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 comprises a blade (109) and a foot (111). The system (105) comprises a pivot (113) configured to rotate about the axis (A) and at least one platform (115) mounted on the pivot (113). The pivot (113) and the at least one platform (115) together form a cavity (117) having a shape complementary to the shape of the foot (111), and in which the foot (111) is clamped and retained by means of fastening means (121, 125). Figure for the abstract: Fig. 3

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 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 Figure 2 in cross-sectional views perpendicular to the axis of the turbomachine of blade retention systems 15 11.

[0010] The left part of Figure 2 thus shows a clamping attachment (called a "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] The right part of figure 2 shows a tangential attachment in which the composite part 17 is represented in light grey and the metal fastening system 19 and 21 is represented 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,

[0018] said system comprising a pivot configured to perform a rotation about the axis and at least one platform mounted on the pivot and whose upper face is intended to be in contact with a flow flowing around the blade,

[0019] said assembly being characterized in that the pivot and at least one platform together form a cavity, having a shape complementary to the shape of the foot, and in which said foot is clamped and held by means of fastening.

[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] - at least one platform and the pivot comprise first aligned orifices, parallel to the axis, said first orifices being complementary to first means among said means of fixing, preferably screws, used to fix said pivot and said at least one platform together.

[0022] - at least one platform and the foot have second through holes aligned, perpendicular to the axis, said second orifices being complementary to second means among said means of fixing used to fix said foot and said at least one platform together.

[0023] - the foot has substantially the shape of a rectangular parallelepiped, and the first the means of fixation and the second means of fixation are distributed according to the direction of the length of the foot.

[0024] - the first fastening means and the second fastening means are alternated according to the direction of the length of the foot.

[0025] - the first fastening means are equally distributed along the length direction of the foot and the second means of fixation are equally distributed according to the direction of the length of the foot.

[0026] - the second means of fastening comprise threaded rods, passing through the second holes, and nuts, tightening the said threaded rods, on either side of the said second holes.

[0027] - the pivot is a single piece comprising a cylindrical lower part, and a upper part having substantially a platinum shape comprising a groove in which a base of the foot is housed.

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

[0030] - dawn is a guiding exit dawn.

[0031] 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.

[0032] The invention according to a third aspect relates finally to a method of assembling an assembly according to the first aspect, comprising the following steps:

[0033] - the insertion of the threaded rods into the second holes of a platform among the first platform and second platform;

[0034] - positioning the foot in contact with the platform by inserting the threaded rods in the second orifices of said foot;

[0035] - the positioning of another platform, among the first platform and the second platform, in contact with the foot, by inserting the threaded rods into the second holes of said other platform;

[0036] - the positioning and tightening of the nuts on the threaded rods so as to fix the first platform, the foot and the second platform together;

[0037] - the positioning of the assembly formed by the first platform, the foot and the a second platform on the upper part of the pivot so that the base of the foot is housed in the groove; and,

[0038] - the insertion and tightening of the screws in the first holes so as to fix the pivot and the first platform and the second platform together.

[0039] Furthermore, in a particular embodiment of the method, during the positioning and tightening of the nuts step, a marble is used, before tightening the nuts, to align the lower surfaces of the first platform and the second platform. Brief description of the drawings

[0040] 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:

[0041] [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;

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

[0043] [Fig.2b] is a schematic representation of a blade support system according to a second embodiment of the prior art;

[0044] [Fig. 3] is a perspective view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;

[0045] [Fig.4a] is a cross-sectional view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;

[0046] [Fig.4b] is a cross-sectional view of an assembly comprising a blade and a blade retention system according to an embodiment of the invention;

[0047] [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; and,

[0048] [Fig.6] is a schematic representation of the assembly steps of an assembly comprising a blade and a blade retention system according to an embodiment of the invention. Description of the implementation methods

[0049] With reference to [Fig.3], [Fig.4a] and [Fig.4b], 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).

[0050] Figures 4a and 4b show two cross-sectional views of the same assembly along two parallel but offset cutting planes. The elements included in the assembly 101 described below are also visible in [Fig. 6], which illustrates certain steps in an implementation of a method for assembling said assembly 101.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] In the assembly 101, the blade retaining system 105 includes a pivot 113 which is configured to perform a rotation about the axis A. Thus, by way of example, the pivot 113 can cooperate with bearings (not shown) which allow its rotation about the axis A or with rollers or any other means allowing its rotation.

[0057] 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 part 113a, and an upper part 113b which is substantially plate-shaped and includes a groove 113ba in which the base 11la of the foot 111 is housed.

[0058] The term "base" here refers to the lower surface of foot 111. 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.

[0059] Furthermore, the foot 111a is substantially rectangular in shape, and the groove 113ba extends longitudinally along the length of the foot 111 (i.e., along the length of the parallelepiped). Generally, the foot 111 can have any equivalent elongated shape to facilitate the fabrication of the blade foot and to ensure good support and force transmission between the blade 109 and the pivot 113, regardless of the operating conditions.

