EP3596314B1 - Turbine shroud seal assembly - Google Patents

Description

Background of the invention

The invention relates to a turbine ring assembly comprising a plurality of ring sectors made of ceramic matrix composite material as well as 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-metal 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 level of the turbine, which would nevertheless make it possible to improve the performance of aero engines.

In order to try to solve these problems, it has been envisaged to produce turbine ring sectors in ceramic matrix composite material (CMC) in order to do away with 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 to be imposed 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 hooking parts of a ring support structure, these hooking parts being subjected to the hot flow. Consequently, these metal fastening parts undergo hot expansions, which can lead to a mechanical stressing of the CMC ring sectors and to an embrittlement of the latter.

We also know the documents FR 2,540,939 , GB 2 480 766 , EP 1,350,927 , US 2014/0271145 , US 2012/082540 and FR 2 955 898 which disclose turbine ring assemblies WO2014123654 shows the technical characteristics of the preamble of independent claim 1.

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

Purpose and summary of the invention

The invention aims to provide a turbine ring assembly making it possible to maintain each ring sector in a deterministic manner, that is to say so as to control its position and prevent it from vibrating. , on the one hand, while allowing the ring sector, and by extension to the ring, to deform under the effects of temperature rises and pressure variations, and this in particular independently of the metallic 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 the manipulations and reducing their number for mounting the ring assembly.

An object of the invention provides a turbine ring assembly comprising a plurality of ring sectors forming a turbine ring and a ring support structure, each ring sector having, according to a section plane defined by an axial direction and a radial direction of the turbine ring, an annular base portion with, in the radial direction of the turbine ring, an inner face defining the inner face of the turbine ring and an outer face to from which project a first and a second hooking lug, the ring support structure comprising a central ferrule from which project a first and a second radial flange between which are held the first and second hooking tabs of each ring sector.

According to a general characteristic of the object, the turbine ring assembly comprises a first annular flange and a second annular flange disposed upstream of the first annular flange with respect 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 flange resting against the first hooking lug, the first end of the second annular flange being distant from the first end of the first annular flange in the axial direction, and the second end of the second flange annular comprising an upstream bearing ring projecting upstream in the axial direction, the upstream bearing ring having a radial bearing in contact with the central shell of the ring support structure.

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

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 absorbing 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 it. ring which presents, when in CMC, a low mechanical admissible.

Indeed, leaving a space between the first ends of the first and the 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. pass directly to the central shell 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. Since the first end of the first flange is not subjected to any force, the turbine ring is thus preserved from this axial force.

The transit of the DHP force through the second annular flange can induce its tilting. This tilting can cause 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 upstream support ring provides greater resistance to tilting induced by the DHP force. The support ring takes up the significant tangential stresses caused by the DHP force and therefore limits the tilting of the second annular flange.

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 on the outside of 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 contact with one another. bearing against the second radial flange, before fixing the annular flanges on the central ferrule of the ring support structure.

During the operation of fixing the turbine ring on the ring support structure, it is possible to use a tool comprising a cylinder or a ring on which the ring sectors are pressed or vacuumed 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 °, makes it possible, compared to sectorized annular flanges, to limit the passage of the flow of air between the non-duct sector and the duct sector, insofar as 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 vibrating, while by improving the seal between the non-vein sector and the vein sector, by simplifying the 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 at the interface.

According to a first aspect of the turbine ring assembly, the second annular flange may include a contact stopper extending in the axial direction of the turbine ring and separating the second end of the second annular flange from the second end. of the first annular flange.

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

According to a second aspect of the turbine ring assembly, the assembly may further comprise an omega seal mounted between the first end of the second annular flange and the first end of the first flange, the second annular flange being fixed to the structure. ring support on a part upstream of the radial support.

The omega seal ensures the seal between the vein cavity and the non-vein cavity upstream of the ring.

According to a third aspect of the turbine ring assembly, the ring sector may have a section in the Greek letter pi (π) inverted according to the section plane defined by the axial direction and the radial direction, and the assembly may comprise, for each ring sector, at least three pins for radially holding the ring sector in position, the first and second hooking tabs of each ring sector each comprising a first end integral with the external face of the annular base, a second free end, at least three ears for receiving said at least three pins, at least two ears projecting from the second end of one of the first or second hooking tabs in the radial direction of the turbine ring and at least one lug projecting from the second end of the other hooking lug in the radial direction of the turbine ring, each receiving lug having a receiving orifice ion of one of the pawns.

