EP2400160B1 - Lightened rotor of axial compressor - Google Patents

Description

Object of the invention

The present invention relates, in the field of turbomachines, to a compressor rotor consisting of a drum and blades mechanically fixed thereon.

State of the art

Axial compressors are well known per se and are used inter alia in turbomachines.

These low or high pressure compressors comprise several stages of rotating blades, also called rotor blades, which are separated by rectifier stages which are intended to reposition the velocity vector of the fluid leaving the preceding stage before sending it to the next floor.

The rectifier stages consist essentially of fixed vanes, also called stator vanes, connecting an outer ferrule to an inner ferrule, both concentric and delimiting the air flow zone or aerodynamic vein.

The rotor blade stages are attached to a drum. In general, a compressor drum is a symmetrical hollow body in revolution with respect to its axis of rotation which corresponds to the axis of the turbomachine. The hollow body has a generally oval or ogival shape depending on the shape of the flow.

Nowadays, the drum and the rotor blades are generally made of a titanium alloy (TA6V) and the drum has circumferential cavities in which the blade roots are fixed via a system of locks. Such a construction is illustrated in figure 1 of the document EP 1 111 246 B1 .

• pour éviter l'ouverture des alvéoles et ainsi garantir la tenue des aubes et la stabilité des pieds au sein des alvéoles, ces dernières doivent appartenir à des zones massives des tambours;
• les pieds des aubes qui viennent se loger dans ces alvéoles sont également massifs (40 à 50% de la masse de l'aube); il en résulte une masse centrifugée importante induisant des contraintes dans le tambour d'autant plus importantes;
• la présence d'alvéoles induit des concentrations de contraintes au bord des encoches d'introduction. I1 en résulte qu'un design classique avec alvéoles embarque une quantité importante de matière dont seule une portion relativement réduite est « utile » pour la tenue mécanique;
• les pieds des aubes ont une latitude de positionnement au sein des alvéoles engendrant notamment des phénomènes d'oscillation (rocking en anglais), consommateur de jeux axiaux et radiaux.

The classical architectures with cells, however, have several drawbacks that can be enumerated as follows:

• to prevent the opening of the cells and thus ensure the holding of the blades and the stability of the feet within the cells, they must belong to massive areas of the drums;
• the feet of the blades that are housed in these cells are also massive (40 to 50% of the mass of the dawn); this results in a large centrifugal mass inducing stresses in the drum all the more important;
• the presence of cavities induces stress concentrations at the edge of the insertion notches. As a result, a conventional design with cavities embeds a large amount of material of which only a relatively small portion is "useful" for mechanical strength;
• the feet of the blades have a positioning latitude within the cells generating in particular oscillation phenomena ( rocking in English), consumer of axial and radial games.

The document GB 1,163,752 presents an alternative to the fastening system with cavities in an axial flow machine rotor. The blade comprises a blade provided with a threaded member which engages in the rotor hub to allow the blade to be fixed to the hub.

Document is also known US 2,685,405 an axial compressor in which the rotor stage is provided with raised zones serving to support the rotor blades. These zones comprise an opening enclosing an intermediate portion of the blade, the platform of the blade being disposed within the support area.

Goals of the invention

The present invention aims to provide a solution that makes it possible to overcome the disadvantages of the state of the art.

The present invention is more particularly intended to provide a new drum architecture and an original attachment system of the blade to the latter.

The present invention also aims to provide a drum rid of its cells and thus aims to provide a new construction of the rotor to reduce consumption in radial and axial clearances.

The present invention also aims to achieve a new rotor construction for optimizing the choice of materials of different elements (drum, blade) and therefore a very consistent mass reduction.

