ASSEMBLY INCLUDING A BLADE AND A BLADE RETAINING SYSTEM

Abstract

The invention relates to an assembly (101) comprising a blade (103) and a blade (105) retention system for an aircraft turbomachine. The blade (103) extends longitudinally along an axis (A), and the system (105) includes a pivot (113) configured to rotate about the axis (A). The system (105) further includes a movable jaw (117), and the pivot (113) includes a groove (113ba) in which the foot (111) and the movable jaw (117) are housed. The groove (113ba), the foot (111), and the movable jaw (117) together form a dovetail joint in which the foot (111) is held tightly. Figure for the abstract: Fig. 4

Description

Title of the invention: ASSEMBLY COMPRISING A BLADE AND A BLADE RETAINING SYSTEM Technical field

[0001] The invention relates to the field of fixed turbine blade architecture for aircraft turbines. It relates in particular to an assembly comprising a blade and a blade retention system. Prior art

[0002] In an unfaired turbomachine, so-called fixed blades, i.e. non-mobile in rotation around the longitudinal extent axis of the turbomachine, are coupled to a propeller and have the function of "straightening" the aerodynamic flow at the outlet of the propeller.

[0003] Similarly, in a shrouded turbomachine, such fixed blades are coupled to a fan located upstream of these fixed blades in the direction of flow within the turbomachine and comprising movable blades rotating about the axis of the turbomachine. As in the case of the unshrouded turbomachine, these fixed blades also serve to straighten the flow exiting the fan, which has been accelerated by the latter. This is also referred to as an outlet guide vane or OGV (from the English "Outlet Guide Vane").

[0004] In addition, these fixed blades can have variable pitch, that is to say, they can be part of an assembly which allows their rotation around their longitudinal extent axis so as to modify their orientation with respect to the direction of flow of the flux.

[0005] Fig. 1 thus shows, by way of example, a variable pitch blade 11 which includes a blade 13 which is mounted on a blade 15 retaining system which is mobile in rotation around the axis A and therefore allows the modification of its orientation.

[0006] In recent turbomachinery, and in particular in unshrouded turbomachinery, large-dimension blades are increasingly made of organic matrix composite materials insofar as these materials allow a significant mass reduction while retaining mechanical properties equivalent to those of materials used until then.

[0007] In the design and manufacture of composite material blades, the support to which the blade is attached is generally made of metallic material. It is this metallic part that can rotate in order to orient the composite blade which is fixed above it, and thus modify its angle of incidence relative to the flow.

[0008] For such a blade, the main type of stress experienced by the part involves bending movements induced by its angle of incidence, but also by the variation in the pressure field caused by the passage of the fan blades. Significantly larger amplitudes can also be observed in the event of impacts (propeller fragments, bird strikes, etc.) during extreme events.

[0009] The simplest means of fastening between a metal part and a composite part is bolting. For this purpose, two types of fasteners are commonly used, as illustrated in [Fig.2a] and [Fig.2b] in cross-sectional views perpendicular to the axis of the turbomachine of blade retaining systems 15 11.

[0010] Fig. 2a thus shows a clamping attachment (called "radial attachment") in which the composite parts 17 are shown in light grey and the screws 19 and the metal fixing part 21 are shown in dark grey.

[0011] Fig. 2b shows a tangential attachment in which the composite part 17 is shown in light grey and the metal fastening system 19 and 21 is shown in dark grey.

[0012] In the case of fixed blades with a radial attachment, it is the lower part of the blade that is subjected to the greatest stress. Moreover, the type of stress to which the blade is subjected produces an antisymmetric loading of the attachment, with one side in tension and the other in compression.

[0013] In particular, it is possible to distinguish two of the most critical areas related to this type of stress: - the radius of flanges 17a, whose bending stresses produce radial forces, favorable to so-called type I damage modes (i.e., opening (tension) and buckling (compression)); and, - the lateral part of the flanges 17a, corresponding to the fixings, where the forces are concentrated to be transmitted to the components located below the blade.

[0014] In all cases, the stresses on the composite part associated with this type of support system are likely to reduce the life of the part if special arrangements are not made to avoid these drawbacks. Summary of the invention

[0015] The present invention proposes a solution to these drawbacks.

