Fixed bucket assembly including variable pitch bucket for turbine engine

Abstract

The invention relates to a vane (3) of a static vane assembly (2) of a turbomachine (1), comprising:-a vane root (8) comprising a fibrous reinforcement (13) comprising a first shell layer (12) and a second shell layer (12) separated by a cavity (14) opening onto a lower surface (15) of the vane root (8); -a fastener (6) configured to receive and attach the bucket root (8) to the hub (4) of the bucket assembly (2), the fastener (6) comprising a platform (16) and a rib (17) protruding from the platform (16), the rib (17) configured to enter into the cavity (14) to extend between the inner surface (12a) of the first shell layer (12) and the inner surface of the second shell layer (12); and-an attachment system (18) configured to mechanically attach the first shell layer (12) and the second shell layer (12) to the rib (17) of the fastener (6).

Description

Technical Field

[0001] The present invention relates to the field of turbomachines, and in particular to fixed blade assemblies of turbomachines, such as fixed blade assemblies comprising variable pitch stator blades, each variable pitch stator blade being attached to a pivot member. The present invention is particularly applicable to unducted guide blades of turbomachines or ducted guide blades of turbomachines. Background Art

[0002] A turbine comprising at least one unducted propeller is called an "open rotor" or "unducted fan" turbine. Such a turbine may comprise two unducted and counter-rotating propellers, known as a Contra-Rotating Open Rotor (CROR) or a single unducted propeller and guide vanes comprising a plurality of stator blades, known as an Unducted Single Fan (USF). The propeller may be arranged at the rear of the gas generator (or engine) so that the gas generator is of the push type, or at the front of the gas generator so that the gas generator is of the traction type. These turbines are turboprop engines, which differ from turbojets in that a propeller (unducted) is used outside the nacelle, instead of an internal fan. This makes it possible to increase the bypass ratio very significantly, without being affected by the mass of the casing or nacelle intended to surround the blades of the propeller or fan.

[0003] The stator blades of the guide vanes are usually mounted on a hub that carries splitters for the primary and secondary flows circulating in the main air path and around the inlet casing, respectively. Unlike the upstream propeller of a turbine of the Unducted Single Fan (USF) type, the stator blades of the guide vanes are rotationally fixed relative to the axis of rotation of the upstream propeller and are therefore not subject to any centrifugal forces.

[0004] The stator blades extend from the inlet housing, advantageously with variable pitch. To this end, each stator blade root is pivotably mounted along a pitch axis, each stator blade being connected to a pitch change system installed in the turbine. Since there are many equipment parts around the root and pivot of the stator blade, the integrated area of ​​the root and pivot of the stator blade is a high stress area.

[0005] Furthermore, in such turbines where weight reduction is desired, the stator vanes are preferably made of a composite material comprising fiber reinforcements embedded in an organic matrix.

[0006] However, current propeller attachment techniques do not meet the requirements for attaching stator blades of USF turbines because current propeller attachment techniques are configured to use the centrifugal force generated by the rotation of the blade assembly to press the root of the blade assembly down into the recessed attachment. However, in a static blade assembly, since there is no rotation and therefore no centrifugal force, this simple and well-known attachment method cannot be used. Therefore, the blades of the static blade assembly are usually attached to metal fasteners by bolting. However, these fasteners are bulky in the radial or tangential direction, which makes them difficult to incorporate into the turbine. Summary of the invention

[0007] An object of the present application is to remedy the above drawbacks by providing an attachment system for attaching variable pitch blades of a static blade assembly of a turbomachine, the attachment system having a reduced radial and tangential bulk while ensuring proper retention of the blades of the static blade assembly.

[0008] To this end, according to a first aspect, a blade of a static blade assembly of a turbine is provided, the blade comprising:

[0009] a blade root, the blade root comprising a fiber reinforcement embedded in a matrix, the fiber reinforcement comprising a first shell and a second shell separated by a cavity opening onto the lower surface of the blade root;

[0010] a fastener configured to receive the blade root and attach the blade root to a hub of the blade assembly, the fastener comprising a platform and a rib protruding from the platform, the rib being configured to enter the cavity to extend between an inner surface of the first shell and an inner surface of the second shell; and

[0011] - an attachment system configured to mechanically attach the first shell and the second shell to the ribs of the fastener.

