Fan rotor with variable pitch blades and turbine equipped with such a rotor

Abstract

The invention relates to a fan rotor with variable pitch blades, comprising a rotor disk provided with a plurality of rotary fasteners (16) at its outer periphery, each fastener (16) comprising a unit (17) for receiving a root (150) in a blade (15). The rotor is characterized in that an elongated wedge (2) and a prestressed rod (3) having at least one cam (33) are also arranged in each unit (17), the bottom of the unit (17) comprising as many retraction cavities (173) as the rod (3) comprises cams (33), the prestressed rod (3) being inserted between the wedge (2) and the bottom (171) of the unit (17) so that the cams (33) face the corresponding retraction cavities (173), and the prestressed rod (3) being able to rotate around the longitudinal axis (X2-X'2) of the prestressed rod between a rest position in which the cams (33) are accommodated in the retraction cavities (173) and a stressed position in which the cams (33) exert radial pressure on the central area (22) of the wedge (2) so as to move the wedge (2) towards the blade root (150).

Description

Technical Field

[0001] The invention belongs to the field of fans, ducted (fans) or unducted (propellers), rotors equipped with variable-pitch blades.

[0002] Potential applications are the aviation propulsion industry (e.g. turboprops, variable pitch fans (VPF), unducted fans (unducted single fans or USF), or unducted rotors with two counter-rotating propellers (counter-rotating open rotors or CROR)), but also the renewable energy industry (wind turbines).

[0003] The invention also relates to a turbomachine equipped with a fan rotor having variable-pitch blades. Background Art

[0004] Document FR 2 918 129 discloses a fan rotor comprising a rotor disk having cells arranged on its periphery, each of which is intended to receive a blade root of fixed pitch. The rotor comprises a wedge of three-dimensional woven composite material inserted between the blade root and the base of the metal cell, also made of three-dimensional woven composite material. During the forced installation of the wedge, it deforms elastically due to its longitudinal curvature and exerts pressure beneath the blade root, which has the effect of pressing the blade root against the supporting surface of the cell.

[0005] The two functions of the wedges are to ensure correct positioning of the blades in the disk and to dampen the impact of the blade roots against the base of the unit when an impact is induced (eg due to a bird ingestion into the rotor).

[0006] Fan rotors equipped with variable-pitch blades are also known in the prior art. Documents EP 3 010 799 or FR 3 017 163, for example, describe a pivot shaft comprising a blade support provided with a receptacle intended to receive a blade root. The blade support is secured to a rotary support radially mounted on the propeller hub and is capable of pivoting about the radial axis of the rotor.

[0007] Document WO2012 / 156633 describes a fan rotor whose blades do not have variable pitch and therefore do not include fasteners rotatably mounted around the pitch axis. This document simply describes the use of a wedge made of elastically deformable material that is inserted into a unit for receiving the blade root.

[0008] Document FR 2 934 873 describes a fan rotor provided with a unit for receiving a blade root in the form of a dovetail. A wedge is inserted between the blade root and the bottom of the unit.

[0009] A fan rotor with fixed-pitch blades is also known from document FR 2 881 174, in which the rotor disk is provided with a plurality of cells for receiving the blade roots. Deformable wedges are inserted between the base of the cells and the blade roots.

[0010] Document FR 3005683 describes a fan rotor with variable pitch blades, which is provided with a plurality of fasteners for receiving the blade roots. The fasteners include grooves for receiving the blade roots and wedges inserted into the grooves below the blade roots.

[0011] None of these four documents describes or suggests the use of prestressed rods.

[0012] The design of fan blades involves multiple disciplines whose objectives are often contradictory. The design of fan blades must enable optimal aerodynamic performance to be obtained (i.e., maximizing efficiency while providing thrust) and guaranteeing the mechanical strength of the blades (i.e., withstanding the mechanical stresses generated by static and dynamic loads) while limiting the mass and acoustic characteristics of the blades. In particular, for dual-flow engines, improvements in the aerodynamic performance of the fan tend to increase the bypass ratio, which translates into an increase in the outer diameter of the fan and, therefore, an increase in the span of the fan's blades.

[0013] Meanwhile, in the aforementioned architectures (VPF, USF, CROR and turboprop), the start of the engine is carried out with a very open pitch, known as "feathering".

[0014] In the attached Figure 1 and Figure 2 middle, Figure 1 and Figure 2 Conventional blade operation and feathered blade operation are shown respectively, and the blade A, the engine axis X, the propeller plane P, the pitch angle C and the angle of attack I can be seen.

[0015] Power is proportional to the product of speed and torque. However, torque increases with increasing angle of attack I, which can be increased by increasing pitch angle C. Activating feathering allows power to be dissipated through torque, which ensures the safety of the machine by maintaining a low fan speed.

[0016] As known to those skilled in the art, the resultant force on the blade profile (arrow F) is approximately perpendicular to the chord of the blade and can be decomposed into two components: the thrust along the engine axis X and the blade drag in the propeller plane P. Therefore, as the pitch of the blade increases, the resultant force shifts towards plane P, which has the effect of increasing the drag of the aerodynamic profile and reducing the thrust.

