EP2369136B1 - Weight-reduced single-piece multi-stage drum of an axial flow compressor - Google Patents

Description

Technical area

The invention relates to an axial turbomachine compressor drum, more particularly to a rotor stage of such a compressor, knowing that the drum may consist of an assembly of several parts corresponding to different rotor stages.

More particularly still, the invention relates to measurements of construction of an axial turbomachine compressor drum, these measures being intended in particular to lighten the drum.

Prior art

In general, a compressor drum is a hollow body generally symmetrical in revolution with respect to its axis of rotation which corresponds to the axis of the turbomachine. The hollow body has a general shape of oval or ogive according to the shape of the flow. Several rows of blades are fixed to the drum so as to form different rotor stages, knowing that each rotor stage cooperates with a stator stage consisting of a row of stator vanes, each pair of rotor and stator stages thus forming a stage of compressing the compressor.

The centrifugal forces exerted by the rotor blades on the drum are very high, in particular when the drum is of large diameter and / or at a high speed of rotation. It is a constant concern for the compressor designers to ensure a satisfactory mechanical strength of the drum and the blades while ensuring to lighten the drum to the maximum.

Patent documents WO 2006/110125 A12 and US 2003/0223873 A1 each disclose an axial turbomachine compressor drum rotor stage according to the preamble of claim 1.

A classic design is disclosed in particular to the patent document US 4,784,572 . The drum consists of a generally smooth web, with the exception of wipers intended to cooperate with the abradable material stator ferrules. He is provided with reinforcements on his face inside at the rotor blades. These reinforcements are an integral part of the drum and are in the form of internal ribs whose thickness is greater at their ends directed towards the inside of the drum. These reinforcements are commonly called "leeks" because of their shape. These reinforcements significantly weigh down the drum because of their massiveness. The latter is the result of an optimum between two trends, namely that of adding material to increase the stiffness of the drum and that of limiting the addition of material to the drum due to centrifugal forces and knowing that this addition of material is all the more penalizing as the material is removed from the axis of rotation. The rotor blades are equipped with a series of circular ribs for diffusion bonding to the outer surface of the drum web. These ribs participate in the stiffness of the drum. They also allow the rotor blades to be leveled with the stator vanes. The construction proposed in this document is interesting from a stiff point of view but imposes however a large massiveness which is detrimental especially for the weight of the compressor itself.

The patent document GB 2 059 819 A discloses a compressor drum and attempts to provide a lightweight drum construction. The drum consists essentially of a series of sections assembled by diffusion. The drum comprises a web provided with internal ribs at the locations of the web intended to receive the rotor blades. The web comprises on its outer surface a pair of ribs at each section for receiving a row of blades. This pair of ribs forms a U-shaped receptacle for receiving the foot of a blade specially designed to cooperate with this receptacle. Fixing is done by inserting a pin or pin through the wings of the U and the wings of the foot of the blade. This construction certainly provides interesting rigidity but it imposes certain geometric tolerances at the level of the fitting of the blade root and the receptacle and a large mass, especially because of the ribs and the connecting pin.

A European patent application no. 08172923.0 filed by the applicant of the present application, and not yet published discloses a lighter compressor drum comprising, besides the veil, a series of sections for receiving, each, a row of rotor blades, these sections being raised relative to the veil . The outer surface of these sections defining the fluid stream is provided with a series of openings, each of these holes being intended to receive a blade platform. The platform is then welded to the wall. These holes extend longitudinally over almost the entire surface delimiting the aerodynamic fluid vein. These holes in the wall section are unfavorable because they partially deform.

The object of the invention is to propose a drum rotor stage or a drum which overcomes at least one of the disadvantages mentioned above, more particularly the object of the invention is to propose a lightened drum.

