GB2565007A

GB2565007A - Turbine ring assembly with cold setting

Info

Publication number: GB2565007A
Application number: GB1818325.1A
Authority: GB
Inventors: Lepretre Gilles; Tesson Thierry; Lyprendi Adele; Revel Thomas
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2016-05-09
Filing date: 2017-05-04
Publication date: 2019-01-30
Anticipated expiration: 2037-05-04
Also published as: WO2017194860A1; GB2565007B; FR3051017A1; FR3051017B1; GB201818325D0

Abstract

A turbine ring assembly comprises a plurality of ring sectors (10) made of a ceramic matrix composite material and forming a turbine ring and a ring support structure (3) comprising a first and a second annular flange (32, 36). Each ring sector having a K-shaped cross section with an internal face defining the internal face of the turbine ring and an external face from which extend a first and a second S-shaped tab (14, 16). The internal faces (14b, 16b) of the tabs (14, 16) of each ring sector (10) rest against a portion of holding elements (40, 41, 50, 51) that are secured to the annular flanges (32, 36). The annular flanges (32, 36) comprise, on their face (32a, 36a) facing the tabs (14, 16) of each ring sector (10), a plurality of clamping flanges (61, 71, 81, 91) that are distributed circumferentially on the flanges, the external faces (14a, 16a) of the tabs (14, 16) of each ring sector (10) being in contact with two clamping flanges.

Description

A TURBINE RING ASSEMBLY WITH COLD SETTING

Background of the invention

The field of application of the invention is in particular that of gas turbine aeroengines. Nevertheless, the invention is applicable to other turbine engines, e.g. industrial turbines.

Ceramic matrix composite (CMC) materials are known for conserving their mechanical properties at high temperatures, which makes them suitable for constituting hot structural elements.

In gas turbine aeroengines, improving efficiency and reducing certain polluting emissions both lead to seeking to obtain operation at ever higher temperatures. For turbine ring assemblies that are made entirely out of metal, it is necessary to cool all of the elements of the assembly, and in particular the turbine ring, which is subjected to very hot streams, typically at temperatures higher than those that can be withstood by the metal material. Such cooling has a significant impact on the performance of the engine, since the cooling stream that is used is taken from the main stream through the engine. In addition, the use of metal for the turbine ring limits the potential for increasing temperature in the turbine, even though that would enable the performance of aeroengines to be improved.

Furthermore, a metal turbine ring assembly deforms under the effect of temperature variations, thereby modifying clearances associated with the flow passage, and consequently modifying the performance of the turbine .

That is why proposals have already been made to use CMC for various hot portions of engines, particularly since CMCs present the additional advantage of density lower than the density of the refractory metals that are conventionally used.

Thus, making turbine ring sectors as a single piece of CMC is described in particular in Documents US 2012/0027572 and WO 2010/103213. Ring sectors comprise an annular base having an inside face defining the inside face of the turbine ring and an outer face from which there extend two tab-forming portions with their ends engaged in housings in a metal ring support structure .

The use of ring sectors made of CMC makes it possible to reduce significantly the amount of ventilation that is needed for cooling the turbine ring. Nevertheless, holding ring sectors in position remains a problem, in particular in the face of differential expansions that can occur between the metal support structure and the CMC ring sectors. That is why it is necessary to provide a certain minimum amount of clearance between the assembled parts. Unfortunately, such clearance degrades good control over the shape of the passage and also the behavior of ring sectors in the event of contacting the tips of blades of the turbine. In addition, the presence of any such clearance leads to problems with vibration.

Object and summary of the invention

The invention seeks to avoid such drawbacks, and for this purpose it provides a turbine ring assembly comprising both a plurality of ring sectors made of ceramic matrix composite material so as to form a turbine ring, and also a ring support structure having first and second annular flanges, the ring support structure being made of a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors, each ring sector presenting a K-shape in a section plane defined by an axial direction and by a radial direction of the turbine ring, the K-shape having a portion forming an annular base with a face on the inside in the radial direction of the turbine ring defining the inside face of the turbine ring, and with a face on the outside from which there project first and second S-shaped tabs, the tabs of each ring sector being held between the two annular flanges of the ring support structure. The ring assembly is characterized in that the face of the first tab of each ring sector that is on the inside in the radial direction of the turbine ring rests against a portion of first and second holder elements secured to the first annular flange and in that the face of the second tab of each ring sector that is on the inside in the radial direction of the turbine ring rests against a portion of third and fourth holder elements secured to the second annular flange. The ring sector is also characterized in that the first annular flange comprises a plurality of clamps on its face facing the first tab of each ring sector, the clamps being distributed circumferentially on the first flange, the face of the first tab of each ring sector that is on the outside in the radial direction of the turbine ring being in contact with two clamps, and in that the second annular flange comprises a plurality of clamps on its face facing the second tab of each ring sector, the clamps being distributed circumferentially on the second flange, the face of the second tab of each ring sector that is on the outside in the radial direction of the turbine ring being in contact with two clamps.

