Annular housing of a turbomachine and its manufacturing process.

Abstract

The present invention relates to an annular housing (1) of a turbomachine, comprising a body (2) made of organic matrix composite material, this body (2) comprising a shaft (21) with longitudinal axis X-X', provided at its upstream (211) and downstream (212) ends, respectively, with an upstream annular radial flange (22) and a downstream annular radial flange (23).This housing is remarkable in that it comprises one or two reinforcing pieces (3, 4), made of metal and having an L-shaped cross-section, so as to present a radial arm (30, 40) and an axial arm (31, 41), and in that said reinforcing piece (3, 4) is fixed to the body (2) so that its radial arm (30, 40) is in contact with the outer face (221, 231) of one of the two upstream (22) and downstream (23) radial flanges, and that its axial arm (31, 41) is in contact with the end (211, 212) of the cylindrical shaft (21) from which extends the radial flange (30, 40) against which said reinforcing piece (3, 4) is fixed. Figure for the abbreviation: Fig. 5.

Description

Description Title of the invention: Annular turbomachine casing and its manufacturing process. FIELD OF THE INVENTION.

[0001] = The invention lies in the field of parts made from composite materials and used in the field of aeronautics.

[0002] The present invention relates to an annular turbomachine casing, and in particular an annular fan casing of a turbomachine. The invention also relates to the manufacturing process of this casing. STATE OF THE ART.

[0003] = A turbomachine fan has the function of compressing all of the air which enters the turbomachine. A large part of this air constitutes the secondary flow and the rest of the air constitutes the primary flow. Classically, the primary flow successively passes through a low pressure compressor attached to the blower, a high pressure compressor, a combustion chamber, a high pressure turbine and finally a low pressure turbine, before being ejected outside the turbomachine.

[0004] As can be seen in the attached [Fig.1], the fan casing A is a part annular, with a central longitudinal axis XX°. The fan casing A, also known under the name of "fan casing" or "retention casing" has the following main functions:

[0005] to ensure the continuity of the air stream between the air intake sleeve B of the aircraft and the engine, and

[0006] — * to ensure the retention of debris, in the event of ingestion of foreign objects, such as birds or others (known under the English name of “FOD: Foreign Object Damage”) or in the event of loss of fan blades (known as English of “FBO: Fan Blade Out”).

[0007] — The fan casing A also has secondary functions, which are among others

[0008] * to ensure mechanical continuity (forces and moments) between the inlet sleeve air B and the intermediate casing shell C,

[0009] * to allow the fixing of the vein panels, which are successively from upstream (left in [Fig.1]) downstream (right in [Fig.1]) relative to the direction air flow inside the turbomachine: the upstream acoustic shell D, the abradable support cartridge E and the downstream acoustic panel F,

