ROTOR OR STATOR BLADE FOR AN AIRCRAFT TURBOMACHINE

Abstract

Rotor (14) or stator (18) blade for an aircraft turbomachine (10), this blade (14, 18) comprising: - a blade (20) comprising a lower surface (20a) and an upper surface (20b), as well as a leading edge (20c) and a trailing edge (20d), the leading or trailing edge (20c, 20d) of the blade (20) comprising serrations (22) formed by alternating teeth (22a) and hollows (22b) along this edge, characterized in that at least one of said teeth (22a1) is attached and fixed to a body (24) of the blade (20), which defines the lower surface (20a) and the upper surface (20b) of the blade, and the other teeth (22a2) are formed by continuity of material of the body (24) of the blade (20). Figure for abstract: Figure 3

Description

Title of the invention: ROTOR OR STATOR BLADE FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a rotor or stator blade for an aircraft turbomachine. Technical approval plan

[0002] The state of the art includes in particular document FR-A1-3 073 017.

[0003] An aircraft turbomachine conventionally comprises a gas generator which drives at least one propeller. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the rotor of the propeller for its rotational drive.

[0004] A propeller can be shrouded. This is the case for a fan in a turbomachine of the turbojet or turbofan type, for example.

[0005] A propeller can be unducted. This is the case for a turboprop, for example.

[0006] A propeller comprises a hub and an annular row of blades which are mounted all around the hub. The propeller blades can be fixed and therefore have a fixed angular position around their respective axes of elongation.

[0007] On the contrary, the blades of the propeller can be variable pitch, that is to say they are capable of being moved in rotation around axes called pitch axes, which generally extend along the axes of elongation of the blades. The pitch axes can be radial axes relative to the axis of rotation of the propeller.

[0008] A rotor blade 14 or stator blade 18 as shown in Figures 2 and 3 conventionally comprises a blade 20 having a lower surface 20a and an upper surface 20b, as well as a leading edge 20c and a trailing edge 20d. In the case of a variable-pitch rotor or stator blade, it further comprises a platform 21 connected to one end of the blade and defining the blade pitch axis A. The platform 21 is generally mounted in an orifice of the hub and centered and guided in rotation in this orifice around the pitch axis A.

[0009] It is known to produce a rotor or stator blade from a metallic, ceramic or composite material. A well-known composite material for a blade comprises a preform based on woven carbon fibers which is embedded in a polymer matrix based on epoxy, for example. The leading edge of the blade can be reinforced by a bonded metal shield.

[0010] The evolution of the performance of turbomachines tends towards the increase of their bypass ratio, which is mainly achieved by increasing the diameter of the propellers and therefore the length and mass of their blades.

[0011] In addition, a so-called slow, high-bypass propeller comprises a reduced number of blades whose chord is increased to improve the propulsive efficiency of the turbomachine.

[0012] In the case of a shrouded propeller, the nacelle surrounding the propeller includes an internal acoustic treatment which makes it possible to reduce noise emissions outside the turbomachine.

[0013] In the case of an unducted propeller, other solutions must be found for reducing propulsive noise. This is particularly the case for the turbomachine 10 illustrated in [Fig.l]. This turbomachine 10 comprises a propeller 12 upstream, which comprises rotor blades 14, for example with variable pitch, and a rectifier 16 downstream, which comprises stator blades 18 also with variable pitch.

[0014] To remedy the problem of noise emission, a noise reduction technology already known on fans and inspired in particular by the wings of nocturnal raptors consists of arranging serrations 22 on the trailing edges 20d of the rotor blades 14 or on the leading edges 20c of the stator blades 18 (figures 2 and 3).

[0015] Serrations 22 of a leading edge 20c or trailing edge 20d are formed by alternating teeth 22a and hollows 22b along this edge. The serrations 22 can cause variations in the chord of the blade as a function of the radial height, with variable thicknesses and a very thin trailing edge 20d or leading edge 20c.

[0016] The teeth 22a are defined so as to reduce noise in the average emission spectrum without unduly worsening other frequencies at other engine speeds.