[0017] exist Figure 2 In the case of a fan, the thrust generated by the fan is zero, the torque is maximum, and the speed is minimum.

[0018] However, the angle of attack I becomes so large that blade A then experiences a strongly separated turbulent aerodynamic flow, which generates strong vibration excitation. In particular, in a blade having a large chord length and a large span that generates a large amount of drag, the aerodynamic force F is strong even at low speeds.

[0019] For variable pitch blades, assembled with a pivot similar to that described for example in documents EP 3 010 799 or FR 3 017 163, the aerodynamic forces F are so strong that they can induce a substantial movement of the blade root in its cell, similar to a "rolling up", see appendix Figure 3 The rotations shown in : roll i (rotation about the broaching axis of the blade), pitch ii (rotation about an axis perpendicular to the broaching axis and the radial axis) and finally yaw iii (rotation about the radial axis).

[0020] In fact, when feathering is activated, the reduced speed of the fan does not allow sufficient centrifugal force to be generated to prevent these movements caused by aerodynamic forces. Consequently, there is a risk of damaging the blades and the wedges inserted between the blade root and the housing of the "friction wear" type (micromotion), limiting the life of the fan blades.

[0021] For this reason, fastening by pivots as described above does not seem to be a viable solution for variable-pitch fan blades with a large chord length and a large span in this case. Summary of the Invention

[0022] It is therefore an object of the present invention to limit the rolling up of the blades when starting a feathered rotor and to avoid premature wear.

[0023] To this end, the invention relates to a fan rotor provided with variable-pitch blades, comprising a rotor disk provided with a plurality of fasteners at its outer periphery, each fastener being mounted rotatably relative to the rotor disk about a radial pitch axis and each fastener comprising a unit for receiving the root of one of the blades, an elongated wedge being arranged in each unit.

[0024] According to the present invention, the central portion of the blade root has a recess, and the blade root is arranged in the unit so that the recess of the blade root is oriented toward the bottom of the unit. A prestressed rod having at least one cam is also arranged in each unit. The wedge is made of an elastically deformable material, and at least one longitudinal section of the wedge has a transverse profile in the form of a circular arc. The central area of the wedge is curved so that the wedge includes a dome portion protruding in the concave direction of the circular arc and a hollow portion in the concave direction of the circular arc. The wedge is arranged in the unit so that the dome portion of the wedge faces the recess of the blade root, and the hollow portion of the wedge is oriented toward the bottom of the unit. The bottom of the unit includes as many retraction cavities as the rod has cams, the prestressing rod is inserted between the hollow part of the central area of the wedge and the bottom of the unit, so that the cam faces the corresponding retraction cavity, and the prestressing rod can be rotated around the longitudinal axis of the prestressing rod to be able to move between a rest position and an armature position, in which the cam is accommodated in the retraction cavity and in which the cam exerts radial pressure on the central area of the wedge to move the wedge in the direction of the blade root and so that the two lateral areas of the wedge arranged on both sides of the central area are in contact with the lateral areas of the blade root and away from the bottom of the unit.

[0025] Due to the presence of the prestressing rod, once it is in the stressed position, it is possible to deform the wedge so that it presses against the blade root, acting at the same time as a spring. This makes it possible to compensate for the loss of centrifugal force by applying a large preload below the blade root.

[0026] Compared to traditional broached fasteners (without prestressing rods), the invention makes it possible to limit premature wear of the blade during the feathering start-up phase.

[0027] Furthermore, the system is advantageous in terms of mass, volume and geometric tolerances.

[0028] Other advantageous and non-limiting features according to the present invention, taken alone or in combination:

[0029] A functional gap exists between the recess of the blade root and the dome portion of the central region of the wedge situated facing the recess, the functional gap being greater when the rod is in the rest position than when it is in the stressed position.

[0030] - the bottom of the unit is provided with a longitudinal groove intended to receive and guide the prestressing rod, said retraction cavity being arranged in this groove;

[0031] - the thickness of the wedge in the central region of the wedge is greater than the thickness of the end portions of the wedge;

[0032] - the wedge is composed of multiple segments connected by narrow joints;

[0033] - the fixing foil is arranged in the bottom of the unit of the fastener;

[0034] one of the ends of the prestressing rod, preferably the upstream end of the prestressing rod, has a shape, such as a cut edge, which enables the prestressing rod to be gripped and driven by a tool to rotate it about its longitudinal axis;

[0035] the prestressing rod has, near one of its ends, preferably its upstream end, a locating pin extending radially with respect to the longitudinal axis of the rod and projecting on the same side of the rod as the cam;

[0036] - an upstream axial retaining lock of the blade root, formed by a plate, is inserted into two upstream slots arranged at the upstream end of the side of the unit for receiving the blade root, the two upstream slots being arranged in a V-shape, and a rod locking piece is fastened to said upstream axial retaining lock, said rod locking piece being arranged with an opening for receiving one of the ends of the prestressing rod, preferably for receiving the upstream end of the prestressing rod, and a recess for receiving a positioning pin of said rod, in order to block said prestressing rod in the stressed position;

[0037] - a downstream axial retaining lock of the blade root formed by a plate is inserted into two downstream slots arranged at the downstream end of the side of the unit for receiving the blade root, the two downstream slots being arranged in a V-shape, the downstream retaining lock being drilled with a hole for receiving the downstream end of the wedge and having, on its inner surface, a surface forming an axial abutment for the downstream end of the stress rod;

[0038] - the wedge is made of 3D woven composite material;

[0039] -The blades are made of 3D woven composite material.