Because of the plurality of clamps present on the annular flanges of the ring support structure, it is possible to hold the ring sectors without clearance where they are mounted while cold on the ring support structure, the ring sectors being held firstly by contact between the inside faces of the tabs of the ring sectors and the holder elements secured to the annular flanges of the ring support structure, and secondly by contact between the outside faces of the tabs of the ring sectors and the clamps likewise present on the annular flanges of the ring support structure.

According to a particular characteristic of the turbine ring assembly of the invention, the first and second holder elements are formed respectively by first and second pegs secured to the first annular flange and in that the third and fourth holder elements are formed respectively by third and fourth pegs secured to the second annular flange.

According to a first particular aspect of the turbine ring assembly of the invention, each clamp belongs to an adjustable eccentric clamping element. By using eccentric clamping elements, it is possible to adjust the thrust while cold between the ring sectors and the ring support structure.

In a second particular aspect of the turbine ring assembly of the invention, the face of the first tab of each ring sector that is at the top in the radial direction of the turbine ring has two thrust surfaces in contact respectively with two clamps of the first annular flange, the face of the first tab of each ring sector that is at the bottom in the radial direction of the turbine ring has two rest surfaces in contact respectively with the first and second holder elements secured to the first annular flange, the two thrust surfaces and the two rest surfaces extending in a common first plane. The face of the second tab of each ring sector that is at the top in the radial direction of the turbine ring has two thrust surfaces in contact respectively with two clamps of the second annular flange, the face of the second tab of each ring sector that is at the bottom in the radial direction of the turbine ring having two rest surfaces in contact respectively with the third and fourth holder elements secured to the second annular flange, the two thrust surfaces and the two rest surfaces extending in a common second plane. This alignment of the contact zones on a thrust plane serves to avoid any relative movement in the radial direction associated with the differences in coefficient of thermal expansion, and serves to conserve the same contact zones both when cold and when hot.

According to a third particular aspect of the turbine ring assembly of the invention, the first or second tab of each ring sector includes a recess situated between the two thrust surfaces, the recess receiving a centering element secured to the first or second annular flange. The centering element serves to guide and hold the ring sectors in radial position during expansions of the flanges of the ring support structure.

According to a fourth particular aspect of the turbine ring assembly of the invention, it further comprises a plurality of upstream plates mounted on the first flange, each upstream plate having a first holder element and a second holder element. The use of plates serves to make it easier to mount the ring sectors on the ring support structure.

Brief description of the drawings

The invention can be better understood by reading the following description given by way of non-limiting indication and with reference to the accompanying drawings, in which:

- Figure 1 is a first diagrammatic perspective view of an embodiment of a turbine ring assembly of the invention;

- Figure 2 is a second diagrammatic perspective view of the Figure turbine ring assembly;

- Figure 3 is a first exploded diagrammatic perspective view of the turbine ring assembly of Figures 1 and 2;

- Figure 4 is a second exploded diagrammatic perspective view of the turbine ring assembly of

Figures 1 and 2;

- Figure 5 is a diagrammatic perspective view showing how a ring sector is mounted on the ring support

structure of Figures	1 and 2;
	- Figure	6	is a	section view of	the	Figure	1	turbine
ring	assembly;
	- Figure	7	is a	section view of	the	Figure	6	turbine
ring	assembly	on	section plane VII shown	in Figure	• 6; and
	- Figure	8	is a	section view of	the	Figure	6	turbine
ring	assembly	on	section plane VIII	shown	l in Figure 8.

Detailed description of embodiments

Figures 1 and 2 show a high-pressure turbine ring assembly comprising a turbine ring 1 made of ceramic matrix composite (CMC) material and a metal ring support structure 3. The turbine ring 1 surrounds a set of rotary blades (not shown). The turbine ring 1 is made up of a plurality of ring sectors 10, with Figures 1 and 2 being views in radial section. Arrow Da shows the axial direction of the turbine ring 1, while arrow Dr shows the radial direction of the turbine ring 1.