[0017] When the blade 14, 18 is made of metal or ceramic, the serration teeth 22a are formed of metal and are formed by continuity of material of the body of the blade, that is to say that the teeth 22a are integral with the body of the blade which defines the intrados 20a and the extrados 20b of the blade 20.

[0018] When the blade 14, 18 is made of composite from a preform, the serration teeth 22a are also formed by continuity of material of the body of the blade, and in particular by continuity of the preform of the body of the blade.

[0019] During operation, deterioration or wear of the clamping teeth may occur and the question then arises of replacing the blade with a new one.

[0020] The present invention provides a simple, effective and economical solution to this problem. Summary of the invention

[0021] The invention provides a rotor or stator blade for an aircraft turbomachine, this dawn comprising:

[0022] - a blade comprising a lower surface and an upper surface, as well as a leading edge and a trailing edge, the leading or trailing edge of the blade having serrations formed by alternating teeth and hollows along this edge,

[0023] characterized in that at least one of said teeth is attached and fixed to a body of the blade, which defines the intrados and the extrados of the blade, and the other teeth are formed by continuity of material of the body of the blade.

[0024] The invention proposes not to replace the blade in its entirety in the event of wear or deterioration of one of its teeth, but rather to replace only the or each tooth to be replaced with a new one. The or each replaced tooth is then added and fixed to the body of the blade. The blade thus comprises original teeth, which are formed by continuity of material of the body of the blade, and one or more teeth added to the body.

[0025] The blade according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another: • the tooth or teeth added is fixed by gluing to the body. • the or each added tooth is fixed by at least one screw on the body. • the screw passes through a hole in the tooth and is screwed into a tapped hole in the body • the screw includes a head which is housed entirely in a recess in the tooth.

[0026] — the recess is completely filled with a filling material which covers the head of the screw. • the orifice or recess opens onto an edge of the added tooth, this edge being located between two faces of the tooth which extend respectively in the extension of the intrados and the extrados of the blade. • the or each added tooth is fitted onto the body using a mortise and tenon system. • the screw is located between at least two tenons or two mortises, or next to at least one tenon or at least one mortise. • the or each added tooth comprises several flat faces bearing on complementary flat faces of the body. • the tenons and mortises include some of said flat faces.

[0027] — the body is metallic or ceramic, and the or each attached tooth is metallic or ceramic. • the body is composite and made from a fibrous preform embedded in a polymer matrix, this fibrous preform extending into said other teeth, and the or each added tooth is metallic or ceramic or is made from another fibrous preform embedded in a polymer matrix.

[0028] The invention further relates to a turbomachine for an aircraft, comprising a rotor or a stator formed by several blades as described above.

[0029] The invention also relates to a method for repairing a rotor or stator blade for an aircraft turbomachine, so as to obtain a blade as described above. The blade to be repaired comprises a blade having a lower surface and an upper surface, as well as a leading edge and a trailing edge, the leading or trailing edge of the blade having serrations formed by alternating teeth and hollows along this edge, the teeth being formed by continuity of material of a body of the blade. The method comprises the following steps:

[0030] a) removing at least one of the teeth to be replaced,

[0031] b) report and fix a new tooth in place of the or each tooth removed on the body of the blade.

[0032] The or each tooth that can be attached is fixed by gluing and / or by at least one screw on the body.

[0033] Alternatively, the or each tooth is added and is formed by mounting a fiber preform on the body, and injecting a polymer resin into this preform inside an injection-molding mold.

[0034] The removal in step a) can be carried out by machining, or unscrewing in the case where the tooth to be replaced has previously been added and fixed to the blade. Brief description of the figures

[0035] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0036] [Fig.l] [Fig.l] is a schematic perspective view of a turbomachine with an unducted propeller and an unducted rectifier, the propeller and the rectifier comprising variable-pitch blades;

[0037] [Fig.2] [Fig.2] is a schematic view of a variable pitch rotor or propeller blade;

[0038] [Fig.3] [Fig.3] is a schematic view of a variable-pitch stator or rectifier blade;

[0039] [Fig.4] [Fig.4] is a schematic view of a blade according to the invention;

[0040] [Fig.5] [Fig.5] is a schematic perspective view of a blade according to a mode of carrying out the invention;

