Turbine ring assembly with a sealing plate

Abstract

The invention relates to a turbine ring assembly (2) provided with a sectorized CMC turbine ring (4) and with a ring support structure (6), each sector (10) of the ring (4) comprising a base (12) from which an upstream attachment tab (16) and a downstream attachment tab (14), which are spaced axially, extend radially outwards, the support structure (6) comprising an upstream radial flange (62) and a downstream radial flange (64), between which the attachment tabs (14, 16) of each sector (10) are held, and the assembly (2) comprising, for each sector (10), at least one first pin (50) passing through the downstream attachment tab (14) and the downstream radial flange (64), and at least one second pin (40) passing through the upstream attachment tab (16) and the upstream radial flange (62). The ring assembly (2) further comprises an annular insert plate (66) mounted between the downstream attachment tab (14) of the ring sector (10) and the downstream radial flange (64) of the ring support structure (6).

Description

[0001] Description

[0002] Title of the invention: Turbine ring assembly with a sealing sheet

[0003] Technical Field

[0004] A turbine ring assembly for a turbomachine is provided wherein the assembly comprises a plurality of angular ring sectors of ceramic matrix composite material placed end to end to form a turbine ring.

[0005] The field of application of the invention is in particular that of gas turbine aeronautical engines. The invention is however applicable to other turbomachines, for example industrial turbines.

[0006] Prior art

[0007] In the case of all-metal turbine ring assemblies, it is necessary to cool all the elements of the assembly and in particular the turbine ring which is subjected to the hottest flows. This cooling has a significant impact on the engine performance since the cooling flow used is taken from the primary flow of the engine. In addition, the use of metallic material for the turbine ring limits the possibilities of increasing the temperature at the turbine level due to the mechanical limitations specific to this type of material, which would nevertheless improve the performance of aeronautical engines.

[0008] In an attempt to resolve these problems, consideration was given to making turbine ring sectors from ceramic matrix composite (CMC) material in order to avoid the need to use a metallic material.

[0009] CMC materials have good mechanical properties making them suitable for forming structural elements and advantageously retain these properties at high temperatures. The use of CMC materials has advantageously made it possible to reduce the cooling flow required during operation and therefore to increase the performance of turbomachines. In addition, the use of CMC materials advantageously makes it possible to reduce the mass of turbomachines and to reduce the effect of hot expansion encountered with metal parts. Documents FR 2 540 939 and FR 2 955 898 are also known, which disclose turbine ring assemblies.

[0010] The ring sectors comprise an annular base whose inner face defines the inner face of the turbine ring and an outer face from which two legs extend radially, the ends of which are held between the two flanges of a metal ring support structure.

[0011] The integration of a CMC ring includes radial support of the part partly ensured by one or more axial pins. In the known document FR 3 086 327, there are four pins, two upstream and two downstream.

[0012] The use of CMC ring sectors thus makes it possible to significantly reduce the ventilation required to cool the turbine ring, and therefore increase efficiency. They also allow for weight savings because they are lighter than the metal alloys traditionally used.

[0013] However, since CMC has a different mechanical behavior from a metallic material, its integration and the way of positioning it within the turbine had to be rethought. Indeed, CMC can be damaged by shrink-fit assemblies (usually used for metallic rings) and its thermal expansion is lower than that of a metallic material.

[0014] There is a need to improve existing turbine ring assemblies and their mounting, and in particular existing turbine ring assemblies using CMC material in order to reduce the intensity of mechanical stresses to which the CMC ring sectors are subjected during turbine operation.

[0015] Axially, the ring is clamped between two metal tabs. The downstream tab is directly connected to the casing, describing a one-piece ring, ensuring increased sealing compared to a solution with a sectored spacer. The upstream tab includes a sectored flange screwed onto the casing.

[0016] These two metal tabs include a lip to better control the ring / casing seal. For each ring sector, this lip is straight so that there is always linear contact, and therefore a good seal, even if the ring tilts. Another flange is dedicated to taking up the force from the high pressure distributor (DHP force). It allows the DHP force to be taken up and transferred directly to the casing, without passing the forces through the CMC ring.

[0017] To ensure axial contact when hot between the ring and the straight lips of the upstream and downstream legs, pre-tightening is carried out during assembly. This pre-tightening makes it possible to compensate for the differential axial expansion between the CMC ring and the metal parts in contact. Thus, when hot, axial contact is maintained and the seal between the vein cavity and the non-vein cavity is ensured.