Summary of the invention

The invention consists of an axial turbomachine compressor drum rotor stage, said compressor being intended to be traversed by a fluid stream in a direction generally oriented along the axis of rotation, the rotor stage comprising a generally symmetrical wall in revolution. relative to the axis of rotation and forming a hollow body, said wall comprising a web and an annular zone for supporting a row of blades and integrally formed with the web; each of said blades having a leading edge and a trailing edge; said annular zone comprising a raised central portion with respect to said web, whose outer surface delimits the fluid vein between the vanes and is in one piece and formed integrally around said annular zone from an upstream edge of said central portion; to the leading edge of the row of blades and / or from a downstream edge of said central portion to the trailing edge of the row of blades, characterized in that the annular zone comprises an upstream stiffening part connecting the central part to the veil upstream and a downstream stiffening part connecting the central part to the veil downstream.

This construction makes it possible to obtain a stiffened and lightened drum. Indeed, raising the support area of the blades creates a boss or half-box at the wall under the blade row, that is to say exactly where the efforts are greatest. In addition, the fact of providing a continuous surface at the central portion defining the fluid stream avoids deforcing the boss thus created. In comparison with the state of the art, this construction replaces conventional fasteners such as pin-holes and alveoli, as well as massive "leeks" by a particular shape of the wall at the level of the zone intended to support the vanes. The inner surface of the boss or half-box is preferably free of rib, for example of the type "leek" serving only reinforcement and adding massiveness. The vanes can be integrally formed with the rotor or welded to the surface in question. Alternatively, a lower part of the blades may be formed integrally with the rotor, the remaining portion of the blades being then welded to this part.

The presence of two stiffeners ensuring the connection of the central part to the veil ensures optimum stability of the annular support area of the blades.

According to an advantageous embodiment of the invention, the outer surface of the central portion of the annular zone is generally smooth, preferably generally cylindrical, conical or curved over the length of said surface along the axis of rotation.

Such a construction of the outer surface of the central portion has the advantage of ensuring good aerodynamics.

According to another advantageous embodiment of the invention, at least a portion, preferably all, of each blade is integrally formed with the annular zone. Alternatively the vanes can be welded at their base to the annular zone. Different weld connection configurations are possible, with or without platform integrally formed with the blade.

According to another advantageous embodiment of the invention, the annular zone comprises at least one stiffening part generally perpendicular to the axis of rotation or inclined, preferably at an average angle of more than 40 ° with the axis of rotation, connecting the central portion to the web. This stiffener may be a simple rib emanating from the veil and joining the support zone. Depending on various sizing parameters, it is possible to provide only one central stiffening portion for a row of blades, providing the connection between the web and the annular zone. In this case, the stiffening portion could have a rib shape generally perpendicular to the axis of rotation and the annular zone would have a bandage shape. The veil would be free of stiffener on its internal face to the right of the stiffener.

According to another advantageous embodiment of the invention, the or at least one of the stiffening parts is generally perpendicular to the axis of rotation or inclined at an average angle of more than 40 ° with the axis of rotation, preferably at an angle average of more than 50 °. The inclination of one or both stiffener parts makes it possible to modify the longitudinal stiffness of the drum and hence the longitudinal dynamics of the drum. This measurement can thus be used to control vibratory modes in relation to the functional clearances between the rotor and stator elements.

According to yet another advantageous embodiment of the invention, the inner surface of the central part and the upstream and downstream parts of the annular zone form an annular cavity open towards the inside of the hollow body of the rotor stage. This measure defines an optimal shape of boss providing reinforcement while minimizing the supply of material.

According to yet another advantageous embodiment of the invention, the section of the annular zone in a plane passing through the axis of rotation has a generally U-shaped profile whose opening is directed towards the axis of rotation.

According to yet another advantageous embodiment of the invention, the or at least one of the stiffening parts is projecting from the web towards the interior of the hollow body. These projecting parts advantageously increase the stiffness of the stiffening parts.

According to another advantageous embodiment of the invention, the junction of the upstream stiffening portion with the central portion of the annular zone is approximately perpendicular, in a direction perpendicular to the axis of rotation, of the intersection of the edge. driving the vane row with said central portion and / or the junction of the downstream stiffening portion with the central portion of said annular zone is approximately plumb, in a direction perpendicular to the axis of rotation, of the intersection of the trailing edge of the row of vanes with said central portion. This arrangement makes it possible to optimize the recovery of the stresses exerted by the rotating blades.

