EP3596313B1 - Seal shroud assembly - Google Patents

Description

Background of the invention

A turbine ring assembly includes a plurality of ceramic matrix composite material ring sectors and a ring support structure.

The field of application of the invention is in particular that of gas turbine aeronautical engines. The invention is however applicable to other turbomachines, for example industrial turbines.

In the case of all-metallic turbine ring assemblies, it is necessary to cool all the elements of the assembly and in particular the turbine ring which is subjected to the hottest flows. This cooling has a significant impact on the performance of the engine since the cooling flow used is taken from the main flow of the engine. In addition, the use of metal for the turbine ring limits the possibilities of increasing the temperature at the turbine level, which would nevertheless improve the performance of aeronautical engines.

In order to try to resolve these problems, it was envisaged to produce turbine ring sectors in ceramic matrix composite material (CMC) in order to avoid the use of a metallic material.

CMC materials have good mechanical properties making them suitable for constituting structural elements and advantageously retain these properties at high temperatures. The use of CMC materials has advantageously made it possible to reduce the cooling flow required during operation and therefore to increase the performance of the turbomachines. In addition, the use of CMC materials advantageously makes it possible to reduce the mass of the turbomachines and to reduce the hot expansion effect encountered with the metal parts.

However, the existing solutions proposed can implement an assembly of a CMC ring sector with metal attachment parts of a ring support structure, these attachment parts being subjected to the hot flow. Consequently, these metal attachment parts undergo hot expansion, which can lead to mechanical stress on the CMC ring sectors and to a weakening of the latter.

We also know the documents FR 2 540 939 , UK 2,480,766 , EP 1 350 927 , US 2014/0271145 , US 2012/082540 And FR 2 955 898 which disclose turbine ring assemblies. GB 2136 508 A shows the technical features of the preamble of independent claim 1.

There is a need to improve existing turbine ring assemblies and their assembly, and in particular existing turbine ring assemblies using a CMC material in order to reduce the intensity of the mechanical stresses to which the ring sectors in CMC are subjected during turbine operation.

Object and summary of the invention

The invention aims to propose a turbine ring assembly allowing each ring sector to be maintained in a deterministic manner, that is to say in such a way as to control its position and prevent it from starting to vibrate. , on the one hand, while allowing the ring sector, and by extension the ring, to deform under the effects of temperature rises and pressure variations, and this in particular independently of the metal parts at the interface, and , on the other hand, while improving the seal between the non-vein sector and the vein sector and by simplifying manipulations and reducing their number for mounting the ring assembly.

An object of the invention provides a turbine ring assembly as described in claim 1.

According to a general characteristic of the object, the turbine ring assembly comprises a first annular flange and a second annular flange arranged upstream of the first annular flange relative to the direction of an air flow intended to pass through the turbine ring assembly, the first and second annular flanges respectively having a first free end and a second end opposite to the first end, the first end of the first annular flange bearing against the first hooking tab, the first end of the second annular flange being spaced from the first end of the first annular flange in the axial direction, the second ends of the first and second annular flanges being removably fixed to the first radial flange of the central ferrule of the ring support structure, and the second end of the first flange and the second end of the second flange being separated by a contact stop.

In a particular embodiment, the ring sectors can be made of ceramic matrix composite (CMC) material.

The second annular flange separated from the first annular flange at its free end makes it possible to provide the turbine ring assembly with an upstream flange dedicated to taking up the force of the high pressure distributor (DHP). The second annular flange upstream of the turbine ring and free from any contact with the ring is configured to pass the maximum axial force induced by the DHP directly into the ring support structure without passing through the ring which, when it is in CMC, has a low mechanical allowability.

Indeed, leaving a space between the first ends of the first and second annular flanges makes it possible to deflect the force received by the second flange, upstream of the first annular flange which is in contact with the turbine ring, and to do so transit directly to the central shroud of the ring support structure via the second end of the second annular flange, without impacting the first annular flange and therefore without impacting the turbine ring. The first end of the first flange does not undergo any force, the turbine ring is thus protected from this axial force.

The transit of the DHP force through the second annular flange can induce its tilting. This tilting can lead to uncontrolled contact between the lower parts, that is to say the first ends, of the second annular flange and of the first annular flange in contact with the turbine ring, which would have the consequence of directly transmitting the DHP force to the ring.

The contact stop provided between the second ends of the first and second annular flange makes it possible to avoid contact between the lower part of the second annular flange, arranged upstream of the first flange, and that of the first annular flange, following this tilting. The direct transit of the DHP force towards the ring is therefore avoided.

In addition, the removable nature of the annular flanges allows axial access to the cavity of the turbine ring. This makes it possible to assemble the ring sectors together outside the ring support structure and then to slide the assembly thus assembled axially into the cavity of the ring support structure until it comes into place. support against the second radial flange, before fixing the annular flange on the central ferrule of the ring support structure.

During the operation of fixing the turbine ring on the support structure of the ring, it is possible to use a tool comprising a cylinder or a ring on which the ring sectors are supported or suctioned during their crown assembly.

