Turbine assembly and gas turbine engine provided with such an assembly

Abstract

A turbine assembly (1), the turbine assembly comprising: - a plurality of turbine ring segments (20) made of a ceramic matrix composite material; - a ring support structure (3), the ring support structure including an annular shroud (6); and in addition - a plurality of angular spacer segments (70), the plurality of angular spacer segments together forming an annular spacer (7), the annular spacer (7) being fixed on the one hand to a turbine ring (2) and on the other hand to the annular shroud (6), characterized in that the turbine assembly (1) includes at least one air diffuser (8), the at least one air diffuser being configured to diffuse cooling air onto a radially outer face (212) of at least one of the turbine ring segments (20), and in a nested position, the at least one air diffuser (8) is mounted by being nested in one of the angular spacer segments (70).

Description

Technical Field

[0001] The present invention relates to a turbine assembly comprising a plurality of ring segments and a ring support structure, the plurality of ring segments being made of a ceramic matrix composite (CMC), and the plurality of ring segments being assembled to form a turbine ring.

[0002] The application field of the present invention is particularly an aircraft gas turbine engine or a turbine. However, the present invention is applicable to other turbines, such as industrial turbines. Background Art

[0003] In an aircraft gas turbine engine, the improvement of efficiency and the reduction of some pollutant emissions have led to the search for operation at higher temperatures. From the current state of the art, all-metal turbine ring assemblies are known. However, it is necessary to cool all the elements of the assembly, especially the turbine ring, because the turbine ring is subjected to a very hot flow, the temperature of which is higher than the temperature that the metal material can withstand.

[0004] However, this cooling has a significant impact on the performance of the engine because the cooling flow used is taken from the main flow of the engine. In addition, the metal used for the turbine ring limits the possibility of increasing the turbine temperature, which would however improve the performance of the aeroengine.

[0005] To solve the above problems, it is envisaged to produce turbine ring segments made of a ceramic matrix composite (CMC) to avoid using metal materials.

[0006] It is well known that ceramic matrix composites can maintain their mechanical properties at temperatures significantly higher than those of metals, which enables ceramic matrix composites to form hot structural elements. Using this type of material makes it possible to reduce the cooling flow rate of the components, thereby improving the performance of the turbine. In addition, the advantage of CMC materials is that they have a lower density than the metals commonly used to produce turbine rings. This makes it possible to envisage a significant mass reduction of the entire turbine.

[0007] The production of turbine ring segments from a single CMC material block is particularly described in document US 2012 / 0027572. The ring segment includes an annular base and an outer face, the inner face of the annular base defining the inner face and the outer face of the turbine ring, and two struts extending radially from the outer face, the ends of the struts being held between two flanges of a metal ring support structure.

[0008] Thus, using CMC ring segments makes it possible to significantly reduce the ventilation required to cool the turbine ring. However, CMC has mechanical properties different from those of metal materials, and the integration of CMC and the way of positioning it within the turbine must be redesigned. In fact, CMC cannot withstand shrink-fit installation (commonly used for metal rings), and the thermal expansion of CMC is lower than that of metal materials.

[0009] The document WO 2015 / 191 169 has disclosed a turbine assembly, which includes a plurality of turbine ring segments made of ceramic composite materials, a support structure held by an external housing (the structure includes an annular shroud and an annular spacer segment), and an air deflector for diffusing air.

[0010] The document WO 2015 / 108 658 has also disclosed a turbine assembly, which includes a ring support structure and a plurality of turbine ring segments that together form a turbine ring. The assembly also includes a deflector provided with channels, which enables cooling air to be introduced onto the radial inner surface of the turbine ring segments.

[0011] Finally, the document EP 3 118 417 has disclosed a turbine assembly, which includes a plurality of turbine ring segments made of CMC ceramic material and a ring support structure. The deflector can be radially arranged between the support and the ring segments.

[0012] However, none of these documents describe or suggest installing the air diffuser by interlocking on one of the said spacer segments, nor do they describe or suggest the structure of the air diffuser according to the present invention. Summary of the Invention

[0013] An object of the present invention is to provide a turbine ring assembly that does not have the above-mentioned drawbacks. In particular, the turbine ring assembly is lighter than the turbine ring assemblies known in the prior art, and, in particular, all bolt connections that are usually present in such assemblies are removed.

