EP2488725B1 - Turbine wheel having an axial retaining ring locking the blades in relation to a disc - Google Patents

Description

The invention relates generally to paddle wheels in gas turbines and more particularly to the axial retention of said blades relative to the axis of the wheel. The field of application of the invention is in particular that of aircraft gas turbines as well as that of industrial gas turbines.

A conventional turbine wheel has an axis of rotation and comprises a disc having a periphery and a lateral face, a plurality of blades mounted on the disc, each of the blades having a blade root and a first axially projecting hook, said first hook being oriented radially and defining a first groove which opens radially towards the axis of rotation of the turbine wheel, the disc comprising a series of second hooks axially projecting from its lateral face on the same side as the first hooks, each second hook being oriented radially and defining a second groove which opens radially towards the axis of rotation of the turbine wheel, an axial retaining ring comprising at least one stopper and intended to be arranged in the first grooves and in the second grooves to axially retain the blades relative to the disk.

Among the known turbine wheels, for example by the patent FR 2,729,709 , a cleat of the ring is locked in rotation between different parts of the turbine wheel in order to secure the assembly of the ring and the retention of the blades on the disk.

The object of the invention is to provide an alternative to known turbine wheel mounting structures.

This object is achieved thanks to the fact that in the type of turbine wheel mentioned above, the cleat is intended to be disposed between two adjacent blade feet so as to limit the azimuthal displacements of the rod.

The term "foot" means the entire blade disposed at the base of the blade for mounting the latter on the disk. It will be noted that subsequently the term "wheel" and "turbine wheel" will be used interchangeably to designate the same object. It is therefore understood that in mounted position, the azimuth displacement of the cleat is restricted by two adjacent blade feet. To do this the cleat can abut against one or the other of the two feet of blade. Therefore the azimuthal movement of the ring is limited.

The cleat is disposed in a space that extends between the two adjacent blade legs so that no particular machining is necessary, especially to provide space for housing the cleat. It is therefore possible to mount on the wheel a set of blades having identical feet. In addition, the blades can be all identical, mounting the wheel is facilitated. Indeed, the operator does not pay particular attention to the placement of a blade having a specific foot vis-à-vis the cleat.

Thus, the azimuthal movement of the rod is at most equal to the azimuthal length of the available space between two adjacent feet minus the azimuthal length of the cleat. In the case where the cleat extends over most of the azimuthal length, it is useful to provide a non-zero maximum azimuth displacement of the rod, in particular to facilitate assembly and to compensate for thermal expansion differentials. It should be noted that the first grooves are defined between the first hooks and the blade roots while the second grooves are defined between the second hooks and the disc. The ring moves azimutally in the first and second grooves.

Furthermore, it will be noted that the arrangement of the cleat between two blade roots advantageously makes it possible to dispense with a particular machining of said cleat, in particular to allow its insertion between the two blade roots. In addition, this arrangement between two blade roots makes it possible to place the cleat between any pair of blade roots. Thus, there is no preferential azimuthal position of the cleat vis-à-vis the disc and vis-à-vis the blade feet. Therefore, several azimuthal mounting positions of the rod are possible, which makes the rod versatile. Thus, unlike the devices of the state of the art, the turbine wheel according to the present invention is not limited to a single mounting position of the cleat, and therefore the rod, vis-à-vis the wheel of turbine.

Advantageously, the cleat is axially projecting from an axial face of the ring.

The term "axial face" of the ring means a face of the ring which is perpendicular to the axis of rotation of the turbine. In other words, an axial face of the ring is a face substantially parallel to the lateral face of the disc. Preferably, in the mounted position, the stopper projects in an axial direction opposite to the lateral face of the disc.

Advantageously, the cleat is disposed on an inner annular portion of the ring.

By considering the ring as a ring having an inner peripheral edge and an outer peripheral edge and an intermediate geometric line extending parallel between the inner and outer peripheral edges, the inner annular portion of the ring is determined to be a portion of the bounded ring. by the inner peripheral edge and the intermediate line of the ring, while the outer annular portion of the ring is defined as being a portion of the ring delimited by the outer peripheral edge and the intermediate line of the ring. It is therefore understood that the cleat extends radially on an axial face of the ring, between the inner peripheral edge and the intermediate line of the ring.

