CASING FOR AN AIRCRAFT TURBOMACHINE

Abstract

The invention relates to a casing (200) for fairing a fan blade for an aircraft turbomachine, this casing having an annular shape around a longitudinal axis (A) and comprising at its axial ends annular fastening flanges (2041, 2042), respectively upstream (2041) and downstream (2042), the casing being made of composite material and comprising a preform produced by weaving warp (FC) and weft (FT) threads, and a polymer matrix in which this preform is embedded, characterized in that, between an intermediate section (202a) and at least one of the flanges, the casing (200) comprises another section (202b) of which at least some of the warp threads are produced from fibers in a first material of a first stiffness, and the rest of the warp threads are produced from fibers in a second material of a second stiffness greater than that of the first material. Figure for abstract: Figure 3

Description

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

[0001] The present invention relates to a fan blade fairing casing for an aircraft turbomachine and a turbomachine comprising this casing. Technological background

[0002] Generally speaking, a turbomachine 100, in particular an aircraft turbomachine, as illustrated in [Fig.lA], comprises from upstream to downstream (i.e. in the direction of flow of the gas flows F), a fan 110, one or more compressors 102 b 1022, a combustion chamber 104, one or more turbines 106b 1062 and an ejection nozzle 108 for the combustion gases leaving the turbine(s).

[0003] [Fig. 1B] schematically and partially illustrates a fan 110 of a turbomachine. The fan 110 comprises a fan blade or a bladed wheel 112 which is surrounded by a fan or fairing casing 200, also called a retention casing due to its function of retaining the blades in the event of their rupture, or in the event of debris entering the fan.

[0004] With reference to [Fig. 1C], a fan casing 200, and more generally a casing 200, typically comprises an annular casing 202, which may be, for example and in a non-limiting manner, made of metallic material or of composite material from woven fibers embedded in a polymeric resin. Preferably, the annular casing is made of composite material.

[0005] In a context of reducing the ecological footprint of aircraft, the use of a lightweight but equally high-performance material, such as composite material, makes it possible to very significantly improve the environmental performance of aircraft by reducing in particular their mass and, at the same time, their fuel consumption.

[0006] Still with reference to [Fig.lC], the annular casing 202 has an axis of revolution A and extends around the fan blades 112 of the turbomachine. The casing 200 comprises an annular fixing flange 204b 2042 at each of the axial ends of the annular casing 202. These flanges 204b 6042 are used to fix the casing 200 to annular walls of a nacelle which surrounds the turbomachine to form an aircraft propulsion assembly.

[0007] The casing 200 may, for example, be connected by the flanges 204b 2042 on the one hand to an air inlet sleeve 4a located upstream of the fan casing 200, and on the other hand, to an intermediate casing shroud located downstream of the fan casing 200. The casing blower 600 also includes upstream acoustic panels 210, as illustrated in [Fig.lD], and downstream acoustic panels (not shown).

[0008] With reference to [Fig.lD], an abradable annular cartridge may be positioned on an internal annular surface 300i([Fig.lC]) of the casing 202 of the housing 200, between the upstream acoustic panels 210 and the downstream acoustic panels. This abradable cartridge may comprise an annular layer 208 of abradable material and an annular panel or support 206 supporting the annular layer 208, the panel 206 being fixed to the casing 202. This abradable annular layer 208 is intended to wear in a controlled manner during operation. As for the panel 206, it may, for example, be solid or have a honeycomb structure. The casing 200 may further comprise at least one stiffener 302a fixed to the outer surface 3002 of the casing 202 as illustrated, for example, in [Fig.lE]. The stiffeners contribute to reinforcing or improving the rigidity of the casing 200.

