Turbine shroud assembly

Abstract

Turbine shroud assembly, comprising sections (10) made of CMC and forming the shroud (1), and a support structure member (3), each section having a base (12) which has a radially inner surface (12a) and a radially outer surface (12b), an upstream attachment lug (14) and a downstream attachment lug (16) extending in a projecting manner from the radially outer surface, the support structure member comprising a collar (31), an upstream radial flange (32) and a downstream radial flange (36) extending radially towards the shroud in a projecting manner from the collar, the lugs of each section of the shroud being held by the upstream radial flange and the downstream radial flange, the shroud (1) being held by axial pins (119, 120) which cooperate on the one hand with the upstream radial flange respectively via a first annular end plate and a second annular end plate (33, 34), and directly with the downstream radial flange, and which cooperate on the other hand with the upstream attachment lug and the downstream attachment lug respectively.

Description

Technical Field

[0001] The present invention relates to a turbine ring assembly which, on the one hand, comprises a plurality of ring segments made of a ceramic matrix composite material and, on the other hand, comprises a structural member for supporting the ring. Background Art

[0002] The application field of the present invention is in particular the field of aero gas turbine engines. However, the present invention can be applied to other turbines, such as industrial turbines.

[0003] In the case of an all-metal turbine ring assembly, it is necessary to cool all the components of the assembly, in particular the turbine ring that is subjected to the hottest gas flow.

[0004] Since the cooling air flow used is extracted from the main air flow of the engine, this cooling has a significant impact on the engine performance. In addition, the use of metal in the turbine ring limits the possibility of increasing the temperature at the turbine, but this would enable the improvement of the performance of the aero engine.

[0005] To solve these problems, it has been envisaged to manufacture the turbine ring segments from a ceramic matrix composite (CMC) material to avoid using metal materials.

[0006] The CMC material has good mechanical properties, which enables the CMC material to form structural elements. In addition, advantageously, the CMC material retains these properties at high temperatures. Therefore, the use of the CMC material can reduce the cooling air flow applied during operation, thereby improving the performance of the turbine.

[0007] In other words, the integration of the ring made of the CMC material (the ring has a very high resistance temperature) enables the reduction of the air flow extracted from the bottom of the chamber, which is necessary for pressurizing the chamber outside the flow path, thus improving the specific fuel consumption of the engine.

[0008] Although the CMC material has a lower density than ordinary metal materials, no expected mass improvement has been achieved due to the integration limitation of the components with which the rings cooperate.

[0009] Document FR 3076578 typically shows such a CMC material ring assembly associated with a metal ring support structural member.

[0010] The attached Figure 1 is a schematic cross-sectional view of a turbine ring assembly according to this prior art.

[0011] More specifically, the shown high-pressure turbine ring assembly comprises a turbine ring 1 made of a ceramic matrix composite (CMC) material and a metal structural member 3 for supporting the ring. The ring 1 surrounds a set of rotating blades (the rotating blades are not shown here). The ring 1 is composed of a plurality of ring segments 10 (only one ring segment is inFigure 1 is formed as visible. Arrow D A and D R respectively represent the axial direction and the radial direction of the turbine ring 1.

[0012] As Figure 1 shown, each ring segment 10 has a segment generally in the shape of an inverted Greek letter pi (π) along the plane defined by the axial direction D A and the radial direction D R The term "upstream" and "downstream" are used throughout this application with reference to the flow direction of the gas flow in the turbine, which is indicated by arrow F. This segment includes an annular base 12 and upstream radial attachment lugs 14 and downstream radial attachment lugs 16 respectively.

[0013] The annular base 12 includes an inner surface 12a and an outer surface 12b that face each other along the radial direction D R of the ring 1. The inner surface 12a of the annular base 12 is coated with a wear-resistant material layer 13 to define the flow path of the gas flow in the turbine. The terms "inner" and "outer" are used herein with reference to the radial direction D R of the turbine.

[0014] The structural member 3 for fixing the support ring 1 to the turbine housing includes a central shroud 31 that generally extends in the axial direction D A When the ring and the structural member are fixed together, the rotation axis of the structural member coincides with the rotation axis of the turbine ring 1. The structural member also includes a first annular radial clamp 32 and a second annular radial clamp 36 respectively. The first clamp 32 is positioned upstream of the second clamp 36.

