AIRCRAFT TURBINE DISTRIBUTOR SECTION, FEATURING IMPROVED ROBUSTNESS

Abstract

The invention relates to a sector (40) of a turbine distributor for an aircraft turbomachine, comprising a first platform (44a), a plurality of blades (42) projecting from the first platform in a first direction (S1) of a radial direction (R) of this sector, and a first end member (50a) projecting from the first platform (44a) in a second direction (S2) of the radial direction, opposite to the first direction (S1), the first end member (50a) extending along a circumferential direction (C) of the sector. According to the invention, the sector comprises at least one first mechanical unloading notch (66a) formed through the first end member (50a), each first notch (66a) having a radial notch bottom (68a), as well as a radial notch opening (70a) spaced from the radial notch bottom (68a) in the second direction (S2). Figure for the abstract: Fig. 3

Description

Title of the invention: TURBINE DISTRIBUTOR SECTOR FOR AIRCRAFT TURBOMACHINE, EXHIBITING IMPROVED ROBUSTNESS technical field

[0001] The present invention relates to an aircraft turbomachine, preferably of the turbojet or turboprop type.

[0002] More particularly, the invention relates to the design of a turbine distributor for an aircraft turbomachine, such a distributor being known for example from document FR 2 825 748 Al. Prior art

[0003] A turbine distributor of an aircraft turbomachine is generally made up of several distributor sectors arranged end-to-end in a circumferential direction. Each sector usually comprises two platforms between which blades are arranged, spaced circumferentially from each other within the sector. Each of the two platforms presents a radial boundary surface for a primary flow of the turbomachine, allowing the channeling of a primary flow through the turbine, originating from the combustion chamber.

[0004] Furthermore, on the side radially opposite to that of the radial boundary surface of the primary flow, each platform carries one or more projecting end members. Each projecting end member extends circumferentially, generally along the entire length of the sector. For example, it could be a bracket for attaching the distributor sector to the turbine housing, or a support leg, for example, to support a sealing element of the abradable type.

[0005] Within the distributor sector, each platform and its protruding end element(s) together form a radial end structure subjected to significant thermal stresses. Indeed, on the side of the radial boundary surface of the primary flow, this surface is directly exposed to a very high temperature from the primary flow, while on the opposite side of this radial end structure, the temperature is usually much lower. This latter observation is explained not only by the radial distance from the primary flow, but also by the possible proximity of one or more cooling air cavities.

[0006] Each radial end structure therefore exhibits a high temperature gradient in the radial direction, which can generate a detrimental effect on the distributor sector, known as the "bimetallic strip effect." It is characterized by a different thermal expansion. The elongation of the structure is greater between the two aforementioned sides of each radial end structure. On the side of the radial boundary surface of the primary flow, the elongation of the structure is greater than on the opposite side, known as the cold side. The bimetallic effect then manifests as high mechanical stresses within the radial end structure, which tends to deform by bending. Since the distributor sector blades are connected to the two radial end structures, they too are subjected to high mechanical stresses, counteracting the deformation of these radial end structures. Due to the nature of the deformation of these two structures, the blades located at the circumferential ends of the sector are primarily subjected to tensile forces, while the blades located more centrally within the sector are mainly subjected to compressive forces between the two radial end structures.

[0007] These constraints on the blades of the distributor sector significantly impact the life of the sector, in particular due to the risk of cracks appearing on the blades located at the circumferential ends.

[0008] To address this issue, it is possible to use materials with greater fatigue and / or abrasion resistance to increase the mechanical robustness of the distributor sector. However, this solution proves particularly costly. Another solution involves manufacturing distributor sectors with a reduced circumferential amplitude to limit the aforementioned bimetallic effect. However, this solution remains disadvantageous in terms of distributor assembly time and costs, and it also increases the leakage cross-sections between the larger number of sectors.

[0009] There therefore remains a need for optimization of turbine distributor sectors, aimed at strengthening their mechanical robustness, while controlling assembly and manufacturing costs. Description of the invention

[0010] To meet the need expressed above, the invention first relates to a turbine distributor sector for an aircraft turbomachine, comprising a first platform, a plurality of blades projecting from the first platform in a first direction of a radial direction of this sector, and a first end member projecting from the first platform in a second direction of the radial direction, opposite to the first direction, the first end member extending along a circumferential direction of the sector.

