The invention relates to a turbine ring assembly for a turbomachine in which the assembly comprises a plurality of angular ring sectors placed end to end to form a turbine ring made of ceramic matrix composite material.

A field of application of the invention is in particular that of aeronautical gas turbine engines.

Prior technique

Ceramic matrix composite materials, or CMCs, are known to retain their mechanical properties at high temperatures, which makes them suitable for forming hot structural elements.

In aeronautical gas turbine engines, the improvement of efficiency and the reduction of certain polluting emissions lead to seeking operation at ever higher temperatures. 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 very hot fluxes, typically higher than the temperature bearable by the metallic material. This cooling has a significant impact on engine performance since the cooling flow used is taken from the main flow of the engine. Furthermore, the use of metal for the turbine ring limits the possibilities of increasing the temperature at the level of the turbine,

Furthermore, a metal turbine ring assembly deforms under the effect of heat fluxes, which modifies the clearances at the level of the flow path and, consequently, the performance of the turbine.

This is why the use of CMCs for different hot parts of engines has already been considered, especially since CMCs have the advantage

additional density lower than that of refractory metals traditionally used.

Thus, the production of turbine ring sectors in a single piece in CMC is described in particular in document US 2012/0027572. The ring sectors comprise an annular base whose inner face defines the inner face of the turbine ring and an outer face from which extend radially two legs whose ends are held between the two flanges of a structure metal ring support.

The use of CMC ring sectors thus makes it possible to significantly reduce the ventilation necessary for cooling the turbine ring. However, the CMC having a different mechanical behavior from a metallic material, its integration as well as the way of positioning it within the turbine had to be redesigned. Indeed, the CMC does not support shrink-fit assemblies (usually used for metal rings) and its thermal expansion is lower than a metal material.

In addition, the use of CMC ring sectors increases the number of parts required for its integration on the turbine casing, which increases the cost and weight of the assembly and requires complex assembly operations (shrinking of bushings, mounting pins, etc.).

Disclosure of Invention

The main object of the present invention is therefore to provide a turbine ring assembly which does not have the aforementioned drawbacks.

This object is achieved by a turbine ring assembly extending around an axis, comprising a plurality of ring sectors of ceramic matrix composite material forming a turbine ring and a ring support structure maintained by a turbine casing, each ring sector comprising a base from which extend radially outwards an upstream leg and a downstream leg spaced axially from each other, the ring support structure comprising a spacer having a flange against which the downstream leg of the ring sectors is held, a first upstream flange against which the upstream leg of the ring sectors is held, and, upstream of the first upstream flange, a second upstream flange of recovery of forces against which the first upstream flange is held.

The turbine ring assembly according to the invention is remarkable in particular in that the CMC ring is held directly on the turbine casing by means of a ring support structure without resorting to a ring holder. In particular, compared to the prior art, the assembly according to the invention has no ring support casing and the radial studs enabling the ring support structure to be held on this casing are eliminated.

In addition, the ring support structure is made in several separate parts independent of each other, which allows assembly of this structure by angular sectors and no longer in a crown. The assembly of the turbine ring assembly is thereby simplified and does not require any tools. Furthermore, the manufacturing tolerances are less strict, the spacers making it possible to compensate for the differences between the ring sectors, which a 360° flange cannot do. In addition, the elimination of radial pins reduces the machining operations of the parts of the ring support structure. This results in a saving of parts, and therefore a reduction in the weight and cost of the assembly.

Advantageously, the ring support structure further comprises an air diffuser intended to diffuse cooling air on an external face of the base of the ring sectors. In this case, the air diffuser of the ring support structure may comprise a flange held between the spacer and the first upstream flange.

Preferably, the ring support structure further comprises a plurality of fixing means screwed into the spacer and crossing from upstream to downstream to fix between them the first upstream flange, the second upstream flange and the flange of the diffuser. 'air.

Also advantageously, the assembly further comprises upstream axial pins intended to hold the first upstream flange of the ring support structure against the upstream leg of the ring sectors. Likewise, the assembly preferably further comprises downstream axial pins intended to hold the flange of the spacer of the ring support structure against the downstream lug of the ring sectors.

The spacer of the ring support structure may comprise an upstream hook for mounting said ring support structure on the turbine casing. Likewise, the first flange upstream of the ring support structure may comprise a hook for mounting said ring support structure on the turbine casing.

Additionally, the ring support structure strut may further include a downstream hook for retaining a low pressure turbine nozzle positioned downstream of the turbine assembly.

The invention also relates to a turbine engine comprising an assembly as defined above.

Brief description of the drawings

[Fig. 1] Figure 1 is a longitudinal sectional view of a turbine ring assembly according to the invention.

[Fig. 2] Figure 2 shows a schematic and perspective view of the turbine assembly of Figure 1.

Description of embodiments

FIG. 1 represents, in longitudinal section, a turbine ring assembly 2 according to the invention.

This assembly 2 comprises in particular a turbine ring 4 made of ceramic matrix composite (CMC) material centered on a longitudinal axis XX and a ring support metal structure 6. The turbine ring 4 surrounds a set of turbine blades 8.

Furthermore, the turbine ring 4 is formed of a plurality of angular ring sectors 10 which are placed end to end circumferentially to form a ring. In Figure 1, the arrow DA indicates the axial direction of the turbine ring while the arrow DR indicates the radial direction of the turbine ring.

Each angular ring sector 10 has a section substantially in the shape of an inverted Pi (or TT) with a base 12 provided with an internal face 12a which defines an angular portion of the internal face of the turbine ring and which is typically provided with an abradable coating layer 14 also acting as a thermal and environmental barrier.

Two legs - namely an upstream leg 16 and a downstream leg 18 - extend radially from the outer face 12b of the base 12 opposite the inner face 12a. These lugs 16, 18 extend over the entire width of the ring sector 10 (in the circumferential direction).

