Turbine ring assembly with improved axial pins

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 pin (50) and at least one passage (140) passing axially through an attachment tab (14, 16) over an axial length (Ll) of the passage (140). At least one pin (50) comprises a planar bearing surface (506) facing an inner surface (142) of the passage (140) through which the pin (50) passes, the bearing surface (506) facing the inner surface (142) extending axially over a length (L2) less than the axial length (Ll) of the passage (140).

Description

[0001] Description

[0002] Title of Invention: Improved Axial Pin Turbine Ring Assembly

[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, particularly the turbine ring, which is subject to the hottest flows. This cooling has a significant impact on engine performance since the cooling flow used is taken from the main engine flow. In addition, the use of metal for the turbine ring limits the possibilities of increasing the temperature at the turbine level, which would otherwise 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, GB 2 480 766, EP 1 350 927, US 2014 / 0271145, US 2012 / 082540 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 does not support shrink-fit assemblies (usually used for metallic rings) and its thermal expansion is lower than that of a metallic material.

[0014] The radial support area between the pins and the top of the ring lugs crossed by the pins is one of the sensitive areas of the technology, with high mechanical stresses. Significant partial damage is observed on a test bench. This phenomenon could be amplified during engine operation due to an inevitable tilting of the part. Since the most marked wear areas are close to the edges of the ring holes, such a tilting would lead to even more significant effects.

[0015] Statement of the invention

[0016] 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.

[0017] More particularly, the solution of the present invention aims to reduce the risk of wear of the ears receiving the pins, in particular at the edges of the ear piercings.

[0018] 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 and a radial direction, and a ring support structure held by a turbine casing, each ring sector comprising a base from which an upstream attachment lug and a downstream attachment 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 attachment lug and the downstream attachment lug of each ring sector are held, and the ring assembly comprising, for each ring sector, at least one pin and at least one passage axially passing through a downstream or upstream attachment lug over an axial length of the passage,said at least one pin cooperating with said at least one passage and one of the upstream or downstream radial flanges of the ring support structure.,

[0019] The turbine ring assembly according to the invention is remarkable in particular in that the passage extends axially between an upstream end and a downstream end and is delimited by an internal surface extending over the axial length of the passage, and, according to a section plane comprising the axial direction, said at least one pin comprises an external, or peripheral, surface which has a flat bearing portion facing the internal surface of said passage crossed by the pin, said bearing portion of the peripheral surface of the pin facing the internal surface of the passage crossed by the pin extending axially over a length less than said axial length of the passage.

[0020] The solution of the present invention thus makes it possible to reduce the risk of wear of the passages crossed by a pin thanks to a specific geometry of the axial pins used. The geometry of the pin according to the invention thus makes it possible to ensure that the support between the pin and the passage made in the CMC ring is not made on at least one edge of the passage but rather in the middle of the material of the CMC ring. In other words, the invention makes it possible to ensure that the pin is not in support with the edge of the hole forming the passage in the tab of the ring, but as much as possible with the middle of the hole in the axial direction.

[0021] The bearing portion of the peripheral surface of the pin preferably comprises an axial length of between 50% and 90% of the axial length of the passage.

[0022] Preferably, the internal surface of the passage is flat.

[0023] Also preferably, the peripheral surface of the pin bears against the internal surface.

[0024] According to a first aspect of the turbine ring assembly, said at least one pin may comprise two opposite axial ends, the pin comprising a chamfer on at least one axial end of the pin.

[0025] Preferably, the chamfer is truncated.

[0026] The chamfer made at one or both axial ends makes it easier to insert the pin into the corresponding passages or holes.

[0027] According to a second aspect of the turbine ring assembly, a chamfer may extend between an axial end of the pin and said bearing portion of the peripheral surface of the pin, a portion of the chamfer being arranged opposite the internal surface of the passage crossed by the pin.

[0028] The use of a chamfer extending from the axial end of the pin to the pin bearing surface makes it possible to simplify the production of the pin while combining an effect of simplifying the insertion of the pin into a passage and preventing damage to the edges of the passage.

[0029] According to a third aspect of the turbine ring assembly, said at least one pin may comprise at least one groove extending over the perimeter of the peripheral surface of the pin in a plane orthogonal to the axial direction, the groove(s) comprising a thickness in the axial direction and being positioned opposite one end of said passage through which the pin passes.