[0015] The turbine ring assembly 1 also includes a first annular flange 33 and a second annular flange 34, which are removably fixed to the first annular radial clamp 32. These two annular flanges are arranged upstream of the turbine ring 1 with respect to the flow direction F of the gas flow in the turbine. The first flange 33 is arranged downstream of the second flange 34.

[0016] The first annular flange 33 has a first inner part 333 and a second outer part 334.

[0017] The second annular flange 34 has a first free end 341 and a second end 342 opposite to the first free end, and the second end contacts the central shroud 31. The second end 342 of the second annular flange 34 is also removably fixed to the ring support structure member 1, more specifically, removably fixed to the first annular radial clamp 32.

[0018] When the ring assembly 1 is in place, a first part 333 of the first annular flange 33 bears against the upstream radial attachment lugs 14 of each of the ring segments 10 forming the turbine ring 1, and a second part 334 of the first annular flange 34 bears against at least a part of the first annular radial clamp 32.

[0019] The two flanges 33 and 34 are removably fixed to the upstream annular radial clamp 32 by fixing screws 60 and nuts 61, the screws 60 passing through orifices provided respectively in the two flanges and in the clamp 32. Similarly, only one screw and only one nut are visible in Figure 1 it.

[0020] The second annular flange 34 is intended to withstand the force by transmitting the force of the high-pressure distributor (DHP) on the ring assembly 1 to the mechanically more robust housing line, that is to say to the line of the ring support structure (as Figure 1 shown by the arrow E in it). Since the first part 333 of the first upstream flange has a reduced section and is thus more flexible, the residual force passing through the first upstream flange 33 is reduced, which makes it possible to apply a minimum force on the CMC ring 1.

[0021] In the axial direction D A the downstream annular radial clamp 36 of the ring support structure 3 is spaced apart from the first upstream annular flange 33 by a distance corresponding to the spacing of the upstream radial attachment lugs 14 and the downstream radial attachment lugs 16, in order to hold the upstream radial attachment lugs and the downstream radial attachment lugs between the downstream annular radial clamp 36 and the first upstream flange 33.

[0022] In order to hold the ring segments 10 and thus the turbine ring 1 in place relative to the ring support structure 3, for each ring segment 10 the ring assembly comprises a first pin 119 cooperating with the upstream attachment lug 14 and the first annular flange 33, and a second pin 120 cooperating with the downstream attachment lug 16 and the second annular radial clamp 36. Of course, orifices (not visible) are provided for receiving these pins.

[0023] The ring support structure 3 also comprises a radial pin 38 which makes it possible to hold the ring in a defined low radial position, that is to say towards the flow path, in a certain way. There is indeed a clearance between the axial pins 119 and 120 and the holes in the ring 1 in order to compensate for the differential expansion which occurs on heating between the metal and the CMC elements. The radial pin 38 cooperates with an orifice 380 formed in the central shroud 31 of the ring support structure 3 along the radial direction D R formed.

[0024] Document 2017 / 103411 describes a turbine ring assembly as defined in the preamble of claim 1.

[0025] According to this prior art, relative to the direction of flow of the gas flow in the turbine:

[0026] - The shroud includes a first upstream portion and a second downstream portion. The first upstream portion extends radially above the first attachment lug. The second downstream portion extends in an extension of the first upstream portion and extends radially above the second attachment lug. The first upstream portion has a straight cylindrical shape. The second downstream portion has a frustoconical shape. The second downstream portion extends from one end of the first upstream portion towards the axis of the turbine ring while having a substantially constant thickness;

[0027] - The upstream radial clamp extends from the upstream portion to bear against the upstream attachment lug, while the downstream radial clamp extends from the downstream portion to come into contact with the downstream attachment lug.

[0028] Due to these features, a part of the material of the shroud is transferred to a reduced radius. Thus, the volume and mass of the shroud are reduced while obtaining an axially symmetric component. In addition, due to the presence of this converging region in a part of the housing, such a structural member also makes it possible to reduce the flexibility of the housing, thereby reducing the displacement of the components.

[0029] Furthermore, the use of screws and pins to hold the ring is limited, which reduces the mass of the component.