According to yet another advantageous embodiment of the invention, the junction of the upstream and / or downstream stiffening part with the central part of the support zone is set back from the upstream and / or downstream edge, respectively, of said central part, so as to that the upstream and / or downstream edge of said central portion is projecting. The fact that the connecting portions are slightly recessed from the respective edges of the central portion allows to limit certain concentrations of stresses in the dawn.

According to another advantageous embodiment of the invention, the junction of the upstream stiffening part with the central part of the annular zone is set back downstream of the intersection of the leading edge of the row of vanes with said central portion. and / or the junction of the downstream stiffening portion with the central portion of said zone is recessed upstream of the intersection of the trailing edge of the row of vanes with said central portion.

According to another advantageous embodiment of the invention, the central portion extends along the axis of rotation from the leading edge to the trailing edge of the blade row.

According to another advantageous embodiment of the invention, the central portion extends along the axis of rotation, preferably exclusively, since a connection fillet from the leading edge to a connection fillet of the trailing edge of the blade row.

The invention also consists of an axial turbomachine compressor drum comprising at least one stage, preferably several stages, as defined above.

Other features and advantages of the present invention will be better understood from the description and drawings.

Brief description of the drawings

The figure 1 is a partial sectional view of a compressor comprising a drum with several rotor stages according to the invention.

The figure 2 is a partial sectional view of a first rotor stage alternative according to the invention.

The figure 3 is a partial sectional view of a second rotor stage alternative according to the invention.

The figure 4 is a partial sectional view of a third rotor stage alternative according to the invention.

The figure 5 is a partial sectional view of a fourth rotor stage alternative according to the invention.

The figure 6 is a partial sectional view of a fifth rotor stage alternative according to the invention.

Description of the embodiments

A compressor comprising a drum or rotor according to the invention is illustrated in FIG. figure 1 . This is a sectional view of the rotor 2 and the stator 8. The drum 2 consists of a wall 4 generally symmetrical in rotation about the axis of rotation, the wall 4 thus forming a shaped hollow body Oval or warhead. The wall 4 comprises a web defining the general shape of the drum. For the sake of simplicity of illustration, the figure 1 shows only the upper half of the rotor assembly 2 and stator, knowing that the other lower half is symmetrical to the upper half relative to the axis of rotation. It is the same for the stator 8. The stator 8 and the rotor 2 define an annular passage for a fluid stream of air to move and compress from left to right according to the representation in FIG. figure 1 . For this purpose, the rotor 2 comprises a fan 10 (partially shown at the far left of the figure) and three parallel rows of blades 14. These vanes 14 are rigidly attached to the drum 2 and thus rotate with it. Rows of rectifying vanes 12 are arranged between the rows of rotor blades 14. These straightening vanes 12 are rigidly fixed at their upper ends to the wall 6 of the stator 8. Each row of stationary blades 12 constitutes a rectifying grid whose function is to straighten the fluid flow coming from the row of rotor blades 14 directly in upstream. A row of rotor blades combined with a row of directly downstream stator vanes constitutes a stage of the compressor. In the case of figure 1 for example, the compressor has three stages. A row of stator vanes is present between the fan 10 and the first row of rotor blades 14. This row of vanes straightens the fluid flow generated by the fan 10.

As can be seen at figure 1 , the stator vanes 12 are fixed to outer shells forming the wall 6 of the stator 8. The lower ends of the vanes of each row of the stator are embedded in an inner ferrule 18, respectively. Each inner ferrule 18 is dimensioned so as to bind the vanes of the stator together and to cooperate sealingly with the rotor 2. In fact, each ferrule has on its inner surface a brittle material more commonly referred to as the "abradable" which has, as its name suggests, the ability to dig a path forming a labyrinth when friction with the wipers 16 of the rotor web. These wipers 16 are circular ribs provided on the outer surface of the rotor 2 facing the inner ferrules 18, respectively. These ribs extend in a plane generally perpendicular to the axis of rotation of the rotor and have a tip-shaped outer edge in order to be able to come into contact with the abradable material to ensure a certain seal while minimizing the contact surface. and therefore the friction forces.