[0010] — * to allow the fixing of various equipment and supports,

[0011] * to meet fire and leak specifications, including fluid leaks circulating in the pipes located around the casing, * to allow the continuity of the electrical current for lightning resistance. The latest generation of fan casings are generally made of CMO composite materials (for "Organic Matrix Composites"), which allows them to perform all the aforementioned functions of a fan casing, while being lighter than if they were made of metal. The weight saving thus obtained is crucial in the aeronautics field, because it allows aircraft manufacturers to save fuel, while fuel is one of the largest expenditure items in the air transport field. Organic matrix composite parts are composed of a fiber reinforcement and a matrix. The fiber reinforcement is a fibrous texture that is an ordered assembly of fibers, for example carbon, glass, or aramid fibers. The matrix is ​​usually an organic resin that impregnates the fiber texture before the assembly cures. The fibrous texture can thus have a shape corresponding to that of the final composite part. Alternatively, it can also be shaped subsequently, after mixing with the resin but before the polymerization (hardening) of the latter. As a purely illustrative example, document EP 1961 923 provides an example of a method for manufacturing a fan casing made of an organic matrix composite. To ensure the functions described above while minimizing mass, the fan casing is optimized by zones, as shown in the attached [Fig.2]. There are three main zones: the flanges (namely the upstream flange G and the downstream flange H), the structural zones (namely the upstream structural zone I and the downstream structural zone J) and the retention zone K. The upstream flange G is connected by bolts to the air inlet sleeve B, while the downstream flange H is connected by bolts to the intermediate casing shell C, these connections being made by the aircraft manufacturer. These upstream flanges G and downstream flanges H must have good thermomechanical resistance in static mode and withstand tensile, compression and shear tests. The upstream structural zones I and downstream J of the fan casing A are thinned in order to reduce the mass of this casing. They must have good mechanical resistance in dynamic mode. Finally, the retention zone K must have good mechanical strength in static and dynamic mode and it is generally thicker than the structural zones. The fan casing, due to the material it is made of and its skin thickness, is therefore sized to withstand the impact of a released blade without suffering critical rupture, while allowing the fragments to be retained. potential follower vanes and / or other debris that will be ingested inside the engine. The retention capacity of a CMO organic matrix composite fan casing is ensured, among other things, by the quantity of fibers used, by the nature of these fibers and by their arrangement within the retention zone K. However, in the case of loss of a fan blade, when the blade strikes the fan casing, a shock wave is produced and propagates from the point of impact to all areas of the casing. In certain cases, this shock wave generates such deformations of the casing that the other areas are subjected to high compressive stress. The current structure of the fiber reinforcement of an organic matrix composite (OMC) fan casing is very effective in terms of the retention function of this casing. However, it is not necessarily optimized in areas of the fan casing other than those in the retention zone K. Also, during operation of the turbomachine, this fan casing may be exposed to high temperatures above 100°C, for example following a fire or a leak from a compressed air pipe in this casing. This exposure to high heat has an impact on two levels: "we observe a degradation of the mechanical properties of the fan casing, which makes it incapable of ensuring in particular its function of mechanical continuity with the surrounding parts, * the expansion differential between the air inlet sleeve B or the intermediate casing shell C, which are metal parts, and the blower casing A made of organic matrix composite CMO, is very significant. As a purely illustrative example, such an expansion differential is of the order of 1 to 4 between the composite material and titanium. This results in a significant bending moment at the flanges, as can be seen in the diagrams of attached figures 3 and 4, which respectively represent the state of a casing A and its flanges, at the nominal operating temperature and at a temperature above 100 °C. The majority of mechanical loads applied to the fan casing A are concentrated at the flanges G and H of this casing and these are mainly subjected to tension and compression. The very constitution of the composite material (composed of fibers and a matrix), used for the manufacture of the fan casing, makes the latter particularly vulnerable to compression, under high temperatures, because when the resin reaches its glass transition temperature, it begins to soften considerably and no longer ensures its function of cohesion with the fibers. STATEMENT OF THE INVENTION. An aim of the invention is to propose an annular fan casing and more generally an annular turbomachine casing, made of organic matrix composite CMO, which does not have the aforementioned drawbacks. To this end, the invention relates to an annular casing of a turbomachine, in particular an annular fan casing of a turbomachine, comprising a body made of organic matrix composite material, this body comprising a cylindrical or frustoconical barrel, with a longitudinal axis XX”, provided at its upstream and downstream ends, respectively, with an upstream annular radial flange and a downstream annular radial flange. According to the invention, this casing comprises at least one reinforcing piece, made of metal, in particular titanium, this reinforcing piece being an annular piece or in the form of an annular segment, said reinforcing piece has on at least part of its circumference, an L-shaped cross-section, so as to have a radial branch and an axial branch, and said reinforcing piece is fixed to the body, so that its radial branch is in contact with the outer face of one of the two upstream and downstream radial flanges and that its axial branch is in contact with the end of the barrel from which extends the radial flange against which said at least one reinforcing piece is fixed. Thanks to these features of the invention, a part of the flange (thanks to the radial branch of the reinforcement piece) is made of metal and there is thus a smooth