[0011] According to the invention, the distributor sector comprises at least one first mechanical discharge notch made through the first end member, each first notch having a radial notch bottom, as well as a radial notch opening spaced from the radial notch bottom in the second direction.

[0012] Thanks to the presence of one or more mechanical unloading notches, the first end element is segmented into several circumferential portions, thus giving it a certain degree of flexibility. This flexibility on the cooler side is used to accommodate the thermal expansion on the hotter side of the first platform. Advantageously, this drastically reduces the bimetallic effect described previously. The deformation to be resisted by the sector blades is therefore reduced, so that these blades are subjected to less mechanical stress. Consequently, they can have an increased service life and require less maintenance / replacement of the distributor sector.

[0013] In other words, the presence of the mechanical unloading notches limits the variations in curvature between the cold and hot parts of the radial end structure, formed by the first platform and each associated first end member. This results in lower stress on the distributor sector blades, whose mechanical strength is advantageously improved.

[0014] Furthermore, the solution provided allows for greater uniformity in the behavior and stresses of all the blades within the same distributor sector. Moreover, the number of blades per sector can be increased, which advantageously reduces the number of sectors to be joined end-to-end in the circumferential direction. Assembly time and costs are therefore reduced, as is aerodynamic performance, due to the reduction in the number of leakage sections per ring. In addition, when the end element is intended to bear against a turbine casing element, the contact forces are better distributed across the casing, advantageously reducing the risk of damage and leakage at the interfaces. Thanks to this more homogeneous distribution of forces on the casing element, wear on the latter is reduced, and the risks of sector tipping, resulting from such wear, are also diminished.By reducing the sector tilting effect, resulting from wear of the housing element, the distributor sector blades remain in an optimal position relative to the primary flow, implying increased turbine performance.

[0015] Finally, this solution allows for the use of less expensive materials in the manufacture of the distributor sector, and it also provides weight savings. As such, the invention therefore represents a result of technological research aimed at significantly improving aircraft performance and, in this respect, contributes to reducing the environmental impact of these aircraft (decarbonization).

[0016] The invention preferably provides for at least one of the following optional technical features, implemented individually or in combination.

[0017] Preferably, each first notch opens axially on either side of the first extremity organ.

[0018] Preferably, each first notch has a radial depth greater than at least 20% of a maximum radial length of the first end member, and more preferably greater than at least 50%, or even 70% of this maximum radial length, while preferably remaining strictly less than this maximum radial length.

[0019] Preferably, the first end member is one of the following elements:

[0020] - a distributor sector attachment tab;

[0021] - a support leg, preferably supporting a sealing element. Al Alternatively, the support leg can be replaced by a connecting leg to another mechanical structural component, such as flange clamps.

[0022] Preferably, the first end member comprises a web projecting from the first platform, as well as a base carried by the web at a distance from the first platform, each first notch radially traversing the entire base, and preferably at least a part of the web.

[0023] Preferably, the first notch has a circumferential width which narrows from the radial bottom of the notch to the radial opening of the notch.

[0024] Preferably, the distributor sector includes at least one sealing tab that closes at least part of the first discharge notch. This advantageously reduces leakage through the discharge notch.

[0025] Preferably, the distributor sector comprises a second platform from which the blades project in the second direction of the radial direction, as well as a second end member projecting from the second platform in the first direction, the second end member extending along the circumferential direction of the sector. Furthermore, the sector also comprises at least one second mechanical discharge notch formed through the second end member, each second notch having a radial notch bottom, as well as a radial notch opening spaced from the radial notch bottom in the first direction. In this regard, it is specified that all the optional features described previously for the first end member and its first discharge notch(s) are applicable to the second end member and its second discharge notch(s).

[0026] The invention also relates to a turbine distributor for an aircraft turbomachine, comprising at least one such distributor sector, and preferably several of these sectors arranged end to end in the circumferential direction.

[0027] Finally, the invention relates to an aircraft turbomachine, comprising at least one such turbine distributor, for low pressure or high pressure turbine.

