GUIDE BOWL ARRANGEMENT FOR AN AIRCRAFT TURBINE ENGINE

Description

Domaine technique de l'invention

[0001] The invention relates to the field of aircraft turbomachine rectifiers. Arrière-plan technique

[0002] The state of the art includes in particular documents FR-A1-3 082 233, FR-A1-3 055 145, FR-A1-3 001 761 and EP-A1-3 540 180.

[0003] In aircraft turbomachines, and in particular in twin-spool turbojets, each stage of a compressor conventionally comprises, on the one hand, a rotor part with moving blades whose rotation around an axis of the turbomachine causes the acceleration of a flow in a vein of the compressor and, on the other hand, a stator part, attached to the rotor part, whose role is to straighten the flow coming from the rotor blades. This stator part, also called a rectifier, is made up of a plurality of sectors which, placed end to end, form a complete annular-shaped rectifier. In other words, a rectifier is sectored and comprises a plurality of sectors arranged circumferentially next to each other and which extend around the same axis.

[0004] THE figures 1 et 2 respectively illustrate an example of a rectifier sector and several assembled sectors of a rectifier according to the state of the art. In particular, a single sector 101 is shown in the figure 1 and three sectors 101 are represented at the figure 2 .

[0005] The rectifier 100, partially represented in the figure 2 , comprises two annular ferrules 104 and 103, respectively internal and external, which extend around the same axis X and which are connected together by blades 102. Furthermore, as appears more clearly in the figure 1 , all the blades 102 of the sector 101 are identical and all the sector sections to which these blades are linked are also identical.

[0006] The repetition of identical sections over the entire longitudinal extent of sector 101 makes it sensitive to resonance phenomena linked to vibrations. More precisely, since all the sections are identical, they respond to the same frequencies and since their connections are made via very rigid ferrules, there is an accumulation of vibration phenomena and therefore an amplification of the response to vibrations of the rectifier as a whole.

[0007] Furthermore, the energy (from vibrations) is transmitted better from blade to blade if the ferrules that connect the blades are rigid.

[0008] In this case, the inner shell 104 has, in an axial section, an I-shape. More precisely, it comprises an inner cylindrical wall 105 and an outer cylindrical wall 107 which are connected to each other by an annular core 106. Experience shows that such a geometry results in very high vibration levels and a very dense modal base. In particular, the fact that this geometry has a very dense modal base promotes the accumulation of modes and consequently results in high vibration levels (i.e. an amplitude of vibrations).

[0009] In summary, the problem of the response to rectifier vibrations in an aircraft turbomachine is a major issue. In particular, since such a rectifier is intended to be integrated into a high-pressure compressor of a high-pressure spool, it must be able to withstand difficult environmental conditions (i.e. in terms of pressures, temperature and high rotor speed) which generate a number of modes and high vibration levels. Résumé de l'invention

[0010] The present invention proposes a solution for reducing the vibration responses of a rectifier. Furthermore, the proposed solution does not affect the design of a sector linked to its aerodynamic properties (i.e. the shape of the blades) or its integration into the rectifier (i.e. the interfaces between sectors).

[0011] To this end, according to a first aspect, the invention relates to an aircraft turbomachine rectifier, this rectifier comprising two annular shells, respectively internal and external, extending around the same axis and connected together by blades, said internal shell having substantially, according to an axial section, an I-shape and comprising two cylindrical walls, respectively internal and external, and connected to each other by an annular core, the rectifier being sectorized and comprising a plurality of sectors arranged circumferentially next to each other around said axis, characterized in that each of the sectors comprises a core portion which comprises at least one concavity oriented in the axial direction.

[0012] By modifying the geometry of the internal shell of the rectifier, its response to vibrations is modified. In particular, the axial displacement of the core of the internal shell on certain portions of the shell results in a modification of the rigidity of said shell which makes it possible to reduce its vibration responses.

