EP1517004B1 - Rotor wheel for a turbomachine and assembly method therefor - Google Patents

Description

TECHNICAL AREA

The present invention relates generally to a turbomachine turbine wheel, of the type comprising a turbine disk and a plurality of blade segments mounted on the turbine disk.

Furthermore, the invention also relates to a method of mounting such a turbine wheel.

STATE OF THE PRIOR ART

In a conventional manner known in the prior art, a turbomachine turbine wheel comprises a turbine disk and a plurality of blades mounted on the turbine disk, each blade comprising a foot extending from a radially inner profile. and being provided with retaining shapes known as "fir fasteners".

To ensure the mounting of the blades on the turbine disc, the latter is usually provided with a series of substantially axial grooves open radially outwardly, having a shape complementary to that of the aforementioned "fir fasteners", and in which the blades can be inserted one after the other, to be maintained by the turbine disk.

Although this solution is widely used in turbines of today's turbomachines, it nevertheless has a number of major disadvantages.

Indeed, it is firstly indicated that the blade roots must necessarily be relatively bulky, as well as the complementary shapes (or teeth) of the turbine disk, in order to allow a good maintenance of these elements. compared to others, despite the high radial forces generated during the rotation of the turbine wheel. Naturally, these large volumes translate directly into weight constraints and material cost constraints. In this respect, it is also stated that the complex realization of the "fir" shapes of the vanes and the disk generates significant manufacturing costs.

On the other hand, it is obvious that with this type of solution of the prior art, a given foot can not have a high number of blades, the latter usually being less than or equal to two. This can be explained by the fact that if the number of blades belonging to one and the same foot is greater, the foot should then have a length and a thickness that are also greater, just like the notch provided for ensuring the introduction of these blades in the disc. Now in such a case, it is clear that the mass of the set "blade-disk" increases by unacceptable, with regard to the interest in reducing manufacturing costs.

In this respect and as is the case in the prior art, it is noted that the impossibility of providing segments provided with a large number of blades, and therefore to design segments of great circumferential length, gives rise to a major disadvantage. Indeed, the smaller the circumferential length of the blade segments, the greater the number of segments provided around the turbine disk is large, and therefore the number of spaces to be sealed between two directly consecutive segments is high.

Moreover, this type of embodiment does not provide a sufficiently satisfactory seal between the turbine disc on the one hand and the blade segments on the other hand, it is generally necessary to add an upstream labyrinth connected by a system of flanges. to the turbine disk. The upstream labyrinth thus makes it possible, while playing an axial stopping role of the turbine blades in their fasteners, to protect the cooling circuit of the blades from the inadvertent crossing of the hot gases coming from the turbine duct, which could pass through the turbine wheel. turbine by borrowing the existing gap between the disk and the blades. Indeed, in known manner, the addition of the upstream labyrinth greatly limits the passage of cooling air between the turbine disk and the blade segments, through its participation in the creation of an intermediate upstream chamber allowing the feeding the blades with cooling air.

However, the upstream labyrinth required is a bulky piece, high mass and extremely complex to achieve, so that its presence is certainly a disadvantage largely detrimental, especially in terms of additional costs generated.

STATEMENT OF THE INVENTION

The object of the invention is therefore to propose a turbomachine turbine wheel comprising a turbine disc as well as a plurality of blade segments mounted on this turbine disk, and at least partially overcoming the aforementioned drawbacks relating to turbines. achievements of the prior art.

On the other hand, the invention also aims to present a method of mounting such a turbine wheel.

To do this, the invention firstly relates to a turbomachine turbine wheel comprising a turbine disk and a plurality of blade segments mounted on the turbine disk, each blade segment comprising a foot as well as at least one dawn attached to the foot. The turbine disk comprises an upstream wing and a downstream wing each extending substantially annularly about a longitudinal main axis of the wheel and radially to a radial end of the disk, each blade segment mounted on the disk turbine being able to be retained by the latter in a radial outer direction by means of upstream engagement means belonging to the foot and able to cooperate with complementary upstream engagement means constituting a radial end external of the upstream wing, and with the aid of downstream engagement means also belonging to the foot and adapted to cooperate with complementary downstream engagement means constituting an outer radial end of the downstream wing. In addition, the upstream and downstream wings of the turbine disk are designed to be able to be brought from a position spaced commitment to a close position, and vice versa, to allow mounting of each blade segment on the turbine disk. According to the invention, at least one of the upstream and downstream wings is elastically designed so that the passage of these wings from the spaced apart position to the close position and the transition from the close position to the spaced apart position can respectively be operated by exerting pressure on the wings, and releasing the pressure exerted.

Advantageously, the specific design of the turbine wheel according to the invention is such that the assembly of the blade segments on the turbine disk is carried out by performing in particular a simple approximation of the upstream and downstream wings allowing a set up of these segments. Indeed, the turbine disk is advantageously designed so that when the upstream and downstream wings occupy their close position, the complementary upstream and downstream engagement means are sufficiently clear of the location they occupy when the upstream and downstream wings are in the open position of engagement, to allow a placement of the segments, by insertion into each other of each blade segment and the turbine disk.

