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 an axis (A) and comprising at its axial ends annular fastening flanges (2041, 2042), respectively upstream (2041) and downstream (2042), the casing comprising an intermediate section (202a) 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 winding around said axis on several superimposed turns of a layer of woven strip forming a preform, and a polymer matrix in which this winding is embedded, the casing further comprises an upstream annular stiffening insert (310a) integrated in said winding and axially interposed between the upstream flange and said intermediate section,and a downstream annular stiffening insert (310b) integrated into said winding and axially interposed between the downstream flange and said intermediate section. Figure for the 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 (radial or 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 Q (i=1, 4) corresponds to a layer of woven strip forming the preform. The latter comprises eight layers of fibrous texture.

[0015] Generally, the envelope 202 of the casing 200 comprises 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 preform. Each ply CM 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 an axis A and comprising at its axial ends annular fastening 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 winding around said axis on several superimposed turns of a layer of woven strip forming a preform, and a polymer matrix in which this winding is embedded, characterized in that it further comprises an upstream annular stiffening insert integrated in said winding and interposed axially between the upstream flange and said section, and a downstream annular stiffening insert integrated in said winding and interposed axially between the downstream flange and said section.

[0023] The positioning of an insert in the casing of the casing makes it possible to introduce a discontinuity of stiffness in the casing of the casing, in particular in the vicinity of the upstream and 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 insert.

[0024] 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.

[0025] The invention also allows a weight saving and a reduction in the ecological footprint relating to the manufacture of casings. Indeed, by stopping or reducing the deformation wave, the insert prevents damage to the casing. In other words, the insert allows 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. Furthermore, better strength of the casing makes it possible to reduce the number of maintenance interventions and the manufacture of new replacement parts.

[0026] The invention may further comprise one or more of the following optional features, in any technically possible combination: - each of the upstream and downstream inserts has a length or axial dimension which represents between 1% and 10% of an internal diameter of the casing; - each of the upstream and downstream inserts is wound with the layer of woven strip forming the preform over at least one turn around the axis; - each of the upstream and downstream inserts is arranged axially between two turns on perpendicular to the layer of woven tape forming the preform or inside the layer of woven tape forming the preform; - each of the upstream and downstream inserts is an elongated and continuous strip; - each of the upstream and downstream inserts is an elongated strip formed by a succession of independent pieces; - each of the upstream and downstream inserts is made of a metal alloy, for example a titanium or steel alloy; - each of the upstream and downstream inserts has an elliptical or trapezoidal or circular or rectangular shape in axial section.

[0027] The invention also relates to a turbomachine comprising a casing as described above. Brief description of the figures

[0028] 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 very schematic representation of the positioning of an insert between two layers of the casing of the casing of [Fig.3] according to a first variant; - [Fig.5A] is a schematic representation of a view of the insert in the winding of the casing envelope, according to a first variant; - [Fig.5B] is a schematic representation of a profile view of the insert in the winding of the casing of the housing, according to a second variant; - [Fig.6] is a schematic representation of the positioning of an insert inside the same layer of the casing of the housing of [Fig.3] according to a second variant; - [Fig.7] is a schematic representation of a partial axial sectional view of the casing of a housing showing the axial extent of the insert, according to the invention; and - [Fig.8] is a schematic representation of the positioning of the insert at a given angular position with respect to an accessory, according to one embodiment. Detailed description of the invention

[0029] 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.

[0030] 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.

[0031] The casing 200 according to the invention has a generally annular shape around an axis A.

[0032] Structural elements similar to those of the prior art according to Figures 1A-2C have the same numerical references.

[0033] [Fig. 3] illustrates a portion of the casing 200, according to the invention.

[0034] 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.

[0035] Preferably, the casing 200 is made of composite material and comprises a winding around said axis A on several superimposed turns of a layer of woven strip forming a preform, and a polymer matrix (polymer resin) in which this winding is embedded. The woven strip may be for example a three-dimensional weave. 3D fibers.

[0036] 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.

[0037] The casing 200 further comprises at least one upstream annular insert 310a and one downstream annular stiffening insert 310b integrated into said winding.

[0038] The upstream insert 310a is axially interposed between the upstream flange 204i and the section 202a of the casing 202 and the downstream insert 310b is axially interposed between the downstream flange 2042 and the section 202a of the casing 202.

[0039] According to a first variant illustrated in [Fig.4], each of the upstream 310a and downstream 310b inserts is arranged axially between two superimposed turns of the layer of woven strip forming the preform.

[0040] Still according to [Fig.4], illustrating a very schematic axial sectional view of the casing 202 of the housing 200, it can be observed that the casing is made up of a winding on four turns represented by four folds C1-4. The insert 310 is interposed between the second fold C2 and the third fold C3.

[0041] A casing made of 3D woven material is made up of a winding of several plies Cm. It is therefore possible to place the insert between two plies at a given axial position. Thus, each of the upstream 310a and downstream 310b inserts is wound with the layer of woven strip forming the preform over at least one turn around the axis.

[0042] Each of the upstream inserts 310a and downstream inserts 310b is an elongated strip.