[0028] Other advantages and features of the invention will become apparent from the following detailed, non-limiting description. Brief description of the drawings

[0029] The detailed description that follows refers to the accompanying drawings in which:

[0030] [Fig-1] is a schematic axial cross-sectional view of a turbojet engine according to the invention

[0031] [Fig.2] is a half-axial cross-sectional view of part of a turbine stage of the tur- bomachine represented in the previous figure, the turbine stage comprising a distributor being in the form of a preferred embodiment of the invention;

[0032] [Fig.3] is an enlarged perspective view of a distributor sector, forming part of the distributor shown in [Fig.2];

[0033] [Fig.4] is a cross-sectional view of part of the sector shown in [Fig.3], showing more specifically a first mechanical unloading notch;

[0034] [Fig.5] is a cross-sectional view of part of the sector shown in [Fig.3], showing more specifically a second mechanical unloading notch;

[0035] [Fig.6] is a perspective view of part of the sector shown in [Fig.3], showing more specifically a first mechanical unloading notch, sealed by sealing tabs;

[0036] [Fig.7] is a cross-sectional view of the part of the sector shown in [Fig.6], the cutting plane passing through the sealing tabs;

[0037] [Fig.8] is a perspective view of part of the sector shown in [Fig.3], showing more specifically another first mechanical unloading notch, sealed by sealing tabs;

[0038] [Fig.9] is a cross-sectional view of the part of the sector shown in [Fig.8], the cutting plane passing through the sealing tabs. Detailed description of implementation methods

[0039] The figures include a reference frame L, R and C defining respectively longitudinal, radial and circumferential directions orthogonal to each other, these directions corresponding to those of an aircraft turbojet 1 according to the invention.

[0040] Figure 1 represents the aircraft turbojet engine 1, preferably having a twin-spool, twin-flow design. However, other types of turbojet engines are possible, as are turbomachinery other than turbojet engines, such as turboprop engines.

[0041] Hereafter, the terms "upstream" and "downstream" are defined with respect to a principal direction DI of gas flow through the turbojet 1 when it is operating in direct thrust mode. The direction DI is parallel to the longitudinal direction L, and also parallel to a longitudinal axis Al of the turbojet, around which its various components extend. In this case, from upstream to downstream of the turbojet 1, these are a fan 4, a low-pressure compressor 5, and a high pressure compressor 6, a combustion chamber 7, a high pressure turbine 8 and a low pressure turbine 9.

[0042] During the operation of the turbojet 1, an airflow 10 enters the turbojet 1 through an air inlet 3, passes through the fan 4, and then splits into a central primary flow 10A and a secondary flow 10B. The primary flow 10A flows in a main gas circulation channel 11A passing through the compressors 5 and 6, the combustion chamber 7, and the turbines 8 and 9. The secondary flow 10B, on the other hand, flows in a secondary channel 11B surrounding the main channel 11A, also called the primary channel, or aerodynamic flow channel.

[0043] In a manner known per se, a turbine such as the high-pressure turbine 8 or the low-pressure turbine 9 comprises one or more stages 12. Each stage 12 comprises a stator assembly 12A including a distributor 29, also called a stator bladed ring, and a runner 12B, arranged directly downstream of the assembly 12A. Such a stage 12 is shown in [Fig. 2].

[0044] With reference now to Figures 2 to 5, the turbine distributor 29, preferably integrated into the high-pressure turbine 8 and centered on the axis AL, will be described. The distributor 29, in the shape of a crown, is traversed in its center by one or more drive shafts 30, also centered on the axis AL.

[0045] The distributor 29 is made up of several distributor sectors 40, arranged end to end along the circumferential direction C. Each sector 40, corresponding to an angular sector of the ring, has two platforms between which blades 42 are arranged, spaced circumferentially from each other within the sector. The sector 40 may, for example, comprise between two and ten blades 42. Only one of the sectors 40 will be described below, but it should be noted that the other sectors 40 of the ring may have an identical or similar design.

[0046] The two platforms of sector 40 correspond respectively to a radially external platform, referred to as the first platform 44a, and to a radially internal platform, referred to as the second platform 44b. An inverse arrangement is also conceivable, without departing from the scope of the invention.

[0047] The blades 42 are thus in projection from the first platform 44a in a first direction SI of a radial direction R of the sector, while these same blades 42 are in projection from the second platform 44b in a second direction S2 of the radial direction R, opposite to the first direction SL Here, the first direction SI of the direction R goes radially from the outside to the inside, and conversely for the second direction S2.

