FR3152039A1 - single-block turbomachine blade - Google Patents

Abstract

The invention relates to a blade (7) for a turbomachine comprising: - a sleeve (13), comprising a fixing portion (14) configured to be connected to a variable pitch mechanism of a turbomachine, a through recess (17) being formed in the fixing portion (14) of the sleeve (13), the recess (17) being delimited by an inner wall of the sleeve (13); - a fibrous structure (20) obtained by three-dimensional weaving of strands, the fibrous structure (20) comprising: - a blade root (22) comprising an attachment portion (23) configured to be inserted into the recess (17) of the fixing portion (14) of the sleeve (13), - an aerodynamically profiled blade (12) connected to the blade root (22); - an insert (24), configured to be inserted into the recess (17) of the fixing part (14) of the sleeve (13) and to press the blade root (22) against the internal wall (18) of the sleeve (13). Figure for the abstract: Fig. 4c

Description

one-piece turbomachine blade Scope of the invention

The invention relates generally to the field of turbomachinery, and in particular to turbomachine blades.

The invention relates more particularly, but not exclusively, to a blade intended for use in an unfaired fan rotor of an aircraft engine.

Technological background

The advantage of unfaired fan engines is that the fan diameter is not limited by the presence of a shroud, making it possible to design an engine with a high bypass ratio (known as the "By Pass Ratio" or BPR), and consequently, reduced fuel consumption. Therefore, in this type of engine, the fan blades can have a large span.

In addition, these engines generally include a mechanism to change the angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

However, the design of such blades requires taking into account conflicting constraints.

On the one hand, the sizing of these blades must allow for optimal aerodynamic performance, notably maximizing efficiency and providing thrust while minimizing losses. Improving the aerodynamic performance of the fan tends towards an increase in the bypass ratio, which translates into an increase in the external diameter, and therefore the span, of these blades.

On the other hand, it is also necessary to guarantee resistance to the mechanical stresses that can be exerted on these blades while limiting their acoustic signature.

Furthermore, on unshrouded fan designs, engine start-up is generally performed with a very open timing setting. Indeed, a very open timing setting allows power to be consumed by torque, which ensures machine safety by guaranteeing low fan speeds.

However, with a very open pitch, the blades experience turbulent, completely separated aerodynamic flow, which generates broadband vibrational excitation. In particular, on blades with a wide chord and large span, the bending stress is intense, even though the engine speed is not at its maximum.

In normal operation, that is, during ground and flight phases, the fan pitch is adjusted to a more closed angle. The aerodynamic flow is then perfectly controlled, particularly in relation to the airfoil. Broadband stresses disappear because the rotational speed is higher, and the bending force is controlled. However, since the engine is not enclosed in a cowling, the angle of attack experienced by the various fan blades, depending on their angular position, varies according to the aircraft's angle of attack, creating a cyclic bending moment (commonly called the 1P moment) on the blades. This cyclic bending moment then generates significant bending stresses on the blades in addition to the centrifugal forces due to their rotation.

These blades can be made of metallic material. While metallic blades have good mechanical resistance, they have the disadvantage of being relatively heavy.

Manufacturing blades from composite materials is an attractive solution for reducing blade weight. However, composite blades can be fragile due to the intense aerodynamic stresses they are subjected to. These aerodynamic stresses can therefore damage the blades and/or the hub in the interface area between the blades and the fan rotor hub, at the blade root.

To overcome these drawbacks, various solutions exist in the prior art. Most use reinforcing elements, particularly at the blade root, and add various structural elements to allow, for example, the blade to be attached to the leveling mechanism. Patent documents WO2022/018353 and WO2022/208002 describe the addition of reinforcing and structural elements, particularly at the blade roots.

However, these solutions have the drawback of requiring the manufacture of several components from potentially different materials and the assembly of these components using fastening methods. Such blades can therefore be relatively time-consuming to produce.

BRIEF DESCRIPTION OF THE INVENTION

One of the aims of the invention is therefore to propose a blade adapted for use with a variable pitching mechanism and in an "Open Rotor" type environment while being able to withstand intense aerodynamic forces, under the constraint of limited size and minimum mass, the blade comprising a limited number of structural elements and being quick to manufacture.

