EP2459884B1 - Outer shell sector for a bladed stator ring of an aircraft turbine engine, comprising vibration-damping blocks - Google Patents

Description

The present invention relates generally to an aircraft turbomachine, preferably of the turbojet or turboprop type.

More particularly, the invention relates to the compressor or turbine stator of such a turbomachine, and more specifically to a bladed crown sector comprising a plurality of stator vanes as well as two concentric ferrules carrying the vanes and intended to delimit radially a primary flow through the turbomachine, respectively inwardly and outwardly. Such a bladed crown, generally made using several sectors arranged end to end, is generally used in the compressor or the turbine as a rectifier or distributor.

Turbomachines generally comprise in series a low pressure compressor, a high pressure compressor, a combustion chamber, a high pressure turbine and a low pressure turbine. The compressors and turbines comprise several rows of circumferentially spaced apart blades, these rows being separated by rows of blades that are also circumferentially spaced apart. In the Modern turbomachines, rectifiers and distributors are subject to high dynamic loads. Indeed, the technological evolution leads to a reduction of the number of floors for equal or higher performances, which results in a higher load for each floor. On the other hand, the evolution of production technologies leads to reducing the number of parts, which leads to the reduction of the damping effect of the connections between the parts. This is the case, in particular, when adopting a soldering technology of the abradable cartridge that eliminates a significant source of dissipation of vibration energy.

To solve this vibration problem, it has been proposed in the document FR-A-2 902 843 to segment the outer shell sector into elementary sectors spaced from each other in the tangential direction by radial, oblique or other slits or cuts, each elementary sector carrying a single blade of the bladed crown sector. In addition, tab-shaped damping plates are interposed between the elementary sectors. The operating principle is based on the introduction of a nonlinearity of stiffness in the dynamic behavior of the structure. This non-linearity is activated from a threshold vibratory level of the system. This vibratory activity causes a relative movement between the elementary sectors of the blades and the damping pads. This relative movement causes adhesion losses and successive gluing of damping pads. They result in a continual variation of the local stiffness of the system. As a result, the mode or modes responsible for the vibratory activity are disorganized by the permanent variation of their associated natural frequencies. The resonances of the system can not be installed because of the continual variation of the state of the dynamic system. This results in a reduction of the vibratory levels of the system.

Nevertheless, even if this solution is satisfactory in terms of vibration damping, it remains perfectible. Especially in this solution proposed by the document FR-A-2 902 843 , the damping plates are held pressed against the friction surfaces of the elementary sectors by pressure gradient effect between the aerodynamic stream and the outside of the compressor, applying to these plates a radially inwardly directed force. The disadvantage is that this pressure gradient may not be sufficient to ensure proper plating of the pads against the friction surfaces. In such a case, it results not only a decrease in vibration damping performance, but also a possible breakage of the vein.

In addition, another drawback relating to this solution lies in the over-stressing of one of the blades of the bladed crown sector. Indeed, the aerodynamic forces applied on the blades incorporate a tangential component that can not be taken up in the outer shell sector, because of its segmentation in elementary sectors spaced tangentially. Thus, these tangential components accumulate and transit through the inner ferrule sector of the bladed crown sector, before passing through the blade located at the right of the anti-rotation stop equipping the crown sector. It is therefore this dawn which is extremely solicited because of the inability of the outer shell sector to transmit the static forces in the tangential direction.

The invention therefore aims to remedy at least partially the problems mentioned above, relating to the achievements of the prior art.

To do this, the invention firstly relates to a bladed crown sector according to claim 1.

According to the invention, each vibration damping wedge has a substantially identical profile to that of the elementary sectors.

Due to the particular profile of the wedges, the friction interface between these and the sectors elementary is large, which results in an improved damping effect.

In addition, a support shims against the friction surfaces of the elementary sectors allows a perfect seal between these elements, independent of the pressure differential between the aerodynamic stream and the outside of the compressor or the turbine. Indeed, this seal is obtained by construction, with shims exerting substantially oriented efforts in the tangential direction against the friction surfaces of the elementary sectors. It is noted that this seal is further enhanced in operation, since the plating forces between the friction surfaces and the wedges are accentuated by the application, on the elementary sectors, of the tangential component of the aerodynamic forces exerted on the vanes. of stator.

