EP1818507A1 - Rotor wheel of a turbomachine - Google Patents

Abstract

Turbomachine rotor wheel, which wheel comprises a disk (24) carrying blades (16) whose feet (18) are engaged and retained in an annular groove (20) of the disc, these feet being connected to platforms ( 44) for cooperating with an annular seal (54) mounted in an annular groove of the disk, the annular seal (54) exerting on the platforms (44) of the blades an elastic force holding the vanes (16) in a correct operating position, when stopping the turbomachine.

Description

The present invention relates to a rotor wheel, in particular a turbomachine, comprising a disc carrying blades whose feet are mounted in an annular groove of an outer peripheral surface of the disc.

The blade roots are introduced into this groove by a window of a side wall of the groove, and then circumferentially displaced in the groove to be retained radially and axially relative to the axis of the rotor by cooperation of shapes, the throat being of dovetail cross section or the like and the blade roots having a shape conjugate with that of the groove.

The blade roots are connected to the blades of the blades by platforms which, when the blades are mounted in the groove and juxtaposed circumferentially, surround the outer surface of the disk peripherally.

Manufacturing and assembly tolerances ensure that the blade roots are housed with clearance in the annular groove of the disc.

In operation, the blades, subjected to large centrifugal forces, adopt a correct angular position with respect to the axis of the rotor, in which the radial clearances between the outer ends of the blades and an outer annular casing are minimized to improve the performance of the rotor. the turbomachine.

An annular elastomeric seal is generally mounted in an annular groove of the peripheral surface of the disk, upstream and / or downstream of the blades, under the platforms of the blades, and has in the free state a lower outer diameter or equal to that of its mounting groove to not interfere with the circumferential sliding of the blades in the annular groove of the disc.

In operation, this seal expands radially outwards under the effect of centrifugal forces and comes into contact with the platforms blades, to prevent an air passage between the platforms and the outer peripheral surface of the disk, which would reduce the performance of the turbomachine, and / or to dampen the vibrations of the blades.

At startup and shutdown of the turbomachine, the vanes of the wheel can tilt more or less with respect to their operating position and their ends can come rub on the outer casing, which results in a deterioration of the blades and a reduced performance of the turbomachine.

The invention aims in particular to provide a simple, economical and effective solution to this problem.

It relates to a rotor wheel whose blades are maintained, in operation and at the stop and start, substantially in the same position relative to the axis of the rotor.

It proposes for this purpose a rotor wheel, in particular a turbomachine, comprising a disc carrying blades whose feet are engaged and retained in an annular groove of an outer peripheral surface of the disk, these feet being connected to platforms externally surrounding the outer peripheral surface of the disk and intended to cooperate with an annular sealing gasket mounted in an annular groove of the outer peripheral surface of the disk, characterized in that, when stationary, the annular seal exerts on the plates. forms of the blades an elastic force maintaining the blades in a correct operating position, the annular seal having, in the free state, an outer diameter greater than that of its mounting groove, and its hardness being determined to ensure the return of the blades in their correct operating position and to allow the circumferential movement of the blades in their grooves annula mounting.

In operation of the turbomachine, the annular seal damps the vibrations of the vanes and / or prevents the passage of air between the platforms of the vanes and the peripheral surface of the disc, and during the starting and stopping phases of the turbomachine, this same seal allows to position the vanes in a correct manner to prevent their ends from rubbing on the outer casing.

When the root of a blade is introduced into the annular groove of the disk through the window, the platform of this blade comes into contact with the annular seal and deforms it locally. The hardness of the elastic seal is determined so that the restoring force exerted by the seal on the blade is sufficiently small to allow the circumferential displacement of the blade in the groove and sufficiently large to ensure the correct positioning of the blade once. that it is mounted in the throat.

The seal preferably has a symmetrical shape with respect to its median transverse plane, which makes it easier to manufacture and to avoid incorrect assembly of the seal in the annular groove of the disc.

