EP0305223B1 - Blade locking device and (de)mounting thereof - Google Patents

Description

The invention relates to the means for mounting and locking the crowns of blades with hammer feet for the rotor discs of a turbomachine.

The blade / disc connections of the last stages of the high pressure compressors of turbomachines with a high compression ratio are preferably produced by a technology called "hammer attachment".

The reasons for this choice are to allow an improvement in the seals by limiting the recirculation of gas under the blade roots and a reduction in the cost of machining the discs.

This technique consists in machining a circumferential groove with a dovetail section on the rim of the disc, the feet of the blades made up of protuberances arranged under the platform - and whose section is substantially identical to that of the groove - being introduced. in the groove, then slipped peripherally into it, one after the other, and locked by various means.

The axial dimension of the root of the blades being generally greater than that of the opening of the groove of the disc, it is necessary to provide on the rim, at least one "window" through which the feet of the blades are introduced radially before sliding them peripherally.

In some applications, the disc does not have a window; to introduce the feet of the blades, you must orient their long axis parallel to the groove, push in feet radially and then make them rotate 90 ° before sliding them peripherally.

All the applications known to date have a certain number of drawbacks such as the obligation to crop the corners of the platforms when a 90 ° rotation is made at dawn, difficulties in mounting the last blades, or the need to lock the locks themselves by means of screws or pegs that can be released during operation and damage the machine.

Another drawback stems from the need to leave a hole drilled in the platforms of the blades associated with the lock in order to be able to access the latter for dismantling the crown.

Thus FR-A-1541373 describes a lock coming to be housed between two blade roots in the introduction window and whose unlocking tabs must be accessible through lights of the blade platforms. These platform lights create disturbances in the boundary layer of the flow in the vein and are detrimental to the operation of the compressor. These disturbances can also cause vibrations which could cause the unlocking of the lock and the sliding of the blades in their groove.

The device according to FR-A-2519073 has a structure of the same type which has been complicated in trying to limit the risks but which still requires lights in the platforms of the closing vanes.

The invention aims to avoid this kind of drawback by providing a locking device accessible from below the blade platforms for its disassembly and which does not require radial opening in the platforms.

It also aims to avoid any risk of recirculation of fluid, and of pressure loss from downstream to upstream by producing a device which, once locked, closes all the interstices of the disc which could allow such recirculations. The subject of the invention is therefore a turbomachine rotor disc comprising a crown of blades of a turbomachine, the feet of which are engaged by a window in a circumferential groove in the rim of the rotor disc in which they can slide; the device comprises a locking bolt cooperating with three adjacent vanes, called closing vanes, and according to the invention, the rim of the disc has an upstream rib and a downstream rib delimiting between itself a circumferential groove, said ribs supporting the platforms vanes while the latch has a double elastic omega shape disposed under the platforms of the closing vanes and whose wings folded under the platforms cooperate with notches in the ribs to ensure the circumferential and radial locking of the crown of 'blades, said double omega lock having a curved body having a recessed central part and at each of these ends a pair of folded wings, said curved body coming to be disposed in the circumferential groove of the disc while in the recessed central part is arranged at the foot of one of the closing vanes, called the central closing vane, the two ends of the v errou being arranged between the foot of the central blade and the feet of the two other blades, said to be lateral, for closing.

• ― la figure 1 montre une vue partielle de la jante du disque;
• ― la figure 2 montre la forme du verrou selon l'invention;
• ― la figure 3 est une vue identique à la figure 2 avec son verrou en place, en l'absence des aubes;
• ― la figure 4 montre une vue en coupe AA de la figure 7 du disque des figures précédentes avec le verrou comprimé entre les nervures amont et aval, en cours de montage;
• ― la figure 5 montre une vue similaire avec les ailes du verrou engagées dans les encoches des nervures du disque;
• ― la figure 6 montre en comparaison les plates-formes d'aubes d'une aube normale (figure 6a), de la première et de la seconde aubes latérales de fermeture (resp. figures 6b et 6c) et de l'aube centrale de fermeture (figure 6d), pour des aubes dont les plates-formes possèdent une partie centrale massive s'étendant normalement sous toute la largeur de la plate-forme;
• ― la figure 6d est également représentative d'une autre variante d'aubes dont la partie massive de la plate-forme est limitée à la section du pied d'aube auquel cas les aubes latérales pas plus que l'aube centrale ne comportent de différences par rapport aux autres aubes formant l'aubage complet;
• ― la figure 7 montre en vue de dessus les aubes de fermeture et le verrou en place;
• ― les figures 8 à 15 décrivent le déroulé opératoire du mode de montage.