[0009] In addition to the retention function, the casing 200 is further designed to: - ensure mechanical continuity (of forces and moments) between the air inlet sleeve and the intermediate casing shell; - allow the fixing of the abradable annular cartridge panels, the upstream acoustic panels and the downstream acoustic panels, thus ensuring continuity of the aerodynamic vein; - allow the attachment of equipment and supports known per se, in particular inside the nacelle; - meet regulatory specifications for fire and leaks; - allow continuity of electric current for lightning resistance, etc.

[0010] The casing 202 of the housing 200 and the annular cartridge are separate parts which are manufactured separately and then assembled in an assembly step in which the panel 206 is first fixed to the annular casing 202 and then the abradable annular layer 208 is bonded to the panel 206.

[0011] It has already been proposed to manufacture the fan casing from a material composite made from woven fibers embedded in a polymer resin, the manufacturing process being of the “RTM” type (English acronym for “Resin Transfer Molding”).

[0012] In an RTM manufacturing process, a mold comprising two half-shells, placed one on top of the other, confines a molding cavity. The fibers can be, for example, woven in three dimensions (3D), via a Jacquard type loom for example, and comprise layers of warp threads Fc and weft threads FT as illustrated for example in [Fig.2A]. The fibers form a fiber preform which is inserted into the mold cavity between the two half-shells, before injection of the resin.

[0013] [Fig.1E] illustrates the direction Dc of the warp threads (circumferential direction) and the direction DT of the weft threads (axial direction) on the casing 202 of a manufactured casing.

[0014] In the example illustrated in [Fig.2A], the layer or ply C; (i=1, 4) corresponds to a layer of woven strip forming the preform. The latter comprises eight layers of fibrous texture.

[0015] The envelope 202 of the casing 200 may comprise a winding over several turns of the preform. In the example of [Fig.2A], the envelope 202 comprises a winding over four turns of layers or plies C, 4 of woven strip forming the preform. Each ply C, 4 represents one turn.

[0016] The use of the RTM manufacturing process is particularly advantageous because it makes it possible to produce parts having a lower overall mass than these same parts when they are made of metallic material, while having at least equivalent, if not superior, mechanical resistance.

[0017] The retention capacity of the composite casing is ensured by the quantity of fibers, the weaving pattern and the quality of the weaving. It may thus be desired to improve this retention capacity of turbomachine casings to guarantee the retention of blades in the event of their rupture, or in the event of debris entering the fan.

[0018] When a blade breaks, it fragments upon contact with the casing 200 and in particular the envelope 202, as illustrated in [Fig.2B], at points CHi and CH2. The envelope 202 can then be subjected to three types of stress: - the perforating impact, very localized, generally at the axial CHi position of the blade. It causes a perforation on the internal face 300i and high local deformations on the external face 3002; - the non-perforating impact, relatively localized, can occur downstream CH2 (and / or upstream) of the axial position of the blade. It causes high local deformations on the internal and external faces; and - the extended displacement / deformation wave, which begins at the main impacts CHi, CH2, then moves from one point to another in the casing.

[0019] To resist perforating impact, one solution is a localized thickening in the impact zone. As for non-perforating impact, one solution is a better elongation at break in the impact zone.

[0020] When the casing is subjected to a deformation wave Vgb Vg2, the latter which initiates at the level of the impacts, for example CH2, and propagates upstream Vgi and downstream Vg2 of the casing, as illustrated in [Fig.2C]. This wave can create cracks at different locations (for example at the level of the flanges) and strongly stress the adjacent parts held to the flanges and the equipment attached to the casing.

[0021] It may thus be desirable to provide a casing which makes it possible to dispense with at least some of the above-mentioned problems and constraints. Summary of the invention

[0022] There is therefore proposed a fairing casing for a fan blade for an aircraft turbomachine, this casing having an annular shape around a longitudinal axis and comprising at its axial ends annular fixing flanges, respectively upstream and downstream, the casing comprising an intermediate section located at a distance from the flanges and configured to extend around a fan blade, the casing being made of composite material and comprising a preform produced by weaving, preferably three-dimensional, of warp and weft threads and a polymer matrix in which this preform is embedded, the warp and weft threads located in said section being made from fibers in the same material, characterized in that, between the section and at least one of the flanges, the casing comprises another section of which at least some of the warp threads are made from fibers in a first material of a first stiffness,and the remaining warp threads are made from fibers in a second material of a second stiffness greater than that of the first material.

