EP0209428B1 - Actuation lever for a stator vane with variable incidence - Google Patents

Description

The invention relates to a blade control rod with variable setting of a turbomachine compressor stator comprising at one of its ends means of attachment to a blade pivot and at the other end of means of articulation to a ring. for controlling the position of the blades.

The adaptation of the orientation of the stator blades of one or more stages of a turbomachine compressor to a given speed is generally obtained by means of rods which are fixed at one of their ends to a pivot of the blade. while the other end is articulated on a ring capable of turning under the action of a drive device controlled by the engine speed regulation device.

A broken link leads to feathering of the blade concerned and an impact on the aerodynamic behavior of the compressor. In addition, in advanced engines, the deflection of the blades is calculated as precisely as possible in order to reduce the length of the compressor as much as possible and therefore a blade deprived of its orientation control would strike the rotor, causing serious damage. , even before reaching its flag position.

We have therefore sought to produce a safety device limiting the amplitude of possible accidental deflection of the blade.

Thus, French Patent No. 2,524,934 describes a safety device for a dawn controlled at the head, consisting of an arm fixed to the foot pivot and capable of turning at a limited angle in a housing provided in the 'inner ring holding the bearings of the foot pivots.

Such a device allows the “mad” dawn only to lock in two extreme positions, determined by the abutment of the arm against the walls of the housing, independent of the position of the other blades, and requires a significant modification of the ring. interior and foot pivots.

According to another embodiment, described in French Patent No. 1,325,261, the blades have platforms at the top and at the bottom. These platforms are approximately circular and have two diametrically opposite flats. The platforms are mounted in casings so that the flats of two neighboring blades leave between them a space allowing the blades to pivot between two extreme angular positions. This device has the function of preventing or at least minimizing gas leaks between the platforms in the two extreme angular positions, but it does not care about the leaks it causes in the intermediate angular positions.

Similar devices having the same function are described, for example, in French patents 1,548,701 and British patents 1,324,385.

Such devices are likely to limit the rotation of a blade in the event of a break in its control mechanism. But they are bulky and require a significant adaptation of the stator to receive the platforms. In addition, given the small necessary dimension of the flats, they are not capable of actually controlling this blade from an extreme angular position to the other in the event of a break in the control rod, because they would cause friction and bruising. inadmissible.

The invention relates to the production of a safety device applicable to blades controlled by rods without requiring modification other than those of said rods and making it possible to ensure redundant control although approximate to the blade released.

A set of links, according to the invention, is remarkable in that each link carries on each of the longitudinal sides at least one contact surface whose generatrices are parallel to the axis of rotation of the blade pivot and capable of cooperating at least along a generator with the similar contact surface on the adjacent side of the neighboring link, so as to at least limit the deflection of the blade in the event of the link breaking.

• La figure 1 représente une vue partielle schématique d'un étage compresseur à aubes à calage variable sur le stator.
• La figure 2 est une vue de dessus de la figure 1 montrant un exemple de réalisation de biellettes selon l'invention.
• La figure 3 est une vue identique à celle de la figure 2 mais dans laquelle une biellette est rompue.
• La figure 4 est une vue identique à celle de la figure 3 mais avec les biellettes en position extrême.
• Les figures 5 à 8 présentent différentes formes de réalisation de biellettes conformes à l'invention.
• La figure 9 est une vue en perspective d'une forme de réalisation d'une biellette conforme à celles représentées figure 8.
• La figure 10 est une vue en perspective d'une autre forme de réalisation d'une biellette du même genre que celles de la figure 8.
• La figure 11 est une vue de dessus d'un groupe de trois biellettes selon une autre forme de réalisation dans une position de fin de course.
• La figure 12 est une vue agrandie des surfaces de contact conformes à la réalisation montrée à la figure 11.
• La figure 13 est une vue agrandie des surfaces de contact de biellettes selon une autre forme de réalisation.

The explanations and figures given below by way of example will make it possible to understand how the invention can be implemented. Some variants are indicated. Still other possible variants are not indicated, but they remain within the scope of the claims. Indeed, all the links described here simultaneously perform the blade control function and the travel stop function of this blade when it is released. However, these two functions can also be performed separately, the link retaining its initial function of controlling the blade while a special plate, superimposed on the link and linked to the pivot of the blade in the same way as the link, performs only the stop function described here. We will not describe any advantage of these variants which are easily deduced from those which are described here.

