EP2373872A2 - Turbine wheel provided with an axial retention device that locks blades in relation to a disk - Google Patents

Abstract

The present invention relates to a turbine wheel, including: a plurality of blades (14), each blade having a profile (144); a platform (142) and a clip (140); a disk (12), on the periphery of which the blades (14) are mounted, the clip of each blade being inserted into a recess (120) that opens into the periphery of the disk, and axially extending between two opposite surfaces (128, 130) of the disk, the recesses being separated by teeth (121); and a device (16) for axially retaining the blades. The disk comprises a first stopping member (126), and the platform of said blade comprises a projection (150) that axially projects beyond one of the surfaces of the disk. Said projection comprises a second stopping member (146). The axial projection, the second stopping member, and said surface of the disk form a groove that is oriented towards the disk axis (A), said groove being intended to receive the axial retention device.

Description

 Turbine wheel equipped with an axial retainer locking blades with respect to a disc.

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 industrial gas turbines and aeronautical gas turbine engines.

A turbine wheel conventionally comprises a plurality of blades, a disk and an axial blade retainer. Each blade generally has a blade profile, a platform and a fastener. At the periphery of the disk are mounted the blades, the attachment of each of the blades being engaged in a housing opening at the periphery of the disk and extending axially between two opposite faces of the disk, the housing being separated by teeth. The axial blade retainer axially locks the blades relative to the axis of rotation of the disk.

In known turbine wheels, the blades, in operation, are sometimes animated vibratory movements or vibrations. These vibrations are harmful because they can lead to dynamic instabilities of the wheel leading to the ruin of the wheel as well as premature wear of the contact zones between the different elements of the wheel.

The invention aims to provide a turbine wheel in which the blades undergo substantially less vibration during operation of the wheel.

This object is achieved thanks to the fact that in the aforementioned type of wheel, at least one of the blades abuts against a first stop member of the disk for locking said blade relative to the disk in a first axial direction. platform of said blade has a projection projecting axially beyond one of the faces of the disc, said projection comprising a second stop member, and the axial projection, the second stop member and said face of the disc form a groove oriented towards the axis of the disc, said groove being intended to receive the axial retaining device, so that the axial retaining device, in mounted position, abuts in the first axial direction against the second stop member and against said face of the disk in a second axial direction opposite to the first axial direction, whereby said blade is locked relative to the disk in the second axial direction. It is therefore understood that the axial retaining device axially locks the blade relative to the disk. Indeed, the blade is blocked axially on the one hand by the first stop member of the disk and on the other hand by the axial retaining device. The first stop member blocks the blade axially in the first axial direction, while the axial retainer blocks the blade axially in the second axial direction. By "axial" is meant a direction oriented along the axis of the wheel or disk. Of course, in the radial direction, the blade is retained in the housing by shape cooperation between the blade and two teeth of the disk, in a manner known per se.

For example and preferably, the first axial direction is that in which the blades are inserted into the disk housing while the second axial direction is that by which the blades can be removed from the disk. The platform of the blade has an axial projection comprising a second stop member. The axial projection is provided to extend axially beyond one of the faces of the disk when the blade is mounted on the disk. The second stop member is located under the platform and protrudes radially towards the axis of the disc. When the blade is mounted on the disk, said disk face, the axial projection and the second stop member form a groove oriented towards the axis of the disk. Thus, the lower face of the platform, opposite to the face bearing the blade profile, forms the bottom of the groove while said face of the disc and the second stop member form the side edges of the groove. The groove thus defined is intended to receive the axial retention device.

The axial retention device is held in the groove in the first axial direction by the second stop member and in the second axial direction by said face of the disk. The axial retention device is also maintained in the radial direction in the centrifugal direction by the bottom of the groove.

When the blade tends to move axially in the second axial direction, the second stop member abuts against the axial retention device, the latter in turn abuts against said face of the disc. Thus, the blade is retained axially in the second axial direction. In addition, upon rotation of the wheel, the centrifugal force applied to the axial retainer tends to press the axial retainer onto the bottom of the groove with increasing contact pressure with the rotational speed of the wheel. . This presents a double advantage. Firstly, this plating makes it possible to maintain the axial retention device at the bottom of the groove. Indeed, the plating ensures that the axial retention device remains properly housed in the groove between the side edges. As a result, the axial retainer can hardly disengage from the groove. In addition, this plating advantageously allows a mechanical coupling between the blade and the axial retention device. The relative flexibility of the axial retention device with respect to the rigidity of the blade and the rigidity of the disk allows a damping of the azimuthal component of the vibrations. By thus damping the vibrations of the blade, the amplitude of the displacements of the blade is reduced, so that the ruin of the blade is advantageously avoided, especially when the vibrations vibrate at the resonant frequency of the blade.