As shown in Figure 3, each ring sector 10 presents a substantially K-shaped section in a plane defined by the axial and radial directions Da and Dr, said section having an annular base 12 having an inside face (inside in the radial direction Dr of the ring) that is covered in a layer 13 of abradable material defining the gas stream flow passage through the turbine. Substantially S-shaped upstream and downstream tabs 14 and 16 extend in the direction Dr from the outside face of the annular base 12 over its entire width and over upstream and downstream end portions 121 terms upstream reference to the and 122 of the annular base 12.

and downstream are used herein flow direction

The with through the turbine (arrow F in Figures

The ring support structure turbine casing 30, has an upstream annular radial flange

3, which is secured to a and a downstream annular radial flange 36 that extends in the radial direction Dr towards the center of the ring 1 and in the circumferential direction of the ring. In the presently-described example, the ring support structure 3 also has a plurality of upstream plates 33 each in the form of a ring segment, the upstream plates 33 being fastened on the upstream annular radial flange 32 .

The inside face 14b in the radial direction Dr of the turbine ring of the first tab 14 of each ring sector 10 has two rest surfaces 1415 and 1416 (Figures 3 and 8) that rest on respective portions of first and second holder elements, specifically pegs 40 and 41, that are secured to the upstream annular radial flange 32 (Figure 1), the holder elements being made of a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors.

In the presently-described example, the pegs 40 and

41 are interference	fits in the orifices 330 and 331 of
each upstream plate	33, using known metal fits such as
H6-P6 fits or other	force-fits enabling these elements to
be held when cold.	Since the upstream plates 33 are

fastened on the upstream annular radial flange 32, the pegs 40 and 41 are secured to the upstream annular radial flange .

Likewise, the inside face 16b in the radial direction Dr of the turbine ring of the second tab 16 of each ring sector 10 has two rest surfaces 1615 and 1616 (Figures 4 and 7) that rest on respective portions of third and fourth holder elements, specifically pegs 50 and 51 that are secured to the downstream annular radial flange 36 (Figure 2), the holder elements being made of a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors .

In the presently-described example, the pegs 50 and are interference fits in orifices 360 and 361 present in the downstream annular radial flange 36, using known metal fits such as H6-P6 fits or other force-fits that enable these elements to be held when cold.

The use of upstream plates 33 serves to facilitate mounting the ring sectors on the ring support structure.

The upstream annular radial flange 32 of the ring support structure 3 has a plurality of clamps 61 and 71 against its face 32a facing the upstream tabs 14 of the ring sectors 10, the clamps 61 and 71 belonging to respective eccentric clamping elements 60 and 70 and corresponding to portions of the clamps for thrusting against the ring sectors. Each eccentric clamping element 60, 70 comprises a threaded rod 62, 72 that is placed in an orifice 322, 323 present in the flange 32 and in an orifice 332, 333 present in each upstream plate 33. In this example, the clamps 61, 71 are in the form of shoes having flats 610, 710 and they are fastened in eccentric manner on the threaded rods 62, 72. The clamps 61, 71 present beside the face 32a facing the upstream tab 14 are held in determined positions by tightening respective nuts 63, 73 on the threaded rods 62, 72.

Thrust surfaces 1413 and 1414 present on the outside face 14a of the upstream tab 14 are in contact when cold with the respective clamps 61 and 71 present against the face 32a of the flange 32 facing the upstream tab 14 of each ring sector 10.

On the downstream side, the downstream annular radial flange 36 of the ring support structure 3 has a plurality of clamps 81 and 91 against its face 36a facing the downstream tabs 16 of the ring sectors 10, the clamps 81, 91 belonging to respective eccentric clamping elements 80 and 90 and corresponding to portions of the clamps for thrusting against the ring sectors. Each eccentric clamping element 80, 90 comprises a threaded rod 82, 92 that is placed in an orifice 362, 363 present in the flange 36. In this example, the clamps 81, 91 are in the form of shoes having flats 810, 910 and they are fastened in eccentric manner on the threaded rods 82, 92.

The clamps 81, 91 present beside the face 36a facing the downstream tab 16 is held in a determined position by tightening a nut 83, 93 on the threaded rod 82, 92.

Thrust surfaces 1613 and 1614 present on the outside face 16a of the downstream tab 16 are in contact when cold with the respective clamps 81 and 91 present against the face 36a of the flange 36 facing the downstream tab 16 of each ring sector 10.