• FIG. 1 represents a partial schematic view of a compressor stage with variable setting vanes on the stator.
• Figure 2 is a top view of Figure 1 showing an embodiment of rods according to the invention.
• Figure 3 is a view identical to that of Figure 2 but in which a link is broken.
• Figure 4 is a view identical to that of Figure 3 but with the rods in the extreme position.
• Figures 5 to 8 show different embodiments of rods according to the invention.
• FIG. 9 is a perspective view of an embodiment of a link in accordance with those represented in FIG. 8.
• FIG. 10 is a perspective view of another embodiment of a rod of the same kind as those of FIG. 8.
• Figure 11 is a top view of a group of three rods according to another embodiment in an end position.
• FIG. 12 is an enlarged view of the contact surfaces according to the embodiment shown in FIG. 11.
• Figure 13 is an enlarged view of the rod contact surfaces according to another embodiment.

Figure 14 is an enlarged view of the surfaces of contact rods according to yet another embodiment.

The schematic view partially in section of a portion of a compressor stage of a turbomachine (FIG. 1) shows a blade 1 with variable setting comprising a pivot 2 at the foot journalling in a bearing 3 placed in an inner ring 4, and a head pivot 5 which passes through the casing 6 of the compressor by a bearing. At one end of the pivot is fixed, by one of its ends 7, a link 8, the other end 9 of which is articulated on a control ring 10.

The blades 1 form the stator stage 11 which distributes the air to the blades 12 of the rotor 13 located downstream.

The rotation of the control ring 10 allows the orientation of the blades at a given angle, depending on the engine speed.

All the top view figures described below represent the rods in the same plane, pivoting around pivots 5 whose axes are perpendicular to this plane. On a turbomachine, the links 8 are arranged on a cylinder of large radius circumscribed to the casing 6 of the compressor and the axes of the pivots converge towards the axis of the turbomachine making between them a very small angle. This implies a slight adaptation of the surfaces which will be described in order to improve the quality of their contacts. These adaptations are easily achievable by those skilled in the art, although not essential. It will not be mentioned in the following description and the surfaces will be considered relative to the projection plane.

In the same way, all the top view figures described below represent symmetrical rods with respect to the longitudinal median plane XX 'which contains the axis 0 of the pivot 5 and the axis 45 of articulation of the rod on the 'ring 10. This symmetry is by no means essential and no mention will be made in the following description of the possible asymmetries. Rods performing the same functions in the same way could be produced with different shapes without departing from the scope of the claims.

FIG. 2 represents, seen from above, a group of rods 14, 15, 16 according to an exemplary embodiment according to the invention, one end of which 17, 18, 19 carries means for fixing to the pivots 5 of the blades 1. The fastening means consist of a polygonal cut 20 which cooperates with corresponding flats machined on the end of the head pivots of the blades 1.

The other ends 21, 22, 23. are articulated by pins 45 on the control ring 10 ensuring the synchronization of the angular displacements of the crown of blades 1 of the stator.

The links have, on each of their longitudinal sides, a flat contact surface and parallel to the longitudinal median plane XX ', capable of cooperating at least along a limiting generatrix with the similar contact surface on the adjacent side of the neighboring link.

According to the embodiment shown, the ends 17, 18, 19 of the rods have the shape of rectangular parallelepipeds centered longitudinally with respect to the axis 0 of the blade pivot, which is also the axis of rotation of the rod. The longitudinal sides, for example 25 and 26, of the central link of the group shown constitute the flat contact surfaces, parallel to the longitudinal median plane XX '. When these links have their longitudinal median planes XX 'approximately perpendicular to the plane of the ring 10, as shown here, their contact surfaces are separated from their neighbors by spaces j allowing their rotation by a given angle in one direction or in the other. Figure 3 shows, for the same group of links in the same position as that of Figure 2, the maintenance of the end 18 of the central link 15 accidentally released. The rupture of a link generally occurs in the zone A between the end 17, 18, 19 comprising the means for fixing to the pivot 5 of the blade and the axis 45 of articulation to the ring 10, this zone being the weakest and the most requested.

The contact surfaces, formed by the sides 25, 26 of the end 18 of the released link 15, abut respectively against the contact surfaces formed by the sides 24, 27 of the neighboring links 14, 16 according to at least two symmetrical generatrices relative to the axis 0 of the blade pivot, which limits the possible travel of the blade 1 released.

Figure 4 shows the maintenance of a link released by two neighboring links for an end position. Contact occurs over almost the entire length of the adjacent planar contact surfaces 25, 24 and 26, 27.

The rods shown in Figures 2 to 4 are more particularly intended to be used in engines "very packed", that is to say of short length. The dimensioning requires both a deflection of the blades (from 10 to 20 ° depending on the stages) and rods of reduced length, hence a positioning of the center of rotation of the blade practically aligned with the midpoints of the sides forming the surfaces of contact.