transition between the composite material of the barrel and the neighboring metal parts to which this casing is intended to be fixed. This avoids a strong discontinuity of thermal expansion between the casing and the neighboring metal parts, such as the air inlet sleeve or the intermediate casing shell. According to other advantageous and non-limiting characteristics of the invention, taken alone or in combination: - the upstream annular radial flange and the downstream annular radial flange extend radially outwards and in that the axial branch of the reinforcing piece is fixed in contact with the internal face of the barrel; - the reinforcement piece is annular and has an L-shaped cross-section over its entire circumference; - the casing comprises several annular reinforcement pieces in the form of annular segments, and in that these annular segments are fixed to the body circumferentially end to end; - the casing comprises several annular reinforcing pieces in the form of annular segments, and in that these annular segments are fixed to the body so as to be spaced from one another or from one another; - the reinforcement piece has at least two parts with an L-shaped cross-section, joined by a junction part; - said junction part has the following form: of an axial tongue which extends in the extension of the axial branches of the two parts with L-shaped cross-section joined by said axial tab, this axial tab having a width less than or equal to the width axial branches of the two parts with L-shaped cross-section, joined by said axial tab, of a radial tongue which extends in the extension of the radial branches of the two parts with L-shaped cross-section, joined by said tab radial, this radial tongue having a height less than or equal to the height of the radial branches of the two parts with L-shaped cross-section, joined by said radial tab, of an L-shaped bracket equipped with a radial branch and an axial branch, the height of the radial branch of the square being less than the height of the radial branches of the two parts with L-shaped cross-section, joined by said square and the width of the axial branch of the square being less than the width of the axial branches of the two L-shaped cross-section parts, joined by said bracket; - the width of the axial branch of the reinforcement piece is equal to or greater than the height of the radial branch of the same reinforcement piece; - the height of the radial branch of the reinforcing piece is such that it covers the entire outer face of the upstream or downstream radial flange in contact with which it is located; - the barrel of the body has at least one of its two upstream and downstream ends, a thickness less than that of the rest of the barrel, so as to define an annular recess and in that this annular recess is sized so as to receive the axial branch of the reinforcement piece and that this axial branch is flush with the face of the barrel in which this recess is formed; - the casing comprises at least one metal counter-plate, fixed against the inner face of one of the two upstream and downstream radial flanges of the body, this counter-plate being an annular counter-plate or having the shape of an annular segment, and this counter-plate having a constant or variable height and a height less than or equal to the height of the inner face of the upstream or downstream radial flange of the body against which this counter-plate is fixed; - said reinforcing piece and possibly said counterplate is fixed or are fixed to the body by cold gluing, by co-injection and / or by mechanical assembly, in particular using rivets; Finally, the invention also relates to a method of manufacturing a casing annular as mentioned above. According to the invention, this method comprises steps of manufacturing said at least one reinforcing part, of optionally manufacturing said counter-plate if the latter is present, and of assembling the body, the reinforcing part and optionally the counter-plate by cold gluing or by co-injection and / or mechanical assembly, in particular using rivets, so as to obtain said annular casing. DESCRIPTION OF FIGURES. Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which: [Fig.1] is a longitudinal sectional view of a portion of an annular fan casing. [Fig.2] is a diagram showing different areas of the annular casing of [Fig.1]. [Fig.3] is a diagram showing an annular fan casing. [Fig.4] is a diagram showing this same annular fan casing, subjected to high temperatures. [Fig.5] is a perspective view of a part of an annular turbomachine casing according to the invention. [Fig.6] is a perspective view of reinforcing pieces according to the invention, having the form of annular segments. [Fig.7] is a perspective view of an alternative embodiment of one of the reinforcement pieces of [Fig.6]. [Fig.8] is a perspective view of a part of an annular turbomachine casing according to the invention. DETAILED DESCRIPTION OF THE INVENTION. The annular casing 1 according to the invention will now be described in connection with Figures 5 to 8. In the remainder of the description, this casing will be described as a fan casing of a turbomachine. However, it could also be any annular casing of a turbomachine, that is to say an annular casing arranged at any point of a turbomachine. The casing 1 comprises a body 2, made of a composite material, in particular an organic matrix composite (OMC) material. Such a material comprises fibers bonded together by a thermosetting resin. This body 2 comprises a cylindrical or truncated cone 21, with a longitudinal axis XX, and this barrel comprises two ends, namely an upstream end 211 and a downstream end 212, the upstream and downstream being defined relative to the direction of air flow inside this body (from left to right in figures 5 to 8). Furthermore, the barrel 21 has an internal face 213, oriented towards the longitudinal central axis XX° and an opposite external face 214. The upstream end 211 of the barrel 21 is extended by an upstream annular radial flange 22 and the downstream end 212 of this barrel is extended by a downstream annular radial flange 23. Preferably, and as can be seen in the figures, the two radial flanges, respectively upstream 22 and downstream 23, extend radially outwards, relative to the longitudinal axis XX°, (i.e. towards the top of the figures). They could, however, extend radially inwards. The two upstream 22 and downstream 23 radial flanges each have an outer face 221, respectively 231 and an inner face 222, respectively 232. The inner faces 222 and 232 are arranged opposite each other. Furthermore, the annular casing 1 comprises at least one