[0018] In addition to ensuring the part is held in place, the straight lips, or straight supports, provide a seal between the cavity above the ring and the vein. It is this seal that ensures the presence of greater pressure in the ring cavity and helps prevent the potential reintroduction of vein gases at the combustion chamber outlet (too hot for metal parts) into the cavities outside the veins. Maintaining this seal at a sufficient level throughout the entire lifespan of the technology is therefore essential.

[0019] Tests were carried out to ensure that these contacts age correctly and that they remain watertight during operating cycles.

[0020] The first results showed an increase in leakage at the end, which is not acceptable with regard to good maintenance of overpressure in the cavities outside the vein compared to the main vein.

[0021] After analysis, the formation of a metallic deposit on the CMC ring was observed. It appears that this wear is due to differential thermal expansion at the ends of the support, the CMC ring expanding less than the non-sectorized metal parts at the interface, at the same temperature.

[0022] Statement of the invention

[0023] The main aim of the present invention is therefore to propose a turbine ring assembly which does not have the aforementioned drawbacks while having a reduced mass and further reducing the intensity of the mechanical stresses to which the CMC ring sectors are subjected during operation of the turbine. More particularly, the solution of the present invention aims to limit wear at the level of the contacts between the CMC ring and the metal parts.

[0024] This aim is achieved by means of a turbine ring assembly comprising a plurality of ring sectors made of ceramic matrix composite material forming a turbine ring, defining an axial direction, a radial direction and a circumferential direction, and a ring support structure held by a turbine casing, each ring sector comprising a base from which an upstream hooking lug and a downstream hooking lug extend radially outwards axially spaced from one another, the ring support structure comprising an upstream radial flange and a downstream radial flange between which the upstream hooking lug and the downstream hooking lug of each ring sector are held, and, to radially hold the ring sector in position with the ring support structure, the ring assembly comprising, for each ring sector,at least one first pin passing through the downstream attachment lug and the downstream radial flange and at least one second pin passing through the upstream attachment lug and the upstream radial flange.,

[0025] The turbine ring assembly according to the invention is remarkable in particular in that it further comprises an annular metal sealing sheet mounted between the downstream attachment lug of the ring sector and the downstream radial flange of the ring support structure.

[0026] The straight lips used in the prior art are replaced by an intermediate sheet disposed between the downstream attachment lug and the downstream radial flange. This sealing sheet limits friction between the downstream radial flange and the downstream attachment lug and thus limits wear at the contacts. This sheet improves the tribology of the contact by smoothing the forces along the entire length of the part.

[0027] This therefore improves the operating performance of the turbine ring and increases its service life.

[0028] More explicitly, the sealing sheet allows the force to be distributed over the entire tangential length of the ring sector, even though the casing transmits more forces in certain areas, due to a stiffness varying tangentially depending on the integration. According to a first aspect of the turbine ring assembly, the sealing sheet can form a radial crown extending over at least part of the radial length of the downstream attachment lug, the sealing sheet being crossed by said at least one first pin to be held radially with the ring sector and the ring support structure.

[0029] Said at least one orifice provided in the sealing sheet to be crossed by said at least one pin serving for the radial and tangential maintenance of the turbine ring with the ring support structure makes it possible to easily integrate the sheet without requiring an adjustment of the reference geometry such as the addition of an additional part generating a very significant axial size.

[0030] Maintaining the sealing sheet is necessary to prevent ingestion into the primary vein during clearance openings during operation (unforeseen event generating non-nominal part thermal gradients for example).

[0031] According to a second aspect of the turbine ring assembly, the sealing sheet may comprise a thickness of between 0.1 mm and 1 mm, the thickness being measured in the axial direction.

[0032] The thinness of the sealing sheet allows for contact that generates less wear. In fact, due to its flexibility, it will be able to deform in the areas where the contact forces are highest, thus relieving the CMC material parts in the same locations.

[0033] According to a third aspect of the turbine ring assembly, the thickness of the sealing sheet may vary along the circumferential direction of the ring formed by the sealing sheet.

[0034] The variation in the thickness of the sheet metal in the circumferential direction makes it possible to distribute the forces uniformly over the ring sector in CMC material, with for example a thickness twice as great near the inter-sectors (significant forces) than at the middle of the ring.