[0023] By stiffness of a fiber is meant the capacity to resist elastic deformation, the stiffness of the fiber being characterized or defined by a modulus of elasticity or Young's modulus. Yarns made from fibers with greater stiffness therefore have increased stiffness.

[0024] The insertion of warp threads of increased stiffness into the preform, from which the casing envelope is manufactured, makes it possible to introduce a discontinuity of stiffness into the envelope, particularly in the vicinity of the upstream and / or downstream flanges. Since the deformation wave does not propagate in the same way from one material to another, it is then possible to reduce or control the effects of this deformation wave as a function of the stiffness of the fibers from which the warp threads are made.

[0025] Thus, thanks to the invention it is possible to stop / slow down the deformation wave or to reduce its effects and preserve the integrity of the casing and the adjacent parts connected to the casing flanges.

[0026] The invention also allows a gain in mass and a reduction in the ecological footprint relating to the manufacture of casings. Indeed, by stopping or reducing the deformation wave, the insertion of warp threads of greater stiffness (compared to the rest of the warp threads of the preform) prevents degradation of the casing. In other words, the threads with increased stiffness make it possible to achieve better mechanical strength of the casing. This better strength makes it possible to reduce the thicknesses of the casing or to eliminate elements such as stiffeners, and therefore to obtain a gain in mass. In addition, better casing performance reduces the number of maintenance interventions and the manufacture of new replacement parts.

[0027] The invention may further comprise one or more of the following optional features, in any technically possible combination: - the stiffness of a fiber is defined by its modulus of elasticity or Young's modulus; - the fibers of the second material of second stiffness are interlaced fibers; - said or each other section has an axial length or dimension which represents between 2% and 20% of an internal diameter of the casing; - the warp threads made from the second material of second stiffness are parallel to the warp threads of the first material of first stiffness and oriented along an axis which is substantially tangent to a circumference centered on said longitudinal axis (A) of the casing (200), the weft threads (FT) being oriented in a direction parallel to the longitudinal axis; - the warp threads (Fc) made in the second material of second stiffness represent between 50% and 100% of the total quantity of warp threads of the preform, said total quantity being defined as the sum of the warp threads (Fc) made in the first material of first stiffness and the warp threads (Fc) made in the second material of second stiffness; - the casing comprises at least a first transition zone attached to an upstream axial end of said other section and a second transition zone attached to the downstream axial end of said other section opposite the upstream end, the first and second zones comprising a quantity of warp threads made from the second material of second stiffness lower than that of said other section; - the second material of second stiffness is carbon fiber of type Tl 100 or UMS 45 and the first material of first stiffness is carbon fiber of type IM7.

[0028] The invention also relates to an aircraft turbomachine, comprising at least one casing as described above. Brief description of the figures