The fact of having two annular flanges each in one piece, that is to say describing the entirety of a ring over 360°, allows, compared to sectored annular flanges, to limit the passage of the flow of air between the non-vein sector and the vein sector, to the extent that all inter-sector leaks are eliminated, and therefore to control the tightness.

The solution defined above for the ring assembly thus makes it possible to maintain each ring sector in a deterministic manner, that is to say to control its position and to prevent it from starting to vibrate, while by improving the seal between the non-vein sector and the vein sector, by simplifying manipulations and reducing their number for mounting the ring assembly, and by allowing the ring to deform under the effect of temperature and pressure in particular independently of the metal parts in interface.

According to one aspect of the turbine ring assembly, the first annular flange may include the contact stop.

According to one aspect of the turbine ring assembly, the second annular flange may include the contact stop.

According to the invention, the first flange has a thickness in the axial direction less than the thickness in the axial direction of the second flange.

The thinness of the second end of the first annular flange offers flexibility to the upstream part of the support structure intended to be in contact with the ring.

The second annular flange, downstream of the first annular flange, ensures, thanks to its increased thickness, greater rigidity to the downstream part of the ring support structure.

According to one aspect of the turbine ring assembly, the central shroud of the ring support structure has a variable radius in the axial direction, the radius of the central shroud decreasing according to the direction of the air flow intended to pass through the turbine ring assembly, that is to say in the direction from the first radial flange towards the second radial flange.

More particularly, the central shroud of the ring support structure has a first radial portion facing the first hooking tab of the turbine ring, and a second radial portion downstream of the first radial portion relative to the direction of said air flow intended to pass through the turbine ring assembly and opposite the second attachment tab of the turbine ring, the second radial portion having a radius of curvature less than the radius of curvature of the first radial portion.

According to the invention, the second radial flange of the ring support structure has a first free end and a second end secured to the central ferrule of the ring support structure, the first end of the second radial flange being at contact of the second hooking tab of the turbine ring and having a thickness in the axial direction greater than the thickness of the first end of the first annular flange.

Controlling the rigidity at the level of the axial contacts of the ring support structure with the ring ensures that the seal is maintained in all circumstances, without inducing efforts. axial too high on the ring. The thin section of the second annular flange, downstream, of the ring support structure ensures flexibility of the downstream part of the ring support structure with respect to its upstream part formed by the first annular flange and the first and second annular flanges, due to the significant thickness of the first annular flange.

According to one aspect of the turbine ring assembly, the ring sector can have a section in the Greek letter pi (π) inverted according to the cutting plane defined by the axial direction and the radial direction, and the assembly can comprise, for each ring sector, at least three pins to radially hold the ring sector in position, the first and second hooking lugs of each ring sector each comprising a first end secured to the external face of the annular base, a second free end, at least three lugs for receiving said at least three pins, at least two lugs extending projecting from the second end of one of the first or second hooking lugs in the radial direction of the turbine ring and at least one ear extending projecting from the second end of the other hooking lug in the radial direction of the turbine ring, each receiving ear comprising an orifice for receiving one of the pions.

According to one aspect of the turbine ring assembly, the ring sector may have a section having an elongated K shape according to the cutting plane defined by the axial direction and the radial direction, the first and a second legs d hooking having an S shape.

According to one aspect of the turbine ring assembly, the ring sector can have, on at least one radial range of the ring sector, an O-shaped section according to the cutting plane defined by the axial direction and the direction radial, the first and second hooking lugs each having a first end secured to the external face and a second free end, and each ring sector comprising a third and a fourth hooking lugs each extending, in the axial direction of the turbine ring, between a second end of the first hooking tab and a second end of the second hooking tab, each ring sector being fixed to the ring support structure by a fixing screw comprising a screw head bearing against the ring support structure and a thread cooperating with a tapping made in a fixing plate, the fixing plate cooperating with the third and fourth hooking tabs. The ring sector further comprises radial pins extending between the central ferrule and the third and fourth hooking lugs.

Another object of the invention proposes a turbomachine comprising a turbine ring assembly as defined above.

Brief description of the designs.

• la figure 1 est une vue schématique en perspective d'un premier mode de réalisation d'un ensemble d'anneau de turbine ne faisant pas partie de l'invention.
• la figure 2 est une vue schématique en perspective éclatée de l'ensemble d'anneau de turbine de la figure 1 ;
• la figure 3 est une vue schématique en coupe de l'ensemble d'anneau de turbine de la figure 1 ;
• la figure 4 est une vue schématique en coupe d'un deuxième mode de réalisation de l'ensemble d'anneau de turbine, ne faisant pas partie non plus de l'invention.
• la figure 5 est une vue schématique en coupe d'un troisième mode de réalisation de l'ensemble d'anneau de turbine ;
• la figure 6 est une vue schématique en coupe d'un quatrième mode de réalisation de l'ensemble d'anneau de turbine ;
• la figure 7 est une vue schématique en coupe d'un cinquième mode de réalisation de l'ensemble d'anneau de turbine, ne faisant pas partie non plus de l'invention.
• la figure 8 présente une vue schématique en coupe d'un sixième mode de réalisation de l'ensemble d'anneau de turbine.