In other words, in the close position, the complementary upstream and downstream engagement means are sufficiently close together so that when the blade segments are inserted into the turbine disk by a radial displacement thereof inwardly of the wheel, they do not form a stop for the upstream and downstream engagement means belonging to the legs of the segments. Consequently, the blade segments can each be moved freely radially relative to the turbine disk, without being impeded by the complementary upstream and downstream engagement means, which are respectively further downstream than the upstream engagement means of the segments. of blades, and more upstream than the downstream engagement means of these same segments.

In addition, once all the blade segments have been put in place on the turbine disk, the upstream and downstream wings can again be brought into their spaced engagement position, in which the upstream and downstream engagement means Further downstream are then able to fulfill their primary function, namely, in combination with the upstream and downstream engagement means, to ensure the radial outward restraint of each blade segment with respect to the turbine disk.

As such, it is specified that the turbine wheel according to the invention is such that the mounting of the blade segments on the turbine disk can be completed as soon as the upstream and downstream wings are brought in their outset commitment position after being reconciled, or further subsequent operations as will be discussed in detail below.

In the first case where the assembly of the segments is completed when the upstream and downstream wings are brought into their spaced engagement position, the configuration of the various engagement means may be such that the simple movement of the upstream and downstream wings in the position spread of commitment, causes the automatic commitment of these engagement means. In other words, once the upstream and downstream wings occupy their disconnected position of engagement, the upstream and downstream engagement means of the blade segments cooperate respectively with the complementary upstream and downstream engagement means of the rotor disk. turbine, and the blade segments are automatically blocked in the outer radial direction relative to the disk. It is noted that this configuration can in particular be obtained by providing engagement means ensuring not only a blocking of the blade segments in the outer radial direction, but also a locking of these segments in the internal radial direction relative to the disk of turbine. This makes it possible to prevent the upstream and downstream engagement means of some of these blade segments from being disengaged by gravity from the complementary upstream and downstream engagement means. Under these conditions, once mounted, the blade segments therefore have no freedom of radial displacement relative to the turbine disk.

Conversely, it can also provide a configuration in which when the segments are in a mounted state, the latter being obtained by a simple movement of the upstream and downstream wings in the engagement position, the blade segments can move radially in a limited manner relative to the turbine disk, still being able to be retained in the outer radial direction through the various engagement means. In this way, especially when the wheel is not rotating, the upstream and downstream engagement means of certain blade segments do not cooperate with the complementary upstream and downstream engagement means of the turbine disk, due to the gravity implying that these segments concerned are in radial internal abutment against the turbine disk, therefore opposite to the position in which they are retained in the outer radial direction by the same turbine disk. Thus, in this configuration, it is only when the wheel is rotated that the centrifugal force generated causes the engagement and cooperation between the upstream and downstream engagement means of all the blade segments, and the means complementary upstream and downstream engagement of the turbine disk. Under these dynamic conditions, these complementary upstream and downstream engagement means of the turbine disk thus effectively act as an external radial abutment for the upstream and downstream engagement means of the blade segments.

In the second case where the assembly of the segments takes place not only by bringing the wings upstream and downstream in their excluded commitment position, but also and carrying out the implementation of additional operations, it is indicated that the latter may be intended to obtain permanent cooperation between the upstream and downstream commitment means all of the blade segments and the complementary upstream and downstream engagement means of the turbine disk, as will be discussed in detail later.

Thus, whatever the configuration adopted for the turbine wheel according to the invention, it generates almost no restriction as to the maximum number of blades to be provided on each segment. This therefore makes it possible to considerably reduce the number of these blade segments, and therefore also the number of spaces to be sealed between two segments of directly consecutive blades, compared to that encountered in the embodiments of the prior art. The overall sealing of the turbine wheel is naturally significantly improved.

In addition, the possibility of reducing the number of segments by providing a plurality of blades on each of them generates a significant reduction in production and assembly costs.

Finally, it is stated that the provision on the one hand of a cooperation between the upstream commitment means and the complementary upstream commitment means, and on the other hand between the downstream commitment means and the commitment means complementary downstream, makes it possible to provide upstream and downstream seals which are quite satisfactory between the turbine disk and vane segments, so that it is no longer necessary to provide upstream labyrinth to supply cooling air blades.

Of course, this removal also allows to greatly reduce the production costs of the turbine wheel.

Preferably, each of the upstream and downstream wings of the turbine disk is elastic. In this way, by designing the turbine wheel so that the spread position of engagement of these wings corresponds to a rest position, it is then easily possible to bring these wings from the position of engagement away to the close position by applying a simple effort on the latter, so as to generate a deformation of these same wings. In addition, as mentioned above, the return to the spread position of commitment is then automatically released releasing the force exerted, because of the elasticity of these wings.

Of course, it would also be possible to provide only one of the two upstream and downstream wings are designed to deform following the application of the effort required to obtain the close position, without departing from the scope of the invention.

