Ejection cone for an aircraft turbine engine

Abstract

The present document relates to an exhaust cone for an aircraft turbine engine, extending along a longitudinal axis (X), said cone comprising a radially inner annular wall (104) and a radially outer skin (102) delimiting a flow path for a primary flow of hot gases and surrounding said inner annular wall, and partitions (106, 108) mounted radially between the outer skin and the inner annular wall and intersecting in such a way as to delimit therewith acoustic chambers (110), characterized in that said exhaust cone comprises at least one seal (112) arranged between a radial end (107) of one of the partitions and at least one of either the inner annular wall (104) and / or the outer skin (102).

Description

[0001] DESCRIPTION

[0002] TITLE: Ejection cone for aircraft turbomachine

[0003] Technical field of the invention

[0004] This document relates to an aircraft turbomachine cone, in particular an ejection cone with a sealed acoustic box.

[0005] State of the prior art

[0006] This disclosure relates to an assembly located at the rear, at a downstream end, of an aircraft turbojet engine to optimize the flow of air expelled by the turbojet engine. More specifically, this disclosure relates to the connection between what is often referred to as an exhaust cone and, located just upstream of the exhaust cone, a turbojet engine casing, for example a turbojet engine gas outlet casing.

[0007] Figure 1 represents an assembly for an aircraft turbojet engine, comprising a central gas ejection element, annular around a longitudinal axis X and adapted so that gas is ejected by the turbojet engine around it, from upstream (AM) to downstream (AV), said assembly being connected to a metal outlet of a turbojet engine. The aforementioned longitudinal axis X is the longitudinal axis, or axis of rotation, of the turbomachine, in particular of the fan 20 and the moving blades of the engine 12. The central gas ejection element may correspond to the ejection cone, referenced 1 below, or at least to the upstream part 1a below.

[0008] The aircraft gas turbojet engine 10 includes a central portion, forming the gas turbine engine 12, mounted within an engine nacelle assembly 14, as is typical of an aircraft designed for subsonic operation, such as a turboprop or a turbofan engine. The nacelle assembly 14 generally includes an engine nacelle 16 and a fan nacelle 18 surrounding a fan 20 located axially upstream of the engine 12.

[0009] The engine 12 comprises, axially in the downstream part, at least one turbine which may be a low pressure turbine and, still in the downstream part, a metallic exhaust casing 22 and comprising an internal annular shell 22a and an external annular shell 22b delimiting between them a downstream part of the primary annular vein 24 in which the combustion gases from the combustion chamber of the engine 12 circulate.

[0010] The inner annular shell 22a is connected, at its downstream end, to the ejection cone 1, which may comprise an upstream portion 1a, of substantially cylindrical shape, and a downstream portion 1b of conical shape. The inner annular shell 22a is aligned with the outer wall of the ejection cone 1 to form a homogeneous flow path for the air leaving the engine 12. To reduce the noise pollution produced by the gases leaving the engine, an acoustic box may be arranged inside the ejection cone, comprising acoustic partitions interposed between the outer wall of the ejection cone 1 and an inner annular wall of the outer wall, forming a cavity. The assembly of the acoustic partitions and the inner and outer walls lacks sealing. Indeed, a clearance exists between the partitions and the inner wall and / or the outer wall.This clearance, coupled with a pressure differential between the acoustic partitions, creates an acceleration of the air around the acoustic partitions, which creates a thermal gradient in the walls and limits their mechanical strength. In addition, the clearance must be less than 1 mm to comply with acoustic attenuation.

[0011] There is a need for improved acoustic enclosures in ejection cones.

[0012] Summary of the invention

[0013] This document relates to an exhaust cone for an aircraft turbomachine, extending along a longitudinal axis, said cone comprising a radially inner annular wall and a radially outer skin delimiting a flow path for a primary flow of hot gases and surrounding said inner annular wall, and partitions mounted radially between the outer skin and the inner annular wall and intersecting so as to delimit acoustic boxes therewith, characterized in that said exhaust cone comprises at least one seal arranged between a radial end of one of the partitions and at least one of the parts constituting the inner annular wall or the outer skin.