Other characteristics of the invention as well as the assembly and disassembly methods will be explained in the light of the attached plates, among which:

• - Figure 1 shows a partial view of the rim of the disc;
• - Figure 2 shows the shape of the lock according to the invention;
• - Figure 3 is a view identical to Figure 2 with its lock in place, in the absence of the blades;
• - Figure 4 shows a sectional view AA of Figure 7 of the disc of the previous figures with the compressed latch between the upstream and downstream ribs, during assembly;
• - Figure 5 shows a similar view with the wings of the lock engaged in the notches of the ribs of the disc;
• - Figure 6 shows in comparison the blade platforms of a normal blade (Figure 6a), the first and second lateral closing blades (resp. Figures 6b and 6c) and the central blade of closure (FIG. 6d), for vanes whose platforms have a massive central part which normally extends over the entire width of the platform;
• - Figure 6d is also representative of another variant of blades whose massive part of the platform is limited to the section of the blade root in which case the side blades no more than the central blade have differences compared to the other blades forming the complete blade;
• - Figure 7 shows a top view of the closing vanes and the latch in place;
• - Figures 8 to 15 describe the operating procedure of the mounting method.

With reference to FIGS. 1 and 2, the rotor disc for example for a high pressure compressor of a turbomachine comprises a rim 1 at the periphery of which is machined a circumferential groove 2 with a narrow opening and swollen interior for fixing blades with hammer feet, that is to say having a dovetail-shaped foot which can be introduced into the groove in a known manner by an introduction window 3.

The outer edge of the disc has upstream and downstream two lateral ribs 4 and 5 intended to support the lower part of the platforms of the blades once mounted. Between the two ribs 4 and 5 is machined a circumferential flat 6 which forms a circular groove. Each of the ribs 4 and 5 has a pair of notches 4a, 4b, (resp. 5a, 5b) whose bottom is flush with the flat of the groove 6, the notches 4a and 5a (resp. 4b and 5b) facing each other. cooperate with the lock 7 according to the invention shown in FIG. 2.

This consists of an elastic foil, the bulged body 8 of which is adapted to lodge in and match the internal shape of the groove 2. The lock 7 has at its ends two pairs of folded wings 9a, 9b such that the wings 9a and 9b are located in the same plane. Between the two pairs of wings, the bolt has a central recess 10 whose width corresponds to that of a blade root while the width of the wings 9a, 9b corresponds to that of the notches 4a, 4b, 5a and 5b. Thus produced the latch 7 has the form of two inverted capital "omega" connected together by a trigger guard 11.

Referring to Figures 3 to 5, we can see that the lock 7 is elastic, these wings 9a and 9b can be compressed so that the curved body 8 of the bolt can penetrate through the narrow opening of the groove 2 of the disc, the wings 9a and 9b being able at first to remain compressed between the ribs 4 and 5 of the rim, thus as shown in Figure 4 or in a second step, be relaxed in the notches 4a, 5a and 4b, 5b (Figures 3 and 5), the lock being then locked circumferentially.

Preferably the notches 4a 5a, 4b, 5b of the ribs of the rim will be distant from the insertion window 3 by a distance such that, after assembly, said window is astride two feet of consecutive blades.

The lock 7 must be able to be housed under the platforms of the closing vanes (as will be seen below), these must in some cases be slightly different from the ordinary vanes 12 of the crown of blades of the stage of rotor.

