EP3390783A1

EP3390783A1 - Turbine ring assembly with support when cold and when hot

Info

Publication number: EP3390783A1
Application number: EP16825493.6A
Authority: EP
Inventors: Clément ROUSSILLE; Thierry TESSON
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2015-12-18
Filing date: 2016-12-14
Publication date: 2018-10-24
Anticipated expiration: 2036-12-14
Also published as: US20180363507A1; CN108699918B; FR3045715A1; CN108699918A; US10378386B2; WO2017103451A1; EP3390783B1; FR3045715B1

Abstract

A plurality of CMC ring sectors forms a turbine ring. A support structure (3) comprises two annular flanges (32; 36). Each ring sector has an outer face with two tabs (14; 16) held between the annular flanges (32; 36) of the support structure. Each tab comprises a projecting portion (140; 160) facing a flange cooperating with a housing (320; 360) present on the flange, and an opening (15; 17) in which there is accommodated, with a clearance, a holding element (40a; 40b) that has a higher thermal expansion coefficient than the CMC and is secured to the flange. The housing has two portions (360a; 360b) abutting on the projecting portion and inclined relative to the radial direction (DA) and the axial direction (RA).

Description

Turbine ring assembly with cold and hot hold

Background of the invention

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

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

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 particularly hot flows. This cooling has a significant impact on the engine performance 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, which would however improve the performance of aircraft engines.

Furthermore, a set of metal turbine ring deforms under the effect of heat flow, which changes the clearance at the flow path and, therefore, the performance of the turbine.

This is why the use of CMC for different hot parts of the engines has already been considered, especially since CMCs have the additional advantage of lower density than refractory metals traditionally used.

The use of ring segments in CMC significantly reduces the ventilation required to cool the turbine ring. However, maintaining the ring sectors in position remains a problem in particular with respect to the differential expansions that can occur between the metal support structure and the CMC ring sectors. In addition, another problem lies in controlling the shape of the vein both cold and hot without generating too much stress on the ring sectors. Also known is WO 2015/191186 which discloses a turbine ring assembly.

There is therefore a need to improve existing turbine ring assemblies employing a CMC material in order to maintain the ring sectors in position despite the differential expansions while limiting the intensity of the mechanical stresses to the sectors. CMC ring are subjected during operation.

Object and summary of the invention

For this purpose, the invention provides, in a first aspect, a turbine ring assembly comprising a plurality of ceramic matrix composite ring sectors forming a turbine ring and a ring support structure having two annular flanges, each ring sector having an annular base portion with an inner face defining the inner face of the turbine ring and an outer face from which extend at least two legs, the legs of each sector of ring being held between the two annular flanges of the ring support structure,

characterized in that each tab of the ring sectors has a portion projecting on its face facing one of the two annular flanges, this projecting portion cooperating with a housing present on the annular flange,

and in that each leg of the ring sectors comprises at least one opening in which is housed a portion of a holding member integral with the annular flange located opposite said tab, a clearance being present between the opening of said tab and the portion of the holding member in said opening, said holding member being of a material having a thermal expansion coefficient greater than the thermal expansion coefficient of the ceramic matrix composite material of the ring sectors.

In the ring assembly according to the invention, the ring sectors are kept cold due to the cooperation between the protruding portions and the housings present on the annular flanges opposite them. Maintaining ring areas by this relief cooperation may no longer be ensured hot due to the expansion of the annular flanges. When hot, the holding force is resumed by the expansion of the holding elements, which expansion does not entail significant stress on the ring sectors because of the presence of a cold clearance between the holding elements and the openings on the legs of the ring sector.

In an exemplary embodiment, the housing of the annular flange may have at least one inclined portion forming, when observed in meridian section, a non-zero angle with respect to the radial direction and the axial direction and bearing on the portion protruding cooperating with said housing.

The radial direction corresponds to the direction along a radius of the turbine ring (straight connecting the center of the turbine ring to its periphery). The axial direction corresponds to the direction along the axis of revolution of the turbine ring and the flow direction of the gas flow in the vein.

The implementation of such inclined portions at the annular flanges of the ring support structure contributes to compensate for the differences in expansion between the annular flanges and the legs of the ring sectors and thus to reduce the mechanical stresses to which the sectors ring are subjected during operation.

In an exemplary embodiment, the housing of the annular flange may have at least a first and a second inclined portions bearing on the projecting portion cooperating with said housing, said first and second inclined portions may each form, when observed in section meridian, a non-zero angle with respect to the radial direction and the axial direction.

In particular, the first inclined portion may bear against the radially inner half of the projecting portion and the second inclined portion may bear against the radially outer half of the projecting portion.