[0016] To this end, the invention, according to a first aspect, relates to an assembly comprising a turbine blade and a blade retention system, for an aircraft turbomachine,

[0017] said blade extending longitudinally along an axis and comprising a blade and a foot, and

[0018] said system comprising a pivot configured to perform a rotation about the axis,

[0019] said assembly being characterized in that the system further comprises a jaw mobile and in that the pivot comprises a groove, in which are housed the foot (111) and said movable bit,

[0020] said groove, said foot and said movable jaw together forming a dovetail joint in which said foot is held tightly between an inclined plane of said groove, the bottom of said groove and a first inclined plane of said movable jaw, by means of fixing said movable jaw on said pivot.

[0021] The assembly according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0022] - the cross-section of the movable jaw has a trapezoidal shape, the smaller base of said trapezoid being positioned opposite the bottom of the throat and a second inclined plane of said movable jaw being positioned in support on an inclined plane complementary to said throat.

[0023] - the fastening means are screws, oriented parallel to the axis, inserted into complementary aligned orifices of the moving jaw and the pivot.

[0024] - a gap is left between the small base of the trapezoid and the bottom of the throat.

[0025] - the movable jaw is positioned in the groove on the extrados side of the blade.

[0026] - the pivot is a single piece comprising a cylindrical lower part, and a upper part having substantially a platinum shape and including the groove.

[0027] - the system further comprises at least one platform, mounted on the pivot, and of which the upper face is intended to be in contact with a flow running around the blade.

[0028] - a first platform is positioned on the extrados side of the blade and a second The platform is positioned on the intrados side of the wing.

[0029] - the system further comprises a support, mounted on the pivot, by means of of which the first platform is mounted on said pivot.

[0030] - the system further comprises at least one pin, inserted into at least one orifice complementary to the throat and housed in at least one cavity in the lower surface of the foot.

[0031] - the blade is made of an organic matrix composite material, for example made by three-dimensional weaving.

[0032] - dawn is a guiding exit dawn.

[0033] The invention according to a second aspect further relates to a turbomachine, in particular for aircraft, comprising at least one assembly according to the first aspect.

[0034] The invention according to a third aspect further relates to a method for assembling an assembly according to the first aspect, comprising the following steps:

[0035] - the insertion of the foot into the groove by sliding;

[0036] - the positioning of the movable jaw in the groove so that the first inclined plane the movable bit rests on an inclined plane complementary to the foot and the second inclined plane of the movable bit rests on the inclined plane of the throat;

[0037] - the insertion of the fastening means into the orifices of the movable jaw and the pivot; and,

[0038] - tightening the fastening means so that the foot is held tightly between the inclined plane of the throat, the bottom of the throat and the first inclined plane of the movable jaw. Brief description of the drawings

[0039] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0040] [Fig.1] is a perspective view of an assembly comprising a blade and a blade retention system according to an embodiment of the prior art;

[0041] [Fig.2a] is a schematic representation of a blade support system according to a first embodiment of the prior art;

[0042] [Fig.2b] is a schematic representation of a blade support system according to a second embodiment of the prior art;

[0043] [Fig.3] is a perspective view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;

[0044] [Fig.4] is a perspective and cross-sectional view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;

[0045] [Fig. 5] is a cross-sectional view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention; and,

[0046] [Fig.6] is a step diagram of a method for assembling an assembly comprising a blade and a blade retention system according to an embodiment of the invention. Description of the embodiments

[0047] With reference to [Fig.3], [Fig.4] and [Fig.5], we will now describe an embodiment of an assembly 101 comprising a blade 103 and a blade 105 retention system for an aircraft turbomachine (not shown).

[0048] The blade 103 extends longitudinally along an axis A and comprises a blade 109 and a foot 111. The axis A is orthogonal to an axis X of longitudinal extent of the turbomachine around which movable blades of the turbomachine rotate. The blade 103 is therefore mounted in the turbomachine, typically among other identical blades that belong to a row of so-called fixed blades.

[0049] This is a so-called fixed blade in the sense that it is not mobile in rotation about the longitudinal axis of the turbomachine in which it is mounted. However, as will become clearer below, the blade 103 is mobile in rotation about the axis A and can be said to have variable pitch, that is to say that its orientation relative to the flow in the turbomachine can be changed.