[0029] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: - [Fig.1A] is a schematic representation of a simplified view of a turbomachine according to the prior art, - [Fig.lB] is a schematic representation of an axial and partial sectional view of a fan of an aircraft turbomachine, according to the prior art, - [Fig.lC] is a schematic representation of a perspective view of a fan casing, according to the prior art; - [Fig.lD] is a schematic representation of a partial axial sectional view of a fan casing, according to the prior art; - [Fig.1E] is a schematic representation of a partial axial sectional view of the casing of a housing, according to the prior art; - [Fig.2A] is a schematic representation of a partial axial sectional view of the casing of a housing comprising a winding over four turns of a preform, according to the prior art; - [Fig.2B] is a schematic representation of a partial axial sectional view of the casing of a housing subjected to impacts; - [Fig.2C] is a schematic representation of a partial axial sectional view of the casing of a housing subjected to waves of deformation; - [Fig. 3] is a schematic representation of a partial axial sectional view of the casing of a housing, according to the invention; - [Fig.4] is a schematic representation of a partial axial sectional view of the casing of a housing comprising a winding over four turns of a preform in which warp threads with increased stiffness are inserted over all of the turns, according to the invention; - [Fig.5] is a schematic representation of a partial axial sectional view of the casing of a housing showing the axial extent of insertion of wires with increased stiffness, according to the invention; - [Fig.6] is a schematic representation of a partial axial sectional view of the casing of a housing comprising zones having different concentrations of wires with increased stiffness, according to a variant of the invention; and - [Fig.7] is a schematic representation of a partial axial sectional view of the casing of a housing with the substitution of a stiffener by a section comprising wires with increased stiffness, according to another variant. Detailed description of the invention

[0030] By convention, in the description, the term “axial” qualifies the orientation of structural elements extending in the direction of an axis. This axis corresponds substantially to an axis of rotation or revolution. The term “radial” qualifies an orientation of structural elements extending in a direction perpendicular to the axis of rotation or revolution. The terms “internal” and “external” are used with reference to a positioning relative to the axis of rotation or revolution. Thus, a structural element extending along the axis of rotation or revolution comprises an internal face facing the longitudinal axis and an external surface, opposite its internal surface.

[0031] In the following description, the invention is applied to a casing 200 for fairing a fan blade or a vane, for example a fan 110, for an aircraft turbomachine 100. The invention is however not limited to this type of casing 200 and can be applied to other casings of a turbomachine 100.

[0032] The casing 200 according to the invention has a generally annular shape around an axis A.

[0033] Structural elements similar to those of the prior art according to Figures 1A-2C have the same numerical references.

[0034] [Fig. 3] illustrates a portion of the casing 200, according to the invention.

[0035] The casing 200 comprises an annular casing 202 having at its axial ends upstream 204i and downstream 2042 annular fixing flanges. The annular casing 202 of the casing 200 comprises an intermediate section 202a located at a distance from the flanges and configured to extend around a fan blade or blading.

[0036] Preferably, the casing 200 is made of composite material (organic matrix composite or OMC) and comprises a preform produced by weaving, preferably three-dimensional (3D), of warp and weft threads and a polymer matrix (polymer resin) in which this preform is embedded.

[0037] The casing may be made or manufactured by winding around said axis A over several superimposed turns a layer of woven strip forming the preform as shown in [Fig.2A].

[0038] The warp and weft threads located in said section are made from fibers in the same material. For example and in a non-limiting manner, carbon fibers of type IM7.

[0039] The casing 200 may further comprise at least one stiffening element 302ac fixed or integrated into the casing 202 and projecting from the external surface of the casing 202 of the casing 200.

[0040] The casing 200 further comprises, between the section 202a and at least one of the flanges 204i, 2042, the casing 200 comprises another section 202b of which at least some of the warp threads are made from fibers in a first material of a first stiffness, and the remainder of the warp threads Fc are made from fibers in a second material of a second stiffness greater than that of the first material.

[0041] The warp threads Fc made from the second material of second stiffness are parallel to the warp threads Fc of the first material of first stiffness and oriented along an axis which is substantially tangent to a circumference (direction Dc on see [Fig.lE]) centered on the longitudinal axis of the casing 200. The weft threads FT are oriented in a direction parallel to the longitudinal axis A (direction DT on [Fig.lE])•

[0042] An advantage of the 3D woven composite structure forming the preform is that it allows the weaving of fibers having different characteristics within the part in order to to improve the physical characteristics (elongation at break, linear mass, etc.) of the preform. For example, and without limitation, a Tl 100 type carbon fiber has a higher stiffness than an IM7 type carbon fiber. However, the characteristics of the Tl 100 fiber are not necessarily all better (elongation at break, linear mass, etc.). It is therefore not necessarily wise to use a Tl 100 type carbon fiber on the entire casing.