Preferably, the cleat is intended to be disposed between the first hooks of two feet of adjacent blade.

Thus, the cleat is able to cooperate with said first hooks of the blade roots in order to limit the azimuthal movement of the ring. It is therefore clear that the azimuthal space in which the cleat extends is delimited azimuthally by the first hooks. Thus, the first hooks have a stop zone for the cleat.

Advantageously, the cleat is intended to be arranged in line with one of the second hooks.

It is therefore understood that one of the second hooks is disposed in the azimuthal space available between two adjacent blade feet. This second hook and the cleat are arranged substantially on the same wheel radius. The second hook is radially further from the axis of rotation of the turbine wheel than the cleat. The second hook is oriented towards the cleat.

Preferably, the minimum distance between the outer peripheral edge of the ring and the stopper is greater than the depth of one of the second grooves.

Thus, if the cleat is in line with a second hook, it is ensured that the outer edge of the ring is adapted to be in contact with the bottom of the second groove, for example under the effect of centrifugal forces. during rotation of the turbine wheel, without cleat is likely to cooperate with the second hook. Therefore radial mechanical stresses on the cleat are avoided which are not used to limit the azimuthal movement of the ring. This improves the life of the rod. In addition, it also limits the mechanical bending stresses in the second hook disposed above the cleat, avoiding a tab contact / second hook. Therefore, the cooperation of the ring is identical with each of the second grooves of the disk, regardless of the presence of the cleat.

Advantageously, the first hook of each of the blades is radially projecting from the foot of said blades.

This first hook structure makes it easy to manufacture first hooks whose first grooves are arranged in the azimuthal continuity of the second grooves of the disc. Thus, when the blades are mounted on the disc, the first hooks axially protrude from the plane defined by the side face of the disc.

Preferably, the foot of each blade is engaged in a housing opening at the periphery of the disk, the housing being separated by teeth, each second hook projecting from one of the teeth.

At the periphery of the disc, it is understood that the teeth alternate with the blade roots, and that the first hooks alternate with the second hooks. Thus, the circumferential groove receiving the ring consists of an alternating succession of first and second grooves. It should be noted that the circumferential groove is not necessarily continuous and may have gaps between the first grooves and the second grooves. Such a groove structure allows to evenly distribute the blade retaining forces over the entire periphery of the disk. This also makes it possible to better maintain the ring and thus to avoid dynamic effects harmful to the structure such as vibrations.

Advantageously, the cleat has contact faces adapted to make a plane contact with bearing faces of the two blade roots which limit the azimuthal movement of the ring.

By providing contact faces on the cleat and bearing faces on the feet, an interface is created between the cleat and the feet improving cooperation between these two elements. Thus, when the cleat cooperates with a foot, the cleat can hardly slip and disengage from the azimuthal lock made by the foot.

Preferably, the ring has a slot diametrically opposite the cleat.

The slot of the ring facilitates the mounting of the latter in the first and second grooves. The position of the slot diametrically opposite the cleat improves the functional reliability of the ring. Indeed, if a rupture of the latter should occur, this break would most likely be located at the cleat. The broken ridge would then form two half-rods of substantially equivalent lengths that could not disengage from the first and second hooks. Thus, the presence of a single cleat disposed opposite the slot makes it possible to concentrate the mechanical stresses undergone by the rod in the vicinity of said cleat opposite the slot and, consequently, to improve the functional reliability. of the rush. In addition, the slot being disposed diametrically opposite the cleat, the ring is arranged in the first and second grooves by varying the radial flexibility of the ring and arranging from the start the cleat between two blade roots. Thus, since the assembly, the azimuthal movements of the ring are limited.

Advantageously, the ring has the general shape of a ring having an axis, the center of gravity of said ring being located on said axis.

A balanced ring has the advantage of not influencing the balance of the rotating assembly constituted by the disk and the blades. Thus, it is not necessary to provide a particular machining on the turbine wheel to compensate for an imbalance that would be due to a nonuniform distribution of masses. Therefore, it is possible to mount the rod in all possible azimuthal positions without disturbing the homogeneous azimuth distribution of the masses, so that the assembly of the turbine wheel is facilitated.

The present invention also relates to a turbomachine comprising a turbine wheel according to the invention.