Another objective of the invention is to provide a blade comprising a composite material and adapted for use with a variable pitching mechanism and in an "Open Rotor" type environment which includes a limited number of structural elements and which can be made simply and quickly, without requiring a large number of operations.

For this purpose, according to a first aspect of the invention, a blade for a turbomachine comprising:
- a sleeve, comprising a fixing part configured to be connected to a variable stalling mechanism of a turbomachine, a through recess being formed in the fixing part of the sleeve, the recess being delimited by an internal wall of the sleeve;
- a fibrous structure obtained by three-dimensional weaving of strands, the fibrous structure comprising:
- a blade foot comprising a portion of attachment configured to be inserted into the recess of the fixing part,
- a blade with an aerodynamic profile connected to the base of the blade;
- an insert, configured to be inserted into the recess of the sleeve's fixing part and to press the blade foot against the inner wall of the sleeve.

The blade is thus formed from a few elements that fit together to form a single piece. Since the blade and the blade root are formed from the same fibrous structure, there is no discontinuity between the blade and the root. Furthermore, the blade root is sandwiched between the insert and the sleeve, and the fibrous structure is thus securely bonded to the blade root.

• le pied de pale comprend en outre une jupe s’étendant autour de la portion d’attache du manchon et la partie de fixation comprend en outre un flasque annulaire, et une face d’extrémité de la jupe du pied de pale est configurée pour venir en appui contre le flasque ;
• la paroi interne du manchon comporte une portion en creux entrainant un élargissement de l’évidement dans une direction radiale et la portion d’attache comporte une surépaisseur configurée pour se loger dans la portion en creux ;
• le manchon comporte en outre une partie de liaison monobloc avec la partie de fixation et dans laquelle se prolonge l’évidement, le pied de pale étant configuré pour être inséré dans la partie de liaison ;
• la partie de liaison du manchon s’étend entre la portion d’attache et la jupe du pied de pale ;
• le manchon comprend en outre une butée s’étendant depuis la paroi interne, l’insert étant configuré pour plaquer le pied d’aube contre la butée ;
• la butée est formée par une réduction de section de l’évidement dans la partie de liaison du manchon ;
• une section transversale de la partie de liaison du manchon est aplatie dans une direction ;
• la partie de fixation du manchon présente une surface externe ayant une forme de révolution dans laquelle est formée au moins une gorge circulaire propre à former un chemin de roulement pour au moins un roulement ;
• la partie de fixation du manchon présente une forme de révolution et la partie de liaison du manchon comprend une première portion, raccordée à la partie de fixation, et une deuxième portion raccordée à la première portion, la première portion présentant une forme de révolution dont une section décroît de la partie de fixation du manchon en direction de la deuxième portion, la deuxième portion présentant une section transversale réduite dans une direction de l’espace ; et
• le manchon est métallique.

The blade can thus withstand significant aerodynamic forces while maintaining a limited mass, and can therefore be used with a variable pitch mechanism and in an open rotor environment. Furthermore, since the blade's components are limited in number, it is quick to manufacture. According to specific embodiments of the invention, which may be used alone or in combination:

• the blade foot further includes a skirt extending around the attachment portion of the sleeve and the attachment part further includes an annular flange, and an end face of the blade foot skirt is configured to bear against the flange;
• the inner wall of the sleeve has a hollow portion causing a widening of the recess in a radial direction and the attachment portion has an extra thickness configured to fit into the hollow portion;
• the sleeve also includes a one-piece connecting part with the fixing part and into which the recess extends, the blade foot being configured to be inserted into the connecting part;
• the connecting part of the sleeve extends between the attachment portion and the blade foot skirt;
• the sleeve further includes a stop extending from the inner wall, the insert being configured to press the blade foot against the stop;
• the stop is formed by a reduction in the cross-section of the recess in the connecting part of the sleeve;
• a cross-section of the connecting part of the sleeve is flattened in one direction;
• the fixing part of the sleeve has an external surface having a shape of revolution in which is formed at least one circular groove suitable for forming a raceway for at least one bearing;
• The fixing portion of the sleeve has a shape of revolution, and the connecting portion of the sleeve comprises a first portion, connected to the fixing portion, and a second portion connected to the first portion, the first portion having a shape of revolution whose cross-section decreases from the fixing portion of the sleeve towards the second portion, the second portion having a reduced cross-section in a spatial direction; and
• The sleeve is metallic.