[0040] The invention also relates to a turbine equipped with a fan rotor having variable-pitch blades as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other characteristics, objects and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting and must be read with reference to the accompanying drawings, in which:

[0042] Figure 1 is a schematic diagram showing the operation of a blade in a conventional mode.

[0043] Figure 2 is a schematic diagram illustrating the operation of the blades in feathering mode.

[0044] Figure 3 is a schematic perspective view of the different rotations that a blade root housed in a prior art rotor disk unit can undergo.

[0045] Figure 4A is a schematic perspective view of a ductless fan equipped with two counter-rotating rotors according to the present invention.

[0046] Figure 4B yes Figure 4A A perspective partial cross-sectional view of a portion of a fan's rotor disk.

[0047] Figure 5 is a perspective view of a unit for receiving a blade root.

[0048] Figure 6 yes Figure 5 A perspective view of a unit arranged with a fixing foil.

[0049] Figure 7 yes Figure 5 Perspective view of a unit arranged with a fixing foil and with a prestressing rod in a rest position.

[0050] Figure 8 is similar to Figure 7 , but with the prestressing rods in stressed position.

[0051] Figure 9 is a perspective view of a wedge-shaped member and a prestressing rod in a rest position according to a first embodiment of the present invention.

[0052] Figure 10 is a perspective view of a wedge and a prestressing rod in a stressed position according to a second embodiment of the present invention.

[0053] Figure 11 Schematic transverse section of a prestressing rod, a wedge and a blade root arranged inside a unit of a rotor disk fastener, with the rod in rest position.

[0054] Figure 12 Schematic transverse section of a prestressing rod, a wedge and a blade root arranged inside a unit of a rotor disk fastener, the rod being in an intermediate position between a rest position and a stressed position.

[0055] Figure 13 is a schematic cross-sectional view of a prestressing rod, a wedge and a blade root arranged inside a unit of a rotor disk fastener, the rod in a stressed position.

[0056] Figure 14It is a longitudinal sectional view of the prestressing rod, the wedge, the blade root and part of the unit, the upstream and downstream retaining locks and the rod lock, taken along a sectional plane passing through the axis X2-X'2 of the rod 3.

[0057] Figure 15 is a perspective view of the downstream axial retention lock.

[0058] Figure 16A is a perspective view of the upstream axial retention lock.

[0059] Figure 16B is different from Figure 16A A perspective view of the upstream retaining lock taken from the perspective of FIG.

[0060] Figure 17 is a perspective view of the rod locking member.

[0061] Figure 18 is a perspective view of a rod locking piece and a prestressed rod held by the rod locking piece.

[0062] Figure 19 is a perspective view of the upstream end of the blade fastener, the prestressing rod, the upstream retaining lock and the rod lock, the upstream retaining lock and the rod lock being unassembled.

[0063] Figure 20 is a perspective view of the upstream end of the blade fastener, the prestressing rod, the upstream retaining lock and the rod lock, the upstream retaining lock and the rod lock being assembled.

[0064] Figure 21 is similar to Figure 13 A view showing the load paths during normal rotor operation.

[0065] Figure 22 is similar to Figure 13 , showing the load path if the blade root is subject to rolling. DETAILED DESCRIPTION

[0066] Reference Figure 4A , an example of an unducted fan 1 can be seen, which comprises two fan rotors 11, 12 according to the invention. The two fan rotors are mounted on a nacelle 13, which itself is intended to be fastened to the fuselage of the aircraft. Each rotor 11, 12 comprises a rotor disk 140 (or hub) and a plurality of blades 15 attached to the disk, to which an outer casing 14, which is mounted in rotation relative to the nacelle 13, is attached.

[0067] Plate 140 Figure 4A The disk is shown in dashed lines because the outer shell 14 hides the disk, but the disk is Figure 4B More visible in Figure 4BThe housing 14 is not shown.

[0068] In this application, upstream and downstream are defined relative to the normal flow direction of the gas in rotors 11 and 12. Furthermore, the rotor's axis of rotation is referred to as rotor axis X. An "axial" direction corresponds to the direction of axis X, while a "radial" direction is a direction perpendicular to and passing through the axis. Furthermore, a "circumferential" direction corresponds to a direction perpendicular to, but not passing through, axis X. Unless otherwise specified, "inner" and "outer" are used with reference to radial directions, such that an inner portion or surface of an element is closer to axis X than an outer portion or surface of the same element.

[0069] Furthermore, the rotor 11, 12 comprises a fastener 16 for each blade 15. Each fastener 16 is mounted rotatably about a radial pitch axis Y relative to the rotor disk 140.

[0070] More precisely, the fastener 16 is rotatably mounted in a housing arranged in the rotor disk by means of a ball or other rolling element. The fastener 16 is also referred to in the literature as a "pivot." For information on this pivot assembly, reference may be made to document FR 2 943 312.