[0030] The groove provided opposite the edge of a passage allows axial pins to be easily manufactured, significantly reducing the risk of damage to the passage edges. Preferably, the pin comprises axial symmetry about an axis parallel to the axial direction, a first radius in a cutting plane perpendicular to the axial direction and intersecting the bearing surface of the pin, a second radius in a cutting plane perpendicular to the axial direction and intersecting the groove, and a third radius in a cutting plane perpendicular to the axial direction and intersecting the axial end of the pin located opposite the ring, the first radius being larger than the second radius, which is itself larger than the third radius.

[0031] According to a fourth aspect of the turbine ring assembly, the groove may comprise a semi-circular shape in a sectional plane comprising the axial direction and the radial direction.

[0032] In one embodiment, the groove may comprise a trapezoidal shape in a sectional plane comprising the axial direction and the radial direction.

[0033] In another embodiment, the pin may comprise axial symmetry along an axis parallel to the axial direction, a first radius in a cutting plane perpendicular to the axial direction and intersecting the bearing portion of the peripheral surface of the pin, a second radius in a cutting plane perpendicular to the axial direction and intersecting the groove, and a third radius in a cutting plane perpendicular to the axial direction and intersecting the axial end of the pin arranged opposite the ring, the first radius being larger than the second radius, which is itself larger than the third radius.

[0034] According to a fifth aspect of the turbine ring assembly, the ring assembly may comprise, for each ring sector, at least one downstream pin cooperating with the downstream attachment lug and the downstream radial flange of the support structure, and at least one upstream pin cooperating with the upstream attachment lug and the upstream radial flange.

[0035] In a variant, the turbine ring assembly may comprise, for each ring sector, at least two pins, each pin passing transversely through the upstream attachment lug and the downstream attachment lug of the ring sector and the ring support to hold the ring sector and the ring support secured to each other. The invention also relates to a turbomachine comprising an assembly as defined above.

[0036] Brief description of the drawings

[0037] [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 the invention.

[0038] [Fig. 2] Figure 2 is a zoom of Figure 1 on the downstream pin 50.

[0039] [Fig. 3] Figure 3 represents a schematic view of a pawn according to a second embodiment of the invention.

[0040] [Fig. 4] Figure 4 represents a schematic view of a pawn according to a third embodiment of the invention.

[0041] [Fig. 5] Figure 5 represents a schematic view of a pawn according to a fourth embodiment of the invention.

[0042] [Fig. 6] Figure 6 represents a schematic view of a pawn according to a fifth embodiment of the invention.

[0043] [Fig. 7] Figure 7 represents a schematic view of a pawn according to a sixth embodiment of the invention.

[0044] Description of the embodiments

[0045] Figure 1 schematically represents a turbine ring assembly 2 according to the invention. Figure 1 is a sectional view along a plane comprising the radial direction DR and the axial direction D A .

[0046] This assembly 2 includes 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.

[0047] Subsequently, throughout the text, the terms "upstream" and "downstream" are used with reference to the direction of flow of the gas flow F through the blades indicated by an arrow. 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 A indicates the axial direction of the turbine ring while the arrow DR indicates the radial direction of the turbine ring.

[0048] Each angular ring sector 10 has a section substantially in the shape of an inverted Pi (or ÎT) 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 coating 13 also acting as a thermal and environmental barrier.

[0049] Two hooking lugs, a downstream hooking lug 14 and an upstream hooking lug 16, extend radially from the external face 12b of the base 12 opposite the internal face 12a. These hooking lugs 14 and 16 extend over the entire width of each ring sector 10 (in the circumferential direction).

[0050] 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 520 of the upstream radial flange 62.

[0051] 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.

[0052] 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.

[0053] Figure 2 shows a zoom of Figure 1 on the downstream pin 50.

[0054] As shown in Figures 1 and 2, the downstream pin 50 passes through a passage 140 of the downstream attachment lug 14 of the ring sector 10. The passage 140 extends axially between an upstream end 144 and a downstream end 146 and is delimited radially by an internal surface 142 against which the pin bears and which extends over an axial length L1.