[0014] To this end, the present invention relates to a turbine assembly extending around a longitudinal axis, the assembly including:

[0015] - a plurality of turbine ring segments made of ceramic matrix composite materials, the turbine ring segments being assembled end to end circumferentially to form a turbine ring, each turbine ring segment including a base having a radial inner surface and a radial outer surface, and an upstream strut and a downstream strut extending radially outward from the radial outer surface and axially spaced apart from each other;

[0016] - a ring support structure held by an external annular turbine housing, the ring support structure including an annular shroud and a plurality of angular spacer segments that together form an annular spacer, the annular spacer being fixed to the annular shroud, and each turbine ring segment being fixed to the annular spacer by the struts;

[0017] - at least one air diffuser configured to diffuse cooling air on the radial outer surface of at least one of the turbine ring segments.

[0018] According to the invention, the at least one air diffuser is mounted in an interlocking manner on one of the corner spacer sections, in an interlocked position. The air diffuser has an internal cavity and a radial internal face, which is penetrated by a plurality of air injection holes opening into the cavity. Each corner spacer section has a radial internal face and has a linear interlocking slot on the radial internal face of the corner spacer section. The linear interlocking slot has an interlocking region with a T-shaped cross-section on a part of the length of the linear interlocking slot. And each air diffuser is also provided with a T-shaped attachment member in the radial outer part of the air diffuser. The T-shaped attachment member is configured to be received and interlocked into the interlocking region. The attachment member of the air diffuser is penetrated by an air inlet hole opening into the internal cavity. And each corner spacer section includes at least one air supply duct. The at least one air supply duct opens into one of the upstream faces of the corner spacer section on the one hand and opens into the bottom of the T-shaped interlocking region of the slot on the other hand, facing the mouth of the air inlet hole of the attachment member of the diffuser. When the diffuser is in its interlocked position, the air supply duct is in fluid communication with the air injection holes.

[0019] Thanks to these features of the invention, in particular thanks to the interlocking of the air diffuser on one of the corner spacer sections, the installation of the diffuser is simplified. The diffuser no longer needs to use sleeves or pins for fixing, and the total mass of the turbine ring assembly is reduced.

[0020] In addition, this installation makes it possible to maintain the use of rings made of ceramic matrix composites and the associated advantages. According to other advantageous and non-limiting features of the invention, these features are taken alone or in combination:

[0021] - The attachment member includes at least one abutment portion that cooperates with the T-shaped interlocking region of the interlocking slot so as to prevent the axial displacement of the air diffuser once the air diffuser is in the interlocked position;

[0022] - Each corner spacer section includes an upstream hook portion and a downstream finger portion directed axially downstream. The annular shroud includes two annular grooves opening upstream, and these grooves are intended to receive the upstream hook portion and the downstream finger portion respectively;

[0023] - Each spacer section is provided with an upstream flange. The nozzles of the turbine are formed in a crown disposed upstream of the turbine ring assembly. The nozzles of the turbine are axially pressed against the upstream flange to hold the upstream hook portion and the downstream finger portion in the corresponding grooves of the annular shroud respectively;

[0024] - The annular shroud includes a downstream flange. The thickness of the downstream flange in the axial direction of the turbine ring is generally less than the thickness of the downstream strut of the ring section. The downstream flange applies stress to the downstream strut of the ring section;

[0025] - The upstream struts of the ring section are fixed to the upstream flange of the spacer section using fixed pins (pions), each spacer section including a plurality of downstream struts, and the downstream struts of the ring section are fixed to at least one downstream strut of the same spacer section using fixed pins, the pins extending mainly axially;

[0026] - Each corner spacer section has sealing slots at its two circumferential ends for receiving sealing tabs, these sealing tabs being arranged in said sealing slots and being located between two circumferentially arranged corner spacer sections connected end to end.

[0027] The invention also relates to a turbine comprising a turbine assembly as described above. Description of the Drawings

[0028] Other features, objects and advantages of the present invention will be presented by the following description, which is entirely illustrative and non - restrictive and should be read in conjunction with the drawings, in which:

[0029] - Figure 1 A longitudinal sectional view of a turbine assembly installed in a turbine according to the present invention is shown.

