Sealing assembly for turbojet nacelle and nacelle comprising such an assembly

Abstract

This sealing assembly for a turbomachine nacelle (4), said nacelle (4) comprising a first panel (7) separated by a functional space (8) from a second panel (6), said panels (6, 7) being made of organic matrix composite materials, includes a metal sheet (9) disposed inside the nacelle (4) and constituting a barrier to the passage of a flame through said functional space (8), and further includes separation means (11) preventing contact between said metal sheet (9) and flammable gases that may be released by said panels (6, 7) in the event of a fire. Figure for the abbreviation: Figure 6

Description

Title of the invention: Sealing assembly for a turbojet engine nacelle and nacelle comprising such an assembly Technical field

[0001] The invention relates to a sealing assembly for a turbomachine nacelle for an aircraft, as well as to a nacelle equipped with such a sealing assembly. Prior art

[0002] An aircraft is powered by several turbomachines such as turbojets each housed in a nacelle also housing a set of ancillary actuation devices linked to its operation and ensuring various functions, when the turbojet is in operation or stopped.

[0003] A nacelle generally has a tubular structure comprising an air inlet in front of the turbojet engine, a middle section intended to surround a fan of the turbojet engine, and a rear section intended to surround the combustion chamber of the turbojet engine and capable of housing thrust reversal means.

[0004] The middle section of the nacelle generally comprises a fixed cowl located around an engine mounting mast and two movable cowls articulated and located on either side of the fixed cowl.

[0005] During the operating phase, the movable hoods are closed.

[0006] During the maintenance phase, the movable covers can be opened to allow access to the interior of the nacelle.

[0007] There is thus a functional space to be provided between each movable hood and the fixed hood in order to make the relative movement of the hoods possible.

[0008] In a turbojet engine, certain areas are likely to experience a fire in the event of damage. These are areas called "fire compartments". Other areas called "non-fire compartments", on the other hand, are devoid of any direct risk of ignition and must be protected from a fire originating from a fire compartment. For example, the interior of a nacelle constitutes a fire compartment and the exterior of the nacelle is a non-fire compartment.

[0009] It is therefore necessary to provide a fire barrier at the functional space separating the movable hoods and the fixed hood.

[0010] For this purpose, it is known to use a metal sheet arranged inside the nacelle and constituting a fire barrier at the level of said functional space.

[0011] However, modern nacelles include structures made of composite material, generally with an organic matrix.

[0012] The application of an external source of heat to a material, such as a radiation or a flame for example, has as its first consequence the heating or increase in temperature of said material.

[0013] In the case of an organic matrix composite material, from a critical temperature, the most thermally fragile bonds break and the organic matrix composite material degrades. This degradation leads to the formation of radicals which react to form low molecular mass organic molecules in the form of gases, generally flammable.

[0014] These flammable gases are likely to come into contact with said metal sheet constituting a fire barrier at the level of said functional space.

[0015] The temperatures reached by the metal sheet may be higher than the auto-ignition temperature of the flammable gases.

[0016] There is thus a risk of self-ignition outside the nacelle. Statement of the invention

[0017] The subject of the invention is a sealing assembly for a turbomachine nacelle, said nacelle comprising a first panel separated by a functional space from a second panel, said panels being made of organic matrix composite materials capable of emitting flammable gases when subjected to temperatures above a critical temperature characteristic of each composite material, said sealing assembly comprising a metal sheet disposed inside the nacelle and constituting a barrier to the passage of a flame through said functional space, characterized in that said sealing assembly further comprises separation means preventing contact between said metal sheet and said flammable gases likely to be released by said panels in the event of a fire.

[0018] According to one embodiment, said separation means comprise at least one shim covering the outer face of the metal sheet over the entire extent of the functional space.

[0019] According to one characteristic, the wedge is in contact with each panel over a predefined minimum contact length, at least equal to 50mm for a fixed side and at least equal to 10mm for a docking side.

[0020] According to an advantageous characteristic, said shim has thermal insulation properties aimed at maintaining the face likely to come into contact with the flammable gases at a temperature lower than the auto-ignition temperature of said flammable gases.

[0021] According to another advantageous characteristic, said shim has elastic mechanical characteristics allowing flexible contact with said panels.

[0022] For example, said shim is made of silicone.

[0023] For example, said wedge comprises a stack of layers of ceramic fabrics reinforced by a metal mesh.

[0024] According to another embodiment, said separation means comprise foils impervious to said flammable gases and arranged on the surface of each panel.

[0025] According to another characteristic, said foils cover each panel on two adjacent sides, namely a first side arranged outside the nacelle and a second side delimiting the functional space.

