Arrangement for an exhaust cone of an aircraft turbo engine

Description

TECHNICAL FIELD

[0001] The invention relates to an assembly for an aircraft turbomachine exhaust cone, an ejection cone for an aircraft turbomachine comprising such an assembly, as well as an aircraft turbomachine comprising such an ejection cone. STATE OF THE PRIOR ART

[0002] Conventionally, a turbomachine for an aircraft comprises, from upstream to downstream in the direction of gas flow in an axial direction, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine and an exhaust nozzle comprising an exhaust casing and an ejection cone connected, upstream, to the exhaust casing.

[0003] This ejection cone comprises an annular upstream part equipped with acoustic boxes for attenuating the noise produced by the combustion of the gases and / or the rotation of the different turbine stages and propagating along the turbomachine, as well as a conical downstream part. These acoustic boxes are formed by a first radially internal annular wall, a second radially external annular wall and by straight partitions extending generally radially between the first and second walls and defining between them a honeycomb alveolar structure. The partitions are further assembled by brazing to the first wall. The acoustic boxes thus formed have small dimensions and a small volume, in particular of the order of 1 cm 3 < to 2 cm 3 < .

[0004] However, the implementation of such acoustic boxes is not always suitable. For example, it is not well suited to absorbing low-frequency noise, which is the case for combustion noise. Furthermore, the brazing attachment provided between the partitions and the first wall is not suitable for all types of materials, such as ceramic matrix composite materials. It is also not suitable for the use of different materials for the partitions and the first and second walls and for absorbing the forces generated by the differential thermal expansion between the partitions and the first and second walls due to the use of such different materials. An assembly for an ejection cone according to the prior art is disclosed in WO 2013 / 121155 A1. STATEMENT OF THE INVENTION

[0005] The present invention aims to overcome the problems mentioned above.

[0006] For this purpose, according to claim 1, the invention relates to an assembly for an aircraft turbomachine exhaust cone, comprising a first annular wall centered on a longitudinal axis of axial direction oriented from upstream to downstream, a plurality of first partitions and second partitions extending substantially perpendicularly from the first wall, in which the first partitions extend generally in the axial direction and are distributed circumferentially around the first wall, in which the second partitions extend generally in a circumferential direction between the pairs of adjacent first partitions and are distributed circumferentially around the annular wall in at least one circumferential row, and in which the first wall, the first partitions and the second partitions define between them a plurality of acoustic boxes distributed around the first wall.

[0007] According to a first aspect of the invention, the second partitions are curved partitions comprising at least one arcuate portion in the axial direction upstream or downstream.

[0008] According to alternative embodiments of this first aspect of the invention which can be taken together or separately: the arcuate portions of the second partitions of at least one of the circumferential rows define a pattern repeating along said circumferential row and the pattern of the arcuate portions of the second partitions of said circumferential row consists of an upstream or downstream arcuate portion, such that all the arcuate portions of the second partitions of said circumferential row are oriented in the same axial direction, upstream or downstream; the arcuate portions of the second partitions of at least one of the circumferential rows define a pattern repeating along said circumferential row and the pattern of the arcuate portions of the second partitions of said circumferential row consists of an upstream arcuate portion followed by a downstream arcuate portion, so as to obtain an alternation of an upstream arcuate portion and a downstream arcuate portion all along said circumferential row;the arcuate portions of the second partitions of at least one of the circumferential rows define a pattern repeating along said circumferential row and the pattern of the arcuate portions of the second partitions of said circumferential row consists of two upstream arcuate portions followed by two downstream arcuate portions, so as to obtain an alternation of two upstream arcuate portions and two downstream arcuate portions along said circumferential row; along at least one of the circumferential rows, two or more successive arcuate portions are interposed between each pair of adjacent first partitions; each second partition of at least one of the circumferential rows carries a single arcuate portion; each second partition of at least one of the circumferential rows carries an upstream arcuate portion and a downstream arcuate portion; ;

[0009] According to a second aspect of the invention which is combined with the first aspect, an assembly formed by the first and second partitions is fixed to the first wall by means of first fixing members arranged upstream and second fixing members arranged downstream, and in that the first fixing members are circumferentially offset relative to the second fixing members.