[0030] - Figure 2 is an enlarged longitudinal sectional view of the turbine assembly according to the present invention.

[0031] - Figure 3 is a front view of one end of the corner spacer section.

[0032] - Figure 4 is a perspective view of an air diffuser according to the present invention.

[0033] - Figure 5 is a perspective and transparent view of a corner spacer section on which two diffusers are mounted.

[0034] - Figure 6 is a bottom view of a corner spacer section on which a diffuser is mounted.

[0035] - Figure 7 Similar to Figure 6 but without the diffuser. Detailed Description of the Invention

[0036] Now reference will be made to Figure 1 and Figure 2 to describe a turbine assembly 1 according to the present invention. The assembly 1 extends around a longitudinal axis X - X'.

[0037] In Figure 1 the arrow D Arepresents the axial direction of the turbine assembly 1, while the arrow D R represents the radial direction of the turbine assembly 1. To simplify the drawings, Figure 1 and Figure 2 are partial views of the assembly, which is actually annular.

[0038] In particular, the assembly 1 includes a turbine ring 2 and a ring support structure 3. The turbine ring is made of a ceramic matrix composite (CMC) and is centered on the longitudinal axis X-X'. The ring support structure is held by an external annular turbine housing 4 and is only visible Figure 1 in

[0039] The turbine ring 2 surrounds a turbine blade assembly 5.

[0040] In the remainder of the specification, the turbine described is a high-pressure turbine. However, the present invention also applies to a low-pressure turbine.

[0041] The turbine ring 2 is formed by a plurality of angular ring segments 20, which are placed circumferentially end to end to form a ring.

[0042] Each angular ring segment 20 has a segment with a shape approximately like an inverted Greek letter Pi (or Π) with a base 21. The base has a radially inner face 211 and a radially outer face 212. The radially inner face defines an angular portion of the inner face of the turbine ring 2, and the radially outer face defines an angular portion of the outer face of the turbine ring. The upstream strut 22 and the downstream strut 23 extend radially outward from the radially outer face.

[0043] The terms "upstream" and "downstream" used here refer to the flow direction of the gas flow within the turbine ring, as indicated by the arrows F in Figure 1 and Figure 2 . The two struts 22 and 23 extend circumferentially above the entire width of the ring segment. The two struts are axially spaced from each other.

[0044] The upstream strut 22 is penetrated by a plurality of axial holes 220, and the downstream strut 23 is penetrated by a plurality of axial holes 230.

[0045] Generally, the seal between two adjacent angular segments 20 is ensured by sealing tabs (not visible in the figures), which are received in sealing slots 24 arranged at the two ends of each ring segment 20. When the two segments 20 are assembled end to end, the slots 24 face each other.

[0046] The ring support structure 3 includes a plurality of different components assembled with each other, namely an annular shroud 6 and an annular spacer 7 according to the present invention.

[0047] The annular shroud 6 can be formed by a rotating part, that is to say, it extends over 360°, or is produced by an assembly of a plurality of angular sections arranged end to end.

[0048] As can be seen in Figure 2 the annular shroud 6 has: an upstream annular groove 61 which opens upstream; an intermediate annular groove 62 which also opens upstream; and finally a downstream annular groove 63 which opens downstream. These different annular grooves are centered on the longitudinal axis X-X' and these different annular grooves extend axially.

[0049] The downstream annular groove 63 is intended to receive the ends of the blades of the nozzles A (here, for example, low-pressure nozzles) of the low-pressure turbine, the ends of the blades of the nozzles A of the low-pressure turbine being arranged downstream of the high-pressure turbine and only visible in Figure 1 the figure.

[0050] In addition, the annular shroud 6 includes an annular downstream flange 64 which extends radially inwards and the end 640 of which bends upstream to extend axially. The flange 64 has a thickness along its radial part which is small enough for the flange to retain an elastic, flexible nature.

[0051] Finally, the annular shroud 6 has projections 65 along its radial outer face, which projections are intended to radially abut against the outer casing 4. The shroud 6 is fixed to the casing 4 by fixing means (shrink fit) not visible in the figure. According to another variant of an embodiment not shown in the figure, the shroud can be made in one piece with the outer casing 4.

[0052] The annular spacer 7 includes a plurality of angular spacer sections 70 assembled end to end circumferentially.

