EP3351736B1 - Internal ferrule of an axial turbine-engine compressor - Google Patents

Description

Technical area

The field of the present invention is that of axial turbomachines. More particularly, the invention addresses the internal ferrules connected to a row of stator vanes.

Prior art

An internal ferrule is known for making it possible to delimit the primary flow of an axial turbomachine, it forms an annular wall which delimits the interior of the fluid stream. Thanks to its external surface, it helps guide the flow during its expansion in a turbine, or its compression in a compressor.

Conventionally, an internal ferrule can be mounted on the internal ends of vanes arranged in an annular row, themselves linked to an external casing. The ferrule has recesses for the introduction of the ferrule fixing ends.

The internal ferrule is also intended to ensure a seal with the rotor around which it is placed. To this end, it has a layer of abradable material cooperating by abrasion with wipers formed outside the rotor. In operation, the wipers come close to the abradable, possibly creating circular notches there, so that a dynamic seal is ensured.

The document EP 2,075,414 A1 discloses an axial turbomachine compressor comprising rectifiers provided with segmented internal ferrules. Each internal ferrule comprises a tubular wall in which are provided rows of openings. These allow the introduction of the blade roots used for fixing between the ferrule and the blades. Each opening has a lip which extends radially around it, ribs join the lips of the neighboring openings, the assembly making it possible to stiffen the ferrule. However, the bending stiffness of the shell; in particular of its segments remains limited. In the event of stress, the main efforts are taken up by the branches of the U shape of the ferrule. In the event of vibrations, the openings can open further around the seals surrounding the blades, which degrades the seal.

The document EP1419849A1 discloses a method of repairing a turbine segment. The segment comprises a pair of blades, the ends of which are linked to an internal ferrule. The latter has two openings linked to the blades, the opposite edges of the openings being joined by a flange.

Summary of the invention Technical problem

The invention aims to solve at least one of the problems posed by the prior art. More specifically, the invention aims to improve the sealing of a ferrule or a segment of a ferrule. The invention also aims to improve the rigidity of an assembly comprising a ferrule and vanes linked in openings formed in the ferrule. Another object of the invention is to stiffen an internal ferrule or an internal ferrule segment linked to stator vanes.

Technical solution

The subject of the invention is a turbomachine comprising a rotor and an internal ferrule around the rotor or an internal ferrule segment matching the rotor, the ferrule or the ferrule segment comprising a circular or semi-circular wall whose profile mainly extends axially, and a circular or semi-circular radial flange extend radially from the wall towards the inside, the flange having a circular or semi-circular surface whose profile extends mainly radially, said surface having asperities. The rotor has annular ribs cooperating sealingly with the ferrule or the ferrule segment, the annular ribs of the rotor are each axially spaced from each radial flange of the ferrule or the ferrule segment. Furthermore, at least one or each radial flange comprises asperities which are formed over the majority of the radial height of the profile of revolution of one of the annular ribs of the rotor disposed opposite the associated radial flange.

According to an advantageous embodiment of the invention, at least one or each radial flange comprises at least one surface with asperities, said surface being generally perpendicular to the axis of revolution of the ferrule or of the ferrule segment.

According to an advantageous embodiment of the invention, the asperities form a pattern repeated on substantially an entire face of the corresponding radial flange.

Other aspects of the invention are indicated in claims 4 to 9.

Benefits

The radial flange makes it possible to form a bridge which spans each opening. The flange thus makes it possible to link the opposite edges of the openings so as to connect the edges. This mechanical seal makes it possible to link the opposite edges through each opening, so as to prevent them from moving apart or approaching despite the material vacuum of the openings.

In parallel, the invention makes it possible to improve the seal between a ferrule or a segment of a ferrule with openings in which stator vanes are fixed. The invention thus provides a ferrule or a segment of ferrule which is both light, rigid, and economical to produce.