Preferably, the complementary upstream and downstream engagement means extend annularly around the longitudinal main axis of the wheel, and the upstream and downstream engagement means of each blade segment foot are each made of to form an annular portion of the same axis, extending circumferentially all along the foot of the blade segment. Therefore, because of the long circumferential length of cooperation between the various engagement means, it is possible to obtain a mechanical maintenance of the blade segments very efficient and easily resistant to the radial forces generated during the rotation of the wheel of turbine. Furthermore, this arrangement also makes it possible to ensure a very satisfactory seal between, on the one hand, the blade segments, and on the other hand the turbine disk.

Preferably, the complementary upstream and downstream engagement means as well as the upstream and downstream engagement means of the foot of each blade segment each have a hook-shaped longitudinal section, this shape being entirely adapted to ensure a blockage in the outer radial direction.

Indeed, it is then possible to provide that the complementary upstream engagement means have a longitudinal hook-shaped section projecting upstream and defining an engagement opening substantially oriented radially towards the inside of the wheel, that the upstream engagement means have a hook-shaped longitudinal section projecting downstream and defining a substantially radially outwardly oriented engagement opening of the wheel, that the complementary downstream engagement means have a longitudinal section; hook-shaped projecting downstream and defining an opening engagement member substantially oriented radially towards the inside of the wheel, and finally that the downstream engagement means have a hook-shaped longitudinal section projecting upstream and defining a substantially radially oriented engagement opening towards the outside the wheel.

Under these conditions, once the segments are put in place and the upstream and downstream wings are again brought into the open engagement position, this preferred solution makes it possible to obtain engagement and then cooperation between the various engagement means by simple movement. relative radial between each of the blade segments and the turbine disk. Naturally, for each blade segment, radial relative movement is preferably performed by moving this segment in the outer radial direction while holding the fixed disk.

Still preferably, each blade segment further comprises holding means for ensuring, when cooperating with the turbine disk, a permanent cooperation between the upstream and downstream engagement means of the assembled blade segment. on the turbine disk, and respectively complementary upstream and downstream engagement means of the same turbine disk. In this way, the permanent cooperation between the various engagement means advantageously makes it possible to maintain the segments of blades fixed with respect to the turbine disk, and thus to obtain a precise radial and circumferential indexing of each of these blade segments. relative to the turbine disk.

To do this, it can be provided that the holding means comprise at least one flexible blade belonging to the foot and a free end of which is able to bear on the turbine disk, each of these flexible blades being then accosted on the disk only after that the upstream and downstream wings have been brought back to their spaced engagement position, and the corresponding blade segment having been radially biased outwardly to bear on the complementary engagement means of the disk.

Preferably, the upstream and downstream wings of the turbine disk define between them an annular space arranged around the longitudinal main axis of the wheel, this annular space communicating with cooling passages provided on the blade segments of the feet. In addition, the upstream wing of the turbine disk has at least one injection hole passing through it and opening inside the annular space, each injection hole being intended to cooperate with a cooling air injector. of the turbomachine.

Still preferentially, the turbine disk is monobloc.

• amener les ailes amont et aval du disque de turbine dans la position rapprochée ;
• positionner chaque segment d'aubes par rapport au disque de turbine de sorte que lorsque les ailes amont et aval du disque de turbine sont à nouveau amenées dans leur position écartée d'engagement, les moyens d'engagement amont et aval du pied de chaque segment d'aubes soient en mesure de s'engager respectivement avec les moyens d'engagement amont et aval complémentaires du disque de turbine ; et
• amener les ailes amont et aval du disque de turbine dans leur position écartée d'engagement.

On the other hand, the invention also relates to a method of mounting a turbine wheel such as that just described and also object of the present invention, this method comprising the following successive steps consisting of:

• bringing the upstream and downstream wings of the turbine disk into the close position;
• positioning each vane segment relative to the turbine disk so that when the upstream and downstream wings of the turbine disk are again brought into their spaced engagement position, the upstream and downstream engagement means of the foot of each segment blades are able to engage respectively with the complementary upstream and downstream engagement means of the turbine disk; and
• bringing the upstream and downstream wings of the turbine disk into their spaced engagement position.

The steps of bringing the upstream and downstream wings of the turbine disk into the close position and bringing the upstream and downstream wings of the turbine disk into their spaced apart engagement position respectively by exerting pressure on the upstream wings and downstream using appropriate tools, and releasing the pressure exerted.

Of course, as mentioned above, in the step of positioning each vane segment with respect to the turbine disk, it should be understood that the various engagement means must be able to engage either directly during the step of bringing the upstream and downstream wings back into their spaced engagement position, either following a rotation of the wheel, or following the implementation of subsequent operations as will be explained more precisely below.