According to another characteristic of the invention, the seal comprises at least one outer peripheral lip intended to extend projecting outside the groove when the seal is mounted in the groove. This lip comes into contact with the platforms of the vanes mounted on the disc and ensures both the correct positioning of the blades, when stopping and starting the turbomachine, and the sealing between the platforms of the blades and the blade. peripheral surface of the disc and / or the damping of the vibrations of the blades, in operation of the turbomachine.

The seal may also include at least one inner peripheral lip for pressing against the bottom of the groove when the seal is mounted in the groove.

In one embodiment of the invention, the annular seal has in cross section a substantially parallelogram or rhomboidal shape, an apex of which forms a radially inner or outer lip of the seal.

In another embodiment of the invention, the annular seal has a cross-section substantially in the form of X or H.

The present invention also relates to an annular seal for a rotor wheel as described above, characterized in that it has, in the free state, an outer diameter greater than that of its annular groove. mounting and a Shore A hardness between 50 and 100 and for example equal to 75. This seal is for example made in "VITON A" or "VITON B".

This annular seal may be a seal and / or a vibration damping seal.

The invention also relates to a turbomachine compressor, comprising at least one rotor wheel as described above, and a turbomachine, such as an airplane turbojet or turboprop, characterized in that it comprises at least one rotor wheel as described above.

• la figure 1 est une demi-vue schématique en coupe axiale d'un compresseur basse-pression de turbomachine comprenant une roue de rotor selon la technique antérieure ;
• la figure 2 est une vue agrandie du détail I₂ de la figure 1 ;
• la figure 3 est une vue schématique correspondant à la figure 2 et représentant un mode de réalisation d'une roue de rotor selon l'invention ;
• la figure 4 est une vue agrandie du détail I₄ de la figure 3 ;
• la figure 5 est une vue schématique correspondant à la figure 4 et représentant une variante de réalisation de l'invention.

The invention will be better understood and other characteristics, details and advantages of the invention will appear on reading the following description given by way of non-limiting example with reference to the accompanying drawings in which:

• Figure 1 is a schematic half-view in axial section of a low-pressure turbomachine compressor comprising a rotor wheel according to the prior art;
• Figure 2 is an enlarged view of detail I ₂ of Figure 1;
• Figure 3 is a schematic view corresponding to Figure 2 and showing an embodiment of a rotor wheel according to the invention;
• Figure 4 is an enlarged view of detail I ₄ of Figure 3;
• Figure 5 is a schematic view corresponding to Figure 4 and showing an alternative embodiment of the invention.

The low-pressure compressor 10 of FIG. 1 comprises three compression stages, each of these stages comprising an annular row of fixed vanes 12 of rectification, the radially outer ends of which are borne by an outer annular casing 14, and an annular row of moving blades 16, arranged downstream of the annular row of fixed blades 12, and whose feet 18 are mounted in an annular groove 20 of an outer peripheral surface of a disc 24 of a rotor wheel.

In the example shown, the disk 24 comprises a wall of revolution 22 which comprises external annular ribs 26 between which are delimited the annular grooves 20 for mounting the rows of blades 16, respectively.

The disc 24 is connected to a shaft of the turbomachine, not shown, by means of a drive cone 28 fixed on an upstream annular flange 30 of the revolution wall 22 of the disc.

Each groove 20 conventionally has a cross-section of the dovetail type or the like and comprises a non-visible window for introducing the feet 18 of the blades 16 which have a shape complementary to that of the groove 20.

As best seen in Figure 2, the groove 20 of the disc 24 comprises an annular bottom 31 extending between two side walls 32 each having an axial annular flange 34 oriented substantially towards the opposite side wall 32. The introduction window of the feet 18 of the blades is for example formed in a side wall 32 of the groove or by cutting the annular rims 34 of the groove.

The feet 18 of the vanes comprise upstream and downstream flanges 42, circumferentially oriented around the axis of the rotor, intended to be housed between the bottom 31 of the groove and the annular rims 34 of the groove, respectively, and to cooperate by abutment with these so as to retain radially and axially the vanes 16 on the disk relative to the axis of the rotor.

