Assembly comprising a blade and a system for holding the blade

Abstract

The invention relates to an assembly (101) which comprises a blade (103) and a system (105) for holding the blade (103), and which is intended for an aircraft turbine engine. The blade (103) extends longitudinally along an axis (A) and the system (105) comprises a pivot (113) configured to rotate about the axis (A). The system (105) further comprises a mobile jaw (117) and the pivot (113) comprises a groove (113ba), in which the root (111) and the mobile jaw (117) are received. The groove (113ba), the root (111) and the mobile jaw (117) together form a dovetail assembly in which the root (111) is kept clamped.

Description

[0001] Description

[0002] TITLE: ASSEMBLY COMPRISING A DAWN AND A DAWN HOLDING SYSTEM

[0003] TECHNICAL FIELD

[0004] The invention relates to the field of fixed blade architecture for aircraft turbomachines. It relates in particular to an assembly comprising a blade and a blade holding system.

[0005] PRIOR ART

[0006] The state of the art includes in particular documents FR-A1-3128972, FR-A1-3126729, EP-B1-4045398 and US-A1-2020063577.

[0007] In an unducted turbomachine, so-called fixed blades, i.e. blades that are not mobile in rotation around the longitudinal axis of the turbomachine, are coupled to a propeller and have the function of "straightening" the aerodynamic flow at the outlet of the propeller.

[0008] Similarly, in a ducted turbomachine, such fixed blades are coupled to a fan which is located upstream of these fixed blades in the direction of flow of the flow in the turbomachine and which comprises moving blades rotating around the axis of the turbomachine. As in the case of the unducted turbomachine, these fixed blades also have the function of straightening the flow from the fan which has been accelerated by it. This is also referred to as an outlet guide vane or OGV (from the English "Outlet Guide Vane")

[0009] Furthermore, these fixed blades can be variable pitch, that is to say they can be part of an assembly which allows their rotation around their longitudinal axis so as to modify their orientation relative to the direction of flow of the stream.

[0010] Figure 1 thus shows, by way of example, a variable-pitch blade 11 which comprises a blade 13 which is mounted on a system 15 for holding the blade 11 which is movable in rotation around the axis A and therefore allows its orientation to be modified.

[0011] In recent turbomachines, and particularly in unducted turbomachines, large blades are increasingly frequently made from organic matrix composite materials, as these materials allow a significant weight saving while retaining mechanical properties equivalent to those of materials used previously.

[0012] In the design and manufacture of composite 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 attached above it, and thus modify its incidence relative to the flow.

[0013] For such a blade, the main type of stress seen by the part concerns bending movements induced by its incidence, but also by the variation of the pressure field caused by the passage of the fan blades. Significantly larger amplitudes can also be seen in the event of impacts (pieces of propeller, bird, others...) during extreme events.

[0014] The simplest means of attachment between a metal part and a composite part is bolting. For this purpose, two types of fasteners are commonly used, as illustrated in Figure 2a and Figure 2b in sectional views perpendicular to the axis of the turbomachine of systems 15 for holding the blade 11. Figure 2a thus shows an attachment by clamping (called “radial attachment”) in which the composite parts 17 are shown in light gray and the screws 19 and the metal attachment part 21 are shown in dark gray.

[0015] Figure 2b shows a tangential attachment in which the composite part 17 is shown in light gray and the metal attachment system 19 and 21 is shown in dark gray.

[0016] In the case of fixed blades with radial attachment, it is the lower part of the blade that is most stressed. In addition, 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. In particular, it is possible to distinguish two most critical zones linked to this type of stress: the radius of the flanges 17a, whose bending stresses produce forces in the radial direction, favorable to damage modes called type I (i.e. opening (tension) and buckling (compression)); and, the lateral part of the flanges 17a, in correspondence with the attachments, where the forces are concentrated to be transmitted to the components located below the blade.

[0017] In any case, the stresses on the composite part associated with this type of holding system are likely to reduce the life of the part if special arrangements are not made to avoid these drawbacks.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention provides a solution to these drawbacks.

[0020] To this end, the invention according to a first aspect relates to an assembly comprising a blade and a blade holding system, for an aircraft turbomachine, said blade extending longitudinally along an axis and comprising a blade and a root, and said system comprising a pivot configured to rotate along the axis, said assembly being characterized in that the system further comprises a movable jaw and in that the pivot comprises a groove, in which the root and said movable jaw are housed, said groove, said root and said movable jaw together forming a dovetail assembly in which said root is held clamped 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 means of said movable jaw on said pivot, and in that the cross-section of the movable jaw has a trapezoidal shape,the small base of said trapezium being positioned opposite the bottom of the groove and a second inclined plane of said movable jaw being positioned resting on an inclined plane complementary to said groove.,

[0021] The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another:

[0022] - the fixing means are screws, oriented parallel to the axis, inserted into complementary aligned holes in the movable jaw and the pivot.

[0023] - there is clearance between the small base of the trapeze and the bottom of the groove.

[0024] - the movable jaw is positioned in the groove on the extrados side of the blade.

[0025] - the pivot is a single part comprising a cylindrical lower part, and an upper part having a substantially plate shape and comprising the groove.

