CRANKCASE FOR AN AIRCRAFT TURBOMACHINE

Abstract

Aircraft turbomachine housing, comprising an annular shell (9) extending about an axis A and having an internal annular surface (9'), the housing also comprising an annular abradable support cartridge (30, 40, 50, 60) which is fixed against said internal annular surface (9'), the abradable support cartridge (30, 40, 50, 60) having a reinforced coating (32, 42, 52, 62) comprising a fibrous texture reinforcement (32'', 42'', 52'', 62'') embedded in a resin matrix (32'), the fibrous texture reinforcement (32'', 42'', 52'', 62'') comprising an overlap of fibrous texture plies (36, 37, 38, 39; 46; 57; 66, 68), in which the overlap of plies (36, 37, 38, 39; 46; 57; 66, 68) includes at least one ply of Kevlar® (36; 68) or of fiberglass (46; 68). Figure for abbreviation: Figure 5

Description

Title of the invention: CASING FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to the production of a casing, in particular a fan casing, for an aircraft turbomachine. Technical background

[0002] Conventionally, a turbomachine comprises from upstream to downstream, that is to say in the direction of flow of the gas flows, a fan, one or more compressors, a combustion chamber, one or more turbines, and a nozzle for ejecting the combustion gases leaving the turbine(s).

[0003] [Fig.l] partially and schematically represents a fan 1 of an aircraft turbomachine.

[0004] The fan 1 comprises a bladed wheel 2 which is surrounded by a fan casing 3, also called a retention casing due to its retention function in the event of debris being ingested into the fan or blade being lost.

[0005] The fan casing 3 typically comprises an annular casing 9 with an axis of revolution A which extends around the fan blades 2 of the turbomachine. This casing comprises an annular fixing flange 3', 3” at each of its axial ends. These flanges 3', 3” are used to fix the casing 3 to annular walls of the nacelle of the turbomachine.

[0006] The fan casing 3 is connected, upstream, to an air inlet sleeve not shown, and, downstream, to an intermediate casing shroud 6.

[0007] The casing also comprises an upstream acoustic shroud 7 and a downstream acoustic panel 8. The fan casing 3 further comprises an annular layer 4 called an abradable support cartridge, arranged on an internal annular surface 9' of the casing 9, between the upstream shroud 7 and the downstream panel 8. The abradable support cartridge 4 carries an annular layer 4' of abradable material, the latter forming, together with the shroud 7 and the downstream panel 8, the profile of the aerodynamic vein 1a of the turbomachine 1.

[0008] The main function of the abradable support cartridge 4 is to support the layer of abradable material 4' and to fill the clearance J ([Fig.l]) provided between the body 9b of the casing 9 and the blades 2 to avoid their direct contact in the event of an event exceeding normal operation, such contact being able to lead to a catastrophic resonance phenomenon.

[0009] The functions of the abradable support cartridge 4 are of two types:

[0010] • mechanical, on the one hand:

[0011] - supporting the layer of abradable material 4',

[0012] - fill the aforementioned clearance J,

[0013] - resist the pressure field that can be exerted in the vein of the turbomachine 1 during its operation,

[0014] - resist the ingestion of ice,

[0015] - allow the evacuation of smoke in the event of a fire in the compartment of the basket;

[0016] • aerodynamic, on the other hand, in order to guarantee the profile of the vein.

[0017] [Fig. 2] shows an abradable support cartridge 4. This abradable support cartridge 4 comprises a core made of NIDA 15 (i.e., made of material with a honeycomb structure), a carbon fiber coating 14 and layers of intumescent material 20, or densification layers. The densification layers 20 are arranged at the upstream and downstream ends of the core made of NIDA 15. The carbon fiber coating 14 is structured so as to envelop the densification layers 20 and the core made of NIDA 15 on three sides 13a, 13b and 13c. A fourth side 13d, namely the outer radial surface of the core 15, is intended to be bonded to the inner surface 9' of the casing 9 and is free of the carbon fiber coating 14.