According to a fourth aspect of the turbine ring assembly, the ring sector may have a section having an elongated K-shape along the section plane defined by the axial direction and the radial direction, the first and a second legs. hook having an S-shape.

According to a fifth aspect of the turbine ring assembly, the ring sector may have, over at least one radial range of the ring sector, an O-shaped section according to the section plane defined by the axial direction and radial direction, the first and the second hooking lugs each having a first end integral with the outer face and a second free end, and each ring sector comprising a third and a fourth hooking lugs s' each extending, in the axial direction of the turbine ring, between a second end of the first hooking lug and a second end of the second hooking lug, each ring sector being fixed to the support structure d 'ring by a fixing screw comprising a screw head bearing against the ring support structure and a thread cooperating with an internal thread made in a fixing plate, the fixing plate cooperating with the third and fourth hooking tabs .

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

Brief description of the drawings.

• la figure 1 est une vue schématique en perspective d'un premier mode de réalisation d'un ensemble d'anneau de turbine selon 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 ;
• 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.

The invention will be better understood on reading below, by way of indication but not limiting, with reference to the appended drawings in which:

• the figure 1 is a schematic perspective view of a first embodiment of a turbine ring assembly according to the invention;
• the figure 2 is a schematic exploded perspective view of the turbine ring assembly of the figure 1 ;
• the figure 3 is a schematic sectional view of the turbine ring assembly of the figure 1 ;
• the figure 4 is a schematic sectional view of a second embodiment of the turbine ring assembly;
• the figure 5 is a schematic sectional view of a third embodiment of the turbine ring assembly;
• the figure 6 is a schematic sectional view of a fourth embodiment of the turbine ring assembly.

Detailed description of embodiments

The figure 1 shows a high pressure turbine ring assembly comprising a turbine ring 1 in composite material with ceramic matrix (CMC) and a metal ring support structure 3. The turbine ring 1 surrounds a set of rotating blades (not shown). The turbine ring 1 is formed from 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 simplicity of presentation, the figure 1 is a partial view of the turbine ring 1 which is actually a complete ring.

As shown on the figures 2 and 3 which respectively show a schematic exploded perspective view and a sectional view of the turbine ring assembly of the figure 1 , the sectional view being along a sectional plane comprising the radial direction D _R and the axial direction D _A , each ring sector 10 has, along a plane defined by the axial D _A and radial D _{R directions} , a section substantially shaped like the inverted Greek letter π. The section in fact comprises an annular base 12 and upstream and downstream radial hooking tabs, respectively 14 and 16. The terms “upstream” and “downstream” are used here with reference to the direction of flow of the gas flow in the turbine. represented by the arrow F on the figure 1 . The tabs 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 to 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 stream flow stream in the turbine. The terms “internal” and “external” are used here with reference to the radial direction D _R in the turbine.

The upstream and downstream radial hooking tabs 14 and 16 extend projecting, in the direction D _R , from the outer 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 over the entire circumferential length of ring sector 10.

As shown on figures 1 to 3 , the ring support structure 3 which is integral with a turbine housing 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 integral with the central ferrule 31. The second annular radial flange 36 comprises a first portion 363, a second portion 364, and a third portion 365 lying between the first portion 363 and the second portion 364. The first portion 363 s' 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 hooking 16. The second portion 364 is thinned with respect 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 do not over-stress 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 integral with the central ferrule 31.

As shown on 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 attached to the first annular radial flange 32. The first and second annular flanges 33 and 34 are arranged upstream of the turbine ring 1 with respect to the direction F of flow of the gas flow in the turbine.

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

Further, 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 hooking lug 14 of each of the ring sectors 10 making up the turbine ring 1, and the second portion 334 of the first annular flange 34 is rests against at least part of the first annular radial flange 32.

The radial retention of the ring 1 is ensured by the first annular flange 33 which is pressed against the first annular radial flange 32 of the ring support structure 3 and on the upstream radial hooking lug 14. The first annular flange 33 provides the seal between the vein cavity and the cavity outside the vein of the ring.

The second annular flange 34 has a free first end 341 and a second end 342 removably attached to the ring support structure 3.

The second annular flange 34 is dedicated to taking up 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 causing this to transit. force towards the casing line which is more robust mechanically, that is to say towards the line of the ring support structure 3 as illustrated by the force arrow E shown on the figure 3 .

In the first embodiment illustrated on figures 1 to 3 , the first annular flange 33 and the second annular flange 34 are in contact at their second end respectively 332 and 342. The second end 342 of the second annular flange 34 comprises a contact stop 340 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 second end 342 of the second annular flange 34 is fixed to the first annular radial flange 32 via the stop and the first annular flange 33.