[0043] Thus, in the present invention, the preform is made with materials of different physical characteristics. The warp threads of the intermediate section 202a are made with fibers in a first material and the warp threads of the other section 202b comprise at least threads made with fibers in a second material in order to improve the physical characteristics (resistance to deformation, elongation at break, etc.) of the casing 200.

[0044] Since the deformation wave does not propagate in the same way from one material to another, this difference in stiffness between the wires of the first material and that of the wires of the second material will have the effect of slowing down or stopping the deformation wave.

[0045] The fibers of the first material, of low stiffness compared to that of the second material, are for example carbon fibers of type IM7.

[0046] The fibers of the second material, of greater stiffness compared to that of the first material, are interlaced fibers (or stiff strands). These fibers are, for example, and in a non-limiting manner, carbon fibers of type Tl 100 or UMS 45, preferably of type Tl 100.

[0047] The IM7 type fiber (first material) has a stiffness characterized by a Young's modulus of approximately 250 GPa. As for the Tl 100 type carbon fiber (second material), its stiffness is characterized by a Young's modulus of approximately 300 GPa, and that of the UMS45 type carbon fiber (second material) by a Young's modulus of approximately 430 GPa.

[0048] [Fig. 4] illustrates an axial section of the casing 202 of the casing 200 obtained by winding a preform. An external diameter Dext and an internal diameter Dint of the casing define the width of the casing 202.

[0049] A casing made of 3D woven material may consist of a winding of several plies C14 (as also illustrated in [Fig.2A]), each ply corresponding to one turn of the preform around the axis A.

[0050] As the preform comprises warp threads made using fibers with increased stiffness, i.e. made from the second material with a second stiffness greater than the first stiffness of the first material, the envelope 200 of the casing 200 therefore comprises warp threads with increased stiffness over all the turns (for example over four turns in the case of a preform wound over four turns).

[0051] Preferably, the warp threads Fc made from the second material of second stiffness represent between 50% and 100% of the total quantity of warp yarns of the preform. The total quantity of warp yarns of the preform is defined as the sum of the warp yarns Fc made in the first material of first stiffness and the warp yarns Fc made in the second material of second stiffness.

[0052] With reference to [Fig. 5], the warp threads made of the second material of second stiffness are arranged in a section 202b having an axial length or dimension La which represents between 2% and 20% of an internal diameter of the casing. Preferably, the axial length La is approximately 10% of the internal diameter. For example, and in a non-limiting manner, the internal diameter may be the diameter of a blade of the fan blade at the axial position of the leading edge of the blade or the diameter of the aerodynamic vein.

[0053] In another variant shown in [Fig.6], the casing 202 of the housing further comprises at least a first transition zone 202ci axially attached to the upstream end of the section 202b comprising wires made from the second material of second stiffness, and a second transition zone 202c2 axially attached to the downstream end of the section comprising wires to made from the second material of second stiffness.

[0054] In this variant, the first and second zones 202ci, 202c2 comprise a quantity of warp threads made from the second material of second stiffness lower than that of the section 202b.

[0055] In this configuration, the envelope 202 of the casing 200 comprises several stiffness discontinuities which can improve the capacity of the casing to resist deformation waves.

[0056] In another variant, illustrated in [Fig.7] ((1) and (2)), the presence of a section comprising warp threads with increased stiffness makes it possible to replace a stiffener present to enhance the natural modes of the casing.

[0057] In the example of [Fig.7], it is the stiffener 302c (see the first envelope illustrated in (1)) which is replaced by a section 202b (figure see the second envelope illustrated in (2)) comprising wires made from the second material of second stiffness, i.e., wires with increased stiffness.