Two cases are indeed to be considered:

- In the first of these two cases, the blades of the blade crown have a platform, the lateral edges of which are not orthogonal to the median plane of the disc ("diamond" platforms). The platforms of the "normal" blades 12 (that is to say of all the blades of the crown except the closing blades) then have (FIG. 6a) a massive central part 12a which extends from the lateral edge 12b at the lateral edge 12c, the lower surface of the solid part 12a resting on the bottom of the circumferential groove 6 while the upstream and downstream edges 12d, 12e rest on the upper part of the ribs 4 and 5. This arrangement is intended to avoid that these diamond platform vanes are not likely to brace in the groove 2 during their compaction against each other by sliding their adjacent side edges against each other in the mounting operations. Indeed, this arrangement ensures good guidance of the blades by cooperation of the edges of the central part 12a with the edges of the ribs 4 and 5.

To allow the latch to be put in place, the three closing vanes must then be slightly different from the normal vanes forming almost the entire circumference of the vane.

By comparison, with the vanes 12, we have shown in FIGS. 6b and 6c, the two lateral closing vanes 14 and in FIG. 6d the central closing vane. The first lateral blade 14 (FIG. 6b) has on the underside of its platform a clearance 16 from the central solid part which will allow the thickness of one of the wings 9a or 9b of the bolt to be mounted. The second lateral blade 15 (FIG. 6c) has, for the same reasons, a symmetrical clearance 17 of the clearance 16 of the first lateral blade 14, in order to receive the thickness of the second wing of the bolt.

The central blade 18 (FIG. 6d) intended to be disposed in the recessed part 10 of the lock 7 between the folded wings 9a and 9b has, for its part, on either side of its foot, clearances 19, 20 on the underside of its platform in order to receive the thickness of the wings 9a and 9b of the lock.

- in the second case, the blades have a rectangular platform (lateral edges orthogonal to the median plane of the disc). In this case the problem of bracing of the blades during assembly does not arise and the central part massive of each of the blades of the blade is limited laterally to the right of the section of the blade root in a configuration similar to that of the central blade closing of the previous case shown in Figure 6d. All the blades of the disc can therefore in this second case be identical.

The invention also relates to the methods of mounting and dismounting the device, the structural description of which has been given above, and these methods of mounting and dismounting such a crown of blades will be better understood with reference to FIGS. 4, 5 and 8 to 15. In the following text, it will be a question of displacements "towards the right" or "towards the left", this with reference to the sequence represented on the figures but it is quite obvious that the mentions are given as indicative since they depend on the upstream or downstream side from which one looks at the disc and that the lock being symmetrical, an equally "symmetrical" reading can be made of the text which will follow. On the other hand, the assembly sequence has been shown with blades whose platforms have the clearances indicated, without this representing a limitation of the invention.

In fact, these assembly and disassembly methods apply in the same way whether it is a question of assembling or disassembling vanes with diamond-shaped platforms or vanes with rectangular platforms. In the latter case, it will be obvious that in the process steps below, the mention of the central and lateral closing blades will refer, as we saw above, to ordinary blades, while in the case of diamond blades, the mention of the closing vanes will refer to the vanes shown in FIGS. 6b to 6d.

• a) on introduit chacune des aubes 12 de la couronne dans la gorge 2 par la fenêtre d'introduction 3 puis par déplacement latéral d'un pas des aubes déjà introduites et ceci à l'exception des trois aubes de fermetures 14,15,18;
• b) on introduit l'aube latérale gauche 14 et on la déplace d'un pas vers la gauche (figure 8);
• c) on introduit le verrou 7 dans la gorge 2 en comprimant ses ailes rabattues 9a, 9b au moyen d'une pince de telle sorte que les ailes soient comprimées dans la rainure 6 entre les nervures amont et aval 4, 5 de la jante 1 du disque (figures 9, 10, et 4);
• d) on déplace latéralement vers la gauche le verrou 7 comprimé sous le dégagement 16 de l'aube latérale gauche 14 jusqu'à laisser libre la fenêtre 3 d'introduction (figure 11);
• e) on introduit l'aube latérale droite 15, le dégagement 17 de sa plate-forme venant coiffer l'extrémité comprimée du verrou 7 (figure 12);
• f) on déplace l'ensemble des aubes vers la droite jusqu'à ce que la partie centrale évidée 10 du verrou 7 coïncide avec la fenêtre 3 d'introduction (figure 13):
• g) on introduit l'aube centrale de fermeture 18 par la fenêtre 3 dans la partie centrale évidée 10 du verrou 7;
• h) on déplace l'ensemble de la couronne d'aubes circonférentiellement jusqu'à engagement des ailes 9a, 9b du verrou 7 dans les encoches 4a, 5a et 4b, 5b des rainures 4, 5 de la jante 1 du disque.