According to a second aspect, the invention proposes a method for manufacturing a blade according to the first aspect, said method comprising the following steps:
- to create the fibrous structure including the attachment portion by three-dimensional weaving,
- Insert the attachment portion into the recess in the sleeve and against the inner wall,
- Position the insert in the recess so as to lock the attachment portion against the inner wall, and
- insert the fibrous structure, the sleeve and the insert into a mold to obtain a preform with an aerodynamic profile.

The process may further include a step of injecting a resin into the mold, after insertion of the fibrous structure, the sleeve and the insert into said mold, so as to obtain the blade according to the first first aspect, said blade being monobloc.

The process may also include a step of positioning the blade foot skirt on the connecting part before inserting the fibrous structure, sleeve and insert.

Furthermore, the fabrication of the fibrous structure may involve the creation of a first and a second tab, each having two beveled lateral edges along at least part of its length, intended to form the attachment portion together. During insertion of the fibrous structure into the mold, the first and second tabs may be joined by pairing the beveled lateral edges of the first tab with the beveled lateral edges of the second tab to form a cylindrical attachment portion.

According to a third aspect, the invention proposes a blower comprising at least one blade according to the first aspect or obtained according to the process of the second aspect.

According to a fourth aspect, the invention proposes a turbomachine comprising a blower according to the third aspect.

According to a fifth aspect, the invention proposes an aircraft comprising a blower according to the third aspect or a turbomachine according to the fourth aspect.

Brief description of the Figures

Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which:

FIG. 1 There FIG. 1 schematically represents an example of an engine including an unfaired fan;

FIG. 2 There FIG. 2 schematically represents a blower blade according to an embodiment of the invention assembled to a shimming mechanism;

FIG. 3 There FIG. 3 schematically represents a blower blade according to a first embodiment of the invention;

FIG. 4 There FIG. 4 schematically represents a sleeve according to a first embodiment of the invention in perspective view;

FIG. 4 There FIG. 4 schematically represents the sleeve of the FIG. 4 according to a profile view;

FIG. 4 There FIG. 4 schematically represents the sleeve in figures 4a and 4b into which the attachment portion and the insert are inserted;

FIG. 4 There FIG. 4 schematically represents the sleeve/attachment/insert assembly of the FIG. 4 inserted into the locking mechanism;

FIG. 5 There FIG. 5 schematically represents a fibrous structure according to a partial and front view embodiment;

FIG. 5 There FIG. 5 schematically represents the fibrous structure of the FIG. 5 according to a cross-sectional view;

FIG. 5 There FIG. 5 schematically represents the attachment portion of the fibrous structure in figures 5a and 5b according to a cross-sectional view;

FIG. 6 There FIG. 6 schematically represents an insert according to one embodiment of the invention;

FIG. 7 There FIG. 7 schematically represents a sleeve according to a second embodiment of the invention in perspective view;

FIG. 7 There FIG. 7 schematically represents the sleeve of the FIG. 7 according to a profile view;

FIG. 7 There FIG. 7 schematically represents a blower blade according to a second embodiment of the invention;

FIG. 8 There FIG. 8 schematically represents a manufacturing process for a blade according to one embodiment of the invention;

FIG. 9 There FIG. 9 represents the dawn obtained according to the process of the FIG. 8 front view; and

FIG. 9 There FIG. 9 represents the dawn obtained according to the process of the FIG. 8 in profile view.

Detailed description of an example of implementation

On the FIG. 1 The engine 1 shown is an "Open Rotor" type engine, in a configuration commonly referred to as "pusher" (i.e., the blower is placed at the rear of the power generator with an air intake located on the side, to the right on the FIG. 1 ).

The engine comprises a nacelle 2 intended to be fixed to an aircraft fuselage, and an unfaired fan 3. The fan 3 comprises two counter-rotating fan rotors 4 and 5. In other words, when the engine 1 is running, the rotors 4 and 5 are driven in rotation relative to the nacelle 2 around the same axis of rotation X (which coincides with a principal axis of the engine), in opposite directions.