[0018] In detail, the carbon fiber coating 14 here comprises four thicknesses of carbon fiber plies 16, 17, 18 and 19. The first thickness of plies 16 is that which envelops the densification layers 20 and the NIDA core 15 on three sides 13a, 13b and 13c, strictly speaking. These folds 16 therefore form on the one hand the outer surface of the vein 1a of the inner side 13b of the abradable support cartridge 4, and on the other hand the coating on the upstream 13a and downstream 13c sides of the cartridge 4. The folds 17 of the second thickness, shorter than the folds 16 of the first thickness, here extend exclusively longitudinally, internally to the core 15 and to the layers 20. The third and fourth thicknesses of folds 18 and 19 are interposed between the folds 17 on the one hand, and the core 15 and the downstream layer 20 on the other hand.The plies 18 and 19 form a reinforcement zone 4b in the downstream part 4a, thus increasing the local thickness of the abradable support cartridge 4, therefore the mechanical inertia, i.e. the quadratic moment, and the stiffness of the cartridge 4. In detail, the plies 19 are of axial length less than the plies 18, and each form a respective local excess thickness 4b” and 4b' ([Fig.2]). It is noted that the downstream part 4a corresponds to a narrowing of the internal diameter of the cartridge 4. .

[0019] [Fig. 3] also partially shows a fan section of an aircraft turbomachine 1 according to the state of the art, showing the path that a block of ice B can follow between a front cone 10, in the center of the turbomachine 1 and aligned on the longitudinal axis A, and a downstream part 4a of the abradable support cartridge 4. The ge The generation of such an ice block B of ice can be carried out in icing conditions in the laboratory to reproduce the conditions of ice formation at the cruising altitude of the aircraft: the turbomachine 1 is driven to rotate at maximum speed in a cloud at low temperature and high humidity. Ice forms on the cone 10 by accretion. From a critical thickness of ice, a significant piece, such as the ice block B, detaches and is expelled at high speed in the vein 1a. The ice block B then passes the blades 2 of the rotor and strikes the downstream part 4a of the abradable support cartridge 4, for example at a point 1 ([Fig.3]). This results in a sometimes total loss of the layer of abradable material 4' and damage to the carbon fiber fabrics of the abradable support cartridge 4. [Fig.4] illustrates the downstream part 4a of the abradable support cartridge 4 after such a test to reproduce icing conditions.We then observe the appearance of craters 40 in the carbon fiber structure.

[0020] At present, the replacement of an abradable support cartridge 4 exhibiting such damage on engines already in service, i.e. mounted on an aircraft, is not possible.

[0021] If the abradable support cartridge 4 were to suffer damage during the manufacturing phase, replacing it would be possible but difficult and expensive since it is glued to the casing 9. It would therefore be necessary to detach it, taking care not to damage the casing 3. A new abradable support cartridge 4 could then be installed, which would require carrying out an autoclave cooking cycle. Such a replacement is therefore expensive, delicate and time-consuming, and is therefore not desirable.

[0022] The invention therefore aims to propose an aircraft turbomachine casing whose abradable support cartridge has an improved service life, particularly in the event of ice impacts. Summary of the invention

[0023] The invention thus relates to an aircraft turbomachine casing, comprising an annular envelope extending around a longitudinal axis and having an internal annular surface, the casing also comprising an annular abradable support cartridge which is fixed against said internal annular surface, the abradable support cartridge having a reinforced coating comprising a fibrous texture reinforcement embedded in a resin matrix, the fibrous texture reinforcement comprising a superposition of fibrous texture plies, in which the superposition of plies comprises at least one ply of Kevlar® or glass fibers.

[0024] Thus, according to the invention, the mechanical strength of the abradable support cartridge on impact is improved, in particular in the event of an impact from ice and rotor blades. By providing impact-resistant fabrics, the damage linked to such impacts is also limited or even eliminated.