[0058] In this configuration, the presence of the section 202b comprising wires with increased stiffness (made from the second material of second stiffness) also makes it possible to improve the capacity of the casing to resist the vibration problems to which the casing 200 may be subjected.

[0059] Thus, advantageously, those skilled in the art will understand that the creation of a discontinuity in stiffness makes it possible to stop or slow down the wave of deformation. This has the consequence of reducing, for example, and in a non-limiting manner, the displacements / deformations at the flanges and transmitted to the adjacent parts and therefore avoiding a deterioration of the structure of the casing and the turbomachine. The mechanical strength of the casing is therefore improved or reinforced.

[0060] The invention also allows a weight saving and a reduction in the ecological footprint relating to manufacturing. Indeed, by stopping or reducing the deformation wave, the insertion of increased stiffness fibers into the preform prevents degradation of the casing. In other words, the increased stiffness fibers allow for better mechanical strength of the casing. This better strength makes it possible to reduce the thickness of the casing or to eliminate elements such as stiffeners, and therefore to obtain a weight saving.

[0061] Better casing performance also reduces the number of maintenance interventions and the manufacture of new replacement parts.

Claims

Claims

1. Casing (200) for fairing a fan blade for an aircraft turbomachine, this casing having an annular shape around a longitudinal axis (A) and comprising at its axial ends annular flanges (204b 2042) for fixing, respectively upstream (204i) and downstream (2042), the casing (200) comprising an intermediate section (202a) located at a distance from the flanges and configured to extend around a fan blade, the casing (200) being made of composite material and comprising a preform produced by weaving warp (Fc) and weft (FT) threads, and a polymer matrix in which this preform is embedded, the warp (Fc) and weft (FT) threads located in said section (202a) being made from fibers in the same material, characterized in that, between the section (202a) and at least one of the flanges (204b 2042),the casing (200) comprises another section (202b) of which at least some of the warp threads (Fc) are made from fibers in a first material of a first stiffness, and the rest of the warp threads (Fc) are made from fibers in a second material of a second stiffness greater than that of the first material.,

2. A housing according to claim 1, wherein the stiffness of a fiber (Fc, FT ) is defined by its modulus of elasticity or Young's modulus.

3. A casing according to claim 1 or 2, wherein the fibers (Fc) of the second material of second stiffness are interlaced fibers.

4. A casing (200) according to one of claims 1 to 3, wherein said or each other section (202b) has an axial length or dimension (La) which represents between 2% and 20% of an internal diameter of the casing (200).

5. Casing (200) according to one of claims 1 to 4, in which the warp threads (Fc) made in the second material of second stiffness are parallel to the warp threads (Fc) of the first material of first stiffness and oriented along an axis which is substantially tangent to a circumference centered on said longitudinal axis (A) of the casing (200), the weft threads (FT) being oriented in a direction parallel to the longitudinal axis (A).

6. Casing according to one of claims 1 to 5, in which the warp threads (Fc) made from the second material of second stiffness represent between 50% and 100% of the total quantity of warp threads of the preform, said total quantity being defined as the sum of the warp threads (F c) made in the first material of first stiffness made and warp threads (Fc) made in the second material of second stiffness.

7. Casing (200) according to the preceding claim, in which it comprises at least a first transition zone (202ci) attached to an upstream axial end of said other section (202b) and a second transition zone (202c2) attached to the downstream axial end of said other section (202b) opposite the upstream end, the first and second zones (202cb 202 c2) comprising a quantity of warp threads made from the second material of second stiffness lower than that of said other section (202b).

8. Housing (200) according to one of claims 1 to 7, in which the second material of second stiffness is carbon fiber of type Tl 100 or UMS 45 and the first material of first stiffness is carbon fiber of type IM7.

9. Casing (200) according to one of claims 1 to 8, in which said other section (202b) preferably comprises warp threads (Fc) made from the fibers of the second material of second stiffness.

10. Aircraft turbomachine (100), comprising at least one casing (200) according to one of the preceding claims.

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