EP3857028A1

EP3857028A1 - Improved turbomachine stator

Info

Publication number: EP3857028A1
Application number: EP19787014.0A
Authority: EP
Inventors: Hugo Louis Rousseaux; Pamela Jessica BENEVENT; Léna JEFFROY
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2018-09-26
Filing date: 2019-09-06
Publication date: 2021-08-04
Anticipated expiration: 2039-09-06
Also published as: WO2020065161A1; FR3086329B1; US11408292B2; CN112771247A; CN112771247B; EP3857028B1; US20220042419A1; FR3086329A1

Abstract

Turbine stator for a turbomachine extending around an axis, the stator comprising a plurality of sectors each comprising at least one vane which extends radially between an inner platform and an outer platform, the stator comprising at least two sealing blades (12) each comprising a main portion (120) that is configured so as to ensure a seal between the stator and an element (1) of the turbomachine adjacent to the stator, and a first portion (121) that is bent with respect to the main portion (120), the first bent portion (121) being in contact with an outer face of at least one platform, each blade (12) being held against the at least one platform by a clamping means (40) that is configured to clamp the first bent portion (121) between the outer face of the platform and the clamping means (40).

Description

Improved turbomachine distributor

FIELD OF THE INVENTION

The present invention relates to the field of aeronautical turbomachines, and more precisely a distributor for a turbomachine turbine, and a turbomachine comprising such a distributor.

STATE OF THE PRIOR ART

The high pressure or low pressure distributors of turbomachinery, as described in document FR 2 955 145, include in particular fixed blades held at each of their radial ends by an inner platform and an outer platform, the latter defining a vein circulation of gases ejected from the combustion chamber. These blades make it possible to direct the flow of gases leaving the combustion chamber on the rotor blades of the turbine. These blades are hollow, and have at least one cavity, one end of which opens to the outside of the vein. These blades being exposed to hot combustion gases, it is necessary to cool them to reduce thermal stresses. One solution is to use air from another element of the turbomachine, for example the compressor. More specifically, relatively fresh air is taken upstream of the combustion chamber at the outlet of a stage of the compressor. This air is injected into the cavity (ies) of the blades through one and the other of the ends thereof, to cool them from the inside. The air then escapes into the vein through holes made in the blades and communicating with the cavity (ies) of the blade and with the vein, the cooling air creating a protective film of cooler air s 'flowing along the blade.

In addition, the inner and outer blades / platforms assembly is fixed to the turbine casing. Sealing strips and joint covers are fixed at the platforms by fixing means (pins / rivets), in order to ensure sealing between the distributor and the external casing.

However, it may happen that during flight, mechanical stresses such as shear stresses between pins / rivets and sealing strips or joint covers cause the loss of these sealing strips and joint covers. These can then be released and sucked up by the distributor. In particular, the cooling air entering the cavities of the blade can entrain these sealing strips and joint covers towards these cavities. The sealing strips and the joint covers are then capable of partially or completely closing these cavities. The cooling of the blades is then no longer or insufficiently ensured. The temperature of the blades may then increase, which could lead to deterioration of the properties of the blades.

There is therefore a need for a device for solving the above technical problem.

PRESENTATION OF THE INVENTION

The present disclosure relates to a turbine distributor for a turbomachine extending radially around an axis, the distributor comprising a plurality of sectors each comprising at least one blade which extends radially between an inner platform and an outer platform , the distributor comprising at least two sealing strips each comprising a main portion configured to seal between the distributor and an element of the turbomachine adjacent to the distributor, and a first portion folded relative to the main portion, the first portion folded being in contact with an outer face of at least one platform, each strip being held on the at least one platform by a clamping means configured to clamp the first folded portion between the outer face of the platform and the clamping means.

In the present description, the term "radial" and its derivatives denote a radial direction of the turbine, that is to say a direction perpendicular to the axis of the turbine. In addition, the terms “upstream” and “downstream” are considered along the axis of the turbine, and according to the direction of flow of the gases in the turbine, between the two platforms, that is to say in the vein gas circulation. Furthermore, the blades are arranged between two platforms: a radially outer platform, and a radially inner platform, the inner and outer platforms being annular or in the form of a ring sector and coaxial. In addition, the “external face” of the platforms designates the face of the platforms opposite the vein gas flow, the latter being delimited by the internal face of the platforms. In other words, the gas flow stream is delimited by the internal face of the external platform, and the internal face of the internal platform.

The sealing strips can have the form of a metal plate, for example made of an alloy based on nickel and / or cobalt, and having a thickness of less than 1 mm.

The plate forming a sealing strip is folded, so as to form a first folded portion, and a main portion having a larger area than the folded portion.