[0055] Each downstream pin 50 comprises an inner end 502 and an outer end 504. The inner end 502 is inside the ring 4, between the downstream attachment lug 14 and the upstream attachment lug 16, and the outer end 504 is outside the ring 4, inserted into a radial flange of the ring support structure 6. The outer end 504 comprises a first chamfer 504a allowing it to be inserted into a housing 642 provided in the attachment portion 640 of the downstream radial flange 64.

[0056] The inner end 502 comprises a second rounded chamfer 502a extending from the inner end 502 to a bearing surface 506 extending parallel to the axial direction D x The junction between the second chamfer 502a and the bearing surface 506 of the downstream pin 50 is arranged in the passage 140 of the downstream attachment tab 14, opposite the internal surface 142 of the passage 140.

[0057] Thus, the bearing surface 506 of the downstream pin 50 which is in abutment against the internal surface 142 of the passage 140 of the downstream attachment lug 14 comprises an axial length L2 less than the axial length L1 of the internal surface 142 of the passage 140.

[0058] In Figure 3 is illustrated a downstream pin 50 according to a second embodiment.

[0059] The downstream pin 50 of the second embodiment differs from the first embodiment of Figures 1 and 2 in several points.

[0060] First of all, the second chamfer 502a does not extend to the inside of the passage 140. The downstream pin 50, on the other hand, comprises a groove 508 made over the entire periphery of the pin and arranged opposite the downstream end 146 of the passage 140. This groove 508 thus makes it possible to ensure that the axial length L2 of the bearing surface 506 of the pin 50 is less than the axial length L1 of the internal surface 142 of the passage 140.

[0061] In Figure 4 is illustrated a downstream pin 50 according to a third embodiment.

[0062] The downstream pin 50 of the third embodiment differs from the second embodiment of FIG. 3 in that the groove 508 comprises a trapezoid-shaped profile in a section plane comprising the axial direction D A and the radial direction DR while in figure 3 the groove 508 comprises a rectangular profile in the same cutting plane.

[0063] The radially inner side of the trapezoid of the groove 508 is smaller than the radially outer side of the groove, thus further reducing the length of the bearing surface 506 of the downstream pin 50.

[0064] In this third embodiment, the pin 50 comprises axial symmetry along an axis parallel to the axial direction D A , a first ray R1 in a cutting plane perpendicular to the axial direction D A and intersecting the bearing surface 506 of the pin 50, a second ray in a cutting plane perpendicular to the axial direction D A and intersecting the groove 508, and a third radius in a cutting plane perpendicular to the axial direction D A and intersecting the internal axial end 502 of the pin 50, the first radius R1 being greater than the second radius R2, which is itself greater than the third radius R3.

[0065] In Figure 5 is illustrated a downstream pin 50 according to a fourth embodiment.

[0066] The downstream pin 50 of the fourth embodiment differs from the second embodiment of FIG. 3 in that the chamfer 502a is even slightly smaller, but above all in that it comprises a second groove 509 made over the entire periphery of the pin and arranged opposite the upstream end 144 of the passage 140.

[0067] The downstream pin of Figure 5 is presented in a configuration where the pin passes not only through the attachment portion 640 of the downstream radial flange 64 and the attachment tab 14 of the ring 4 but also through an additional flange 680 which could be an additional radial flange of the ring support structure 6.

[0068] In Figure 6 is illustrated a downstream pin 50 according to a fifth embodiment. The downstream pin 50 of the fifth embodiment differs from the fourth embodiment illustrated in Figure 5 in that the grooves 508 and 509 comprise a semicircular-shaped profile in a section plane comprising the axial direction D A and the radial direction DR while in figure 5 the grooves 508 and 509 comprise a rectangular profile in the same cutting plane.

[0069] In Figure 7 is illustrated a downstream pin 50 according to a sixth embodiment.

[0070] The downstream pin 50 of the sixth embodiment differs from the second embodiment of FIG. 3 in that the inner end 502 is smaller in the radial direction DR than the outer end 504, and in that the inner end 502 does not include a chamfer, but instead, a ramp 502c between the inner end 502 and the bearing surface 506 of the pin.

[0071] The downstream pin 50 of the sixth embodiment illustrated in FIG. 7 further comprises a hollowed-out portion 510 located between the bearing surface 506 of the downstream pin 50 and the downstream end 504. The hollowed-out portion 510 thus forms a second ramp between the bearing surface 506 of the pin 50, the bearing surface 506 is thus at a distance from the upstream end 144 and the downstream end 146 of the passage 140.