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

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente une vue en demi-coupe longitudinale d'une roue de turbine selon un premier mode de réalisation préféré de la présente invention, cette roue de turbine étant représentée à l'état monté ;
• la figure 2 représente une vue partielle en perspective de la roue de turbine représentée sur la figure 1 ;
• la figure 3 représente une vue partielle agrandie de la figure 1 ;
• la figure 4 représente une vue partielle en demi-coupe longitudinale d'une roue de turbine selon un second mode de réalisation préféré de la présente invention, cette roue de turbine étant représentée à l'état monté ;
• la figure 5 représente une vue partielle en demi-coupe longitudinale d'une roue de turbine selon un troisième mode de réalisation préféré de la présente invention, cette roue de turbine étant représentée à l'état monté ; et
• les figures 6a à 6d illustrent diverses étapes d'un procédé de montage selon un mode de réalisation préféré de la présente invention, de la roue de turbine représentée sur les figures 1 et 2.

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

• the figure 1 represents a longitudinal half-sectional view of a turbine wheel according to a first preferred embodiment of the present invention, said turbine wheel being shown in the assembled state;
• the figure 2 is a partial perspective view of the turbine wheel shown in FIG. figure 1 ;
• the figure 3 represents an enlarged partial view of the figure 1 ;
• the figure 4 is a partial longitudinal half-sectional view of a turbine wheel according to a second preferred embodiment of the present invention, said turbine wheel being shown in assembled state;
• the figure 5 is a partial longitudinal half-sectional view of a turbine wheel according to a third preferred embodiment of the present invention, said turbine wheel being shown in assembled state; and
• the Figures 6a to 6d illustrate various steps of a mounting method according to a preferred embodiment of the present invention, of the turbine wheel shown in FIGS. figures 1 and 2 .

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference jointly to figures 1 and 2 , there is shown a turbine wheel 1 for turbomachine, according to a first preferred embodiment of the present invention.

The turbine wheel 1, of longitudinal main axis 2, comprises a turbine disk 4, preferably one-piece, as well as a plurality of blade segments 6 mounted on the disk 4, only one of these segments 6 being represented on the figure 2 .

Each blade segment 6 comprises a foot 8 extended radially outwards by a blade 10, or preferably by several blades 10. As an example, each segment 6 is provided with three blades 10 integral with a part external radial 11 of the foot 8, this portion 11 of the metal plate type optionally variable thickness can for example take substantially the shape of an angular sector of a cylindrical geometry axis identical to the longitudinal main axis 2. Moreover , the turbine wheel 1 may be designed to have about twenty segments 6 of three blades 10, these segments 6 being evenly distributed around the longitudinal main axis 2 and mounted on the turbine disk 4. In addition, each space (not shown) between two segments directly consecutive 6 is sealed in a conventional manner, using means known to those skilled in the art.

The turbine disc 4 comprises an internal body 12, preferably of the solid body type, or more conventionally pierced with a central hole if necessary to pass a low pressure turbine shaft for example, this inner body 12 being centered on the axis main longitudinal 2. The inner body 12 is extended radially outwards on the one hand by an upstream wing 14a, and on the other by a downstream wing 14b. As can be seen clearly on the figure 1 , the upstream and downstream flanges 14a and 14b each extend substantially annularly around the longitudinal main axis 2 of the wheel 1, and each extend radially to a radial end of the disc 4.

Naturally, throughout the description, the terms "upstream" and "downstream" are defined with respect to a main direction of gas flow through the turbine wheel 1, this direction being shown schematically by the arrow Dp on the figure 1 .

Preferably, the upstream and downstream wings 14a and 14b are both resilient, so that they can be easily moved from a position of engagement away as shown in FIGS. figures 1 and 2 at a close position, and vice versa. This specificity allows to allow the assembly of the blade segments 6 on the disc 4 monobloc, as will be explained in more detail later.

In the assembled state shown on figures 1 and 2 , the blade segments 6 are not only retained in an external radial direction indicated schematically by the arrow Re, but also retained in an internal radial direction indicated schematically by the arrow Ri. In this way, as will become clearer in the rest of the description, the specificity of this first mode of The preferred embodiment of the present invention resides in the fact that the blade segments 6 have no freedom of radial displacement with respect to the turbine disk 4.

To ensure the retention of the blade segments 6 by the turbine disk 4 in the outer radial direction Re, it is provided that each segment 6 comprises upstream engagement means 16a and 16b downstream engagement means, ci extending radially inwardly from the portion 11 of the foot 8, to which they are secured. These upstream engagement means 16a and downstream 16b respectively cooperate with complementary upstream engagement means 18a constituting a radial outer end of the upstream wing 14a, and with complementary downstream engagement means 18b constituting an outer radial end of the downstream wing 14b. Of course, it is understood by the term "cooperate" that the various engagement means 16a, 16b, 18a and 18b effectively provide retention, in the outer radial direction Re, of each segment 6 with respect to the disc 4. By therefore, in the mounted state in which the various engagement means 16a, 16b, 18a and 18b cooperate with each other, the blade segments 6 are in radial outer abutment against the turbine disc 4, and these segments 6 do not can not move in the external radial direction Re with respect to this same disk 4.

With reference to the figure 3 , we can see in more detail the various means of engagement 16a, 16b, 18a and 18b, when they cooperate with each other.

In this first preferred embodiment of the present invention, it can be seen that the complementary upstream engagement means 18a and the complementary downstream engagement means 18b, as well as the upstream and downstream engagement means 16a of the foot 8 of each blade segment 6, each have a hook-shaped longitudinal section.