Thanks to the invention, on the one hand, the axial retention of the blades on the disk is correctly ensured and, on the other hand, the vibrations of the blade are damped.

According to an advantageous aspect of the invention, at least one boss is provided between the axial retaining device and said blade to make a mechanical contact between the blade and the axial retaining device. The presence of a boss between the blade and the axial retention device improves the mechanical contact between the blade and the axial retention device, said mechanical contact allowing damping of vibrations of the blade. In addition, this boss may possibly make it possible to slow down the possible movements of the axial retention device in an azimuthal direction, which improves the safety of the axial retention of the blades.

Alternatively, the boss is formed on the axial retainer.

According to another variant, the boss is formed under the axial projection, at the bottom of said groove, that is to say on the face which is facing the axial retaining device. Advantageously, a recess of complementary shape to the boss is formed on the element facing the boss, and formed so that the boss comes to lodge in the recess.

It is therefore understood that if the boss is formed on the axial retention device, the element facing the boss is the platform and the recess is made under the platform. Conversely, if the boss is formed under the platform, the element facing the boss is the axial retention device and the recess is formed at the axial retaining device. A recess of complementary shape to the boss makes it possible to further improve the mechanical contact between the blade and the axial retention device by combining the advantages associated with the presence of a simple boss and the advantages related to the presence of facing surfaces without boss. . Indeed, the boss allows permanent contact, and the facing surfaces being very close thanks to the recess of complementary shape to the boss allow additional contact during the rotation of the wheel due to the centrifugal force. In addition, the fact that the boss is housed in a recess, also prevents the rotation of the axial retention device. Preferably, the boss and / or the recess are made on a portion of the platform that does not radially support the blade profile.

With this arrangement of the boss relative to the blade profile, it is understood that the boss is not located near a radially supporting zone blade profile, the boss is arranged under the platform or on the retainer axial. Thus the mechanical stresses resulting from the interactions between the blade and the axial retention device are applied in an area where the platform is weakly mechanically stressed. Indeed, the areas of the platform close to the blade profile are typically substantially solicited by the blade profile.

Advantageously, the disk has an anti-rotation cleat capable of blocking the azimuthal movements of the axial retaining device with respect to the disk. An anti-rotation cleat makes it possible to ensure that the axial retaining device does not itself rotate during the rotation of Ia. wheel. In addition, thanks to the anti-rotation cleat, the axial retention device remains correctly positioned. Preferably, this anti-rotation cleat is made in such a way that it guarantees the balance of the wheel. In this case, the anti-rotation tab balances the mass of the axial retainer which is not necessarily evenly distributed over the entire wheel. Thus the assembly composed by the axial retention device and the antirotation cleat has a uniformly distributed mass on the wheel and does not imbalance when the latter rotates.

Advantageously, the disc also has at least one safety catch able to block the centripetal movements of the axial retention device.

A safety catch thus arranged makes it possible to block the axial retention device radially in the groove. The safety of the axial locking is thus further improved. Preferably, the wheel according to the invention comprises three safety catches uniformly distributed radially every 120 ° angle on the disk.

Preferably, the axial retention device is a split annular ring.

This annular ring has the advantage of being a single member for retaining all the blades on the disc. In addition, the fact that the ring is split gives it some flexibility vis-à-vis the radial deformations, which is advantageous from the point of view of damping azimuthal vibrations of the blades. Thus, the ring is advantageously elastic, which allows on the one hand damping of the vibrations of the blades, and on the other hand to facilitate the mounting operation of the latter on the wheel.

In addition, the choice of an annular ring as axial retention device allows for a simultaneous mechanical coupling of the rod with several blades. In addition to the practical aspect that the ring presents during the assembly of the wheel, the ring also achieves a satisfactory damping of the vibrations of each blade which makes it possible to avoid their ruin.

In addition, according to yet another variant, the ring is prestressed so as to be in contact with a contact pressure with the platform, which ensures the position of the ring relative to the wheel at the stop of the machine. Advantageously, the second stop member forms a spoiler and, preferably, the spoiler forms a ring portion extending over at least a portion of the azimuthal length of the axial projection of the blade platform. This preferred form of the second stop member makes it possible to distribute the axial retention forces at the platform of the blade and thus to avoid local peaks of mechanical stresses.