[0041] [Fig.6] [Fig.6] is a schematic perspective view of a replacement tooth for the blade of [Fig.5];

[0042] [Fig.7] [Fig.7] is a schematic perspective view of a body of the dawn of the [Fig.5] ;

[0043] [Fig.8] [Fig.8] is a schematic sectional view of a blade according to an alternative embodiment of the invention;

[0044] [Fig.9] [Fig.9] is a schematic sectional view of a replacement tooth for the dawn of [Fig.8]; and

[0045] [Fig. 10] [Fig. 10] is a schematic sectional view of a body of the blade of [Fig.8]. Detailed description of the invention

[0046] Figures 1 to 3 have been described in the above.

[0047] The invention relates to a rotor 14 or stator 18 blade for an aircraft turbomachine, which may be the turbomachine of [Fig.l] or another turbomachine.

[0048] [Fig. 4] illustrates a blade according to the invention, which is here a rotor blade 14 but which could also be a stator blade 18 insofar as the invention applies to both types of blade.

[0049] The blade 14 or 18 comprises a blade 20 having a lower surface 20a and an upper surface 20b, as well as a leading edge 20c and a trailing edge 20d.

[0050] The trailing edge 20d of the blade 20 comprises serrations 22 formed by an alternation of teeth 22a and hollows 22b along this trailing edge.

[0051] In the case of a stator blade 18, it is its leading edge 20c which comprises serrations 22 as mentioned above.

[0052] The particularity of the blade 14, 18 is that at least one of its teeth 22al is attached and fixed to the body 24 of the blade 20 while the other teeth 22a2 are formed by continuity of material of the body 24 of the blade 20.

[0053] This is due to the fact that the teeth 22a2 are original teeth of the blade which were produced at the same time as the body 24 of the blade 20, whereas the tooth 22al is a replacement tooth or a new tooth which was added and fixed on the body 24 to replace a tooth which was worn or damaged.

[0054] In the example of [Fig.4], we can clearly see that the tooth 22al comprises a base 26 and a projection 28 and that it is fixed on the body 24 by means of its base 26. It can also be seen more particularly in the following [Fig.5] that the tooth 22al comprises an edge 30 or field which is located between two faces 32, 34 of the tooth 22al which extend respectively in the extension of the intrados 20a and the extrados 20b of the blade 20.

[0055] The edge 30 has a convex curved shape and in turn extends in the extension of the leading edge 20c or trailing edge 20d of the blade which includes the serrations 22.

[0056] Figures 5 to 7 illustrate a first embodiment of the invention in which the tooth 22a 1 is attached and fixed by gluing to the body 24 of the blade 20.

[0057] In the example shown, the tooth 22al is further fixed by at least one screw 36 on the body 20.

[0058] The screw 36 can pass through an orifice 38 of the tooth 22al and be screwed into a tapped hole 40 of the body 24.

[0059] The screw 36 may comprise a head 42 which conventionally comprises an imprint 44 intended to cooperate with a tool for driving the screw 36 in rotation and therefore for screwing it in.

[0060] Preferably, the head 42 of the screw 36 is housed entirely in a recess 46 of the tooth 22al, as in the example illustrated.

[0061] The recess 46 is then completely filled with a filling material which covers the head 42 of the screw 36. This makes it possible to prevent the accumulation of impurities or water in the recess, this water being liable to freeze and form ice in flight.

[0062] In the example shown, the orifice 38 or the recess 46 opens onto the edge 30 of the tooth 22al and therefore makes it possible not to alter the faces 32, 34 of the tooth 30 which extend in the extension of the intrados 20a and the extrados 20b. The filling of the recess 46 however makes it possible to ensure aerodynamic continuity of this edge 30 and therefore not to alter the air flow at the level of this edge 30 because of the recess 46.

[0063] Advantageously, as in the example shown, the tooth 22al is fitted onto the body 24 by a system 48 of the tenon-mortise type.

[0064] The number of tenons and the number of mortises is not limiting. There may be a single tenon-mortise set or several tenon-mortise sets.

[0065] For example, the screw 36 may be located between two tenons 50 of the tooth 22al as illustrated in [Fig.6], and extend in the middle of a mortise 52 of the body 24 as illustrated in [Fig.7]. In other words, two tenons 50 may cooperate with the same mortise 52 of larger dimension than the tenons 50.