[0012] Some preferred but non-limiting features of the blade according to the first aspect are the following features taken alone or in combination:

[0013] - the attachment system passes through the first shell, the ribs and the second shell;

[0014] - the rib comprises two side surfaces connected to the platform and a top end connecting the two side surfaces, the thickness of the rib decreases from the platform to the top end, and the inner surface of the shell can be more outwardly expanded than the side surfaces of the rib; in a variant, the rib comprises two side surfaces connected to the platform and a top end connecting the two side surfaces, the thickness of the rib is substantially constant from the platform to the top end; according to another variant, the rib comprises two concavely curved side surfaces, so that the thickness of the rib decreases from the platform to the top end;

[0015] - the first shell and the second shell also abut against the platform;

[0016] - the attachment system comprises at least one of the following elements: a bolt; a plate shaped to be in contact with the outer surface of the shell;

[0017] - the attachment system comprises a bolt which passes through the first shell, the rib and the second shell;

[0018] - the blade further comprises a shaped part housed in the cavity, remote from the top end of the rib;

[0019] the shaped part comprises an additional composite material comprising an additional fiber reinforcement embedded in an additional matrix, the additional fiber reinforcement comprising fibers having a Young's modulus at least equal to 5 GPa, such as carbon fibers, aramid fibers, glass fibers or basalt fibers;

[0020] - the blade further comprises a filling part housed in the cavity, between the tip of the blade and the shaped part, the filling part being able to comprise a material with a density less than that of the composite material;

[0021] the fiber reinforcement has an upstream edge and a downstream edge, the cavity also opening onto at least one of the upstream edge and the downstream edge; and / or

[0022] - The fastener is a pivoting element.

[0023] According to a second aspect, a static blade assembly of a turbomachine is provided, comprising at least one blade according to the first aspect and a hub, a fastener of the blade being pivotably mounted on the hub about a pitch axis.

[0024] According to a third aspect, a turbine is provided, comprising a static blade assembly according to the second aspect, the turbine further comprising a ducted fan or an unducted propeller, a compression section and a turbine section, the static blade assembly being at least one of the following blade assemblies: ducted guide blades of a fan, unducted guide blades of a propeller, guide blades of a compression section, and a nozzle of a turbine section.

[0025] According to a fourth aspect, there is provided an aircraft comprising at least one turbine according to the third aspect, the turbine being attachable to the aircraft using a pylon.

[0026] According to a fifth aspect, there is provided a method for manufacturing a blade according to the first aspect, the method comprising the following steps:

[0027] - producing a blade root comprising a fiber reinforcement embedded in a matrix, the fiber reinforcement comprising a first shell and a second shell separated by a cavity opening onto the lower surface of the fiber reinforcement;

[0028] - inserting the rib of the fastener into the cavity of the blade root so that the rib extends between the inner surface of the first shell and the inner surface of the second shell and the platform extends outside the cavity;

[0029] - Mechanically attaching the first shell and the second shell to the ribs of the fastener.

[0030] Optionally, before the step of inserting the ribs, the step of producing the blade root comprises the following sub-steps:

[0031] - inserting at least one filling component and at least one shaping component into the cavity in sequence;

[0032] - placing the assembly formed by the fiber reinforcement, the at least one filling component and the at least one shaped component into a mold, and

[0033] -Injection matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other characteristics, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and non-limiting and must be read with reference to the accompanying drawings, in which:

[0035] Figure 1 is a schematic cross-sectional view of an exemplary embodiment of a blade according to a first embodiment of the present invention;

[0036] Figure 2 is a schematic perspective view of an exemplary embodiment of a fiber reinforcement that can be used to produce a blade according to an embodiment of the present invention;

[0037] Figure 3 is a schematic cross-sectional view of an exemplary embodiment of a blade according to a second embodiment of the present invention;

[0038] Figure 4 is a schematic axial partial cross-sectional view of an example of a USF type turbine including a single unducted propeller and unducted guide vanes to which the present invention is applicable; and

[0039] Figure 5 is a schematic diagram of an example of an aircraft that may include at least one turbine according to an embodiment of the present invention.