The invention will be better understood on reading below, for information but not limitation, with reference to the appended drawings in which:

• there figure 1 is a schematic perspective view of a first embodiment of a turbine ring assembly not forming part of the invention.
• there figure 2 is a schematic exploded perspective view of the turbine ring assembly of the figure 1 ;
• there Figure 3 is a schematic sectional view of the turbine ring assembly of the figure 1 ;
• there Figure 4 is a schematic sectional view of a second embodiment of the turbine ring assembly, also not part of the invention.
• there Figure 5 is a schematic sectional view of a third embodiment of the turbine ring assembly;
• there Figure 6 is a schematic sectional view of a fourth embodiment of the turbine ring assembly;
• there figure 7 is a schematic sectional view of a fifth embodiment of the turbine ring assembly, also not part of the invention.
• there figure 8 presents a schematic sectional view of a sixth embodiment of the turbine ring assembly.

Detailed description of embodiments

There figure 1 shows a high pressure turbine ring assembly comprising a ceramic matrix composite (CMC) turbine ring 1 and a ring supporting metal structure 3. Turbine ring 1 surrounds a set of rotating blades (not shown). The turbine ring 1 is formed of a plurality of ring sectors 10, the figure 1 being a view in radial section. The arrow D _A indicates the axial direction of the turbine ring 1 while the arrow D _R indicates the radial direction of the turbine ring 1. For reasons of simplification of presentation, the figure 1 is a partial view of the turbine ring 1 which is in reality a complete ring.

As illustrated on the figure 2 And 3 which respectively present a schematic exploded perspective view and a sectional view of the turbine ring assembly of the figure 1 , the sectional view being according to a section plane comprising the radial direction D _R and the axial direction D _A , each sector of ring 10 has, according to a plane defined by the axial directions D _A and radial directions D _R , a section substantially in the shape of the reversed Greek letter π. The section in fact comprises an annular base 12 and radial upstream and downstream attachment tabs, respectively 14 and 16. The terms "upstream" and "downstream" are used here in reference to the direction of flow of the gas flow in the turbine. represented by the arrow F on the figure 1 . The legs of the ring sector 10 could have another shape, the section of the ring sector having a shape other than π, such as for example a K or O shape.

The annular base 12 comprises, in the radial direction D _R of the ring 1, an internal face 12a and an external face 12b opposite each other. The internal face 12a of the annular base 12 is coated with a layer 13 of abradable material forming a thermal and environmental barrier and defines a gas flow path in the turbine. The terms "internal" and "external" are used here in reference to the radial direction D _R in the turbine.

The upstream and downstream radial hooking lugs 14 and 16 extend projecting, in the direction D _R , from the external face 12b of the annular base 12 at a distance from the upstream and downstream ends 121 and 122 of the annular base 12. The upstream and downstream radial hooking tabs 14 and 16 extend over the entire width of the ring sector 10, that is to say over the entire arc of a circle described by the ring sector 10 , or even over the entire circumferential length of the ring sector 10.

As illustrated in the figures 1 to 3 , the ring support structure 3 which is integral with a turbine casing comprises a central ferrule 31, extending in the axial direction D _A , and having an axis of revolution coincident with the axis of revolution of the turbine ring 1 when they are fixed together, as well as a first annular radial flange 32 and a second annular radial flange 36, the first annular radial flange 32 being positioned upstream of the second annular radial flange 36 which is therefore located in downstream of the first annular radial flange 32.

The second annular radial flange 36 extends in the circumferential direction of the ring 1 and, in the radial direction D _R , from the central ferrule 31 towards the center of the ring 1. It comprises a first free end 361 and a second end 362 secured to the central ferrule 31. The second annular radial flange 36 comprises a first portion 363, a second portion 364, and a third portion 365 included between the first portion 363 and the second portion 364. The first portion 363 is extends between the first end 361 and the third portion 365, and the second portion 364 extends between the third portion 365 and the second end 362. The first portion 363 of the second annular radial flange 36 is in contact with the radial flange d downstream attachment 16. The second portion 364 is thinned relative to the first portion 363 and the third portion 365 so as to give a certain flexibility to the second annular radial flange 36 and thus not overly constrain the turbine ring 1 in CMC.

The first annular radial flange 32 extends in the circumferential direction of the ring 1 and, in the radial direction D _R , from the central ferrule 31 towards the center of the ring 1. It comprises a first free end 321 and a second end 322 secured to the central ferrule 31.

As illustrated in the figures 1 to 3 , the turbine ring assembly 1 comprises a first annular flange 33 and a second annular flange 34, the two annular flanges 33 and 34 being removably fixed on the first annular radial flange 32. The first and second annular flanges 33 and 34 are arranged upstream of the turbine ring 1 relative to the direction F of flow of the gas flow in the turbine.