metal reinforcing piece, preferably several. Preferably, the metal constituting the reinforcement part(s) is titanium. Such a material offers a good compromise between coefficient of expansion / mass / mechanical properties. According to a first embodiment of the invention shown in [Fig.5], the reinforcing piece is annular (therefore a single piece) and the casing 1 is here provided with two annular reinforcing pieces, referenced respectively 3 for the upstream piece and 4 for the downstream piece. Each reinforcing piece has, over at least part of its circumference and in the example shown in [Fig.5], over its entire circumference, an L-shaped cross-section. Thus, the upstream reinforcing piece 3 has a radial branch 30 and an axial branch 31, while the downstream reinforcing piece 4 has a radial branch 40 and an axial branch 41. The upstream reinforcement piece 3 is fixed to the body 2, so that its radial branch 30 is located in contact with the external face 221 of the upstream flange 22 and its axial branch 31 is located in contact with the upstream end 211 of the barrel 21. The downstream reinforcement piece 4 is fixed to the body 2, so that its radial branch 40 is located in contact with the external face 231 of the downstream flange 23 and its axial branch 41 is located in contact with the downstream end 212 of the barrel 21. In the preferred embodiment of the invention, in which the two upstream 22 and downstream 23 annular flanges extend radially outwards, then the axial branch 31, 41 of each reinforcing piece 3, 4 is fixed in contact with the internal face 213 of the barrel 21. According to a second variant embodiment of the invention shown in [Fig.6], the reinforcing piece can take the form of an annular segment (ring segment). In this figure, several annular segments (referenced 3' or 4' depending on whether they are arranged against the upstream flange 22 or respectively the downstream flange 23 of the body 2). In this figure, these annular segments 3°, respectively 4°, are assembled together circumferentially end-to-end. They thus form a 360° crown. However, these annular segments 3', respectively 4', can also be arranged circumferentially against the flanges 22 or 23, but being spaced from each other. Such an arrangement allows an overall weight saving of the casing and therefore of the turbomachine, thus reducing fuel consumption. In [Fig.6], the annular segment has an L-shaped cross-section along its entire length (along its entire circumference portion). However, the annular segment 3°, 4° (as shown in [Fig.7]) or the annular reinforcing piece 3, 4 (as is not visible in the figures) may have at least two parts 7 with an L-shaped cross-section (i.e. with a radial branch 30, 40 and an axial branch 31, 41), joined together by a joining part 8. As an example, it can be seen in [Fig.7] that the annular segment comprises four parts 7 with L-shaped cross-section and three joining parts 8. The joining part 8 can have different shapes to choose from. It may for example be an axial tongue 81 which extends in the extension of the axial branches 31, 41 of the two parts 7 with L-shaped cross-section, joined by this tongue 81. It will be noted that this axial tongue 81 preferably has a width L2 less than or equal to the width L1 of the axial branches 31, 41 of the two parts 7 with L-shaped cross-section joined by said axial tongue 81. The joining part 8 may also be a radial tongue 82 which extends in the extension of the radial branches 30, 40 of the two parts 7 with L-shaped cross-section, joined by said tongue 82. It will be noted that this radial tongue 82 preferably has a height H2 less than or equal to the height H1 of the radial branches 30, 40 of the two parts 7 with L-shaped cross-section joined by said tongue 82. Finally, the joining part 8 may also be an L-shaped bracket 83 provided with a radial branch 830 and an axial branch 831, the height H3 of the radial branch 830 of the bracket 83 being less than the height H1 of the radial branches 30, 40 of the two parts 7 with L-shaped cross-section, joined by said bracket 83 and the width L3 of the axial branch 831 of the bracket 83 being less than the width L1 of the axial branches 31, 41 of the two parts 7 with L-shaped cross-section joined by said bracket 83. These different junction zones 81, 82, 83 also make it possible to reduce the overall mass of the reinforcement part. In [Fig.7], the different possible shapes of the junction part 8 have been represented on a single segment, however, it is possible to have only one alone on the same segment. Furthermore, whatever the shape of the reinforcing piece, preferably, and in order to ensure good fixing between this reinforcing piece 3, 4, 3°, 4' and the barrel 21, the width LI of its axial branch 31, 41 is equal to or greater than the height H1 of its radial branch 30, 40. Also preferably, and in order to fully play its role of mechanical reinforcement, the height HI of the radial branch 30, 40 of the reinforcement piece 3, 4, 3°, 4 is such that it covers the entire outer face 221, 231 of the upstream radial flange 22, respectively downstream 23, in contact with which it is located. Finally, advantageously, the annular casing | according to the invention can also comprise at least one metal counter-plate, fixed against the internal face of one of the two radial flanges 22, 23 of the body 2. According to a first embodiment of the invention shown in [Fig. 5], the counter plate is annular (i.e. it has the shape of a flat ring of small thickness). In this figure, the casing 1 is provided with two annular counter plates, namely an upstream counter plate S fixed against the inner face 222 of the upstream flange 22 and a downstream counter plate 6 fixed against the inner face 232 of the downstream flange 23. According to a second embodiment of the invention, visible in [Fig.8], the counter plate may have the shape of an annular segment. In this figure, several annular counter plate segments are thus shown (referenced 5' or 6° depending on whether they are arranged against the upstream flange 22 or respectively the downstream flange 23 of the body 2). In this figure, the annular counter plate segments 5', respectively 6°, are assembled circumferentially end-to-end. They thus form a 360° crown. However, these annular counter plate segments 5', respectively 6°, can also be arranged circumferentially against the flanges 22 or 23, but being spaced from each other. Such an arrangement allows an overall weight saving of the casing and therefore of the turbomachine, thus reducing fuel consumption. It will be noted that the height H4 of the counter-plate 5, 6, 5', 