[0050] This may include, by way of non-limiting example, a so-called outlet guide vane or OGV (from the English "Outlet Guide Vane") belonging to a row of OGVs whose function is to straighten a flow from a propeller of an unfaired turbomachine or from a fan of a faired turbomachine.

[0051] In a particular embodiment, the blade 103 is made of an organic matrix composite material. It may have been produced, for example, by layering two-dimensional fibrous reinforcements, subsequently densified by resin, or by three-dimensional weaving of a single preform which is then densified.

[0052] Advantageously, this type of material allows for a significant mass reduction while maintaining mechanical properties equivalent to those of other heavier materials, or an improvement in mechanical properties for an equivalent mass, or a combination of both advantages.

[0053] In the assembly 101, the blade retaining system 105 includes a pivot 113 which is configured to rotate about axis A. Thus, in the example shown, the pivot 113 cooperates with ball bearings 114 which allow its rotation about axis A. In other embodiments, it could be rollers or any other means allowing the rotation of the pivot 113.

[0054] In the non-limiting example shown, the pivot 113 is a single piece, that is to say, it is not an assembly of several separate parts. Furthermore, the pivot 113 comprises a lower cylindrical part 113a (hollow in this example), and an upper part 113b which is substantially plate-shaped and includes a groove 113ba in which the foot 111 is housed.

[0055] The system 105 further includes a movable jaw 117 which is also housed in the groove 113ba. The movable jaw 117 is a separate part from the foot 111 and the pivot 113. In this sense, it is said to be "movable" insofar as it can be moved independently of the pivot 113 and the foot 111.

[0056] In addition, the groove 113ba, the foot 111 and the movable jaw 117 together form a dovetail assembly in which the foot 111 is held tightly between an inclined plane 113baa of the groove 113ba, the bottom 113bab of the groove 113ba and a first inclined plane 117a of the movable jaw 117, by means of fixing means 119 of the movable jaw 117 on the pivot 113.

[0057] In other words, the foot 111 is linked to the system 105 by a sliding connection in which the three faces indicated above (the two inclined planes and the bottom of the groove) are in contact with three complementary faces of the foot 111 when the assembly 101 is assembled so that the foot 111 is clamped in the system 105.

[0058] Advantageously, this arrangement prevents the loss of the blade 103 once the assembly of the set 101 has been completed.

[0059] Moreover, thanks to this arrangement as well, the stresses experienced by the dawn 103, in by particularly at the level of its foot 111, are diffused to the rest of the structure, notably via the bearings, which avoids their local concentration and the associated risks.

[0060] In the non-limiting example shown, the cross-section of the movable jaw 117 has a trapezoidal shape, and the small base of the trapezoid is positioned opposite the bottom 113bab of the groove 113ba and a second inclined plane 117b of the movable jaw 117 (i.e. the other inclined face of the trapezoid) is positioned in support on an inclined plane 113bac complementary to the groove 113ba.

[0061] In addition, the fastening means 119 are screws 119, oriented parallel to the axis A, and inserted into aligned holes 121 complementary to the movable jaw 117 and the pivot 113. A clearance j is also provided between the small base of the trapezoid (i.e. the lower surface part of the movable jaw 117) and the bottom 113bab of the groove 113ba.

[0062] Thus, the adjustment of the clamping level of the movable jaw 117 by the screws 119, made possible thanks to the presence of the play j, makes it possible to determine the intensity of the pressure which is exerted on the complementary inclined planes of the movable jaw 117 and contribute to tightening the foot 111 in the groove 113ba in fine.

[0063] Advantageously, the orientation of the fastening means 119, in this case the screws, allows easy access for maintenance when dismantling the blade 103. In addition, this orientation also prevents the screws from working in shear.

[0064] The terms "lower" and "upper" are defined relative to the drive axis (i.e., the X-axis of rotation of the moving blades of the turbomachine mentioned above). Thus, the lower parts mentioned below are those closest (radially) to the X-axis, while the upper parts mentioned in the following are those furthest (radially) from the X-axis.

[0065] In the example shown, five screws 119 are equally distributed along the longitudinal extent of the movable jaw 117. In general, a person skilled in the art will be able to adapt the number and spatial distribution of the means for fixing the movable jaw according to a desired tightening (and distribution of this tightening).