In addition, the second end 342 of the second annular flange 34 comprises a support ring 346 projecting upstream in the axial direction D _A.

In other words, the second annular flange 34 has an upstream face 34a receiving the gas flow F and a downstream face 34b facing the first annular flange 33, and the second end 342 of the second annular flange 34 comprises a contact stop 340 extending in the axial direction D _A from the downstream face 34b towards the downstream, that is to say towards the first annular flange 33, and a bearing ring 346 extending in the axial direction D _A from the upstream face 34a of the second annular flange 34.

The support ring 346 has an internal face 346a and an external face 346b, a free first end 3461, and a second end 3462 integral with the upstream face 34a of the second annular flange 34, the first end 3461 being upstream of the second end 3462 when the impeller ring assembly is mounted. The support ring 346 comprises, on its first end 3461, a radial support 348 projecting from the outer face 346b of the support ring 346. The radial support 348 is in contact with the central ring 31 of the structure of ring holder 3.

The support ring 346 provides greater resistance to tilting induced by the DHP force. The support ring 346 takes up the significant tangential stresses caused by the DHP force and thereby limits the tilting of the second annular flange 34.

The second annular flange 34 provides 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.

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

The second annular flange 34 is shrunk onto the central ferrule 31 of the ring support structure 3, the shrinking being carried out, with a hand, between the central ferrule 31 and a portion 345 projecting from the contact stop 340, in the radial direction D _R away from the axis of revolution of the ring, that is to say going towards the central ferrule 31, and, on the other hand, between the central ferrule 31 and the radial support 348.

The first annular flange 33 is shrunk onto the first annular radial flange 32 of the ring support structure 3. More precisely, the shrinking 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 at mid-height of the first annular radial flange 32, the two radial surfaces 335 and 325 being opposite, and at the same time in contact, with each other 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 over the face of the first annular flange 33 opposite the first annular flange 32 and the first radial fixing lug 14. More specifically, the radial surface 335 of the first annular flange 33 may be formed anywhere on the portion of the first annular flange 33 intended to contact 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 press the ring in a low radial position, that is to say towards the vein, in a deterministic manner. There is in fact 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 A schematic sectional view of a second embodiment of the turbine ring assembly is shown.

The second embodiment of the invention illustrated in figure 4 differs from the first embodiment illustrated in the figures 1 to 3 mainly in that the second annular flange 34 is not in direct contact with the first annular flange 33.

The first annular flange 33 and the second annular flange 34 are connected by an omega seal 40 making it possible to ensure the seal between the vein cavity and the cavity outside the vein upstream of the ring 1.

In the second embodiment, the second annular flange 34 does not include a contact stop 340 unlike the first embodiment illustrated in the figures. figures 1 to 3 .

The support ring 346 of the second annular flange 34 also comprises a radial support 348 projecting from the outer face 346b of the support ring 346. On the figure 4 , the radial support 348 is disposed on an upstream part of the support ring 346 without being directly on the first end 3461, the radial support 348 can be disposed over the entire length of the outer face 34b in the axial direction D _A , the most upstream position allowing more resistance.

In the second embodiment illustrated in figure 4 , the first annular flange 33 is fixed to the first annular flange 32 of the ring support structure 3 by means of screws 60 and fixing nuts 61, the screws 60 passing through the second portion 334 of the first annular flange 33 as well as the upstream annular radial flange 32.

The radial support 348, projecting in the radial direction D _R in a direction away from the axis of revolution of the ring 1, comprises a first face 348a extending in the radial direction D _R and receiving the flow F and a second face 348b extending in the radial direction D _R and opposite to the first face 348a, the second face 348b forming an axial shoulder resting on a radial rib 314 of the central shell 31. The radial rib 314 s 'projecting in the radial direction D _R from the central ferrule 31 in a direction going towards the axis of revolution of the ring 1. The radial rib 314 comprises a first face 314a extending in the radial direction D _R in sight of the flow F and in contact with the second face 348b of the radial support 348, and a second face 314b extending in the radial direction D _R and opposite to the first face 314a.

The axial shoulder formed by the second face 348b of the radial support 348 of the second annular flange 34 is pressed against the radial rib 314 of the central ferrule 31 of the ring support structure 3. A DHP casing, not shown on the figure 4 , located upstream of the second annular flange 34 ensures a locking in the axial direction D _A of the second annular flange 34 on the other side of the radial rib 314. The second annular flange 34 is thus held axially in position between the radial rib 314 and the DHP casing upstream of the second annular flange 34.