Summary of the invention

The present invention relates to a rotor drum rotor compressor stage for axial turbomachine comprising a row of rotor blades each provided with a platform, and a generally symmetrical wall in revolution with respect to the axis of rotation of the rotor. the turbomachine and forming a hollow body, said wall comprising a web and a support area raised relative to the web in a direction facing outwardly of the hollow body, said support zone comprising a central portion and side walls connecting the central portion to web of the drum, said platform of each of said blades being assembled to said central portion by means of one or more fasteners.

• la partie centrale est munie, sur sa face extérieure au corps creux, d'un logement destiné à recevoir la plateforme de chacune desdites aubes rotoriques;
• ladite plateforme comporte au moins un élément de fixation et/ou comporte au moins un orifice permettant le passage de l'élément de fixation;
• la partie centrale comporte, sur sa face intérieure au corps creux, une aire de placement d'une pièce additionnelle, aussi appelée secteur;
• la partie centrale et le secteur comportent au moins un orifice permettant chacun le passage de l'élément de fixation;
• la partie centrale est reliée aux parois latérales par des bords arrondis, la crête des bords arrondis délimitant une veine aérodynamique, et les parois latérales sont reliées au voile du tambour par des tronçons arrondis;
• les parois latérales sont inclinées par rapport à une perpendiculaire à l'axe de rotation;
• l'aire de placement est disposée sur une partie saillante vers l'intérieur de la zone support;
• le secteur et l'aire de placement sont plans;
• le logement de la partie centrale est plan et coopère avec une surface plane de la plateforme de l'aube;
• la plateforme est de forme complémentaire à la partie centrale;
• l'élément de fixation est une attache boulonnée, un lockbolt ou un rivet;
• la tige de chaque attache boulonnée ou de chaque lockbolt ou rivet fait partie intégrante de la plateforme de l'aube rotorique;
• le secteur vient se placer en sandwich entre la partie centrale et un écrou de l'attache boulonnée ou entre la partie centrale et une bague du lockbolt ou entre la partie centrale et une partie déformée du rivet;
• les aubes rotoriques sont réalisées en aluminium MMC, pour Metal Matrix Composite, ou dans un alliage de titane et en ce que le tambour est réalisé dans un matériau métallique ou dans un matériau composite à matrice organique.

According to particular embodiments of the invention, the rotor stage comprises at least one or a suitable combination of the following characteristics:

• the central portion is provided on its outer face to the hollow body, a housing for receiving the platform of each of said rotor blades;
• said platform comprises at least one fixing element and / or comprises at least one orifice allowing passage of the fixing element;
• the central portion has, on its inner face to the hollow body, an additional part placement area, also called sector;
• the central portion and the sector comprise at least one orifice each allowing the passage of the fastener;
• the central part is connected to the side walls by rounded edges, the ridge of the rounded edges delimiting an aerodynamic stream, and the side walls are connected to the veil of the drum by rounded sections;
• the side walls are inclined with respect to a perpendicular to the axis of rotation;
• the placement area is disposed on a projecting portion towards the inside of the support area;
• sector and placement area are plans;
• the housing of the central portion is plane and cooperates with a flat surface of the platform of the blade;
• the platform is of complementary shape to the central part;
• the fastening element is a bolted fastener, a lockbolt or a rivet;
• the stem of each bolted fastener or each lockbolt or rivet is an integral part of the rotor blade platform;
• the sector is sandwiched between the central portion and a nut of the bolted fastener or between the central portion and a lockbolt ring or between the central portion and a deformed portion of the rivet;
• the rotor blades are made of MMC aluminum, for Metal Matrix Composite, or in a titanium alloy and in that the drum is made of a metallic material or an organic matrix composite material.

The present invention relates to a compressor drum for axial turbomachine comprising at least one rotor stage as described above.

Brief description of the figures

The figure 1 is a partial sectional view of a conventional axial compressor drum architecture superimposed on a partial sectional view of an axial compressor drum according to a preferred embodiment of the invention (gray profile).

The figure 2 represents a three-dimensional view of a preferred variant of the rotor blade according to the invention and the assembly nut.