[0025] The casing according to the invention may comprise one or more of the following characteristics, considered independently of one another or in combination with one another:

[0026] - the at least one ply of Kevlar® or glass fibers extends at least partially in a downstream part of the abradable support cartridge and / or over more than half of the axial length of the abradable support cartridge;

[0027] - the at least one ply of Kevlar® or glass fibers forms a coating ra- internally of the abradable support cartridge and / or is configured to form an outer wall of a vein of the turbomachine;

[0028] - the at least one ply of Kevlar® or glass fibers also forms a layer peripheral on the upstream side and the downstream side of the abradable support cartridge;

[0029] - the at least one ply of Kevlar® or glass fibers is made of woven Kevlar® fabric, and wherein a thickness of mixed Kevlar®-carbon fiber woven fabric is radially superimposed externally on said Kevlar® woven fabric;

[0030] - the at least one ply of Kevlar® or glass fibers is made of woven Kevlar® fabric pre-impregnated with resin,

[0031] - the at least one ply of Kevlar® or glass fibers is made of glass fibers, and in wherein a thickness of fiber plies is superimposed radially externally on said fiberglass ply;

[0032] - at least one ply of Kevlar® or glass fibers is sandwiched between two folds between two thicknesses of carbon fiber plies;

[0033] - the abradable support cartridge comprising a honeycomb structure core, one face of the core preferably being free of at least one ply of Kevlar® or glass fibers;

[0034] - the honeycomb structure core being impregnated with epoxy resin;

[0035] - the fibrous texture reinforcement being embedded in an epoxy resin matrix.

[0036] The invention also relates to an aircraft turbomachine comprising a casing according to one or more of the above characteristics. Brief description of the figures

[0037] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0038] [Fig-1] The [Fig. 1] already discussed partially shows a sectional view of a fan of an aircraft turbomachine according to the state of the art;

[0039] [Fig.2] [Fig.2] illustrates an abradable support cartridge;

[0040] [Fig.3] [Fig.3] also partially shows a fan section of a tur- Aircraft engine according to the state of the art, showing the path that a block of ice can follow between a front cone, in the center of the turbomachine, and a downstream part of an abradable support cartridge;

[0041] [Fig.4] [Fig.4] illustrates very schematically a downstream part of a abradable support cartridge of [Fig.3] having undergone tests in icing conditions;

[0042] [Fig.5] [Fig.5] illustrates a first embodiment of a support cartridge abradable according to the invention;

[0043] [Fig.6] [Fig.6] illustrates a second embodiment of a support cartridge abradable according to the invention;

[0044] [Fig.7] [Fig.7] illustrates a third embodiment of a support cartridge abradable according to the invention;

[0045] [Fig.8] [Fig.8] illustrates a fourth embodiment of a support cartridge abradable according to the invention. Detailed description of the invention

[0046] In the following description, the invention is applied to a fan casing such as the casing 3 partially illustrated in [Fig. 1]. The invention is however not limited to this type of casing and can be applied to a casing of another type of turbomachine.

[0047] The casing 3 to which the invention applies has a generally annular shape around the longitudinal axis A. An arrow F materializes a forward direction of the elements illustrated with regard to their orientation once installed in the turbomachine. A double arrow Ext-Int in figures 5 to 8 materializes a radial direction and the inward and outward directions of the turbomachine 1 when the abradable support cartridges 30, 40, 50 and 60 described below are oriented according to their arrangement on a casing 3 of a turbomachine 1 in service on an aircraft.

[0048] The casing 3 comprises an annular envelope 9 which itself extends around the axis A ([Fig.l]).

[0049] An annular abradable support cartridge, or in ring sectors, such as the abradable support cartridges 30, 40, 50 or 60 described below, is arranged on an internal surface 9' of the annular casing 9.

[0050] A first embodiment of an abradable support cartridge 30 is illustrated in [Fig. 5]. Second, third and fourth embodiments of abradable support cartridges 40, 50 and 60 respectively are illustrated in Figures 6, 7 and 8 and will be described later.

[0051] In the embodiment of [Fig. 5], the abradable support cartridge 30 comprises a core made of NIDA 31 (i.e. made of a honeycomb structure material), a reinforced coating 32, made of a composite material, and densification layers 33. The densification layers 33 are arranged at the upstream and downstream ends of the core in NIDA 31, radially. The reinforced coating 32 is structured so as to envelop the NIDA core 31 and the densification layers 33 on three sides 34a, 34b and 34c. A fourth side 34d, namely the outer radial surface of the core 31, is intended to be bonded to the inner surface 9' of the casing 9 and is free from the coating 32.