[0066] In the non-limiting example also shown, the movable jaw 117 is positioned in the groove 113ba on the extrados side of the blade 103. In other embodiments, insofar as the foot is straight, the movable jaw could be positioned on the other side.

[0067] In addition, the system 105 also includes at least one platform 125 which is mounted on the pivot 113 and whose upper face is intended to be in contact with a flow F (typically an airflow) which flows around the blade 109 during the use of the aircraft turbomachine.

[0068] In particular, the system 105 comprises a first platform 125a which is positioned on the extrados side of the blade 103 and a second platform 125b which is positioned on the intrados side of the blade 103.

[0069] In general, the platform(s) used have an aerodynamic role in the sense that their shape (in the example shown, a convex shape) is designed to optimize the flow of the flux over their surface while limiting their mass (for example via hollow areas within them).

[0070] Advantageously, the use of several platforms facilitates the assembly of the set 101 and a person skilled in the art will be able to adapt their number, greater than or equal to 1, to the specific geometry of an assembly used.

[0071] In the non-limiting example shown again, the system 105 further includes a support 127, mounted on the pivot 113, and through which the first platform 125a is mounted on the pivot 113. In particular, in this example, the support 127 has an L-shape, one arm of which is fixed on the pivot 113 (for example by screws not shown) and the other arm is configured to allow the fixing of the first platform and has holes adapted for this purpose.

[0072] In addition, as can be seen in [Fig.4] and [Fig.5], aligned through holes 128 of the support 127 and of the first platform 125a are provided to accommodate screws for fixing the first platform 125a to the support 127.

[0073] Similarly, with regard to the second platform 125b, through holes 130 of the second platform 125b and of the pivot 113 are provided to accommodate screws for fixing the second platform 125b onto the pivot 113. In the example shown, as can be seen in [Fig.3], the upper part 113a on pivot 113 even has a projection in which one of the holes 130 is located.

[0074] In the non-limiting example shown, the system 105 comprises at least one pin 129, inserted into at least one orifice 131 complementary to the groove 113ba and housed in at least one cavity in the lower surface of the foot 111. In particular, a plurality of pins 129 are distributed along the longitudinal extent of the groove 113ba. Advantageously, these pins allow for optimal axial positioning of the blade 103 during assembly of the assembly 101.

[0075] Advantageously, the assembly 101 according to the invention makes it possible to obtain an aerodynamic link for a fixed blade which leads to a reduction in the stress on its critical areas and good mechanical strength, while reducing the mass of the assembly.

[0076] In addition, a person skilled in the art will know how to adapt the shape of the different parts (such as the radius of curvature of the platforms 125) to avoid the concentration of stresses in a given area.

[0077] In addition, a person skilled in the art will know how to adapt the contact surface between the foot 111 and the various elements of the system 105 to optimize the distribution of the forces experienced by the blade 103 during its use, for example by increasing the embedment height of the foot 111 in the system 105.

[0078] Finally, in other embodiments (not shown), the shape of the foot 111 could have tapered or double tapered faces, in order to optimize the transmission of forces, limit the risks of slippage of the foot, and make the fastening means (described later) work in shear.

[0079] With reference to [Fig.6], we will now describe an implementation method of a method 601 for assembling the assembly 101 according to the invention.

[0080] A first step 603 consists of inserting the foot 111 into the groove 113ba by sliding it. The foot 111 slides in the groove 113ba along its longitudinal extent until it is fully positioned in the groove. Furthermore, during the insertion of the foot 111 into the groove 113ba, the pins 129 can be inserted into the cavity in the lower surface of the foot 111.

[0081] To facilitate the next step, the shape of the cavity can be oblong so that each pin can move in the cavity when the foot moves transversely in the groove 113ba under the action of the movable jaw 117.

[0082] The next step 605 consists of positioning the movable jaw 117 in the groove 113a so that the first inclined plane 117a of the movable jaw 117 is supported on a complementary inclined plane of the foot 111 and the second inclined plane 117b of the movable jaw is supported on the inclined plane 113bac of the groove 113ba.

[0083] The next step 607 consists of inserting the screws 119 into the holes 121 of the movable jaw 117 and the pivot 113.