The first annular flange 33 is arranged downstream of the second annular flange 34. The first annular flange 33 has a first free end 331 and a second end 332 removably fixed to the ring support structure 3, and more particularly to the first annular radial flange 32. The second annular flange 34 has a first free end 341 and a second end 342 removably fixed to the ring support structure 3, and more particularly to the first annular radial flange 32.

Furthermore, the first annular flange 33 has a first portion 333 extending from the first end 331 and a second portion 334 extending between the first portion 333 and the second end 332. When the ring assembly 1 is mounted , the first portion 333 of the first annular flange 33 rests against the upstream radial attachment lug 14 of each of the ring sectors 10 composing the turbine ring 1, and the second portion 334 of the first annular flange 34 is finds support against at least part of the first annular radial flange 32.

The second annular flange 34 is dedicated to absorbing the force of the high pressure distributor (DHP) on the ring assembly 1, on the one hand, by deforming, and, on the other hand, by passing this force towards the casing line which is more mechanically robust, that is to say towards the line of the ring support structure 3 as this is illustrated by the force arrows E presented on the Figure 3 .

The first annular flange 33 and the second annular flange 34 are in contact at their second ends 332 and 342 respectively.

The radial retention of the ring 1 is ensured by the first annular flange 33 which is placed on the first annular radial flange 32 of the ring support structure 3 and on the upstream radial attachment tab 14. The first annular flange 33 ensures the seal between the vein cavity and the non-vein cavity of the ring.

The second annular flange 34 ensures the connection between the downstream part of the DHP, the ring support structure 3, or casing, by radial surface contact, and the first annular flange 33 by axial surface contact.

In the first embodiment illustrated on the figures 1 to 3 , the second end 342 of the second annular flange 34 comprises a contact stop 340 extending projecting in the axial direction D _A between the second annular flange 34 and the first annular flange 33. The contact stop 340 makes it possible to maintain a distance between the first end 331 of the first annular flange 33 and the first end 341 of the second annular flange 34 during the tilting of the second annular flange 34 induced by the DHP force.

The first and second annular flanges 33 and 34 are fixed by hooping to the ring support structure 3.

The second annular flange 34 is hooped onto the central ferrule 31 of the ring support structure 3, the hooping being carried out between a portion 345 projecting, in the radial direction D _R , of the second end 342 of the second annular flange 34 and the central ferrule 31.

The first annular flange 33 is hooped onto the first annular radial flange 32 of the ring support structure 3. More precisely, the hooping is carried out between a radial surface 335 approximately in the middle, in the radial direction D _R , of the first annular flange 33 and a radial surface 325 halfway up the first annular radial flange 32, the two radial surfaces 335 and 325 being facing, and even in contact with, one another in the radial direction D _R . The radial surface 335 of the first annular flange 33 extends over the entire circumference of the first annular flange 33, and on the face of the first annular flange 33 facing the first annular flange 32. More precisely, the radial surface 335 of the first annular flange 33 can be formed anywhere on the portion of the first annular flange 33 intended to be in contact with the first annular radial flange 32, the radial surface 325 of the first annular radial flange 32 being formed at a corresponding height on the face of the first annular radial flange 32 facing the first annular flange 33.

The ring support structure 3 further comprises screws 38 which make it possible to place the ring in the low radial position, that is to say towards the vein, in a deterministic manner. There γ in fact has a clearance between the axial pins and the bores on the ring to compensate for the differential expansion between the metal and the CMC elements which takes place when hot.

On the Figure 4 is presented a schematic sectional view of a second embodiment of the turbine ring assembly.

The second embodiment illustrated on the Figure 4 differs from the first embodiment illustrated on the figures 1 to 3 mainly in that the second end 332 of the first annular flange 33 comprises a contact stop 330, instead of the second flange 34, the contact stop 330 projecting in the axial direction D _A between the first annular flange 33 and the second annular flange 34.

As in the first embodiment, the first and second annular flanges 33 and 34 are fixed on the ring support structure 3 by radial shrinking.

As illustrated in the Figure 4 , in the second embodiment, the second end 342 of the second annular flange 34 has, in section along the section plane comprising the axial direction D _A and the radial direction D _R , a rounded shape and thus forms a ball joint in contact with the central ferrule 31 of the ring support structure 3. The tilting of the second annular flange 34 is done thanks to this form of ball joint on the second end 342. The ball joint is in linear contact with the central ferrule 31 of the structure of ring support 3. When the force DHP is applied to the second annular flange 34, the latter tilts forward, that is to say in the direction of the flow F. The upper part of the second annular flange 34 , that is to say that extending radially from the second end 342, is stopped axially by the contact stop 330 of the first annular flange 33.

On the figure 5 is presented a schematic sectional view of a third embodiment of the turbine ring assembly.