[0052] In detail, the coating 32 comprises a reinforcement in fibrous texture 32'', comprising a superposition of plies in fibrous texture, embedded in a resin matrix 32'. In the embodiment shown, the reinforcement 32” comprises four thicknesses of plies in fibrous texture 36, 37, 38 and 39. The resin 32' is, preferably but not limited to, an epoxy resin. An epoxy resin will preferably also impregnate the NIDA core to benefit from the best possible chemical compatibility. The first thickness of plies 36 is that which envelops the NIDA core 31 and the densification layers 33 on three sides 34a, 34b and 34c, strictly speaking. These plies 36 therefore form, by their longitudinally extending middle part 36b, the radially inner layer of the abradable support cartridge 30 on the radially inner side 34b thereof, that is to say the outer wall of the flow path 1a of the turbomachine 1.The plies 36 also form, by their radially and outwardly oriented folds 36a and 36c, the peripheral layer of the cartridge 30 on the upstream 34a and downstream 34c sides, that is to say they form the upstream face and the downstream face of the cartridge 30. The plies 37, 38 and 39 are sandwiched radially between the plies 36 and the NIDA core 31. Radially and from the inside to the outside of the cartridge 30, the plies 36 to 39 and the core 31 are superimposed in the following manner: the middle parts 36b of the plies 36 in Kevlar®, the plies 37, 38 and 39 in carbon fibers, and the NIDA core 31. The plies 37 of the second thickness, shorter than the plies 36 of the first thickness, extend here exclusively longitudinally, radially internally to the core in NIDA 31 and to the densification layers 33.The third and fourth thicknesses of plies 38 and 39, shorter than the plies 37 and extending along the NIDA core 31 over a length less than the axial length of the core 31, are interposed between the plies 37 on the one hand, and the core 31 and the downstream densification layer 33 on the other hand. The plies 38 and 39 form a reinforcement zone 30b in the downstream part 30a. Finally, the plies 39 are here of axial length less than the plies 38, and each form a respective local excess thickness 30b” and 30b' ([Fig.5]).

[0053] In the embodiment illustrated in [Fig. 5], the plies 36 are made of Kevlar® fabric. The plies 36 are here three in number but one, two, four, five or more plies can be provided. Kevlar® has the advantage of having improved impact resistance compared to carbon fibers. The carbon fiber fabrics 37 to 39 arranged inside (i.e. within the abradable support cartridge 30) are thus protected from impacts, which limits, or even eliminates, the risks of damage requiring a replacement of the abradable support cartridge 30 during the lifetime of the turbomachine 1. In addition, Kevlar® is a less dense material than carbon fiber. With the same number of plies, replacing carbon fiber plies with Kevlar® plies thus makes it possible to lighten the abradable support cartridge 30 compared to the prior art.

[0054] The plies 37 to 39 are made of carbon fibers. It is appropriate to keep a certain number of them in order to guarantee the modal strength of the casing 3 (its resistance to vibration stresses). Preferably, the plies 37 are three to five in number. Preferably, the plies 38 are three to six in number (six in the embodiment illustrated in [Fig.5], for example). Preferably, the plies 39 are three to five in number.

[0055] Second, third and fourth alternative embodiments to the first embodiment are described below, with respective reference to Figures 6, 7 and 8, without however these being limiting of the invention. In these, identical elements bear the same references and are not repeated in the description which follows.

[0056] Compared to the first embodiment, in a second embodiment of abradable support cartridge 40 illustrated in [Fig. 6], a reinforced coating 42 comprising a fibrous texture reinforcement 42'' which comprises glass fiber plies 46 is provided. The plies 46 here replace the Kevlar® plies 36 of the coating 32. The reinforced coating 42 further comprises plies 37, 38 and 39, here identical in composition and arrangement to those of the coating 32.