[0084] The last step 609 consists of tightening the screws 119 so that the foot 111 is held tight between the inclined plane 113baa of the groove 113ba, the bottom 113bab of the groove 113ba and the first inclined plane 117a of the movable jaw 117.

[0085] Thus, as this method shows, the assembly (or disassembly) of the assembly 101 is simple and can, for example, be easily carried out upstream of the mounting of the assembly 101 on an aircraft turbomachine (for assembly) and also easily carried out when maintenance of a blade 103 is necessary (for disassembly).

Claims

Claims

1. An assembly (101) comprising a blade (103) and a system (105) for holding the blade (103), for an aircraft turbomachine, said blade (103) extending longitudinally along an axis (A) and comprising a blade (109) and a root (111), and said system (105) comprising a pivot (113) configured to rotate along the axis (A), said assembly (101) being characterized in that the system (105) further comprises a movable jaw (117) and in that the pivot (113) comprises a groove (113ba), in which the root (111) and said movable jaw (117) are housed, said groove (113ba), said root (111) and said movable jaw (117) together forming a dovetail assembly in which said root (111) is held clamped between an inclined plane (113baa) of said groove (113ba), the bottom (113bab) of said groove (113ba) and a first inclined plane (117a) of said movable jaw (117), by means of fixing means (119) of said movable jaw (117) on said pivot (113).

2. Assembly (101) according to claim 1, in which the cross section of the movable jaw (117) has a trapezoidal shape, the small base of said trapezoid being positioned opposite the bottom (113bab) of the groove (113ba) and a second inclined plane (117b) of said movable jaw (117) being positioned resting on an inclined plane (113bac) complementary to said groove (113ba).

3. Assembly (101) according to claim 1 or claim 2, in which the fixing means (119) are screws (119), oriented parallel to the axis (A), inserted into complementary aligned orifices (121) of the movable jaw (117) and of the pivot (113).

4. An assembly (101) according to claim 2 or claim 3, wherein a clearance (j) is provided between the small base of the trapezium and the bottom (113bab) of the groove (113ba).

5. An assembly (101) according to any preceding claim, wherein said movable jaw (117) is positioned in the groove (113ba) on the extrados side of the blade (103).

6. An assembly (101) according to any preceding claim, wherein the pivot (113) is a single piece comprising a cylindrical lower portion (113a), and an upper portion (113b) having a substantially platen shape and comprising the groove (113ba).

7. Assembly (101) according to any one of the preceding claims, in which the system (105) further comprises at least one platform (125), mounted on the pivot (113), and the upper face of which is intended to be in contact with a flow (F) flowing around the blade (109).

8. An assembly (101) according to claim 7, wherein a first platform (125a) is positioned on the extrados side of the blade (103) and a second platform (125b) is positioned on the intrados side of the blade (103).

9. An assembly (101) according to claim 8, wherein the system (105) further comprises a support (127), mounted on the pivot (113), by means of which the first platform (125a) is mounted on said pivot (113).

10. Assembly (101) according to any one of the preceding claims, in which the system (105) further comprises at least one pin (129), inserted into at least one orifice (131) complementary to the groove (113ba) and housed in at least one cavity in the lower surface of the foot (111).

11. Assembly (101) according to any one of the preceding claims, in which the blade (103) is made of organic matrix composite material, for example produced by three-dimensional weaving.

12. An assembly (101) according to any preceding claim, wherein the vane (103) is an outlet guide vane.

13. Turbomachine, in particular for an aircraft, comprising at least one assembly (101) according to any one of the preceding claims.

14. Method (501) for assembling an assembly (101) according to any one of claims 1 to 6, comprising the following steps: - inserting (603) the foot (111) into the groove (113ba) by sliding; - positioning (605) the movable jaw (117) in the groove (113a) so that the first inclined plane (117a) of the movable jaw (117) rests on a complementary inclined plane of the foot (111) and the second inclined plane (117b) of the movable jaw rests on the inclined plane (113bac) of the groove (113ba); - inserting (607) the fixing means (119) into the orifices (121) of the movable jaw (117) and of the pivot (113); and, - the tightening (609) of the fixing means (119) so that the foot (111) is held tight between the inclined plane (113baa) of the groove (113ba), the bottom (113bab) of the groove (113ba) and the first inclined plane (117a) of the movable jaw (117).

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