Variable-pitch blade for a turbomachine

Abstract

The invention relates to a variable-pitch blade (7, figure 1) for a turbomachine, comprising: • - a tubular metal sleeve (13); • - a fibrous structure (20, figure 1), the fibrous structure comprising a blade root (22, figure 1) comprising a tubular attachment portion (23) inserted axially into a cavity (17) in the sleeve (13); • - an insert (24) centered on the pitch axis (Y) and inserted axially into a recess (20a, figure 4c) in the attachment portion (23) such that the attachment portion (23) is radially interposed between the insert (24) and the inner wall (18) of the sleeve (13); and • - at least one tooth (50) in order to form a load path in the circumferential direction about the axis (Y) between the sleeve (13) and the insert (24).

Description

[0001] DESCRIPTION

[0002] TITLE: VARIABLE TIMING TURBINE BLADE FOR A TURBOMACHINE

[0003] Technical field of the invention

[0004] The invention relates generally to the field of turbomachinery, and in particular to turbomachine blades.

[0005] The invention relates more particularly, but not exclusively, to a variable pitch blade intended for use in an unfaired aircraft engine fan rotor.

[0006] Technical background

[0007] The technical background includes documents DE-C1-37 38 216, EP-A2-2 535 519, US-A1-2016 / 272299 and FR-A1-3 050 719.

[0008] 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 BPR), and consequently, reduced fuel consumption. Therefore, in this type of engine, the fan blades can have a large span.

[0009] 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.

[0010] However, the design of such blades requires taking into account conflicting constraints.

[0011] On the one hand, the design 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 may be exerted on these blades while limiting their acoustic signature.

[0012] Furthermore, on unshod fan designs, engine start-up is generally performed with a very open valve timing. Indeed, a very open valve timing allows power to be consumed by torque, which ensures machine safety by guaranteeing low fan speeds. However, with a very open valve timing, the blades experience turbulent, completely separated aerodynamic flow, which generates broadband vibrational excitation. In particular, on large-chord, long-span blades, the bending stress is intense, even though the engine speed is not at its maximum.

[0013] 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.

[0014] These blades can be made of metallic material. While metallic blades have good mechanical resistance, they have the disadvantage of being relatively heavy.

[0015] 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.

[0016] To overcome these drawbacks, various solutions exist in the prior art. Most utilize reinforcing elements, particularly at the blade root, and add various structural elements to allow, for example, the blade to be attached to the stabilization mechanism. Patent documents W0-A1-2022 / 018353 and W0-A1-2022 / 208002 describe the addition of reinforcing and structural elements, especially at the blade roots. However, these solutions have the disadvantage of requiring the manufacture of several elements in potentially different materials and the assembly of these elements using fastening methods. Such blades can therefore be relatively time-consuming to manufacture.

[0017] Summary of the invention

[0018] The invention proposes a variable-pitch blade for a turbomachine comprising:

[0019] - a tubular metal sleeve, this sleeve comprising a fixing part configured to be connected to a variable shimming mechanism, and a recess passing through the sleeve along a shimming axis, the recess being delimited by an internal wall of the sleeve,

[0020] - a fibrous structure, the fibrous structure comprising a blade root including a tubular attachment portion inserted axially into the recess of the sleeve, this attachment portion including a housing centered on the alignment axis, the fibrous structure further comprising an aerodynamically profiled blade connected to the blade root,

[0021] - an insert centered on the alignment axis and inserted axially into the housing of the attachment portion so that the attachment portion is radially interposed between the insert and the inner wall of the sleeve, and

[0022] - a polymerized resin for solidifying the fibrous structure and for bonding the insert to the fibrous structure and to the inner wall of the sleeve, characterized in that it further comprises at least one tooth extending radially with respect to the axis and passing successively through the insert, the attachment portion of the fibrous structure, and the sleeve, in order to form a force path in a circumferential direction around the axis between the sleeve and the insert.

