ASSEMBLY INCLUDING A BLADE AND A BLADE RETAINING SYSTEM
The blade retention system with a pivot and movable jaw dovetail joint addresses stress concentration issues in composite blades, enhancing mechanical strength and reducing mass while improving durability.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2023-09-22
- Publication Date
- 2026-05-22
AI Technical Summary
The existing fastening systems for composite material blades in turbomachinery experience significant stress concentrations, leading to reduced lifespan due to antisymmetric loading and localized stress concentrations, particularly in areas like the radius of flanges and fixings, which are prone to damage modes such as opening and buckling.
A blade retention system featuring a pivot with a groove and a movable jaw forming a dovetail joint, secured by fastening means passing through the movable jaw, foot, and pivot, distributing stress evenly and preventing local concentration.
The solution effectively diffuses stress, enhances mechanical strength, reduces mass, and improves the lifespan of composite blades by evenly distributing forces and minimizing wear on fastening means.
Smart Images
Figure 00000011_0000 
Figure 00000012_0000 
Figure 00000012_0001
Abstract
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 blade architecture for aircraft turbomachinery. It relates in particular to an assembly comprising a blade and a blade retention system. Previous technique
[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 around the axis of the turbomachine. As with 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 retention system are likely to reduce the part's lifespan 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, said pivot comprising a groove in which the foot is housed,
[0019] said assembly being characterized in that the system further comprises a movable jaw, positioned on one side of the foot, 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 an inclined plane of said movable jaw, by means of fastening means passing through said movable jaw, said foot and said pivot.
[0020] The assembly according to the invention may comprise one or more of the following features, taken individually or in combination with each other:
[0021] - the fastening means are screws, passing through complementary aligned holes said movable jaw, said foot and said pivot, said screws being tightened by additional nuts.
[0022] - the fastening means extend parallel to a transverse direction at the longitudinal extent of the foot.
[0023] - the movable jaw and the pivot fit into each other, according to the direction transverse to the longitudinal extent of the foot and are linked to each other by a sliding joint.
[0024] - the assembly, formed by the pivot and the movable jaw embedded one inside the other, exhibits symmetry along a plane parallel to the longitudinal extent of the throat and passing through the axis.
[0025] - the movable jaw is positioned on the extrados side of the blade.
[0026] - the number of fastening means is between 3 and 8, preferably between 4 and 6, said means of fixation being equally distributed along the longitudinal extent of the foot.
[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] 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.
[0029] 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:
[0030] - the positioning of the foot in the throat;
[0031] - the fitting of the movable jaw into the pivot by sliding said movable jaw in said pivot along a direction transverse to the longitudinal extent of the foot;
[0032] - the positioning of the fastening means at the level of the movable jaw, the foot and the pivot; and,
[0033] - tightening the fastening means so that the foot is held tightly between the inclined plane of the throat, the bottom of said throat and the inclined plane of the movable jaw. Brief description of the drawings
[0034] 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:
[0035] [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;
[0036] [Fig.2a] is a schematic representation of a blade support system according to a first embodiment of the prior art;
[0037] [Fig.2b] is a schematic representation of a blade support system according to a second embodiment of the prior art;
[0038] [Fig.3] is a perspective view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;
[0039] [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; and,
[0040] [Fig.5] 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 implementation methods
[0041] With reference to [Fig.3] and [Fig.4] 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) according to the invention.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] By way of further example, the blade 103 may be 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.
[0046] Advantageously, this type of material allows 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.
[0047] 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 115 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.
[0048] 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 cylindrical lower portion (which is hollow in this example), and an upper portion which is substantially plate-shaped and includes a groove 113a in which the foot 111 is housed.
[0049] 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.
[0050] The system 105 further includes a movable jaw 117 which is positioned on one side of the foot 111 (relative to the longitudinal extent of said foot 111). The movable jaw 117 is a separate part from the foot 111 and the pivot 113. It is said to be "movable" insofar as it can be moved independently of the pivot 113 and the foot 111.
[0051] In the non-limiting example shown, the movable jaw 117 is positioned on the extrados side of the blade 103 (and by extension of the foot 111 as well). Generally, insofar as the foot 111 is straight, the movable jaw 117 can be positioned on either side.
