TURBINE RING ASSEMBLY MOUNTED ON A CARRIER

Description

Technical Field

[0001] 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.

[0002] 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. Prior art

[0003] 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.

[0004] 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.

[0005] CMC materials have good mechanical properties making them suitable for use in 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.

[0006] Documents WO 2015 / 191186, EP 3 118 417, WO 2015 / 191174, US 2006 / 292001, FR 2 540 939, GB 2 480 766, EP 1 350 927 are also known.

[0007] US 2014 / 0271145, US 2012 / 082540 and FR 2 955 898 which disclose turbine ring assemblies.

[0008] 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.

[0009] The use of CMC ring sectors thus makes it possible to significantly reduce the ventilation required to cool the turbine ring. 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.

[0010] In addition, the use of CMC ring sectors increases the number of parts required for its integration into the turbine casing, which increases the cost and weight of the assembly and requires complex assembly operations (shrinking of bushings, assembly of pins, etc.). Statement of the invention

[0011] 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.

[0012] This object is achieved by means of a turbine ring assembly extending about an axis, the assembly comprising a plurality of ring sectors made of ceramic matrix composite material forming a turbine ring and a ring support structure held by a turbine casing. Each ring sector comprises a base from which an upstream hooking lug and a downstream hooking lug extending radially outwardly axially spaced from each other.

[0013] The turbine ring assembly according to the invention is remarkable in particular in that it further comprises a spacer mechanically connected to the ring support and comprising a first radial flange bearing against the upstream attachment lugs of the ring sectors, and, for each ring sector, at least two transverse pins and a radial spring, each transverse pin passing through the upstream attachment lug and the downstream attachment lug of the ring sector and the ring support to keep the ring sector and the ring support secured to each other, and the radial spring being kept bearing against the ring sector on the one hand and against the ring support on the other hand, the ring support further comprising a second radial flange bearing against the downstream attachment lugs of the ring sectors,the upstream hooking lug and the downstream hooking lug of each ring sector being arranged axially between the first radial flange and the second radial flange.,

[0014] The architecture of the turbine ring assembly according to the invention thus makes it possible to provide radial and axial support for each ring sector made of CMC material not using the support techniques for metal rings and made in such a way as to control its position and prevent it from starting to vibrate, on the one hand, while allowing the ring sector, and by extension the ring, to deform freely under the effects of temperature increases and pressure variations, and this in particular thanks to a reduced number of metal parts at the interface.

[0015] In this architecture, the radial retention of a ring made of CMC material is ensured, on the one hand, by said at least two pins passing through each ring sector and the ring support via axial holes provided for this purpose, and, on the other hand, via the metal spring placed between two pins and being in radial support between the ring sector and the ring support.

[0016] The spring allows in particular to keep the ring sectors arranged in the same radial position.

[0017] The axial retention of a ring made of CMC material is ensured, on the one hand, by securing the ring support to the spacer, for example via at least one assembly formed by a screw and a nut, fixing the ring support and the spacer together outside the casing, and, on the other hand, by the plane contact between the upstream attachment lug of the ring and the spacer and by the plane contact between the ring support and the downstream attachment lug of the ring.

[0018] Furthermore, this architectural configuration of the turbine ring assembly provides a solution without bolted connection between the turbine ring and the ring support structure and the casing, the connection being made by means of the transverse pins, which makes it possible to reduce the total mass of the assembly significantly. In addition, the elimination of bolted connections also makes it possible to arrange the parts of the ring assembly differently, which also allows a weight saving by reducing the number of elements constituting the turbine ring assembly.

[0019] In addition, the elimination of radial pins reduces the machining operations of the parts of the ring support structure. This results in a saving of parts, and therefore a reduction in the weight and cost of the assembly.

[0020] Said first radial flange comprises a first portion and a second portion radially inside the first portion, the second portion comprising a first tab and a second tab axially distant from each other and both secured to the first portion, the first tab being axially upstream of the second tab, and the second tab bearing against the upstream attachment tab.

[0021] The first radial flange of the spacer thus makes it possible to minimize the tangential stress in the metal parts ensuring the maintenance of the ring, on the one hand, and to compensate for the high manufacturing dispersion of the CMC ring sectors, in particular the axial length of the rings.

[0022] In addition, making the spacer in a single piece significantly reduces the number of parts needed to hold the ring.

[0023] Furthermore, manufacturing tolerances are less severe, the spacer making it possible to compensate for the gaps between the ring sectors, which a 360° flange cannot do.

