EJECTION CONE HAVING A FLEXIBLE AERODYNAMIC ATTACHMENT

Abstract

The invention relates to an assembly for an aircraft turbomachine, comprising a central element (1) for the ejection of gas, and a connecting flange (9) interposed between, upstream, a gas outlet (22a) made of metal for a turbomachine, and, at the downstream end, the central element (1). The connecting flange comprises an annular portion (9a) and flexible tabs (11) having axially: a first end (111a) where the tab is connected to the said annular portion, and a second free end (111b), projecting radially inwardly with respect to the first end and to which said tab is attached with the central element (1).

Claims

1. An assembly for a turbomachine of an aircraft, the assembly comprising: a metal gas outlet for the turbomachine, a central element for ejecting gas, which is annular about an axis and adapted to have gas ejected around it by the turbomachine, from upstream to downstream, and a connecting flange interposed between, upstream, the metal gas outlet, and downstream, the central element, to connect the metal gas outlet to the central element, the connecting flange comprising an annular portion, and, circumferentially, flexible tabs individually having, axially: a first end at which the flexible tab is connected to said annular portion, and a second free end at which said flexible tab is attached with the central element, the second free end being located axially upstream of the first end and, on each flexible tab, the second free end extends radially inwardly with respect to the first end, wherein the central element has a peripheral wall: provided with an acoustic-attenuation structure, and having, upstream of the acoustic-attenuation structure, an upstream end portion: which is located radially inwardly with respect to the flexible tabs, and where the central element is attached with said flexible tabs at said second free ends, so that the acoustic-attenuation structure is confined downstream of the upstream end portion.

2. The assembly according to claim 1, wherein the attachment between the central element and said flexible tabs comprises screws passing through the central element and the flexible tabs, each screw comprising a threaded rod having a head disposed radially inwardly with respect to the upstream end portion and the flexible tabs.

3. The assembly according to claim 1, wherein the flexible tabs extend radially inwardly with respect to the annular portion, the annular portion extending toward upstream by a radial attachment collar oriented radially inwards.

4. The assembly according to claim 1, wherein the acoustic-attenuation structure extends axially to said tabs.

5. The assembly according to claim 1, wherein the central element is made of a ceramic matrix composite and the connecting flange is made of metal.

6. The assembly according to claim 1, wherein one said flexible tabs are connected to said annular portion, at a said first end, by respective weldings.

7. The assembly according to claim 1, wherein said annular portion defines a solid wall which uniformly occupies a space between the metal gas outlet and, downstream, the central element.

8. The assembly according to claim 1, wherein said annular portion has, at a downstream end, an annular seal having flexible fingers supported against a radially outer surface of the central element, so as to ensure an aerodynamic continuity.

9. The assembly according to claim 8, wherein the support of the flexible fingers is located towards a break in slope where the central element tapers towards the upstream end portion.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0065] FIG. 1 is a schematic profile section (axial section) of a known aircraft turbomachine;

[0066] FIG. 2 corresponds in axial half-section to the local view in frame II of FIG. 1, in a version different from that of the invention;

[0067] FIG. 3 is a perspective view of the connecting flange (9 hereinafter), shown in FIG. 2; and

[0068] FIG. 4 corresponds to a portion of the view of FIG. 2, but in a version in accordance with the invention, at the enlargement of the area marked IV FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0069] FIG. 2 shows, with reference to FIG. 1 and therefore on a turbojet engine 10, an engine tail assembly 12, comprising a central element for gas ejection 1 (or ejection cone) and a connecting flange 9 interposed between, upstream, a metal outlet of a turbojet engine (in this case the inner annular shroud 22a of the exhaust housing) and, downstream, the said central element 1, in order to connect them together by means of axial attachments 5, which can be screws. The central element 1 is made of ceramic matrix composite and is annular around the (X) axis. It is adapted to have gas ejected by the turbojet engine around it, from upstream to downstream; see arrow F FIGS. 1, 2.

[0070] In this embodiment, not in accordance with the invention and as also illustrated in FIG. 3, the connecting flange 9 comprises an annular portion 9a, coaxial with the central element 1 and, circumferentially, flexible tabs 11.

[0071] The flexible tabs 11 follow one another circumferentially, in a regular sequence, around the X axis, on the annular portion 9a. The tabs 11 are presented as blades that can be roughly rectangular. For their flexible articulation with respect to the annular portion 9a, they have individually, axially: [0072] a first end 11a at which the tab is integrally connected to the said annular portion 9a, and [0073] a second, free end 11b, projecting radially (Z-axis) outwardly from the first end 11a and to which the tab 11 is attached with the central element 1.

[0074] Each end can therefore bend at the first end 11a. They define as many flexible supports. The central element/ejection cone 1, hereinafter referred to systematically as the ‘central element’, is made of ceramic matrix composite (CMC) and the connecting flange 9 is made of metal. It can be titanium alloy or any other high temperature resistant alloy.

[0075] In particular, in order not to attach the tabs 11 to the central element 1 in the zone treated for acoustic attenuation (see details below; zone 13) or in the bulb 7, the second free end 11b of a said (each) flexible tab 11, where there is attachment with the central element 1, is located axially upstream (AM) of the first end 11a of this tab.

[0076] The central element 1 has a peripheral wall 15: [0077] locally provided with an acoustic-attenuation structure 17 with an acoustically absorbent core, which can be honeycombed, and [0078] having, upstream of the acoustic-attenuation structure 17, an upstream end portion 19 where the central element 1 is attached with the said flexible tabs 11, at their second free ends 11b.

[0079] In this way, the acoustic-attenuation structure 17 is confined downstream of the portion 19 where the attachment with the tabs 11 takes place.