• la figure 1 représente une portion de roue de turbine selon l'invention,
• la figure 2, représente le montage du jonc de la roue de turbine selon l'invention vu selon le plan de section II de la figure 1,
• la figure 3, représente le montage du jonc de la roue de turbine selon l'invention vu selon le plan de section III de la figure 1,
• la figure 4 représente le jonc de la figure 1 dans son ensemble, et
• la figure 5 représente une turbomachine d'hélicoptère équipée d'une roue de turbine selon l'invention.

The invention and its advantages will be better understood on reading the detailed description given below of an embodiment given to as a non-limitative example. This description refers to the appended figures, in which:

• the figure 1 represents a portion of turbine wheel according to the invention,
• the figure 2 , represents the assembly of the ring of the turbine wheel according to the invention seen according to the sectional plane II of the figure 1 ,
• the figure 3 , represents the assembly of the ring of the turbine wheel according to the invention seen according to the section plane III of the figure 1 ,
• the figure 4 represents the rush of the figure 1 as a whole, and
• the figure 5 represents a helicopter turbine engine equipped with a turbine wheel according to the invention.

The figure 1 represents a portion of a turbine wheel 10 with a rotation axis X. The turbine wheel 10 comprises a disk 12 and a plurality of blades 14. The disk 12 has at its periphery a plurality of teeth 16 spaced apart by housings 18. Each blade 14 of the turbine wheel 10 is engaged in a housing 18 at its foot 20. Each foot 20 of blade 14 has a first hook 22 projecting axially (along the X axis). On each blade 14, the first hook 22 is oriented radially and forms a first groove 24 which opens radially towards the axis of rotation X of the wheel 10. Note that by "radial orientation" is meant "oriented according to a radius of the "turbine wheel" while "axial orientation" means "oriented along the axis of rotation of the turbine".

Each tooth 16 of the disk 12 has a second hook 26 which projects axially (along the X axis). On each tooth 16, the second hook 26 is oriented radially and defines a second groove 28. The first and second hooks 22 and 26 extend axially from the plane defined by the lateral face 12a of the disk 12, on the same side. The first grooves 24 and the second grooves 28 are azimutally aligned. According to the azimuthal direction, the first hooks 22 alternate with the second hooks 26. By "azimuthal direction" is meant "oriented along the circumference of the turbine wheel".

In this example, the first hook 22 is located at the base of the attachment of the blade and the second hooks 26 at the base of the teeth 16. According to a variant, the first hook 22 could be placed on another part of the foot, for example under the platform of the blade 14. The second hooks 26 would then be placed at the top of the teeth 16. In other words, the radial position of the hooks can be adapted.

To axially retain the blades 14 on the disk 12, a rod 30 is disposed in the first grooves 24 and in the second grooves 28. This ring 30 has an annular shape about an axis which coincides with the axis of rotation X of the turbine. The ring 30 has a single catch 32 disposed on an axial face of the ring 30, opposite the lateral face 12a of the disc 12. The catch 32 is disposed between two adjacent feet 20 of two adjacent blades 14. The azimuthal ends 32a cleat 32 are able to abut against the feet 20 which surround it, and more particularly with the first hooks 22, to limit the azimuthal movement of the rod 30 in the first and second grooves 24 and 28.

The cleat 32 is also placed in line with a second hook 26. Whatever the mechanical conditions experienced by the rod 30, the cleat 32 does not come into contact with the second hook 26, neither radially nor azimuthally. Thus, the first hooks 22 are radially longer than the second hooks 26 so that the first hooks 22 are able to cooperate with the catch 32 while the second hooks 26 leave the catch 32 (and therefore the rod 30) free of movement. azimuthal. Consequently, the first grooves 24 defined by the first hooks 22 are deeper than the second grooves 28 defined by the second hooks 26.

So that the tab 32 can not come into contact with the second hooks 26 and that the rod 30 is engaged in the second grooves 28, the rod 30 has an outer annular portion 30a on which the tab 32 does not extend. Thus, the cleat 32 is disposed on an inner annular portion 30b of the ring 30. In this example, the inner annular portion 30b is delimited and separated from the outer annular portion 30a by the intermediate line 30c of the axial face supporting the cleat 32. This intermediate line 30c is a brand machining a chamfer 31a made at the inner peripheral edge 30d on the axial face supporting the latch 32 (cf. fig.2 and 4 ).