[0010] The invention also relates to an ejection cone for an aircraft turbomachine comprising an assembly as previously described.

[0011] The invention also relates to a turbomachine for aircraft, comprising an ejection cone as previously described. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which: [ Fig. 1 ] is a schematic view, in longitudinal section, of a turbomachine comprising an ejection cone provided with an assembly according to an embodiment of the invention: [ Fig.2 ] is a perspective view of the ejection cone shown in figure 1 ; [ Fig.3 ] is a partial perspective view of the ejection cone shown in figure 2 ; [ Fig.4 ] is a partial view, in longitudinal section, of the ejection cone illustrated in figures 2 And 3 ; [ Fig.5 ] is a partial radially outward view of the ejector cone shown in figures 2 to 4 ; [ Fig.6] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig.7 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig.8 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig.9 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig. 10 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig. 11 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig. 12] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig. 13 ] is a partial and schematic view, radially outwards of an ejection cone according to an embodiment of the invention; [ Fig. 14 ] is a partial and schematic view, radially outwards, of an ejection cone according to an embodiment of the invention. DETAILED DESCRIPTION

[0013] There figure 1 shows a turbomachine 100 for an aircraft comprising an ejection cone 101 provided with an assembly 10 according to an embodiment of the invention. The ejection cone 101 is shown in more detail in figures 2 And 3 .

[0014] As a preliminary step, an axial direction is defined, a radial direction which is orthogonal to the axial direction and a circumferential direction which is orthogonal to the axial and radial directions.

[0015] The turbomachine 100 extends along a longitudinal axis X in the axial direction and comprises, from upstream AM to downstream AV in the direction of flow of the gases in the axial direction, a fan 102, a low-pressure compressor 103, a high-pressure compressor 104, a combustion chamber 105, a high-pressure turbine 106, a low-pressure turbine 107 and an exhaust nozzle 108 comprising in particular the ejection cone 101.

[0016] The turbomachine 100 further comprises, downstream of the fan 102, an annular primary flow channel 109, called a primary vein, along which a primary gas flow circulates and passes through the low-pressure compressor 103, the high-pressure compressor 104, the combustion chamber 105, the high-pressure turbine 106 and the low-pressure turbine 107, and an annular secondary flow channel 110, called a secondary vein, surrounding the primary vein 109 and along which a secondary gas flow circulates. The primary and secondary gas flows mix at the exhaust nozzle 108.

[0017] The turbomachine 100 also comprises, downstream of the low-pressure turbine 107 and upstream of the exhaust nozzle 108, an exhaust casing 111 comprising a radially internal shell 112 and a radially external shell 113 defining an annular space forming, downstream of the low-pressure turbine 107, a part of the primary flow path 109.

[0018] The ejection cone 101 comprises, for example, an annular upstream part 114 connected to the radially internal shell 112 of the exhaust casing 111 and comprising the assembly 10 according to the invention, and a conical downstream part 115 connected to the upstream part 114.

[0019] The assembly 10 according to the invention is shown in more detail in figures 2 to 14 It comprises a first annular wall 11, first partitions 12 and second partitions 13.

[0020] The first wall 11 is centered on the longitudinal axis X. The first wall 11 may have, from upstream AM to downstream AV, a first generally cylindrical portion 14, a second generally frustoconical portion 15 diverging towards downstream AV and a third generally frustoconical portion 16 converging towards downstream AV ( figure 4 ). The first wall 11 may further be fixed, upstream, to the radially internal shell 112 of the exhaust casing 111, in particular by means of an upstream end 17 of its first portion 14. The first wall 11 may also be fixed, downstream, to the downstream part 115 of the ejection cone 101. The first wall 11 is for example made of a ceramic matrix composite material. More generally, it may be made with any type of material capable of withstanding temperatures greater than or equal to 450°C.