[0023] The problem to be solved concerns the absorption of the torsional moment around the blade's pitch axis. Indeed, the aerodynamic and centrifugal forces acting on the blade generate a resulting torsional moment that must be absorbed at the interface between the blade root and the outer metal sleeve in order to control the blade pitch via the variable pitch mechanism.

[0024] By default, this torque is absorbed by the polymerized resin, which ensures a bond between the blade root attachment and the sleeve. This bond provides an initial path for the torque transfer. A failure of this interface would result in a loss of control over the blade pitch.

[0025] The invention thus proposes to reinforce this force path thanks to the tooth or teeth which form a secondary force path between the sleeve and the insert.

[0026] The blade according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0027] - the fibrous structure is obtained by weaving, preferably three-dimensional, fibers;

[0028] - where each tooth is brought into a housing of the insert, of the attachment portion of the fibrous structure, and of the sleeve;

[0029] - each tooth comprises a radially internal end aligned with an internal surface of the insert, and a radially external end aligned with an external surface of the sleeve;

[0030] - where each tooth has a radial dimension greater than its axial dimension; - where each tooth has a radial dimension greater than its angular extent around the axis;

[0031] - where each tooth is made of metal;

[0032] - where each tooth has an angular range around the axis which is between 5 and 20°;

[0033] - the number of teeth is between 1 and 10 and for example between 2 and 6;

[0034] - where each tooth has an elastic modulus lower than that of the sleeve and preferably less than twice that of the sleeve;

[0035] - the elastic modulus of the tooth or teeth is less than 100 GPa, or even 50 GPa.

[0036] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one blade as described above.

[0037] Brief description of the figures

[0038] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0039] [Fig.1] Figure 1 schematically represents an example of an engine including an unfaired fan;

[0040] [Fig.2] Figure 2 schematically represents a blower blade according to an embodiment of the invention assembled to a shimming mechanism;

[0041] [Fig.3] Figure 3 schematically represents a blower blade according to a first embodiment of the invention;

[0042] [Fig. 4a] Figure 4a schematically represents a sleeve according to a first embodiment of the invention in perspective view

[0043] J

[0044] [Fig.4b] Figure 4b schematically represents the sleeve of figure 4a in profile view;

[0045] [Fig.4c] Figure 4c schematically represents the sleeve of figures 4a and 4b into which the attachment portion and the insert are inserted; [Fig.4d] Figure 4d schematically represents the sleeve / attachment portion / insert assembly of figure 4c inserted into the stabilizing mechanism;

[0046] [Fig. 5] Figure 5 schematically represents an insert according to one embodiment of the invention; and

[0047] [Fig.6a-6b] Figures 6a and 6b are schematic views, respectively in axial section and in cross section, of a foot of a blade according to an embodiment of the invention.

[0048] Detailed description of the invention

[0049] In Figure 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 inlet located on the side, to the right in Figure 1).

[0050] 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.

[0051] Thus, in the example illustrated in Figure 1, 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).

[0052] Furthermore, the invention also applies to engines with different architectures, such as an architecture comprising a fan rotor with moving blades and a fan stator with fixed blades, or a single fan rotor. The invention is applicable to turboprop-type architectures (comprising a single fan rotor).

[0053] In Figure 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.

[0054] As illustrated in Figure 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 ball bearings 11 or other rolling elements.

[0055] The aerodynamic airfoil blade 12 has a first end connected to the blade root 9 and a second end, opposite the first end. The aerodynamic airfoil portion of the blade 12 is designed to extend into an engine air stream when the engine is running, in order to generate lift. Conversely, the blade root 9 is designed to extend out of the air stream.

[0056] 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 the mechanism 8, in particular inside the attachment device 10. The sleeve 13 has a recess 17 delimited by an internal wall 18 of the sleeve 13. The recess 17 passes through the sleeve 13 along a shimming axis Y.

[0057] With reference to Figures 3, 5a, and 5b, the blade 7 also includes a fibrous structure 20 obtained, for example, by three-dimensional weaving of fibers. Other methods could be used as alternatives. 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.