More specifically, the complementary upstream engagement means 18a have a hook-shaped longitudinal section projecting upstream. In other words, the complementary upstream engaging means 18a project upstream relative to the rest of the upstream wing 14a. In addition, these means 18a define an engagement opening 20a substantially oriented radially towards the inside of the wheel 1, as clearly shown on the figure 3 .

Preferably, always in longitudinal section, the free end 22a of the hook points radially towards the inside of the wheel 1.

Furthermore, for each blade segment 6 of the wheel 1, the upstream engagement means 16a also have a hook-shaped longitudinal section, the latter projecting downstream. In addition, these means 16a define an engagement opening 24a substantially oriented radially outwardly of the wheel 1. Always preferably and in longitudinal section, the free end 26a of hook points radially outward of the wheel 1.

Thus, in the mounted state corresponding to a state in which the complementary upstream engaging means 18a cooperate with the upstream engaging means 16a of each of the blade segments 6, the free end 22a passes through the opening of engagement 24a and is in contact with a hook bottom 28a of upstream engagement means 16a. In the same way, the free end 26a passes through the engagement opening 20a and is in contact with a hook bottom 30a complementary upstream engaging means 18a. For practical reasons of manufacture, it could be decided to favor one or other of the contacts 28a or 30a, without departing from the scope of the invention.

Consequently, the complementary upstream engagement means 18a preferably extending annularly around the longitudinal main axis 2 of the wheel 1, and the upstream engagement means 16a of each blade segment 6 being each made of so as to form an annular portion of the same axis extending circumferentially along the foot 8 along a circumferential length L, it is then possible to obtain a particularly satisfactory upstream seal. Indeed, it is noted that the centrifugal force generated during the rotation of the wheel 1 causes a significant pressure on the one hand between the free end 26a and the hook bottom 30a, and / or on the other hand between the free end 22a and hook bottom 28a. In both cases, the observed support is substantially circumferential axis identical to the longitudinal main axis 2, and therefore strongly contributes to obtaining an upstream tightness perfectly adapted to the needs encountered.

Similarly, the complementary downstream engagement means 18b have a hook-shaped longitudinal section projecting downstream. In other words, the complementary downstream engagement means 18b projects downstream from the rest of the downstream wing 14b. In addition, these means 18b define an engagement opening 20b substantially oriented radially towards the inside of the wheel 1, as is clearly apparent on the figure 3 .

Preferably and always in longitudinal section, the free end 22b of the hook points radially towards the inside of the wheel 1.

Furthermore, for each blade segment 6 of the wheel 1, the downstream engagement means 16b also have a hook-shaped longitudinal section, the latter protruding upstream. In addition, these means 16b define an engagement opening 24b substantially oriented radially outwardly of the wheel 1. Always preferably and in longitudinal section, the free end 26b of the hook points radially outwardly of the wheel 1.

Thus, in the mounted state corresponding to a state in which the complementary downstream engagement means 18b cooperate with the downstream engagement means 16b of each of the blade segments 6, the free end 22b passes through the engagement opening 24b and is in contact with a hook bottom 28b of the downstream engagement means 16b. In the same way, the free end 26b passes through the engagement opening 20b and is in contact with a hook bottom 30b complementary downstream engagement means 18b. Here again, for practical reasons of manufacture, it could be decided to favor one or other of the contacts 28a or 30a, without departing from the scope of the invention.

Consequently, the complementary downstream engaging means 18b also preferably extending annularly around the longitudinal main axis 2 of the wheel 1, and the downstream engaging means 16b of each blade segment 6 being each made so as to form an annular portion of the same axis extending circumferentially along the foot 8 to a circumferential length identical to that of the upstream engagement means 16a, it is thus possible to obtain a particularly satisfactory downstream seal. This is always due to the centrifugal force generated during the rotation of the wheel 1, causing a significant pressure on the one hand between the free end 26b and the hook bottom 30b, and on the other hand between the free end 22b and hook bottom 28b.

To ensure permanent cooperation between the various engagement means 16a, 16b, 18a and 18b, therefore permanent contact between the free ends 22a, 22b, 26a and 26b and respectively the hook bases 28a, 28b, 30a and 30b, each segments blade 6 of the turbine wheel 1 also has holding means 32a and 32b ensuring the retention of these segments 6 in the internal radial direction Ri.

Indeed, again with reference to figures 1 and 2 , the holding means 32a of each segment 6 take the form of an upstream flexible blade, the latter extending radially towards the inside of the wheel 1. Preferably, the upstream flexible blade 32a has an integral end of the upstream engagement means 16a of the segment 6, and a free end 34a having a notch 36a. Thus, in the assembled state shown on figures 1 and 2 a nipple 38a integral with the upstream flange 14a and projecting from it upstream, is inserted into the bottom of the notch 36a open radially towards the inside of the wheel 1. Therefore, the nipple 38a thus provides the function of internal radial abutment for the segment 6 concerned.