[0021] The first and second partitions 12, 13 extend substantially perpendicularly from the first wall 11 between a radially internal end edge 121, 131, arranged opposite the first wall 11, and a radially external end edge 122, 132 ( figures 3 to 5 ). The first and second partitions 12, 13 are arranged radially outside the first wall 11. The first and second partitions 12, 13 may be made from metal, for example titanium or Inconel ®<. This is for example Inconel ®< 625 or Inconel ®< 718. The first and second partitions 12, 13 may also be made from composite material, in particular from ceramic matrix composite material. More generally, they may be made with any type of material capable of withstanding temperatures greater than or equal to 450°C.

[0022] The first partitions 12 further extend generally in the axial direction and are distributed circumferentially around the first wall 11, in particular regularly ( figure 3 ). The first partitions 12 are for example identical in shape and dimensions.

[0023] The second partitions 13 extend generally in the circumferential direction between the pairs of adjacent first partitions 12 ( figure 3 ). These second partitions 13 are curved partitions, comprising at least one arcuate portion in the axial direction upstream or downstream, extending in the circumferential direction.

[0024] The second partitions 13 are further distributed circumferentially around the annular wall 11, in particular regularly, in at least one circumferential row 18, 19, for example two circumferential rows 18, 19 spaced axially from one another. The second partitions 13 of the most upstream circumferential row 18 may extend from the first portion 14 of the first wall 11, while the second partitions 13 of the most downstream circumferential row 19 may extend from the second portion 15 of the first wall 11. The second partitions 13 of the same circumferential row 18, 19 are for example identical in shape and dimensions.

[0025] The second partitions 13 can be fixed, at each of their circumferential ends 20a, to that of the first and second partitions 12, 13 which is circumferentially closest to it, in particular by riveting ( Figure 5). The first and second partitions 12, 13 thus form a solid assembly or a single piece. The circumferential ends 20a of each of the second partitions 13 are for example formed by tabs extending generally axially from a central core 20b of said second partition 13.

[0026] Along a circumferential row 18, 19, one or more second partitions 13 may be arranged between each pair of adjacent first partitions 12. Thus, for example, when a single second partition 13 of a circumferential row 18, 19 is arranged between a pair of adjacent first partitions 12, each of its circumferential ends 20a is fixed to one of the first partitions 12 of said pair. When two second partitions 13 of a circumferential row 18, 19 are arranged between a pair of adjacent first partitions 12, one of the circumferential ends 20a of said second partitions 13 is fixed to one of the first partitions 12 of said pair, and their other circumferential ends 20a are fixed to each other.

[0027] The first wall 11, the first partitions 12 and the second partitions 13 further define between them a plurality of acoustic boxes 21 distributed around the first wall 11 in at least one circumferential row 22, 23, for example two circumferential rows 22, 23 succeeding each other axially. The acoustic boxes 21 are in particular designed to absorb at least part of the noise generated by the combustion of the gases in the combustion chamber 105, in particular the low-frequency noise, typically between 300 Hz and 1000 Hz.

[0028] Each of the acoustic boxes 21 is thus delimited radially inwards by the first wall 11, circumferentially by a pair of first partitions 12 and axially by one or more second partitions 13. For example, the acoustic boxes 21 of the most upstream circumferential row 22 are delimited axially, towards the upstream AM, by one or more second partitions 13 located between said pair of first partitions 12 and belonging to the most upstream circumferential row 18 and, towards the downstream AV, by one or more second partitions 13 located between said pair of first partitions 12 and belonging to the most downstream circumferential row 19. The acoustic boxes 21 of the most downstream circumferential row 23 are delimited axially towards the upstream AM by the second partitions 13 of the most downstream circumferential row 19. They can also be delimited towards the downstream AV by the first wall 11, in particular its second portion 15.