The figure 3 represents a profile view of the attachment of the rotor blade of the figure 2 with the drum according to the preferred embodiment of the invention.

Legend:

1. Drum according to the state of the art
2. 2. Drum according to the invention
3. 3. Drum wall
4. 4. Alveolus of the drum according to the state of the art
5. 5. Support area
6. 6. Lech
7. 7. Side wall of the support zone
8. 8. Central part bonding the side walls of the support zone
9. 9. Rotor blade
10. 10. Hollow part in the central part
11. 11. Rounded edges framing the hollow part
12. 12. Fixing platform
13. 13. Line delimiting the aerodynamic vein
14. 14. projecting part
15. 15. Additional room, also called sector
16. 16. Area of investment of the sector
17. 17. Blade of dawn
18. 18. Threaded rod
19. 19. Nut

Detailed description of the invention

Two respective views in partial section (upper half) and axial of a compressor drum according to the state of the art 1 and according to the invention 2 (in gray) are superimposed on the figure 1 . In the illustrated example, the respective drums are intended to fix three stages of rotor blades (not shown).

The drums 1.2 comprise a wall 3 generally symmetrical in rotation about an axis of rotation, the wall 3 thus forming a hollow body in the shape of an oval or ogive. The wall 3 comprises a web defining the general shape of the drum. According to the conventional architecture, the wall 3 further comprises cells 4 for receiving the roots of the rotor blades. According to the present invention, the wall 3 instead of the cells 4 support zones 5. The drums 1,2 also conventionally include wipers 6 disposed between the rotor blade stages and intended to be positioned opposite the abradable inner ferrules (not shown).

• une paroi 3 de tambour comportant des zones supports 5,
• des aubes rotoriques 9 comportant chacune une plateforme 12 fixée à la zone support 5,
• des éléments de fixation assurant la fixation entre les plateformes 12 et les zones supports 5,
• et des pièces 15, appelées secteurs, assurant la reprise des efforts lors de la mise sous tension des éléments de fixation.

The rotor architecture according to the invention and as partially shown in FIG. figure 3 results from the assembly of four main elements which will be described below:

• a drum wall 3 comprising support zones 5,
• rotor blades 9 each comprising a platform 12 fixed to the support zone 5,
• fixing elements ensuring the fixing between the platforms 12 and the support zones 5,
• and parts 15, called sectors, ensuring the recovery of forces when powering the fasteners.

The support zone 5 of the wall 3 visible to the figures 1 and 3 comprises two side walls 7 and a central portion 8 joining the two side walls 7 and intended to be fixed to the rotor blade 9. The support zone 5 thus forms an annular cavity open towards the inside of the hollow body and raised relative to the neighboring wall 3 forming the veil. According to the present invention, the side walls 7 of the support zone 5 are preferably inclined relative to a perpendicular to the axis of rotation (radial direction) and connected to the web by rounded sections.

According to a preferred embodiment of the invention, the central portion 8 has on its outer face to the hollow body, a hollow portion 10 and rounded edges 11 connecting it to the side walls 7. The hollow portion 10 serves as a housing for the platform 12 of the rotor blade 9, as will be described below, and is preferably provided with a flat bottom. The rounded edges 11 flanking the hollow portion 10 are at the height of the line 13 which delimits the aerodynamic vein (see figure 1 ). On its inner side, ie on its face facing the hollow body, the central portion 8 also has rounded edges connecting it to the side walls 7 and a projecting portion 14 directed towards the inside of the annular cavity formed by the support zone 5. According to this first form of embodiment of the invention, the projecting portion 14 may be substantially corresponding in shape to that of the hollow portion 10. Preferably, the projecting portion 14 comprises an area 16 of an additional piece 15, also called sector. Still preferentially, the placement area 16 and the area 15 are planar.

One or more openings are formed through the thickness of the central portion 8 to allow the attachment of each platform 12 to the central portion 8. According to the embodiment of the invention, or the orifices are formed through the thickness of the hollow portion 10 of the central portion 8.