Similarly, the holding means 32b of each segment 6 take the form of a downstream flexible blade, the latter extending radially towards the inside of the wheel 1. Preferably, the downstream flexible blade 32b has a integral end of the downstream engagement means 16b of the segment 6, and a free end 34b having a notch (not referenced). Thus, in the mounted state, a pin 38b integral with the downstream flange 14b and projecting from it downstream, is inserted into the bottom of the notch open radially towards the inside of the wheel 1 Therefore, the pin 38b therefore ensures also the internal radial stop function for the segment 6 concerned.

Preferably and as is clear from the figures, the upstream flexible blades 32a and downstream 32b may be respectively connected to the upstream engagement means 16a and the downstream engagement means 16b, at a portion of these means 16a and 16b defining the hook funds 28a and 28b. In other words, the junction between the flexible blades 32a and 32b and the engagement means 16a and 16b is effected at a portion of these means 16a and 16b located radially towards the inside of the wheel. turbine 1.

In this way, when the flexible blades 32a and 32b are put in place, the contact obtained between the various engagement means 16a, 16b, 18a and 18b and the contact between the free ends 34a, 34b and the pins 38a, 38b , makes it possible to achieve precise radial and circumferential indexing of each of the blade segments 6 with respect to the turbine disk 4.

In this first preferred embodiment, the upstream and downstream flanges 14a and 14b define, when they occupy their spaced engagement position, an annular space 40 arranged around the longitudinal main axis 2. This annular space 40, radially outwardly, therefore communicates with cooling passages 42 provided on the foot 8 of the blade segments 6, and more precisely on the outer radial portion 11 of the same foot.

Furthermore, the upstream flange 14a has at least one injection hole 44 therethrough and opening into the annular space 40. In this way, each injection hole 44 is intended to cooperate with an injection system. injection of cooling air of the turbomachine (not shown), it is therefore easily possible to cool the blades 10 without requiring an upstream labyrinth. Indeed, the cooling air ejected from the injectors can then successively borrow the injection holes 44, the annular space 40, then the cooling passages 42 communicating with a cooling circuit (not shown) formed inside the vanes 10.

With reference to Figures 6a to 6d various steps of a method of mounting according to a preferred embodiment of the present invention of the turbine wheel 1 which has just been described are shown.

Referring first to the figure 6a it can be seen that a first step of this method consists in bringing the upstream 14a and downstream wings 14b from the engaged engagement position to the close position. This is done using appropriate tools schematically represented by the numerals 46, and whose function is to exert pressure on the upstream wings 14a and downstream 14b of the monobloc disk 4, so that they deform and get closer to each other. Preferably, the two wings 14a and 14b are each subjected to a pressure distributed annularly around the main axis longitudinal 2, and respectively applied on an upstream face of the upstream wing 14a and on a downstream face of the downstream wing 14b.

The close position is obtained when the complementary upstream engagement means 18a and complementary downstream engagement means 18b are sufficiently clear of the location they occupy when the upstream wings 14a and downstream 14b are in the engaged position , to allow placement of the segments 6 by insertion into each other of each blade segment 6 and the turbine disk 4.

Indeed, a next step is to set up the various segments 6 with respect to the turbine disk 4, as shown in FIG. figure 6b . The positioning is preferably carried out by moving each of the segments 6 radially towards the inside of the wheel 1, so that complementary complementary upstream 18a and complementary downstream engagement means 18b are inserted inside these same segments. 6, without being impeded by the upstream engagement means 16a and downstream 16b. In such a case, for each blade segment 6, the complementary engagement means 18a and 18b can therefore easily be introduced into a space delimited jointly by the upstream engagement means 16a, the downstream engagement means 16b, and the outer radial portion 11 of the foot 8 of the segment 6 concerned.

In addition, this placing step is completed only when the segments 6 have been placed sufficiently radially inwards by relative to the disc 4, so that when the upstream wings 14a and downstream 14b are again brought into their spaced engagement position, the upstream engagement means 16a and downstream 16b of the foot 8 of each segment 6 are able to s' respectively engage with complementary upstream engaging means 18a and complementary downstream 18b of the turbine disk 4, during a relative radial displacement of these various elements.

By way of illustrative example, it is possible to provide that this placing step only ends when the complementary engagement means 18a and 18b have come into contact with the part 11 of the foot 8 of each segment 8, as shows it figure 6b . In this way, the complementary engagement means 18a and 18b then fulfill an internal radial abutment function for the segments 6, indicating that the vane segments 6 are indeed correctly put in place.

It is then proceeded to a step of bringing the upstream flanges 14a and downstream 14b into the spaced engagement position, by simply releasing the pressure exerted on these same flanges by means of the appropriate tooling 46.

In this excluded position of commitment, as can be seen on the Figure 6c the free ends 22a, 22b, 26a and 26b are respectively opposite and at a distance from the engagement openings 24a, 24b, 20a and 20b, and the complementary engagement means 18a and 18b are preferably always in contact with the external radial portion 11 of the feet 8. Furthermore, see on this Figure 6c that the flexible blades 32a and 32b are respectively pressed against the end of the pins 38a and 38b, but that they do not yet cooperate with the notches 36a because of the radial offset existing at this time of the implementation of the method.