For mounting the blades on the rim of a turbomachine rotor disc and locking them by the device according to the invention, the following steps are carried out:

• a) each of the blades 12 of the crown is introduced into the groove 2 through the introduction window 3 and then by lateral displacement of one pitch of the blades already introduced and this with the exception of the three closing blades 14,15,18 ;
• b) the left lateral blade 14 is introduced and it is moved one step to the left (FIG. 8);
• c) the lock 7 is introduced into the groove 2 by compressing its folded wings 9a, 9b by means of pliers so that the wings are compressed in the groove 6 between the upstream and downstream ribs 4, 5 of the rim 1 of the disc (Figures 9, 10, and 4);
• d) the bolt 7 compressed under the clearance 16 of the left lateral blade 14 is moved laterally to the left until the opening window 3 is left free (FIG. 11);
• e) the right side blade 15 is introduced, the clearance 17 of its platform coming over the compressed end of the lock 7 (FIG. 12);
• f) the set of blades is moved to the right until the hollowed-out central part 10 of the latch 7 coincides with the introduction window 3 (FIG. 13):
• g) the central closing vane 18 is introduced through the window 3 into the hollowed-out central part 10 of the latch 7;
• h) the whole of the crown of blades is moved circumferentially until the wings 9a, 9b of the lock 7 engage in the notches 4a, 5a and 4b, 5b of the grooves 4, 5 of the rim 1 of the disc.

The crown of blades is then locked circumferentially and the closing blades are also locked radially since no blade root is no longer located in front of the introduction window.

In addition, the platforms of the closing blades have an upper surface identical to those of ordinary blades of the crown without projecting or hollow part and do not, therefore, risk creating disturbances in the vein of which they form. the internal wall at the level of the rotor stage thus assembled.

In addition, the wings 9a and 9b of the lock arranged in the notches 4a, 5a, and 4b, 5b are flush with the edge of the rim 1, which therefore retains a smooth outline without hollow parts, although the lock is still accessible. for disassembly operations.

• a) on pince les ailes du verrou au moyen d'une pince 20 (représentée en pointillés à la figure 5), engagée sous les plates-formes des aubes latérales de fermeture 14,15 pour comprimer les ailes 9a, 9b entre les nervures 4 et 5.
• b) on déplace latéralement l'ensemble d'aubes jusqu'à coïncidence de la fenêtre 3 avec l'aube centrale 18 et on extrait celle-ci;
• c) on déplace latéralement l'ensemble d'aubes jusqu'à coïncidence de la fenêtre 3 avec une aube latérale 14 ou 15 et on extrait celle-ci;
• d) on déplace latéralement l'ensemble d'aubes jusqu'à coïncidence de la fenêtre avec la seconde aube latérale 15 ou 14 et on extrait cette dernière;
• e) on extrait le verrou 7 comprimé hors de la gorge;
• f) on retire de façon connue les autres aubes 12 de la couronne.

The disassembly of the blade crown is then carried out according to the following steps:

• a) the wings of the lock are clamped by means of a clamp 20 (shown in dotted lines in FIG. 5), engaged under the platforms of the lateral closing vanes 14, 15 in order to compress the wings 9a, 9b between the ribs 4 and 5.
• b) the blade assembly is moved laterally until the window 3 coincides with the central blade 18 and the latter is extracted;
• c) the set of blades is moved laterally until the window 3 coincides with a side blade 14 or 15 and the latter is extracted;
• d) the blade assembly is moved laterally until the window coincides with the second lateral blade 15 or 14 and the latter is extracted;
• e) the compressed latch 7 is extracted from the throat;
• f) the other vanes 12 are removed in a known manner from the crown.

This locking device therefore provides great mounting security while making it simpler than in the past to manufacture the blades, since the closing blades differ from the normal blades of the stage and only in the case of platform blades. in rhombus by the mere presence of clearances, easy to machine, in the lower surface of their platform, the production of the latch by tinsel being also simple and inexpensive.