[0040] In all the figures, similar elements have the same reference numerals. DETAILED DESCRIPTION

[0041] The turbomachine 1 , in particular a turbomachine 1 for an aircraft 100 , generally comprises at least one fan or at least one propeller 26 , a compression section 27 , a combustion chamber 28 , a turbine section 29 downstream of the combustion chamber 28 , and an exhaust casing.

[0042] The invention is applicable to any static (ie non-rotating) blade assembly 2 of a turbomachine 1, whether the static blade assembly 2 is a guide blade assembly 2 of a fan or propeller 26, a guide blade assembly 2 of a compression section 27, or a nozzle guide blade assembly 2 of a turbine section 29. As an example, the turbomachine 1 may be a USF type turboprop engine including an unducted propeller 26, in which case the static blade assembly 2 is unducted and extends downstream of the propeller (see Figure 4 In another example, the turbine 1 may be a turbojet engine including a ducted fan, in which case the static blade assembly 2 may be a ducted guide vane extending downstream of the fan, the ducted guide vane being referred to as an “outer guide vane”.

[0043] In the present application, upstream and downstream are defined relative to the flow direction of the gas through the static blade assembly 2. The term "X-axis" refers to the axis of rotation of the rotor of the propeller 26 (or fan). The axial direction corresponds to the direction of the axis X, and the radial direction is a direction perpendicular to the axis X and passing through the axis X. In addition, the circumferential (or tangential) direction corresponds to a direction perpendicular to the axis X but not passing through the axis X. Unless otherwise specified, "inner" and "outer" are used with reference to the radial direction, so that the interior or inner surface of an element is closer to the axis X than the exterior or outer surface of the same element.

[0044] The blades 3 will therefore be defined relative to the axis X of the rotor associated with the static blade assembly 2 (whether the axis X is the axis of rotation of the fan or propeller 26 for the fan guide vanes, the axis of rotation of the rotor of the compressor for the compression section guide vanes 27, or the axis of rotation of the rotor of the turbine for the turbine section nozzle 29 (the rotor is intended to be mounted on the turbine section nozzle 29)).

[0045] In the remainder of this document, the invention will be described in the context of variable pitch blades 3, i.e. the blades 3 are pivotably mounted on the hub 4 of the blade assembly 2 about a pitch axis Y. However, this is not restrictive, and when the fan is a ducted fan, the blades 3 can be fixed relative to the hub 4, which then corresponds to the shroud of the intermediate casing (the intermediate casing is located between the casing of the low-pressure compressor and the casing of the high-pressure compressor).

[0046] The static blade assembly 2 comprises a hub 4 fixedly mounted relative to a casing 30 of the turbomachine 1. The static blade assembly 2 is thus non-rotating. The blades 3 of the blade assembly 2 extend substantially radially relative to an axis X.

[0047] The blades 3 here have a variable pitch. Therefore, the blade assembly 2 comprises an actuating mechanism 5 which enables the pitch angle of the blades 3 of the blade assembly 2 to be varied in order to adapt the performance of the turbine 1 to different flight phases. In addition, each blade 3 comprises a fastener 6 (or pivot) arranged at the blade root 8. The fastener 6 is rotatably mounted relative to the hub 4 about the pitch axis Y. More precisely, the fastener 6 is rotatably mounted in a housing formed in the hub 4 by means of balls or other rolling elements.

[0048] In a manner known per se, the fastener 6 comprises a wall having an outer surface having a shape of revolution. The outer surface may for example have circular grooves suitable for forming raceways 6a for balls or other rolling elements.

[0049] The bucket 3 includes an airfoil 7 having an aerodynamic profile adapted to be arranged in an air flow to generate lift when the turbine 1 is in operation, and a bucket root 8 configured to be attached to the hub 4 of the bucket assembly 2 by fasteners 6 .