[0071] like Figure 5 As shown more clearly in FIG, each fastener 16 comprises a unit 17 for receiving a root 150 of a blade 15, the root having, for example, the shape of a dovetail. Figures 7 to 13 More clearly visible.

[0072] The fastener 16 comprises two sides 161 and 162 which define between them an upper radial opening 170 of the unit 17, opposite the unit's bottom 171. The two sides 161 and 162 are inclined towards each other and form a bearing surface.

[0073] Each side surface 161, 162 is provided with a downstream groove 1611, 1621 and an upstream groove 1612, 1622, respectively. The two downstream grooves 1611, 1621 arranged at the downstream end of the unit 17 face each other and are arranged in a V-shape. The same is true for the two upstream grooves 1612, 1622 (see Figure 5 ).

[0074] The unit 17 extends in the axial direction between an inlet on the leading edge side of the blade and an inlet on the trailing edge side of the blade. The blade root can be engaged in the unit 17 by sliding through one of the two opposite inlets.

[0075] The present invention will be better understood by describing in more detail the relationship between the various forces acting on a blade with a pivoting fastener. On the one hand, the centrifugal force exerted on blade 15 is directed in the radial direction, and its magnitude is proportional to the square of the rotor's rotational speed. Therefore, this force depends largely on the engine speed. On the other hand, the centrifugal force presses blade root 150 against support surfaces 161, 162 of unit 17, thereby ensuring the retention of the blade root. In other words, each support surface of the unit generates a reaction force on blade root 150 that is directed along the normal to the contact surface, and the resultant of these forces opposes the centrifugal force. It can be inferred that the magnitude of the reaction forces at support surfaces 161, 162 is directly related to the centrifugal force. However, these reaction forces also play another very important role, as they counteract the moment of the aerodynamic force that causes blade 15 to roll up. Thus, in the case of feathering start, characterized by reduced engine speed and turbulent aerodynamic flow, the low centrifugal forces induce reaction forces at the bearing surfaces 161 , 162 that are insufficient to counteract the moment causing the strong aerodynamic forces that cause the blade 15 to roll up.

[0076] The invention consists in compensating for low centrifugal forces by applying a large preload below the blade root 150. To this end, a wedge 2 and a prestressing rod 3 with at least one cam are mounted between the blade root 150 and the bottom 171 of the unit.

[0077] Now refer to Figures 9 to 13 Next, wedge 2 will be described.

[0078] The wedge 2 has a generally elongated shape. The wedge has a straight profile along the longitudinal direction of the wedge, which is defined by Figure 9 and Figure 10 The axis X1-X'1 in FIG. 1 is schematically shown.

[0079] The wedge 2 is constructed from a single block of elastically deformable material. This material can be, for example, aluminum. Advantageously, however, the material is a 3D (three-dimensional) woven composite material, such as an "interlock weave" type. An "interlock weave" as used herein is a 3D weave pattern in which each layer of warp yarns connects multiple layers of weft yarns, and all yarns in the same warp column have the same motion in the weave plane.

[0080] Also preferably, the material is anisotropic and has a greater stiffness in the broaching direction (ie along the axis X1-X'1) than in the direction of transmitting the force of the cam to the blade root (circumferential direction Z-see Figure 11 )'s stiffness.

[0081] The wedge 2 comprises at least one longitudinal section. Figure 9 and Figure 10In the exemplary embodiment shown, the wedge 2 comprises three longitudinal sections 20a, 20b, 20c (the number of longitudinal sections may be different) connected by a narrow joint 21 made of the same material, the assembly forming a single component.

[0082] like Figure 11 As shown more clearly in FIG, each longitudinal segment 20a, 20b, 20c has a transverse profile in the form of an arc of a circle, the central region 22 of the wedge being curved so that the wedge has a dome portion 221 protruding in the concave direction of the arc of the circle and a hollow portion 220 in the concave direction of the arc of the circle. The two lateral regions 23, 24 of the wedge are arranged at the two ends of the arc of the circle.

[0083] The wedge 2 is arranged in each unit 17 so as to be inserted between the blade root 150 and the prestressing rod 3, and so that its two lateral areas 23, 24 are in contact with the corresponding lateral areas 151, 152 of the blade root 150, while being away from the bottom 171 of the unit 17, and the central area 22 of the wedge faces the central area 153 of the blade root 150.

[0084] The wedge 2 has a downstream end 25 and an upstream end 26 (see Figure 9 ).

[0085] Now refer to Figures 7 to 11 A prestressing rod 3 is described which has at least one cam.

[0086] The rod 3 is cylindrical and has two ends, an upstream end 31 and a downstream end 32 .

[0087] The rod has a longitudinal axis X2-X'2. The rod comprises at least one cam 33, preferably formed in one piece with the rest of the rod. This cam 33 projects over a portion of the circumference of the rod. The rod 3 may comprise more than one cam 33, for example two cams distributed over the length of the rod (see Figure 10 ) or three cams (see Figures 7 to 9 ), or include more than three cams.