[0060] The system 105 also includes at least one platform 115 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.

[0061] The platform(s) used therefore 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).

[0062] In the non-limiting example also shown, the system 105 includes a first platform 115a which is positioned on the extrados side of the blade 103 and a second platform 115b which is positioned on the intrados side of the blade 103.

[0063] 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 a set used.

[0064] Furthermore, the platforms 115a and 115b on the one hand, and the pivot 113 on the other hand, together form a cavity 117, which has a shape complementary to the shape of the foot 111, and in which the foot 111 is clamped and held by means of fastening (described below).

[0065] In particular, in this example, the groove 113ba and internal cavities of the platforms 115a and 115b together form the cavity 117 which has substantially a parallelepiped shape, identical to that of the foot 111, so as to enclose the foot 111 when the assembly 101 is assembled.

[0066] 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.

[0067] Furthermore, a person skilled in the art will know how to adapt the contact surface between the platforms 115 and the foot 111 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 (i.e. in the platforms 115 and the pivot 113).

[0068] In the example shown, the platforms 115a and 115b and the pivot 113 have holes 119 aligned and parallel to the axis A. The holes 119 are complementary to fastening means 121, in this case screws, used to fix the pivot 113 and the platforms 115a and 115b together.

[0069] In addition, in the example also shown, five screws 121 with a diameter of 12.7 millimeters are distributed in each platform 115 along the direction of the length of the foot 111. The screws 121 are buried in the holes 119 so that they do not protrude from the top face of the platforms 115a and 115b so as not to obstruct the flow of a stream in this area.

[0070] The platforms 115a and 115b and the foot 111 also have aligned through holes 123 which are perpendicular to the axis A. In the described embodiment, the axis of the holes 123 is also perpendicular to the length of the foot 111.

[0071] In addition, the orifices 123 are complementary to the fastening means 125 used to fix the foot 111 and the platforms 115a and 115b together.

[0072] As can be seen in particular in [Fig.4a], the orifices 123 which pass through both the foot 111 and the platforms 115a and 115b open at the level of internal hollow areas of the platforms 115a and 115b.

[0073] Furthermore, in the non-limiting example shown, four fastening means 125 are distributed along the length of the foot 111. More specifically, the fastening means 125 comprise threaded rods 125a (also called "tie rods" in the vocabulary of the design and use of blades according to the invention) which pass through the holes 125 and nuts 125b which clamp the threaded rods 125a on either side of the holes 123. The threaded rods 125a and the nuts 125b are equally distributed along the length of the foot 111.

[0074] As can be seen more particularly in [Fig.3] and [Fig.6], the fastening means 121 (and consequently the orifices 119) and the fastening means 125 (and consequently the orifices 123) are alternated along the direction of the length of the foot 111.

[0075] Finally, in the non-limiting example shown again, the assembly 101 also includes a nut 127 screwed onto a complementary thread located in the lower part 113a of the pivot 113. The nut 127 retains the assembly on the motor and is not described in further detail here as it is not part of the invention.

[0076] Advantageously, the invention in general and this arrangement in particular makes it possible to maintain the blade 103 with a system 105 which is compact and lightweight.

[0077] 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, better mechanical strength, and a significant reduction in mass.

[0078] With reference to [Fig.5] and [Fig.6], we will now describe an implementation method of a method 501 for assembling the assembly 101 as illustrated in [Fig.3] and Figure 4.

[0079] The first step 503 consists of inserting the threaded rods 125a into the second holes 123 of a platform 115 between the first platform 115a and the second platform 115b. In the example shown, it is the platform 115a and the threaded rods 125a therefore emerge at the level of a hollow area of ​​the platform 115a.

[0080] The next step 505 consists of positioning the foot 111 (and therefore the blade 103) in contact with the platform 115a by inserting the threaded rods 125a into the holes 123 of the foot 111.

[0081] The next step 507 consists of positioning another platform 115, from among the first platform 115a and the second platform 115b, in contact with the foot 111, by inserting the threaded rods 125a into the holes 123 of this other platform 115a or 115b. In the example, it is the platform 115b that comes into contact with the foot 111 and the other platform 115a so that the two platforms 115a and 115b enclose the foot 111 and the threaded rods 125a open into internal hollow areas of the two platforms 115a and 115b.

[0082] The next step 509 consists of positioning and tightening the nuts 125b on the threaded rods 125a so as to fix the first platform 115a, the foot 111, and the second platform 125b together. Those skilled in the art will know how to adjust the tightening of the nuts 125b to achieve the desired level of pressure on the foot 111 held by the platforms 115a and 115b.

[0083] Furthermore, in a particular embodiment, during this step, a marble slab is used, before tightening the nuts 125b, to align the lower surfaces of the first platform 115a and second platform 115b (as can be seen in the lower part of [Fig.6]).