[0024] According to a second aspect of the turbine ring assembly, the downstream leg of said first radial flange may comprise a first end which is integral with the first portion of the first radial flange and a second end which is free and opposite the first end, the downstream leg further comprising radial slots regularly spaced angularly and each extending from the second end to a circular orifice, the number of radial slots being at most equal to the number of ring sectors.

[0025] The circular orifices into which the slots open make it possible to reduce the stress concentration in the area. In one embodiment, the number of slots may be equal to the number of ring sectors. In this way, contact between the spacer and each ring sector of the assembly is ensured regardless of the manufacturing dispersion of the CMC ring sectors. In another embodiment, the ring sectors may be paired two by two or three by three in order to create pairs of two or three rings having substantially identical axial lengths. The pairs of ring sectors are then mounted side by side on the motor to form the ring.

[0026] In this way the number of slots required on the downstream leg of the first radial flange of the spacer can be divided by two or three. This reduction in the number of slots makes it possible to further increase the robustness of the ventilation of the device by improving the sealing between the non-vein sector and the vein sector, in particular the sealing of the cavity located at the level of the radially upper part of the ring.

[0027] According to a third aspect of the turbine ring assembly, the spacer may include a crown disposed around the turbine ring, and the ring support may include a ferrule disposed radially between the turbine ring and the crown of the spacer.

[0028] According to a fourth aspect of the turbine ring assembly, the ring of the spacer may include injection ports and the shroud of the ring support includes complementary injection ports radially offset from the injection ports. In other words, no complementary injection port of the ring support is radially aligned with an injection port of the spacer.

[0029] The injection ports and the complementary injection ports supply cold air at high pressure, generally air taken from the outlet of the high-pressure compressor, to pressurize the cavities located between the ring and the spacer or between the ring and the ring support. In other words, this air injection makes it possible to pressurize the non-vein sector and thus improve the seal between the non-vein sector and the vein sector.

[0030] According to a fifth aspect of the turbine ring assembly, the assembly may further comprise a C-ring seal extending between the spacer crown and the ring carrier shroud, the C-ring seal being coaxial with the spacer crown and the ring carrier shroud.

[0031] The C-ring seal placed between the spacer and the ring holder helps minimize any leakage between these two parts and improves the robustness of the ring cooling device.

[0032] According to a sixth aspect of the turbine ring assembly, the ring support structure may further comprise a first radial support flange and a second radial support flange axially spaced from the first radial support flange, each transverse pin passing through the first radial support flange and the second radial support flange.

[0033] Radially coupling the turbine ring sectors to the ring support via transverse pins avoids the use of more cumbersome and heavier bolted connections and simplifies the mechanical configuration of the ring assembly.

[0034] According to a seventh aspect of the turbine ring assembly, the radial spring may comprise a metal plate having at least one crown in a first direction parallel to the axial direction.

[0035] The metal plate forming the radial spring may be corrugated or domed, with the bump extending radially to exert a force in the radial direction of the turbine ring.

[0036] According to an eighth aspect of the turbine ring assembly, the radial spring further comprises a tab extending projecting from the top of the crown in a second direction orthogonal to the first direction and extending along the crown in a third direction orthogonal to the first and second directions for a length less than the length of the metal plate in the third direction, the tab being disposed between the first and second radial support flanges to form an axial stop for the spring.

[0037] The spring tab thus prevents the spring from moving axially.

[0038] According to a ninth aspect of the turbine ring assembly, the assembly may further comprise an L-shaped sealing tab disposed at each junction between two adjacent ring sectors, each sealing tab comprising a large axially extending portion and a small radially extending portion, the small portion being integral with the large portion at an upstream end of the large portion.

[0039] The tongue extending in the circumferential direction between two adjacent ring sectors over the entire axial length of the ring sectors, this forms a seal ensuring the seal between the vein sector and the non-vein sector. In addition, the L-shape of the tongue prevents any impact between the tongue and the second radial flange.

[0040] According to a tenth aspect of the turbine ring assembly, the assembly may further comprise a thermal protection ring mounted radially within the second radial flange, the second radial flange of the ring support further comprising relief holes axially passing through said second radial flange of the ring support.

[0041] The relief holes and the thermal protection ring ensure a seal between the non-vein sector and the vein sector, particularly in the cavities located downstream of the ring sectors. The thermal protection ring may be an annular metal sheet segmented at a single point on its circumference to better adapt to the radial dimensions.