[0080] To make the attachment more reliable, the upstream end portion 19 favourably forms a circumferentially closed ring integrally extending the peripheral wall 15 upstream with respect to the acoustic-attenuation structure 17, like an axial. This annular rim 19 has holes 21 through which attachment screws 23 pass, which also pass through other holes 25 in the flexible tabs 11 towards their respective second free ends 11b.

[0081] In addition, in order to facilitate a large radial clearance and the fitting of attachments (such as screws 23; see FIG. 2), the flexible tabs 11 extend radially outwards from the cut-outs 18 formed in the annular portion 9a; see FIG. 3.

[0082] In practice, the central element 1 can comprise, as shown with reference to FIG. 1, the upstream portion 1a (commonly referred to as the “front plug”) and, attached to it axially (for example by bolting), the downstream portion 1b (commonly referred to as the “rear plug”). It would then be this upstream portion 1a which would be equipped with at least one so-called acoustic-attenuation structure 17, and thus with the wall 15 and the portion 19. However interesting this solution may be, it can still be improved; this is the case with the solution of the invention schematised in FIG. 4 where the references are those of the previous figures increased by a hundred for the parts and pieces which correspond to each other and which are identical or similar in operation.

[0083] Comparing FIGS. 2 and 4, it is easy to see the similarities and differences between the two solutions. Furthermore, using FIG. 3, where the connecting flange 9 is shown in its entirety, along its entire perimeter, it is easy to transpose the cross-sectional view of FIG. 4 to the connecting flange 109 of the invention, which extends circumferentially in an identical manner to the connecting flange 9.

[0084] Hereafter, only the differences between the solutions are detailed.

[0085] Thus, in the “modified solution” of the invention, there is radially, on the (and preferably each) flexible tab(s) 111, a said free second end 111b extending radially inwardly from the first end 111a.

[0086] In this way, the risk of leakage or deviation of the gas flow is limited, since the said annular portion 109a, which is radially more outer than the flexible tabs 111, naturally forms a screen, while at the same time making it possible to offset the attachment zones radially (see attachments 105 and 123) and to combine flexibility and ease of assembly.

[0087] By ensuring flexibility from downstream (AV) to upstream (AM) in the attachments via the flexible tabs 111, it will also be possible to bring the attachment of the central element 3/ejector cone 1 upstream, thus towards the connecting flange 109.

[0088] Rather than being integral with the annular portion 109a, the flexible tabs 111 can be welded (mark 39 FIG. 4) to this annular portion at their respective said first ends 111a.

[0089] For the sealing between the said metal outlet 22 of the turbomachine 10 and, downstream, the central element 3, it is also proposed that the said annular portion 109a of the connecting flange 109 define a solid wall which (axially and circumferentially) thus uniformly occupies the space between the metal outlet 22 of the turbomachine and the said central element 3. The same objective is followed, with intended aerodynamic continuity, in that the said annular portion has, at a free downstream end 109a1, an annular seal 27 with flexible fingers 270 bearing against a radially outer surface (in the example the peripheral wall 15) of the central element 3/ejection cone 1.

[0090] In particular, the support can be located in the upstream portion 1a, towards a break in slope 1a1 where the central element 3/ejection cone 1 tapers in direction to leave sufficient radial space 29 at the flexible tabs 111 and at the radial attachments 123.

[0091] As in the solution in FIG. 2, the solution in FIG. 4 proposes that the central element 1/3 therefore has a peripheral wall 15: [0092] provided with an acoustic-attenuation structure 17, and [0093] having, upstream of the acoustic-attenuation structure, an upstream end portion 19: [0094] located radially inwardly with respect to the flexible tabs 111, and [0095] wherein the central element 1/3 is attached with the said flexible tabs 111 at their said second free ends 111b.

[0096] This facilitates assembly between the central element 1/3 and the connecting flange: it is possible to work radially well away from the gas stream F.

[0097] It is also proposed that the attachment between the central element 1/3 and the said flexible tabs 111 be carried out by the screws 123, which will pass through them, radially a priori. The screws 123 will each favourably comprise a threaded rod 123a having an enlarged head 123b disposed radially inwardly with respect to the upstream end portion 1a (and in particular its tapered portion 1a1) and to the flexible tabs 111.

[0098] This will allow the screw heads 123b to be screwed in radially from the inside. The radial space 29 can remain reduced between the flexible tabs and the said annular portion 109a, just sufficient to place a threaded hole therein, for example via a nut 35 engaged with the corresponding threaded rod 123a.

[0099] And for attachment to the metal outlet 22a, not only will the flexible tabs 111 advantageously extend radially inwards with respect to the annular portion 109a, but the annular portion 109a can then be extended upstream by a radial attachment collar 37, oriented radially inwards (and not outwards as in the solution of FIG. 2: outer collar or rim 33).

[0100] Moreover, aerodynamic continuity will be further encouraged with, axially, opposite the radial collar 37, an annular rim 31 for attaching the metal outlet 22a also oriented radially inwards (and not outwards as in the solution of FIG. 2).

[0101] All this is useful for a practical, reliable and aerodynamic connection between a metal outlet 22 and a central element 1/3 made from CMC and acoustically treated.

[0102] The connecting flange 109 can then be metallic, especially if the tapered portion 1a1: [0103] extends upstream to the flexible tabs 111, radially inwards, and [0104] also has a acoustic-attenuation structure 17.

[0105] As already indicated, the above will preferably be achieved: [0106] with a said upstream end portion 19 for attachment of the central element 1/3 extending parallel to the said axis (X) (thus avoiding the aforementioned inclined connections), [0107] in the same way for the tabs 111 towards their said second ends 111b, so that these tabs and the said upstream end portion 19 of the central element 3/ejection cone 1 be attached together, in a radially reduced space.