[0053] One of these spacer sections 70 is better shown in Figure 5 the figure. Each section 70 includes a curved body 71 which has a radial outer face 711 and a radial inner face 712. The curved downstream edge of the body 71 defines a downstream finger 713 oriented axially. The downstream finger 713 is intended to be inserted into the intermediate annular groove 62 of the shroud 6. As can be seen in Figure 2 the figure, the assembly of the spacer 7 and the shroud 6 is made such that the radial outer face of the downstream finger 713 bears against the radial inner face of the intermediate annular groove 62 to ensure a seal between the two parts.

[0054] An upstream hook 714 in the form of an annular section and oriented axially downstream projects outwards from the upstream end of the radial outer face 711. The upstream hook 714 is intended to be inserted into the upstream annular groove 61 of the annular shroud 6. As can be seen in Figure 2As can be seen, the assembly of the spacer 7 and the shroud 6 is made such that the radially outer face of the upstream annular groove 61 bears against the radially inner face of the upstream hook portion 714 to ensure a seal between the two components.

[0055] In Figure 2 it can also be seen that the upward contact of the downstream finger portion 713 and the downward contact of the upstream hook portion ensure the radial positioning of each spacer section 70 relative to the annular shroud 6 (tilting effect).

[0056] In addition, the body 71 includes an upstream flange 72 and a plurality of downstream lugs 73. In Figure 5 it can be seen that there are, for example, two of these lugs 73 on each section 70. Each lug 73 is penetrated by an axial hole 730. In addition, the flange 72 has a plurality of axially blind cavities 720 opening downstream.

[0057] The upstream flange 72 and the downstream lugs 73 extend radially or substantially radially in the direction of the interior of the ring assembly 1, that is to say in the direction of the axis X-X'.

[0058] The turbine ring assembly 1 also includes an upstream axial dowel 24 and a downstream axial dowel 25. The upstream axial dowel 24 is inserted into the blind cavity 720 and through the hole 220 to ensure that the upstream strut 22 of the ring section 20 is fixed to the upstream flange 72. The downstream axial dowel 25 is inserted through the axial hole 730 of the spacer 7 and the axial hole 230 of the ring section 20 to ensure that the downstream strut 23 of the ring section 20 is fixed to the lug 73. The different axial dowels are evenly distributed around the longitudinal axis X-X' of the ring.

[0059] When the assembly is complete, the lugs 73 are arranged upstream of the downstream strut 23 of the ring 2, and the upstream flange 72 is arranged upstream of the upstream strut 22.

[0060] In addition, the upstream strut 22 and the downstream strut 23 of each ring section 20 are respectively held between the upstream flange 72 and the flange 64, the upstream flange 72 and the flange 64 each exerting an axial stress on these struts, and the end 640 of the flange 64 bearing against the downstream face of the downstream strut 23, these axial stresses being opposite.

[0061] Generally, the upstream flange 72 is thicker in the axial direction (except in the area where the housing 720 is provided) than the radial part of the flange 64. Therefore, the upstream flange 72 is more rigid and the flange 64 is more flexible and deformable.

[0062] Finally, as in Figure 1As can be seen, the turbine ring assembly 1 is arranged between two nozzle stages, here between nozzle A (for example, a low-pressure nozzle) and nozzle B (here, for example, a high-pressure nozzle of a high-pressure turbine). The nozzle B upstream of this arrangement presses axially against the upstream flange 72. Thus, during operation, due to the high stiffness of the upstream flange 72, the spacer 7 ensures the force on the nozzle B by restricting the transfer of these forces to the CMC ring 2. The force transmitted to the ring 2 is also restricted by the flexible nature of the downstream flange 64.

[0063] Finally, once the assembly has been completed, the annular shroud 6 surrounds the annular spacer 7, which in turn surrounds the ring 2, such that these three elements are concentric and coaxial along the longitudinal axis X-X'.

[0064] Advantageously, as can be seen in Figure 5 each corner spacer section 70 has sealing slots 721 at its two ends for receiving sealing tabs. These tabs (not shown in the figure) are arranged between two corner spacer sections 70, which are arranged circumferentially end to end. This makes it possible to ensure the seal between two adjacent sections 70.

[0065] Preferably, these sealing slots 721 are arranged at the two ends of the upstream flange 72 and at the two ends of the hook portion 714.