[0035] According to a fourth aspect of the turbine ring assembly, the sealing sheet may comprise a radial length of between 3 mm and 10 mm.

[0036] According to a fifth aspect of the turbine ring assembly proposing an alternative embodiment of the sealing sheet, the sealing sheet can form an axial ring extending in the axial direction, with a thickness measured in the radial direction and a length in the axial direction greater than the thickness, the downstream radial flange comprising a first groove extending in the circumferential direction, and the downstream attachment lug comprising a second groove extending in the circumferential direction opposite the first groove, the first groove and the second groove each having a depth measured in the axial direction less than half the axial length of the sealing sheet.

[0037] This embodiment makes it possible to reduce the value of the hooping between the flanges of the ring support and the ring attachment lugs. This results in an order of magnitude of a few hundredths of a millimeter to 0.2 mm on an initial value of 0.2 to 0.3 mm. Contact stresses are reduced as well as the risks of damage accordingly.

[0038] According to a sixth aspect of the turbine ring assembly, the sealing sheet may be made from a metallic material selected from A600®, Hastelloy X®, HA188®, and HS25®.

[0039] A600® has an expansion coefficient intermediate between that of Wasploy® metal parts and CMC. Hastelloy X® and HA188® allow for the production of thin parts, in the order of 0.1 mm in particular, with good resistance to high temperatures. HS25 has good behavior in contact with CMC (very little chemical interaction).

[0040] Furthermore, in the event of thermal creep between the parts, the casing rubs against this metal sealing sheet, this contact not generating significant wear. The differential creep between the turbine ring made of CMC material and this sealing sheet is lower than if there was direct contact between the part made of CMC material and the casing. This is even more true if a material with intermediate thermal expansion is used for the sealing sheet between the metal casing and the CMC ring.

[0041] According to a seventh aspect of the turbine ring assembly, the sealing sheet may comprise a plurality of sheet sectors together forming a ring coaxial with the turbine ring, the sealing sheet sectors comprising a length of between 50 mm and 150 mm in the circumferential direction of the turbine ring.

[0042] According to an eighth aspect of the turbine ring assembly, the first pin and the second pin are two transverse pins, each transverse pin passing through the upstream hooking lug and the downstream hooking lug of the ring sector and the ring support to hold the ring sector and the ring support integral with each other.

[0043] The turbine ring assembly may further comprise another annular metal sealing sheet mounted between the upstream attachment lug of the ring sector and the upstream radial flange of the ring support structure.

[0044] The invention also relates to a turbomachine comprising an assembly as defined above.

[0045] Brief description of the drawings

[0046] [Fig. 1] Figure 1 is a schematic sectional view along a plane including the axial direction and the radial direction of a turbine ring assembly according to a first embodiment of the invention.

[0047] [Fig. 2] Figure 2 shows a perspective view of a portion of the turbine ring assembly of Figure 1.

[0048] [Fig. 3] Figure 3 shows a partial perspective view of a portion of the turbine ring assembly of Figure 1.

[0049] [Fig. 4] Figure 4 shows a perspective view of a portion of a turbine ring assembly according to a second embodiment of the invention.

[0050] [Fig. 5] Figure 5 shows a schematic sectional view along a plane including the axial direction and the radial direction of the turbine ring assembly of Figure 4.

[0051] Description of the embodiments

[0052] Figure 1 schematically represents a turbine ring assembly 2 according to a first embodiment of the invention. Figure 1 is a sectional view along a plane comprising the radial direction D R and the axial direction D . Figures 2 and 3 show two perspective views of a portion of the turbine ring assembly of Figure 1 .

[0053] The turbine ring assembly 2 shown in Figures 1 to 3 comprises in particular a turbine ring 4 made of ceramic matrix composite (CMC) material centered on a longitudinal axis XX, a metal ring support structure 6 fixed to a turbine casing not shown for greater readability. The turbine ring 4 surrounds a set of turbine blades not shown.

[0054] Subsequently, throughout the text, the terms "upstream" and "downstream" are used in reference to the direction of flow of the gas stream F through the blades indicated by an arrow.

[0055] Furthermore, the turbine ring 4 is formed from a plurality of angular ring sectors 10 which are placed end to end in the circumferential direction to form a ring. In Figure 1, the arrow D indicates the axial direction of the turbine ring while the arrow D R indicates the radial direction of the turbine ring.