[0029] The acoustic boxes 21 can also be delimited radially outwards by the second wall 24 which is centered on the longitudinal axis X ( figures 2 And 4 ). The second wall 24 joins for example the first wall 12 downstream of the first partitions 12, in particular at the level of the third portion 16 of the first wall 12. The second wall 24 is multi-perforated so as to allow part of the acoustic energy of the primary vein 109 to pass into the acoustic boxes 21 and thus ensure the attenuation of the noise generated by the combustion of the gases in the combustion chamber 105. The second wall 24 is for example fixed, downstream, to the conical downstream part 115 of the ejection cone 101. The second wall 24 can be made of a ceramic matrix composite material. More generally, it can be made with any type of material capable of withstanding temperatures greater than or equal to 450 °C.

[0030] The dimensions and conformation of the first wall 11, the first partitions 12, the second partitions 13 and, where appropriate, the second wall 24 are such that the acoustic boxes 21 have large volumes, in particular volumes of between 3000 cm 3 and 5000 cm 3 .

[0031] For example ( figures 4 And 5), a volume V1 of the acoustic boxes 21 of the most upstream circumferential row 22 is substantially equal to 3710cm 3< , while a volume V2 of the acoustic boxes 21 of the most downstream circumferential row 23 is substantially equal to 4230cm 3< . For this, a height H1 of the central core 20b of the second partitions 13 of the most upstream circumferential row 18 is for example between 50 and 60mm inclusive, in particular substantially equal to 55mm. A height H2 of the central core 20b of the second partitions 13 of the most downstream circumferential row 19 is for example between 110 and 135mm inclusive, in particular substantially equal to 123mm. “Height” is understood to mean a dimension of the central core 20b of the second partitions 13, taken perpendicular to the first wall 11, between their radially internal 131 and external 132 end edges.A distance D1 between each pair of adjacent first partitions 12, taken at the level of the radially external end edge 122 of said first partitions 12 and at the level of the most upstream circumferential row 18 of second partitions 13, is for example between 190 and 230 mm, in particular substantially equal to 210 mm. A distance D2 between each pair of adjacent first partitions 12, taken at mid-height between their radially internal 121 and external 122 end edges and at the level of the most downstream circumferential row 19 of second partitions 13, is for example between 225 and 275 mm, in particular substantially equal to 250 mm.A distance D3, taken along the axial direction, between the most upstream point of the radially external end edge 132 of the second partitions 13 of the most upstream circumferential row 18 and the most upstream point of the radially external end edge 132 of the second partitions 13 of the most downstream circumferential row 19, is for example between 110 and 140 mm, in particular substantially equal to 124 mm. A distance D4, taken along the axial direction, between the most upstream point of the radially external end edge 132 of the second partitions 13 of the most upstream circumferential row 18 and the most upstream point of the radially internal end edge 131 of the second partitions 13 of the most downstream circumferential row 19, is for example between 165 and 200 mm, in particular substantially equal to 183 mm.

[0032] According to a first aspect of the invention, the second partitions 13 are curved partitions comprising at least one arcuate portion 25a, 25b in the axial direction towards the upstream AM or towards the downstream AV ( figures 2 to 11 ), extending in the circumferential direction. The arcuate portion(s) 25a, 25b are in particular made in the central core 20b of the second partitions 13. This makes it possible on the one hand to limit the forces induced by thermal expansion in the acoustic boxes 21, in particular in the circumferential direction, for example when the exhaust gases of the turbomachine 100 are at high temperature such as temperatures ranging from 600 to 650°C. This also makes it possible to reduce the axial forces which are exerted on the second partitions 13 due to the pressure of the gases in the acoustic boxes 21 and therefore which are to be supported by the acoustic boxes 21, and thus to improve the mechanical strength of the acoustic boxes 21.