[0084] The next step 511 consists of positioning the assembly formed by the first platform 115a, the foot 111 and the second platform 115b (i.e. the assembly that was clamped in the previous step) on the upper part of the pivot 113b so that the base of the foot 11la is housed in the groove 113ba. The foot 111 is thus clamped by the platforms 115a and 115b and the pivot 113, with the additional presence of a clearance between the lower part of the base 11la and the groove 113ba (i.e. there is no contact between these two parts) to avoid excessive static loads when tightening the screws 121 in the pivot 113.

[0085] Finally, step 513 consists of inserting and tightening the screws 121 into the holes 119 so as to fix the pivot 113, the first platform 115a and the second platform 115b together.

[0086] The process described here is a process for assembling the assembly 101; however, the steps described can be applied to a disassembly by reversing their order and replacing a tightening with a loosening, a positioning with a withdrawal, and an insertion with an extraction.

[0087] Advantageously, the assembly according to the invention thus has simplified assembly and disassembly. In particular, it is possible to assemble the assembly in the workshop before mounting it on a turbomachine. Similarly, maintenance of the blade is simplified thanks to its easy disassembly.

Claims

Demands

1. Assembly (101) comprising a blade (103) and a blade (103) retention system (105), for an aircraft turbomachine, said blade (103) extending longitudinally along an axis (A) and comprising a blade (109) and a foot (111), said system (105) comprising a pivot (113) configured to perform rotation about the axis (A) and at least one platform (115) 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), said assembly being characterized in that the pivot (113) and the at least one platform (115) together form a cavity (117), having a shape complementary to the shape of the foot (111), and in which said foot (111) is clamped and retained by means of fastening means (121, 125), in that at least one platform (115) and the pivot (113) have first orifices (119) aligned parallel to the axis (A),said first holes (119) being complementary to first means (121) among said fastening means (121, 125), preferably screws (121), used to fix said pivot (113) and said at least one platform (115) together, and in that the at least one platform (115) and the foot (111) have second through holes (123) aligned, perpendicular to the axis (A), said second holes (123) being complementary to second means (125) among said fastening means (125, 121) used to fix said foot (111) and said at least one platform (115) together.

2. Assembly (101) according to claim 1, wherein the foot (111) has substantially a rectangular parallelepiped shape, and the first fixing means (121) and the second fixing means (125) are distributed along the direction of the length of the foot (111).

3. Assembly (101) according to claim 2, wherein the first fastening means (121) and the second fastening means (125) are alternated along the direction of the length of the foot (111).

4. Assembly (101) according to claim 3, wherein the first fastening means (121) are equally distributed along the direction of the length of the foot (111) and the second fastening means (121) are equally distributed along the direction of the length of the foot (111).

5. Assembly (101) according to any one of the preceding claims, wherein the second fastening means (125) comprise threaded rods (125a), passing through the second orifices (123), and nuts (125b), clamping said threaded rods (125a), on either side of said second orifices (123).

6. Assembly (101) according to any one of the preceding claims, wherein the pivot (113) is a single piece comprising a cylindrical lower part (113a), and an upper part (113b) having substantially a plate shape comprising a groove (113ba) in which a base (11la) of the foot (111) is housed.

7. Assembly (101) according to any one of the preceding claims, wherein a first platform (115a) is positioned on the extrados side of the blade (103) and a second platform (115b) is positioned on the intrados side of the blade (103).

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

9. Assembly (101) according to any one of the preceding claims, wherein the blade (103) is an output guide blade.

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

11. Method (501) of assembling an assembly (101) having at least the characteristics of claims 1 to 5 and 7, comprising the following steps: - the insertion (503) of the threaded rods (125a) into the second orifices (123) of a platform (115) between the first platform (115a) and the second platform (115b); - the positioning (505) of the foot (111) in contact with the platform (115) by inserting the threaded rods (125a) into the second orifices (123) of said foot (111); - the positioning (507) of another platform (115), between the first platform (115a) and the second platform (115b), in contact with the foot (111), by inserting the threaded rods (125a) into the second orifices (123) of said other platform (115);

12. - the positioning and tightening (509) of the nuts (125b), on the threaded rods (125a) so as to fix the first platform (115a), the foot (111) and the second platform (115b) together; - the positioning (511) of the assembly formed by the first platform (115a), the foot (111) and the second platform (115b) on the upper part of the pivot (113b) so that the base (11la) of the foot (111) is housed in the groove (113ba); and, - the insertion and tightening (513) of the screws (121) in the first holes (119) so as to fix the pivot (113) and the first platform (115a) and the second platform (115b) together. Method (501) of assembling an assembly (101) according to claim 11, wherein, during the positioning and tightening step (509) of the nuts (125b), a marble is used, before tightening the nuts (125b), to align the lower surfaces of the first platform (115a) and the second platform (115b).

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