[0030] In this context, the present invention aims to further improve such a turbine ring assembly, particularly in terms of the mass of the turbine ring assembly. Summary of the Invention

[0031] To this end, the present invention particularly relates to a turbine ring assembly, which includes a plurality of ring segments made of a ceramic matrix composite material forming the turbine ring, and a ring support structure. Each ring segment has a base along a cutting plane defined by the axial direction and the radial direction of the turbine ring. The axial direction corresponds to the flow direction of the air flow in the turbine. The base has a radially inner surface and a radially outer surface in the radial direction of the turbine ring. The radially inner surface defines the inner surface of the turbine ring. An upstream attachment lug and a downstream attachment lug project from the radially outer surface. The ring support structure includes a shroud extending around the turbine ring. An upstream radial clamp and a downstream radial clamp project radially from the shroud towards the turbine ring. The upstream attachment lug and the downstream attachment lug of each ring segment are held by the upstream radial clamp and the downstream radial clamp. The shroud includes a first upstream portion and a second downstream portion with respect to the flow direction of the air flow in the turbine. The first upstream portion extends radially above the first attachment lug. The second downstream portion extends in an extension of the first upstream portion and extends radially above the second attachment lug. The first upstream portion has a straight cylindrical shape. The second downstream portion has a frustoconical shape. The second downstream portion extends from one end of the first upstream portion towards the axis of the turbine ring while having a substantially constant thickness. The upstream radial clamp extends from the upstream portion to directly or indirectly bear against the upstream attachment lug, and the downstream radial clamp extends from the downstream portion to come into contact with the downstream attachment lug.

[0032] According to the present invention, the ring is held relative to the radial clamp by an axial pin. On the one hand, the axial pin cooperates with the upstream radial clamp through a first annular flange and a second annular flange respectively, and directly cooperates with the downstream radial clamp. On the other hand, the axial pin cooperates with the upstream attachment lug and the downstream attachment lug.

[0033] Due to these features, the ring is radially wedged, so there is no longer a need to use radial pins as in the above-mentioned prior art to ensure a definite block. Not using such pins helps to reduce the mass of the component. In addition, according to the above-mentioned prior art, the significant thickness of the housing is justified particularly due to the fact that it is necessary to ensure a sufficient guiding length for the pins. Since these thicknesses are no longer required now, the thickness can be corrected downwards, and particularly can reach half of the thickness according to the prior art.

[0034] According to a specific embodiment of the present invention:

[0035] - The shroud has a substantially constant thickness between the two clamps;

[0036] - The upstream portion and the downstream portion form an angle between 30° and 80°, preferably between 30° and 70°.

[0037] - The ring is also held in a compressed manner between the radial clamps.

[0038] According to some additional features of the present invention:

[0039] - The first annular flange and the second annular flange have substantially the same thickness in the axial direction along the radial extent of the first annular flange and the second annular flange;

[0040] - The ring is at least partially formed by a three-dimensional braid of ceramic fibers, the three-dimensional braid including warp yarns and weft yarns, characterized in that the ratio of warp / weft yarns within the ring is variable;

[0041] - The ratio within the annular base is lower than the ratio within the attachment lug.

[0042] Finally, the present invention also relates to a turbine including a turbine ring assembly according to any one of the above-described detailed features. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features and advantages of the present invention will become apparent from the following description with reference to the drawings, which illustrate possible embodiments in an indicative but non-limiting manner.

[0044] In these drawings:

[0045] As shown above, Figure 1 is a schematic cross-sectional view of a turbine ring assembly according to the above prior art;

[0046] Figure 2 is a view similar to that of the assembly according to the present invention Figure 1 ;

[0047] Figure 3 is Figure 2 a three-dimensional cross-sectional view of the assembly of DETAILED DESCRIPTION

[0048] In the appended Figure 2 and Figure 3 of an exemplary embodiment of the present invention, the turbine ring assembly shown is structurally similar to the assembly described above with reference to the prior art Figure 1 ;

[0049] In the following description, reference numerals identical to those already used with reference to Figure 1 correspond to the same or similar components. Under these conditions and unless otherwise specified, only the specific elements of the present invention will be substantially described below.

[0050] ​​In the same manner as in the aforementioned prior art, the component according to the invention comprises a structural member 3 that supports the ring 1, the structural member including a central shroud 31 from which a first clamp 32 and a second clamp 36 project radially, and the first attachment lugs 14 and the second attachment lugs 16 of each ring segment 10 made of a ceramic matrix composite material are held by the first clamp and the second clamp.