[0033] The arcuate portions 25a, 25b of the second partitions 13 of each circumferential row 18, 19 define in particular a pattern repeating along said circumferential row 18, 19.

[0034] According to an embodiment of this first aspect of the invention, the pattern of the arcuate portions 25a, 25b of the second partitions 13 of at least one of the circumferential rows 18, 19 consists of an arcuate portion 25a towards the upstream AM or an arcuate portion 25b towards the downstream AV. Thus, all the arcuate portions 25a, 25b of the second partitions 13 of said circumferential row 18, 19 are oriented in the same axial direction, towards the upstream AM or towards the downstream AV. On the figures 3 , 5 , 6 And 11 , the arcuate portions 25a of the second partitions 13 of the two circumferential rows 18, 19 are oriented upstream AM.

[0035] According to an embodiment of this first aspect of the invention, the pattern of the arcuate portions 25a, 25b of the second partitions 13 of at least one of the circumferential rows 18, 19 consists of an arcuate portion 25a towards the upstream AM followed by an arcuate portion 25b towards the downstream AV, so as to obtain an alternation of an arcuate portion 25a towards the upstream AM and an arcuate portion 25b towards the downstream AV along the entire length of said circumferential row 18, 19. On the figures 7 And 8 , the two circumferential rows 18, 19 comprise such an alternation of an arcuate portion 25a towards the upstream AM and an arcuate portion 25b towards the downstream AV.

[0036] According to an embodiment of this first aspect of the invention, the pattern of the arcuate portions 25a, 25b of the second partitions 13 of at least one of the circumferential rows 18, 19 consists of two arcuate portions 25a towards the upstream AM followed by two arcuate portions 25b towards the downstream AV, so as to obtain an alternation of two arcuate portions 25a towards the upstream AM and two arcuate portions 25b towards the downstream AV along the entire length of said circumferential row 18, 19. On the figure 9 , the two circumferential rows 18, 19 comprise such an alternation of two arcuate portions 25a towards the upstream AM and two arcuate portions 25b towards the downstream AV.

[0037] According to an embodiment of this first aspect of the invention, along at least one of the circumferential rows 18, 19, two or more successive arcuate portions 25a, 25b are interposed between each pair of adjacent first partitions 12. This is for example the case of the circumferential row 18 furthest upstream on the figures 3 And 5 where two arcuate portions 25a, 25b towards the upstream AM are interposed between each pair of first adjacent partitions 12 and the two circumferential rows 18, 19 on the figure 10 where two arcuate portions 25a are oriented in the same axial direction, towards the upstream AM, between each pair of first adjacent partitions 12. This is for example also the case of the two circumferential rows 18, 19 on the figures 8 and 9 where two arcuate portions 25a, 25b are oriented alternately upstream AM and downstream AV between each pair of first adjacent partitions 12.

[0038] According to an embodiment of this first aspect of the invention, each second partition 13 of at least one of the circumferential rows 18, 19 carries a single arcuate portion 25a, 25b. This is for example the case on the figures 3 , 5 , 6, 7 , 10 and 11 .

[0039] According to an embodiment of this first aspect of the invention, each second partition 13 of at least one of the circumferential rows 18, 19 carries an arcuate portion 25a towards the upstream AM and an arcuate portion 25b towards the downstream AV. This is for example the case on the figures 8 and 9 .

[0040] For example, a distance D5, taken in an axial plane and at the level of the radially external end edge 132 of each second partition 13, between a vertex of the or one of the arcuate portions 25a, 25b of said second partition 13 and the circumferential ends of the central core 20b of said second partition 13 is greater than or equal to 20mm ( Figure 5). The term “apex” is understood to mean the point of the radially external end edge 132 of the second partition 13 furthest upstream in the case of an arcuate portion 25a towards the upstream AM and furthest downstream in the case of an arcuate portion towards the downstream AV.