[0042] The invention also relates to a turbomachine comprising an assembly as defined above. Brief description of the drawings

[0043] [ Fig. 1 ] There figure 1is a schematic sectional view along a plane comprising the axial direction and the radial direction of a turbine ring assembly according to the invention. Fig. 2 ] There figure 2 represents a schematic sectional and perspective view of the spacer of the turbine assembly of the figure 1 . [ Fig. 3 ] There figure 3 represents a schematic perspective view of the radial spring of the turbine assembly of the figure 1 . [ Fig. 4 ] There figure 4 represents a sectional view of the ring assembly at a radial spring along a sectional plane including the axial direction and the radial direction. Fig. 5 ] There Figure 5 represents a sectional view of the ring assembly at a ring sector along a sectional plane comprising the radial direction and orthogonal to the axial direction. Description of the embodiments

[0044] There figure 1schematically represents a turbine ring assembly 2 according to the invention. The figure 1 is a sectional view along a plane including the radial direction and the axial direction.

[0045] This assembly 2 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 of which only an attachment portion 32 is shown on the figure 1 for readability. Turbine ring 4 surrounds a set of turbine blades not shown.

[0046] 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.

[0047] 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. On the figure 1 , the arrow DA 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 π) 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] In addition to the turbine ring 4 and the ring support structure 6 disposed radially outside the turbine ring 4, the ring assembly 2 further comprises a spacer 20 attached to the ring support structure 6 using a bolt 300 and a nut 302.

[0051] The spacer 20 comprises a crown 202 extending around the axis XX and having a downstream end 204 and an upstream end 206. The spacer 20 further comprises a first radial attachment flange 208 extending radially outward from the downstream end 204 of the spacer 20.

[0052] The ring support structure 6 includes a ferrule 60 extending about the axis XX and includes a second attachment flange 62 extending radially outwardly from the ferrule 60.

[0053] The second radial attachment flange 62 of the shroud 60 of the ring support structure 6, the attachment portion 32 of the turbine casing and the first radial attachment flange 208 of the spacer 20 are fixed together using the bolt 300 which axially passes through the three elements and the nut 302.

[0054] The ring support structure 6 further comprises a first radial attachment flange 64 for the ring 4 and a second radial attachment flange 66 for the ring 4, each extending inwards in the radial direction DR, i.e. towards the turbine ring 4.

[0055] The first radial attachment flange 64 is placed downstream of the second radial attachment flange 66. The first radial attachment flange 64 and the second radial attachment flange 66 are arranged axially between the downstream attachment lug 14 and the upstream attachment lug 16 of the ring sectors 10.

[0056] The turbine ring assembly 2 further comprises transverse pins 40, each transverse pin 40 being formed in a single piece and passing axially, in the direction of the gas flow F, the upstream tab 16 of a ring sector 10, the second radial attachment flange 66 of the ring support structure 6, the first radial attachment flange 64 of the ring support structure 6, and the downstream attachment tab 14.

[0057] Each transverse pin 40 comprises a downstream end 402, an upstream end 404, the upstream end comprising an axial orifice 406 to facilitate the removal of the pin 40.

[0058] The spacer 20 further comprises an upstream radial flange 210 extending radially inward from the upstream end 206 of the spacer 20. The upstream radial flange 210 comprises, in the radial direction DR, a first end 2101 secured to the upstream end 206 of the spacer 20, a second end 2102 free and opposite the first end 2101, a first portion 2103 and a second portion 2104, the first portion 2103 extending radially between the first end 2101 and the second portion 2104, and the second portion 2104 extending radially between the first portion 2103 and the second end 2102.

[0059] The second portion 2104 of the upstream radial flange 210 of the spacer 20 comprises an upstream tab 2105 and a downstream tab 2106. The upstream tab 2105 and the downstream tab 2106 of the second portion 2104 of the upstream radial flange 210 form two rings spaced apart from each other in the axial direction DA. Furthermore, the downstream tab 2106 of the upstream radial flange 210 bears against the upstream attachment tab 16 of the ring sectors 10.

[0060] The upstream attachment lug 16 of the ring sectors 10 is thus axially arranged, in the direction of flow F, between the downstream lug 2106 of the upstream radial flange 210 of the spacer 20 and the second radial attachment flange 66 of the ring support structure 6.

[0061] Furthermore, the upstream tab 2105 of the second portion 2104 of the upstream radial flange 210 comprises a radial groove 2107 on its radially inner end inside which a seal 2108 is inserted.

[0062] The spacer 20 may be a part of revolution (i.e. 360°) or may be made by assembling a plurality of spacer sectors placed end to end. The same applies to the ring support structure which may be made of a part of revolution or by assembling flange sectors.