[0051] According to the invention, the shroud is characterized in that it comprises a first upstream portion 310 and a second downstream portion 320 that are coaxial, the first upstream portion 310 having a straight cylindrical shape, while the second downstream portion has a converging wall. Advantageously, the transition region 330 between these two portions 310 and 320 is curved, that is to say, it has no protruding corners.

[0052] Advantageously and as Figure 2 and Figure 3 shown, the second downstream portion has the shape of a frustum of a cone.

[0053] Still according to the invention, the first radial clamp 32 is fixed to the first upstream portion 310, while the second radial clamp 36 is fixed to the downstream region of the second downstream portion 320. In other words, the second radial clamp extends in the region of the portion 320 that is farthest from the upstream portion 310.

[0054] In the case shown here, the second clamp extends to the boundary of the second portion 320 that is connected to the downstream extension portion 340, which is coaxial with the first portion 310.

[0055] Due to this structural member, the material of the housing can be at least partially transferred to a smaller radius, which makes it possible to significantly reduce the volume of the housing and thus its mass. In addition, an axially symmetric component is thus obtained, which makes the manufacture of the axially symmetric component easier.

[0056] Furthermore, due to the specific taper of the housing in the second downstream portion, this modification also makes it possible to reduce the flexibility of the turbine ring assembly and thus reduce the displacement of the turbine ring assembly.

[0057] Advantageously, the angle α formed by the generatrices of the upstream portion 310 and the downstream portion 320 is between 30° and 80°, preferably between 30° and 70°, which makes it possible to obtain a good compromise between the reduction in total mass and the stiffness.

[0058] To further reduce the total mass of the component according to the invention, any of the solutions described below can be used.

[0059] Thus, it is possible to use what is arranged in Figure 2 and Figure 3A flange 34 upstream of the structural member, the thickness of which is thinned to improve quality. This component enables the axial force from the high-pressure diffuser to be transferred to the outer casing to release the ring 1. Thinning such a flange may exert pressure on the ring 1. However, this optimization of the flange geometry enables an increase in the flexibility of the flange and thus a reduction in the axially transmitted force. Therefore, in addition to the weight improvement, the pressure on the ring 1 is no greater than the pressure during installation according to the above-mentioned prior art.

[0060] According to the invention, the thickness of the flange 34 is such that the two flanges 33 and 34 have substantially the same thickness in the axial direction along the radial extent of the flange. Thus, in this case, the thickness of the flange 34 can be reduced by half compared to the thickness of the flange implemented according to the prior art.

[0061] As in the prior art, the ring 1 is axially held relative to the axial clamps 32 and 36 by axial pins 119 and 120. The axial pins 119 and 120 cooperate with the first radial clamp 32 via the first annular flange 33 and the second annular flange 34 respectively on the one hand, and directly cooperate with the second radial clamp 36. On the other hand, the axial pins 119 and 120 cooperate with the first attachment lug 14 and the second attachment lug 16.

[0062] In the radial direction, due to the reduction in the thickness of the flange 34 and the flexibility provided by the frustoconical shape of the second part 320 of the central shroud 31, the ring 1 is held in compression between the radial clamps 32 and 36. Thus, this enables the attachment lugs 14 and 16 of each ring segment 10 to be clamped, thereby holding each ring segment radially. Therefore, the radial pins denoted by the reference numeral 38 in the above Figure 1 are no longer required. Thus, the total mass of the assembly according to the invention is further reduced.

[0063] In a known manner, the ring 1 can be obtained at least in part by three-dimensional weaving of ceramic fibers, this weaving comprising warp and weft yarns, in particular as described in document FR 2942844. To reduce the mass of the assembly according to the invention, this weaving can be carried out by varying the warp / weft ratio for manufacturing the ring. More particularly, a lower ratio can be used within the annular base 12 relative to the attachment lugs 14 and 16.

[0064] In this way, in the central part formed by the annular base 12, the thickness of the weaving is reduced while the thickness of the attachment lugs 14 and 16 remains unchanged. Thus, for the same number of weaving layers, a thinner and thus lighter central part is obtained, but with lugs that are still equally thick and strong.

[0065] By way of indication only, the thickness reduction can be from about 0.5 mm to 5 mm.

[0066] Although this does not form part of the specific features of the present invention, it should be noted that the components shown in the appended Figure 2 and Figure 3 include a cooling device with the reference numeral 4.

[0067] More specifically, the outer surface 12b of the ring 1 and the attachment lugs 14 and 16 form a cavity outside the flow path, in other words, outside the hot fluid flow path F.