6° is preferably identical to the height HS of the inner face 222, 232 of the upstream radial flange 22 or downstream 23 of the body 2 against which this counter-plate 5, 6, 5°, 6° is fixed, so as to reinforce the mechanical strength of this flange 22 or 23. However, in order to reduce the mass of the casing, this height H4 may be less than HS or the height H4 may vary over the length of the counter-plate so as to be in places only less than H5. Thanks to this or these counter-plate(s) 5, 6, 5', 6°, the flange 22, 23 is thus arranged between two metal plates (namely the counter-plate 5, 5' or 6, 6° and the radial wing 30 or 40 of the reinforcement piece 3, 3', 4, 4' and the overall mechanical strength of the crankcase 1 with respect to compression and temperature rise is greatly improved. The different types of reinforcement pieces 3, 4, 3°, 4' and the different types of counter plate 5, 6, 5°, 6° which have just been described can be combined in different ways. Thus, it is possible to have reinforcing pieces and / or counter-plates (whether in annular form or in the form of annular segments) arranged against one and / or the other of the flanges 22, 23 of the body 2. When on either side of a flange of the body 2 there are reinforcing pieces in the form of annular segments 3' and counter-plates in the form of annular segments 5', and these segments are respectively arranged circumferentially end to end, then advantageously the segments 3' are arranged so that their contact lines at their respective ends are circumferentially offset relative to the contact lines of the respective ends of the segments 5°. Advantageously, the same is done for the annular segments 4' and 6'. This reinforces the mechanical strength of the flange of the body 2. When the annular segments are arranged circumferentially but do not touch each other (because they are not arranged end to end), it is also advantageous to arrange the segments 3 and 5' so that the ends of a segment 3' are circumferentially offset relative to the ends of a segment 5' located on the other side of the flange of the body 2, (the same applies to the segments 4' and 6°). Housing manufacturing process. The reinforcement piece(s) and the metal counterplate(s) are manufactured, for example, by casting or forging. For example, a titanium bar is rolled, possibly bent, and then machined. The assembly of the at least one reinforcing piece 3, 3', 4, 4', of the body 2 and possibly of the at least one counterplate 5, 5', 6, 6' can be done in different ways. Assembly by cold gluing. In this case, the body 2 made of composite material is manufactured beforehand. To do this, a 3D woven preform is used, for example made of carbon strands. This preform is then wrapped several times around a part of the mold. Then this mold, whose shape is adapted to that of body 2, is closed and the resin is injected, in order to obtain body 2 with its barrel and flanges. Furthermore, preferably, and as can be seen in [Fig.5], the barrel 21 of the body 2 has at least one of its ends and preferably at both of its ends 211 and 212, a thickness E1 less than that of the rest of the barrel 21, so as to define an annular recess referenced 2110 for the upstream end 211 and respectively 2120 for the downstream end 212. In the preferred embodiment of the invention shown in [Fig. 5], these upstream 2110 and downstream 2120 recesses are formed on the internal face 213 of the barrel 21. The dimensions of these recesses 2110, 2120 (width and thickness) are such that these recesses 2110, 2120 can receive the axial branch 31, respectively 41 of the corresponding reinforcing piece 3, 3', 4, 4' and that this axial branch is flush with the face of the barrel 21 in which this recess is formed. Preferably, and to the extent that the body 2 is manufactured by winding a preform, the thickness of the recess 2110, 2120 (and therefore the thickness of the axial branch 31, 41) corresponds to a multiple of the thickness of the preform. In other words, in the embodiment of [Fig. 5], the upstream recess 2110 is dimensioned so as to receive the axial branch 31 of the upstream reinforcing piece 3 and the downstream recess 2120 is dimensioned so as to receive the axial branch 41 of the reinforcing piece 4 and that in each case, the axial branches 31, 41 are flush with the same level as the internal face 213 of the barrel 21. The fixing of the reinforcing part(s) and possibly the counter plate(s) can then be carried out by positioning these parts on the body 2, at the appropriate locations described previously, then by cold gluing, for example using an epoxy type glue or a thermosetting adhesive film. With this type of fixing, if the barrel 21 is cylindrical, then a counter plate is used in the form of annular segments which can be attached to the inner face of the flanges 22 or 23. If the barrel 21 is frustoconical, it is possible to use an annular counter plate 5, 6, by introducing it around the smaller diameter end of the barrel 21 and applying it against the flange located at the larger diameter end of the barrel 21. Assembly by co-injection. In this case, the reinforcing part(s) 3, 3', 4, 4' and possibly the counter plate(s) 5, 5', 6, 6° if present, are placed in the mold for manufacturing the body 2. The preform is placed there (rolled) as explained previously for assembly by cold bonding, then the mold is closed and the resin is injected into the mold, so that the aforementioned parts are held with the body 2. Assembly by mechanical fixing. Preferably, this fixing of the reinforcing piece(s) 3, 3°, 4, 4' and possibly the counter plate(s) 5, 5', 6, 6° if they are present, is carried out using rivets. Preferably, countersunk head rivets are used to maintain smooth surfaces. Axial rivets can be fixed through axial orifices provided respectively through the upstream 22 and downstream 23 flanges and the radial branches 30, 40 of the reinforcing pieces 3, 3°, 4, 4' and through axial orifices provided in the counterplates 5, 5', 6, 6°. Radial rivets may also be fixed through radial holes provided through the axial branches 31, 41 and the ends 211 and 212 of the barrel 21. Such rivets are not shown in the figures. In Figures 6 and 7, the axial orifices 300, 400 and radial orifices 310, 410 can be seen formed through the radial branch 30, 40 and the axial branch 31, 41 of the upstream 3° or downstream 4° reinforcement piece. In [Fig.5], the axial orifices 50 provided through the counterplate 5 can be seen. Finally, it should be noted that assembly by mechanical fixing can be the only assembly method or be carried out in addition to assembly by cold bonding or co-injection.