[0088] Preferably, the prestressing rod 3 is made of steel or titanium alloy.

[0089] Advantageously, the bottom 171 of the unit is prepared and has a longitudinal groove 172 (preferably a machined longitudinal groove, see Figure 5 ) to receive the rod 3. The groove 172 has as many retraction chambers 173 as the rod 3 has cams 33, and each retraction chamber 173 is used to receive the cam 33.

[0090] This groove 172 is intended to guide and support the rod 3 in the region of the groove that does not have a cam. When the rod 3 is in the groove, the rod acts as a lower half bearing.

[0091] Once the rod is arranged in the groove, the rod 3 can be manipulated in rotation to pivot it about its longitudinal axis X2-X'2 by means of a tool. For this purpose, advantageously, one of the ends of the rod (preferably the upstream end 31 of the rod) has a cut edge that facilitates the gripping of the rod (see Figure 9 ).

[0092] Advantageously, the prestressing rod 3 may comprise a positioning pin 34, preferably arranged near the upstream end 31 (see for example Figure 9 and Figure 18 ).exist Figure 10 In the figure, the cross section makes the dowel pins invisible.

[0093] The positioning pin 34 extends radially relative to the longitudinal axis X2 - X′ 2 of the rod 3 and is oriented so as to project on the same side of the rod 3 as the cam 33 .

[0094] Therefore, when the positioning pin 34 is Figure 9 When extending downward (ie in a radially inward direction towards the centre of the rotor disc 140), the rod 3 is in a position referred to as a “rest” position, when the locating pin is in Figure 18 When extending in an upward direction (ie in a radially outward direction towards the exterior of the rotor disk 140 ), the rod 3 is in a position referred to as a “stressed” position.

[0095] according to Figure 10 In the variant embodiment schematically shown in FIG, oblong holes 25 are arranged in the central region 22 of at least some of the segments 20a, 20b, 20c to further improve the flexibility and deformability of the different parts of the wedge 2. These oblong holes 25 also make it possible to lighten the wedge. The oblong holes are positioned so as not to come into contact with the cam 33 of the prestressing rod 3.

[0096] Advantageously and from Figure 6 As can be seen better in FIG, a metal fixing foil 4 is arranged at the bottom of the unit 17 to protect it from friction with the rod 3. This fixing foil 4 also extends to the bearing surfaces 161, 162 of the unit to protect the fastener 16 from friction with the blade root 150. Preferably, the fixing foil 4 is perforated around the friction-free retraction cavity 173 (see the holes marked 40) and around the grooves 1611, 1621, 1612, 1622.

[0097] The fixing foil 4 is preferably made of stainless steel and preferably has a thickness of a few tenths of a millimeter.

[0098] Other protective elements may also be present to protect the components made of composite materials. For example, impregnated fabrics (or wear strips) designed specifically to resist friction may be mounted on the bearing surface of the blade root 150 in the area of contact with the unit and on the wedge 2 in the area of contact with the cam 33 or the blade root 150.

[0099] Advantageously, as Figures 11 to 13 As shown, the shape of the transverse section of the base of the blade root 150 can have a central recess 154 (shaped like a bone) so as to adapt itself optimally to the presence of the wedge 2 and the prestressed rod 3 with cam. This particular form makes it possible to free up space under the blade root for integrating the wedge and the rod while limiting the drilling of the unit 17.

[0100] However, this is not the only function of the bone shape, which also serves as an abutment for the cam 2 by form fit in the event of uncontrolled rolling up of the blade (eg bird ingestion), as will be explained subsequently.

[0101] The axial retention of the blade root 150, the wedge 2 and the rod 3 is ensured by downstream axial retention locks 5 and upstream axial retention locks 6, and the locking of the rod 3 in its stressed position is ensured by a rod lock 7. These three locks are preferably made of metal.

[0102] Figure 15 An exemplary embodiment of a downstream axial retaining lock 5 is shown in FIG.

[0103] This locking element 5 comprises a plate 50 having a pentagonal shape, with two lateral edges 51, 52 (called "locking" edges) and two radially inner edges 54, 55 connected by a radially outer edge 53. The plate 50 has an inner surface 56 on which is arranged a honeycomb damping element 57. Finally, the plate 50 is drilled with a hole 58 arranged between the two edges 54, 55, lower than the honeycomb 57.

[0104] The plate 50 is dimensioned so that its two lateral edges 51, 52 can be inserted into the downstream grooves 1611 and 1621 of the fastener 16, respectively, from the inside to the outside in the radial direction, i.e. Figures 5 to 8 From bottom to top.

[0105] The tip of the locking element 5 , which is arranged between the two edges 54 , 55 of the locking element, below the hole 58 , is referenced 59 .

[0106] Figure 16A and Figure 16BAn exemplary embodiment of an upstream axial retention lock 6 is shown in FIG. This lock 6 comprises a plate 60 having a hexagonal shape, with two lateral edges 61, 62 (called "locking" edges) connected by a radially outer edge 63, and two inner lateral edges 64, 65, which are inclined towards each other and connected by a radially inner edge 66 opposite the edge 63. The plate 60 has an inner surface 601, on which a honeycomb damping element 67 is arranged, and an opposite outer surface 602, which is extended outwards by a vertical wing 68 drilled with at least one hole 680, in which case two holes are drilled.