The figure 2 represents the engagement of the rod 30 in a first groove 24, seen according to the sectional plane II of the figure 1 . The figure 3 represents the engagement of the rod 30 in a second groove 28, seen according to the sectional plane III of the figure 1 . The depth of the second grooves 28 is less than the distance between the outer peripheral edge 30e of the ring 30 and the catch 32 so that on the figure 3 , the outer peripheral edge 30e of the ring 30 cooperates with the bottom 28c of the second groove 28 while the catch 32 is radially distant from the edge 26a of the second hook 26 at least one set j1. In other words, the clearance j1 is greater than the radial deformations of the rod 30 at the cleat 32 when the turbine wheel 10 operates.

In addition, the bottom 24c of the first grooves 24 is radially further from the axis of rotation X of the turbine wheel 10 than the bottom 28c of the second grooves 28 so that the outer peripheral edge 30e of the rod 30 remains at a minimum. a clearance j2 of the bottom 24c of the first grooves 24 while it cooperates with the bottom 28c of the second grooves 28. In other words, the clearance j2 is greater than the radial deformation of the ring 30 between two first and second hooks 22 and 26. Thus, the ring 30 is held radially only by the second hooks 26 while it cooperates in the axial direction with the first and second hooks 22 and 26. The ring 30 also cooperates with the lateral face 12a of the disc 12 In other words, the rod 30 cooperates radially only with the bottom 28c of the second grooves 28 while it co-operates axially with the lateral faces 24a and 24b of the first grooves 24, with the lateral faces 28a and 28b of the second gorgs. 28, as well as with the lateral face 12a of the disk 12. Thus, the rod 30 cooperates radially only with the second hooks 26. This has the advantage of limiting the contact wear experienced by the first hooks 22, particularly at The bottom of the first grooves 24. This assembly thus limits the risk of rupture of the first hooks 22 of blade 14.

Note that at its outer periphery 30e, the ring 30 has chamfers 31b and 31c on its axial faces to facilitate its insertion into the first and second grooves 24 and 28. The width of the bevel 31b made on the axial face supporting cleat 32 is less important than the width of the chamfer 31c made on the axial face opposite the lateral face 12a of the disc 12. By "width" of the chamfer means the dimension of the chamfer which extends radially on the chamfered portion of the ring.

The figure 4 represents the rod 30 in perspective. The ring 30 has a slot 34 diametrically opposed to the stop 32. The slot 34 is beveled, that is to say that it extends obliquely with respect to a radius of the ring 30. This beveled slot 34 allows easily bend the ring 30 radially in order to insert it into the first and second grooves 24 and 28. In particular, the beveled shape of the slot 34 makes it possible to avoid an interaction between the ends of the ring 30 delimiting the edges of the slot 34 which block and limit the elastic deformation of the ring 30 during assembly. Note that when the wheel 10 is not in operation, the rod 30 is maintained in the first and second grooves 24 and 28 by its natural elasticity while when the turbine wheel 10 is in operation the ring 30 is further maintained in the first and second grooves 24 and 28 by the centrifugal forces.

Preferably, when the rod 30 is mounted on the turbine wheel 10, the slot 34 is disposed in a first or second groove 24 or 28 so that a first or second hook 22 or 26 limits and / or blocks the axial movements of the ends of the ring 30 delimiting the slot 34. Preferably, when the ring is mounted on the turbine wheel 10, the slot is disposed in one of the second grooves 28, under one of the second hooks 26. Advantageously, the azimuthal length the cleat 32 is such that the maximum authorized azimuth movements of the rod leave the slot 34 engaged in a first or second groove 24 or 28. In other words, the azimuthal length of the cleat 32 is such that the slot 34 does not disengage a first or second groove 24 or 28, even when the stop 32 abuts on one of the feet 20 which surround it.