[0050] The aerodynamic profile airfoil 7 is shaped to define a pressure surface, a suction surface, a leading edge 9 and a trailing edge 10. In a manner known per se, the leading edge 9 is configured to extend facing the gas flow entering the engine 1. The leading edge 9 corresponds to a front portion with an aerodynamic profile, which faces the air flow and divides the air flow into a pressure surface flow and a suction surface flow. At the same time, the trailing edge 10 corresponds to a rear portion with an aerodynamic profile, where the pressure surface flow and the suction surface flow meet.

[0051] The blade 3 comprises two shells 12 which are connected to each other and extend integrally facing each other. In particular, the shells 12 are connected over the entire chord of the blade 3 at the blade tip, at the leading edge and at the trailing edge. The shells 12 are made of a composite material comprising a fiber reinforcement 13 densified by a matrix. The shells 12 may be integral and made from a single part of a fiber preform of varying thickness. In a variant, the fiber reinforcement 13 may comprise a first shell 12 for the pressure surface and a second shell 12 for the suction surface, the first shell and the second shell being connected, for example, near the tip of the blade 3.

[0052] The fiber reinforcement 13 may include a woven or knitted three-dimensional fiber arrangement. In addition, the fiber reinforcement 13 is manufactured so that the fiber reinforcement includes warp yarns that extend continuously inside the aerodynamic profile airfoil portion 7 and inside the blade root portion 8. In a variant, the fiber reinforcement 13 may include a laminated two-dimensional fiber arrangement. The fibers of the fiber reinforcement 13 include at least one of the following materials: carbon (usually silicon carbide), glass, aramid, polypropylene and / or ceramic (usually oxide ceramic). The matrix typically includes an organic matrix (thermosetting, thermoplastic or elastomer) or a carbon matrix. For example, the matrix includes a plastic material, which is typically made of a polymer (e.g., epoxy resin, bismaleimide or polyimide).

[0053] The shells 12 of the fiber reinforcement 13 are separated by cavities 14 opening onto the lower surface 15 of the blade root 8, which makes it possible to further reduce the mass of the blade 3 compared to conventional blades 3. Note that when the blade root 8 is assembled with the fastener 6, the lower surface 15 of the blade root 8 corresponds to the platform 16 of the blade root 8 facing the fastener 6 (at Figure 1 and Figure 3 The cavity 14 is not through (open) at the blade tip.

[0054] When the shell 12 is obtained by three-dimensional weaving and the shell 12 is monolithic, the cavity 14 is obtained by forming a non-interconnected portion in the fiber blank between two consecutive warp yarn layers, from the so-called non-interconnected (non déliée) zone (here including the blade tip 3) up to the radially inner end of the shell 12 to which the cavity 14 opens. To this end, at the non-interconnected portion, the warp yarn strands of two consecutive layers of the fiber blank are not connected by the weft yarn strands forming the cavity 14. Preferably, the non-interconnected portion extends inside the aerodynamic profile airfoil 7 and extends up to the lower surface 15 of the blade root 8 (so that the rib 17 of the fastener 6 can be inserted). In the portion of the blank intended to extend in the air flow (i.e. the aerodynamic profile airfoil 7), the cavity 14 does not open onto the leading edge 9 or the trailing edge 10. Therefore, the portion of the fiber blank forming the leading edge 9 and the trailing edge 10 is non-interconnected. On the other hand, in the portion of the blank forming the blade root 8 (i.e. the zone intended to be attached to the fastener 6), the cavity 14 may also open onto the upstream edge 19 and the downstream edge 20, respectively, of the blade root 8 (the upstream edge 19 and the downstream edge 20 of the blade root 8 extending in the extension of the leading edge 9 and the trailing edge 10 of the airfoil 7). Thus, the portions of the fiber blank forming the upstream edge 19 and the downstream edge 20 of the blade root 8 are non-interconnected.

[0055] As an example, one may refer to document EP2588758 in the name of the applicant for more details on forming the non-interconnected parts.