The third embodiment of the invention illustrated on the figure 5 also presents the contact stop 340 on the second end 342 of the second annular flange 34. The third embodiment differs from the first embodiment illustrated on the figures 1 to 3 mainly in that the first annular flange 33 has a thickness in the axial direction D _A less than the thickness of the second annular flange 34. The first annular flange 33 is fixed by shrinking the second end 332 onto the central ferrule 31 of the ring support structure 3.

As explained later in the description, the third embodiment of the invention also presents differences compared to the first embodiment for fixing the ring on the ring support structure 3.

In the third embodiment, the first portion of the second annular radial flange 36 further comprises a groove 360 in which is arranged an omega seal 369 extending between the second annular radial flange 36 and the downstream radial attachment tab 16 .

On the Figure 6 is presented a schematic sectional view of a fourth embodiment of the turbine ring assembly.

The fourth embodiment of the invention illustrated on the Figure 6 is similar to the third embodiment illustrated in the Figure 5 . The fourth embodiment also presents the contact stop 340 on the second end 342 of the second annular flange 34, the omega seal 369 extending in the groove 360 of the second annular radial flange 36, as well as a thickness of the first flange annular 33 in the axial direction D _A less than the thickness of the second annular flange 34.

The fourth embodiment of the invention illustrated on the Figure 6 differs from the third embodiment illustrated on the Figure 5 in that the central ferrule 31 of the ring support structure 3 has a variable radius in the axial direction D _A , the radius of the central ferrule 31 decreasing according to the direction of the air flow F intended to pass through the assembly turbine ring, that is to say in the direction going from the first radial flange 32 towards the second radial flange 36.

The central ferrule 31 of the ring support structure 3 has a first radial portion 310 facing the upstream radial attachment tab 14 of the ring 1, and a second radial portion 315 downstream of the first radial portion 310 relative to the direction of the air flow F and facing the downstream radial attachment tab 16 of the ring 1. The second radial portion 315 has a radius of curvature less than the radius of curvature of the first radial portion 310.

On the figure 7 Presented is a schematic sectional view of a fifth embodiment of the turbine ring assembly.

The fifth embodiment illustrated on the figure 7 differs from the first embodiment illustrated on the figures 1 to 3 in that the ring sector 10 has, in the plane defined by the axial D _A and radial D _R directions, a K-shaped section instead of an inverted π-shaped section.

On the figure 8 is presented a schematic sectional view of a sixth embodiment of the turbine ring assembly.

The sixth embodiment illustrated on the figure 8 differs from the first embodiment illustrated on the figures 1 to 3 in that the ring sector 10 presents in the plane defined by the axial directions D _A and radial directions D _R , on part of the ring sector 10, an O-shaped section instead of an O-shaped section π inverted, the ring section 10 being fixed to the ring support structure 3 using a screw 19 and a fixing part 20, the screws 38 being removed.

In each of the embodiments illustrated on the figures 1 to 8 , in the axial direction D _A , the second annular radial flange 36 of the ring support structure 3 is separated from the first annular flange 33 by a distance corresponding to the spacing of the upstream and downstream radial attachment tabs 14 and 16 so as to maintain the latter between the first annular radial flange 32 and the second annular radial flange 36.

In the first and second embodiments illustrated on the figures 1 to 4 , to hold in position the ring sectors 10, and therefore the turbine ring 1, with the ring support structure 3, the ring assembly comprises two first pins 119 cooperating with the upstream hooking tab 14 and the first annular flange 33, and two second pins 120 cooperating with the downstream hooking tab 16 and the second annular radial flange 36.

In these two embodiments illustrated respectively on the figures 1 to 3 and on the Figure 4 , for each corresponding ring sector 10, the second portion 334 of the first annular flange 33 comprises two orifices 3340 for receiving the first two pins 119, and the third portion 365 of the annular radial flange 36 comprises two orifices 3650 configured to receive the two second pawns 120.

For each ring sector 10, each of the upstream and downstream radial attachment tabs 14 and 16 comprises a first end, 141 and 161, secured to the external face 12b of the annular base 12 and a second end, 142 and 162, free. The second end 142 of the tab radial upstream attachment tab 14 comprises two first lugs 17 each comprising an orifice 170 configured to receive a first pin 119. Similarly, the second end 162 of the radial downstream attachment lug 16 comprises two second lugs 18 each comprising an orifice 180 configured to receive a second pin 120. The first and second ears 17 and 18 extend projecting in the radial direction D _R from the turbine ring 1 respectively from the second end 142 of the upstream radial attachment tab 14 and the second end 162 of the downstream radial hooking tab 16.

The orifices 170 and 180 can be circular or oblong. Preferably all of the orifices 170 and 180 comprise a portion of circular orifices and a portion of oblong orifices. The circular orifices make it possible to tangentially index the rings and prevent them from moving tangentially (particularly in the event of contact with the blade). The oblong holes accommodate differential expansions between the CMC and the metal. CMC has a much lower expansion coefficient than metal. When hot, the lengths in the tangential direction of the ring sector and the facing portion of the casing will therefore be different. If there were only circular orifices, the metal casing would impose its movements on the CMC ring, which would be a source of very high mechanical stresses in the ring sector. Having elongated holes in the ring assembly allows the pin to slide into that hole and avoid the over-constraint phenomenon mentioned above. Therefore, two drilling schemes can be imagined: a first drilling scheme, for a case with three lugs, would include a radial circular orifice on a radial attachment flange and two oblong tangential orifices on the other radial attachment flange , and a second drilling diagram, for a case with at least four lugs, would include a circular orifice and an oblong orifice per radial attachment flange facing each other. Other ancillary cases can also be considered.