[0058] The fibrous structure 20 has a tubular shape and includes a housing 20a centered on the Y alignment axis.

[0059] The fibrous structure 20 also includes a blade 21 with an aerodynamic profile connected to the blade root 22.

[0060] The blade 7 also includes an insert 24 shown in Figure 5 and which is configured to be inserted into the housing 20a of the attachment portion 23 so that the attachment portion 23 is radially intercalated between the insert 24 and the inner wall 18 of the sleeve 13.

[0061] The blade 7 further includes a polymerized resin for solidifying the fibrous structure 20 and for bonding the insert 24 to the fibrous structure 20 and to the inner wall 18 of the sleeve 13.

[0062] The resin thus makes it possible to form a main force path, called default, when transmitting a torque recovery force around the Y alignment axis between the blade root 22 and the sleeve 13.

[0063] 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.

[0064] 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.

[0065] The resin typically comprises an organic material (thermosetting, thermoplastic, or elastomer) or a carbon matrix. For example, the matrix may comprise a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide. The fibers of the fibrous structure 20 comprise at least one of the following materials: carbon, glass, aramid, polypropylene, and / or ceramic.

[0066] With reference to Figures 4a, 4b, and 4c, the attachment portion 23 may have 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 24 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.

[0067] Indeed, when the fan is rotating, the blade 7 is subjected to centrifugal forces oriented in a radial direction relative to the axis of rotation of the fan, which tend to separate the aerodynamic profile blade 12 from the sleeve 13. The extra thickness 23” helps to prevent the separation of the blade 12 and the sleeve 13.

[0068] With reference to figures 3, 4a to 4d, the fixing part 14 has a rotational symmetry about the Y axis. Furthermore, the fixing part 14 has an external surface with different reliefs.

[0069] 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 the blade foot 22 is configured to bear.

[0070] 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.

[0071] The fixing part 14 also includes a first cylindrical surface 32 and a second cylindrical surface 34, each allowing one of the bearings 11 to be received. The fixing part 14 thus allows the blade foot 9 to be mounted rotatably inside the attachment device 10 provided in the hub 6.

[0072] Sleeve 13 is preferably metallic and monolithic.

[0073] As previously described, the sleeve 13 has an inner wall 18 that defines the recess 17. The recess 17 can form 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".

[0074] The recessed portion can have a different shape and can be placed in a different position along wall 18.

[0075] The wall 18 could alternatively 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.

[0076] Figure 4d represents the sleeve into which the attachment portion 23 and the insert 24 are inserted, the sleeve being arranged in the attachment device 10, the bearings 11 being arranged on the cylindrical surfaces 32 and 34.

[0077] Referring to Figure 5, 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 or pointed. 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. Alternatively, the locking end 42 may have a different shape to accommodate a stop that may also have a different shape. The insert 24 is preferably metallic.

[0078] Figures 6a-6b represent one embodiment of the blade according to the invention.

[0079] The particularity of the blade according to the invention is related to the fact that the blade further comprises at least one tooth 50 which extends radially with respect to the Y axis and which successively passes through the insert 24, the attachment portion 23 of the fibrous structure 20, and the sleeve 13, in order to form a force path in a circumferential direction around the Y axis between the sleeve 13 and the insert 24.

[0080] Each tooth 50 is preferably brought into a housing 52 of the insert 24, of the attachment portion 23 of the fibrous structure 20, and of the sleeve 18.

[0081] In practice, to produce the blade according to the invention, it may be sufficient to machine the housing 54 and to mount the tooth or each tooth 54 therein. The machining then takes place after solidification of the fibrous structure 20 by the resin.

[0082] Each tooth 50 may include a radially internal end 50a aligned with an internal surface 24a of the insert 24, and a radially external end 50b aligned with an external surface of the sleeve 13, such as the aforementioned surface 34.

[0083] Each tooth 50 can have a radial dimension R1 greater than its axial dimension L1, as is the case in the example shown.

[0084] The or each tooth 50 may have a radial dimension R1 greater than its angular extent oc around the Y axis, as is also the case in the example shown.