The main portion of the strips is the portion of the strip having the largest surface, and extends on the one hand in a direction substantially parallel to the radial direction, or slightly inclined relative to the radial direction, and d on the other hand in a circumferential direction, following the shape of the distributor, so that the main portion has the shape of an arc of a circle.

The main portion of the blades is in contact with an element of at least one sector of the turbomachine, for example a shoulder of the sector disposed at an upstream or downstream end of the platform, and with an element of the turbomachine adjacent to the distributor. This element of the turbomachine may for example be a part of an adjacent casing, or a flange of the combustion chamber.

The folded portion extends in the axial direction, that is to say from upstream to downstream, and is in contact with the external face of the platform. The folded portion is held and clamped against the external face of the platform by means of the clamping means. The latter is configured to hold and tighten the folded portion of each lamella over the entire circumference of the dispenser, by exerting pressure on the lamellae in the radial direction, so that the folded portions are sandwiched between the clamping means and the external faces of the platforms. More specifically, the clamping means exerts a force on the blades directed radially towards the axis of the turbine when the blades are arranged on the external platform, and directed radially towards the direction opposite to the axis of the turbine when the blades are arranged on the interior platform. Consequently, according to the present description, the fixing of the sealing strips to the distributor is ensured by the first folded parts and the fixing means, and the sealing between the distributor and the elements of the turbomachine adjacent to the distributor is provided by the main portion. The use of pins and / or rivets usually making it possible to fix the strips on the distributor, for example on the shoulder of the sector disposed at an upstream and / or downstream end of the platform, is therefore no longer necessary. The risk of loss of the lamellae due to shearing of the rivets is therefore reduced. Consequently, the risk of deterioration of the blades, due to obstruction of the cooling cavities by the lamellae, is also reduced.

In some embodiments, the dispenser comprises two strips each forming a half-ring, the clamping means being arranged around the dispenser so as to clamp the two strips against the outer faces of the platforms of the dispenser.

According to this configuration, each strip has a shape of an arc of a circle of 180 °. When several sectors are assembled so as to form the distributor crown, each of the two 180 ° strips is fixed on the external face of the adjacent platforms of the distributor crown, and are held and clamped against these external faces by the clamping means , the latter surrounding the dispenser over its entire circumference and thus maintains the two strips simultaneously. The circumferential ends of the two strips are joined to each other so as to form a sealing ring which extends around the dispenser. The use of two strips makes it possible to limit the number of parts required, to limit inter-sector leaks and to simplify the assembly process.

In some embodiments, the main portion and the first folded portion of each strip form between them an angle between 90 ° and 150 °.

We understand that this angle between the main portion and the first folded portion of each strip is the natural angle formed by these two portions of the strip, that is to say when no effort tending to deform the strip , and therefore to modify this angle, is only exerted on the strip. According to this configuration, the plate forming the strip is not folded so as to form a right angle between the portion main and the folded portion, but so as to form an obtuse angle between the latter. In other words, when the strip is fixed to a distributor, the plane in which the main portion of the strip extends is not parallel with respect to the radial direction, but slightly inclined with respect to the latter. This configuration improves the seal between the distributor and the element of the turbomachine adjacent to the distributor. Indeed, due to the inclination of the main portion, the element of the turbomachine adjacent to the distributor comes into contact with the radial end of the main portion. This contact tends to deform the strip so as to reduce the angle between the main portion and the folded portion. The main portion, tending to return to its initial position by elasticity, thus acts as a spring by exerting pressure on the element of the turbomachine adjacent to the distributor. In other words, the contact pressure between the main portion of the strip and the element of the turbomachine adjacent to the distributor is increased, thereby improving the seal between this element and the distributor.

In some embodiments, the slats each have a second folded portion extending from the first folded portion, substantially perpendicular thereto, and coming into contact with a radial wall which extends radially projecting from the '' at least one platform.

According to this configuration, the strips are folded so as to have three portions: the main portion, the first folded portion in contact with the external face of the platform, and the second folded portion, the first folded portion being interposed between the main portion and the second portion folded, so that, in a cross section, the strip has substantially the shape of a U.

The presence of the second folded portion makes it possible to limit the movements of the clamping means in the axial direction. More specifically, the thus folded strip takes the form of a gutter in which is housed the clamping means, thus limiting its axial movements, and limiting the risks that sufficient clamping of the strip against the platform is no longer ensured. By sufficient tightening, it is understood to be a tightening making it possible to prevent the strip from coming loose during normal operation of the turbomachine. In some embodiments, two circumferentially adjacent strips around the dispenser are arranged so that a circumferential end of the main portion of a strip is superimposed on a circumferential end of the main portion of a circumferentially strip adjacent.