The present invention also relates to a turbomachine comprising a turbine wheel according to the invention. The invention and its advantages will be better understood on reading the detailed description given below of various embodiments given as non-limiting examples. This description refers to the appended figures, in which:

FIG. 1 is an overall view of a turbine wheel according to the invention,

FIG. 2A shows an exploded portion of a turbine wheel of FIG. 1, and FIG. 2B represents the same assembled turbine portion;

FIG. 3 is a sectional view along plane III of FIG. 2B,

FIG. 4 is a sectional view along plane IV of FIG. 2B,

FIGS. 5A to 5E show different embodiments of the axial retaining ring according to the sectional plane V of FIG. 4, and

- Figure 6 shows a turbine equipped with a turbine wheel according to the invention.

FIG. 1 represents an exemplary embodiment of a turbine wheel 10 according to the invention. The wheel 10 is composed of a disc 12 having an axis A, a plurality of blades 14 and an axial retaining device 16. In this example, the axial retaining device 16 is a split annular rod. In the following description of the embodiments of the invention, the term "ring" or "split ring" for "axial retention device" will be used. Each of the blades 14 has a fastener 140 in the form of a fir tree, a platform 142 and a blade profile 144. The fastener 140 is engaged in a housing 120 of the disk 12. The housing 120 extend axially between two opposite faces of the disc, and are separated by teeth 121. Each blade 14 is retained radially at its attachment 140 by the two adjacent teeth 121 at the clip. The disk 12 is equipped with three safety catches 122 arranged at 120 ° angle to each other on the disk. These safety catches 122 hold the rod 16 in its radial position with respect to the disk 12 and the blades 14. The disk 12 is also equipped with an anti-rotation cleat 124 to lock the rod 16 in its azimuthal position with respect to the disk 12 and the blades 14. The anti-rotation tab 124 is inserted into the slot of the ring 16.

Figure 2A shows an angular portion of the wheel 10 of Figure 1 exploded. In this FIG. 2A, the first stop members 126 and the second stop members 146 are visible. When the blades are mounted on the disc 12 in a first axial direction X, the first stop members 126 are housed in cavities 148 of the blades 14.

The second stop members 146 are arranged on the lower face of the platform 142 on an axial projection of the platform 150 projecting from the face 128 of the disc 12. Each second stop member 146 forms a spoiler so that when mounting a blade 14 on the disc 12 from the face 130 of the disc 12, the blade attachment 140 can slide in the housing 120 until the first stop member 126 is housed in a cavity 148 In this example, each spoiler has an additional machining on its azimuth flanges so as not to interfere with the teeth 121 during assembly. Subsequently, the term "spoiler" will be used for "second stop device".

In this example, each spoiler 146 forms a ring portion, so that when the blades 14 are mounted on the disc 12, the set of spurs 146 form a discontinuous ring. FIG. 2B represents the wheel portion described in FIG.

2A in an assembled manner. The underside of the axial projection 150, the face 128 of the disc, and the face of the spoiler 146 facing the face 128 of the disc 12 (or facing the blade attachment 140) form a groove oriented towards the axis. A record. The rod 16 is housed in this groove. The mounting of the axial retention device will be described with reference to FIGS. 3 and 4. FIG. 3 is a sectional view of the example shown in Figure 2B along the section plane III. The blade 14 of FIG. 3 is engaged in its housing 120 in the first axial direction X until one of the contact faces 152 of the platform 142 comes into abutment against the first stop member 126 of the disc 12 The blade is thus blocked in the first axial direction X.

Then, as seen in Figure 4 (section along the plane IV of Figure 2B), the rod 16 is disposed under the projection 150, between the face 154 of the blade attachment 140 which is in line with the face 128 of the disc 12, and the face 156 of the spoiler 146 which is opposite the face 154. Thus, the blade is retained axially in the second axial direction Y opposite the first axial direction X, by the spool 146 which abuts against the ring 16 which itself bears against the face 128 of the disc 12 and the first stop member 126 (see fig.3). Thus the blade is retained in the two opposite axial directions X and Y through the interaction of the axial retention device 16, on the one hand with the first stop member 126 and on the other hand with the second stop member 146.

Still with reference to FIG. 4, it will be noted that according to an advantageous aspect of the invention the platform 142 is provided with at least one boss 170. This boss 170 is on the lower face of the platform 142, and more particularly on the lower face of the axial projection 150. More specifically, considering the groove in which the rod 16 is housed, the boss 170 is formed on the bottom of this groove.

In addition, in the radial direction, the boss 170 is not disposed directly above the blade profile 144, that is to say that in the axial direction, the blade profile 144 and the boss 170 are staggered. . Indeed, the blade profile 144 is supported radially by the portion of the platform supported by piecing of the blade 140 and does not impinge on the axial projection 150. In other words, the boss 170 is not located on a part of the platform 142 which radially supports the blade profile 144.