The rotor or drum shown at figure 1 is monobloc, namely that its wall 4 is formed in one piece. The rotor blades 14, at least their feet or lower parts are also formed integrally with the wall 4. Although this is not visible in the figure, the rotor blades may each consist of a bottom part integrally formed with the rotor and an upper part which is fixed to the lower part, preferably by any conventional bonding method such as welding. The wall 4 of the rotor is made of metallic material such as titanium. It is initially shaped roughly by forging operation and then machined. The wall 4 comprises a veil defining the generally convex cylindrical shape or oval or ogive, and supporting the wipers 16. In addition to the veil, the wall also includes areas for supporting the rotor blades. These zones have a particular geometry to optimize the stiffness of the rotor and its mass.

The rotor thus comprises three of these zones constructed in a similar manner. The support zone of the first rows of rotor blades will thus be described in more detail, knowing that this description also applies to the other stages of the rotor.

The support zone of the wall 4 is annular in shape and consists essentially of two wall portions 20 and 22 in the form of ribs generally perpendicular to the axis of rotation and a central portion 21 supporting the row of vanes. The central portion 21 is thus raised relative to the surrounding wall forming the veil. This elevation in a direction generally perpendicular to the axis of rotation and directed towards the outside of the hollow body allows the outer surface of the central portion 21 to be at the surfaces of neighboring inner rings 18 delimiting the fluid stream. These surfaces of the inner ferrules are indeed at a distance from the veil because of the height of the wipers and the necessary thickness of the ferrule. The surfaces of the inner rings and the central portions 21 of the annular zones, which delimit the fluid stream are thus generally compensated and aligned so as to ensure the least disturbed flow possible.

The central portion 21 of the annular support zone is generally of generally straight or slightly curved section so as to correspond to the general shape of the fluid vein of the rotor. This central portion has a generally annular shape with the blade roots integrally formed with it. It has a length, in a longitudinal direction, which corresponds essentially to the width in this direction of the blade roots with their connecting fillet. The central portion 21 thus constitutes a generally annular platform for the blade row. The upstream side portions 20 and downstream 22 in the form of ribs connect this platform to the rest of the veil. The annular support zone of the blades thus forms an annular cavity inside the hollow body and open towards the latter, in the direction of the axis of rotation. The section of the annular zone in a plane passing through the axis of rotation has a generally "U" shaped profile whose opening is directed towards the axis of rotation.

The junctions of the upstream and downstream lateral portions 22 and 22 with the central portion are such that they are at a distance from the respective ends of the platform formed by the central portion. The junction of the upstream portion 20 with the central portion 21 is approximately plumb (along a perpendicular to the axis of rotation) of the leading edge of the blade, more precisely below the intersection of the extension of the leading edge of the dawn with the platform. The same goes for the downstream wall part with the trailing edge of the blade. The platform formed by the central portion and has a projecting edge upstream side and similarly a projecting edge downstream side. This construction makes it possible to optimize the recovery of the centrifugal forces exerted by the blades. Indeed, the massivity of the blades is present over their entire width, so that the fact of providing the retaining platform away from its upstream and downstream edges avoids an unfavorable concentration of stress at the level of the connection fillet. In addition, these construction measures provide a certain space between the upstream edge and the web, and similarly between the downstream edge and the web, this place to bring the rows of rotor blades and stator blades, respectively, which considerably reduces the total weight of the compressor.

The upstream and downstream wall portions 22 of the annular zone project from the web towards the interior of the hollow body, thus forming ribs 24 and 26 internal to the hollow body. They contribute to the strengthening of the rotor and have the advantage that their massivity is somewhat behind the veil and therefore closer to the axis of rotation.