For each ring sector 10, the first two lugs 17 are positioned at two different angular positions relative to the axis of revolution of the turbine ring 1. Likewise, for each ring sector 10, the two second ears 18 are positioned at two different angular positions relative to the axis of revolution of the turbine ring 1.

In the third and fourth embodiments illustrated on the figures 5 And 6 , each ring sector only comprises one pin 119 cooperating with the upstream radial attachment tab 14 and with the first annular radial flange 32. More particularly, the pin 119 cooperates with the orifice 170 of the first ear 17 of the upstream radial attachment tab 14 corresponding to the ring sector 10 and with an orifice 3260 of an ear 326 projecting radially towards the axis of revolution of the ring 1 and the ring support structure 3 .

As illustrated on the figure 7 , in the fifth embodiment, each ring sector 10 has, according to a plane defined by the axial directions D _A and radial directions D _R, a substantially K-shaped section comprising an annular base 12 with, in the radial direction D _R of the ring, an internal face 12a coated with a layer 13 of abradable material forming a thermal and environmental barrier and which defines the gas flow path in the turbine. Upstream and downstream radial hooking tabs 140, 160 substantially S-shaped extend, in the radial direction D _R , from the external face 12b of the annular base 12 over the entire width thereof and at -above the upstream and downstream circumferential end portions 121 and 122 of the annular base 12.

The radial attachment tabs 140 and 160 have a first end, referenced respectively 1410 and 1610, secured to the annular base 12 and a second free end, referenced respectively 1420 and 1620. The free ends 1420 and 1620 of the radial attachment tabs upstream and downstream 140 and 160 extend either parallel to the plane in which the annular base 12 extends, that is to say in a circular plane, or in a rectilinear manner while the hooking tabs 140 and 160 extend in an annular manner. In this second configuration where the ends are rectilinear and the annular hooking lugs, in the case of a possible tilting of the ring during operation, the surface supports then become linear supports which offers greater sealing than in the case of occasional supports. The second end 1620 of the downstream radial hooking tab 160 is held between a portion 3610 of the second annular radial flange 36 extending projecting in the axial direction D _A from the first end 361 of the second annular radial flange 36 in the direction opposite to the direction of flow F and the free end of the associated screw 38, it i.e. the screw opposite the screw head. The second end 1410 of the upstream radial attachment tab 140 is held between a portion 3310 of the first annular flange 33 extending projecting in the axial direction D _A from the first end 331 of the first annular flange 33 in the direction of flow F and the free end of the associated screw 38.

In the sixth embodiment illustrated on the figure 8 , the ring sector 10 comprises an axial hooking tab 17' extending between the upstream and downstream radial hooking tabs 14 and 16. The axial hooking tab 17' extends more precisely, in the direction axial D _A , between the second end 142 of the upstream radial attachment tab 14 and the second end 162 of the downstream radial attachment tab 16.

The axial hooking tab 17' comprises an upstream end 171' and an end 172' separated by a central part 170'. The upstream and downstream ends 171' and 172' of the axial hooking tab 17' extend projecting, in the radial direction D _R , from the second end 142, 162 of the radial hooking tab 14, 16 to which they are coupled, so as to have a central part 170' of axial hooking tab 17' raised relative to the second ends 142 and 162 of the upstream and downstream radial hooking tabs 14 and 16.

For each ring sector 10, the turbine ring assembly comprises a screw 19 and a fixing part 20. The fixing part 20 is fixed on the axial hooking tab 17'.

The fixing part 20 further comprises an orifice 21 provided with a thread cooperating with a thread of the screw 19 to fix the fixing part 20 to the screw 19. The screw 19 comprises a screw head 190 whose diameter is greater to the diameter of an orifice 39 made in the central ferrule 31 of the support structure of the ring 3 through which the screw 19 is inserted before being screwed to the fixing part 20.

The radial connection of the ring sector 10 with the ring support structure 3 is carried out using the screw 19, the head 190 of which bears on the central crown 31 of the structure of support of the ring 3, and of the fixing part 20 screwed to the screw 19 and fixed to the axial hooking tab 17' of the ring sector 10, the screw head 190 and the fixing part 20 exerting forces in opposite directions to hold the ring 1 and the ring support structure 3 together.

In a variant, the radial holding of the ring downwards can be ensured using four radial pins placed on the axial hooking tab 17', and the radial holding of the ring upwards can be ensured by a pick head, secured to the screw 19, placed under the ring in the cavity between the axial hooking tab 17' and the external face 12b of the annular base.