With regard to the tangential component of the aerodynamic forces acting on the blades, it is noted that one of the essential advantages of the present invention lies in the fact that this component can pass through the outer shell sector assembly, since the latter, although it is sectorized in the tangential direction, is strongly stiffened in this same direction by the particular location of vibration damping wedges. This results in no over-stressing of the vanes, which are therefore loaded substantially uniformly.

Finally, it is stated that since a adopter has a substantially identical profile to that of the elementary sectors, the outer radial delimitation of the primary annular flow, also called vein, is perfectly reconstituted between the elementary sectors spaced apart from one another.

Preferably, said wedge is in abutment against two plane parallel friction surfaces and facing each other in said tangential direction and respectively provided on said two elementary sectors associated with said wedge, and said wedge has two friction surfaces. complementary planes parallel to each other and cooperating respectively with the two friction surfaces of the elementary sectors. The planar contacts between the friction surfaces and the complementary friction surfaces make it possible to ensure a satisfactory damping of the vibrations by friction. In addition, it is possible to simultaneously perform the two friction surfaces during a single machining operation, for example a simple cutting, in order to obtain straight slots, that is to say according to a specific plane , slots in which are then housed the corresponding shims. The manufacture of the assembly according to the invention is greatly simplified, which provides a significant gain in terms of cost and time.

Preferably, said wedge has hooks for its maintenance on the stator of compressor or turbine, these hooks thus having the same profile than those of the brackets worn by the elementary sectors.

Preferably, the elementary sectors are spaced from each other by radial slots fully filled by said damping damping wedges.

Preferably, said damping damping wedges extend substantially in an axial or oblique direction of said assembly. It is expected that each elementary sector carries a single stator vane, or possibly several blades, without departing from the scope of the invention.

The bladed crown can constitute a compressor rectifier, or a turbine distributor.

In addition, the ring sector preferably extends over an angular extent of between 5 and 60 °, but can be up to 360 ° in order to constitute the entire bladed crown.

The subject of the invention is also an aircraft turbine engine comprising a stator of compressor or turbine equipped with at least one sector of bladed crown as described above.

Other advantages and features of the invention will become apparent in the detailed non-limiting description below.

• la figure 1 représente une vue schématique en coupe d'une turbomachine destinée à être équipée d'un ou plusieurs secteurs de couronne aubagée selon la présente invention ;
• la figure 2 représente une vue en coupe représentant une partie du compresseur haute pression de la turbomachine montrée sur la figure 1, et intégrant un secteur de couronne aubagée selon la présente invention ;
• la figure 3 représente une vue en perspective du secteur de couronne aubagée montré sur la figure précédente, le secteur se présentant sous la forme d'un mode de réalisation préféré de la présente invention ;
• la figure 4 représente une vue axiale d'une partie du secteur de couronne aubagée montré sur la figure précédente ;
• la figure 5 représente une vue des profils des cales et des secteurs élémentaires du secteur de couronne aubagée montré sur les figures précédentes, prise selon la ligne V-V de la figure 4 ; et
• les figures 6a à 6c représentent des vues schématisant différentes étapes d'un procédé de fabrication du secteur de couronne aubagée montré sur les figures précédentes.

This description will be made with reference to the appended drawings among which;

• the figure 1 is a schematic sectional view of a turbomachine intended to be equipped with one or more sectors of bladed crown according to the present invention;
• the figure 2 is a sectional view showing part of the high pressure compressor of the turbomachine shown on the figure 1 and incorporating a bladed crown sector according to the present invention;
• the figure 3 is a perspective view of the bladed crown sector shown in the preceding figure, the sector being in the form of a preferred embodiment of the present invention;
• the figure 4 is an axial view of a portion of the bladed crown sector shown in the preceding figure;
• the figure 5 represents a view of the profiles of the holds and the elementary sectors of the bladed crown sector shown in the preceding figures, taken along the line VV of the figure 4 ; and
• the Figures 6a to 6c represent schematic views of different steps in a process of manufacture of the bladed crown sector shown in the preceding figures.