In an exemplary embodiment, said at least one inclined portion may form an angle of between 30 ° and 60 ° with the radial direction.

In an exemplary embodiment, the ratio (diameter of the part of the holding element present in said opening) / (diameter of said opening) may be between (l + a _C c) / (l + Qm) and l, lx (l + acMc) / (l + a _m ) where a _m denotes the coefficient of thermal expansion of said portion of the holding member and OCMC denotes the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors, with _m and O _C MC being measured at 900 ° C and expressed in 10 ^" ⁶ ° C ^{" 1} .

Such values for the ratio between the diameter of the part of the holding element present in said opening and the diameter of said opening make it possible to obtain a maintenance of the optimum ring sectors when hot because of the integral or substantially integral filling. the game present between the opening and the holding member obtained by expansion of the holding member.

In an exemplary embodiment, each ring sector may have a Pi shape in axial section.

The present invention also relates to a turbomachine comprising a turbine ring assembly as described above.

Brief description of the drawings

Other characteristics and advantages of the invention will emerge from the following description of a particular embodiment of the invention, which is not limiting, with reference to the appended drawings, in which:

FIG. 1 is a view in radial section of an exemplary turbine ring assembly according to the invention,

FIG. 2 is a detail of FIG. 1, and

- Figures 3 and 4 schematically illustrate the mounting of a ring sector in the ring support structure of the ring assembly of Figure 1.

Detailed description of embodiments

FIG. 1 shows a high pressure turbine ring assembly comprising a turbine ring 1 made of ceramic matrix composite material (CMC) and a metal ring support structure 3. The turbine ring 1 surrounds a set of blades 5. The turbine ring 1 is formed of a plurality of ring sectors 10, Figure 1 being a radial sectional view along a plane passing between two sectors of consecutive rings. Ring sectors 10 present in the example illustrated a Pi shape in axial section. The arrow DA indicates the axial direction with respect to the turbine ring 1 while the arrow DR indicates the radial direction with respect to the turbine ring 1.

Each ring sector 10 has a substantially inverted π-shaped section with an annular base 12 whose inner face coated with a layer 13 of abradable material defines the flow stream of gas flow in the turbine. Upstream and downstream tabs 14, 16 extend from the outer face of the annular base 12 in the radial direction DR. The terms "upstream" and "downstream" are used herein with reference to the flow direction of the gas flow in the turbine (arrow F).

The ring support structure 3 which is integral with a turbine casing 30 comprises an annular upstream radial flange 32 and an annular downstream radial flange 36. The lugs 14 and 16 of each ring sector 10 are held between the flanges. 32 and 36. Each of the annular flanges 32 and 36 defines a housing 320 and 360. The housings 320 and 360 cooperate with a respective projecting portion 140 and 160 to ensure the cold maintenance of the ring sectors 10 on the structure ring support 3. By "cold" is meant in the present invention, the temperature at which the ring assembly is located when the turbine does not run, that is to say at room temperature which may be for example about 25 ° C. The protruding portion 140 is located on the face 14a of the lug 14 facing the flange 32. The projecting portion 160 is, for its part, located on the face 16a of the lug 16 located opposite the flange 36 In the illustrated example, each tab 14 and 16 comprises a portion of extra thickness forming the projecting portion 140 or 160.

The housings 320 and 360 each have, in the illustrated example, two inclined portions. Thus, as illustrated in Figure 2, the housing 360 has a first inclined portion 360a and a second inclined portion 360b each forming a non-zero angle with the radial direction DR and axial DA. The first and second inclined portions 360a and 360b bear on the projecting portion 160 cooperating with said housing 360. The first 360a and second 360b inclined portions may not be parallel to each other, as illustrated. The housing 360 may furthermore have a radial portion 360c extending along the radial direction DR and located between the first inclined portion 360a and the second inclined portion 360b. In the illustrated example, the first 360a and second 360b inclined portions each form, when observed in meridian section, an angle of between 30 ° and 60 ° with the radial direction DR. In FIG. 2, ai denotes the angle formed between the first inclined portion 360a and the radial direction DR, a ₂ denotes the angle formed between the first inclined portion 360a and the axial direction DA, a ₃ denotes the angle formed between the second inclined portion 360b and the radial direction DR and a ₄ designates the angle formed between the second inclined portion 360b and the axial direction DA. The first inclined portion 360a rests on the radially inner half Mi of the projecting portion 160 and the second inclined portion 360b bears against the radially outer half Me of the projecting portion 160. The housing 320 located on the upstream flange 32 has a structure similar to that just described for housing 360.