[0056] The blade 3 may also include one or more filling parts 25 (generally parts made of foam or any other suitable material having a density lower than that of the composite material of the shell 12), arranged in the part of the cavity 14 extending inside the aerodynamic profile airfoil 7, in order to stiffen the shell 12 and / or give it the final shape of the airfoil 7. The filling parts 25 have, for example, a mass of about 100 kg / m 3 The filling member 25 may comprise, in particular, a foam, for example a foam of organic origin (polymethacrylimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyetherimide (PEI), polyethylene, carbon, polyisocyanurate, polyurethane, etc.) or a metal foam (in particular made of an aluminum alloy), or a foam made of Kevlar, glass fiber or aluminum. Type honeycomb (comprising aramid fibers calendered into sheets and covered with phenolic resin).

[0057] The fastener 6 is configured to receive the blade root 8 and attach the blade root 8 to the hub 4 of the static blade assembly 2. To this end, the fastener 6 also includes a platform 16 and a rib 17 protruding from the platform 16. The rib 17 is configured to enter the cavity 14 to extend between the inner surface 12a of the first shell 12 and the inner surface 12a of the second shell 12. In addition, the first shell 12 and the second shell 12 are mechanically attached to the rib 17 by the attachment system 18. This configuration enables the blade 3 to be reliably attached to the hub 4 with a reduced radial and lateral volume by utilizing the inner cavity 14 of the airfoil 7 (located between the two shells 12) to transfer forces from the blade assembly 2 to the fastener 6. More precisely, the attachment system 18 passes through the first shell 12, the rib 17 and the second shell 12. The portion of the fastener 6 that bears against the blade root 8 is then housed inside the blade root 8, so that this portion does not affect the radial or transverse volume of the blade assembly 2, unlike conventional fasteners that are arranged outside the blade root 8 and therefore necessarily affect the available space in the blade assembly 2. This portion thus makes it possible to reduce the inter-component space and / or use the saved volume for other functions of the engine (channels or cable passages, addition of functions to surrounding components, etc.).

[0058] The rib 17 is housed in the cavity 14 of the blade root 8, and the height of the rib 17 (i.e. the dimension of the rib 17 along the pitch axis Y) can be greater than that of conventional fasteners, which improves the absorption of the moments generated by aerodynamic forces. Since the rib 17 can have a significant height, the rib 17 has a larger bearing surface, which reduces the bearing stresses (out-of-plane direction).

[0059] The rib 17 extends along the chord of the blade 3 between an upstream edge 19 and a downstream edge 20 of the blade root 8, the upstream edge 19 and the downstream edge 20 of the blade root 8 extending in the extension of the leading edge 9 and the trailing edge 10 of the airfoil 7, respectively. The shape of the rib 17 substantially follows the shape of the blade root 8. For example, the blade root 8 and the rib 17 may be substantially rectilinear. In the form of an embodiment and as described above, the cavity 14 may also open onto the upstream edge 19 and the downstream edge 20 of the blade root 8. The rib 17 then extends along the entire cavity 13 from the upstream edge 19 of the blade root 8 to the downstream edge 20, the shell 12 being arranged over the entire length of the shell (in the axial direction, as shown in FIG. 1 ). Figure 1 and Figure 2 shown) is attached to rib 17.

[0060] The rib 17 includes two side surfaces 21 and a top end 22. The side surface 21 is connected to the platform 16 at the lower boundary, and the radius of curvature of the side surface 21 is large enough to limit the concentration of stress. Figure 1 In the form of embodiment shown, the side surfaces 21 are inclined and converge in the direction of the tip 22, so that the thickness of the rib 17 near the platform 16 is greater than the thickness of the rib 17 near its tip 22. This configuration of the rib 17 thus makes it possible to adapt to the aerodynamic profile of the blade 3 and facilitates the installation of the blade root 8. In a variant (see Figure 3 ), the side surface 21 is substantially parallel to the pitch axis Y, and the side surface 21 extends generally parallel to the pitch axis Y. Then, the thickness of the rib 17 is substantially constant in the direction from the platform to the top end. In the form of an embodiment, the side surface 21 is flat. In a variant, the side surface 21 can be curved and symmetrical with respect to a plane passing through the axis Y, and the curvature of the side surface 21 is concave, so that the thickness of the rib 17 decreases in the direction of the top end 22. Then, the radius of curvature of the side surface 21 can be between 15 mm and 25 mm. According to another variant, the side surface 21 can have a flat first part (for example parallel to the axis Y or inclined in the direction of the top end 22), and then bends all the way to the top end with a radius of curvature of about 20 mm.