[0014] The seal limits the infiltration of air from the primary flow into the acoustic boxes. This improves the acoustic attenuation of the noise emitted by the turbomachine.

[0015] The gasket may be interposed between a radially outer end of the partition and the outer annular wall.

[0016] The seal may be inserted between a radially inner end of the partition and the inner annular wall. This arrangement allows the seal to be constrained by the partition more effectively, in particular by the weight of the partition. This ensures better sealing of the acoustic enclosure.

[0017] The partitions can be fixed to the outer skin or to the inner annular wall, for example by welding, brazing or screwing. The radially inner end can be arranged with a radial clearance relative to the inner annular wall. Thus, it is advantageous to arrange the sealing gasket between the radially inner end and the inner annular wall.

[0018] According to one embodiment, the seal may comprise an O-ring connected to a fastening strip. The fastening strip may be attached to a downstream face of the partition and the O-ring may be arranged at least partially against an upstream face of said partition.

[0019] The toric part can thus be placed on the side where the maximum pressure is exerted, which ensures that the seal is pressed against the internal annular wall.

[0020] The fixing strip may have a thickness less than the radial clearance to allow the passage of the fixing strip between the radially inner end of the partition and the inner annular wall.

[0021] In addition, the diameter of the toric portion may be greater than the radial clearance to prevent the toric portion from passing between the partition and the inner annular wall. Thus, the sealing gasket obstructs the radial clearance between the partition and the inner annular wall and thus seals the acoustic enclosure.

[0022] The fixing strip may be fixed to the partition by a lock wire passing through holes provided in said partition and said fixing strip. Small diameter holes may be made in the partition and the lock wire may pass on either side of the partition and the strip like a seam. In particular, a button may be provided on the upstream face of the partition to receive the lock wire and hold it in the locking position. This arrangement makes it possible to limit air leakage into the acoustic enclosures if the holes have too large a diameter.

[0023] Alternatively, the fixing strip can be fixed to the partition by riveting or screwing, washers can be provided at the rivets and / or screws.

[0024] According to one embodiment, the seal may comprise an upstream toric portion and a downstream toric portion. The upstream toric portion may be arranged in contact with the upstream face of the partition and the downstream toric portion may be arranged in contact with the downstream face of said partition.

[0025] The diameter of the upstream toric part and / or the diameter of the downstream toric part may be less than the radial clearance.

[0026] The upstream toric part and the downstream toric part can be connected by a brake wire passing through holes provided in the partition holding said seal.

[0027] According to one embodiment, the seal may be arranged between the radially inner end of the partition and the inner wall. The upstream toric portion and the downstream toric portion of said seal may be connected by a connecting strip arranged under the radially inner end of the partition. The connecting strip may be held against the inner wall by said partition.

[0028] The toric part(s) of the seal can be made by weaving or braiding ceramic and / or metal fibers.

[0029] In addition, the upstream and downstream toric portions of the seal may be made by weaving or braiding ceramic and / or metal fibers. The seal may comprise a casing made of high-temperature material made by weaving, braiding or winding ceramic fibers or metal high-temperature fibers. The seal may comprise a central body surrounded by the casing made of the same material as the casing or a strand of high-temperature fibers, for example refractory or silica fibers.

[0030] The seal may comprise a fixing strip fixed to the upstream face of the partition and a curved portion comprising a convex surface bearing against the internal wall. The fixing strip may be fixed to the partition by a lock wire passing through holes provided in said partition and said fixing strip. In particular, a button may be provided at the upstream face of the partition to receive the lock wire and hold it in the locking position. Alternatively, the fixing strip may be fixed to the partition by riveting. The seal may be metallic.