[0107] The plate 60 is dimensioned so that its two lateral locking edges 61, 62, inclined in a V-shape, can be inserted into the upstream grooves 1612, 1622 of the fastener 16, respectively, from the inside to the outside in the radial direction, i.e., at Figures 5 to 8 In this position, the honeycomb 67 abuts the blade root 150 , which the locking element 6 axially blocks.

[0108] Now combine Figure 17 and Figure 18 The following describes the lever locking member 7. The locking member 7 has the general shape of a bridge. The locking member comprises a U-shaped portion 70, which defines a through hole 71 at its lower portion. The U-shaped portion is blocked at its upper portion by a plate 72, which extends beyond the U-shaped portion on both sides to provide two wing members 720. Each wing member 720 is bored with a hole 721.

[0109] The recess 73 is arranged in the central portion of the plate 72, between the central portion of the plate and the inner surface 700 of the U-shaped portion 70 (i.e. the surface intended to be turned towards the unit 17 when the rod locking piece 7 is in place, see Figure 14 ) at the junction.

[0110] exist Figure 14 and Figure 20 In FIG. 7 , it can be seen that the opening 71 is configured to receive the upstream end 31 of the rod 3 such that the outer periphery of this end (and eg the cut edge of this end) is no longer accessible and cannot be rotationally manipulated.

[0111] exist Figure 14 and Figure 18 In FIG. 7 , it can be seen that the recess 73 is configured to receive the radial positioning pin 34 when the prestressing rod 3 is in the stressed position, ie when the cam 33 is pressed against the wedge 2 .

[0112] The rod lock 7 can be assembled with the upstream retaining lock 6 by applying the plate 72 against the wing 68, by aligning the holes 721 with the holes 680, and by inserting the assembly members 8, such as screws and nuts, into these holes (see Figure 20 ).

[0113] The sequence for assembling the blade root 150 into the unit 17 of the fastener 16 follows the following steps:

[0114] - installing the metal fixing foil 4 in the bottom 171 of the unit 17 of the pivot fastener 16,

[0115] - Mounting the prestressing rod 3 at the bottom of the unit 17 so that it is in a rest position, with the cam 33 housed in the retraction chamber 173 (see Figure 7 ),

[0116] - The downstream retaining lock 5 is mounted in the downstream guide slots 1611, 1621, with the end 32 of the rod 3 coming into abutment with the tip 59 of the lock 5 (see Figure 10 ),

[0117] - inserting the blade root 150 inside the cell 17 of the fastener 16 by sliding until it comes into abutment against the honeycomb 57 of the downstream retaining lock 5 ,

[0118] - installing the upstream retaining lock 6 in the upstream guide slots 1612 , 1622 , with the honeycomb 67 coming into abutment with the blade root 150 ,

[0119] - The wedge 2 is introduced between the blade root 150 and the prestressing rod 3, the downstream end 25 of the wedge 2 penetrating the hole 58 of the downstream retaining lock 5 (see Figure 14 ). Then appeared Figure 11 Since there is a gap J between the surface of the rod 3 without the cam 33 and the bottom of the recess 154 of the blade root 150 (see Figure 11 ), and the wedge 2 is straight along its longitudinal axis X1-X'1, so that the assembly of the wedge 2 can be carried out without difficulty.

[0120] - Apply torque to the upstream end 31 of the prestressing rod 3 using a tool ( Figure 12 The cam 33 is rotated by 180° (arrow G in FIG) to complete the 180° rotation, thereby engaging the cam 33 in the hollow 220 of the central region 22 of the wedge 2. During this rotation, the geometry of the cam 33 creates a hard point felt by the operator, during which the wedge 2 is slightly overstressed (see FIG. Figure 12 ) without ever coming into contact with the central recess 154 of the blade root 150. There is a gap J1 between the bottom of the recess 154 and the dome portion 221 (see Figure 12 ), the gap is suitable for making the wedge 2 able to perform this temporary deformation. Once through the hard point, continue to rotate the rod 3 into Figure 13 The new equilibrium position (stressed position) is shown. The value of gap J1 varies depending on the orientation of cam 33. The geometry of cam 33 is symmetrical and has hard points on both sides of this stressed equilibrium position, preventing the system from being able to unstress itself in one direction or the other without force provided by the operator. Figure 13 In the position of , the cam 33 is supported on the wedge 2 and causes the deformation of the wedge. Figure 12 and Figure 13 In FIG, the dotted line arranged below the cam 2 shows the shape of the cam when it is not stressed.

[0121] - Install the rod lock 7 and screw it to the upstream retaining lock with the bolt 8 (see Figure 14 and Figure 20 ).

[0122] Another advantage of the rod locking element 7 is that the notch 73 and the U-shaped portion 70 surround the dowel pin of the prestressing rod, preventing its assembly if the prestressing rod 3 is not forced. Figure 19 As shown, when the dowel pin 34 is oriented downwards (rod 3 is at rest), the U-shaped portion 70 abuts against the dowel pin, the hole 721 cannot be aligned with the hole 680, and assembly is impossible. This prevents assembly of the blade without preloading of the root 150.