In the example shown on the FIG. 1 The motor 1 is an "Open Rotor" type motor, in a "pusher" configuration, with counter-rotating fan rotors. However, the invention is not limited to this configuration. The invention also applies to "Open Rotor" type motors, in a "puller" configuration (i.e., the fan is placed upstream of the power generator with an air inlet located before, between, or just behind the two fan rotors).

Furthermore, the invention also applies to motors with different architectures, such as an architecture comprising a blower rotor with moving blades and a blower stator with fixed blades, or a single blower rotor.

The invention is applicable to turboprop type architectures (comprising a single fan rotor).

On the FIG. 1 , each blower rotor 4, 5 comprises a hub 6 mounted rotatably relative to the nacelle 2 and a plurality of blades 7 according to an embodiment of the invention, said blades being fixed to the hub 6. The blades 7 extend substantially radially relative to the axis of rotation X of the hub.

As illustrated on the FIG. 2 The fan 3 further includes an actuation mechanism 8 for collectively adjusting the pitch angle of the rotor blades to adapt engine performance to different flight phases. For this purpose, each blade 7 comprises a blade root 9 and an aerodynamically profiled blade 12. The blade root 9 is rotatably mounted relative to the hub 6 around a pitch axis Y. More precisely, the blade root 9 is rotatably mounted within a mounting device 10 formed in the hub 6, via balls 11 or other rolling elements.

The aerodynamically profiled blade 12 has a first end connected to the blade root 9 and a second end, opposite the first end. The aerodynamically profiled portion of the blade 12 is designed to extend into an air stream within the engine, when the engine is running, in order to generate lift. Conversely, the blade root 9 is designed to extend out of the air stream.

According to a first embodiment described with reference to Figures 3, 4a and 4b, the blade 7 includes a sleeve 13 having a fixing part 14 configured to be connected to a variable pitching mechanism of a turbomachine, in particular inside the attachment device 10. The sleeve 13 has a recess 17 delimited by an internal wall 18 of the sleeve 13.

With reference to Figures 3, 5a and 5b, the blade 7 also includes a fibrous structure 20 obtained by three-dimensional weaving. The fibrous structure 20 includes a blade root 22 comprising an attachment portion 23 configured to be inserted into the recess 17 formed by the attachment portion 14 of the sleeve 13.

The fibrous structure 20 also includes a blade 21 with an aerodynamic profile connected to the blade root 22.

Dawn 7 also includes an insert 24 shown on the FIG. 6 and which is configured to be inserted into the recess 17 of the fixing part 14 of the sleeve and to press the blade foot 22 against the inner wall 18 of the sleeve 13.

The blade 7 is thus formed from a few elements that fit together to form a single-piece blade. Since the blade 21 and the blade root 22 are formed from the same fibrous structure 20, there is no discontinuity between the blade 21 and the blade root 22. Furthermore, the blade root 22 is wedged between the insert 24 and the sleeve 13, and the fibrous structure 20 is thus securely joined to the blade root 9.

The blade 7 can therefore withstand significant aerodynamic stresses while maintaining a limited mass, and can thus be used with a variable pitch mechanism and in an "open rotor" type environment. Furthermore, since the components of the blade 7 are limited in number, it is quick to manufacture.

With reference to the FIG. 5 The blade root 22 also includes a skirt 25 which extends around the attachment portion 23. The skirt 25 is formed by the same fibrous structure 20 as the blade 21 and the attachment portion 23. Thus, the attachment portion 23 on the one hand, and the skirt 25 on the other hand, are formed by the extension of the strands forming the blade 21. This continuity between the blade 21 and the attachment portion 23, and between the blade 21 and the skirt 25, allows the blade 7 to resist the aerodynamic forces it is subjected to in an optimized manner.

The fibrous structure 20, and in particular the aerodynamically profiled blade 12, is suitable for being placed in an airflow when the engine is in operation in order to generate lift.

As illustrated on the FIG. 5 The fibrous structure 20 comprises two skins 22', which are connected to each other and extend generally opposite one another. The skins 22' are shaped to define together an intrados I, an extrados E, a leading edge 15, and a trailing edge 15'. As is known, the leading edge 15 is configured to extend in line with the flow of gases entering the turbomachine. It corresponds to the forward part of an airfoil that faces the airflow and divides the airflow into an intrados flow and an extrados flow. The trailing edge 15', for its part, corresponds to the rear part of the airfoil, where the intrados and extrados flows meet.

