle A is greater than 90°, the droplet 33 does not spread and the surface is said to be non-wettable, in other words, it is hydrophobic. In a particular embodiment, the material coating 31 comprises a fabric or carbon fiber impregnated with silicone. For example, it may consist of a carbon fiber mesh or roll embedded in a silicone matrix to form a composite-type material coating 31. The coefficient of friction of the impregnated carbon fiber is of the same order as the coefficient of friction of Nomex® while its intrinsic hydrophobicity is greatly improved compared to the strong capillarity of Nomex®, the contact angle of the impregnated carbon fiber being greater than or equal to 90°. In another embodiment, the material coating 31 includes a hydrophobic layer produced by graphene spraying. This embodiment utilizes the properties of carbon detailed previously, namely, in particular, sufficient hydrophobicity to allow the sliding contact of the second element 11 with respect to the sealing gasket 23 without the passage of fluid by capillary action along said sealing gasket 23. In this embodiment, the hydrophobic layer is applied directly to the sealing material of the longitudinal sector 29, or to a layer of Meta-aramid, more commonly known as Nomex®, which allows good sliding, or to a layer of polyester fabric or impregnated carbon fabric which both allows sliding and enhances hydrophobicity. The material coating 31 is for example partially embedded in the sealing material of the second part 27 of the sealing joint 23. This is for example the case when the material coating 31 is made during the manufacture of said second part 27 of the sealing joint 23. Alternatively, the coating of material 31 covers the waterproofing material so as to create a layer distinct from the waterproofing material. This is the case, for example, when the re- garment of material 31 is added by layering after the manufacture of the second part 27 of the sealing joint 23. The various alternatives described can be combined with each other.

Claims

Demands

1. Sealing gasket (23) configured to be disposed between a first element (17) and a second element (11) of a propulsive assembly in an assembled configuration, characterized in that it comprises a longitudinal sector (29) intended to be in contact with the second element (11), the longitudinal sector (29) being formed of a material Fluid-tight and fire-resistant, substantially elastic, and comprising a coating of material (31) slippery and hydrophobic covering the area longitudinal (29).

2. Sealing gasket according to claim 1, wherein the coating of material (31) has a wettability criterion corresponding to an angle of contact (A) greater than or equal to 90°.

3. A sealing gasket according to any one of claims 1 and 2, wherein the material coating (31) comprises a fabric or carbon fiber impregnated with resin and / or silicone.

4. Sealing gasket according to any one of claims 1 to 3, in which the material coating (31) comprises a hydrophobic layer created by graphene projection.

5. Sealing gasket according to any one of claims 1 to 4, in of which the waterproofing material comprises an elastomeric binding material and a reinforcing material made of ceramic, glass, or carbon fabric.

6. A sealing gasket according to any one of claims 1 to 5, in which the material coating (31) is partially embedded in the waterproof material or covers the waterproof material.

7. Sealing gasket according to any one of claims 1 to 6, including an "omega" type cross-section comprising a first part (25) substantially planar fixed to the first element (17) and a second rounded part (27) comprising the longitudinal sector (29).

8. Aircraft propulsion system comprising a first compartment (9) liable to be exposed to fire and a second compartment (13), characterized in that it comprises a sealing joint (23) according to any one of claims 1 to 7 between the first com- compartment (9) and the second compartment (13).

9. Aircraft characterized in that it comprises a propulsion system according to the claim 8 and / or a sealing gasket (23) according to any one of them claims 1 to 7.