Claims

Claims

1. Annular casing (1) of a turbomachine, in particular an annular casing of a turbomachine fan, comprising a body (2) made of organic matrix composite material, this body (2) comprising a barrel (21) cylindrical or truncated cone, with longitudinal axis XX®, provided at its upstream (211) and downstream (212) ends, respectively of a radial flange upstream annular (22) and a downstream annular radial flange (23), characterized in that it comprises at least one reinforcing piece (3, 4, 3', 4'), made of metal, particularly titanium, this reinforcement part being an annular part (3, 4) or in the form of an annular segment (3°, 4), in that said reinforcing piece (3, 4, 3', 4') has on at least one part of its circumference, an L-shaped cross-section, so as to have a radial branch (30, 40) and an axial branch (31, 41), and in that said reinforcing piece (3, 4, 3', 4') is fixed to the body (2), so that its radial branch (30, 40) is in contact with the ex- face inner (221, 231) of one of the two upstream (22) and downstream radial flanges (23) and that its axial branch (31, 41) is in contact with the end (211, 212) of the barrel (21) from which the radial flange (30, 40) extends against to which said at least one reinforcing piece (3, 4) is fixed.

2. Annular casing (1) according to claim 1, characterized in that the upstream annular radial flange (22) and the downstream annular radial flange (23) extend radially outwards and in that the axial branch (31, 41) of the reinforcing piece (3, 4) is fixed in contact with the face internal (213) of the barrel (21).

3. Annular casing (1) according to claim | or 2, characterized in that the reinforcing piece (3, 4) is annular and has a section L-shaped transverse shape around its entire circumference.