Brief description of the drawings

• The figure 1 represents an axial turbomachine according to the invention.
• The figure 2 is a diagram of a turbomachine compressor according to the invention.
• The figure 3 illustrates a portion of compressor according to the invention.
• The figure 4 sketch a section of the compressor portion along axis 4-4 traced on the figure 3 according to the invention.
• The figure 5 sketch a section of the compressor portion along axis 5-5 plotted on the figure 3 according to the invention.
• The figure 6 is a diagram of the method of assembling a stator vane to an internal ferrule or to an internal ferrule segment according to the invention.

Description of the embodiments

In the following description, the terms internal or internal and external or external refer to a positioning relative to the axis of rotation of an axial turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The lateral direction is according to the circumference.

The figure 1 represents in a simplified manner an axial turbomachine. In this specific case, it is a double-flow turbojet engine. The turbojet engine 2 comprises a first level of compression, called a low-pressure compressor 5, a second level of compression, called a high-pressure compressor 6, a combustion chamber 8 and one or more levels of turbines 10. In operation, the mechanical power from the turbine 10 transmitted via the central shaft to the rotor 12 sets in motion the two compressors 5 and 6. The latter comprise several rows of rotor blades associated with rows of stator blades. The rotation of the rotor around its axis of rotation 14 thus makes it possible to generate an air flow and to compress it progressively until the inlet of the combustion chamber 8. Reduction means can increase the speed of rotation transmitted to the compressors.

An inlet fan commonly designated as a fan or blower 16 is coupled to the rotor 12 and generates an air flow which is divided into a primary flow 18 passing through the various above-mentioned levels of the turbomachine, and a secondary flow 20 passing through an annular duct (partially shown) along the machine to then join the primary flow at the outlet of the turbine. The secondary flow can be accelerated so as to generate a thrust reaction. The primary 18 and secondary 20 flows are annular flows, they are channeled by the casing of the turbomachine. For this purpose, the casing has cylindrical or ferrule walls which can be internal and external.

The figure 2 is a sectional view of a compressor of an axial turbomachine such as that of the figure 1 . The compressor can be a low-pressure compressor 5. The rotor 12 comprises a drum with an external annular wall which supports several rows of rotor blades 24, in this case three rows.

The low-pressure compressor 5 comprises several rectifiers, in this case four, which each contain a row of stator vanes 26. The rectifiers are associated with the fan or with a row of rotor vanes to straighten the air flow, so as to convert the velocity of the flow into static pressure.

The stator vanes 26 extend essentially radially from an external casing 22, and can be fixed to it using a pin. The casing 22 then forms an external support for the different rows. The compressor 5 also includes internal ferrules 28 which are fixed to the radially internal ends of the stator vanes 26. The internal ferrules 28 make it possible to guide and delimit the primary flow 18. They also provide a seal with the rotor 12 to avoid recirculation d air reducing the compression ratio of the compressor 5, and limiting the efficiency of the turbomachine. Each ferrule 28 can form a ring of a turn, or be segmented angularly.

The figure 3 represents a portion of the compressor such as that of the figure 2 . There is visible a portion of the rotor 12, an internal radial end 30 of the stator vane 26, and an internal ferrule 28 which is fixed to it. The internal ferrule 28 could be segmented.

The ferrule 28 has a profile of revolution with a portion extending mainly axially and which generates an axial wall 32. The axial wall 32 may be generally tubular, and be substantially inclined relative to the axis of rotation 14 of the turbomachine; the latter may coincide with the general axis of symmetry 14 of the shell 28.

The ferrule 28 has a series of openings 34 arranged in an annular row. These openings 34 are crossed by the ends 30 of the vanes 26 to suspend the ferrule 28 there. Each opening 34 has opposite edges 36 in the direction of the row of openings 34, these edges 36 being placed opposite the faces of the associated dawn 26. One is facing the lower surface of the dawn, the other facing the upper surface. The edges 36 can generally be conjugates; one is concave, the other convex.

The ferrule 28 further comprises at least one radial flange 38 which extends radially inwards from the axial wall 32. The ferrule 28 may comprise several radial flanges 38 which each cut the openings 34. These radial flanges may be parallel, and distributed axially through the openings.