[0063] The ring support structure 6 further comprises a downstream radial flange 68 arranged axially downstream of the first attachment flange 64 and downstream of the downstream attachment tab 14 of the ring sectors 10. The downstream attachment tab 14 of the ring sectors 10 is thus arranged axially, in the flow direction F, between the first radial attachment flange 64 and the downstream radial flange 68 of the ring support structure 6. The downstream radial flange 68 bears against the downstream attachment tab 16 of the ring sectors 10.

[0064] The ring sectors 10 are thus held axially in support between the downstream tab 2106 of the upstream radial flange 210 of the spacer 20 and the downstream radial flange 68 of the ring support structure 6.

[0065] The crown 202 of the spacer 20 further comprises injection orifices 220 radially passing through the crown 202 and the ferrule 60 of the ring support structure 6 further comprises complementary injection orifices 600 radially passing through the ferrule 60. The injection orifices 200 and the complementary injection orifices 600 are not radially aligned. They may be arranged in a staggered manner relative to each other. The injection orifices 200 and the complementary injection orifices 600 make it possible to convey cooling air taken from the high-pressure compressor into the cavities located between the ring support structure 6 and the turbine ring 4 in particular.

[0066] The downstream radial flange 68 of the ring support structure 6 further comprises relief holes 680 for conveying cooling air into the cavity located downstream of the downstream radial flange 68.

[0067] The ring assembly 2 further comprises a C-shaped metal annular seal 50 disposed radially between the spacer 20 and the ring support structure 6 to improve sealing.

[0068] The ring assembly 2 also comprises a thermal protection ring 52 made of metal arranged radially between the downstream radial flange 68 of the ring support structure 6 and the vein 45 inside which the gas flow F flows.

[0069] Furthermore, as illustrated in the figure 2which presents a schematic perspective sectional view of the spacer 20, the downstream tab 2106 of the upstream radial flange 210 of the spacer 20 further comprises a plurality of radial slots 222 regularly angularly spaced in the circumferential direction. The radial slots 222 are open and extend radially from the second end 2102 of the upstream radial flange 210 to a circular orifice 224 making it possible to reduce the accumulation of stresses. Depending on the embodiment, the number of radial slots 222 is equal to the number of ring sectors 10 forming the turbine ring 4, or is equal to the number of ring sectors 10 divided by two or three.

[0070] On the figure 3a radial spring 70 is schematically shown in perspective. The radial spring 70 comprises a corrugated metal plate 71, the corrugation being arranged in a first direction tangent to the circumferential direction of the turbine ring 4 when the radial spring 70 is mounted on the turbine ring assembly 2. The metal plate 71 thus comprises a central boss 72 from which a tab 73 projects radially and also extends in a second direction orthogonal to the first direction and parallel to the axial direction DA when the radial spring 70 is mounted on the turbine ring assembly 2. The length of the tab in the axial direction DA is less than the length of the metal plate 71.

[0071] The central boss 72 is surrounded by two legs 74 having a boss opposite the central boss 72.

[0072] As illustrated in the figure 4which represents a sectional view along a plane comprising the axial direction DA and the radial direction DR at the level of a radial spring 70, the tongue 73 is axially arranged and held between the first radial attachment flange 64 and the second radial attachment flange 66. Radially, the radial spring 70 bears, via its tabs 74, against the base 12 of the ring sector 10 in which it is mounted and against the ferrule 60 of the ring support structure 6 via its tongue 73.

[0073] As illustrated in the figure 1 And 4 , and on the Figure 5which presents a sectional view of the turbine ring assembly 2 at a ring sector 10 along a sectional plane comprising the radial direction DR and the circumferential direction DC which is orthogonal to the radial direction DR and to the axial direction DA, the ring assembly further comprises a sealing tab 8 having an L shape with a small portion 82 and a large portion 84.

[0074] The large portion extends in the axial direction DA between an upstream end 86 and a downstream end 88. The small portion 82 extends radially outward from the upstream end 86 of the large portion 84.

[0075] The sealing tab 8 is arranged at each junction between two ring sectors 10. The small portion 82 makes it possible to maintain the sealing tab 8 axially in position and to prevent it from moving downstream and damaging the downstream radial flange 68 of the ring support structure 6.

[0076] The present invention thus provides a turbine ring assembly having a reduced number of parts, thereby reducing the risk of leakage and improving the robustness of the ventilation and sealing of the assembly while ensuring the maintenance of the ring sectors made of CMC material. In addition, the turbine ring assembly according to the invention does away with the manufacturing dispersion of the CMC ring sectors and makes it possible to reduce the tangential stresses at the ring maintenance devices. In addition, the turbine ring assembly can be integrated into a wider range of turbines.