The contact surfaces allow, in the event of a link breakage, and for an all-or-nothing type adjustment control, taking over of the blade "released" until the end of the race by the neighboring links, whatever whatever the direction of the command. The maximum setting angle corresponds to the abutment one on the other of two neighboring contact surfaces, for example 24 and 25, of two neighboring links. This angle is a function of the distance d separating the axes 0 from two neighboring links and the initial clearance j separating the two adjacent contact surfaces in the middle position of the links.

If the command is modulated, the released blade is immobilized only in the extreme positions of the rods still ordered. In the intermediate positions, the clearances j between the contact surfaces allow it to rotate only within the limits defined by the position of the rods still controlled. For the same distance between axes d between the axes 0 of two neighboring links and the same initial clearance j between the neighboring contact surfaces, the deflection of the blade will be all the smaller as the angle β, formed between the plane longitudinal median XX ′, of the link and the generatrix limiting the contact surface which enters the first in contact with the surface neighbor, will be smaller. In addition, the mating pressure of the contact surface of a vane released on the neighboring surface, the control force to be applied by the surface of a vane still controlled on the surface of the neighboring vane released, and the risk of jamming will be all the smaller the smaller the angle (3.

Figures 5 and 6 show two new embodiments of rods according to the invention in which the contact surfaces are plane, parallel, symmetrical with respect to the longitudinal median plane XX 'of the rod, and remote from the axis 0 of the blade pivot in the longitudinal direction XX '.

In the embodiment of FIG. 5, the contact surfaces, for example 29, 30, of the central link 15 are distant towards the end of the link carrying the means of attachment to the pivot 5, beyond the axis 0 of the blade pivot.

The mode of action of the contact surfaces of the rods close to the released rod is in all respects similar to that of the previous examples.

This embodiment has the advantage of allowing smaller angles β, but the drawback of lengthening the links. The embodiment shown in Figure 6 avoids this drawback by enjoying the same advantage and being less bulky. The contact surfaces are placed between the axis 0 of the blade pivot and the axis of rotation 45 of the link on the ring 10.

The variant shown in FIG. 7 is similar to that of FIG. 5, except that the flat contact surfaces have been replaced by convex cylindrical surfaces. This arrangement makes it possible to reduce or even eliminate the clearance j between two rods, therefore the movement of a rod released in the intermediate positions.

The cylindrical surfaces are formed by two sectors of the same circular cylinder whose axis C is parallel to the axis 0 of the blade pivot, placed in the longitudinal median plane XX 'of the rod and offset relative to the axis of rotation 0 of the link beyond this axis 0.

When the rods pivot around the axes 0, the cylindrical surfaces 32 slide on each other. As a result of the conditions of use of the links, we do not seek to have a zero clearance but a minimum clearance and thus we reduce the deflection of a vane released to a fraction of a degree on either side of the position she should occupy.

According to an exemplary embodiment not shown, but similar to that of FIG. 6, the contact surfaces are placed between the axis 0 of rotation of the link and the axis 45 of articulation on the ring 10 and have a shape cylindrical similar to that of figure 7.

In these last two variants, the stop effect of the rods on one another for the limit switches, as shown in FIG. 4, is no longer achieved by these only cylindrical surfaces. The following realizations show how we can find this effect.

FIG. 8 shows an exemplary embodiment obtained by superposing in the axial direction, that is to say according to the thickness of the rod, the planar contact surface 33 and the cylindrical contact surface 34, the plane of the surface plane being intersecting from the cylindrical surface.

The adjacent flat surfaces 33 of two neighboring rods are therefore spaced from one another, so that they abut one against the other when the rods are in the end-of-travel positions while the cylindrical surfaces 34 are always in contact according to one of their generators or very close and ensure the maintenance of the blade released in the intermediate positions.

The contact surfaces liable to become active therefore consist of a cylindrical surface extended at its ends by a flat surface parallel to the longitudinal median plane XX 'of the link.

Figures 9 and 10 show in perspective two embodiments of rods as described above. The cylindrical surfaces are produced there using a washer of which only the useful middle part has been kept, attached and fixed in known manner to the flats 33.

FIG. 11 represents a group of three links, the contact surfaces of which are formed by a central cylindrical part 35 extended at its two ends by a planar surface 36 tangent to the cylindrical surface at its connection point. These flat surfaces serve as end-of-travel stops for the cylindrical surfaces of the two neighboring connecting rods. The mode of action is easily understood by referring to Figure 12 on a larger scale. In fact, any volume outside the cylindrical surfaces proposed in FIG. 7 prevents the connecting rods in contact from pivoting while preserving their parallelism and therefore stops their angular movement. This same principle is repeated in FIG. 13 which presents another embodiment in which the central convex cylindrical surface 37 is extended at each of its ends by a concave and tangent cylindrical surface 38 of the same radius as the central convex part 37.