FIGS. 5A to 5E represent different variants of ring / platform interfaces according to the section plane V of FIG. 4.

Figure 5 corresponds to the embodiment shown in Figure 4, in the same manner as in Figure 4, a single boss 170 is shown in Figure 5A. The ring / platform interface is realized by a contact between the boss 170 and the rod 16. The surface 160 of the rod 16 facing the bottom of the groove 158 is substantially smooth.

FIG. 5B represents an alternative embodiment in which, contrary to the embodiment previously described, the rod 16 has a plurality of bosses 162 positioned along the circumference of the rod (only one boss is shown) while the bottom of the groove 158 is smooth.

FIGS. 5C and 5D, respectively similar to FIGS. 5A and 5B, show bosses 170 and 162 arranged in a recess of complementary shape arranged opposite said boss. In one case, that of Figure 5C, the bosses 170 are under the platforms 142 while the rod 16 has recesses of complementary shape. In the other case, that of Figure 5D, the bosses 162 are formed on the circumference of the ring 16 while the recesses are formed in the blade platforms 142. In both cases, the ring 16 is then advantageously maintained according to the azimuthal direction by the interaction between the bosses and recesses of complementary shape.

FIG. 5E is a variant combining the simultaneous presence of bosses and recesses on the rod 16 and on the projection 150.

FIG. 6 represents a turbomachine 200 equipped with a turbine wheel according to the invention. In this example, the gas generator turbine wheel 210 and the free turbine wheel 220 are in accordance with the present invention.

Claims

REVENDICAΉONS A turbine wheel (10) comprising: a plurality of blades (14), each of the blades (14) having a profile (144), a platform (142) and a fastener (140), - A disc (12) on the periphery of which are mounted the blades (14), the fastener (140) of each of the blades (14) being engaged in a housing (120) opening at the periphery of the disk (12) and extending axially between two opposite faces (128, 130) of the disc (12), the housings (120) being separated by teeth (121) an axial retention device (16) for the blades (14) axially locking the blades (14) with respect to the disk (12), said wheel (10) being characterized in that at least one of the blades (14) abuts against a first stop member (126) of the disk (12) for locking said blade (14) with respect to the disc (12) in a first axial direction (X), in that the platform of said blade has a projection projecting axially beyond one of the faces of the disc, said projection comprising a second projection; stopper (146), and in that the axial projection (150), the second stop member (146) and the said disk face (128) form a groove oriented towards the axis of the disc (A), the said groove being intended to receive the device axial retention device (16), so that the axial retention device (16), in the mounted position, abuts in the first axial direction (X) against the second stop member (146) and against said face of the disk (128) in a second axial direction (Y) opposite the first axial direction (X), whereby said blade (14) is locked relative to the disk (12) in the second axial direction (Y). 2. Turbine wheel (10) according to claim 1, characterized in that at least one boss (162, 170) is provided between the axial retaining device (16) and said blade (14) to make a mechanical contact between the blade (14) and the axial retainer (16). 3. turbine wheel (10) according to claim 2, characterized in that at least one boss (162) is formed on the axial retainer (16). 4. Turbine wheel (10) according to claim 2 or 3, characterized in that at least one boss (170) is formed under the axial projection (150) at the bottom of said groove. 5. Turbine wheel (10) according to any one of claims 2 to 4, characterized in that a recess of complementary shape to the boss (162, 170) is formed on the element facing the boss (162, 170 ), and formed so that the boss (162, 170) is housed in the recess. 6. turbine wheel (10) according to any one of claims 2 to 5, characterized in that the boss (162, 170) and / or the recess are formed on a portion of the platform (142) which does not support radially the blade profile (144). 7. Turbine wheel (10) according to any one of claims 1 to 6, characterized in that the disk (12) has an anti-rotation cleat (124) capable of blocking the azimuthal movements of the axial retaining device (16). ) relative to the disk (12). A turbine wheel (10) according to any one of the claims 1 to 7, characterized in that the disk (12) further has at least one safety catch (122) capable of blocking the centripetal movements of the axial retention device (16). 9. Turbine wheel (10) according to any one of claims 1 to 8, characterized in that the axial retaining device is a split annular ring (16). 10. turbine wheel according to any one of claims 1 to 9, characterized in that the second stop member forms a spoiler (146). IL turbine wheel (10) according to claim 10, characterized in that the spoiler (146) forms a ring portion extending over at least a portion of the azimuthal length of the axial projection (150) of the platform ( 142) of blade (14). 12. A turbomachine (200) comprising a turbine wheel (210, 220) according to any one of claims 1 to 11.