Claims

1. A turbine ring assembly (2) extending around an axis (X-X), comprising a plurality of ring sectors (10) made of ceramic matrix composite material, forming a turbine ring (4) and a ring support structure (6) held by a turbine casing, each ring sector (10) comprising a base (12) from which an upstream latching tab (16) and a downstream latching tab (14), spaced axially away from one another, extend radially outward, the assembly (2) additionally comprising: - a cross-member (20) mechanically connected to the ring support structure (6) and comprising a first radial flange (210) bearing against the upstream latching tabs (16) of the ring sectors (10), and - for each ring sector (10), at least two transverse pins (40) and a radial spring (70), each transverse pin (40) passing though the upstream latching tab (16) and the downstream latching tab (14) of the ring sector (10) and the ring support structure (6) to hold the ring sector (10) and the ring support structure (6) secured to one another, the ring support structure (6) also comprising a second radial flange (68) bearing against the downstream latching tabs (14) of the ring sectors (10), the upstream latching tab (16) and the downstream latching tab (14) of each ring sector (10) being arranged axially between the first radial flange (210) and the second radial flange (68), characterized in that the assembly (2) further comprises a radial spring (70) being held bearing, in a radial direction (DR) orthogonal to the axial direction (X-X), against the ring sector (10) on the one hand and against the ring support structure (6) on the other hand to hold the ring sectors arranged at the same radial position and in that said first radial flange (210) comprises a first portion (2103) and a second portion (2104) radially inside the first portion (2103), the second portion (2104) including a first tab (2105) and a second tab (2106) axially distant from one another and both secured to the first portion (2103), the first tab (2105) being axially upstream of the second tab (2106), and the second tab (2106) bearing against the upstream latching tab (16).

2. The assembly (2) according to claim 1, wherein the downstream tab (2106) of said first radial flange (210) comprises a first end which is secured to the first portion (2103) of the first radial flange (210) and a second end which is free and opposite to the first end, the downstream tab (2106) also comprising radial slots (222) regularly spaced angularly and each extending from the second end to an opening (224), the number of radial slots (222) being at most equal to the number of ring sectors (10).

3. The assembly (2) according to one of claims 1 or 2, wherein the cross-member (20) comprises a bell housing (202) arranged around the turbine ring (4), and the ring support structure (6) comprises a shroud (60) arranged radially between the turbine ring (4) and the bell housing (202) of the cross-member (20).

4. The assembly (2) according to claim 3, wherein the bell housing (202) of the cross-member (20) comprises injection openings (220) and the shroud (60) of the ring support structure (6) comprise complementary injection openings (600) axially offset relative to the injection openings (220).

5. The assembly (2) according to one of claims 3 or 4, also comprising a C-shaped annular seal (50) extending between the bell housing (202) of the cross-member (20) and the shroud (60) of the ring support structure (6), the C-shaped annular seal (50) being coaxial with the bell housing (202) of the cross-member (20) and the shroud (60) of the ring support structure (6).

6. The assembly (2) according to one of claims 1 to 5, wherein the ring support structure structure (6) also comprises a first radial support flange (64) and a second radial support flange (66) axially distant from the first radial support flange (64), each transverse pin (40) passing through the first radial support flange (64) and the second radial support flange (66).

7. The assembly (2) according to any one of claims 1 to 6, wherein the radial spring (70) comprises a metal plate (71) corrugated so as to have at least one camber (72).

8. The assembly (2) according to the combination of claims 6 and 7, wherein the radial spring (70) also comprises a tab (73) protruding from the peak of the camber (72) and extending along the camber (72) over a length less than the axial length of the metal plate (71), the tab (73) being arranged between the first and the second axial support flanges (64, 66).

9. The assembly (2) according to one of claims 1 to 8, also comprising an L-shaped sealing tab (8) arranged at each junction between two adjacent ring sectors (10), each sealing tab (8) comprising a large portion (84) extending axially and a small portion (82) extending radially, the small portion (82) being secured to the large portion (84) at an upstream end (86) of the large portion (84).

10. The assembly (2) according to any one of claims 1 to 9, also comprising a thermal protection ring (52) mounted radially inside of the second radial flange (68), the second radial flange (68) also comprising discharge holes (680) passing axially through said second radial flange (68).

11. A turbomachine comprising an assembly (2) according to any one of claims 1 to 10.