[0052] In addition, the groove 113a, 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 113aa of the groove 113a, the bottom 113ab of the groove 113ba and an inclined plane 117a of the movable jaw 117.
[0053] The foot 111 is held tightly in the groove 113a by means of fastening means 119 which pass through the movable jaw 117, the foot 111 and the pivot 113.
[0054] 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.
[0055] Advantageously, this arrangement prevents the loss of the blade 103 once the assembly of the set 101 has been completed.
[0056] Moreover, thanks to this arrangement also, the stresses suffered by the blade 103, in particular at the level of its foot 111, are diffused to the rest of the structure, in particular via the bearings, which avoids their local concentration and the associated risks.
[0057] In the non-limiting example shown, the fastening means 119 are screws, which pass through complementary aligned holes 121 in the movable jaw 117, the foot 111 and the pivot 113. These screws 119 are tightened by complementary nuts 123.
[0058] More specifically, the body of each screw 119 passes through the movable jaw 117, the foot 111 and the pivot 113, and emerges at one side of the groove 113a where the emerging part of each screw 119 is tightened by a complementary nut 123.
[0059] Furthermore, the number of screws 119 used is typically between 3 and 8, and preferably between 4 and 6 (5 in the example shown). These screws 119 are equally spaced along the longitudinal extent of the foot 111.
[0060] Generally, a person skilled in the art will be able to adapt the number and spatial distribution of the means of fixing 119 of the movable jaw 117 according to a desired tightening (and distribution of this tightening).
[0061] Finally, the fixing means 119, whether screws or not, extend parallel to a transverse direction (i.e. orthogonal) to the longitudinal extent of the foot 111.
[0062] Advantageously, due to the inclination of the inclined planes (117a and 113aa) which clamp the foot 111, the fastening means 119 are very little stressed in shear and are therefore protected from the associated risks of wear.
[0063] In general, the adjustment and distribution of the clamping level of the movable jaw 117, the foot 111 and the pivot 113, by the screws 119, makes it possible to determine the intensity of the force which is exerted on said foot 111 and contributes, on the one hand, to its retention in the groove 113a and, on the other hand, to the redistribution of the forces suffered by the blade 103 as a whole.
[0064] In the non-limiting example also shown, the movable jaw 117 and the pivot 113 fit into each other in a direction transverse to the longitudinal extent of the foot 111 and are connected to each other by a sliding joint. In other words, the movable jaw 117 can only slide in one direction (the direction transverse to the longitudinal extent of the foot 111) to fit into the pivot 113. Furthermore, the direction in question is parallel to that of the extent of the means of fixation 119.
[0065] Indeed, as can be seen more particularly in [Fig.3], the respective shapes of the movable jaw 117 and the pivot 113 are complementary and fit together perfectly.
[0066] Moreover, the assembly formed by the pivot 113 and the movable jaw 117 embedded in each other, exhibits a symmetry along a plane P parallel to the longitudinal extent of the groove 113a and passing through the axis A.
[0067] In other words, the movable jaw 117 has the shape of a "missing" part of the pivot 113 so that their embedding produces a part whose shape (which allows the dovetail assembly with the foot 111) is symmetrical (according to the plane P).
[0068] In this case, the movable jaw 117 has the same shape, in its upper part, as the side of the groove 113a to which belongs the inclined plane 113aa which allows the clamping of the foot 111. Whereas, in its lower part, the movable jaw 117 has substantially an inverted T shape which fits into a complementary cavity of the pivot 113 so that the whole of the two embedded parts has no protruding part and only the screw heads 119 protrude from the whole when the assembly 101 is assembled.
[0069] Finally, in a particular embodiment not shown, the system 105 may also include at least one platform 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.
[0070] 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).
[0071] 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.
[0072] Advantageously also, 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.
[0073] In addition, a person skilled in the art will know how to adapt the shape of the different parts to avoid the concentration of stresses in a given area.
[0074] Furthermore, 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 stresses experienced by the blade 103 during its use, for example by increasing the embedment height of the foot 111 in the system 105 (i.e. in the groove 113a in particular).
[0075] With reference to [Fig.5], we will now describe an implementation method of a method 501 for assembling an assembly 101 such as that shown in [Fig.3].
[0076] The first step 503 consists of positioning the foot 111 in the groove 113a. In particular, the base of the foot 111 (i.e. its lower extremity) is positioned in the bottom 113ab of the groove 113a, the width of which is complementary to that of the foot 111.