[0123] When all the parts are assembled and under duress:

[0124] - downstream retaining lock 5 serving as downstream abutment for prestressing rod 3 and wedge 2,

[0125] - the wedge 2 forced by the prestressing rod 3 pushes the upstream retaining lock 6 and the downstream retaining lock 5 into the corresponding V-shaped grooves of the fastener 16,

[0126] - the positioning pin 34 of the prestressing rod 3 serves as an upstream abutment for the wedge 2 ,

[0127] The rod lock 7 acts as an upstream abutment for the prestressing rod 3 , locking the force applied to the rod 3 and preventing access to the control for rotating the prestressing rod 3 .

[0128] Disassembly of the blades can be easily performed by performing these steps in reverse order.

[0129] When the system is stressed, the rod 3 with the cam acts to impose a radial outward movement on the central portion 22 of the wedge 2, the ends 23, 24 of which are supported by the blade root 150. The wedge 2 then acts as a spring, since the radial force generated depends on the structural stiffness of the wedge. By analogy, the wedge 2 can also be considered as a beam section bent at three points in its transverse cross-section. The central force exerted on the wedge 2 by the cam 33 is equal to the sum of the forces exerted on the blade root 150 by the ends 23, 24 of the wedge. The force transmitted to the blade root depends on the bending, i.e. the radial outward movement, imposed on the central portion of the wedge 2 by the cam 33 when the system is stressed. Using the same analogy, the internal stresses in the wedge 2 are considered to be maximum in the central portion and at the surface of the wedge. Therefore, the advantage of this system is that the preload force on the blade root 150 can be adjusted by acting on the geometry of the cam 33, the geometry of the wedge 2, or the material of the wedge 2.

[0130] However, the wedge 2 must resist the internal pressure generated by the bending of the wedge. Therefore, it is preferred that the wedge has a minimum thickness, especially in the center of the wedge, but is not too hard. Therefore, advantageously and in order to meet this compromise, the thickness of the wedge 2 decreases from the center ( Figure 13 The thickness E1 in the middle decreases toward the end (thickness E2), where E1 is greater than E2.

[0131] It is then important not to lose the assembly preload due to centrifugal forces which would push the blade roots radially outwards (at Figures 11 to 13 1 and upwards), thereby relaxing the deformation of the wedge 2. This means that the radially outward movement imparted by the cam 33 is greater than the radially outward movement of the blade root 150 in the start-up state. Therefore, to achieve the target preload force, it is preferable to reduce the stiffness of the wedge 2, for example by reducing its thickness E1, and to increase the movement imparted by the cam 33 by increasing its size.

[0132] exist Figure 21 In the figure, the dashed arrows illustrate the force paths when the prestressing rod 3 is in the stressed position and the rotor is in normal operation. Force is transmitted from the central portion 22 of the wedge 2 to its ends 23 and 24, which contact the blade root. The functional gap J1 between the domed portion 221 of the wedge 22 and the recessed portion 154 of the blade root 150 enables the wedge 2 to function as a spring. This maintains the preload as the blade 15 moves under the influence of centrifugal force.

[0133] Figure 22The figure shows a situation where the prestressing rod 3 is stressed, but the preload becomes insufficient to counteract the rolling up of the blade root 150 (e.g., due to excessive aerodynamic forces or bird ingestion into the rotor blade). In this case, the blade root 150 not only rolls up (arrow H), but also drops into the cell 17. The contact surface between the wedge 2 and the blade root 150 approaches the contact surface between the wedge 2 and the cam 33. The force path (dashed line) is shortened, and it is the compression of the wedge 2 through its thickness that directly opposes the rolling up of the blade. The wedge 2 acts as an abutment. The value of the gap J1 decreases.

[0134] Finally, it will be noted that the different sectors 20a, 20b, 20c of the wedge 2 react respectively to the movements of the blade 15, making it possible to follow as closely as possible the movements of each of the portions of the blade root 150.

[0135] It should be noted that there is a gap J1 between the recess 154 of the blade root 150 and the dome portion 221 of the central zone 22 of the wedge 2 arranged facing this recess, this gap being greater when the rod 3 is in the rest position than when it is in the stressed position.

[0136] In the foregoing description, the blade 15 is made of 3D woven composite material according to the general principles of known blades made of composite materials, the blade having a woven preform impregnated with resin, however, the root of the blade is adapted to comply with the provisions of the root described in the corresponding paragraph of the foregoing description.