With reference first to the figure 1 it can be seen an aircraft turbojet 100 to which the invention applies. It comprises, from upstream to downstream, a low-pressure compressor 2, a high-pressure compressor 4, an annular combustion chamber 6, a high-pressure turbine 8 and a low-pressure turbine 10.

The figure 2 is a part of the high pressure compressor 4. In known manner, the compressor has, alternately in an axial direction parallel to the axis 12 of the compressor, rows 14 of stator vanes and rows 16 of rotor blades. The stator vanes 18, distributed circumferentially / tangentially about the axis 12, fit into a stator portion called a bladed crown 20, preferably made in a sectorized manner in the circumferential direction 22. Thus, subsequently, it will be done reference to a sector of bladed crown 20, it being understood that this sector 20 preferably extends over an angular extent of between 5 and 60 °, but can be up to 360 ° in order to constitute the entire bladed crown.

The sector 20, thus forming all or part of a turbine distributor or a compressor rectifier, comprises an inner ferrule sector 24 of inner radial delimitation of a primary annular flow 26 passing through the turbomachine, this ferrule sector 24 laying the feet of In addition to these vanes 18, the sector 20 also incorporates an outer ferrule sector assembly 28, radially outer of the primary annular flow 26, which fixes the heads of the vanes 18.

In this regard, it is noted that the sector 20 also comprises known additional elements equipping the ferrule sector 24, such as an abradable radially inner coating 29 forming an annular sealing track, contacted by a sealing device 31 carried by the rotor stage 16 carrying the rotating vanes and arranged downstream of the sector 20 concerned. The rotating sealing device 31 is in a known manner of labyrinth or wipe type.

On the figure 3 it is possible to see the bladed crown sector 20. In the preferred embodiment described, the entire turbine distributor or compressor straightener is obtained by the end-to-end insertion of a plurality of these sectors 20 constituting therefore each an angular or circumferential portion of this crown aubagée. The angular sectors 20 (only one visible on the figure 3 ) are preferably devoid of direct rigid mechanical connections connecting them to each other, their adjacent ends being in fact simply placed opposite each other, with or without play.

More specifically with reference to Figures 3 and 4 it can be seen that the inner ferrule sector 24 is made in one piece, and is not segmented. In contrast, the assembly 28 forming outer shell sector 28 is segmented into elementary sectors 30 spaced from each other in the tangential direction 22, by radial or slightly oblique straight slots 32, thus creating gaps between the directly consecutive sectors 30. Each slot 32 is made along a median straight line between two directly consecutive blades 18, so that each elementary sector 30 fixedly carries a single stator blade 18. One of the two elementary sectors 30 located at the ends of the sector 20 carries an anti-rotation stop 33 protruding radially outwardly, and intended to cooperate, in a known manner, with another part of the stator of the compressor.

The assembly 28 also comprises, housed between the elementary sectors 30 directly consecutive vibration damping wedges 34.

More specifically, each vibration damping wedge 34 is housed between two parallel flat friction surfaces 38 facing one another in the tangential direction 22, and respectively provided on the tangential ends facing each other of the two associated elementary sectors. at the hold. Similarly, each shim 34 has two complementary flat friction surfaces 40, parallel to each other, and also parallel and in contact with the two flat friction surfaces 38 with which they cooperate, respectively.

Each shim 34 is thus sandwiched between two directly consecutive elementary sectors 30, in having a complementarity of shape with that of the friction surfaces 38.

The contact between the two friction surfaces 38, 40 of each pair is obtained preferably as soon as the wedge 34 is placed between its two associated elementary sectors 30. The wedges 34 thus exert, with their complementary flat friction surfaces 40, substantially oriented efforts in the tangential direction against the friction surfaces 38 of the elementary sectors. These efforts are moreover reinforced in operation by the additional application, on the elementary sectors, of the tangential component of the aerodynamic forces exerted on the stator vanes.

As has been schematized on the figure 5 , one of the peculiarities of the present invention lies in the fact that the profile of shims 34 is substantially identical to the profile of the elementary sectors, this same profile corresponding to that of the outer shell sector. By profile, here we mean the overall shape of the element seen in the tangential direction 22, even if a sectional view has been shown in FIG. figure 5 .