[0048] The first platform 44a comprises two opposing surfaces in the radial direction R, namely a first radial boundary surface 46a of the primary vein 1 IA oriented in the SI direction, and a first outer surface 48a of the sector, oriented in the direction S2. Similarly, the second platform 44b has two opposite surfaces in the radial direction R, namely a second radial boundary surface 46b of the primary vein 1 IA oriented in the direction S2, and a second outer surface 48b of the sector, oriented in the direction SI.

[0049] The distributor sector 40 comprises, at one radial end thereof, at least one first end member 50a, projecting from the first outer surface 48a, in the second direction S2 of the direction R. Each first end member 50a extends preferentially along the circumferential direction C of the sector 40, and more preferably along its entire length. These are two mounting lugs 50a for attaching the distributor sector 40 to one or more turbine housing elements 52, as shown in [Fig. 2]. These mounting lugs 50a cooperate, in a conventional manner, with associated hooks provided on the turbine housing elements 52. The upstream mounting lug 50a has a hook shape facing upstream, while the other downstream mounting lug 50a has a hook shape facing downstream.Between these tabs 50a, for example, a cooling air cavity 54 is defined, radially delimited inwards by the first outer surface 48a of the first platform 44a. It is noted that this first platform 44a, together with the two mounting tabs 50a, forms a first radial end structure, subject to differential thermal expansion for the reasons explained above. In this regard, it is noted that the mounting tab(s) 50a could be non-hook-shaped and have a simpler shape designed to support their ends against the housing.

[0050] Similarly, the distributor sector 40 comprises, at one radial end thereof, at least one second end member 50b projecting from the second outer surface 48b, in the first direction SL. Each second end member 50b extends preferentially along the circumferential direction C of the sector 40, and more preferably along its entire length. This is a support leg 50b for an abradable part 56 of a labyrinth seal, as shown in [Fig. 2]. The support leg 50b radially crosses a defined free space between two axial spoilers 58 provided respectively on the two movable turbine wheels 12B located on either side of the distributor 29. Also, at least a part of this leg 50b is housed in a cooling air cavity 60, and / or participates in delimiting one or more cavities of this type.Alternatively, the 50b support leg could be replaced by a connecting leg to another structural part, for example by being inserted into a flange clamp.

[0051] It is noted that the second platform 44b forms, with the support leg 50b, a second radial end structure, also subject to differential thermal expansion, for the reasons explained above.

[0052] As can be most clearly seen in [Fig. 4], each mounting bracket 50a has a web 62a projecting in the direction S2 from the first outer surface 48a of the first platform 44a. This web 62a is oriented radially, or inclined with respect to the radial direction. In addition, each mounting bracket 50a also has a flange 64a supported by the web 62a, at a distance from the platform, and oriented axially or substantially axially. The web 62a and the flange 64a together constitute a cross-section element generally shaped like an L, the angle between the web and the flange being on the order of 90°, or a greater value, for example on the order of 100 to 150°, as is the case for the upstream element 50a.

[0053] Similarly, as best seen in [Fig. 5], the support leg 50b has a web 62b projecting in the SI direction from the second outer surface 48b of the second platform 44b. This web 62b is oriented radially, or substantially radially. Furthermore, the support leg 50b may also have a flange 64b carried by the web 62b, at a distance from the platform, and oriented axially or substantially axially. The web 62b and the flange 64b together constitute a cross-sectional element generally shaped like a T, the angle between the web and the flange being approximately 90°, or a different value.

[0054] In order to avoid or greatly limit the bimetallic effect described above on the two radial end structures of the distributor sector 40, one of the features of the invention lies in the provision of one or more mechanical unloading notches.

[0055] More specifically, as shown in [Fig. 3], each latching lug 50a is traversed by at least one first mechanical unloading notch 66a, and preferably by several notches 66a spaced circumferentially from each other. Each first notch 66a has a radial notch bottom 68a, as well as a radial notch opening 70a spaced from the radial notch bottom 68a in the second direction S2.

[0056] Each first notch 66a is through, in that it opens axially on both sides of the attachment lug 50a on which it is formed. Here, each notch 66a radially passes through the entire base 64a, and preferably at least a part of the web 62a, on which the radial bottom of the notch 68a is therefore located.