The blades 16 (for example 62 in number) are introduced into the annular groove 20 of the disk one after the other and are juxtaposed circumferentially around the axis of the rotor. The feet 18 of the blades are connected to the blade blades by platforms 44 which are circumferentially aligned with each other and surround the annular ribs 26 externally.

Manufacturing and assembly tolerances cause the blade roots 18 to be mounted with clearance in the groove 20 of the disk.

In the example shown, the radial clearance between the radially outer end of a downstream rib 26 and the corresponding part of the blade root or the platform 44 can reach 0.15 mm in the case of a ring groove Having an outer diameter of about 1.20 m.

In operation of the turbomachine, the blades 16 are subjected to significant centrifugal forces and adopt a rectified angular position with respect to the axis of the rotor in which the downstream edges 42 of the blade roots abut on the rim 34 of the downstream wall. 32 of the groove (Figure 2), and the platforms 44 of the blades are supported on the outer periphery of the upstream wall 32 of the groove and are spaced from the outer periphery of the downstream wall 32 of the groove, the games Radials between the outer ends of the blades 16 and the outer casing 14 are then minimized to improve the performance of the turbomachine.

The inner surface of the platform 44 of each blade comprises an annular rib 46 projecting towards the axis of the rotor which is hooked on the outer periphery of the upstream wall 32 of the groove, as shown in FIG.

A one-piece annular seal 50 of elastomer and circular section is mounted in an annular groove 52 of the outer periphery of the downstream side wall 32 of the groove, this groove 52 opening radially outwardly under the downstream ends 48 of the platforms blades.

The seal 50 has in the free state an outer diameter less than or equal to that of the groove 52 (as shown in dashed lines in Figure 2) and is, at rest, housed entirely in the groove. This seal 50 may be a seal and / or a vibration damping seal.

In operation of the turbomachine, the seal 50 expands radially outwards under the effect of centrifugal forces and is supported on internal downstream surfaces 48 of the blade platforms (as shown in solid lines), to prevent an air passage between the platforms of the blades and the outer periphery of the downstream wall 32 of the groove, and / or to exert pressure on the platforms and dampen the vibrations of the blades.

When the turbomachine stops and starts, the vanes 16 of the wheel swing slightly downstream and adopt another angular position with respect to the axis of the rotor, in which the downstream edges 42 of the blade roots come into contact with each other. support on the bottom 31 of the groove so that the radially outer ends of the blades 16 are likely to touch the outer casing 14, which may deteriorate the blades at startup and shutdown and thus reduce the performance of the turbomachine .

The invention responds to this problem by means of an annular seal mounted in the groove 52 and which makes it possible, on stopping the turbomachine, to exert on the platforms 44 of the vanes an elastic force urging the blades 16 towards their position. operating in which the ends of the blades are spaced apart from the outer casing 14 and can not rub on it.

In a first embodiment shown in FIGS. 3 and 4, the seal 54 has a substantially diamond-shaped section and comprises an outer peripheral lip 56 with a triangular section intended to protrude outside the groove 52 in order to come into contact. bearing against the internal downstream surfaces 48 of the platforms of the blades, and an inner peripheral lip 58 with a triangular section intended to bear against the bottom of the groove 52, when the seal 54 is mounted in the groove. The upstream and downstream edges 60 of the gasket 54 are intended to bear against the lateral walls of the groove 52.

The dimensions and the hardness of the seal 54 have been determined so that on the one hand the vanes 16 of the wheel adopt substantially the same angular position when the turbine engine is stopped and in operation, and on the other hand, so that the seal 54 does not prevent the introduction of the blade roots 18 into the groove 20 of the disk and the circumferential displacement of the blades in this groove by friction of the surfaces 48 of the platforms on the seal 54. As can be seen in FIG. 4, the seal 54 is elastically deformed between the platforms of the blades and the bottom of the groove 52 and exerts on these platforms a restoring force to ensure the correct positioning of the blades.