[0061] In order to facilitate the mounting of the shell 12 on the fastener 6 and avoid any risk of obstruction, the inner surface 12a of the shell 12 is more flared than the lateral surface 21 of the rib 17 (see Figure 1 More precisely, the inner surface 12a of the shell 12 forms a first angle with the plane of symmetry of the blade root 8 (perpendicular to the plane of the figure including the pitch axis Y), and the side surface 21 forms a second angle with this plane; the first angle is then greater than the second angle (see Figure 1 ).

[0062] Preferably, the radially inner end of the shell 12 bears against the platform 16. Figure 1In the example shown, the radially inner end of the shell 12 corresponds to the lower surface 15 of the blade root 8. Figure 3 In the example shown, the shell 12 is pushed down onto the rib 17 so that the inner surface 12a of the shell 12 is in contact with the side surface of the rib 17 and the platform 16. The radially inner end of the shell 12 is then the inner surface 12a of the shell 12. Therefore, whatever the variant embodiment, the platform 16 and the radially inner end (15 / 12a) of the shell 12 serve as reference surfaces for radial positioning of the blade 3 relative to the fastener 6.

[0063] At the same time, since the attachment system 18 presses the shell 12 of the blade 3 flat against the lateral surface 21 of the rib 17, the tangential positioning of the blade 3 is provided by the contact of the inner surface 12a of the shell 12 with the rib 17. Thus, the lateral surface 21 of the rib 17 and the inner surface 12a of the shell 12 form reference surfaces for the tangential positioning of the blade root 8 relative to the fastener 6.

[0064] Alternatively, the reference surface of the blade root 8 is formed by machining a sacrificial thickness of composite material. The sacrificial thickness corresponds to the non-structural part of the blade 3, which can be obtained, for example, by adding a composite material layer pre-impregnated and co-injected with a preform of the fiber reinforcement 13. The composite material layer can notably comprise glass fibers embedded in a matrix, preferably a matrix compatible with the matrix of the fiber reinforcement 13 of the shell 12 (generally the same matrix).

[0065] The attachment system 18 may include any suitable means for mechanically attaching the blade root 8 to the fastener 6. For example, the attachment system 18 includes a bolt 31 passing through the first shell 12, the rib 17 and the second shell 12. In the form of an embodiment, the attachment system 18 includes a plurality of bolts 31 distributed between the upstream end and the downstream end of the rib 17. The screws of the bolts 31 are then inserted into through passages formed in the shell 12 and the rib 17. Thus, the same bolt 31 passes through both shells 12 and the rib 17.

[0066] When the rib 17 extends over the entire chord of the blade 3, the attachment system 18 comprises bolts 31 equidistantly distributed from the upstream edge 18 of the blade root 8 all the way to the downstream edge 20. For example, for the blade 3 of a guide vane of a USF type turboprop aircraft, the attachment system 18 comprises three to six bolts 31 equidistantly distributed between the leading edge 9 and the trailing edge 10 of the blade 3. Optionally, countersinking can be done on the outer surface of the shell 12 to improve the bearing surface of the screw heads of the bolts 31.

[0067] In a variant or in addition, the attachment system 18 may include a metal plate 23 (see Figure 3), a metal plate 23 is added to each shell of the fiber reinforcement 13 and is attached to each shell of the fiber reinforcement 13 by bolting. Optionally, countersinking can be done in the plate-like element 23 to improve the bearing surface of the screw head of the bolt 31. The plate 23 can be substantially flat and pressed flat against the corresponding shell 12 by the bolt 31. In a variant embodiment where the inner surface 12a of the shell 12 is also in contact with the platform 16 (see, for example Figure 3 ) in which the plate 23 can be curved and comprises a first portion configured to press the shell 12 facing the fiber reinforcement 13 flat against the corresponding side surface 21 of the rib 17, and a second portion configured to press the free end of the same shell 12 flat against the platform 16.