So that the rod 30 is balanced, that is to say so that its center of gravity G is located on the axis of the rod 30 which coincides with the axis X of rotation of the turbine wheel 10, the radial thickness E of the ring 30 varies along the perimeter of the ring 30. In fact, in order to compensate for the surplus of material represented by the catch 32 and the lack of material represented by the slot 34, the radial thickness E of the ring 30 varies. continuously and progressively between the minimum radial thickness Emin at the cleat 32 and the maximum radial thickness Emax at the slot 34. The radial thickness variation E is essentially effected at the inner annular portion 30b of the ring 30. Thus, the center of gravity G of the ring 30 is located on the axis of the ring 30, preferably at the intersection of the median plane of the ring 30. We mean by "median plane" of the ring the plane which passes to the axial half-thickness of the ring 30. Of course, according to one variant, the azimuth balance of the ring can be achieved by adjusting the shape of the chamfers 31a, 31b and 31c. Of course, the combination of both adjustments (chamfer and radial thickness) is also feasible. Furthermore, it is also possible to adjust the equilibrium of the rod by eccentric machining on the cleat 32. The latter being unique, this adjustment by machining is easy and quick to achieve. In addition, the cleat 32 does not have a preferred azimuthal position within the wheel 10, so-called third-party operations, of choosing an azimuthal position of the cleat 32 to improve the overall balance of the wheel 10, are possible .

The figure 5 represents a helicopter turbine engine 100 equipped with the turbine wheel 10. Of course, a second turbine wheel 110 may advantageously be made according to the invention, but not necessarily.

Claims (13)

1. A turbine wheel (10) having an axis of rotation (X) and comprising:

   · a disk (12) having a periphery and a side face (12a);

   · a plurality of blades (14) assembled on the disk (12), each blade (14) having a root (20) of the blade (14) and a first hook (22) projecting axially therefrom, said first hook (22) being oriented radially and defiling a first groove (24) that opens radially towards the axis of rotation (X) of the turbine wheel (10);

   · the disk (12) including a series of second hooks (26) projecting axially from its side face (12a) on the same side as the first hooks (22), each second hook (26) being oriented radially and defining a second groove (28) that opens radially towards the axis of rotation (X) of the turbine wheel (10); and

   · an axial retaining ring (30) including at least one tab (32) and arranged in the first groove (24) and in the second groove (28) in order to retain the blades (14) axially relative to the disk (12);

   said turbine wheel (10) being characterized in that the tab (32) is arranged between two roots (20) of adjacent blades (14) so as to limit the movements of the ring (30) in azimuth.
2. A turbine wheel (10) according to claim 1, characterized in that the tab (32) projects axially from an axial face of the ring (30).
3. A turbine wheel (10) according to claim 1 or claim 2, characterized in that the tab (32) is placed on an inner annular portion (30b) of the ring (30).
4. A turbine wheel (10) according to any one of claims 1 to 3, characterized in that the tab (32) is placed between the first hooks (22) of two adjacent roots (20) of blade (14).
5. A turbine wheel (10) according to any one of claims 1 to 4, characterized in that the tab (32) is placed radially aligned with one of the second hooks (26).
6. A turbine wheel (10) according to any one of claims 1 to 5, characterized in that the minimum distance between the tab (32) and the outer peripheral edge (30e) of the ring (30) is greater than the depth of one of the second grooves (28).
7. A turbine wheel (10) according to any one of claims 1 to 6, characterized in that the first hook (22) of each blade (14) projects radially from the root (20) of said blade (14).
8. A turbine wheel (10) according to any one of claims 1 to 7, characterized in that the root (20) of each blade (14) is engaged in a housing (18) that opens out into the periphery of the disk (12), the housings (18) being separated by teeth (16), with each second hook (26) projecting from one of the teeth (16).
9. A turbine wheel (10) according to any one of claims 1 to 8, characterized in that the tab (32) presents contact faces suitable for making plane-on-plane contact with bearing faces of two roots (20) of blades (14) that limit movement of the ring (30) in azimuth.
10. A turbine wheel (10) according to any one of claims 1 to 9, characterized in that the ring (30) presents a slot (34) diametrically opposite from the tab (32).
11. A turbine wheel (10) according to any one of claims 1 to 10, characterized in that the ring (30) presents the general shape of an annulus having an axis (X), with the center of gravity (G) of said ring (30) being situated on said axis (X).
12. A turbine wheel (10) according to any one of claims 1 to 11, characterized in that the ring (30) co-operates radially solely with the second hooks (26).
13. A turbine engine (100) including a turbine wheel (10) according to any one of claims 1 to 12.

Images