[0085] The tooth or each tooth 50 is preferably made of metal.

[0086] Each tooth 50 preferably has an angular range oc around the axis which is between 5 and 20°. The number of teeth 50 can be between 1 and 10 and for example between 2 and 6. When their number is greater than 2, the teeth are preferably regularly distributed around the Y axis.

[0087] The metallic material of the insert 24 and the sleeve 13 generally has an elastic modulus greater than 100 GPa (gigapascals) and high hardness, whereas the composite of the fibrous structure 23 is less hard. Each tooth 50 preferably has an elastic modulus less than 100 GPa, and preferably less than 50 GPa (i.e., less than half the modulus of the metal). Under these conditions, the torsional force is normally transmitted only from the sleeve to the fibrous structure, through the bond formed by the resin. In the event of a break in this bond, each tooth takes over to form a secondary load path.

Claims

1. DEMANDS 1. Variable pitch blade (7) for an aircraft turbomachine, comprising: - a tubular metal sleeve (13), this sleeve comprising a fixing part (14) configured to be connected to a variable shimming mechanism, and a recess (17) passing through the sleeve (13) along a shimming axis (Y), the recess (17) being delimited by an internal wall (18) of the sleeve (13), - a fibrous structure (20), the fibrous structure (20) comprising a blade root (22) comprising a tubular attachment portion (23) inserted axially into the recess (17) of the sleeve (13), this attachment portion (23) comprising a housing (20a) centered on the alignment axis (Y), the fibrous structure (20) further comprising an aerodynamically profiled blade (12) connected to the blade root (22), - an insert (24) centered on the alignment axis (Y) and inserted axially into the housing (20a) of the attachment portion (23) so that the attachment portion (23) is radially interposed between the insert (24) and the inner wall (18) of the sleeve (13), and - a polymerized resin for solidifying the fibrous structure (20) and for bonding the insert (24) to the fibrous structure (20) and to the inner wall (18) of the sleeve (13), characterized in that it further comprises at least one tooth (50) extending radially with respect to the axis (Y) and passing successively through the insert (24), the attachment portion (23) of the fibrous structure (20), and the sleeve (23), in order to form a force path in a circumferential direction around the axis (Y) between the sleeve (13) and the insert (24).

2. Blade (7) according to claim 1, wherein the tooth or each tooth (50) is brought into a housing (54) of the insert (24), of the attachment portion (23) of the fibrous structure (18), and of the sleeve (13).

3. Blade (7) according to claim 1 or 2, wherein the tooth or each tooth (50) comprises a radially internal end (50a) aligned with an internal surface (24a) of the insert (24), and a radially external end (50b) aligned with an external surface (34) of the sleeve (23).

4. Blade (7) according to any one of claims 1 to 3, wherein the tooth or each tooth (50) has a radial dimension (R1) greater than its axial dimension (L1).

5. Blade (7) according to any one of claims 1 to 4, wherein the tooth or each tooth (50) has a radial dimension (R1) greater than its angular extent (oc) around the axis (Y).

6. Blade according to any one of claims 1 to 5, wherein the tooth or each tooth (50) is made of metal.

7. Blade (7) according to any one of the preceding claims, wherein the tooth or each tooth (50) has an angular extent (oc) around the axis (Y) which is between 5 and 20°.

8. Blade (7) according to any one of the preceding claims, wherein the number of tooth(s) (50) is between 1 and 10 and for example between 2 and 6.

9. Blade according to any one of the preceding claims, wherein the tooth or teeth (50) have an elastic modulus lower than that of the sleeve (13) and preferably less than twice that of the sleeve (13).

10. Blade (7) according to the preceding claim, wherein the elastic modulus of the or each tooth is less than 100 GPa.

11. Blade (7) according to the preceding claim, wherein the fibrous structure is obtained by three-dimensional weaving of fibers.

12. Turbomachine, in particular for aircraft, comprising at least one blade (7) according to any one of the preceding claims.

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