The ferrule 28 may comprise at least three radial flanges, including an upstream radial flange 40, a downstream radial flange 42, and a through radial flange 38 which passes through the openings 34, or central radial flange 38. The through radial flange 38 is disposed axially between the upstream 40 and downstream 42 flanges. The ferrule may have an “E” or comb profile.

The rotor 12, in particular its wall has annular ribs 44, also called "wipers". They extend radially and cooperate with the shell 28 in a sealed manner. They can cooperate by abrasion with layers of abradable material 46 where they dig grooves in the event of contact. By abradable material is meant a friable material in the event of contact. The abradable layers 46 can be applied to the ends of the blades 30, and / or to the axial wall 32. The abradable layers 46 and the radial flanges (38; 40; 42) form an alternation.

The radial flanges (38; 40; 42) can be combined in pairs to frame each annular rib 44 of rotor 12, possibly individually. Each radial flange (38; 40; 42) comprises a profile of revolution which extends essentially radially, each flange profile extends over the majority of the radial height of each profile of the flange neighboring radial. Each rib profile (38; 40; 42) extends over the majority of the radial height of the profiles of the adjacent annular ribs 44.

To improve the dynamic sealing of the turbomachine, the faces of radial flanges (38; 40; 42) facing annular ribs 44 are covered with roughness 48 which amplifies turbulence 50, or vortices 50 opposing recirculations 52.

The figure 4 represents a section of the ferrule 28 and the stator vanes 26 along the axis 4-4 traced on the figure 3 . The cutting plane passes through the radial flange 38 which crosses the openings 34. The ferrule could be formed by segments of ferrule which would be placed end to end so as to form a circle.

The blades 26 extend radially from the ferrule 28 and pass through the openings 34. Their radial ends 30 are in radial abutment against the radial flange 38. Each blade end 30 has a radial abutment surface which cooperates with a abutment surface niche correspondent. Seals 54 extend radially into the openings 34 and pass through them, they come into contact with the radial flange 38. The bottoms of notches, or abutment surfaces of the notches, are spaced from the seals 54 and / or the axial wall.

The radial flange 38 not only joins all the openings 34, but also connects all the opposite edges 36 to each other by crossing the openings 34. It forms a reinforcing bar which, in each opening 34, blocks the opposite edges 36 The radial flange 38 has an arcuate shape and a notched profile. It comprises a series of steps forming notches 56 in which the ends 30 of the blades 30 are placed. These notches 56 can be a place for fixing the blades 26, for example by gluing or using fixing plates (not shown). To this end, the ends 30 may include fixing orifices (not shown). Within each opening 34, the radial flange 38 links the opposite edges 36. This configuration stiffens the ferrule 28, and prevents it from bending at the openings, 38 so that the risk of detachment at the joints 54 is reduced.

The figure 5 represents a section along axis 5-5 drawn on the figure 3 . The section shows a compressor section between the rotor 12 and an internal shroud, seen from the outside. The location of the blade ends 30 is shown.

The asperities 48 comprise grooves and ridges alternating with the grooves, They extend radially and are optionally perpendicular to the axis of rotation of the turbomachine. The assembly can form a striated annular surface. The asperities 48 may have triangular tooth shapes, and have a general sawtooth profile.

The asperities 48 are formed opposite the wipers 44, preferably on each side. The pattern can be formed along, along the circumference, radial flanges (38; 40; 42); or all around. Thanks to the asperities 48, the radial flanges (38; 40; 42) cause vortices 50 in the air entrained by the rotor 12

The figure 6 shows a diagram of a method of assembling a stator vane on a ferrule, the ferrule being able to be segmented.

1. (a) fourniture d'une ou plusieurs aubes statoriques 100, chaque aube statorique comportant une extrémité radiale interne, optionnellement avec des moyens de fixation ;
2. (b) fourniture d'une virole interne ou d'un segment de virole interne 102 comprenant une rangée d'ouvertures et une bride radiale circulaire ou semi-circulaire traversant les ouvertures en les franchissant de bord à bord ;
3. (c) positionnement 104 de chaque extrémité d'aube statorique dans une ouverture en mettant en butée chaque extrémité d'aube contre la bride radiale ;
4. (d) fixation 106 de chaque extrémité d'aube dans l'ouverture associée ;
5. (e) mise en œuvre ou réalisation 108 de joints d'étanchéité dans les ouvertures autour des aubes statoriques, de sorte à permettre une étanchéité entre la virole et les aubes statoriques.