[0068] In particular, the plate 23 (straight or curved) makes it possible to contribute to the absorption of moments, in particular in the event of an object ingestion, and to dissipate energy by plastic deformation in the event of a significant bending of the blade 3 .

[0069] In the form of an embodiment, the blade 3 also comprises a shaped part 24 arranged in the cavity 14 close to the tip 22 of the rib 17 to reinforce the rigidity of the blade 3 at the bottom of the airfoil 7. The shaped part 24 also has the purpose of ensuring a gradual transition of the rigidity in the radial direction to avoid stress concentrations at the exit of the clamping area.

[0070] The shaped part 24 is positioned in the cavity 14 to extend close to the rib 17, while a functional gap is formed between the shaped part 24 and the rib 17 to provide for the mounting of the blade root 8. The gap may be, for example, of the order of a few millimeters.

[0071] Where applicable, a shaping member 24 is arranged between the top end 22 of the rib 17 and one or more filling members 25 .

[0072] The shaped part 24 may in particular be made of a composite material comprising a fiber reinforcement embedded in a matrix, preferably a matrix compatible with the matrix of the fiber reinforcement 13 of the shell 12 (generally the same matrix). The fiber reinforcement of the shaped part 24 may in particular comprise fibers having a Young's modulus greater than 5 GPa, such as carbon fibers, aramid fibers, glass fibers or basalt fibers.

[0073] Manufacturing method

[0074] The blade 3 according to the invention can be obtained in particular according to the following steps.

[0075] The fiber blank of the two shells 12 is produced, for example, by weaving or knitting. In the exemplary embodiment, the fiber blank is woven in a three-dimensional manner by producing one or more non-interconnected portions to obtain the two shells 2, 12 and the cavity 4. The two shells 12 are integral at the tip, at the leading edge 9 and at the trailing edge 10 of the airfoil 7. The cavity 14 opens onto the inner surface 15 of the blade root 8 and extends all the way inside the airfoil 7.

[0076] In a variant, the shells 12 can be woven individually in two or three dimensions, and then the shells 12 are connected during curing (co-curing).

[0077] Where applicable, the cavity 14 also opens onto the upstream edge 19 and the downstream edge 20 of the blade root 8 .

[0078] At least one filling component 25 is then arranged at the bottom of the cavity 14. At least one forming component 24 is then arranged in the cavity 14, for example bearing against one or more filling components 25. The forming component 24 seals the cavity 14 and is positioned so as to leave a gap with the rib 17 after assembly.

[0079] Optionally, the pre-impregnated composite material layer is arranged against a surface of the shell which serves to form a reference surface (i.e. the inner surface 12a of the shell 12) on the radially inner end of the shell 12 in the area intended to come into contact with the side surface 21 of the rib 17.

[0080] The assembly formed by the fiber blank, the filling part 25 and the forming part 24 and, where applicable, the composite material layer is placed in a mold with a recess having the shape of the molded final part (i.e., the root of the airfoil 7 and the blade 3), and a material, usually plastic (the "matrix" of the composite material), is injected into the mold to impregnate the fiber reinforcement 13 of the shell 12 and the forming part and the filling part. The injection of the matrix can be done by RTM or VARRTM type injection techniques. In the case of plastics, the injected matrix is, for example, a thermosetting liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer (e.g., a resin), which is diluted in a solvent where applicable. In a manner known per se, the plastic is then heated to polymerize the plastic, for example, by crosslinking. To this end, the mold is placed in an oven.

[0081] The part obtained is then removed from the mould and then optionally trimmed by machining to remove excess length and obtain a part of the desired shape, despite any shrinkage of the fibres of the fibre reinforcement 13 during the polymerisation of the plastic. In particular, the sacrificial thickness is machined to obtain a reference surface for the blade root 8. Furthermore, a through passage is machined in the shell 12 to accommodate the attachment system. Where applicable, a countersink is also machined around the through passage.