At the radial level, there is a functional clearance between the radial support 348 of the second annular flange 34 and the central ferrule 31 of the ring support structure 3. This clearance has no influence on the behavior of the assembly. , in particular in dynamics since the second annular flange 34 remains static during the operation of the engine. In addition, its radial positioning has no influence on the radial positioning of the other parts.

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

The third embodiment illustrated in figure 5 differs from the first embodiment illustrated in 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 6 A sectional view of a fourth embodiment of the turbine ring assembly is shown.

The fourth embodiment illustrated in figure 6 differs from the first embodiment illustrated in 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} , over 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 fastening part 20, the screws 38 being omitted.

In each of the embodiments of the invention illustrated on figures 1 to 6 , 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 hooking tabs 14 and 16 so as to maintain the latter between the first annular flange 33 and the second annular radial flange 36.

In the first and second embodiments illustrated on figures 1 to 4 , to keep 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 lug 14 and the first annular flange 33, and two second pins 120 cooperating with the downstream hooking lug 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 two first 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 hooking tabs 14 and 16 comprises a first end, 141 and 161, integral with the outer face 12b of the annular base 12 and a second end, 142 and 162, free. The second end 142 of the upstream radial 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 downstream radial attachment tab 16 comprises two second ears 18 each comprising an orifice 180 configured to receive a second pin 120. The first and second ears 17 and 18 project out in the radial direction D _R of the turbine ring 1 respectively from the second end 142 of the upstream radial attachment tab 14 and of the second end 162 of the downstream radial attachment tab 16.

The orifices 170 and 180 can be circular or oblong. Preferably, the set of orifices 170 and 180 comprises 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 being able to move tangentially (in particular in the event of contact by the blade). The oblong orifices make it possible to accommodate the differential expansions between the CMC and the metal. CMC has a much lower coefficient of expansion than metal. When hot, the lengths in the tangential direction of the ring sector and of 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. Have slotted holes throughout ring allows the pin to slide in this hole and to avoid the phenomenon of over-stress mentioned above. Therefore, two drilling diagrams can be imagined: a first drilling diagram, for a case with three lugs, would include a radial circular hole on one radial hooking flange and two tangential oblong holes on the other radial hooking flange , and a second drilling diagram, for a case with at least four ears, would include a circular orifice and an oblong orifice per radial hooking flange facing each other. Other additional cases can also be considered.

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

As shown on the figure 5 , in the third embodiment, each ring sector 10 has, along a plane defined by the axial D _A and radial D _{R directions} , 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 stream flow stream in the turbine. Upstream and downstream radial hooking tabs 140, 160 substantially S-shaped extend, in the radial direction D _R , from the outer face 12b of the annular base 12 over the entire width thereof and at the bottom. 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, integral with the annular base 12 and a second free end, respectively referenced 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 annularly. In this second configuration where the ends are rectilinear and the lugs annular, 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 cases of occasional support. The second end 1620 of the downstream radial hook 160 is held between a portion 3610 of the second annular radial flange 36 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, that is to say the screw opposite to the screw head. The second end 1410 of the upstream radial hooking tab 140 is held between a portion 3310 of the first annular flange 33 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 fourth embodiment illustrated in figure 6 , the ring sector 10 comprises an axial attachment tab 17 'extending between the upstream and downstream radial attachment tabs 14 and 16. The axial attachment tab 17' extends more precisely, in the direction axial D _A , between the second end 142 of the upstream radial attachment lug 14 and the second end 162 of the downstream radial attachment lug 16.

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

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

The fastener 20 further comprises an orifice 21 provided with an internal thread cooperating with a thread of the screw 19 for fixing the fastener 20 to the screw 19. The screw 19 comprises a screw head 190 whose diameter is greater than 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 fastener 20.

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

In a variant, the radial retention of the ring downwards can be ensured by means of four radial pins pressed against the axial hooking lug 17 ', and the radial upward retention of the ring can be ensured. by a pickaxe head, integral with the screw 19, placed under the ring in the cavity between the axial hooking lug 17 'and the external face 12b of the annular base.

In each of the embodiments of the invention illustrated on figures 1 to 6 , each ring sector 10 further comprises rectilinear bearing surfaces 110 mounted on the faces of the upstream and downstream radial hooking tabs 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 attachment lug 14 and on the downstream face 16b of the downstream radial attachment lug 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 hooking lug 14 and the first annular flange 33, on the one hand, and between the downstream radial hooking lug 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 bending in the turbine ring 1.