In some embodiments, the circumferential end of the main portion of a strip and the circumferential end of the main portion of the adjacent strip overlap over a distance between 1 and 10 mm.

In other words, the dimensions of each strip are provided so that the circumferential ends thereof overlap each other, over their entire height. We understand by height their length in the radial direction. For example, when the distributor has two 180 ° strips each forming a half-ring, the circumference of one of the two strips is substantially larger than the other, so as to overlap the ends of the latter.

This configuration avoids the presence of a play between the circumferential ends of each strip, and therefore improves the seal between the distributor and an element of the turbomachine adjacent to the distributor.

In some embodiments, the clamping means comprises at least one clamping surface, the clamping surface being in contact with the first folded portion.

The presence of at least one flat clamping surface makes it possible to obtain a planar contact between the clamping means and the first folded portion, increasing the contact surface, and therefore the reliability of clamping the strip on the platform. .

In some embodiments, the clamping means is a rod.

By ring means a ring, preferably metallic, having two free ends opposite but disjoint from each other. This device has the advantage of being simple and inexpensive. In some embodiments, the dispenser comprises at least one blade fixed to the radial wall, and configured to exert pressure on a strip.

The blade is fixed to the radial wall, and is oriented so as to bear on a lamella of the dispenser, thus exerting pressure thereon. This makes it possible to exert pressure against the main portions of the lamellae, and thus increase the contact pressure between the main portions and the element of the turbomachine axially adjacent to the distributor, thus further improving the seal.

The present disclosure also relates to a turbomachine comprising a distributor according to any one of the preceding embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention given by way of non-limiting examples. This description refers to the pages of attached figures, on which:

- Figure 1 shows a partial perspective view of a turbine distributor for a turbomachine according to the prior art;

- Figure 2 shows a partial perspective view of a turbine distributor for a turbomachine according to the prior art, when an orifice is closed;

- Figure 3 shows a partial perspective view of a turbine distributor for a turbomachine according to the present description;

- Figure 4 shows a perspective view of the junction between two strips according to the present description;

- Figure 5 shows a section of the end of a platform of a distributor according to the present description.

- Figure 6 shows a partial top view of one end of a platform according to the present description.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENT

FIG. 1 represents a sector 10 of a distributor for a high pressure turbine of a turbomachine according to the prior art, the distributor comprising a ring of fixed hollow blades 13, arranged between two coaxial annular platforms: an external platform 16 and an indoor platform 18. The platforms are formed by ring sectors which extend around the axis X and which delimit a gas circulation stream 20 in which the blades 13 are distributed regularly distributed circumferentially and which extend radially between the platforms 16, 18 Each blade has a cavity 26 opening to the outside of the vein 20 through the external platform 16. Likewise, each blade has a cavity (not shown) opening to the outside of the vein through the internal platform 18. These cavities communicate with the vein 20 by rows of holes 30 extending axially and / or radially between the inner platform 18 and the outer platform 16 along the blades 13 to open into the vein 20. A gas flowing from the exterior of the vein 20 can thus penetrate into the cavity 26, flow into the blade 13, then be evacuated into the vein 20 via the orifices 30, thus allowing the blade cooling 13.

In the following description, the description is made with reference to the external platform 16, in particular in the figures. However, a similar description is applicable to the interior platform 18.

A jacket 36 is inserted into the cavity 26, so as to define an orifice 37 on the external face of the platform 16. By "external" is understood the face of the platform opposite the vein 20. The shirt 36 further comprises a flange 38 bearing on the external face of the platform 16. A jacket (not shown) is also inserted in the cavity on the side of the internal platform 18, so as to define an orifice on the external face of the platform interior 18.

The distributor sector 10 also includes sealing strips 12 fixed to the platforms 16, 18, and making it possible to ensure sealing between the distributor and an element of the turbomachine 1 axially adjacent to the distributor. More specifically, the sealing strips 12 are fixed on shoulders 161, 162 of the platform 16, by means of pins and / or rivets 14.

Figure 2 illustrates a configuration that the invention seeks to prevent and according to which, after the detachment of a strip 12 from its location for attachment to the high pressure distributor due to the shear stresses between the rivets 14 and the strip 12, the latter is sucked in by the air entering the cavity 26, and obstructs the orifice 37, thus preventing the air, partially or totally, from entering the cavity 26.