[0082] The fastener 6 is then positioned on the blade root 8 by arranging the rib 17 in the cavity 14 between the inner surfaces 12a of the shells 12. After the fastener 6 is inserted, the tip 22 of the rib 17 preferably extends away from the shaped part 24 by a short distance.

[0083] Preferably, before the rib 17 is inserted into the cavity 14 , a through-passage is formed through the lateral surface 21 of the rib 17 , which through-passage is intended to receive the attachment system 18 and extends facing the through-passage machined in the shell 12 .

[0084] Finally, the attachment system 18 is added and attached to the shell 12 and the fastener 6 to secure the blade root 8 and the rib 17. For example, bolts 31 are inserted into the through passages of the shell 12 and the through passages of the fastener 6 and attached.

[0085] The manufacturing method is therefore simpler than that of a blade with conventional fasteners, the number of parts required to manufacture the blade 3 is reduced, and the steps of weaving or knitting the fiber preform are simplified.

Claims

1. A blade (3) of a static blade assembly (2) of a turbine (1), the blade comprising: - a blade root (8) comprising a fiber reinforcement (13) embedded in a matrix, the fiber reinforcement (13) comprising a first shell (12) and a second shell (12), the first shell and the second shell being separated by a cavity (14) opening onto a lower surface (15) of the blade root (8); a fastener (6) configured to receive the blade root (8) and attach the blade root to the hub (4) of the blade assembly (2), the fastener (6) comprising a platform (16) and a rib (17) protruding from the platform (16), the rib (17) being configured to enter the cavity (14) to extend between an inner surface (12a) of the first shell (12) and an inner surface of the second shell (12); as well as - an attachment system (18) configured to mechanically attach the first shell (12) and the second shell (12) to the rib (17) of the fastener (6), The blade (3) is characterized in that the attachment system passes through the first shell (12), the rib (17) and the second shell (12).

2. The impeller (3) according to claim 1, wherein: The rib (17) includes two side surfaces (21) connected to the platform (16) and a top end (22) connecting the two side surfaces (21), and the thickness of the rib (17) decreases from the platform (16) toward the top end (22).

3. The impeller (3) according to claim 1, wherein: The inner surface (12a) of the shell (12) is more outwardly flared than the side surface (21) of the rib (17).

4. The impeller (3) according to claim 1, wherein: The rib (17) includes two side surfaces (21) connected to the platform (16) and a top end (22) connecting the two side surfaces (21), and the thickness of the rib (17) is substantially constant in a direction from the platform (16) to the top end (22).

5. The blade (3) according to any one of claims 1 to 4, wherein: The first shell layer and the second shell layer (12) also abut against the platform (16).

6. The blade (3) according to any one of claims 1 to 5, wherein: The attachment system (18) comprises at least one of the following elements: a bolt (31); a plate (23) shaped to contact the outer surface of the shell (12).

7. The impeller (3) according to claim 6, wherein: The attachment system (18) comprises a bolt (31) passing through the first shell (12), the rib (17) and the second shell (12).

8. The blade (3) according to any one of claims 1 to 7, further comprising a shaped part (24) housed in the cavity (14) remote from the top end (22) of the rib (17).

9. The impeller (3) according to claim 8, wherein: The shaped part (24) comprises an additional composite material comprising an additional fiber reinforcement embedded in an additional matrix, the additional fiber reinforcement (13) comprising fibers having a Young's modulus at least equal to 5 GPa, such as carbon fibers, aramid fibers, glass fibers or basalt fibers.

10. The blade (3) according to claim 8 or 9, further comprising a filling part (25) housed in the cavity (14), between the tip (22) of the blade (3) and the shaped part (24), the filling part (25) being able to contain a material having a density less than that of the composite material.

11. The blade (3) according to any one of claims 1 to 10, wherein: The fiber reinforcement (13) has an upstream edge (19) and a downstream edge (20), the cavity (14) also opening onto at least one of the upstream edge (19) and the downstream edge (20).

12. The blade (3) according to any one of claims 1 to 11, wherein: The fastener (6) is a pivoting member.

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