[0041] Each second partition 13 may also have a transition radius R between each of its circumferential ends 20a and the top of the arcuate portion 25a 25b of said second partition 13, which is adjacent to them, greater than or equal to 20mm ( Figure 5 ).

[0042] According to an embodiment of this first aspect of the invention, the first partitions 12 are corrugated in the axial direction. This is for example the case on the figure 11 .

[0043] According to a second aspect of the invention which is combined with the first aspect and which is illustrated in figures 12 to 14, the assembly formed by the first and second partitions 12, 13 is fixed to the first wall 11 by means of first fixing members 30 arranged upstream and second fixing members 31 arranged downstream. The first and second fixing members 30, 31 form point mechanical connections, such as fittings. The first fixing members 30 are further circumferentially offset relative to the second fixing members 31. The first fixing members 30 and the second fixing members 31 are thus misaligned in the axial direction. It is understood here that the assembly 10 is devoid of other means for fixing the first and second partitions 12, 13 to the first wall 11. In this way, the first partitions 12 can only be fixed to the first wall 11 upstream or downstream, but not both, which allows the first partitions 12 to expand freely, in particular in the axial direction.This improves the mechanical resistance of the acoustic boxes 21.

[0044] The first fixing members 30 are mounted between first and / or second partitions 12, 13 and an upstream portion 32 of the first wall 11. The upstream portion 32 is for example formed in the first portion 14 of the first wall 11. The first fixing members 30 may furthermore be generally circumferentially aligned with each other.

[0045] The second fixing members 31 are mounted between first and / or second partitions 12, 13 and a downstream portion 33 of the first wall 11. The downstream portion 33 is for example formed in the second portion 15 of the first wall 11. The second fixing members 31 may furthermore be generally circumferentially aligned with each other.

[0046] Each first partition 12 is for example mounted on the first wall 11, either upstream by one or more first fixing members 30, or downstream by one or more second fixing members 31. In other words, first or second fixing members 30, 31 are for example mounted between each first partition 12 and the first wall 11. On the figures 12 and 13 , each first partition 12 is mounted on the first wall 11 by means of one or two second fixing members 31. On the figure 14 , the first partitions 12 are alternately mounted on the first wall 11 upstream by means of two first fixing members 30 and downstream by means of two second fixing members 31.

[0047] According to an embodiment of this second aspect of the invention, the first fixing members 30 are mounted between second partitions 13 of the most upstream circumferential row 18 and the upstream portion 32 of the first wall 11. This is for example the case of the first fixing members 30 on the figures 12 and 13 The first fixing members 30 can also be mounted on one side only, in particular on the downstream side as is the case on the figures 12 and 13 , of said second partitions 13 in the axial direction. Each first fixing member 30 can also be separated from the first fixing members 30 which are circumferentially adjacent to it, by one or two first partitions 12. On the figure 12 , a first fixing member 30 is arranged in each acoustic box 21 of the most upstream circumferential row 22. On the figure 13, a first fixing member 30 is arranged in an acoustic box 21 out of two of the most upstream circumferential row 22.

[0048] Alternatively, the first fixing members 30 are mounted between first partitions 12 and the upstream portion 32 of the first wall 11, in particular upstream of the circumferential rows 18, 19 of second partitions 13. This is for example the case of the first fixing members 30 on the figure 14 . Of course, in this case, no second fixing member 31 can be mounted between said first partitions 12 and the downstream portion 33 of the first wall 11. The first fixing members 30 can furthermore be mounted on each side of said first partitions 12 in the circumferential direction.

[0049] According to an embodiment of this second aspect of the invention, the second fixing members 31 are mounted between first partitions 12 and the downstream portion 33 of the first wall 11, in particular downstream of the circumferential rows 18, 19 of second partitions 13. This is for example the case on the figures 12 to 14 . The second fixing members 31 can be mounted on each side of said first partitions 12 in the circumferential direction. This is for example the case of the second fixing members 31 on the figures 12 And 14. As a variant, each second fixing member 31 is mounted on only one side of said first partitions 12 in the circumferential direction, in particular opposite another second fixing member 31. The second fixing members 31 can thus be arranged in an acoustic box 21 on two or more of the most downstream circumferential row 23. This is for example the case of the second fixing members 31 on the figure 13 .