In each of the embodiments of the invention illustrated on the figures 1 to 8 , each ring sector 10 further comprises rectilinear bearing surfaces 110 mounted on the faces of the upstream and downstream radial attachment lugs 14 and 16 in contact respectively with the first annular flange 33 and the second annular radial flange 36, that is to say on the upstream face 14a of the upstream radial hooking tab 14 and on the downstream face 16b of the downstream radial hooking tab 16. In a variant, the rectilinear supports could be mounted on the first annular flange 33 and on the second downstream annular radial flange 36.

The rectilinear supports 110 make it possible to have controlled sealing zones. Indeed, the bearing surfaces 110 between the upstream radial attachment tab 14 and the first annular flange 33, on the one hand, and between the downstream radial attachment tab 16 and the second annular radial flange 36 are included in the same rectilinear plane.

More precisely, having supports on radial planes makes it possible to overcome the effects of decambering in the turbine ring 1.

We now describe a method of producing a turbine ring assembly corresponding to that shown in the figure 1 , that is to say according to the first embodiment illustrated on the figures 1 to 3 , not being part of the invention.

Each ring sector 10 described above is made of ceramic matrix composite material (CMC) by formation of a fibrous preform having a shape close to that of the ring sector and densification of the ring sector by a ceramic matrix .

To produce the fibrous preform, ceramic fiber yarns can be used, for example SiC fiber yarns such as those marketed by the Japanese company Nippon Carbon under the name "Hi-NicalonS", or carbon fiber yarns.

The fibrous preform is advantageously produced by three-dimensional weaving, or multilayer weaving with the provision of unbinding zones making it possible to separate the parts of preforms corresponding to the hooking lugs 14 and 16 of sectors 10.

The weave can be interlock type, as shown. Other three-dimensional or multi-layer weaves can be used, such as multi-canvas or multi-satin weaves. We can refer to the document WO 2006/136755 .

After weaving, the blank can be shaped to obtain a ring sector preform which is consolidated and densified by a ceramic matrix, the densification being able to be carried out in particular by chemical infiltration in the gas phase (CVI) which is well known in self. In a variant, the textile preform can be hardened a little by CVI so that it is sufficiently rigid to be handled, before bringing liquid silicon up by capillary action into the textile to carry out densification (“Melt Infiltration”).

A detailed example of manufacturing CMC ring sectors is described in particular in the document US 2012/0027572 .

The ring support structure 3 is made of a metallic material such as a Waspaloy ^® or Inconel 718 ^® or even C263 ^® alloy.

The production of the turbine ring assembly continues by mounting the ring sectors 10 on the ring support structure 3.

For this, the ring sectors 10 are assembled together on a “spider” type annular tool comprising, for example, suction cups configured to each hold a ring sector 10.

Then the two second pins 120 are inserted into the two orifices 3650 provided in the third part 365 of the second annular radial flange 36 of the ring support structure 3.

The ring 1 is then mounted on the ring support structure 3 by inserting each second pin 120 into each of the orifices 180 of the second lugs 18 of the downstream radial attachment flanges 16 of each ring sector 10 composing the ring 1.

We then place all the first pins 119 in the orifices 170 provided in the first lugs 17 of the radial hooking lug 14 of the ring 1.

Then we fix the first annular flange 33 and the second annular flange 34 to the ring support structure 3 and to the ring 1. The first and second annular flanges 33 and 34 are fixed by shrinking to the support structure d ring 3. The DHP force exerted in the direction of flow F reinforces this attachment during engine operation.

To hold the ring 1 in position radially, the first annular flange 33 is fixed to the ring by inserting each first pin 119 into each of the orifices 170 of the first lugs 17 of the upstream radial attachment lugs 14 of each ring sector 10 making up ring 1.

The ring 1 is thus held in position axially using the first annular flange 33 and the second annular radial flange 36 bearing respectively upstream and downstream on the rectilinear bearing surfaces 110 of the radial attachment tabs respectively upstream 14 and downstream 16. When installing the first annular flange 33, an axial prestress can be applied to the first annular flange 33 and to the upstream radial attachment tab 14 to compensate for the effect of differential expansion between the material CMC of the ring 1 and the metal of the ring support structure 3. The first annular flange 33 is held in axial stress by mechanical elements placed upstream as is illustrated in dotted lines on the Figure 3 .

The ring 1 is held in position radially using the first and second pins 119 and 120 cooperating with the first and second lugs 17 and 18 and the orifices 3340 and 3650 of the first annular flange 33 and the annular radial flange 36.

The invention thus provides a turbine ring assembly allowing the maintenance of each ring sector in a deterministic manner while allowing, on the one hand, the ring sector, and by extension the ring, to deform under the effects of temperature rises and pressure variations, particularly independently of the metal parts at the interface, and, on the other hand, while improving the seal between the non-vein sector and the vein sector and by simplifying manipulations and reducing their number for mounting the ring assembly.