[0056] Each angular ring sector 10 has a section substantially in the shape of an inverted Pi (or ii) with a base 12 provided with an internal face 12a which defines an angular portion of the internal face of the turbine ring 4 and which is typically provided with a layer of abradable or abrasive coating 13, also acting as a thermal and environmental barrier.

[0057] Two axially spaced attachment lugs, a downstream attachment lug 14 and an upstream attachment lug 16, extend radially from the outer face 12b of the base 12 opposite the inner face 12a. These attachment lugs 14 and 16 extend over the entire width of each ring sector 10 (in the circumferential direction).

[0058] The ring support structure 6 comprises a ferrule 60 extending around the axis XX, as well as an upstream radial flange 62 and a downstream radial flange 64 extending radially inward from the ferrule 60. The downstream radial flange 64 comprises an attachment portion 640 projecting radially from the ferrule 60, and the upstream radial flange 62 comprises an attachment portion 620 projecting radially from the ring 60, as well as a first upstream flange 20 and a second upstream flange 22 fixed to the attachment portion 620 projecting radially from the upstream radial flange 62 using bolts 300 and nuts 302. The first upstream flange 20 is arranged upstream of the second upstream flange 22. The bolts 300 axially pass through the first upstream flange 20, the second upstream flange 22 and the attachment portion 620 of the upstream radial flange 62.

[0059] The upstream radial flange 62 and the downstream radial flange 64 thus form two attachment flanges for the ring 4 arranged axially between the downstream attachment lug 14 and the upstream attachment lug 16 of the ring sectors 10.

[0060] The turbine ring assembly 2 further comprises upstream pins 40 and downstream pins 50. The upstream pins 40 pass through the second upstream flange 22 of the upstream radial flange 62 as well as the upstream lug 16 of a ring sector 10. The downstream pins 50 pass at least partially through the downstream radial flange 64, and more particularly the radially projecting attachment portion 640, as well as the downstream attachment lug 14.

[0061] The turbine ring assembly according to the invention further comprises an annular metal sealing sheet 66 mounted between the downstream attachment lug 14 of the ring sector 10 and the attachment portion 640 of the downstream radial flange 64 of the ring support structure 6.

[0062] The sealing sheet 66 makes it possible to distribute the force over the entire tangential length of the ring sector 10, even though the casing transmits more forces in certain zones, due to a stiffness varying tangentially according to the integration.

[0063] The sealing sheet 66 forms a radial crown, that is to say forming a crown having a length in the radial direction D R greater than its thickness measured in the axial direction D. The radial crown formed by the sealing sheet 66 extends, in the radial direction, over at least part of the radial length of the downstream attachment lug 14.

[0064] The sealing sheet 66 comprises a plurality of sheet sectors together forming the radial crown, this radial crown being coaxial with the turbine ring 4. The sealing sheet sectors comprise a length of between 50 mm and 150 mm in the circumferential direction D.c of turbine ring 4.

[0065] In a variant, the sealing sheet 66 may be formed from a ring in a single piece. The sealing sheet 66 further comprises axial orifices each crossed by a downstream pin 50 to ensure the radial retention of the sealing sheet 66 with the ring sector 10 and the ring support structure 6.

[0066] The sealing sheet 66 comprises a thickness, in the axial direction D A , between 0.1 mm and 1 mm. This fineness allows for contact that generates less wear.

[0067] In some embodiments, the axial thickness of the sealing sheet 66 may vary along a circumferential direction of the crown formed by the sealing sheet, the circumferential direction being orthogonal to the radial direction D R and to the axial direction D A and describing a circle around the X axis.

[0068] The sealing sheet has a length in the radial direction DR of between 3 mm and 10 mm.

[0069] The sealing sheet is made from a metallic material chosen from A600®, Hastelloy X®, HA188®, and HS25®.

[0070] A600® has an expansion coefficient intermediate between that of Wasploy® metal parts and CMC. Hastelloy X® and HA188® allow for the production of thin parts, in the order of 0.1 mm in particular, with good resistance to high temperatures. HS25 has good behavior in contact with CMC (very little chemical interaction).

[0071] In Figure 4 is shown schematically a perspective view of a portion of a turbine ring assembly according to a second embodiment of the invention.