Claims

1. A set (10) for an ejection cone (101) of an aircraft turbomachine (100), comprising a first annular wall (11) centred on a longitudinal axis (X) of axial direction oriented from upstream to downstream, a plurality of first partitions (12) and second partitions (13) extending substantially perpendicularly from the first wall (11), wherein the first partitions (12) extend generally in the axial direction and are distributed circumferentially around the first wall (11), wherein the second partitions (13) extend generally in a circumferential direction between the pairs of adjacent first partitions (12) and are distributed circumferentially around the annular wall (11) in at least one circumferential row (18, 19), and wherein the first wall (11), the first partitions (12) and the second partitions (13) define therebetween a plurality of acoustic enclosures (21) distributed around the first wall (11), the set (10) being characterised in that the second walls (13) are bent walls comprising at least one portion (25a, 25b) arched in the axial direction upstream or downstream.

2. The set (10) according to claim 1, wherein the arched portions (25a, 25b) of the second partitions (13) of at least one of the circumferential rows (18, 19) define a pattern repeating along said circumferential row (18, 19) and wherein the pattern of the arched portions (25a, 25b) of the second partitions (13) of said circumferential row (18, 19) consists of a portion arched upstream (25a) or downstream (25b), such that all the arched portions (25a, 25b) of the second partitions (13) of said circumferential row (18, 19) are oriented in a same axial direction, upstream (AM) or downstream (AV).

3. The set (10) according to claim 1 or claim 2, wherein the arched portions (25a, 25b) of the second partitions (13) of at least one of the circumferential rows (18, 19) define a pattern repeating along said circumferential row (18, 19) and wherein the pattern of the arched portions (25a, 25b) of the second partitions (13) of said circumferential row (18, 19) consists of a portion (25a) arched upstream (AM) followed by a portion (25b) arched downstream (AV), so as to obtain an alternation of a portion (25a) arched upstream (AM) and a portion (25b) arched downstream (AV) all along said circumferential row (18, 19).

4. The set (10) according to one of claims 1 to 3, wherein the arched portions (25a, 25b) of the second partitions (13) of at least one of the circumferential rows (18, 19) define a pattern repeating along said circumferential row (18, 19) and wherein the pattern of the arched portions (25a, 25b) of the second partitions (13) of said circumferential row (18, 19) consists of two portions (25a) arched upstream (AM) followed by two portions (25b) arched downstream (AV), so as to obtain an alternation of two portions (25a) arched upstream (AM) and two portions (25b) arched downstream (AV) all along said circumferential row (18, 19).

5. The set (10) according to one of claims 1 to 4, wherein, along at least one of the circumferential rows (18, 19), two or more successive arched portions (25a, 25b) are interposed between each pair of adjacent first partitions (12).

6. The set (10) according to one of claims 1 to 5, wherein each second partition (13) of at least one of the circumferential rows (18, 19) carries a single arched portion.

7. The set (10) according to one of claims 1 to 6, wherein each second partition (13) of at least one of the circumferential rows (18, 19) carries a portion (25a) arched upstream (AM) and a portion (25b) arched downstream (AV).

8. The set (10) according to one of claims 1 to 7, wherein an assembly formed by the first and second partitions (12, 13) is attached to the first wall (11) by means of first attachment members (30) arranged upstream and second attachment members (31) arranged downstream, and wherein the first attachment members (30) are offset circumferentially relative to the second attachment members (31).

9. An ejection cone (101) for an aircraft turbomachine (100) comprising a set (10) according to one of claims 1 to 8.

10. An aircraft turbomachine (100), comprising an ejection cone (101) according to claim 9.