Furthermore, the invention provides a turbine ring assembly comprising an upstream annular flange dedicated to absorbing the DHP force and thus inducing low levels of forces in the CMC ring, a contact stop between the annular flange dedicated to absorbing the DHP force and the annular flange used to hold the ring, the stop ensuring non-contact of the lower parts of the two flanges when the upstream flange tilts. The turbine ring assembly according to the invention also makes it possible to control the rigidity at the level of the upstream and downstream axial contacts between the CMC ring and the metal casing. As a result, sealing is ensured in all circumstances, without inducing excessively high axial forces on the ring.

Claims (8)

1. A turbine ring assembly comprising a plurality of ring sectors (10) forming a turbine ring (1) and a ring support structure (3), each ring sector (10) having, along a section plane defined by an axial direction (D_A) and a radial direction (D_R) of the turbine ring (1), a portion forming an annular base (12) with, in the radial direction (D_R) of the turbine ring (1), an inner face (12a) defining the inner face of the turbine ring (1) and an outer face (12b) from which a first and a second attachment tabs (14, 16) protrude, the ring support structure (3) including a central shroud (31) from which a first and a second radial clamps (32, 36) protrude between which the first and second attachment tabs (14, 16) of each ring sector (10) are maintained,

   characterized in that it comprises a first annular flange (33) and a second annular flange (34) disposed upstream of the first annular flange (33) with respect to the direction of an air flow (F) intended to pass through the turbine ring assembly (1), the first and second annular flanges (33, 34) having respectively a first free end (331, 341) and a second end (332, 342) opposite to the first end, the first end (331) of the first flange (33) bearing against the first attachment tab (14), the first end (341) of the second annular flange (34) being distant from the first end (331) of the first annular flange (33) in the axial direction (D_A), the second ends (332, 342) of the first and second annular flanges (33, 34) being removably fastened to the first radial clamp (32) of the central shroud (31) of the ring support structure (3), and the second end of the first flange (33) and the second end (342) of the second flange (34) being separated by a contact abutment (330, 340),

   the first flange (33) having a thickness in the axial direction (D_A) smaller than the thickness in the axial direction (D_A) of the second flange (34)

   the second radial clamp (36) of the ring support structure (3) has a first free end (361) and a second end (362) secured to the central shroud (31) of the ring support structure (3), the first end (361) of the second radial clamp (36) being in contact with the second attachment tab (16) of the turbine ring (1) and having a thickness in the axial direction (D_A) greater than the thickness of the first end (331) of the first annular flange (33).
2. The assembly according to claim 1, wherein the first annular flange (33) comprises the contact abutment (330).
3. The assembly according to claim 1, wherein the second annular flange (34) comprises the contact abutment (340).
4. The assembly according to any of claims 1 to 3, wherein the central shroud (31) of the ring support structure (3) has a variable radius in the axial direction (D_A), the radius of the central shroud (31) decreasing along the direction of the air flow (F) intended to pass through the turbine ring assembly (1), that is to say in the direction from the first radial clamp (32) to the second radial clamp (36).
5. The assembly according to any of claims 1 to 4, wherein the ring sector has a π _-section along the section plane defined by the axial direction (D_A) and the radial direction (D_R), and the assembly comprises, for each ring sector (10), at least three pins (119, 120) to radially hold the ring sector (10) in position, the first and second attachment tabs (14, 16) of each ring sector (10) each comprising a first end (141, 161) secured to the outer face (12b) of the annular base (12), a second free end (142, 162), at least three lugs (17, 18) for receiving said at least three pins (119, 120), at least two lugs (17) protruding from the second end (142, 162) of one of the first or second attachment tabs (14, 16) in the radial direction (D_R) of the turbine ring (1) and at least one lug (18) protruding from the second end (162, 142) of the other attachment tab (16, 14) in the radial direction (D_R) of the turbine ring (1), each receiving lug (17, 18) including an orifice (170, 180) for receiving one of the pins (119, 120).
6. The assembly according to any of claims 1 to 4, wherein the ring sector has a K-section along the section plane defined by the axial direction (D_A) and the radial direction (D_R), the first and second attachment tabs (14, 16) having an S-shape
7. The assembly according to any of claims 1 to 4, wherein the ring sector has an O-shaped section along the section plane defined by the axial direction (D_A) and the radial direction (D_R), the first and second attachment tabs (14, 16) each having a first end (141, 161) secured to the outer face (12b) and a second free end (142, 162), and each ring sector (10) comprising a third and a fourth attachment tabs (17') each extending, in the axial direction (D_A) of the turbine ring (1), between a second end (142) of the first attachment tab (14) and a second end (162) of the second attachment tab (16), each ring sector (10) being fastened to the ring support structure (3) by a fastening screw (19) including a screw head (190) bearing against the ring support structure (3) and a thread cooperating with a tapping formed in a fastening plate (20), the fastening plate (20) cooperating with the third and fourth attachment tabs (17').
8. A turbomachine comprising a turbine ring assembly (1) according to any one of claims 1 to 7.

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