3 shows a sector 10 of a high pressure turbine distributor for a turbomachine according to one embodiment of the invention. The elements identical to the elements of Figures 1 and 2 have the same reference signs and will not be described again. A portion of a strip 12 is illustrated in FIG. 3. However, a dispenser according to the present embodiment, comprising a plurality of sectors 10 assembled to each other, may comprise two semi-annular strips 12 extending over 180 °, so that the latter surround the crown of the dispenser when they are assembled to one another. Unlike the sector described with reference to FIGS. 1 and 2, the sector 10 described below does not have rivets 14 for fixing the strips 12 to the shoulders of the platform.

According to this embodiment, each strip 12 has a main portion 120, a first folded portion 121, and a second folded portion 122. To do this, before fixing the strip to the dispenser, the strip 12 is folded in a first step in half so as to obtain the main portion 120 and the first folded portion 121, and so that the main portion 120 and the first folded portion 121 have an angle between them substantially greater than 90 °. More specifically, the main portion 120 and the first folded portion 121 have an angle of 90 ° + a between them, where a is less than 60 °, preferably less than 20 °. The strip 12 is folded again so as to obtain the second folded portion 122, the first folded portion 121 and the second folded portion 122 being substantially perpendicular to one another. The strip 12 thus formed thus has substantially the shape of a U, in section in a transverse section plane which extends axially and radially, so as to form a groove or a gutter around the crown of the distributor when the strips are fixed on the distributor's platforms, thus making it possible, when a clamping element is housed in this groove, to limit the axial displacements of the latter. The axial displacements of the element of clamping and slats are also limited by a radial wall 163 which extends radially projecting from the platform.

In the same way as the strip 12 according to the prior art, the main portion 120 makes it possible to seal between the distributor and the element of the turbomachine 1 axially adjacent to the distributor, for example a flange of the combustion chamber or part of an axially adjacent casing, being in contact with a shoulder 161 of the platform 16 and the element of the turbomachine 1 adjacent to the distributor. In fact, when the strip 12 is fixed to the distributor, and by the inclination of its main portion 120, the element of the turbomachine 1 axially adjacent to the distributor comes into contact with the radial end of the main portion 120 during assembly or during operation of the turbomachine. This contact generates a force on the radial end of the main portion 120, tending to reduce the angle between the main portion 120 and the folded portion 121. The main portion 120, tending to return to its initial position by elasticity, thus acts as a spring by exerting pressure on the element of the turbomachine 1 axially adjacent to the distributor. The value of the angle a is determined so that, when the distributor is assembled to the turbomachine, and during normal operation of the latter, contact always exists between the main portion 120 of the strip 12 and the element of the turbomachine 1 axially adjacent to the distributor.

6 shows a partial view from above, that is to say in the radial direction, of an upstream end of a platform 16. Blades, or pins 170, used to exert pressure on joint covers in order to maintain the latter at the junctions between two circumferentially adjacent strips 12 can be used in order to exert pressure against the main portions 120 of the strips 12 via a contact portion 171, and thus accentuate the contact pressure between the main portions 120 and the element of the turbomachine 1, thus further improving the sealing. These pins are fixed to a radial wall 163 by means of a rivet 164. It is noted that the rivets 164 serving to fix these pins 170 to the dispenser, are not in contact with the strips 12, which limits damage by shearing of the strips 12.

In addition, the first folded portion 121 is pressed against the outer face of the platform 16 by a clamping means 40, the latter being configured to exert pressure in the radial direction on the first folded portion 121, the latter being thus sandwiched between the clamping means 40 and the platform 16. According to this embodiment, the clamping means 40 is a rod, allowing the two strips 12 to be clamped simultaneously by 180 ° against the external face of the distributor platforms, the rod coming to lodge in the groove formed by the main portion 120, the first folded portion 121 and the second folded portion 122.

The rod is an open ring, preferably metallic, for example an alloy based on nickel and / or cobalt, having two free ends circumferentially opposite, but separated from each other . The rod has an initial diameter D ₀ . When these two free ends are distant from each other, using a clamp for example, the metal rod is elastically deformed so that its diameter increases, allowing the latter to be placed around the dispenser, while keeping the ends away from each other. When the rod is in the desired position, in the groove formed by the strips 12, its free ends are released. The rod then tends to regain its initial shape, until it comes into abutment against the first folded portion 121, thus reaching its final diameter D _f , when it clamps the strips 12 against the external face of the external platforms 16 So that the force exerted by the clamping means 40 on the first folded portion 121 is sufficient, that is to say that it ensures a clamping making it possible to prevent the strip from coming off, the initial diameter D ₀ of the rod must therefore be less than the final diameter D _f .