The skins 22’ of the aerodynamically profiled structure are made of a composite material comprising the fibrous structure 20 densified by a matrix. They are therefore monolithic and are made in one piece according to a non-limiting embodiment.

The matrix typically comprises an organic material (thermoset, thermoplastic, or elastomer) or a carbon matrix. For example, the matrix may include a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide. The fibers of the fibrous structure comprise at least one of the following materials: carbon, glass, aramid, polypropylene, and/or ceramic. The matrix and fibers of composite materials.

The attachment portion 23 and the skirt 25 are formed by unlinking in the three-dimensional weave. Preferably, at least part of the strands forming the attachment portion 23 and/or the skirt 25 extend from a free end 28 of the blade 12 to a free end 23’ of the attachment portion 23 and/or a free end 25’ of the skirt 25.

In this way, the three-dimensional structure of the fibrous structure 20 extends into the sleeve 13 and optionally around it, and this continuity contributes to the resistance of the blade to the aerodynamic forces it undergoes.

Regarding the formation of attachment portion 23 and as illustrated on the FIG. 5 Each skin has a tab 60 (62) positioned opposite the free end 28. The tab 60 of one skin is designed to be joined with the tab 62 of the other skin to form the cylindrical attachment portion 23. The tabs 60 and 62 are formed during the flat weaving process. The preform of the fibrous structure 20 is divided in two through its thickness by creating unbundles. This results in the independent, flat tabs 60 and 62, each of which is connected to one of the skins 22' due to the continuity of the strands. This continuity of the strands allows the transfer of mechanical loads between the blade 21 and the blade root 22.

As described in more detail later, the flat tabs 60 and 62 are then shaped into a half-cylinder to form a cylindrical attachment portion 23.

Furthermore, each tab 60 (62) has a first lateral edge 60a (62a) and a second lateral edge 60b (62b) which are beveled along at least part of their length. As shown in the FIG. 5 , the two tabs 60 and 62 are assembled by joining the beveled edges in pairs so as to form the cylindrical attachment portion 23 which has a relatively constant thickness over its entire circumference.

With reference to Figures 4c, 4b, and 4c, the attachment portion 23 further includes an additional thickness 23'' resulting from a progressive thickening of the fibrous structure 20 forming said attachment portion 23, at its free end 23'. This additional thickness 23'' is configured to fit into a recessed portion 18' of the inner wall 18. Thus, the portion 18' widens the recess 17, and the remainder of the wall portion 18 narrows the recess 17. In this way, when the insert is positioned in the recess 17, any translation of the attachment portion 23 away from the free end 23' is prevented by the portion of the wall 18 that narrows the recess 17 and forms a stop.

Indeed, when the fan is rotating, the blade 7 is subjected to centrifugal forces oriented radially with respect to the fan's axis of rotation, which tend to separate the aerodynamically profiled blade 12 from the sleeve 13. The extra thickness 23" helps prevent the separation of the blade 12 and the sleeve 13. The blade 7 may also include one or two cavities, preferably two cavities 26, each accommodating a shaping piece 27. The cavities 26 are formed by debonding in the weave. Each shaping piece 27 is formed from a rigid and lightweight material so as to reduce the mass of the blade 12 while allowing it to maintain its aerodynamic shape.

The rigid material forming the conforming part(s) is preferably honeycomb-shaped, for example a foam, and made, for example, of pre-machined polymethacrylimide (PMI). Alternatively, the rigid honeycomb material can be a pre-sealed aluminum honeycomb material.

The shaping piece(s) 27 allows the desired thickness and shape to be given to the aerodynamic profile blade 12 of the blade 7, while using a lighter material than other elements of the blade.

However, according to one possible embodiment, the cavities may remain empty and not be filled by filler pieces.

According to this first embodiment and with reference to figures 3, 4a to 4d, the fixing part 14 has a rotational symmetry around the Y axis. Furthermore, the fixing part 14 has an external surface 30 having different reliefs.

The fixing part 14 has at its end through which the attachment portion 23 is inserted a first annular flange 29. This first annular flange 29 forms a stop against which an end face 25’ of the skirt 25 of the blade foot 22 is configured to bear.