[0072] Figure 5 schematically illustrates a sectional view along a plane comprising the radial direction DR and the axial direction D. Aof ring assembly 2 of figure 4.

[0073] In this second embodiment illustrated in Figures 4 and 5, the sealing sheet 660 forms an axial ring extending in the axial direction D A , with a thickness measured in the radial direction D and a length measured in the axial direction D A , the axial length being greater than the radial thickness.

[0074] In the second embodiment, the downstream radial flange 64 comprises a first groove 642 hollowed out in the attachment portion 640 and extending in the circumferential direction D c , and the downstream hooking lug 14 comprises a second groove 140 extending in the circumferential direction D c opposite the first groove 642, the first groove and the second groove each having a depth measured in the axial direction D A less than half the axial length of the sealing sheet 660.

[0075] The present invention thus provides a turbine ring assembly having a reduced mass and further reducing the intensity of the mechanical stresses to which the CMC ring sectors are subjected during operation of the turbine.

Claims

Claims

1. Turbine ring assembly (2) comprising a plurality of ring sectors (10) made of ceramic matrix composite material forming a turbine ring (4), defining an axial direction (D A ), a radial direction (D R ) and a circumferential direction (D c), and a ring support structure (6) held by a turbine casing, each ring sector (10) comprising a base (12) from which an upstream hooking lug (16) and a downstream hooking lug (14) extend radially outwards axially spaced from each other, the ring support structure (6) comprising an upstream radial flange (62) and a downstream radial flange (64) between which the upstream hooking lug (16) and the downstream hooking lug (14) of each ring sector (10) are held, and, to radially hold the ring sector (10) in position with the ring support structure (6), the ring assembly (2) comprising, for each ring sector (10), at least a first pin (50) passing through the downstream hooking lug (14) and the downstream radial flange (64) and at least one second ... at least a second pin (40) passing through the upstream attachment lug (16) and the upstream radial flange (62),characterized in that it further comprises an annular metal sealing sheet (66, 660) mounted between the downstream attachment lug (14) of the ring sector (10) and the downstream radial flange (64) of the ring support structure (6), and another annular metal sealing sheet mounted between the upstream attachment lug (16) of the ring sector (10) and the upstream radial flange (62) of the ring support structure (6).,

2. Turbine ring assembly (2) according to claim 1, in which the sealing sheet (66) forms a radial crown extending over at least part of the radial length of the downstream attachment lug (14), the sealing sheet (66) being crossed by said at least one first pin (50) to be held radially with the ring sector (10) and the ring support structure (6).

3. Turbine ring assembly (2) according to claim 2, wherein the sealing sheet (66) comprises a thickness of between 0.1 mm and 1 mm, the thickness being measured in the axial direction (DA).

4. Turbine ring assembly (2) according to claim 3, wherein the thickness of the sealing sheet (66) varies along the circumferential direction (DC) of the crown formed by the sealing sheet (66).

5. Turbine ring assembly (2) according to one of claims 2 to 4, in which the sealing sheet (66) comprises a radial length of between 3 mm and 10 mm.

6. Turbine ring assembly (2) according to claim 1, in which the sealing sheet (660) forms an axial ring extending in the axial direction, with a thickness measured in the radial direction (D R) and a length in the axial direction (D) greater than the thickness, the downstream radial flange (64) comprising a first groove extending in the circumferential direction (D c ), and the downstream hooking lug (14) comprising a second groove extending in the circumferential direction (D c ) opposite the first groove, the first groove and the second groove each having a depth measured in the axial direction (D A ) less than half the axial length of the sealing sheet.

7. A turbine ring assembly according to one of claims 1 to 6, wherein the sealing sheet (66, 660) is made from a metallic material selected from A600®, Hastelloy X®, HA188®, and HS25®.

8. A turbine ring assembly (2) according to one of claims 1 to 7, wherein the sealing sheet (66, 660) comprises a plurality of sealing sheet sectors together forming a ring coaxial with the turbine ring (4), the sheet sectors comprising a length of between 50 mm and 150 mm in the circumferential direction (DC) of the turbine ring (4).

9. Turbine ring assembly according to one of claims 1 to 8, in which the first pin and the second pin are two transverse pins, each transverse pin passing through the upstream attachment lug (16) and the downstream attachment lug (14) of the ring sector (10) and the ring support (6) to keep the ring sector (10) and the ring support (6) secured to each other.

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

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