[0057] The first notches 66a provided on one of two hooking tabs 50a can be offset circumferentially with respect to the first notches 66a provided on the other of the two hooking tabs 50a.

[0058] Similarly, the support leg 50b can be traversed by at least one second mechanical unloading notch 66b, and preferably by several notches 66b spaced circumferentially from each other. Every second notch 66b has a radial bottom of notch 68b, as well as a radial opening of notch 70b spaced from the radial bottom of notch 68b in the first SI direction.

[0059] Each second notch 66b is through, in that it opens axially on both sides of the support leg 50b on which it is formed. Here, each notch 66b radially passes through the entire base 64b, and preferably at least a part of the web 62b, on which the radial bottom of the notch 68b is therefore located.

[0060] Regardless of the notch in question 66a, 66b, it has a radial depth Pr greater than at least 20% of a maximum radial length Lrmax of its associated end member 50a, 50b, and more preferably greater than at least 50%, or even 70%, of this maximum radial length Lrmax. However, the radial depth of the notch Pr, measured along the radial direction R between the bottom 68a, 68b and the point of the radial notch opening 70a, 70b furthest from this bottom in this direction R, preferably remains strictly less than this maximum radial length Lrmax, also measured along the direction R, from the outer surface of the platform 48a, 48b.

[0061] It is noted that the radial depth Pr of the notches 66a, 66b preferably remains greater than or equal to the thickness of the flanges 64a, 64b, when such flanges, usually axially or substantially axially oriented, are provided. In other words, each notch 66a, 66b extends sufficiently deep to pass through at least the flange 64, 64b, and preferably also through at least a portion of the web 62a, 62b.

[0062] The number of notches 66a, 66b per organ 50a, 50b can vary, for example from two to ten, depending on the circumferential length of the sector 40.

[0063] The shape of the notches 66a, 66b can be adapted according to the needs and constraints encountered. For example, as shown in one of the first notches 66a in [Fig. 3], its circumferential width Le narrows from the radial bottom of the notch 68a to the radial opening of the notch 70a. This principle can be applied to some or all of the mechanical unloading notches 66a, 66b.

[0064] As previously mentioned, the presence of the mechanical unloading notches 66a, 66b makes it possible, in particular, to limit the variations in curvature between the cold and hot parts of each of the two radial end structures, formed by the platform 44a, 44b and its associated end member 50a, 50b. This results in lower stress on the distributor sector blades, whose mechanical strength is advantageously improved, and an increased service life. Indeed, thanks to the presence of the mechanical unloading notches, the end members 50a, 50b are each segmented into several circumferential portions, thus giving them a certain degree of flexibility in deformation. This flexibility on the cooler side is used to accommodate the thermal expansion on the warmer side of the platforms 44a, 44b. The bimetallic effect described previously is thus significantly reduced. Furthermore, the solution according to the invention allows for greater uniformity in the behavior and stresses of all the blades 42 in the same sector 40. The number of blades 42 per distributor sector 40 can therefore be increased, which reduces the number of sectors to be joined end-to-end along the circumferential direction C. Assembly time and costs are thus reduced, as is aerodynamic performance, due to the reduction in the number of leakage sections per ring.

[0065] Furthermore, with the first end members 50a bearing against the turbine casing elements 52, the contact forces are better distributed on these elements 52, advantageously reducing the risk of sagging and leakage at the interfaces with the sector 40. Thanks to this more homogeneous distribution of forces on the casing elements 52, their wear is reduced, and the risks of sector tilting, resulting from such wear, are also diminished. By reducing the tilting effect of the distributor sector 40, the distributor sector blades 42 remain in an optimal position with respect to the primary flow, resulting in increased turbine performance.

[0066] With reference now to figures 6 and 7, the upstream attachment lug 50a is shown, in which one or more of the discharge notches 66a is at least partially closed by a sealing tab, in order to prevent leaks through these notches.

[0067] In the embodiment shown, two sealing tabs 72, 74 are provided for each notch 66a. Tab 72 is dedicated to sealing the portion of the notch 66a through the web 62a, while the other tab 74 is dedicated to sealing the portion of the notch 66a through the base 64a. Each of these tabs 72, 74 is guided and held at its two opposite circumferential ends in rail-shaped slots 76, formed in the opposite circumferential flanks of the notch 66a.