[0031] The acoustic boxes may be formed by longitudinal partitions and circumferential partitions. The longitudinal partitions and the circumferential partitions may be perpendicular to each other. The longitudinal partitions and the circumferential partitions may be perpendicular to the inner annular wall. At least one, in particular each, of the acoustic boxes may be equipped with a seal, a portion of which extends along a lateral face of one of the longitudinal partitions forming said acoustic box and an upstream face of the downstream circumferential partition forming said acoustic box.

[0032] This document also relates to a turbomachine for aircraft comprising an ejection cone as mentioned above.

[0033] Brief description of the figures

[0034] [Fig. 1] represents a sectional view of a turbomachine according to the prior art.

[0035] [Fig. 2] represents a perspective view of an upstream part of an ejection cone comprising an acoustic structure equipped with a first example embodiment of the sealing joint.

[0036] [Fig. 3] represents a sectional view of the upstream part of the ejection cone of Figure 2. [Fig. 4] represents an enlarged view of one end of one of the partitions of the acoustic structure of Figures 2 and 3.

[0037] [Fig. 5] represents a front view of a first acoustic box of the acoustic structure of figures 2 to 4.

[0038] [Fig. 6] represents a perspective view of the seal fitted to the first acoustic box in Figure 5.

[0039] [Fig. 7] represents a front view of a second acoustic box of the acoustic structure of Figures 2 to 4. [Fig. 8] represents a perspective view of a first seal equipping the second acoustic box of Figure 7.

[0040] [Fig. 9] represents a perspective view of a second seal fitted to the second acoustic box of Figure 7.

[0041] [Fig. 10] shows an enlarged view of one end of one of the partitions of the acoustic structure equipped with a second example of the sealing joint.

[0042] [Fig. 11] shows an enlarged view of one end of one of the partitions of the acoustic structure equipped with a third example of the sealing joint.

[0043] [Fig. 12] shows an enlarged view of one end of one of the partitions of the acoustic structure equipped with a fourth example of the sealing joint.

[0044] Detailed description of the invention

[0045] Figure 2 represents an upstream portion of an ejection cone which may be the ejection cone 1 of Figure 1. Figure 3 represents a sectional view of the upstream portion of Figure 2. This upstream portion comprises an annular outer skin 102 around the longitudinal axis X. The outer skin 102 is made of ceramic matrix composite and surrounds an inner annular wall 104 which is also made of ceramic matrix composite. The outer skin 102 and / or the inner wall 104 are connected upstream to an exhaust casing, for example the exhaust casing 22, and downstream to a conical wall of the ejection cone by a connecting flange 114. In particular, the outer skin 102 is fixed at its downstream portion to the ejection cone and is free at its upstream portion and only the inner wall 104 is fixed upstream to the exhaust casing.

[0046] Longitudinal partitions 106 and circumferential partitions 108 are arranged between the outer skin 102 and the inner wall 104. The partitions 106 and 108 extend substantially perpendicular to the inner wall 104. The longitudinal partitions 106 are also substantially perpendicular to the circumferential partitions 108 and form a honeycomb structure, comprising acoustic boxes 110 provided to attenuate the noise in the turbomachine.

[0047] The longitudinal partitions 106 are fixed to the internal wall 104 by screws 130 through retaining brackets 132 which are also fixed to said longitudinal partitions. Each circumferential partition 108 is interposed circumferentially between two consecutive longitudinal partitions and said circumferential partition 108 is fixed on either side of said two consecutive longitudinal partitions.

[0048] The assembly of the partitions to the inner wall 104 does not ensure sealing of the acoustic boxes because a radial clearance remains between a radially inner end 107 of the partitions 108, 106 and the inner wall 104. A portion of the air flow F passing through the turbomachine can infiltrate into the acoustic boxes 110 through this radial clearance. In addition, this clearance impacts noise attenuation because the acoustic waves are no longer correctly channeled into the cell.