By using eccentric clamping elements 60, 70, 80, and

90, it is possible to adjust the thrust forces when cold between the ring sectors and the ring support structure. The term cold is used in the present invention to mean the temperature at which the ring assembly is to be found when the turbine is not in operation, i.e. at ambient temperature, which may be about 25°C, for example. The term hot is used herein to mean the temperatures to which the ring assembly is subjected while the turbine is in operation, which temperatures may lie in the range 600°C to 900°C.

The eccentric clamping elements may have shapes other than those described above. The clamps of these elements may for example be constituted by cylindrical elements mounted eccentrically on the threaded rod.

Inter-sector sealing is provided by sealing tongues received in grooves that face one another in the facing edges of two adjacent ring sectors. A tongue 22a extends over almost the entire length of the annular base 12 in its middle portion. Another tongue 22b extends along the tab 14 and over a portion of the annular base 12. Another tongue 22c extends along the tab 16. At one end, each of the tongues 22b and 22c comes into abutment against the tongue 22a. By way of example, the tongues 22a, 22b, and 22c are made of metal and they are mounted with clearance when cold in their housings so as to provide the sealing function at the temperatures that are encountered in operation.

In conventional manner, ventilation orifices (not shown in Figures 1 to 4) formed in the flange 32 enable cooling air to be brought to the outside of the turbine ring 10.

There follows a description of a method of making a turbine ring assembly corresponding to the assembly shown in Figures 1 and 2.

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

In order to make the fiber preform, it is possible to use yarns made of ceramic fibers, e.g. SiC fiber yarns such as those sold by the Japanese supplier Nippon Carbon under the name Nicalon, or else carbon fiber yarns.

The fiber preform is advantageously made by threedimensional weaving or by multilayer weaving with zones of non-interlinking being arranged so as to enable the portions of the preforms that correspond to the tabs 14 and 16 of the sectors 10 to be folded out.

The weaving may be of the interlock type, as shown. Other three-dimensional or multilayer weaves may be used, such as for example multi-plain or multi-satin weaves. Reference may be made to Document WO 2006/136755.

After weaving, the blank may be shaped in order to obtain a ring sector preform that is consolidated and densified by a ceramic matrix, with densification being performed in particular by chemical vapor infiltration (CVI) as is well known.

A detailed example of fabricating ring sectors out of CMC is described in particular in Document

US 2012/0027572.

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

Making the turbine ring assembly continues by mounting ring sectors 10 on the ring support structure 3. As shown in Figure 5, the inside faces 16b of the downstream tabs 16 of each ring sector are placed on the pegs 50 and 51 present beside the face 36a of the downstream annular radial flange 36. The clamping elements 80 and 90 are then mounted so as to hold the downstream tabs 16 of each ring sector 10 against the flange 36. The upstream plates 33 and the pegs 40 and 41 interference-fitted therein are then assembled with the upstream annular radial flange 32, the threaded rods 62 and 72 of the eccentric clamping elements 60 and 70 being placed respectively in the orifices 322 and 332 and in the orifices 323 and 333 present in the flange 32 and in the plates 33. The upstream plates 33 are held against the flange 32 by tightening the nuts 63 and 73 on the threaded rods 62 and 72. Once the upstream plates 33 have been mounted in this way, the inside faces 14b of the downstream tabs 14 of each ring sector 10 rest on the pegs 40 and 41. Retention of the tabs 14 and 16 of each ring sector without clearance when cold between the flanges 32 and 36 of the ring support structure is adjusted by varying the positions of the clamps 61, 71, 81, and 91 of the eccentric clamping elements 60, 70, 80, and 90. This results in a turbine ring assembly as shown in Figures 1 and 2.

Preferably, the contact zones between the tabs of the ring sectors and both the thrust portions and the pegs secured to the annular flanges are in alignment in a common plane. More precisely, and as shown in Figure l_rthe thrust surfaces 1613 and 1614 and the rest surfaces 1615 and 1616 present on the downstream tabs 16 of each ring sector 10 lie in the same first thrust plane PA. Thus, all of the thrust points or zones of the downstream annular radial flange 36 constituted by the clamps 81 and 91, and also by the pegs 50 and 51, against the downstream tab 16 of each ring sector 10 are in alignment on the same thrust plane PA. This alignment of the contact zones on a thrust plane serves to avoid any relative movement in the radial direction associated with differences of coefficient of thermal expansion and serves to conserve the same contact zones both when cold and when hot.