[0026] According to one characteristic, said foils cover each panel on three adjacent sides, namely a first side arranged outside the nacelle, a second side delimiting the functional space, and a third side arranged inside the nacelle and opposite the first side.

[0027] For example, the foils are metallic, glued or riveted or force-mounted using, for example, a spring clip.

[0028] For example, each foil is made up of a ply of carbon or ceramic, dry or pre-impregnated.

[0029] For example, each foil is cooked simultaneously with the cooking of the panel that it covers or is glued subsequently to said panel.

[0030] According to another aspect, the invention also relates to a turbojet engine nacelle comprising at least one sealing assembly as described above. Brief description of the drawings

[0031] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0032] [Fig-1] is a schematic cross-sectional view of an aircraft turbojet engine comprising a nacelle equipped with two movable cowls shown in the closed position;

[0033] [Fig.2] illustrates the movable covers of [Fig.l] in the open position;

[0034] [Fig.3] is a perspective view in a longitudinal direction of the nacelle of a metal sheet closing a functional space between a fixed cover and a movable cover according to the prior art;

[0035] [Fig.4] to [Fig.6] illustrate a shim arranged between the metal sheet and panels according to an embodiment of the invention; and

[0036] [Fig.7] to [Fig.8] illustrate foils arranged on the surface of each panel according to another embodiment of the invention. Detailed description of at least one embodiment

[0037] [Fig.l] represents an engine assembly 1 for aircraft intended to be fixed under a wing of the aircraft, this assembly 1 comprising a mounting mast 2, a double-flow turbojet engine 3, as well as a nacelle 4 surrounding the turbojet engine with longitudinal axis 5. The nacelle 4 comprises a fixed cowl 6 located around the mounting mast 2 and two movable cowls 7 articulated and located on either side of the fixed cowl 6.

[0038] In the operating phase, the movable covers 7 are closed.

[0039] During the maintenance phase, the movable covers 7 can be opened ([Fig.2]) in order to allow access to the interior of the nacelle, in particular to the turbojet 3.

[0040] In order to allow the opening kinematics of the movable hoods 7, a longitudinal functional space 8 is provided between each movable hood 7 and the fixed hood 6.

[0041] [Fig. 3] represents a perspective view in the longitudinal direction 5 of the nacelle 4 of a sheet 9 serving as a support for a seal 10 of the fire barrier type of a thrust reverser (TRU or “Thrust Reverser Unit” in English) according to the prior art. The seal 10 constitutes a fire-tight barrier between a fire compartment represented by a first zone of a middle section of the nacelle 4 and a non-fire compartment represented by a second zone adjacent to the first, located downstream thereof and containing the thrust reverser activation systems (TRAS or “Thrust Reverse Activation System” in English).

[0042] Conventionally, in order to allow the fire barrier type seal 10 of the TRU to pass from the area of ​​the fixed cover 6 to the area of ​​the movable cover 7, a metal sheet 9 is inserted above the functional space 8 on the inner side of the nacelle 4. The metal sheet 9 constitutes an elastic support for the seal 10 and allows the assembly to close the triple interface TRU - movable cover - fixed cover. Generally, the metal sheet 9 is made of titanium and may for example have a thickness of approximately 0.4 mm.

[0043] The interior of the nacelle 4 constitutes a fire compartment while the exterior of the nacelle is a non-fire compartment.

[0044] It is therefore necessary to provide a fire barrier at the functional space separating the movable covers 7 and the fixed cover 6.

[0045] Although the metal sheet 9 constitutes a barrier to the passage of a flame, there remains a risk of ignition on the non-fire side.

[0046] Indeed, as indicated previously, modern nacelles comprise structures made of composite material, generally with an organic matrix. In particular, the fixed cowl 6 and the movable cowls 7 can emit flammable gases when they are subjected to temperatures exceeding a critical temperature.

[0047] These flammable gases are likely to come into contact with the metal sheet 9.

[0048] However, the temperatures reached by the metal sheet 9 may be higher than the self-ignition temperature of the flammable gases emitted by the fixed cover 6 and the movable covers 7, with a risk of ignition on the non-fire side.

[0049] The invention aims to prevent the creation of a fire on the non-fire side by using a improved sealing assembly comprising separation means 11 which prevent contact between the flammable gases which may be emitted by the covers 6 and 7 in the event of a fire, and the metal sheet 9.

[0050] Most generally, the invention is applicable to two panels separated by a functional space. Each of the panels can be fixed, mobile or removable, independently of the other panel.