Claims (6)

1. Rotor disc of a turboshaft engine comprising a ring of blades whose roots are introduced through a window (3) into a circumferential slot (2) in the rim (1) of the disc in which they can slide, a device comprising a locking-piece (7) working in conjunction with three adjacent blades called the closure blades (14, 15, 18) characterised in that the rim (1) of the disc comprises an upstream rib (4) and a downstream rib (5) defining between them a circumferential groove (6), the said ribs supporting the platforms of the blades, and in that the locking-piece (7) is in the form of an elastic double omega placed under the platforms of the closure blades and whose wings (9a, 9b), flattened under the platforms work in conjunction with cut-outs (4a, 5a and 4b, 5b) in the ribs (4, 5) to ensure both the circumferential and radial locking of the ring of blades, the said double omega locking-piece (7) comprising a curved body (8) having a central hollowed out portion (10) and at each end a pair of flattened wings (9a, 9b), the said curved body being placed in the circumferential slot whilst in the hollowed out portion is placed the root of one of the closure blades, called the central closure blade (18), the two ends of the locking-piece fitting between the root of the central blade (18) and the roots of the other two blades, called the lateral closure blades (14, 15).

2. Device in accordance with Claim 1 characterised in that the cut-outs (4a, 5a and 4b, 5b) in the ribs (4, 5) of the rim are distanced from the blade insertion window (3) by a distance such that, after installation, the said window (3) should overlap two consecutive blade roots.

3. Device in accordance with either of Claims 1 or 2 characterised in that the central closure blade (18) comprises symmetrical cut-away portions on the underside of its platform on both sides of the blade root.

4. Device in accordance with any of Claims 1 to 3 characterised in that the two lateral closure blades (14, 15) have on the underside of their platforms a cut-away portion (resp. 16, 17) on only one side of their root.

5. Assembly and locking process for the blade ring of a rotor with a locking device in accordance with one of the Claims 1 to 4 fitted to the rim of a rotor disc for a turboshaft engine characterised in that it comprises the following steps:

a) each of the blades (12) of the ring is inserted into the slot (2) through the blade insertion window (3) and then, by moving laterally by the width of one blade, the blades already inserted, with the exception of the three closure blades (14, 15, 18);

b) the lefthand lateral blade (14) is inserted and moved laterally leftwards by the width of a blade;

c) the locking-piece (7) is introduced into the slot (2) by compressing its flattened wings (9a, 9b) by means of a cramp of such type that the wings are compressed into the groove (6) between the upstream and downstream ribs (4, 5) on the rim (1) of the disc;

d) the compressed locking-piece (7) is moved laterally under the cut-away portion (16) of the left lateral blade (14) until the blade insertion window (3) is left clear;

e) the right lateral blade (15) is inserted, the cut-away portion (17) of its platform covering the compressed end of the locking-piece (7));

f) all the blades are pushed to the right until the central hollowed out part (10) of the locking-piece (7) coincides with the blade insertion window (3);

g) the central closure blade (18) is inserted through the window (3) into the central hollowed out portion (10) of the locking-piece (7);

h) the whole of the ring of blades is moved circumferentially until the wings (9a, 9b) of the locking-piece (7) engage with the cut-outs (4a, 5a and 4b, 5b) in the ribs (4, 5) of the rim (1) of the disc.

6. Dismantling process for a ring of blades in accordance with any one of Claims 1 to 4 characterised in that it comprises the following steps:

a) the wings of the locking-piece are compressed by means of a cramp (20) fitting under the platforms of the lateral closure blades (14, 15) to compress the wings (9a, 9b) between the ribs (4 and 5);

b) the whole set of blades is moved laterally until the blade insertion window (3) coincides with the central blade (18) and this is withdrawn;

c) the whole set of blades is moved laterally until the blade insertion window (3) coincides with a lateral blade (14 or 15) and this is withdrawn;

d) the whole set of blades is moved laterally until the blade insertion window (3) coincides with the second lateral blade (15 or 14) and this latter is withdrawn;

e) the compressed locking-piece (7) is withdrawn from the slot;

f) in known manner, the other blades of the ring are withdrawn.

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