4. Annular casing (1) according to claim | or 2, characterized in that it includes several segment-shaped annular reinforcement pieces annular (3°, 4°), and in that these annular segments (3°, 4') are fixed on the body (2) circumferentially end to end.

5. Annular casing (1) according to claim | or 2, characterized in that it includes several segment-shaped annular reinforcement pieces annular (3°, 4°), and in that these annular segments (3°, 4') are fixed on the body (2) so as to be spaced from one another or from one another of others.

6. Annular casing (1) according to claim 1 or 2, characterized in that the reinforcement piece (3, 3', 4, 4') has at least two parts (7) to L-shaped cross-section, joined by a joining part (8).

7. Annular casing (1) according to claim 6, characterized in that said junction part (8) has the following shape: - an axial tab (81) which extends in the extension of the axial branches (31, 41) of the two parts (7) with L-shaped cross-section joined by said axial tab (81), this axial tab (81) having a width (L2) less than or equal to the width (L1) of the axial branches (31, 41) of the two parts (7) with cross section in L, joined by said axial tab (81), -a radial tab (82) which extends in the extension of the radial branches (30, 40) of the two parts (7) with cross section in L, joined by said radial tab (82), this radial tab (82) having a height (H2) less than or equal to the height (H1) of the radial branches (30, 40) of the two parts (7) with cross section in L, joined by said radial tab (82), - an L-shaped bracket (83) equipped with a radial branch (830) and a axial branch (831), the height (H3) of the radial branch (830) of the square (83) being less than the height (H1) of the radial branches (30, 40) of the two parts with L-shaped cross-section, joined by said bracket (83) and the width (L3) of the axial branch (831) of the bracket (83) being less than the width (L1) of the axial branches (31, 41) of the two parts (7) with L-shaped cross-section, joined by said bracket (83).

8. Annular casing (1) according to any one of claims 1 to 7, ca- characterized in that the width (L1) of the axial branch (31, 41) of the reinforcement piece (3, 4, 3', 4') is equal to or greater than the height (H1) of the radial branch (30, 40) of this same reinforcing piece (3, 4, 3°, 4°).

9. Annular casing (1) according to any one of claims 1 to 8, ca- characterized in that the height (H1) of the radial branch (30, 40) of the reinforcement piece (3, 4, 3', 4') is such that it covers the entire outer face (221, 231) of the upstream (22) or downstream (23) radial flange at contact with which it is located.

10. Annular casing (1) according to any one of claims 1 to 9, ca- characterized in that the barrel (21) of the body (2) presents at least one of its two upstream (211) and downstream (212) ends, a thickness (El) in- lower than that of the rest of the barrel (21), so as to define a recess annular (2110, 2120) and in that this annular recess (2110, 2120) is sized to receive the axial branch (31, 41) of the reinforcement piece (3, 4; 3°, 4') and that this axial branch (31, 41) outcrops at the level of the face of the barrel (21) in which this recess (2110, 2120) is formed.

11. Annular casing {1) according to any one of claims 1 to 10, characterized in that it comprises at least one metal counterplate, fixed against the inner face (222, 232) of one of the two flanges upstream (22) and downstream (23) radials of the body (2), this counter-plate being an annular counterplate {5, 6) or having the shape of a segment annular (5°, 6°), and this counter-plate (5, 6, 5°, 6') having a constant or variable height (H4) and a lower or variable height (H4) equal to the height (H5) of the inner face (222, 232) of the flange upstream radial (22) or downstream (23) of the body (2) against which this counter- plate (5, 6, 5', 6°) is fixed.

12. Annular casing {1) according to any one of claims 1 to 11, characterized in that said reinforcing piece (3, 4, 3', 4') and possibly actually said counter plate (5, 6, 5°, 6°) is fixed or are fixed on the body (2) by cold bonding, by co-injection and / or by assembly mechanical, particularly using rivets.

13. A method of manufacturing an annular casing (1) according to any one of claims 1 to 6, characterized in that it comprises: of the preceding claims, characterized in that it comprises steps: - manufacturing said at least one reinforcement piece (3, 4, 3', 4°), - of possible manufacture of said counter-plate (5, 6, 5', 6°) if the latter is present, - and assembly of the body (2), the reinforcement part (3, 4; 3,4') and possibly counter plate (5, 6, 5', 6') by cold gluing or by co-injection and / or mechanical assembly, in particular using rivets, so as to obtain said annular casing (1).