It should be noted that the blade roots do not have to be integrally formed with the rotor. Indeed, it is quite possible to provide the smooth support zone, possibly provided with an orifice intended to ensure or reinforce the attachment of the blades thereafter. The blades can indeed be simply welded at their feet to the support zone, flush with the outer surface of the central portion 21. The blades may also have at their feet a surface comparable to a fixing platform for insertion into a corresponding orifice of the annular zone to be welded thereafter. In this case, this platform would ideally be small, namely essentially centered on the dawn and away from the leading and trailing edges.

It should also be noted that the rotor wall does not have to be built in one piece. Indeed, it may even be desirable to provide several sections to be assembled. Such a construction makes it possible to make a substantial gain in the material to be machined because it enables a first shaping by forging which will be substantially closer to the final shape. This results in a reduction in loss of material removed by machining and a reduction in machining time.

The figure 2 illustrates a first alternative construction of an annular support zone of the rotor. The arrow indicates the flow direction of the fluid. This first alternative differs from the construction present at the different stages of the rotor of the figure 1 essentially in that the upstream side portions 20 and downstream 22 are connected to the veil by rounded and thus no longer projecting from the veil inward hollow body. The wall roundings have the advantage of reducing the stress concentrations at the junctions between the lateral parts and the web. This reduction in stress concentration makes it possible to perform the internal ribs present in the design of the figure 1 . The junctions of the upstream and downstream lateral wall portions 22 with the platform or central portion 21 are spaced from the respective upstream and downstream edges 32, and slightly recessed towards the inside of the cavity formed by the edges of the walls. attack 27 and leakage 28, respectively.

The figure 3 illustrates a second alternative of construction of an annular support area of the rotor blades. The arrow indicates the flow direction of the fluid. This alternative is different from the construction of the figure 1 essentially in that the upstream and downstream lateral wall portions 22 are inclined with respect to a perpendicular to the axis of rotation. This inclination has the advantage of being able to control the stiffness of the drum along its axis of rotation while enjoying the advantages of the construction of the drum. figure 1 . The rotor may indeed be subject to a longitudinal vibratory dynamic, because of certain vibratory modes in this direction. Inclining one or the other of the side wall portions at the support zone makes it possible to maintain a sufficient longitudinal stiffness. This measurement is all the more useful if the mechanical clearance between the upstream or downstream edge 32 and the adjacent edge of the inner shell is reduced.

The figure 4 is a third alternative of construction of an annular support area of the rotor blades. The arrow indicates the flow direction of the fluid. It's basically a combination of the designs of the figures 2 and 3 , namely with the particularity that the upstream and downstream lateral portions 20 and 22 are inclined as in figure 3 and are connected to the veil by rounded sections as in the figure 2 . This construction therefore presents the combined benefits of the achievements of the figures 2 and 3 .

The figure 5 illustrates a fourth alternative of construction of an annular support area of the rotor blades. The arrow indicates the flow direction of the fluid. This alternative corresponds to the construction of the figure 4 with the difference that one of the lateral parts, for example the downstream part 22, is generally perpendicular to the axis of rotation and not inclined. In this case, the downstream side portion 22 has no connection to the web. This construction can be interesting for the last row of dawn. It makes it possible to maintain a rigidity with significant radial forces while ensuring a necessary longitudinal rigidity.

The figure 6 illustrates a fifth alternative construction of a rotor blade support zone. The arrow indicates the flow direction of the fluid. This alternative is similar to the constructions illustrated in figure 1 where, however, the internal ribs 24 and 26 are no longer protruding towards the axis of rotation but well now towards each other, that is to say in a longitudinal direction.

It is important to note that the different alternative constructions of the rotor blade support zones are purely illustrative and not limiting. There are therefore other similar constructions in accordance with the invention.

In addition, it should be noted that each rotor stage may have a construction of the annular support area of the blades which will be specific to it according to various sizing parameters.

In the description of the invention which has been made above, the wall constituting the web and the annular support area of a rotor stage is provided in one piece. Although this embodiment seems to be the most practical to date, it should be noted that the invention could provide that the wall of the rotor stage is composed of several wall sections assembled for example by welding.