[0057] The plies 46 are here three in number but one, two, four, five or more plies can be provided. Glass fibers have the advantage of having improved impact resistance compared to carbon fibers. The carbon fiber fabrics 37, 38 and 39 arranged inside (i.e. within the abradable support cartridge 40) are thus protected from impacts, which limits, or even eliminates, the risks of damage requiring replacement of the abradable support cartridge 40.

[0058] The folds 38 and 39 here form a reinforcement zone 30b in the downstream part 30a. Finally, the folds 39 here have an axial length less than the folds 38, and each form a respective local excess thickness 30b” and 30b'.

[0059] As can be seen in [Fig.6] by way of example, the improvement in the impact resistance of the abradable support layer 40 makes it possible, if necessary, to eliminate carbon fiber plies, such as the plies 39. In such a case, the NIDA core 31 can be thickened to replace the carbon fiber plies 39 eliminated.

[0060] Compared to the first embodiment, in a third embodiment of abradable support cartridge 50 illustrated in [Fig.7], a reinforced coating 52 comprising a fibrous texture reinforcement 52'' which comprises folds 57 of fabric Kevlar®-carbon hybrid is provided. The plies 57 here replace the carbon fiber plies 37 of the covering 32. The reinforced covering 52 also comprises plies 36, 38 and 39, here identical in composition and arrangement to those of the covering 32.

[0061] Preferably, but not limited to, the proportion between Kevlar®-carbon in the plies 57 is chosen to be balanced. An appropriate ratio can then be chosen from a volume ratio, a mass ratio, or even a ratio in number of fibers. For example, the plies 57 have a ratio in number of Kevlar® fibers relative to the number of carbon fibers of between 40 / 60 and 60 / 40 (i.e. the proportion of Kevlar® fibers relative to the total number of fibers is between 40 and 60% and respectively, the proportion of carbon fibers is 60 to 40%). More preferably, this ratio is between 45 / 55 and 55 / 45. Very preferably, this ratio is 50 / 50. By analogy, the ratio chosen can relate to the volume relationship between Kevlar® and carbon, or to the mass relationship between Kevlar® and carbon, based on the same numerical ratios.

[0062] This embodiment with hybrid plies 57 allows a more flexible, i.e. more gradual, transition between the properties of the plies 36 in Kevlar® and the plies 38 and 39 in carbon fibers. This embodiment also offers a reinforced downstream part 50a ([Fig.7]). Excellent mechanical and chemical consistency is thus obtained. In an advantageous example of plies 57, non-limiting and not illustrated in detail, the warp threads are made of carbon while the weft threads are made of Kevlar®. Such an example of configuration of the plies 57 allows simple weaving while allowing a gradual transition between the plies 36 and 38, i.e. by limiting the mechanical problems at the interfaces between the successive plies of different types.

[0063] The plies 36 of Kevlar® are here three in number but one, two, four, five or more plies may be provided. The plies 57 of Kevlar®-carbon hybrid fabric are here three in number but one, two, four, five or more plies may be provided.

[0064] Compared to the first embodiment, in a fourth embodiment of abradable support cartridge 60 illustrated in [Fig. 8], a reinforced coating 62 comprising a fiber texture reinforcement 62” which comprises on the one hand a thickness of plies 68 of glass fibers or Kevlar® and on the other hand plies of carbon fibers 66, is provided. The plies 68 replace the plies of carbon fibers 38 of the coating 32. The plies 66 replace the plies of Kevlar® 36. The thickness of plies 68 of glass fibers or Kevlar® is therefore sandwiched between two thicknesses of plies 37 and 39 of carbon fibers. Radially and from the inside to the outside of the cartridge 60, the plies 36 to 39 and the core 31 are superimposed in the following manner, in the downstream part 60a of the cartridge 60: the middle parts 36b of the 36 and 37 plies of carbon fiber, 68 plies of glass fiber or Kevlar®, 39 plies of carbon fiber, and the core of NIDA31.