The rotor blade 9 according to the invention comprises a blade 17 and an attachment platform 12 located in a plane substantially perpendicular to that of the blade. The platform and the blade of the blade are of such dimensions that the platform 12 is housed in the hollow portion 10 while the blade root of the blade partially rests on the rounded edges 11 flanking the housing (see figures 2 and 3 ). Preferably, the platform 12 comprises a flat surface that cooperates with the flat bottom of the hollow portion 10. The platform may, however, take other forms and fit into a housing of complementary shape.

To ensure the attachment of the platform 12 to the support zone 5, different variants are possible. According to a preferred variant, the platform 12 is provided with one or more rods (s) intended (s) to be inserted respectively into the or orifices formed through the thickness of the central portion 8 and allowing fixation from the support zone 5 to the platform 12 of the blade by one or more bolted fasteners, one or more lockbolts or one or more rivets. Preferably and as illustrated in figures 2 and 3 , the platform 12 has a threaded rod 18 at its center and is attached to the support zone 5 by a bolted fastener. According to another variant, the platform 12 comprises one or more orifices for later receiving one or more fastening elements respectively (not shown). According to yet another variant, the platform comprises one or several orifices and one or more rods (not shown).

As mentioned above, and preferentially, the inner face of the central portion 8 comprises an investment area 16 of an additional piece 15, also called sector. This piece is provided with one or more orifices intended to be placed (s) facing the orifice (s) formed through the thickness of the central portion. The sector makes it possible not to damage the central part of the support zone during the assembly tensioning of the fastening element or elements. In the example shown in figure 3 , the sector 15 serves to take up the compressive stresses when screwing the nut 19 on the threaded rod 18. In the case of a lockbolt, the sector is placed between the rod and the lockbolt ring and in the case a rivet, it comes to be placed between the stem and the deformed part of the rivet.

According to the present invention, the rotor blades are, for example, made of a titanium alloy (TA6V) or aluminum MMC (for Metal Matrix Composite). The drum according to the invention is made of an organic matrix composite material or a metallic material such as, for example, a conventional titanium alloy (TA6V).

Advantages of the invention

The rotor according to the invention is lighter in its architecture to reduce the mass of the foot of the blade and remove the cells. This new architecture also makes it possible to introduce new materials (composite drum, MMC aluminum blades) that would not be compatible with a conventional design and thus allows even more significant mass reduction.

This drum profile makes it possible to bring the veil of the drum closer to the inner vein, thus minimizing the mass of the blade as mentioned above, a mass that the drum must therefore no longer support. This drum profile also makes it possible to free space for the feet of the stator vanes and the inner ferrules.

This fastening system makes it possible to guarantee blade positioning in all operating cases, even at low rotational speeds and even at standstill, in contrast to the conventional design where the blades have a positioning latitude generating, in particular, the phenomena of oscillation (rocking), consumer of axial and radial games. The removal of blade rocking and, consequently, the reduction in the consumption of axial games makes it possible to improve the compactness of the booster and therefore the total mass of the engine.

The architecture according to the invention also makes it possible to reduce the radial clearance consumptions by the disappearance of the point masses that are the latches and balancing masses thereof used in the conventional architecture with cells and inducing ovalization of the drum. The decrease of the ovalization of the rotor makes it possible to improve the aero performances via a reduction of the radial clearances as well as a reduction of the variation of these on the same floor.

It also facilitates the assembly and control of the games by a blade attachment easier to implement and stable.

It also makes it possible to increase the natural frequencies of the system which limits the risks of harmful vibration phenomena (drum mode, rotor-stator interaction).

The use of composite materials for the compressor rotor drum optimizes fiber orientation to maximize circumferential stiffness. This results in an increase in life span and a reduction in the consumption of radial clearances (less swelling of the drum with a metal material through the maximization of stiffness).