Thus, each shim 34 has, like the elementary sectors 30, a lower surface 46 serving as external radial delineation of the vein. The annular overall surface of delimitation of the vein, composed of the succession of these surfaces 46 provided on the wedges 34 and the sectors 30, is therefore substantially continuous from a point of view aerodynamic, since there is no step between the successive surfaces 46.

In addition, each shim 34 and sector 30 includes hooks for its retention on another part of the compressor stator, and more specifically a holding hook 48 projecting forwards, and a holding hook 50 protruding towards the rear. As shown on the figure 2 , the hooks 48, 50 are respectively housed in annular slots 52, 54 provided in another part of the stator of the compressor, in order to ensure the attachment of the sector 20 to this other stator part.

The shims 34, completely filling the slots 32, provide a damping function of frictional vibration against the friction surfaces 38, according to the physical principle mentioned above relating to the holds disclosed in the document FR-A-2 902 843 . They also provide a sealing function, as well as a function of passage of the tangential component of the aerodynamic forces exerted on the stator vanes. Regarding this last point, more generally, each shim 34 allows the transmission of tangential forces between the two elementary sectors 30 between which it is interposed.

The material used for the elementary sectors 30 and the material used for the wedges 34 are substantially of the same nature, preferably metallic, and chosen so that the wedges are used primarily with respect to the elementary sectors 30.

In addition, it is indicated that the ratio between the extent in the tangential direction of each shim, and the extent in the tangential direction of each elementary sector, these extents also corresponding to the thicknesses, is between 0.5 and 1.

The Figures 6a to 6c schematically a manufacturing process of the bladed crown sector 20. First, as shown by figure 6a , in one-piece assembly 100 is produced by casting or by machining, forming the inner ferrule sector 24, the outer ferrule sector 28, and the stator vanes 18. By simple and inexpensive machining, it is then proceeded to the realization of radial straight slots 32 on the outer ferrule sector 28, so as to obtain the elementary sectors 30, as has been schematized on the figure 6b . For example, these slots 32 can be obtained by simply cutting the sector 28.

Finally, Figure 6c shows the final step of placing the vibration damping wedges 34 in the slots 32 forming the friction surfaces by simply sliding the wedges in their respective holes.

It is noted that to obtain relative ease of insertion of each shim in its associated slot, while allowing maintenance of this wedge in its slot by the only pinch between the two friction surfaces 38, a sliding fit game just is preferentially retained.

Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples.

Claims (6)

1. A blade rim sector (20) for equipping a compressor stator of an aircraft turbomachine, comprising an assembly forming an outer shell sector (28), an inner shell sector (24), as well as a plurality of blades (18) tangentially spaced apart from each other and interposed between the assembly forming the outer shell sector and the inner shell sector, said blades being attached on each of the assembly forming the outer shell sector and the inner shell sector, the assembly forming the outer shell sector (28) comprising on the one hand a plurality of unit sectors (30) spaced apart from each other along a tangential direction (22) of said assembly, and on the other hand vibration damping wedges (34) each interposed between two unit sectors associated therewith, positioned directly consecutively along said tangential direction,
   characterised in that each vibration damping wedge (34) has a profile substantially identical to that of the unit sectors (30).
2. The sector according to claim 1, characterised in that said wedge bears against two parallel planar friction surfaces (38) facing each other along said tangential direction (22) and respectively provided on said two unit sectors (30) associated with said wedge, and in that said wedge (34) has two complementary planar friction surfaces (40), parallel to each other and respectively cooperating with both friction surfaces of the unit sectors.
3. The sector according to claim 1 or claim 2, characterised in that said wedge (34) has hooks (48, 50) for being held on the compressor or turbine stator.
4. The sector according to any of the preceding claims, characterised in that the unit sectors (30) are spaced apart from each other by radial slits (32) fully filled with said vibration damping wedges (34).
5. The sector according to any of the preceding claims, characterised in that said vibration damping wedges (34) extend substantially along an axial or oblique direction of said assembly.
6. An aircraft turbomachine comprising a compressor stator equipped with at least one blade rim sector according to any of the preceding claims.

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