[0049] To limit these infiltrations, a seal 112 is fitted to fill the radial clearance. Figure 4 shows the arrangement of the seal 112 relative to the circumferential partition 108 but this arrangement can be applicable to the longitudinal partition 106. The seal 112 comprises an O-ring portion 118 connected to a fixing strip 116. The fixing strip 116 can have a rectangular section and is fixed to the downstream face of the circumferential partition 108 for example by rivets 120. The fixing strip 116 has a thickness less than the radial clearance between the end 107 and the internal wall 104. The end 107 of the circumferential 108 abuts against the O-ring portion 118, in particular at the junction between the O-ring portion 118 and the fixing strip 116. The O-ring portion 118 is arranged against the upstream face of the circumferential partition 108.The toric portion 118 has a diameter greater than the radial clearance, so it is held in place.

[0050] A first acoustic box 110 is shown in Figure 5 and includes a seal 112A, similar to the seal 112 of Figure 6. The first acoustic box 110 is formed by two longitudinal partitions 106 and a downstream circumferential partition 108 attached to each of the longitudinal partitions 106 at its circumferential ends. The seal 112A is made in a single part. The fixing strip 116 of the seal 112A has a shape complementary to the downstream surface of the circumferential partition 108 and a portion of the longitudinal partition 106. A first toric portion 1181 of the seal 112 has a shape complementary to the upstream surface of the circumferential partition 108. A second toric portion 1182 of the seal 112 is arranged at the longitudinal partition 106.

[0051] A second acoustic box 110 is shown in Figure 7 and includes the seal 112A of Figure 8. The second acoustic box 110 is formed laterally by two longitudinal partitions 106. The second acoustic box 110 is formed upstream by a downstream circumferential partition 108 attached to each of the longitudinal partitions 106 at its circumferential ends. The second acoustic box 110 is also formed upstream by a first circumferential partition 1081 and a second circumferential partition 1082 attached to each other by an attachment to the inner wall 104 and to the longitudinal partitions. The first circumferential partition 1081 is equipped with the seal 112B and the second circumferential partition 1082 is equipped with the seal 112A. The 112A seal is formed from a single seal sector on which a specific cut has been made to accommodate the geometry of the IO82 and 106 walls.The seal 112A, when mounted in the acoustic box 110, has a shape complementary to the second circumferential partition IO82 and the longitudinal partition 106 adjacent to said second circumferential partition IO812. The seal 112A comprises a cutout 111A of the toric portion 118 and thus allows the insertion of the seal 112A into the second acoustic box 110.

[0052] The seal 112B is shown in Figure 9. The seal 112B comprises a single sector without a cutout and which has a shape complementary to the downstream surface of the first circumferential partition 1081, when the seal 112B is mounted in the acoustic box 110.

[0053] The seal 112, 112A or 112B comprises a casing made of high-temperature material produced by weaving, braiding or winding ceramic fibers and / or high-temperature metal fibers. This casing surrounds a central body of the seal 112 made of the same material as the casing or a strand of high-temperature fibers, for example refractory or silica fibers.

[0054] A second example of a seal 212 is shown in Figure 10. The seal 212 comprises a first toric portion 214 arranged against an upstream face of the circumferential partition 108 and a second toric portion 216 arranged against a downstream face of the circumferential partition 108. The first and second toric portions 214 and 216 each have a diameter greater than the radial clearance between the end 107 and the inner wall 104. The seal 212 comprises a casing made of high-temperature material produced by weaving, braiding or winding ceramic fibers and / or high-temperature metal fibers. This casing surrounds a central body of the seal 212 made of the same material as the casing or a strand of high-temperature fibers, for example refractory or silica fibers.

[0055] The first toric portion 214 is connected to the second toric portion 216 by a connecting strip 218 having a rectangular section. The connecting strip 218 is arranged between the end 107 and the inner wall 104. The connecting strip 218 has a thickness less than the radial clearance.