The fixing part 14 also includes a second annular flange 29’ at its free end opposite to the end through which the fibrous structure 20 is inserted.

The mounting portion 14 also includes a first circular groove 32 and a second circular groove 34, enabling the formation of a raceway on at least one bearing, for example, a ball bearing. The mounting portion 14 thus allows the blade foot 9 to be rotatably mounted within the attachment device 10 provided in the hub 6.

Sleeve 13 is preferably metallic and monolithic.

As previously described, the sleeve 13 has an inner wall 18 that defines the recess 17. In this first embodiment, the recess 17 forms a cylinder of constant diameter that widens as it approaches the free end of the sleeve 13, forming a beveled inner edge. The wall 18 thus has a recessed portion 18' that widens the recess 17 in a radial direction. The extra thickness 23'' of the attachment portion 23 is then inserted into the recessed portion 18' so as to prevent any translation of the attachment portion 23 away from the free end 23' when the insert 24 is positioned in the recess 17. The portion of the wall 18 with a constant diameter then acts as a stop for the extra thickness 23''.

According to one possible embodiment, the recessed portion may have a different shape and may be placed in a different position along wall 18.

Furthermore, according to another unrepresented embodiment, the wall 18 can be thickened at its end opposite the free end so as to reduce the diameter of the recess 17 and form a stop allowing the insert 24 to be blocked and the attachment portion 23 to be wedged against the wall 18 in an optimized manner.

There FIG. 4 represents the sleeve into which the attachment portion 23 and the insert 24 are inserted, the sleeve being disposed in the attachment device 10, the rolling elements 11 being disposed in the circular grooves 32 and 34.

With reference to the FIG. 6 The insert 24 comprises a cylindrical body 40 having a free end 41 and a locking end 42 opposite the free end 41. In this embodiment, the locking end 42 is rounded. According to the variant in which the sleeve 13 has a stop, the rounded locking end 42 allows the insert 24 to wedge the attachment portion 23 against the stop.

According to other possible embodiments, the locking end can have a different shape that can adapt to a stop that can also have a different shape.

Insert 24 is preferably metallic.

According to a second embodiment illustrated in figures 7a, 7b and 7c, the sleeve 13 differs from the first embodiment in that it includes a connecting part 16 which extends the sleeve 13 longitudinally from the annular flange 29. The recess 17 and the internal wall 18 delimiting the recess 17 then extend inside the connecting part 16.

The connecting part 16 of the sleeve 13 comprises a first portion 37, connected to the fixing part 14, and a second portion 38 connected to the first portion 37, the first portion 37 having a shape of revolution whose section decreases from the fixing part 14 of the sleeve 13 towards the second portion 38, the second portion 38 having a reduced cross-section in a direction of space, in particular along an axis perpendicular to the X axis and the Y axis.

In other words, according to a profile view of the blade 7, the connecting part 16 of the sleeve 13 has a cross-section that decreases with distance from the fixing part 14 and is thus flattened in a direction perpendicular to the X and Y axes. This reduction in cross-section allows the connecting part 16 to fit within the aerodynamic profile of the fibrous structure 20. The recess 17 also has a reduced cross-section, enabling it to form a stop 36.

When the blade foot 22 is positioned inside the sleeve 13, it then extends against at least part of the main portion 19 and inside the connecting part 16 and in particular against the stop 36.

This stop 36 allows the insert 24 to press the blade foot 22 against the inside of the sleeve 13, and in particular against the inner wall 18. For this purpose, the insert 24 has a shape complementary to at least part of the inner wall 18, in particular the entire inner portion of the fixing part 14 up to the stop 36.

The connecting part 16 of the sleeve 13, according to a front view of the blade 7, has a section which increases in distance from the fixing part 14 and has in particular a dovetail shape.

This shape is adapted to the complementary shape of the skirt 25 which can thus receive the connecting part 16 of the sleeve 13 so that the connecting part 16 of the sleeve 13 extends between the attachment portion 23 and the skirt 25 of the blade root 22. The skirt 25 thus surrounds the connecting part 16 so as to be in contact with its outer surface and the attachment portion 23 is then pressed against the inner surface of the connecting part 16.

The skirt 25 thus constitutes an additional element for assembling the fibrous structure 20 to the sleeve 13.