[0077] The next step 505 consists of the fitting of the movable jaw 117 into the pivot 113 by sliding the movable jaw 117 into said pivot 113 in a direction transverse to the longitudinal extent of the foot 111. As mentioned above, the shapes of the movable jaw 117 and the pivot 113 are complementary and configured so as to allow the translation of the movable jaw 117 (for its fitting) only in this direction until the inclined plane 117a of the movable jaw 117 is in contact with the foot 111.
[0078] The next step 507 then consists of positioning the fastening means 119 at the level of the movable jaw 117, the foot 111 and the pivot 113. In the example shown in [Fig.3], this involves inserting the screws 119 and positioning the nuts 123 on these screws, but in other embodiments of the invention, it could involve other fastening means allowing the three parts (movable jaw 117, foot 111 and pivot 113) to be clamped together.
[0079] Finally, step 509 consists of tightening the fastening means 119 (in this case tightening the nuts 123 on the screws 119) so that the foot 111 is held tight between the inclined plane 113aa of the groove 113a, the bottom 113ab of the groove 113a and the inclined plane 117a of the movable jaw 117.
[0080] Advantageously, the assembly according to the invention can therefore be assembled very simply, for example in a workshop prior to its mounting on a turbomachine. Maintenance of the blade is thus also simplified by the easy disassembly of the assembly by the reverse of the process described herein.
Claims
Demands
1. An assembly (101) comprising a blade (103) and a blade (105) retention system for an aircraft turbomachine, said blade (103) extending longitudinally about an axis (A) and comprising a blade (109) and a foot (111), and said system (105) comprising a pivot (113) configured to rotate about the axis (A), said pivot (113) having a groove (113a) in which the foot (111) is housed, said assembly (101) being characterized in that the system (105) further comprises a movable jaw (117) positioned on one side of the foot (111), said groove (113a), said foot (111), and said movable jaw (117) together forming a dovetail joint in which said foot (111) is held tightly between an inclined plane (113aa) of said groove (113a), the bottom (113ab) of said groove (113a) and an inclined plane (117a) of said movable jaw (117), by means of fastening means (119) passing through said movable jaw (117),said foot (111) and said pivot (113), and in that the movable jaw (117) and the pivot (113) fit into each other, in the direction transverse to the longitudinal extent of the foot (111) and are linked to each other by a sliding joint.
2. Assembly (101) according to claim 1, wherein the fastening means (119, 123) are screws (119), passing through complementary aligned holes (121) in said movable jaw (117), said foot (111) and said pivot (113), said screws (119) being tightened by complementary nuts (123).
3. Assembly (101) according to claim 1 or claim 2, wherein the fastening means (119, 123) extend parallel in a direction transverse to the longitudinal extent of the foot (111).
4. Assembly (101) according to claim 1, wherein the assembly, formed by the pivot (113) and the movable jaw (117) embedded in each other, has a symmetry about a plane (P) parallel to the longitudinal extent of the groove (113a) and passing through the axis (A).
5. Assembly (101) according to any one of the preceding claims, wherein the movable jaw (117) is positioned on the extrados side of the blade (103).
6. Assembly (101) according to any one of the preceding claims, wherein the number of fastening means (119) is between 3 and 8, preferably between 4 and 6, said means of fixation (119) being equally distributed along the longitudinal extent of the foot (111).
7. Assembly (101) according to any one of the preceding claims, wherein the system (105) further comprises at least one platform, 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. Turbomachine, in particular aircraft, comprising at least one assembly (101) according to any one of the preceding claims.
9. A method (501) for assembling an assembly (101) according to any one of claims 1 to 6, comprising the following steps: - positioning (503) the foot (111) in the groove (113a); - embedding (505) the movable jaw (117) in the pivot (113) by sliding said movable jaw (117) in said pivot (113) in a direction transverse to the longitudinal extent of the foot (111); - positioning (507) the fastening means (119, 123) at the level of the movable jaw (117), the foot (111) and the pivot (113); and, - the tightening (509) of the fastening means (119, 123) so that the foot (111) is held tight between the inclined plane (113aa) of the groove (113a), the bottom (113ab) of said groove (113a) and the inclined plane (117a) of the movable jaw (117).