The process can include the following stages, possibly carried out in the order presented below:

1. (a) supply of one or more stator vanes 100, each stator vane having an internal radial end, optionally with fixing means;
2. (b) providing an internal ferrule or an internal ferrule segment 102 comprising a row of openings and a circular or semicircular radial flange passing through the openings crossing them from edge to edge;
3. (c) positioning 104 of each end of the stator vane in an opening by abutting each end of the vane against the radial flange;
4. (d) fixing 106 of each blade tip in the associated opening;
5. (E) implementation or realization 108 of seals in the openings around the stator vanes, so as to allow a seal between the ferrule and the stator vanes.

Step (b) supply 102, can comprise additive manufacturing of the shell or of the shell segment. The ferrule or each segment may have come from a mantle and be made of polymer, for example a composite martial material with fibers, possibly of length less than 10 mm.

Positioning step (c) 104 can be carried out by fixing the blades to an external compressor casing. Then the ferrule is brought together radially so that the internal ends of the blades are found in the openings. Initially, the blade tips enter the openings, then pass through them. Finally, these ends abut against a radial flange. The stop is then axial and / or radial, which makes it possible to improve the relative position between the blade and the shell. Thus, the joint produced or implemented during step (e) implementation or production 108 is better positioned and / or better produced.

Claims (9)

1. Turbomachine (2) comprising a rotor (12) and an internal shroud (28) around the rotor (12) or a segment of an internal shroud adopting the form of the rotor (12), the shroud (28) or the segment of a shroud comprising:

   - a circular or semi-circular wall (32), of which the profile extends essentially axially, and

   - at least one circular or semi-circular radial flange (38, 40, 42) extending radially from the interior of the wall (32)
   characterized in that
   the or each flange (38, 40, 42) has at least one circular or semi-circular surface, the profile of which extends substantially radially, said surface having areas of roughness (48),
   in that the rotor (12) comprises annular ribs (44) interacting in a sealed manner with the shroud (28) or the segment of a shroud, the annular ribs (44) of the rotor (12) each being located at a distance axially from each radial flange (38; 40; 42) of the shroud (28) or of the segment of a shroud,
   and in that the areas of roughness (48) are formed on more than half of the radial height of the profile of one of the annular ribs (44) of the rotor (12) facing the associated radial flange (38; 40; 42).
2. Turbomachine (2) according to claim 1, characterized in that said surface of the flange (38; 40; 42) with areas of roughness (48) is generally perpendicular to the axis of revolution of the shroud (28) or of the segment of a shroud.
3. Turbomachine (2) according to claim 1 or 2, characterized in that said areas of roughness (48) form a pattern that is repeated on substantially the entire face of the corresponding radial flange (38; 40; 42).
4. Turbomachine (2) according to any of claims 1 to 3, characterized in that the areas of roughness (48) comprises furrows and ridges, said ridges alternating with furrows and extending radially.
5. Turbomachine (2) according to claim 4, characterized in that the furrows and the ridges are perpendicular to the axis of revolution (14) of the turbomachine (2).
6. Turbomachine (2) according to any of claims 4 or 5, characterized in that the entirety of the furrows and ridges forms a annular and serrated surface.
7. Turbomachine (2) according to any of claims 1 to 3, characterized in that the areas of roughness (48) exhibit the form of teeth, possibly triangular, each tooth extending over more than half of, or all of, the radial height of the associated radial flange (38; 40; 42).
8. Turbomachine (2) according to any of claims 1 to 7, characterized in that the areas of roughness (48) are formed opposite the annular ribs (44), preferably on each side.
9. Turbomachine (2) according to any of claims 1 to 8, characterized in that the pattern of the areas of roughness (48) is formed circumferentially over the entirety of the radial flanges (38; 40; 42); or on the entire circle of flanges (38; 40; 42).

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