According to the invention, the ring support structure 6 is made by assembling a plurality of separate parts (ie independent) from each other.

As more precisely shown in Figure 2, these parts include in particular a spacer 20, a first upstream flange 22, a second upstream flange 24 for taking up forces, and an air diffuser 26.

The spacer 20 comprises a flange 20a against which the downstream tab 18 of the ring sectors 10 is held by means of a plurality of downstream axial pins 28 regularly distributed around the longitudinal axis XX of the ring.

The spacer 20 also comprises an upstream hook 20b which is intended to engage in a downstream hook 30 of a turbine casing 32 in order to allow the mounting of the ring support structure directly on the turbine casing.

The spacer 20 also comprises a downstream hook 20c which is intended to engage in a corresponding hook (not shown in the figures) of a low-pressure turbine distributor 34 located downstream of the ring assembly 2 of turbine in order to allow the maintenance of it.

It will be noted that the spacer 20 can be a part of revolution (that is to say of 360°) or else be made by assembling a plurality of spacer sectors placed end to end.

The upstream leg 16 of the ring sectors 10 is held against the first upstream flange 22.

The first upstream flange 22 also includes a hook 22a which is intended to engage in an upstream hook 36 of the turbine casing 32 in order to allow the mounting of the ring support structure directly on the turbine casing.

The first upstream flange 22 can be a part of revolution (that is to say of 360°) or else be produced by an assembly of two half-flanges of 180° each.

The first upstream flange 22 is held upstream against a second upstream flange 24 for taking up forces. The latter is intended to take up the forces of a high-pressure turbine distributor 38 which is positioned upstream of the turbine ring assembly.

This front flange 24 can be a part of revolution (that is to say of 360°) or be a sectorized part.

Finally, the air diffuser 26 is intended to diffuse cooling air on the external face 12b of the base 12 of the ring sectors. For this purpose, it comprises a cavity 26a positioned around the base 12 of the ring sectors, supplied with cooling air taken from a stage of the compressor of the turbomachine and opening out towards the external face of the base of the ring sectors by through a multi-perforation of its walls (not shown in the figures).

The air diffuser 26 also comprises a flange 26b coming directly into axial support against the upstream leg 16 of the ring sectors 10.

The ring support structure 6 further comprises a plurality of fixing means 40 (for example bolted connections) which are screwed into the spacer 20 and cross from upstream to downstream to fix between them the first upstream flange 22, the second upstream flange 24 for taking up forces and the flange 26b of the air diffuser 26.

The turbine ring assembly 2 further comprises upstream axial pins 42 which are intended to hold the first upstream flange 22 of the ring support structure against the upstream leg 16 of the ring sectors 10. These upstream pins 42 are regularly distributed around the longitudinal axis XX of the ring.

In this way, the upstream and downstream legs 16, 18 of the ring sectors 10 are held between the first upstream flange 22 and the flange 20a of the spacer 20 of the ring support structure 6.

It will be noted that the clearance at the top of the turbine blades 8 can be controlled by acting on the thicknesses of the turbine casing 32 or by providing the latter with control bosses (not shown in the figures).

WE CLAIMS

Claim 1] Turbine ring assembly (2) extending around

an axle (XX), comprising a plurality of ring sectors (10) made of ceramic matrix composite material forming a turbine ring (4) and a ring support structure (6) held by a turbine casing (32), each ring sector (10) comprising a base (12) from which extend radially outwards an upstream leg (16) and a downstream leg (18) spaced axially from one on the other, the ring support structure (6) comprising a spacer (20) having a flange (20a) against which the downstream tab (18) of the ring sectors (10) is held, a first upstream flange (22 ) against which the upstream leg of the ring sectors is held, and upstream of the first upstream flange (22), a second upstream flange (24) for picking upforces against which the first upstream flange (22) is maintained.

[Claim 2] An assembly according to claim 1, wherein the

ring support structure (6) further comprises an air diffuser (26) for diffusing cooling air on an outer face (12b) of the base (12) of the ring sectors (10) .

[Claim 3] An assembly according to claim 2, wherein the

air diffuser (26) of the ring support structure (6) comprises a flange (26b) held between the spacer (20) and the first upstream flange (22).

[Claim 4] An assembly according to claim 3, wherein the

ring support structure (6) further comprises a plurality of fixing means (40) screwed into the spacer (20) and crossing from upstream to downstream to fix between them the first upstream flange (22), the second upstream flange (24) and the flange (26b) of the air diffuser (26).

[Claim 5] An assembly according to any one of claims 1 to

4, further comprising upstream axial pins (42) intended to hold the first upstream flange (22) of the ring support structure against the upstream leg (16) of the ring sectors (10).

[Claim 6] An assembly according to any one of claims 1 to

5, further comprising downstream axial pins (28) intended to hold the flange (20a) of the spacer (20) of the ring support structure (6) against the downstream lug (18) of the ring sectors (10).

[Claim 7] An assembly according to any one of claims 1 to

6, wherein the spacer (20) of the ring support structure (6) comprises an upstream hook (20b) for mounting said ring support structure (6) on the turbine casing (32) .

[Claim 8] An assembly according to any one of claims 1 to

7, in which the first upstream flange (22) of the ring support structure (6) comprises a hook (22a) for mounting said ring support structure (6) on the turbine casing (32) .

[Claim 9] Assembly according to any one of claims 1 to 7, in which the spacer (20) of the ring support structure (6) further comprises a downstream hook (20c) for the maintenance of a low pressure turbine nozzle (34) positioned downstream of the turbine assembly.

[Claim 10] Turbomachine comprising an assembly (2) according to any one of claims 1 to 9.