[0026] - the system further comprises at least one platform, mounted on the pivot, and the upper face of which is intended to be in contact with a flow flowing around the blade.

[0027] - a first platform is positioned on the extrados side of the blade and a second platform is positioned on the intrados side of the blade.

[0028] - the system further comprises a support, mounted on the pivot, by means of which the first platform is mounted on said pivot.

[0029] - the system further comprises at least one pin, inserted into at least one complementary orifice of the groove and housed in at least one cavity in the lower surface of the foot.

[0030] - the blade is made of organic matrix composite material, for example made by three-dimensional weaving.

[0031] - the dawn is an exit guide dawn.

[0032] The invention according to a second aspect further relates to a turbomachine, in particular an aircraft turbomachine, comprising at least one assembly according to the first aspect. The invention according to a third aspect further relates to a method of assembling an assembly according to the first aspect, comprising the following steps:

[0033] - the insertion of the foot into the groove by sliding; - the positioning of the movable jaw in the groove so that the first inclined plane of the movable jaw rests on a complementary inclined plane of the foot and the second inclined plane of the movable jaw rests on the inclined plane of the groove;

[0034] - the insertion of the fixing means into the holes of the movable jaw and the pivot; and,

[0035] - tightening the fixing means so that the foot is held tight between the inclined plane of the groove, the bottom of the groove and the first inclined plane of the movable jaw.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: Figure 1 is a perspective view of an assembly comprising a blade and a blade holding system according to an embodiment of the prior art; Figure 2a is a schematic representation of a blade holding system according to a first embodiment of the prior art; Figure 2b is a schematic representation of a blade holding system according to a second embodiment of the prior art; Figure 3 is a perspective view of an assembly comprising a blade and a blade holding system according to an embodiment of the invention; Figure 4 is a perspective and sectional view of an assembly comprising a blade and a blade holding system according to an embodiment of the invention;Figure 5 is a sectional view of an assembly comprising a blade and a blade holding system according to one embodiment of the invention; and, Figure 6 is a step diagram of a method of assembling an assembly comprising a blade and a blade holding system according to one embodiment of the invention.;

[0038] DESCRIPTION OF THE EMBODIMENTS With reference to Figure 3, Figure 4 and Figure 5, we will now describe an embodiment of an assembly 101 comprising a blade 103 and a system 105 for holding the blade 103, for an aircraft turbomachine (not shown). The blade 103 extends longitudinally along an axis A and comprises a blade 109 and a root 111. The axis A is orthogonal to an axis X of longitudinal extent of the turbomachine around which mobile blades of the turbomachine rotate. The blade 103 is therefore mounted in the turbomachine, typically among other identical blades which belong to a row of so-called fixed blades.

[0039] This is a so-called fixed blade in the sense that it is not rotatable about the longitudinal axis of the turbomachine in which it is mounted. However, as will become more clear in the following, the blade 103 is rotatable about the axis A and can be said to have variable pitch, that is to say that its orientation relative to the flow flowing in the turbomachine can be modified.

[0040] It may thus be, by way of non-limiting example, a blade called an outlet guide vane or OGV (from the English “Outlet Guide Vane”) belonging to a row of OGVs whose function is to straighten a flow coming from a propeller of an unducted turbomachine or from a fan of a ducted turbomachine.

[0041] In a particular embodiment, the blade 103 is made of an organic matrix composite material. It may have been made, for example, by laminating two-dimensional fiber reinforcements, then densified with resin, or by three-dimensional weaving of a single preform which is then densified.

[0042] Advantageously, this type of material allows a significant weight gain while retaining mechanical properties equivalent to those of other heavier materials, or an improvement in mechanical properties for an equivalent weight or even a combination of the two advantages.

[0043] In the assembly 101, the system 105 for holding the blade 103 comprises a pivot 113 which is configured to rotate along the axis A. Thus, in the example shown, the pivot 113 cooperates with ball bearings 114 which allow it to rotate along the axis A. In other embodiments, it could be rollers or any other means allowing the rotation of the pivot 113. In the non-limiting example shown, the pivot 113 is a single part, that is to say that it is not an assembly of several separate parts. In addition, the pivot 113 comprises a cylindrical lower part 113a (hollow in this example), and an upper part 113b which has a substantially plate-like shape which comprises a groove 113ba in which the foot 111 is housed.

[0044] The system 105 further comprises 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 “mobile” insofar as it can be moved independently of the pivot 113 and the foot 111.

[0045] Furthermore, the groove 113ba, the foot 111 and the movable jaw 117 together form a dovetail assembly in which the foot 111 is held clamped 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.

[0046] In other words, the root 111 is connected 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 supported on three complementary faces of the root 111 when the assembly 101 is assembled so that the root 111 is clamped in the system 105. Advantageously, this arrangement prevents the loss of the blade 103 once the assembly of the assembly 101 has been carried out.

[0047] Furthermore, thanks to this arrangement also, the forces undergone by the blade 103, in particular at the level of its root 111, are diffused to the rest of the structure, in particular via the bearings, which avoids their local concentration and the associated risks.