The skirt 25 has a shape complementary to the shape of the connecting part 16 of the sleeve 13. Preferably, the skirt 25 has a dovetail shape, the narrowest part being located at the free end of the skirt 25, which is the end closest to the fixing part 14.

Thus, the assembly between the fibrous structure 20 and the sleeve 13 can withstand the centrifugal force exerted on the blade 21 when the blade 7 is rotating.

Indeed, when the fan is rotating, the blade 7 is subjected to centrifugal forces oriented in a radial direction with respect to the axis of rotation of the fan, which tend to separate the aerodynamic profile blade 12 from the sleeve 13. The attachment portion 23 and the skirt 25, by their shape and the way in which they are assembled with the sleeve 13 and the insert 24, prevent the separation of the blade 12 and the sleeve 13.

The sleeve 13 is preferably metallic and monolithic. The fixing part 14 and the connecting part 16 are thus inseparable and remain firmly aligned despite the aerodynamic forces exerted on the blade 7.

According to the second embodiment, the cylindrical body 40 closely fits the main portion 19 and the locking end 42 closely fits the stop 36, which means that when the blade foot 22 is positioned in the recess 17 and the insert is also positioned in the recess 17, the blade foot 22 is in contact with the main portion 19, the stop 36 and at least a part of the cylindrical body 40 and the locking end 42.

According to a preferred variant of this second embodiment, the sleeve 13 also has a hollow portion 18’ described for the first embodiment and allowing to accommodate an extra thickness 23’ of the fibrous structure 20.

According to another variant of the second embodiment, the connecting part can be shorter and, for example, only include the first cylindrical portion 37.

Blade manufacturing process

With reference to the FIG. 8 , a manufacturing process 50 of a blade 7 includes a step 51 consisting of producing the fibrous structure 20 comprising the attachment portion 23 by three-dimensional weaving, the attachment portion 23 being produced by forming unlinks in the weaving.

Preferably, this step also includes the manufacture of the skirt 25 in the fibrous structure 20 by also making unbindings in the weaving.

Furthermore, the weaving is carried out in such a way as to form the two cavities 26 into which shaping pieces 27 are inserted.

The process 50 then includes step 52, which consists of inserting the attachment portion 23 into the recess 17 of the sleeve 13 and positioning said attachment portion 23 against the inner wall 18.

In a step 53, the insert 24 is positioned in the recess 17 so as to block the attachment portion 23 against the inner wall 18. Preferably, the cylindrical body 40 blocks a part of the attachment portion 23 against the main portion 19 and the locking end 42 blocks another part of the attachment portion 23 against the stop 36.

Preferably, the process 50 further includes a step 54 of positioning the skirt 25 of the blade foot 22 on the connecting part 16 so that the skirt 25 is pressed against the connecting part 16.

Once the fibrous structure 20, the sleeve 13, and the insert 24 are assembled, the resulting blade 7 is inserted into a mold to obtain a preform with an aerodynamic profile. In step 55, a liquid resin is then injected into the mold using the RTM process to obtain the one-piece blade 7 shown in Figures 9a and 9b. The resin can be, in particular, an epoxy resin, a thermoplastic resin, or a polybismaleimide (BMI) resin.

During the injection of the resin, the latter impregnates the entire fibrous structure 20 and thus inserts itself in particular between the insert 24 and the wall 18 and around the connecting part 16. The resin thus makes it possible to maintain the different assembled elements, namely the fibrous structure 20, the sleeve 13 and the insert 24, in a single block.

Preferably, embodiment 51 of the fibrous structure 20 comprises a first tab 60 and a second tab 62, the first and second tabs 60 and 62 each having two beveled lateral edges 60a,b and 62a,b over at least part of their length. The beveled lateral edges are intended to form together the attachment portion 23. During insertion 55 of the fibrous structure 20 into the mold, the first and second tabs 60 and 62 are assembled by joining in pairs the beveled lateral edges 60a and 60b of the first tab 60 with the beveled lateral edges 62a and 62b of the second tab 62 so as to form a cylindrical attachment portion 23.