[0068] Due to the high-temperature air on the flow path side, the wall 12 is subject to a significant temperature gradient. In addition, the high pressure present in the hot air flow path increases the risk of hot air leakage, especially at the joints between the ring segments 10. Therefore, injecting cooling air into the cavity outside the flow path enables the wall 12 of the ring to be cooled, reduces the thermal gradient in the wall, and also increases the pressure in the cavity outside the flow path, thereby limiting the risk of hot air leakage flowing out of the flow path.

[0069] The above-mentioned cooling device is attached to the flanges 33 and 34 and includes a head pointing near the wall 12 of the ring, and the head is provided with an opening (not shown) to form a cooling channel.

Claims

1. A turbine ring assembly, comprising a plurality of ring segments (10) made of a ceramic matrix composite material forming a turbine ring (1), and a ring support structure (3), each ring segment (10) having a base (12) along a cutting plane defined by the axial direction (D A ) and the radial direction (D R ) of the turbine ring (1), the axial direction corresponding to the flow direction (F) of the air flow in the turbine, the base having a radially inner surface (12a) and a radially outer surface (12b) in the radial direction (D R ) of the turbine ring (1), the radially inner surface defining the inner surface of the turbine ring (1), an upstream attachment lug (14) and a downstream attachment lug (16) protruding from the radially outer surface, the ring support structure (3) comprising a shroud (31) extending around the turbine ring (1), an upstream radial clamp (32) and a downstream radial clamp (36) protruding radially from the shroud towards the turbine ring (1), the upstream attachment lug (14) and the downstream attachment lug (16) of each ring segment (10) being held by the upstream radial clamp and the downstream radial clamp, the shroud (31) comprising, with respect to the flow direction (F) of the air flow in the turbine: A first upstream portion (310) and a second downstream portion (320), the first upstream portion extending radially above the upstream attachment lug (14), the second downstream portion extending in an extension of the first upstream portion (310) and extending radially above the downstream attachment lug (16), the first upstream portion (310) having a straight cylindrical shape, the second downstream portion (320) having a frustoconical shape, the second downstream portion extending from one end of the first upstream portion (310) towards the axis of the turbine ring (1) while having a substantially constant thickness, The upstream radial clamp (32) extends from the first upstream portion (310) to directly or indirectly bear against the upstream attachment lug (14), while the downstream radial clamp (36) extends from the second downstream portion (320) to come into contact with the downstream attachment lug (16), characterized in that the downstream radial clamp (36) extends in the region of the second downstream portion (320) furthest from the first upstream portion (310), the turbine ring (1) being held relative to the upstream radial clamp (32) and the downstream radial clamp (36) by axial pins (119, 120), the axial pins cooperating with the upstream radial clamp (32) respectively through a first annular flange (33) and a second annular flange (34) on the one hand and directly cooperating with the downstream radial clamp (36) on the one hand, and the axial pins cooperating with the upstream attachment lug (14) and the downstream attachment lug (16) on the other hand, the first upstream portion (310) and the second downstream portion (320) forming an angle between 30° and 80°.

2. The turbine ring assembly according to claim 1, wherein The shroud (31) has a substantially constant thickness between the upstream radial clamp (32) and the downstream radial clamp (36).

3. The turbine ring assembly according to claim 1 or 2, characterized in that, The first upstream portion (310) and the second downstream portion (320) form an angle between 30° and 70°.

4. The turbine ring assembly according to claim 1 or 2, characterized in that, The turbine ring (1) is also held in a compressed manner between the upstream radial clamp (32) and the downstream radial clamp (36).

5. The turbine ring assembly according to claim 1 or 2, characterized in that, The first annular flange (33) and the second annular flange (34) have substantially the same thickness along the radial extent of the first annular flange and the second annular flange in the axial direction.

6. The turbine ring assembly according to claim 1 or 2, wherein, The turbine ring (1) is at least partially formed by a three-dimensional braid of ceramic fibers, the three-dimensional braid including warp yarns and weft yarns, characterized in that the ratio of the warp yarns / the weft yarns in the turbine ring (1) is variable.

7. The turbine ring assembly according to claim 6, wherein, The ratio in the annular base (12) is lower than the ratio in the upstream attachment lug (14) and the downstream attachment lug (16).

8. A turbine comprising a turbine ring assembly according to any one of claims 1 to 7.

Images