In an exemplary embodiment of the invention, the annular seal 54 has an outer diameter of approximately 1.20 meters, a Shore A hardness of between 50 and 100, for example approximately 75, and can withstand temperatures which can reach 150 ° C. This seal is for example made in "VITON A" or "VITON B".

In another embodiment shown in FIG. 5, the seal 62 has a section substantially in X or H and comprises two outer peripheral lips 64 which protrude outside the groove 52 to bear on the internal surfaces downstream 48 platforms of the blades, and two inner peripheral lips 66 whose upstream and downstream side surfaces 68 are substantially flat and parallel and bear against the side walls of the groove 52, when the seal 62 is mounted in the groove 52. The seal 62 is elastically deformed between the platforms of the blades and the bottom of the groove 52 and exerts on the platforms a restoring force to ensure the correct positioning of the blades.

When the seal 54 or 62 is mounted in the groove 52 of the disc, it does not occupy the entire volume of this groove, as shown in Figures 4 and 5. When the foot 18 of a blade is introduced into the groove 20 the platform 44 of this blade abuts on the seal 54, 62 which is slightly compressed inside the groove 52.

Of course, the invention is not limited to the embodiments which have been described in the foregoing and represented in FIGS. 3 to 5. For example, the seal 54 or 62 which preferably has a shape that is symmetrical with respect to its median transverse plane, may have a shape in section different from those shown.

On the other hand, the seal 54 or 62 could be mounted in an annular groove of the upstream side wall 32 of the groove, this groove opening under the upstream parts of the platforms 44 of the blades.

Claims (11)

A rotor wheel, in particular a turbomachine, comprising a disk (24) carrying vanes (16) whose feet (18) are engaged and retained in an annular groove (20) of an outer peripheral surface of the disk (24), said legs (18) being connected to platforms (44) externally surrounding the outer peripheral surface of the disc and adapted to cooperate with an annular seal (54, 62) mounted in an annular groove (52) of the surface outer periphery of the disk, characterized in that , when stationary, the annular seal (54, 62) exerts an elastic force on the platforms (44) of the blades holding the blades (16) in a correct operating position, the annular seal (54, 62) having, in the free state, an outer diameter greater than that of its mounting groove (52), and its hardness being determined to ensure the return of the vanes (16) in their correct position of operation and to authorize the circumferentially spacing the blades (16) in their annular groove (20) mounting. Wheel according to claim 1, characterized in that the annular seal (54, 62) is upstream of the vanes (16). Wheel according to claim 1, characterized in that the annular seal (54, 62) is downstream of the vanes (16). Wheel according to one of the preceding claims, characterized in that the seal (54, 62) has a symmetrical shape with respect to its median transverse plane. Wheel according to one of the preceding claims, characterized in that the seal (54, 62) comprises at least one outer peripheral lip (56, 64) intended to protrude outside the groove (52) when the seal (54, 62) is mounted in the groove. Wheel according to one of the preceding claims, characterized in that the seal (54, 62) comprises at least one inner peripheral lip (58, 66) for pressing against the bottom of the groove (52) when the seal (54, 62) is mounted in the groove. Wheel according to one of the preceding claims, characterized in that the seal (54) has a substantially diamond-shaped cross-section, whose apices form radially inner (56) and external (58) lips of the seal (54). Wheel according to one of the preceding claims, characterized in that the seal (62) has a cross-section substantially in the form of X or H. Ring seal for a rotor wheel according to one of the preceding claims, characterized in that it has, in the free state, an outer diameter greater than that of its annular groove (52) for mounting and a hardness Shore A between 50 and 100. Turbomachine compressor, comprising at least one rotor wheel according to one of Claims 1 to 8. Turbomachine, such as a turbojet engine or an airplane turboprop, characterized in that it comprises at least one rotor wheel according to one of claims 1 to 8.

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