The next step of this mounting method may then be to move each of the blade segments 6 in the outer radial direction Re with respect to the disk 4, so as to ensure engagement between the various engagement means. 16a, 16b, 18a and 18b, that is to say to cause the introduction of the free ends 22a, 22b, 26a and 26b respectively into the engagement openings 24a, 24b, 20a and 20b.

Of course, as shown on the figure 6d this radial displacement is stopped by the cooperation between the various engagement means 16a, 16b, 18a and 18b, namely by the coming into contact of the free ends 22a, 22b, 26a and 26b respectively with the hook funds 28a, 28b, 30a and 30b.

Finally, if we have taken the precaution, during this radial displacement operation, circumferentially preposition each of the segments 6 so that the radial direction of the flexible blades 32a and 32b coincides with that of the pins 38a and 38b associated, then at the end of displacement, these pins 38a and 38b will automatically come to be housed at the bottom of the notches due to the elasticity of the flexible blades 32a and 32b, as can be seen in FIG. figure 6d . Naturally, the cooperation between these notches 36a (not referenced on the figure 6d ) and the pins 38a and 38b ensures a circumferential and radial indexing of the segments 6, as well as the blocking of the latter with respect to the turbine disk 4.

On the other hand, it is specified that it is from this moment that the assembly of the blade segments 6 on the turbine disk 4 is completed. Nevertheless, the method of mounting the wheel 1 may comprise conventional preliminary or subsequent steps, such as those for sealing the various spaces formed between the blade segments 6, for example by introducing sealing tongues 39 such as represented on the figure 2 , at the level of the foot 8 and between two consecutive segments of blades 6. This step is of course implemented before proceeding to the final indexing of these segments 6 on the disk 4.

Referring now to figures 4 and 5 it is partially shown turbine wheels 100 and 200 for turbomachine, respectively according to a second and a third preferred embodiments of the present invention.

The common point between these two preferred embodiments lies in the fact that the assembly of the blade segments 6 on the turbine disc 4 is completed as soon as the upstream wings 14a and downstream 14b have been brought back to their engaged engagement position. , the assembly therefore not requiring a step of radial displacement of the segments 6, as previously described for the first embodiment prefer. Of course, following the repositioning of the upstream wings 14a and downstream 14b in their separated engagement position, and therefore as soon as the assembly of the segments 6 on the disk 4 is completed, it is naturally possible to perform the conventional steps finishes such as those for sealing the various spaces formed between the blade segments 6.

Thus, the turbine wheel 100 according to the second preferred embodiment shown in FIG. figure 4 is substantially similar to the wheel 1 according to the first preferred embodiment described above. The main difference is that the segments 6 of the wheel 100 do not have holding means to obtain permanent cooperation between the various engagement means 16a, 16b, 18a and 18b, the latter being moreover substantially identical to those described for the turbine wheel 1. In this way, as can be seen clearly on the figure 4 , in the assembled state and when the wheel 1 is not in rotation, some segments are in internal radial abutment against the complementary engagement means 18a and 18b, due to gravity. Consequently, it is only when the wheel 1 is rotated that the centrifugal force generated causes the engagement and then the cooperation between the upstream and downstream engagement means 16a and 16b of the totality of the blade segments 6, and the complementary upstream engagement means 18a and complementary downstream 18b of the turbine disk 4.

Naturally, this solution is less advantageous than that of the first preferred embodiment, insofar as it is not possible to obtain a precise radial and circumferential indexing of the segments 6 with respect to the disk 4.

The turbine wheel 200 according to the third preferred embodiment shown in FIG. figure 5 differs from the turbine wheels 1 and 100 in that the repositioning of the upstream wings 14a and downstream 14b in their spaced engagement position simultaneously causes engagement and cooperation between the various engagement means 16a, 16b, 18a and 18b. In addition, these various engagement means 16a, 16b, 18a and 18b are designed so that when they cooperate with each other, they ensure the retention of the segments 6 relative to the disk 4 in the outer radial direction Re, as well as in the internal radial direction Ri. The blade segments 6 therefore do not require holding means such as those described for the turbine wheel 1.

To do this, as shown on the figure 5 , the upstream engagement means 16a and downstream 16b may each comprise an annular groove 48a and 48b respectively open downstream and open upstream. In addition, the complementary engagement means 18a and 18b may each be provided with an annular projection 50a and 50b respectively protruding upstream and downstream, and having a shape complementary to that of the annular grooves 48a and 48b so as to be properly maintained. With such an arrangement, the engagement means 16a, 16b, 18a and 18b therefore no longer require the shape of a hook in longitudinal section.

Of course, various modifications may be made by those skilled in the art to the turbine wheels 1, 100, 200 and the mounting method which have just been described, by way of non-limiting examples only.