We now describe a method of making a turbine ring assembly corresponding to that shown in Figure figure 1 , that is to say according to the first embodiment illustrated in the figures 1 to 3 .

Each ring sector 10 described above is made of a ceramic matrix composite material (CMC) by forming a fiber preform having a shape close to that of the ring sector and densifying the ring sector with a ceramic matrix. .

For producing the fiber preform, one can use ceramic fiber threads, for example SiC fiber threads such as those sold by the Japanese company Nippon Carbon under the name “Hi-NicalonS”, or carbon fiber threads. .

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

The weaving can be of the interlock type, as illustrated. Other three-dimensional or multi-layered weaves can be used, for example multi-plain 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 gas infiltration (CVI) which is well known in France. self. In a variant, the textile preform can be hardened a little by CVI so that it is sufficiently rigid to be handled, before making liquid silicon rise by capillary action in the textile in order to make the densification (“Melt Infiltration”).

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

The ring support structure 3 is for its part made of a metallic material such as a Waspaloy® or inconel 718® or alternatively C263® alloy.

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

For this, the ring sectors 10 are assembled together on an annular tool of the “spider” type 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 ears 18 of the downstream radial hooking flanges 16 of each ring sector 10 making up the ring. 1.

All the first pins 119 are then placed in the orifices 170 provided in the first ears 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 hooping to the support structure d Ring 3. The DHP force exerted in the direction of flow F reinforces this fixation during engine operation.

It should be noted that in the case of a method of making a turbine ring assembly corresponding to that shown in Figure figure 4 , the assembly is carried out by fixing the first flange 33 to the ring support structure 3 by bolted connection, then by putting the omega seal 40 in place in the groove provided for this purpose in the first flask 33 before coming to assemble the second flange 34 to the ring support structure 3.

To maintain 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 hooking tabs 14 of each ring sector 10 making up ring 1.

The ring 1 is thus held in position axially by means of the first annular flange 33 and of the second annular radial flange 36 bearing respectively upstream and downstream on the rectilinear bearing surfaces 110 of the radial hooking 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 hooking lug 14 to mitigate the effect of differential expansion between the material CMC of ring 1 and the metal of the ring support structure 3. The first ring flange 33 is maintained in axial stress by mechanical elements placed upstream as illustrated in dotted lines on the figure 3 .

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

The invention thus provides a turbine ring assembly making it possible to maintain each ring sector in a deterministic manner while allowing, on the one hand, the ring sector, and by extension the ring, to be deformed under the effects of temperature rises and pressure variations, in particular independently of the metallic parts at the interface, and, on the other hand, while improving the seal between the non-duct sector and the duct sector and by simplifying manipulations and reducing their number for mounting the ring assembly.

In addition, the invention provides a turbine ring assembly comprising an upstream annular flange dedicated to the absorption of the DHP force and thus to induce low levels of forces in the CMC ring, a contact stop between the annular flange dedicated to the absorption of the DHP force and the annular flange used to hold the ring, the stop making it possible to ensure non-contact of the lower parts of the two flanges during tilting of the upstream flange. 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 excessive axial forces on the ring.

Claims (7)

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), and the second end (342) of the second annular flange (34) comprising an upstream bearing shroud (346) protruding upstream in the axial direction (D_A), the upstream bearing shroud (346) having a radial bearing (348) in contact with the central shroud (31) of the ring support structure (3).
2. The assembly according to claim 1, wherein the second annular flange (34) comprises a contact abutment (340) extending in the axial direction (D_A) of the turbine ring (1) and separating the second end (342) of the second annular flange (34) from the second end (332) of the first annular flange (33).
3. The assembly according to claim 1, further comprising an omega seal (40) mounted between the first end (341) of the second annular flange (34) and the first end (331) of the first flange (33), the second annular flange (34) being fastened to the ring support structure (3) on a portion upstream of the radial bearing (348).
4. The assembly according to any of claims 1 to 3, wherein the ring sector (10) has an inverted Greek letter section pi (π) 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).
5. The assembly according to any of claims 1 to 3, wherein the ring sector (10) has a section with an elongated K-shape 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.
6. The assembly according to any of claims 1 to 3, wherein the ring sector (10) has, on at least one radial range of the ring sector, 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').
7. A turbomachine comprising a turbine ring assembly (1) according to any one of claims 1 to 6.

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