FIG. 14 shows another embodiment of rods in which the neighboring sides carry convex cylindrical surfaces 39, 40 extended respectively on both sides by non-tangent planar surfaces 41,42,43, 44 parallel to the longitudinal median plane XX ', so that, in the end position shown, the cylindrical surfaces 39 and 40 come to bear on the flat surfaces 43 and 42 respectively.

As in the previous exemplary embodiments, the contact surfaces can also be arranged between the axis of rotation 0 of the blade and the axis of articulation 45 from the link to the control ring 10.

In order to lighten the manufacturing, it is possible to produce only one of these abutment elements described in FIGS. 11 to 14, on each side of the rods.

The stop system obtained by adding at least one different curvature surface to the convex cylindrical surface is particularly useful when several consecutive rods are broken or detached from the control ring. Indeed, in this case, the clearances or deflections of the released rods increase from the first dawn to the last and, without this system, the last blades would risk taking inadmissible angular positions.

Claims (10)

1. Assembly of links for controlling the variable- setting stator blade of a turbo-engine compressor, each link having, at one of its ends, means for fastening to a blade pivot (5) and, at its other end, means of articulation (45) on a ring (10) for controlling the position of the blades, characterized in that each link has, on each of the longitudinal sides, an approximately plane contact surface (25, 26; 29, 30) parallel to the longitudinal mid-plane (XX') of this link, the generatrices of which are approximately parallel to the axis of rotation (0) of the blade pivot (5), and in that, under normal circumstances, the adjacent contact surfaces of the links are separated by a predetermined distance in the mid-position of the blades and, in the event of the breakage of a link, the adjacent contact surfaces form stop surfaces for limiting the movement of the blade.

2. Assembly of links according to Claim 1, characterized in that the plane contact surfaces (25, 26) of each link are centred longitudinally relative to the axis (0) of the pivot (5) of the corresponding blade.

3. Assembly of links according to Claim 1, characterized in that the plane contact surfaces (29, 30) of each link are longitudinally distant from the axis (0) of the pivot (5) of the corresponding blade.

4. Assembly of links for controlling the variable- setting stator blade of a turbo-engine compressor, each link having, at one of its ends, means for fastening to a blade pivot (5) and, at its other end, means of articulation (45) on a ring (10) for controlling the position of the blades, characterized in that each link has, on each of the longitudinal sides, a contact surface (32; 34; 35; 37; 39; 40) which is at least partially approximately cylindrical and convex and the generatrices of which are approximately parallel to the axis of rotation (0) of the blade pivot (5), when in contact with the adjacent contact surface, and in that the axis (C) of a cylindrical surface is shifted in the longitudinal direction relative to the axis (0) of the corresponding pivot (5).

5. Assembly of links according to Claim 4, characterized in that the convex cylindrical contact surfaces (32) are formed from two sectors of the same cylinder, the axis (C) of which is parallel to the axis of rotation (0) of the pivot (5) of the corresponding blade.

6. Assembly of links according to one of Claims 4 or 5, characterized in that the cylindrical contact surfaces (34) are superposed, in the radial direction of the compressor stage, on plane contact surfaces (33), the plane containing the plane surface intersecting the cylindrical surface and being parallel to the axis of rotation (0) of the corresponding blade pivot (5).

7. Assembly of links according to one of Claims 4 or 5, characterized in thatthe convex cylindrical contact surfaces (35) are extended, at at least one of their ends, by a plane surface (36) tangent to the cylindrical surface at its connecting point.

8. Assembly of links according to one of Claims 4 or 5, characterized in that the convex cylindrical contact surfaces (37) are connected, at at least one of their ends, to a concave cylindrical surface (38) of the same radius and tangent to the convex cylindrical surface at its connecting point.

9. Assembly of links according to one of Claims 4 or 5, characterized in that the convex cylindrical contact surfaces (39, 40) are extended, at at least one of their ends, by a plane contact surface parallel to the axis of rotation (0) of the corresponding blade pivot (5).

10. Assembly of links according to any one of the preceding claims, characterized in that each link is composed of two independent parts, the first performing the function of controlling the blade according to an already known form, and the second, superposed on the first and connected to the blade pivot (5) in the same way, performing the function of an angular stop for the blade in the event of breakage of the first part and for that purpose having on its longitudinal sides, contact surfaces according to the preceding claims.

Images