Claims (12)

1. Turbine wheel (1,100,200) for a turbomachine comprising a turbine disk (4) and several blade segments (6) installed on the said turbine disk (4), each blade segment (6) comprising a root (8) and at least one blade (10) fixed to the said root (8), the turbine disk (4) comprising an upstream rib (14a) and a downstream rib (14b) each extending approximately in the annular direction around a longitudinal principal axis (2) of the wheel and radially as far as a radial end of the disk (4), each blade segment (6) installed on the turbine disk (4) possibly being retained by the turbine disk in an external radial direction (Re) using upstream engagement means (16a) forming part of the root (8) and capable of cooperating with complementary upstream engagement means (18a) forming an external radial end of the upstream rib (14a), and downstream engagement means (16b) also forming part of the root (8) and capable of cooperating with complementary downstream engagement means (18b) forming an external radial end of the downstream rib (14b), the upstream rib (14a) and downstream rib (14b) of the turbine disk (4) being designed so that they can be moved from a separated engagement position to a close position, and vice versa, so that each blade segment (6) can be assembled on the turbine disk (4), characterised in that at least either the upstream rib (14a) or the downstream rib (14b) is designed elastically such that these ribs (14a, 14b) can be moved from the separated position to the close position and from the close position to the separated position by respectively applying a pressure on the ribs (14a, 14b), and releasing the applied pressure.
2. Turbine wheel (1,100,200) according to claim 1, characterised in that each of the upstream rib (14a) and downstream rib (14b) of the turbine disk (4) is elastic.
3. Turbine wheel (1,100,200) according to claim 1 or claim 2, characterised in that the complementary upstream and downstream engagement means (18a,18b) extend in an annular arrangement around the main longitudinal axis (2) of the wheel, and in that the upstream and downstream engagement means (16a, 16b) of each root (8) of the blades segment (6) are made so that each forms an annular portion of the same axis, extending circumferentially around the entire root (8) of the blade segment (6).
4. Turbine wheel (1,100) according to any one of the previous claims, characterised in that the complementary upstream and downstream engagement means (18a,18b), and the upstream and downstream engagement means (16a, 16b) of the root (8) of each blade segment (6), have a hook-shaped longitudinal section.
5. Turbine wheel (1,100) according to claim 4, characterised in that the complementary upstream engagement means (18a) have a hook-shaped longitudinal section projecting in the upstream direction and defining an engagement opening (20a) oriented approximately in the inwards radial direction into the said wheel, in that the upstream engagement means (16a) have a hook-shaped longitudinal section projecting in the downstream direction and defining an engagement opening (24a) oriented approximately radially outwards from the said wheel, in that the complementary downstream engagement means (18b) have a hook-shaped longitudinal section projecting towards the downstream direction and defining an engagement opening (20b) oriented in approximately the inwards radial direction of the said wheel, and finally, in that the downstream engagement means (16b) have a hook-shaped longitudinal section projecting in the upstream direction and defining an engagement opening (24b) oriented approximately in the outwards radial direction from the said wheel.
6. Turbine wheel (1) according to any one of the previous claims, characterised in that each blade segment (6) comprises also holding means (32a, 32b) for maintaining permanent cooperation between the upstream and downstream engagement means (16a,16b) of the blade segment (6) installed on the turbine disk (4), and the corresponding complementary upstream and downstream engagement means (18a,18b) of this turbine disk (4), when they cooperate with the turbine disk (4).
7. Turbine wheel (1) according to claim 6, characterised in that for each blade segment (6), the holding means comprise at least one flexible strip (32a, 32b) forming part of the root (8) and for which a free end (34a, 34b) is designed to bear on the turbine disk (4).
8. Turbine wheel (1,100,200) according to any one of the previous claims, characterised in that the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) define an annular space (40) between them arranged around the main longitudinal axis (2) of the wheel, the said annular space (40) communicating with cooling passages (42) provided on the roots (8) of the blade segments (6).
9. Turbine wheel (1,100,200) according to claim 8, characterised in that the upstream rib (14a) of the turbine disk (4) has at least one injection hole (44) passing through it and opening up inside the annular space (40), each injection hole (44) being designed to cooperate with a cooling air injector of the turbomachine.
10. Turbine wheel (1,100,200) according to any one of the previous claims, characterised in that each blade segment (6) of the said wheel comprises at least two blades (10) fixed to the root (8).
11. Turbine wheel (1, 100, 200) according to any one of the previous claims, characterised in that the said disk (4) is single-piece.
12. Method for installing a turbine wheel (1,100,200) according to any one of the previous claims, characterised in that it comprises the following successive steps consisting of:

    - bringing the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) into the close position;

    - positioning each blade segment (6) with respect to the turbine disk (4) such that when the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) are once again brought into their separated engagement position, the upstream and downstream engagement means (16a,16b) of the root (8) of each blade segment (6) are capable of engaging with the complementary upstream and downstream engagement means (18a,18b) of the turbine disk (4) ; and

    - bringing the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) into their separated engagement position,

    the steps consisting of bringing the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) into the close position and bringing the upstream rib (14a) and the downstream rib (14b) of the turbine disk (4) into their separated engagement position being made by applying pressure on the upstream rib (14a) and the downstream rib (14b) using an appropriate tool (46), and releasing the applied pressure, respectively.

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