[0043] In a variant, illustrated in [Fig.5A], the preform is wound on a Ci turn or fold. In this example, the insert is substantially circular and continuous.

[0044] Since the casing is made up of a continuous winding over several turns of the woven strip layer forming the preform, the insert can be formed from a succession of pieces joined end to end to produce a continuous assembly.

[0045] According to another variant, each of the upstream and downstream inserts is an elongated strip formed by a succession of independent parts 31 L (as illustrated for example, and in a non-limiting manner, in [Fig.5B].

[0046] Generally, the insert can be inserted on a single turn (as illustrated in Figures 5A and 5B) or on all of the turns.

[0047] With reference to [Fig. 6], which represents a variant of positioning or integration of the insert in the casing of the housing, the upstream and downstream inserts can be arranged axially inside the layer of woven strip forming the preform.

[0048] Indeed, due to its 3D woven material structure, the woven strip layer forming the preform comprises a set of sub-layers making it possible to add the insert inside the same ply. In the example of [Fig.6], the composite ply C 3 is untied (separated into 2 parts locally) for the positioning or arrangement of the insert.

[0049] The insert can be positioned on all interfaces including on the internal or external surface, the insertion being carried out on an axially restricted zone.

[0050] With reference to [Fig.7], each of the upstream 310a and downstream 310b inserts has an axial length or dimension La which represents between 1% and 10% of an internal diameter of the casing. Preferably, the axial length La is approximately 5% 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.

[0051] However, the axial position of the zone may be different from one design to another of the casing 200.

[0052] The upstream insert 310a and / or downstream insert 310b has an elliptical or trapezoidal or circular or rectangular shape in axial section. Inserts may also be integrated having an identical or different shape in axial section. For example, and in a non-limiting manner, the upstream insert 310a may have a trapezoidal shape in axial section and the downstream insert 310b an elliptical shape.

[0053] Each of the upstream and downstream inserts is made of a metal alloy. For example, and in a non-limiting manner, the inserts are made of a titanium alloy or steel.

[0054] Thus, the preform and the insert are made of materials with different characteristics. The metal alloy is made so as to have, for example, and in a non-limiting manner, a stiffness ranging from 110 to more than 200 GPa while the injected 3D woven composite material (organic matrix composite or OMC) has a stiffness which can range from 50 to 100 GPa.

[0055] In another embodiment, illustrated in [Fig.8], the casing may comprise an insert integrated into an angular portion of the annular casing of the casing and capable of protecting at least one accessory fixed to the external surface of the casing 202 of the casing 200.

[0056] In this embodiment, the axial length of the insert may be greater than previously described in order to provide protection of the at least one accessory over a sufficient length.

[0057] Advantageously, the person 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 of avoiding degradation of the structure of the casing and the turbomachine. The mechanical strength of the casing is therefore improved or reinforced.

[0058] The invention also allows a gain in mass and a reduction in the ecological footprint relating to manufacturing. Indeed, by stopping or reducing the wave of deformation, the insert prevents damage to the casing. In other words, the insert provides better mechanical strength for the casing. This improved strength makes it possible to reduce the thickness of the casing or to remove elements such as stiffeners, and therefore to achieve a weight saving.

[0059] 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 (200) having an annular shape around an axis (A) and comprising at its axial ends annular fastening flanges (204i, 2042), 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 winding around said axis on several superimposed turns (C1.4) a layer of woven strip forming a preform, and a polymer matrix in which this winding is embedded, characterized in that it further comprises an upstream annular stiffening insert (310a) integrated into said winding and axially interposed between the upstream flange (2041) and said section (202a), and a downstream annular stiffening insert (310b) integrated into said winding and axially interposed between the downstream flange (2042) and said section (202a).

2. A casing (200) according to claim 1, wherein each of the upstream (310a) and downstream (310b) inserts has an axial length or dimension (La) which represents between 1% and 10% of an internal diameter of the casing (200).

3. Casing (200) according to one of claims 1 to 2, in which each of the upstream (310a) and downstream (310b) inserts is wound with the layer of woven strip forming the preform over at least one turn around the axis (A).

4. Casing (200) according to one of claims 1 to 3, in which each of the upstream (310a) and downstream (310b) inserts is arranged axially between two superimposed turns (C2, C3) of the layer of woven strip forming the preform or inside the layer of woven strip.

5. Housing (200) according to one of claims 1 to 4, in which each of the upstream (310a) and downstream (310b) inserts is a strip of elongated and continuous shape.

6. Casing (200) according to one of claims 1 to 4, in which each of the upstream (310a) and downstream (310b) inserts is an elongated strip formed by a succession of independent parts (31 la_d).

7. Casing (200) according to one of claims 1 to 6, in which each of the upstream (310a) and downstream (310b) inserts is made of a metal alloy, and for example of a titanium or steel alloy.

8. Casing (200) according to one of claims 1 to 7, in which each of the upstream (310a) and downstream (310a) inserts has an elliptical or trapezoidal or circular or rectangular shape in axial section.

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

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