Claims (14)

1. Rotor stage of a compressor drum of an axial turbo machine, said compressor being designed to be traversed by a fluid stream in a direction generally along the axis of rotation, the rotor comprising a wall (4) generally symmetrical in revolution in relation to the axis of rotation and having a hollow body, the said wall comprising a web and an annular zone (20, 21, 22) for supporting a row of blades (14) and integrally formed with the web, each of the said blades having a leading edge (27) and a trailing edge (28);
   the said annular zone comprising a central portion (21) raised relative to the said web, whose outer surface defines the fluid stream between the blades (14) and is integrally on the periphery of the said annular zone from an upstream edge (30) of the said central portion (21) to the leading edge (27) of the blade row (14) and/or from a downstream edge (32) of the said central portion (21) to the trailing edge (28) of the blade row;
   characterised in that
   the annular area comprises a upstream stiffener (20) part connecting the central portion (21) to the web upstream and a downstream stiffener (22) connecting the central portion (21) to the web downstream.
2. Rotor stage according to the preceding claim, characterised in that the outer surface of the central portion (21) of the annular zone is generally smooth, preferably of a generally cylindrical, conical or convex form along the length of the said surface along the axis of rotation.
3. Rotor stage according to one of the preceding claims, characterised in that at least part, preferably all, of each blade (14) is integrally formed with the annular zone (20, 21, 22) or each blade (14) is welded to the said annular zone (20, 21, 22).
4. Rotor stage according to one of the preceding claims, characterised in that the annular zone comprises at least one stiffener (20, 22) generally perpendicular to the axis of rotation or at an angle that is preferably at an average of more than 40° with the axis of rotation, connecting the central portion (21) to the web.
5. Rotor stage according to one of the preceding claims, characterised in that at least one stiffener (20, 22) generally perpendicular to the axis of rotation or at an average angle of more than 40 ° with the axis of rotation, preferably at an average angle of more than 50 °.
6. Rotor stage according to one of the preceding claims, characterised in that the inner surface of the central portion (21) and the upstream (20) and downstream (22) parts of the support zone for the blade row forms an annular cavity open towards the interior of the hollow body of the rotor stage.
7. Rotor stage according to one of the preceding claims, characterised in that the section of the annular zone (20, 21, 22) in a plane passing through the axis of rotation has a profile in the general shape of a U, the opening of which is directed towards the axis of rotation.
8. Rotor stage according to one of the preceding claims, characterised in that at least one of the stiffeners (20, 22) protrudes inwards towards the web of the hollow body.
9. Rotor stage according to one of the preceding claims, characterised in that the junction of the upstream stiffener (20) with the central portion (21) of the annular zone is approximately in line, along a direction perpendicular to the axis of rotation, with the intersection of the leading edge (27) of the blade row with the said central portion (21) and/or the junction of the downstream stiffener (22) with the central portion (21) of the said annular zone is approximately in line, along a direction perpendicular to the axis of rotation, with the intersection of the trailing edge (28) of the blade row with the said central portion (21).
10. Rotor stage according to one of the preceding claims, characterised in that the junction of the upstream (20) and/or downstream (22) stiffener with the central portion (21) of the annular zone is set back from the upstream (30) and/or downstream (32) edge of the said central portion (21) respectively, so that the upstream and/or downstream edge of the said central portion protrudes.
11. Rotor stage according to one of the preceding claims, characterised in that the junction of the upstream stiffener (20) with the central portion (21) of the annular zone is set back downstream from the intersection of the leading edge (27) of the blade row with the said central portion (21) and/or the junction of the downstream stiffener (22) with the central portion (21) of the said annular zone is set back upstream from the intersection of the trailing edge (28) of the blade row with the said central portion (21).
12. Rotor stage according to one of the preceding claims, characterised in that the central portion (21) extends along the axis of rotation from the leading edge (27) to the trailing edge (28) of the blade row.
13. Rotor stage according to one of the preceding claims, characterised in that the central portion (21) extends along the axis of rotation, preferably exclusively, from a fillet on the leading edge (27) up to a fillet on the trailing edge (28) of the blade row.
14. Compressor drum (2) of an axial turbo machine, comprising at least one stage, preferably several stages, according to one of the preceding claims.

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