[0066] The turbine assembly 1 further includes an air diffuser 8, which is intended to diffuse the cooling air on the radially outer face 212 of the base 21. The air diffuser 8 includes a wall that defines an internal cavity 80 (see Figure 2 ). In the exemplary embodiment shown in the figure, the wall of the air diffuser has a truncated pyramid shape.

[0067] The air diffuser 8 has a preferably planar radially inner wall 81, which is penetrated by a plurality of air injection holes 810.

[0068] According to the invention, each air diffuser 8 is mounted by interlocking on one of the corner spacer sections 70. In the Figure 5 example shown, two air diffusers 8 are mounted on the corner spacer section 70. These two air diffusers are in a position called "interlocked".

[0069] For this purpose, each corner spacer section 70 has a straight interlocking slot 74 on one of its radially inner faces (here its radially inner face 712) (see Figures 5 to 7 ). The slot is straight, that is, not curved, and the slot is arranged in the curved body 71.

[0070] Advantageously, the spacer section 70 is manufactured by additive manufacturing.

[0071] In addition, the slot 74 has a T-shaped cross-section forming an interlocking region 742 over part of its length, preferably in its central part. This T-shaped cross-section is better shown in the Figure 3 section shown. At this location, the slot 74 is locally (ponctuellement) provided with two tabs 740 which face each other and are spaced apart from each other to define the two branches of the T.

[0072] In addition, as can be seen in Figure 4 the air diffuser 8 also has a T-shaped attachment member 82 in its radially outer part (here at the top of the truncated pyramid), which T-shaped attachment member is configured to be received and interlocked by sliding in the slot 74. Since the sliding groove is straight, sliding is facilitated.

[0073] Advantageously, one of the ends of the attachment member 82 has two abutments 821 which are arranged on either side of the T. The horizontal branch 822 of the T-shaped attachment member is configured to be received in the slot 74, between the bottom of the slot and the two tabs 740, while the vertical branch 823 of the T is received between the two tabs 740. The radially outer face 824 of the member 82 is planar.

[0074] Complementary interlocking shapes other than T-shaped for the attachment member 82 and the slot 74 can also be envisaged.

[0075] Thus, the air diffuser 8 can be inserted by axially sliding from one of the ends of the section 70 into the slot 74 (insertion arrow G in Figure 6 ), the tabs 740 holding the horizontal branch 822 of the T until the two abutments 821 come into contact with the two corresponding tabs 740. Thus, these abutments 821 prevent axial sliding of the air diffuser 8 within the slot 740. The diffuser 8 cannot move further towards the center of the spacer section 70. Additional wedges (not shown in the figure) can be added to prevent displacement of the diffuser 8 in the direction opposite to its insertion direction.

[0076] In addition, the attachment member 82 is penetrated by at least one air intake hole 825 which opens both on the outer face 824 of the attachment member 82 and within the cavity 80.

[0077] Each corner spacer section 70 also includes at least one air supply duct 75 (two ducts 75 in the Figure 5 embodiment shown). Each duct 75 opens on the one hand onto the upstream face 76 of the corner section 70 and on the other hand onto the bottom of the slot 74, facing the part 74 of the slot having a T-shaped cross-section (interlocking region 742). As in Figure 5As can be seen, the duct 75 is configured such that when the air diffuser 8 is positioned to abut against the tab 740 within the slot 74 (interlocking position), the duct 75 opens at the mouth of the air inlet hole 825 of the attachment member 82 of the diffuser 8.

[0078] Accordingly, cooling air taken from a stage of the compressor of the turbine enters the duct 75 and then enters the diffuser 8, where the cooling air is ejected via the air ejection holes 810 in the direction of the inner face 212 of the ring segment base 21, thereby cooling the ring segment base.

[0079] Advantageously, the shroud 6, the spacer 7 and the diffuser 8 are made of metal.