This example shows the clamping of a strip 12 on the external face of an external platform 16. However, the clamping means 40 can also be used to clamp a strip 12 on the external face of an internal platform 18 In this case, unlike the case described in the previous paragraph, the rod is deformed by bringing the free ends thereof, causing these ends to overlap, so that the diameter of the rod decreases. When the rod is in the desired position, in the groove formed by the lamellae 12, the deformed position of the rod is then released. The diameter of the rod then tends to increase again to regain its initial shape, until it comes into abutment against the first folded portion 121, thus reaching its final diameter Df when it clamps the strips 12 against the external face. interior platforms 18. So that the force exerted by the clamping means 40 on the first folded portion 121 is sufficient, that is to say that it ensures a clamping making it possible to prevent the strip from coming off, the initial diameter D ₀ of the rod must therefore be greater than the final diameter Df.

Although in the embodiment described above, the clamping means 40 is a rod, other clamping means can be envisaged, such as circlips, clamps or rings comprising for example a first portion and a second portion, the first and second portions being fixed together around the distributor so as to clamp the strips against the external faces of the platforms of the distributor.

Furthermore, the main portions 120 of each strip 12 have a circumferential end 120a, said circumferential end 120a extending in the radial direction. The dimensions of the strips 12 are configured such that the circumferential ends 120a of two circumferentially adjacent strips overlap, so as to form an overlapping portion 125. This overlapping portion 125 makes it possible to seal the junction between two strips 12 circumferentially adjacent. The dimensions of the strips 12 are configured so that the overlapping portion 125 extend over an angle between 1 and 10 °. The overlapping portion can also be formed by stamping a circumferential end of a strip 12, thus creating a recess on one face of the main portion 120, at the circumferential end of this strip 12, the circumferential end of the adjacent strip then coming to lodge in this disbursement (cf. Figure 4).

In addition, for each strip 12, the length along the circumference (in other words the length of the arc of a circle) of the first folded portion 121 and the second folded portion 122, is substantially less than the length according to the circumference of the portion main 120. Thus, only the circumferential ends of the main portions 120 overlap. The circumferential ends of the first folded portion 121 and of the second folded portion 122 of two circumferentially adjacent strips 12 are separated from each other. This configuration makes it easier to assemble the strips 12 around the distributor, and in particular the junction of two adjacent strips 12.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the revendications. In particular, individual features of the various illustrated / mentioned embodiments can be combined in additional embodiments. Therefore, the description and the drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

1. Distributor for a turbomachine turbine extending around an axis (X), the distributor comprising a plurality of sectors (10) each comprising at least one blade (13) which extends radially between an internal platform (18 ) and an external platform (16), the distributor comprising at least two sealing strips (12) each comprising a main portion (120) configured to seal between the distributor and an element (1) of the turbomachine adjacent to the distributor, and a first folded portion (121) relative to the main portion (120), the first folded portion (121) being in contact with an external face of at least one platform (16, 18), each strip (12 ) being held at the at least one platform (16, 18) by a clamping means (40) configured to clamp the first folded portion (121) between the external face of the platform (16, 18) and the clamping means ( 40).

2. Distributor according to claim 1, comprising two strips (12) each forming a half-ring, the clamping means (40) being arranged around the distributor so as to clamp the two strips (12) against the external faces of the platforms ( 16, 18) of the dispenser. 3. Dispenser according to claim 1 or 2, wherein the main portion (120) and the first folded portion (121) of each strip (12) form between them an angle between 90 ° and 150 °. 4. Dispenser according to any one of claims 1 to 3, in which the lamellae (12) each comprise a second folded portion (122) extending from the first folded portion (121), substantially perpendicular thereto, and coming into contact with a radial wall (163) which extends radially projecting from the at least one platform (16, 18).

5. Dispenser according to any one of claims 1 to 4, comprising two strips (12) circumferentially adjacent around the distributor arranged so that a circumferential end (120a) of the main portion (120) of a strip ( 12) is superimposed on a circumferential end (120a) of the main portion (120) of the adjacent strip (12).

6. The dispenser of claim 5, wherein the circumferential end (120a) of the main portion (120) of a lamella (12) and the circumferential end (120a) of the main portion

(120) of the adjacent strip (12) overlap over a distance of between 1 and 10 mm.

7. Dispenser according to any one of claims 1 to 6, in which the clamping means (40) comprises at least one clamping surface, the clamping surface being in contact with the first folded portion (121).

8. A dispenser according to any one of claims 1 to 7, wherein the clamping means (40) is a rod.

9. A dispenser according to any one of claims 4 to 8, comprising at least one blade (170) fixed to the radial wall (163), and configured to exert pressure on a strip (12).

10.Turbomachine comprising a distributor according to any one of the preceding claims.