[0066] Alternatively, the screw could be located between more than two tenons of the tooth, or could pass through a tenon of the tooth, or could be located adjacent to a tenon (or mortise) or more tenons (or mortises) of the tooth.

[0067] The tooth 22al preferably comprises several flat faces 54, 56, 58 bearing on complementary flat faces 60, 62, 64 of the body 24. The tenons 50 and mortises 52 comprise, for example, flat faces 54, 60 which cooperate with each other. The base 26 of the tooth 22al may further comprise flat faces 56, 58 which cooperate with flat faces 62, 64 of the body 20. The flat faces 56, 58 of the base 26 of the tooth 22al extend between the aforementioned faces 32, 34 of the tooth 22al, and on the side opposite the edge 30 of the tooth. The faces 56 and 62 cooperate with each other and are substantially per pendicular to the axis of the screw 36. The faces 58, 64 cooperate with each other and are inclined relative to the faces 56, 62. In the example shown, the face 56 (respectively the face 62) is located between a pair of faces 58 (respectively faces 64). The faces 60 and 64 form a sort of bowl and the faces 56, 58 have a shape complementary to this bowl. The cooperation of the faces 56, 58, 62, 64 of the tooth 22al and the body 24 makes it possible to ensure precise positioning of the tooth 22al on the body 24, or even a foolproofing during assembly.

[0068] The body 24 of the blade 14, 18 may be metallic or ceramic. In this case, the tooth 22a 1 may be made of the same material as the blade 14, 18 and therefore metallic or ceramic.

[0069] Alternatively, the blade 14, 18 may be made of composite material and be made from a fiber preform embedded in a polymer matrix. This fiber preform extends into the teeth 22a2 which are formed simultaneously with the body 24 as mentioned above. The new tooth 22al may be metallic or ceramic, or may be made from another fiber preform embedded in a polymer matrix.

[0070] The invention also relates to a method of repairing a blade 14, 18 so as to obtain a blade as described above and illustrated in [Fig.4].

[0071] The blade 14, 18 to be repaired comprises a blade 20 whose teeth 22a are formed by continuity of material of the body 24 of the blade 20.

[0072] The method comprises the following steps:

[0073] a) removing at least one of the teeth 22a to be replaced,

[0074] b) report and fix a new tooth 22a 1 in place of the or each tooth removed on the body 24 of the blade 20.

[0075] Concerning step a), the tooth to be removed may be a tooth already added and fixed on the blade, in accordance with the invention for example, or a tooth which is in one piece with the rest of the blade. In the first case, the screw can be unscrewed to remove the tooth. If the screw is not accessible or if the tooth is in one piece, then the tooth can be machined for example (by a milling tool or water jet cutting tool for example).

[0076] In the case mentioned above in relation to figures 5 to 7, the or each tooth 22a 1 added is fixed by gluing and / or by at least one screw 36 on the body 24. The glue can be introduced into the mortise(s) 52, in sufficient quantity so that when the tenon(s) 50 are inserted into the mortise 52, the glue overflows and covers all of the bearing faces between the tooth 22a1 and the body 24. The excess glue is then removed and can be sanded after drying to ensure aerodynamic continuity between the faces 32, 34 and the intrados 20a and the extrados 20b of the blade 20.

[0077] In the other case mentioned, the new tooth 22al is made from another fibrous preform embedded in a polymer matrix.

[0078] This variant is illustrated in Figures 8 to 10. The attached tooth 22al is formed by mounting a fiber preform 70 on the body 24 (Figures 9 and 10), and injecting a polymer resin into this preform 70 inside an injection-molding mold 72 ([Fig.8]).

[0079] The preform 70 of the tooth 22al can be mounted on the body 24 of the blade 20 by a tenon-mortise system 74 similar to that described above. In the example shown, this system 74 has a dovetail shape. This assembly makes it possible to anchor the tooth 22a 1 in the body 24 of the blade 20.

[0080] The resin injected into the preform 70 makes it possible to solidify the tooth 22al but also to secure it to the body 24 of the blade 20.