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] The 68 plies of glass fiber or Kevlar® are here six in number but one, two, three, four, five or more plies can be provided. This alternative also makes it possible to improve the impact resistance of the abradable support cartridge 60, in particular in a reinforcement zone 60b in the downstream part 60a of the abradable support cartridge 60, compared to the prior art. The reinforcement zone then comprises an excess thickness 30b' (as mentioned above) and an excess thickness 60b” formed of the folds 68 In the first to third embodiments, the reinforced coatings are arranged on the surface, thus optimally protecting the carbon fiber plies 38, 39, and where appropriate the plies 37. The invention provides advantages on several levels. From a technical point of view: - the Kevlar® used as reinforcement has improved impact resistance (impacts from ice and / or rotor blades) and allows for a weight saving due to a lower density than carbon fibers; - the glass fibers used as reinforcement have improved impact resistance (impacts from ice and / or rotor blades). From an industrial point of view: - thanks to higher impact resistance, the abradable support cartridges according to the invention can enjoy an extended service life. There is therefore no longer any need to replace the abradable support cartridge in a turbomachine casing, such as a fan casing, in the event of an ice impact; - the improvement in impact resistance allows, where appropriate, the removal of carbon fiber plies (for example, by thickening the NIDA material to replace the removed carbon fiber plies). In such a case, the invention makes it possible to save on material costs and shorten the cycle time during manufacturing. The invention therefore brings significant gains both on the technical and industrial levels.

Claims

Claims

1. Aircraft turbomachine casing, comprising an annular casing (9) extending around an axis A and having an internal annular surface (9'), the casing also comprising an annular abradable support cartridge (30, 40, 50, 60) which is fixed against said internal annular surface (9'), the abradable support cartridge (30, 40, 50, 60) having a reinforced coating (32, 42, 52, 62) comprising a fibrous texture reinforcement (32”, 42”, 52”, 62”) embedded in a resin matrix (32'), the fibrous texture reinforcement (32”, 42”, 52”, 62”) comprising a superposition of fibrous texture plies (36, 37, 38, 39; 46; 57; 66, 68), characterized in that the superposition of fibrous texture plies fibrous (36, 37, 38, 39; 46; 57; 66, 68) comprises at least one ply of Kevlar® (36; 68) or glass fibers (46; 68), and in that plies (38, 39;68) of said superposition of folds in fibrous texture each form a local excess thickness defining a reinforcement zone (30b; 60b) in the downstream part (30a; 50a; 60a) of the abradable support cartridge (30, 40, 50, 60).;

2. Aircraft turbomachine casing according to the preceding claim, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply extends at least partially in a downstream part (30a, 50a, 60a) of the abradable support cartridge (30, 40, 50, 60) and / or over more than half of the axial length of the abradable support cartridge (30, 40, 50, 60).

3. Aircraft turbomachine casing according to one of the preceding claims, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply forms a radially inner coating of the abradable support cartridge (30, 40, 50, 60) and / or is configured to form an outer wall of a vein (la) of the turbomachine (1).

4. Aircraft turbomachine casing according to one of the preceding claims, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply also forms a peripheral layer on the upstream side (34a) and / or the downstream side (34c) of the abradable support cartridge (30, 40, 50, 60).

5. Aircraft turbomachine casing according to one of the preceding claims, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply is made of Kevlar® fabric (36), and in which a thickness of mixed Kevlar®-carbon fiber woven fabric (57) is superimposed radially externally on said Kevlar® fabric (36).

6. Aircraft turbomachine casing according to one of the preceding claims, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply is made of pre-impregnated Kevlar® fabric (36).

7. Aircraft turbomachine casing according to one of claims 1 to 4, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply is made of glass fiber (46), and in which a thickness of carbon fiber plies (37, 38, 39) is superimposed radially externally on said glass fiber ply (46).

8. Aircraft turbomachine casing according to claim 1 or 2, in which the Kevlar® (36; 68) or glass fiber (46; 68) ply is sandwiched between two plies between two thicknesses of carbon fiber plies (37, 39).

9. Aircraft turbomachine casing according to one of the preceding claims, in which the abradable support cartridge (30, 40, 50, 60) comprises a honeycomb structure core (31), one face (34d) of the honeycomb structure core (31) preferably being free of the at least one ply of Kevlar® (36; 68) or glass fibers (46; 68).

10. Aircraft turbomachine comprising a casing according to one of the preceding claims.

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