[0072] In another embodiment of the invention, the upstream pins 40 may have the same conformation as the downstream pins 50.

[0073] The present invention thus provides a turbine ring assembly making it possible to reduce the risk of wear of the ears of the attachment tabs of the ring receiving the pins, in particular at the edges of the ear holes.

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) and a radial direction (DR), 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 the ring assembly (2) comprising, for each ring sector (10), at least one pin (50) and at least one passage (140) axially passing through a downstream hooking lug (14) or upstream hooking lug (16) over an axial length (L1) of the passage (140), said at least one pin (50) cooperating with said at least one passage (140) and one of the upstream or downstream radial flanges (62, 64) of the ring support structure (6),characterized in that the passage (140) extends axially between an upstream end (144) and a downstream end (146) and is delimited by an internal surface (142) extending over the axial length (L1) of the passage (140), and, according to a section plane comprising the axial direction (D, A ), said at least one pin (50) comprises a peripheral surface which has a flat bearing portion (506) facing the internal surface (142) of said passage (140) crossed by the pin (50), said bearing portion (506) of the peripheral surface of the pin (50) facing the internal surface (142) of the passage (140) crossed by the pin (50) extending axially over an axial length (L2) less than said axial length (L1) of the passage (140).

2. Turbine ring assembly (2) according to claim 1, in which the bearing portion (506) of the peripheral surface of the pin (50) comprises an axial length (L2) of between 50% and 90% of the axial length (L1) of the passage (140).

3. Turbine ring assembly (2) according to one of claims 1 or 2, wherein said at least one pin (50) comprises two opposite axial ends (502, 504), the pin (50) comprising a chamfer (502a), preferably frustoconical, on at least one axial end (502) of the pin (50).

4. Turbine ring assembly (2) according to claim 3, in which a chamfer (502a) extends between an axial end (502) of the pin (50) and said bearing portion (506) of the peripheral surface of the pin (50), a portion of the chamfer (502a) being arranged opposite the internal surface (142) of the passage (140) crossed by the pin (50).

5. Turbine ring assembly (2) according to one of claims 1 to 4, wherein said at least one pin (50) comprises at least one groove (508, 509) extending over the perimeter of the peripheral surface of the pin (50) in a plane orthogonal to the axial direction (D A ), the groove(s) (508, 509) comprising a thickness in the axial direction (D A ) and being positioned opposite one end (144, 146) of said passage (140) which the pin (50) crosses.

6. A turbine ring assembly (2) according to claim 5, wherein the groove (508, 509) comprises a semicircular shape in a section plane comprising the axial direction (DA) and the radial direction (DR).

7. A turbine ring assembly (2) according to claim 5, wherein the groove (508, 509) comprises a trapezoidal shape in a sectional plane comprising the axial direction (D A) and the radial direction (DR).

8. Turbine ring assembly (2) according to one of claims 5 to 7, in which the pin (50) comprises axial symmetry along an axis parallel to the axial direction (D A ), a first ray (RI) in a cutting plane perpendicular to the axial direction (D A ) and intersecting the support portion (506) of the peripheral surface of the pin (50), a second radius (R2) in a cutting plane perpendicular to the axial direction (D A ) and intersecting the groove (508), and a third radius (R3) in a cutting plane perpendicular to the axial direction (D A ) and cutting the axial end (502) of the pin arranged opposite the ring, the first radius (RI) being larger than the second radius (R2), which is itself larger than the third radius (R3).

9. Turbine ring assembly according to one of claims 1 to 8, comprising, for each ring sector (10), at least one downstream pin (50) cooperating with the downstream attachment lug (14) and the downstream radial flange (64) of the support structure (6), and at least one upstream pin (40) cooperating with the upstream attachment lug (16) and the upstream radial flange (62).

10. Turbine ring assembly according to one of claims 1 to 8, comprising, for each ring sector (10), at least two pins, each pin passing transversely through the upstream attachment lug (16) and the downstream attachment lug (14) of the ring sector (10) and the ring support (6) to hold the ring sector (10) and the ring support (6) integral with each other.

11. A turbine ring assembly according to one of claims 1 to 10, wherein the inner surface (142) of the passage (140) is planar.

12. Turbomachine comprising an assembly (2) according to any one of claims 1 to 11.

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