[0048] 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 resting on an inclined plane 113bac complementary to the groove 113ba. In addition, the fixing means 119 are screws 119, oriented parallel to the axis A, and inserted into aligned orifices 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.

[0049] Thus, the adjustment of the clamping level of the movable jaw 117 by the screws 119, made possible by the presence of the clearance j, makes it possible to determine the intensity of the pressure exerted on the complementary inclined planes of the movable jaw 117 and contribute to clamping the foot 111 in the groove 113ba in fine.

[0050] Advantageously, the orientation of the fixing 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.

[0051] The terms "lower" and "upper" are defined relative to the engine axis (i.e. the X axis of rotation of the moving blades of the turbomachine mentioned above). Thus, the lower parts mentioned in the following are those closest (radially) to the X axis while the upper parts mentioned in this are those furthest (radially) from the X axis.

[0052] In the example shown, five screws 119 are equally distributed along the longitudinal extent of the movable jaw 117. Generally, a person skilled in the art will know how 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).

[0053] 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, to the extent that the root is rectilinear, the movable jaw could be positioned on the other side.

[0054] Furthermore, the system 105 also comprises at least one platform 125 which is mounted on the pivot 113 and the upper face of which is intended to be in contact with a flow F (typically an air flow) which flows around the blade 109 during use of the aircraft turbomachine. 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.

[0055] Generally speaking, 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 stream over their surface while limiting their mass (for example via hollow areas within them).

[0056] Advantageously, the use of several platforms facilitates the assembly of the assembly 101 and the person skilled in the art will know how to adapt their number, greater than or equal to 1, to the specific geometry of an assembly used.

[0057] In the non-limiting example still shown, the system 105 further comprises a support 127, mounted on the pivot 113, and by means of which the first platform 125a is mounted on the pivot 113. In particular, in this example, the support 127 has the shape of a bracket, a first arm of which is fixed to the pivot 113 (for example by screws not shown) and the other arm is configured to allow the fixing of the first platform and comprises orifices adapted for this purpose.

[0058] Furthermore, as can be seen in Figure 4 and Figure 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. 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 to the pivot 113. In the example shown, as can be seen in Figure 3, the upper part 113a on the pivot 113 even has a projection in which one of the holes 130 is located.

[0059] In the non-limiting example finally 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 root 111. In particular, a plurality of pins 129 are distributed along the longitudinal extent of the groove 113ba. Advantageously, these pins allow optimal axial positioning of the blade 103 during assembly of the assembly 101. Advantageously, the assembly 101 according to the invention makes it possible to obtain an aerodynamic connection for a fixed blade which results in a reduction in the stress on its critical zones and good mechanical strength, while reducing the mass of the assembly.

[0060] Furthermore, the person skilled in the art will know how to adapt the shape of the different parts (such as for example the radius of curvature of the platforms 125) to avoid the concentration of stresses in a given area.

[0061] In addition, a person skilled in the art will be able to adapt the contact surface between the root 111 and the various elements of the system 105 to optimize the distribution of the forces undergone by the blade 103 during its use, for example by increasing the embedding height of the root 111 in the system 105.

[0062] Finally, in other embodiments (not shown), the shape of the foot 111 could have tapered faces, or double tapered faces, with the aim of optimizing the transmission of forces, limiting the risks of the foot slipping, and making the fixing means (described later) work in shear.

[0063] With reference to Figure 6, we will now describe an embodiment of a method 601 for assembling the assembly 101 according to the invention.

[0064] A first step 603 consists of inserting the foot 111 into the groove 113ba by sliding. The foot 111 slides in the groove 113ba along their longitudinal extent until it is fully positioned in the groove. Furthermore, when inserting the foot 111 into the groove 113ba, the pins 129 can be inserted into the cavity in the lower surface of the foot 111.

[0065] To facilitate the next step, the shape of the cavity may 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.

[0066] 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 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. The next step 607 consists of inserting the screws 119 into the holes 121 of the movable jaw 117 and the pivot 113.

[0067] 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.

[0068] Thus, as this method shows, the assembly (or disassembly) of the assembly 101 is simple and can be, for example, 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. 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),and in that 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)., 2. Assembly (101) according to claim 1, 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).

3. Assembly (101) according to claim 1 or claim 2, in which a clearance (j) is provided between the small base of the trapezium and the bottom (113ba b) of the groove (113ba).

4. Assembly (101) according to any one of the preceding claims, wherein said movable jaw (117) is positioned in the groove (113ba) on the extrados side of the blade (103).

5. Assembly (101) according to any one of the preceding claims, in which the pivot (113) is a single piece comprising a cylindrical lower part (113a), and an upper part (113b) having substantially the shape of a plate and comprising the groove (113ba).

6. 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).

7. Assembly (101) according to claim 6, 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).

8. Assembly (101) according to claim 7, 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).

9. 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).

10. 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.

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

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

13. Method (501) of assembling an assembly (101) according to any one of claims 1 to 5, comprising the following steps: - the insertion (603) of the foot (111) into the groove (113ba) by sliding; - the positioning (605) of 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); - the insertion (607) of 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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