Furthermore, the ring sectors 10 are further maintained by holding elements, here in the form of locking bands 40a and 40b, for example in the form of pins 40a and 40b. A first set of locking shrouds 40a is engaged both in the annular upstream radial flange 32 and in the upstream lugs 14 of the ring sectors 10. For this purpose, each hoop 40a passes respectively through an orifice 35 formed in the radial flange. annular upstream 32 and an orifice 15 formed in each upstream lug 14, the orifices 35 and 15 being aligned during the assembly of the ring sectors 10 on the ring support structure 3. In the same way, a second set of frets 40b is engaged both in the annular downstream radial flange 36 and in the downstream lugs 16 of the ring sectors 10. For this purpose, each hoop 40b passes respectively through an orifice 37 formed in the annular downstream radial flange 36 and a orifice 17 formed in each downstream tab 16, the orifices 37 and 17 being aligned during assembly of the ring sectors 10 on the ring support structure 3.

The locking frets 40a and 40b are made of a material having a coefficient of thermal expansion greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors 10. The locking frets 40a and 40b may for example be made of metallic material, for example alloy AMI or Inconel 718. A game J is present cold between the frets of block 40a, respectively 40b, and the orifices 15, 17 respectively, of the tabs 14, respectively 16. The expansion of the locking bands 40a and 40b in the orifices 15 and 17 contributes to the hot maintenance of the ring sectors 10 on the structure ring support 3 reducing or even filling the clearance J. By "hot" means here the temperatures to which the tabs of the ring sectors during the operation of the turbine, these temperatures can be understood between 600 ° C and 900 ° C. In the illustrated example, the ratio between the diameter di of the portion of the bands 40b present in the orifice 17 and the diameter d _{2 of} said orifice 17 (ie di / d ₂ ) is between (l + a _C Mc) / (l + o _m ) and l, lx (l + a _C M _C ) / (l + Om) where a _m denotes the coefficient of thermal expansion of said portion of the frets 40b and a _C Mc denotes the coefficient of thermal expansion of the This feature can also be verified for the ratio (diameter of the portion of the hoop 40a present in the orifice 15) / (diameter of the orifice 15).

In addition, the inter-sector sealing is provided by sealing tabs housed in grooves facing in the opposite edges of two neighboring ring sectors. A tongue 22a extends over almost the entire length of the annular base 12 in the middle portion thereof. Another tab 22b extends along the tab 14 and on a portion of the annular base 12. Another tab 22c extends along the tab 16. At one end, the tab 22c abuts the tab 22a and on the tongue 22b. The tabs 22a, 22b, 22c are for example metallic and are mounted with cold clearance in their housings to ensure the sealing function at the temperatures encountered in operation.

Conventionally, ventilation orifices 33 formed in the flange 32 make it possible to bring cooling air to the outside of the turbine ring 1.

The assembly of an exemplary turbine ring assembly as shown in FIG. 1 will now be described.

Each ring sector 10 described above is made of a ceramic matrix composite material (CMC) by forming a fibrous preform having a shape close to that of the ring sector and densifying the preform with a ceramic matrix. For the realization of the fiber preform, it is possible to use ceramic fiber yarns, for example SiC fiber yarns, such as those marketed by the Japanese company Nippon Carbon under the name "Nicalon", or carbon fiber yarns. The fibrous preform is advantageously made by three-dimensional weaving, or multilayer weaving with the provision of debonding zones enabling the parts of preforms corresponding to the lugs 14 and 16 of the sectors 10 to be spaced apart. The weaving may be of the interlock type, as illustrated. Other weaves of three-dimensional weave or multilayer can be used as for example multi-web or multi-satin weaves. Reference can be made to 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 can be achieved in particular by chemical vapor infiltration (CVI) which is well known in itself. A detailed example of manufacture of ring sectors in CMC is described in particular in document US 2012/0027572.

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

The realization of the turbine ring assembly is continued by mounting the ring sectors 10 on the ring support structure 3. The illustrated ring support structure 3 comprises at least one flange, here the flange radial downstream annular 36, which is elastically deformable in the axial direction DA of the ring. When mounting a ring sector 10, the annular downstream radial flange 36 is pulled in the direction DA as shown in Figure 3 to increase the spacing between the flanges 32 and 36 and allow the insertion of the sector. ring 10 between the flanges 32 and 36 without risk of damaging the ring sector 10. In order to facilitate the traction separation of the annular downstream radial flange 36, it comprises a plurality of hooks 39 distributed over its face 36b, face which is opposite the face 36a of the flange 36 opposite the downstream lugs 16 of the ring sectors 10. The traction in the axial direction DA exerted on the elastically deformable flange 36 is here carried out by means of a tool 50 comprising at least one arm 51 whose end comprises a hook 510 which is engaged in a hook 39 present on the outer face 36a of the flange 36. The number of hooks 39 distributed on the face 36a of the flange 36 is defined according to the number of tensile points that one wishes to have on the flange 36. This number depends mainly on the elastic nature of the flange. Other forms and arrangements of means for exerting traction in the axial direction DA on one of the flanges of the ring support structure can of course be considered within the scope of the present invention.