[0081] Although the invention has been described in the case of the replacement of a single tooth 22a 1 of a blade 20, it is understood that the blade 20 could comprise two or more teeth 22al added and fixed to the body 24 of the blade 20.

[0082] Furthermore, although the invention has been described in the context of serration teeth on the trailing edge of a blade, it also applies to serration teeth on the leading edge of a blade.

Claims

Claims

1. Rotor (14) or stator (18) blade for an aircraft turbomachine (10), this blade (14, 18) comprising: - a blade (20) comprising a lower surface (20a) and an upper surface (20b), as well as a leading edge (20c) and a trailing edge (20d), the leading or trailing edge (20c, 20d) of the blade (20) comprising serrations (22) formed by an alternation of teeth (22a) and hollows (22b) along this edge, characterized in that at least one of said teeth (22al) is attached and fixed to a body (24) of the blade (20), which defines the lower surface (20a) and the upper surface (20b) of the blade, and the other teeth (22a2) are formed by continuity of material of the body (24) of the blade (20).

2. Blade (14, 18) according to claim 1, in which the or each added tooth (22al) is fixed by gluing to the body (24).

3. Blade (14, 18) according to claim 1 or 2, in which the or each attached tooth (22al) is fixed by at least one screw (36) on the body (24).

4. A blade (14, 18) according to claim 3, wherein the screw (36) passes through an orifice (38) of the tooth (22al) and is screwed into a tapped hole (40) of the body (24).

5. A blade (14, 18) according to claim 3 or 4, wherein the screw (36) comprises a head (42) which is housed entirely in a recess (46) of the tooth (14, 18).

6. Blade (14, 18) according to claim 4 or 5, in which the orifice (38) or the recess (46) opens onto an edge (14, 18) of the attached tooth (22al), this edge (14, 18) being located between two faces (32, 34) of the tooth (22a 1) which extend respectively in the extension of the intrados (20c) and the extrados (20d) of the blade (20).

7. Blade (14, 18) according to one of claims 4 to 6, in which the or each added tooth (20al) is fitted onto the body (20) by a mortise-and-tenon type system (48).

8. A blade (14, 18) according to claim 7, dependent on one of claims 3 to 6, wherein the screw (36) is located between at least two tenons (50) or two mortises (52), or next to at least one tenon or at least one mortise.

9. Blade (14, 18) according to one of the preceding claims, in which the or each tooth (22al) added comprises several faces (54, 56, 58) support planes on complementary plane faces (60, 62, 64) of the body (24).

10. A blade (14, 18) according to claim 9, dependent on claim 8, wherein the tenons (52) and mortises (54) comprise some of said planar faces (54, 60).

11. Blade (14, 18) according to one of claims 1 to 10, in which the body (24) is composite and made from a fibrous preform embedded in a polymer matrix, this fibrous preform extending into said other teeth (22a2), and the or each tooth (22a1) added is metallic or ceramic or is made from another fibrous preform (70) embedded in a polymer matrix.

12. Turbomachine (10) for an aircraft, comprising a rotor or a stator formed by several blades (14, 18) according to one of the preceding claims.

13. Method for repairing a rotor (14) or stator (18) blade for an aircraft turbomachine (10), so as to obtain a blade (14, 18) according to one of claims 1 to 11, the blade to be repaired comprising a blade (20) comprising a lower surface (20a) and an upper surface (20b), as well as a leading edge (20c) and a trailing edge (20d), the leading or trailing edge (20c, 20d) of the blade (20) comprising serrations (22) formed by alternating teeth (22a) and hollows (22b) along this edge, the teeth (22a) being formed by continuity of material of a body of the blade, in which it comprises the following steps: a) removing at least one of the teeth (22a) to be replaced, b) adding and fixing a new tooth (22a 1) in place of the or each tooth removed on the body (24) of the blade (20).

14. Method according to claim 13, in which the or each tooth (22a 1) added is fixed by gluing and / or by at least one screw (36) on the body (24).

15. Method according to claim 14, in which the or each tooth (22a 1) added is formed by mounting a fibrous preform (70) on the body, and injecting a polymeric resin into this preform (70) inside an injection-molding mold (72).

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