[0056] Alternatively, in the third seal 312 of Figure 11, the first toric portion 214 is connected to the second toric portion 216 by a brake wire 318 passing through holes provided in the circumferential partition 108 and the toric portions 214 and 216. The brake wire 318 may be metallic.

[0057] A fourth seal 412 is shown in Figure 12 and comprises a fastening strip 416 secured to the upstream face of the circumferential partition 108. The seal 412 comprises a curved portion 414 comprising a convex surface 415 arranged in contact with the inner wall 104. The curved portion 414 has a “U” shape and has a concave surface opposite the convex surface 415 and facing the outer skin 102. The fastening strip 416 is connected to the upstream face of the circumferential partition by a lock wire passing through the fastening strip 416 and the circumferential partition 108 and held tight by a button 420.

[0058] Each of gasket 212, gasket 312, and gasket 412 are described in relation to circumferential bulkhead 108 but may be arranged at a longitudinal bulkhead.

Claims

DEMANDS 1. Exhaust cone for an aircraft turbomachine, extending along a longitudinal axis (X), said cone comprising a radially internal annular wall (104) and a radially external skin (102) defining a flow path for a primary flow of hot gases and surrounding said internal annular wall, and partitions (106, 108) mounted radially between the external skin and the internal annular wall and intersecting so as to define acoustic enclosures (110), characterized in that said exhaust cone comprises at least one sealing gasket (112; 212; 312; 412) arranged between a radial end (107) of one of the partitions and at least one of the parts constituting the internal annular wall (104) or the external skin (102), in which the sealing gasket is interposed between a radially internal end of one of the partitions and parts constituting the internal annular wall (104).

2. Cone according to the preceding claim, in which the sealing joint (112) comprises a toroidal portion (118) connected to a fixing strip (116), in which the fixing strip is fixed to a downstream face of the partition (108) and the toroidal portion (118) is arranged at least in part against an upstream face of said partition.

3. Cone according to claim 1, wherein the sealing joint (212;312) comprises an upstream toroidal part (214) and a downstream toroidal part (216), wherein the upstream toroidal part is disposed in contact with the upstream face of the partition (108) and the downstream toroidal part is disposed in contact with the downstream face of said partition.

4. Cone according to the preceding claim, in which the upstream toroidal part (214) and the downstream toroidal part (216) are connected by a brake wire (318) passing through orifices provided in said partition (108).

5. Cone according to claim 3, in which the sealing gasket (212) is arranged between the radially internal end (107) of the partition (108) and the internal wall (104), and in which the upstream toroidal part (214) and the downstream toroidal part (216) of said sealing gasket are connected by a connecting strip (218) arranged under the radially internal end of the partition.

6. Cone according to any one of claims 2 to 5, wherein the toroidal part (118) of the sealing joint (112) is made by weaving or braiding metallic ceramic fibers or wherein the upstream and downstream toroidal parts (214,216) of the sealing joint (212; 312) are made by weaving or braiding metallic ceramic fibers.

7. Cone according to claim 1, in which the sealing joint (412) comprises a fixing strip (416) fixed to the upstream face of the partition (108) and a curved part (414) having a convex surface (415) bearing against the inner wall (104).

8. Cone according to claim 2 or claim 7, wherein the fixing strip (116; 416) is fixed to the partition (108) by a brake wire (418) passing through holes provided in said partition and said fixing strip.

9. Cone according to any one of the preceding claims, in which the acoustic chambers (110) are formed by longitudinal partitions (106) and circumferential partitions (108), wherein at least one of the acoustic enclosures is equipped with a sealing gasket (112A, 112B) a portion of which extends along a lateral face of one of the longitudinal partitions (106) forming said acoustic enclosure and an upstream face of the downstream circumferential partition (108) forming said acoustic enclosure.

10. Aircraft turbomachine comprising an ejection cone according to any one of the preceding claims.

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