[0068] Here, for example, the tongue 72 is first slid into its associated rails 76 from the outside of the base 64a, and then, once at the bottom of its rails, the other tongue 74 is slid into its associated rails 76 from the outside of the web 62a, also to the bottom of its rails. In its final position, the tongue 74 extends sufficiently to cover the tongue 72, thus preventing the latter from sliding out along its rails 76. The tongue 72 therefore requires no other means of holding it in position, while the tongue 74 can be held in its rails 76 by one or more weld points 78, one of which has been schematically shown in the [Fig.7].

[0069] The tabs 72, 74 can be made of any material chosen so that the tabs do not affect the flexibility of the radial end structure once installed. They have a thinner profile than their associated component 50a, 50b and serve solely for sealing purposes, to limit leakage through the notches 66a, 66b.

[0070] Figures 8 and 9 represent another embodiment on the downstream attachment lug 50a, with a principle analogous to two tabs 72, 74. The tab 74 is no longer held in its rails 76 by a weld point, but by a stop member 80 external to the sector 40, for example formed by an adjacent ferrule, or any other stator element.

[0071] Other technical solutions for retaining the tabs can be considered, such as folding these tabs. Furthermore, it is noted that this principle of sealing tabs can also be applied to the notches 66b of the support leg 50b, without departing from the scope of the invention.

[0072] Of course, various modifications can be made by a person skilled in the art to the invention which has just been described only by way of non-limiting examples, and within the limits of the scope of the annexed claims.

Claims

Demands

1. Turbine distributor sector (40) for an aircraft turbomachine, comprising a first platform (44a), a plurality of blades (42) projecting from the first platform in a first direction (SI) of a radial direction (R) of this sector, and a first end member (50a) projecting from the first platform (44a) in a second direction (S2) of the radial direction, opposite to the first direction (SI), the first end member (50a) extending along a circumferential direction (C) of the sector, characterized in that it comprises at least one first mechanical unloading notch (66a) formed through the first end member (50a), each first notch (66a) having a radial notch bottom (68a), and a radial notch opening (70a) spaced from the radial notch bottom (68a) in the second direction (S2).

2. Distributor sector according to claim 1, characterized in that each first notch (66a) opens axially on either side of the first end member (50a).

3. Distributor sector according to claim 1 or 2, characterized in that each first notch (66a) has a radial depth (Pr) greater than at least 20% of a maximum radial length (Lrmax) of the first end member (50a), and more preferably greater than at least 50%, or even 70% of this maximum radial length (Lrmax), while preferably remaining strictly less than this maximum radial length (Lrmax).

4. Distributor sector according to any one of the preceding claims, characterized in that the first end member is one of the elements among which: - a tab (50a) for attaching the distributor sector; - a support leg (50b), preferably supporting a sealing member (56).

5. Distributor sector according to any one of the preceding claims, characterized in that the first end member (50a) has a web (62a) projecting from the first platform (44a), and a base (64a) carried by the web at a distance from the first platform (44a), each first notch (66a) radially through the entire base (64a), and preferably at least a portion of the web (62a).

6. Distributor sector according to any one of the preceding claims, characterized in that the first notch (66a) has a circumferential width (Lr) which narrows from the radial bottom of the notch (68a) to the radial opening of the notch (70a).

7. Distributor sector according to any one of the preceding claims, characterized in that it comprises at least one sealing tab (72, 74) closing at least a part of the first discharge notch (66a).

8. Distributor sector according to any one of the preceding claims, characterized in that it comprises a second platform (44b) from which the blades (42) project in the second direction (S2) of the radial direction (R), and a second end member (50b) projecting from the second platform (44b) in the first direction (SI), the second end member (50b) extending along the circumferential direction (C) of the sector, and in that it also comprises at least one second mechanical discharge notch (66b) made through the second end member (50b), each second notch (66b) having a radial notch bottom (68b), and a radial notch opening (70b) spaced from the radial notch bottom (68b) in the first direction (SI).

9. Turbine distributor (29) for aircraft turbomachine, comprising at least one distributor sector (40) according to any one of the preceding claims.

10. Aircraft turbomachine (1), comprising at least one turbine distributor (29) according to the preceding claim.

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