[0051] As illustrated in the example shown in Figures 1 and 2, one of the two panels may constitute a movable cover, while the other panel may constitute a fixed cover.

[0052] Other variants may be envisaged, without detracting from the generality of the invention.

[0053] For example, in another variant the two panels could constitute fixed covers.

[0054] For example, in another variant, one of the panels may constitute a removable cover, provided for maintenance of the nacelle for example, while the other panel may constitute a fixed cover.

[0055] In a first embodiment illustrated in figures 4 to 6, the separation means comprise at least one wedge 12 arranged between the metal sheet 9 and the panels 6 and 7. In the figures, identical elements bear the same references.

[0056] The wedge 12 is arranged so as to prevent contact near the functional space 8 between the metal sheet 9 and the flammable gases which may be released by the panels 6 and 7 in the event of a fire.

[0057] According to the embodiment illustrated in figures 4 to 6, the shim 12 covers the outer face of the metal sheet 9 over the entire extent of the functional space 8. Preferably, the shim 12 is arranged so as to be in contact with each panel 6 and 7 over a predefined minimum contact length L, at least equal to 50mm for a fixed side and at least equal to 10mm for a docking side.

[0058] The wedge 12 can be fixed on one of the panels 6 or 7 or on the metal sheet 9.

[0059] Preferably, the shim 12 has thermal insulation properties necessary for maintain the face likely to come into contact with the flammable gases at a temperature below the auto-ignition temperature of said flammable gases. Preferably, the shim 12 has elastic mechanical characteristics allowing flexible contact with the panels 6, 7, in order to avoid damage to said panels 6, 7.

[0060] In a preferred embodiment, the insulating shim 12 is made of silicone.

[0061] In other alternative embodiments, the production of the insulating shim 12 may be considered in other elastic thermal insulating materials. For example, the insulating shim 12 may comprise a stack of layers of ceramic fabrics reinforced with a metal mesh to achieve the desired elasticity in order to avoid damage to said panels 6, 7.

[0062] In a second embodiment illustrated in figures 7 and 8, the separation means 11 comprise foils 13 arranged on the surface of each panel 6, 7 in order to contain the flammable gases likely to be emitted by the panels 6, 7 and to prevent contact of said flammable gases with the sheet metal 9 arranged at the level of the functional space 8.

[0063] The foils 13 may have an L shape ([Fig.8]) covering each panel 6, 7 on two adjacent sides, namely a first side arranged outside the nacelle 4 and a second side delimiting the functional space 8.

[0064] Alternatively, the foils 13 may have a U shape ([Fig.7]) covering each panel 6, 7 on three adjacent sides, namely a first side arranged outside the nacelle 4, a second side delimiting the functional space 8, and a third side arranged inside the nacelle 4 and opposite the first side.

[0065] In all the variants of this embodiment, the overlap distance between a foil 13 and the side arranged outside the nacelle 4 of a panel 6, 7 is at least 25 mm.

[0066] Preferably, the foils 13 have a small thickness to limit the quantity of heat transmitted to the non-fire side. The foils 13 may be metallic or made of any other material impervious to flammable gases likely to be emitted by the panels 6, 7.

Claims

Claims

1. Turbomachine nacelle (4) comprising a first panel (7) separated by a functional space (8) from a second panel (6), said panels (6, 7) being made of organic matrix composite materials, said nacelle comprising at least one sealing assembly comprising a metal sheet (9) arranged inside the nacelle (4) and constituting a barrier to the passage of a flame through said functional space (8), characterized in that said sealing assembly further comprises separation means (11) comprising at least one shim (12) covering the outer face of the metal sheet (9) over the entire extent of the functional space (8), said separation means (11) preventing contact between said metal sheet (9) and flammable gases likely to be released by said panels (6, 7) in the event of a fire.

2. Turbomachine nacelle (4) according to claim 1, in which the wedge (12) is in contact with each panel (6, 7) over a predefined minimum contact length (L), at least equal to 50mm for a fixed side and at least equal to 10mm for a docking side.

3. Turbomachine nacelle (4) according to claim 1 or 2, wherein said shim (12) has thermal insulation properties aimed at maintaining the face likely to come into contact with the flammable gases at a temperature lower than the auto-ignition temperature of said flammable gases.

4. Turbomachine nacelle (4) according to any one of claims 1 to 3, in which said wedge (12) has elastic mechanical characteristics allowing flexible contact with said panels (6, 7).

5. Turbomachine nacelle (4) according to any one of claims 1 to 4, in which said shim (12) comprises a stack of layers of ceramic fabrics reinforced by a metal mesh.

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