Claims

1. A fan rotor (11, 12) arranged with variable pitch blades (15), comprising a rotor disk (140), wherein a plurality of fasteners (16) are arranged on the outer periphery of the rotor disk, each fastener (16) being mounted rotatably relative to the rotor disk about a radial pitch axis (Y), and each fastener (16) comprising a unit (17) for receiving a blade root (150) of one of the variable pitch blades (15), wherein an elongated wedge (2) is arranged in each unit (17), characterized in that The central portion (153) of the blade root (150) has a recess (154), the blade root (150) is arranged in the unit (17) so that the recess (154) of the blade root is oriented towards the bottom (171) of the unit (17), a prestressing rod (3) having at least one cam (33) is also arranged in each unit (17), the wedge (2) is made of an elastically deformable material, at least one longitudinal section (20a, 20b, 20c) of the wedge (2) has a transverse profile in the form of a circular arc The central area (22) of the wedge is curved so that the wedge comprises a dome portion (221) protruding in the concave direction of the circular arc and a hollow portion (220) in the concave direction of the circular arc, the wedge (2) is arranged in the unit (17) so that the dome portion (221) of the wedge faces the concave portion (154) of the blade root (150), and the hollow portion (220) of the wedge is oriented toward the bottom (171) of the unit, the bottom (171) of the unit (17) comprising The prestressing rod (3) has as many retraction chambers (173) as cams (33), the prestressing rod (3) being inserted between the hollow portion (220) of the central region (22) of the wedge (2) and the bottom (171) of the unit (17) so that the cams (33) face the corresponding retraction chambers (173), and the prestressing rod (3) is rotatably movable around the longitudinal axis (X2-X'2) of the prestressing rod so as to be movable between a rest position and a stressed position, in which the cams (3) are in the rest position. 3) is accommodated in the retraction cavity (173), and in the stressed position, the cam (33) applies radial pressure on the central area (22) of the wedge (2) to move the wedge (2) in the direction of the blade root (150) and to make the two lateral areas (23, 24) of the wedge arranged on both sides of the central area (22) of the wedge contact with the corresponding lateral areas (151, 152) of the blade root (150) and away from the bottom (171) of the unit (17).

2. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 1, characterized in that: A functional gap (J1) exists between the recess (154) of the blade root (150) and the dome portion (221) of the central region (22) of the wedge (2) arranged to face the recess, the functional gap (J1) being greater when the prestressing rod is in a rest position than when the prestressing rod is in a stressed position.

3. The fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: The bottom (171) of the unit (17) is provided with a longitudinal groove (172) intended to receive and guide the prestressing rod (3), the retraction cavity (173) being arranged in this longitudinal groove (172).

4. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 1 or 2, characterized in that: The thickness (E1) of the wedge-shaped member (2) in the central region (22) of the wedge-shaped member is greater than the thickness (E2) of the end portions of the wedge-shaped member.

5. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 1 or 2, characterized in that: The wedge (2) is composed of a plurality of longitudinal sections (20a, 20b, 20c) connected by narrow joints (21).

6. A fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: A fixing foil (4) is arranged in the bottom portion of the unit (17) of the fastener (16).

7. A fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: One of the ends of the prestressed rod (3) has a shape that enables the prestressed rod to be clamped and driven by a tool to rotate around the longitudinal axis (X2-X'2) of the prestressed rod.

8. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 1 or 2, characterized in that: The prestressing rod (3) has a positioning pin (34) near one of its ends, which extends radially relative to the longitudinal axis (X2-X'2) of the prestressing rod (3) and protrudes on the same side of the prestressing rod (3) as the cam (33).

9. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 8, characterized in that: The upstream axial retaining lock (6) formed by a plate of the blade root (150) is inserted into two upstream slots (1612, 1622), which are arranged at the upstream ends of the side surfaces (161, 162) of the unit (17) for receiving the blade root (150), the two upstream slots (1612, 1622) being arranged in a V-shape, and a rod locking member (7) is fastened to the upstream axial retaining lock (6), the rod locking member (7) being arranged with an opening (71) for receiving one of the ends of the prestressing rod (3) and a recess (73) for receiving the positioning pin (34) of the prestressing rod (3) to block the prestressing rod (3) in the stressed position.

10. A fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: The downstream axial retaining lock (5) formed by a plate of the blade root (150) is inserted into two downstream slots (1611, 1621), which are arranged at the downstream end of the side (161, 162) of the unit (17) for receiving the blade root (150), and the two downstream slots (1611, 1621) are arranged in a V shape, and the downstream axial retaining lock (5) is drilled with a hole (58) for receiving the downstream end (25) of the wedge (2), and the downstream axial retaining lock (5) has a surface (59) on the inner surface (56) of the downstream axial retaining lock, which forms an axial abutment portion for the downstream end (32) of the prestressed rod (3).

11. A fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: The wedge-shaped piece (2) is made of a 3D braided composite material.

12. A fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 1 or 2, characterized in that: The variable pitch blade (15) is made of a 3D braided composite material.

13. The fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 7, characterized in that: One of the ends of the prestressed rod (3) is an upstream end (31) of the prestressed rod.

14. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 7, characterized in that: The shape is a cut edge.

15. The fan rotor (11, 12) provided with variable pitch blades (15) according to claim 8, characterized in that: One of the ends of the prestressed rod is an upstream end (31) of the prestressed rod.

16. The fan rotor (11, 12) arranged with variable pitch blades (15) according to claim 9, characterized in that One of the ends of the prestressed rod (3) is an upstream end (31) of the prestressed rod.

17. A turbine, characterized in that: The turbine comprises a fan rotor (11, 12) arranged with variable pitch blades (15) according to any one of claims 1 to 16.

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