The use of composite materials for the drum also makes it possible to minimize the rotating mass of the drum, and consequently to reduce the amount of material required (thickness) thereon.

The use of composite materials for the drum also reduces manufacturing costs through a very significant reduction in material requirements, the mass ratio of the part / material purchased is particularly unfavorable in the case of a starting titanium drum a large forged and requiring a lot of machining unlike composite parts.

The simplicity of assembly also reduces assembly and control times.

Finally, the architecture according to the invention also provides the possibility of lightening the blower system and mainly the blower disc, by reducing the forces on it from the drum, thanks to the lightening of the rotor low pressure.

Claims (15)

1. A compressor drum (2) for an axial turbomachine, comprising:

   - a wall (3) generally symmetrical in revolution relative to the rotation axis of the turbomachine and forming a hollow body with an oval or bullet shape, said wall (3) comprising a shroud defining the general shape of the drum (2) and a support zone (5) that is raised relative to the shroud in a direction oriented toward the outside of the hollow body; said support zone (5) comprising a central portion (8) and side walls (7) connecting the central portion (8) to the shroud of the drum (2), the support zone (5) thus forming an annular cavity that is opened toward the inside of the hollow body and raised relative to the adjacent wall (3) forming the shroud;

   - at least one rotor stage comprising a row of rotor vanes (9) each provided with a platform (12), said platform (12) of each of said vanes (9) being assembled to the central portion (8) of the support zone (5) using one or more fastening elements, the central portion (8) being provided, on its face outside the hollow body, with a housing intended to receive the platform (12) of each of said rotor vanes (9).
2. The drum (2) according to Claim 1, characterized in that said platform (12) covers the entire central portion (8).
3. The drum (2) according to any one of the preceding claims, characterized in that said platform (12) comprises at least one fastening element and/or comprises at least one orifice allowing the passage of the fastening element.
4. The drum (2) according to any one of the preceding claims, characterized in that the central portion (8) comprises, on its face inside the hollow body, a placement area (16) for an additional piece (15), also called sector.
5. The drum (2) according to Claim 4, characterized in that the central portion (8) and the sector (15) comprise at least one orifice each allowing the passage of the fastening element.
6. The drum (2) according to any one of the preceding claims, characterized in that the central portion (8) is connected to the side walls (7) by rounded edges (11), the crest of the rounded edges (11) delimiting an aerodynamic vein, and in that the side walls (7) are connected to the shroud of the drum (2) by rounded sections.
7. The drum (2) according to any one of the preceding claims, characterized in that the side walls (7) are slanted relative to a perpendicular to the rotation axis.
8. The drum (2) according to Claim 4, characterized in that the placement area (16) is arranged on a portion (14) that protrudes toward the inside of the support zone (5).
9. The drum (2) according to Claim 4, characterized in that the sector (15) and the placement area (16) are planar.
10. The drum (2) according to Claim 1, characterized in that the housing of the central portion (8) is planar and cooperates with a planar surface of the platform (12) of the vane.
11. The drum (2) according to Claim 2, characterized in that the shape of the platform (12) is complementary to the central portion (8).
12. The drum (2) according to any one of the preceding claims, characterized in that the fastening element is a bolted clip, a lockbolt or a rivet.
13. The drum (2) according to Claim 12, characterized in that the rod of each bolted clip or of each lockbolt or rivet is an integral part of the platform (12) of the rotor vane.
14. The drum (2) according to Claim 12, characterized in that the sector (15) becomes sandwiched between the central portion (8) and a nut (19) of the bolted clip or between the central portion (8) and a ring of the lockbolt or between the central portion (8) and a deformed portion of the rivet.
15. The drum (2) according to any one of the preceding claims, characterized in that the rotor vanes (9) are made of MMC (metal matrix composite) aluminum, or of a titanium alloy, and in that the drum (2) is made of a metal material or an organic matrix composite material.

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