Likewise, and as shown in Figure 8, the thrust surfaces 1413 and 1414 and the rest surfaces 1415 and 1416 present on the upstream tab 14 extend in the same second thrust plane PB. Thus, all of the thrust points or zones of the upstream annular radial flange 32 as constituted by the clamps 61 and 71 and also by the pegs 40 and 41 against the upstream tab 14 of each ring sector 10 are in alignment on the same thrust plane. This alignment of contact zones on a thrust plane serves to avoid any relative movement in the radial direction associated with differences of coefficients of thermal expansion and serves to conserve the same contact zones both when hot and when cold.

According to a particular characteristic, the downstream tab 16 of each ring sector 10 may also include a housing, specifically a cutout 164, that receives a centering element, specifically a peg 60, that is secured to the upstream annular radial flange 32 (Figures 3 and 8). Alternatively, a central cutout may be provided in the upstream tab 14 of each ring sector 10 and may cooperate with a centering element secured to the downstream annular radial flange. The centering element serves to guide and to hold the ring sectors in position radially during expansions of the flanges of the ring support structure.

Claims

1. A turbine ring assembly comprising a plurality of ring sectors (10) made of ceramic matrix composite material so as to form a turbine ring (1) and a ring support structure (3) including first and second annular flanges (32, 36), the ring support structure being made of a material having a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the ceramic matrix composite material of the ring sectors, each ring sector presenting a K-shape in a section plane defined by an axial direction (Da) and a radial direction (Dr) of the turbine ring, the K-shape having a portion forming an annular base (12) with a face on the inside in the radial direction (Dr) of the turbine ring defining the inside face of the turbine ring, and with a face on the outside from which there projects first and second S-shaped tabs (14, 16), the tabs of each ring sector being held between the two annular flanges (32, 36) of the ring support structure (3), the assembly being characterized:

in that the face (14b) of the first tab (14) of each ring sector (10) that is on the inside in the radial direction of the turbine ring rests against a portion of first and second holder elements secured to the first annular flange (32);

in that the face (16b) of the second tab (16) of each ring sector (10) that is on the inside in the radial direction of the turbine ring rests against a portion of third and fourth holder elements secured to the second annular flange (36);

in that the first annular flange (32) comprises a plurality of clamps (61, 71) on its face (32a) facing the first tab (14) of each ring sector (10), the clamps (61, 71) being distributed circumferentially on the first flange, the face (14a) of the first tab (14) of each ring sector (10) that is on the outside in the radial direction of the turbine ring being in contact with two clamps; and in that the second annular flange (36) comprises a plurality of clamps (81, 91) on its face (36a) facing the second tab (16) of each ring sector (10), the clamps (81, 91) being distributed circumferentially on the second flange, the face (16a) of the second tab (16) of each ring sector (10) that is on the outside in the radial direction of the turbine ring being in contact with two clamps .

2. An assembly according to claim 1, wherein the first and second holder elements are formed respectively by first and second pegs (40, 41) secured to the first annular flange (32) and in that the third and fourth holder elements are formed respectively by third and fourth pegs (50, 51) secured to the second annular flange (36) .

3. An assembly according to claim 1 or claim 2, wherein each clamp (61, 71, 81, 91) belongs to an adjustable eccentric clamping element (60, 70, 80, 90).

4. An assembly according to any one of claims 1 to 3, wherein the face (14a) of the first tab (14) of each ring sector (10) that is at the top in the radial direction of the turbine ring has two thrust surfaces (1413, 1414) in contact respectively with two clamps (61, 71) of the first annular flange (32), the face (14b) of the first tab (14) of each ring sector (10) that is at the bottom in the radial direction of the turbine ring has two rest surfaces (1415, 1416) in contact respectively with the first and second holder elements secured to the first annular flange (32), the two thrust surfaces and the two rest surfaces extending in a common first plane (PA), and wherein the face (16a) of the second tab (16) of each ring sector (10) that is at the top in the radial direction of the turbine ring has two thrust surfaces (1413, 1414) in contact respectively with two clamps (81, 91) of the second annular flange (36), the face (16b) of the second tab (16) of each ring sector (10) that is at the bottom in the radial direction of the turbine ring having two rest surfaces (1615, 1616) in contact respectively with the third and fourth holder elements secured to the second annular flange (36), the two thrust surfaces and the two rest surfaces extending in a common second plane (PB).

5. An assembly according to any one of claims 1 to 4, wherein the first tab (14) or the second tab (16) of each ring sector (10) includes a recess (164) situated between the two thrust surfaces (1613, 1614), the recess receiving a centering element (60) secured to the first annular flange (32) or to the second annular flange (36).

6. An assembly according to any one of claims 1 to 5, further comprising a plurality of upstream plates (33) mounted on the first flange (32), each upstream plate having a first holder element and a second holder element.