Claims

1. A turbine assembly (1) extending about a longitudinal axis, the turbine assembly (1) comprising: - a plurality of turbine ring segments (20) made of ceramic matrix composite material, the turbine ring segments being assembled end-to-end circumferentially to form a turbine ring (2), each turbine ring segment (20) comprising a base (21) having a radially inner face (211) and a radially outer face (212), and an upstream strut (22) and a downstream strut (23) extending radially outward from the radially outer face and axially spaced from each other; - a ring support structure (3) held by an outer annular turbine housing (4), the ring support structure (3) comprising an annular shroud (6) and a plurality of angular spacer segments (70) which together form an annular spacer (7), the annular spacer (7) being fixed to the annular shroud (6), and each turbine ring segment (20) being fixed to the annular spacer (7) by the upstream strut (22) and the downstream strut (23); - at least one air diffuser (8) configured to diffuse cooling air over the radially outer face (212) of at least one of the turbine ring segments (20); characterized in that the at least one air diffuser (8) is mounted in an interlocking manner on one of the angular spacer segments (70) in an interlocking position, the air diffuser (8) having an internal cavity (80) and a radially inner face (81), the radially inner face of the air diffuser being penetrated by a plurality of air injection holes (810) opening into the internal cavity (80), each angular spacer segment (70) having a radially inner face and having a straight interlocking slot (74) on the radially inner face (712) of the angular spacer segment, the straight interlocking slot having an interlocking region (742) with a T-shaped cross-section over a part of the length of the straight interlocking slot, and each air diffuser (8) also being provided with a T-shaped attachment member (82) in the radially outer part of the air diffuser, the T-shaped attachment member being configured to be received and interlocked into the interlocking region (742), the attachment member (82) of the air diffuser (8) being penetrated by an air intake hole (825) opening into the internal cavity (80), and each angular spacer segment (70) comprising at least one air supply duct (75), the at least one air supply duct opening on the one hand into one of the upstream faces (76) of the angular spacer segment and on the other hand into the bottom of the T-shaped interlocking region (742) of the interlocking slot (74), facing the mouth of the air intake hole (825) of the attachment member (82) of the air diffuser (8), such that the air supply duct (75) is in fluid communication with the air injection holes (810) when the air diffuser (8) is in the interlocking position of the air diffuser.

2. The turbine assembly (1) according to claim 1, characterized in that, The attachment member (82) includes at least one abutment portion (821) that mates with a T-shaped interlocking region (742) of the interlocking slot (74) so as to prevent axial displacement of the air diffuser (8) once the air diffuser is in the interlocked position.

3. The turbine assembly (1) according to claim 1 or 2, characterized in that, Each corner spacer segment (70) includes an upstream hook (714) and a downstream finger (713) that are axially directed downstream. The annular shroud (6) includes two annular grooves (61, 62) that open upstream, and these annular grooves (61, 62) are adapted to receive the upstream hook (714) and the downstream finger (713), respectively.

4. The turbine assembly (1) according to claim 3, characterized in that, Each corner spacer segment (70) is provided with an upstream flange (72). The nozzles (B) of the turbine form a crown disposed upstream of the turbine assembly (1). The nozzles of the turbine are axially pressed against the upstream flange (72) to hold the upstream hook (714) and the downstream finger (713) in the corresponding annular grooves (61, 62) of the annular shroud (6), respectively.

5. The turbine assembly (1) according to claim 1 or 2, characterized in that, The annular shroud (6) includes a downstream flange (64). The thickness of the downstream flange (64) in the axial direction of the turbine ring (2) is generally less than the thickness of the downstream strut (23) of the turbine ring segment (20). The downstream flange (64) applies stress to the downstream strut (23) of the turbine ring segment (20).

6. The turbine assembly (1) according to claim 4, characterized in that, The upstream strut (22) of the turbine ring segment (20) is fixed to the upstream flange (72) of the corner spacer segment (70) using a first fixing dowel (24). Each corner spacer segment (70) includes a plurality of downstream lugs (73). The downstream strut (23) of the turbine ring segment (20) is fixed to at least one downstream lug (73) of the same corner spacer segment (70) using a second fixing dowel (25). The first fixing dowel (24) and the second fixing dowel (25) extend mainly axially.

7. The turbine assembly (1) according to claim 1 or 2, characterized in that, Each of the corner spacer segments (70) has a sealing slot (721) for receiving a sealing tab at two circumferential ends of the corner spacer segment. These sealing tabs are disposed in the sealing slot (721) between two circumferentially adjacent corner spacer segments (70) arranged end to end.

8. A turbine, the turbine including a turbine assembly (1) according to any one of claims 1 to 7.

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