Once the annular flange 36 spreads in the direction DA, the ring sector 10 is inserted between the annular flanges 32 and 36. During the insertion of the ring sector 10, the projecting portion 140 is engaged in the housing 120 and the orifices 15 and 35 are aligned. The flange 36 is then released in order to introduce the projecting portion 160 into the housing 360 and to align the orifices 17 and 37. The structure illustrated in FIG. 4 is then obtained in which the ring sectors 10 are kept cold by cooperation of projecting portions 140 and 160 and housing 320 and 360. A hoop 40a is then engaged in the aligned orifices 35 and 15 respectively formed in the annular upstream radial flange 32 and in the upstream lug 14. In the same manner, a 40b is engaged in the aligned orifices 37 and 17 formed respectively in the annular downstream radial flange 36 and in the downstream lug 16. The frets 40a and 40b are force-fitted into the annular flanges 32 and 36 to ensure their maintenance at cold (mounting H6P6 for example or other tight fixtures). Each lug 14 or 16 of ring sector may comprise one or more orifices for the passage of one or more frets.

In cold, the ring sectors 10 are maintained by cooperation between the protruding portions 140 and 160 and the housings 320 and 360. When hot, the expansion of the annular flanges 32 and 36 may no longer make it possible to maintain the sectors ring 10 at the housing 320 and 360. The hot maintenance of the ring sectors 10 is then ensured by the expansion of the bands 40a and 40b in the orifices 15 and 17 which reduces or cancels the game J.

The expression "understood between ... and ..." must be understood as including boundaries.

Claims

A turbine ring assembly comprising a plurality of ring sectors (10) of ceramic matrix composite material forming a turbine ring (1) and a ring support structure (3) having two annular flanges (32). 36), each ring sector (10) having an annular base portion (12) with an inner face defining the inner face of the turbine ring and an outer face from which at least two legs extend. (14; 16), the tabs (14; 16) of each ring sector (10) being held between the two annular flanges (32; 36) of the ring support structure (3), characterized in that each tab (14; 16) of the ring sectors (10) has a protruding portion (140; 160) on its face (14a; 16a) facing one of the two annular flanges (32; 36); protruding portion (140; 160) cooperating with a housing (320; 360) on the annular flange (32; 36);

and in that each lug (14; 16) of the ring sectors (10) has at least one opening (15; 17) in which is housed a portion of a holding member (40a; 40b) integral with the flange ring (32; 36) facing said lug (14; 16), a clearance (J) being present between the opening (15; 17) of said lug (14; 16) and the portion of the lug element (14; holding (40a, 40b) in said opening (15; 17), said holding member (40a; 40b) being of a material having a coefficient of thermal expansion greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring (10),

and in that the housing (320; 360) of the annular flange (32; 36) has at least one first (360a) and a second (360b) inclined portions resting on the projecting portion (140; 160) cooperating with said housing (320; 360), said first (360a) and second (360b) inclined portions each forming, when observed in meridian section, a non-zero angle (α ₁ , α ₂ , α ₃ ; a ₄ ) with respect to the radial direction (DR) and the axial direction (DA).

2. The assembly of claim 1, wherein the first inclined portion (360a) bears on the radially inner half (Mi) the protruding portion (140; 160) and wherein the second inclined portion (360b) bears on the radially outer half (Me) of the projecting portion (140; 160).

3. The assembly of claim 1 or 2, at least one of the first and second inclined portions (360a; 360b) forming an angle (Oi; a ₃ ) between 30 ° and 60 ° with the radial direction (DR).

4. An assembly according to any one of claims 1 to 3, the ratio [diameter (d of the portion of the holding member (40a; 40b) present in said opening (15; 17)] / [diameter (d ₂ ) of said aperture (15; 17)] being between (l + a _C mc) / (l + a _m ) and l, lx (l + a _c mc) / (l + a _m ) where a _m denotes the coefficient of thermal expansion of said portion of the holding member and C-CMC means the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors, a _m and O _C MC being measured at 900 ° C and expressed in 10 ^"

⁶ . ^o c

5. An assembly according to any one of claims 1 to 4, each ring sector (10) having a Pi shape in axial section.

A turbomachine comprising a turbine ring assembly according to any one of claims 1 to 5.