Claims (15)

Blade (7) for a turbomachine comprising:
- a sleeve (13), comprising a fixing part (14) configured to be connected to a variable timing mechanism of a turbomachine, a through recess (17) being formed in the fixing part (14) of the sleeve (13), the recess (17) being delimited by an internal wall of the sleeve (13);
- a fibrous structure (20) obtained by three-dimensional weaving of strands, the fibrous structure (20) comprising:
- a blade foot (22) comprising an attachment portion (23) configured to be inserted into the recess (17) of the fastening part (14) of the sleeve (13),
- an aerodynamically profiled blade (12) connected to the blade root (22);
- an insert (24), configured to be inserted into the recess (17) of the fixing part (14) of the sleeve (13) and to press the blade foot (22) against the inner wall (18) of the sleeve (13).
Blade according to claim 1, wherein the blade foot (22) further comprises a skirt (25) extending around the attachment portion (23) of the sleeve (13) and the attachment portion (14) further comprises an annular flange (29), and wherein an end face (25’) of the skirt (25) of the blade foot (22) is configured to bear against the flange (29). Blade according to claim 1 or 2, wherein the inner wall of the sleeve has a hollow portion causing an enlargement of the recess (17) in a radial direction and wherein the attachment portion (23) has an overthickness (23’’) configured to fit into the hollow portion. Blade according to any one of claims 1 to 3, wherein the sleeve (13) further comprises a one-piece connecting part (16) with the fixing part (14) and in which the recess (17) extends, the blade foot being configured to be inserted into the connecting part (16). Blade according to claim 4 when it depends on claim 2, wherein the connecting part (16) of the sleeve (13) extends between the attachment portion (23) and the skirt (25) of the blade foot (22). Blade according to any one of claims 1 to 5, wherein the sleeve (13) further comprises a stop (36) extending from the inner wall (18), the insert (24) being configured to press the blade root (22) against the stop (36). Blade according to claim 6 when it depends on claims 4 or 5, wherein the stop (36) is formed by a reduction in cross-section of the recess (17) in the connecting part (16) of the sleeve (13). Blade according to any one of claims 4 to 7, wherein a cross-section of the connecting part (16) of the sleeve (13) is flattened in one direction. Blade according to any one of claims 4 to 8, wherein the fixing part (14) of the sleeve (13) has a shape of revolution and the connecting part (16) of the sleeve (13) comprises a first portion (37), connected to the fixing part (14), and a second portion (38) connected to the first portion (37), the first portion (37) having a shape of revolution, a section of which decreases from the fixing part (14) of the sleeve (13) towards the second portion (38), the second portion (38) having a reduced cross-section in a direction of space. Blade according to any one of claims 1 to 9, wherein the fixing part (14) of the sleeve (13) has an external surface (30) having a shape of revolution in which is formed at least one circular groove (32, 34) suitable for forming a raceway for at least one bearing. Blade according to any one of claims 1 to 10, wherein the sleeve (13) is metallic. A method for manufacturing a blade according to any one of claims 1 to 11, comprising the following steps:
- to produce (51) the fibrous structure (20) comprising the attachment portion (23) by three-dimensional weaving,
- insert (52) the attachment portion (23) into the recess (17) of the sleeve (13) and against the inner wall (18),
- position (53) the insert (24) in the recess (17) so as to lock the attachment portion (23) against the inner wall (18), and
- insert (55) the fibrous structure (20), the sleeve (13) and the insert (24) into a mold to obtain a preform with an aerodynamic profile. Method according to claim 12, further comprising a step (55) consisting of injecting a resin into the mold, after insertion of the fibrous structure (20), the sleeve (13) and the insert (24) into said mold, to obtain the blade (7) according to any one of claims 1 to 11, said blade being monobloc. Manufacturing method according to claim 12 or 13 when they depend on claim 4, further comprising a step (54) of positioning the skirt (25) of the blade foot (22) on the connecting part (16) before inserting the fibrous structure (20), the sleeve (13) and the insert (24). A manufacturing method according to any one of claims 12 to 14, wherein the realization (51) of the fibrous structure (20) comprises the realization of a first tab and a second tab, the first and second tabs each having two lateral edges beveled over at least part of their length and being intended to form together the attachment portion (23), and wherein, during the insertion (55) of the fibrous structure (20) into the mold, the first and second tabs are assembled by joining two by two the beveled lateral edges of the first tab with the beveled lateral edges of the second tab so as to form a cylindrical attachment portion (23).