[0013] The rectifier according to the invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another: each of the sectors comprises a core portion which comprises at least one concavity oriented upstream relative to a direction of flow of the gases through the rectifier in operation. each of the sectors comprises a core portion which comprises at least one concavity oriented downstream relative to a direction of flow of the gases through the rectifier in operation. each of the sectors comprises a core portion which comprises at least two concavities oriented axially in the same direction. the rectifier sectors are identical. the core extends in the axial direction over a dimension which represents at least 200% of an axial thickness of the core. the core has a general sinusoidal shape around said axis. the core portion of each sector comprises circumferential ends which extend in a plane perpendicular to the axis, or which extend in planes inclined relative to this axis.the internal cylindrical wall carries an annular coating of abradable material. According to a second aspect, the invention also relates to an aircraft turbomachine, comprising at least one rectifier according to the first aspect. Brève description des figures

[0014] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which: [ Fig. 1 ] there figure 1 is a perspective view of a rectifier sector according to the state of the art; [ Fig. 2 ] there figure 2 is a perspective view of a rectifier according to the state of the art; [ Fig. 3a ] there figure 3a is a perspective view of a rectifier sector according to a first embodiment of the invention; [ Fig. 3b ] there figure 3b is a perspective view of a rectifier sector according to a first embodiment of the invention; [ Fig. 4a ] there figure 4a is a perspective view of a rectifier sector according to a second embodiment of the invention; [ Fig. 4b ] there figure 4b is a perspective view of a rectifier sector according to a second embodiment of the invention; [ Fig. 5a ] there figure 5a is a schematic representation of the shape of an internal shell of a rectifier sector according to a third embodiment of the invention; [ Fig. 5b ] there figure 5b is a schematic representation of the shape of an internal shell of a rectifier sector according to a fourth embodiment of the invention; [ Fig. 6a ] there figure 6a is a schematic representation of the shape of an internal shell of a rectifier sector according to a fifth embodiment of the invention; and, [ Fig. 6b ] there figure 6b is a schematic representation of the shape of an internal shell of a rectifier sector according to a sixth embodiment of the invention.

[0015] Elements having the same functions in different embodiments have the same references in the figures. Description détaillée de l'invention

[0016] THE figures 1 et 2 have been described in the above.

[0017] In reference to the figure 3a and to the figure 3b we will now describe a rectifier 300 of an aircraft turbomachine (not shown) according to a first embodiment. For reasons of readability, only the sector 301 of the rectifier 300 is shown while the other sectors are symbolized by the dotted lines at figure 3a The rectifier 300 therefore comprises a plurality of sectors 301 which are arranged circumferentially next to each other around an axis X. The complete rectifier 300 therefore has a ring shape.

[0018] THE figures 3a et 3b are two perspective views of a rectifier sector 301 from two distinct points of view, respectively from below (i.e. from the internal part of the sector) and from the edge (i.e. from one of the longitudinal ends of the sector). In both cases, the part 305, the innermost part of the sector 301, is shown in transparency to show more clearly the specific shape of a part of the sector described later.

[0019] The rectifier 300 comprises two annular ferrules 304 and 303, respectively internal and external, which extend around the same axis X and which are connected together by blades 302. As appears more clearly in the figure 3b , the internal ferrule has substantially, in an axial section, an I-shape. In particular, it comprises two cylindrical walls 305 and 307, respectively internal and external, which are connected to each other by an annular core 306. Those skilled in the art will appreciate that the invention also applies to a ferrule whose internal cylindrical wall carries an annular coating of abradable material.

[0020] Further, the inner ferrule 304 includes a core portion that includes an axially oriented concavity. In the example shown in figures 3a et 3b , the core 306 of the sector 301 has a substantially U shape. Thus, in this example, the concavity of the core is oriented upstream relative to a direction of flow of the gases through the rectifier in operation. In other words, the ends of the U are oriented upstream when the rectifier is mounted in the turbomachine. figures 4a et 4b illustrate another embodiment in which the core 306 of the sector 301 has substantially an inverted U shape, that is to say that the concavity of the core is oriented downstream relative to a direction of flow of the gases through the rectifier in operation.

[0021] In the various embodiments of the invention, the different sectors of the rectifier may all be identical or different from each other. Furthermore, in a particular embodiment, the ends of the sectors facing each other in the rectifier are identical. Advantageously, the fact that at least the ends of the sectors of a rectifier are identical makes it possible to avoid the occurrence of flux recirculation phenomena, that is to say the fact that a flux can circulate at the level of the internal shell at each junction between two distinct sectors.

[0022] THE figures 5a et 5b illustrate two embodiments of the rectifier in which each of the sectors comprises a core portion which comprises at least two concavities oriented axially in the same direction. For example, the core 502 has substantially the shape of two identical U-shaped sections placed side by side, as in figure 5b , or the soul 501 has substantially the shape of two identical inverted U's joined together, as in the figure 5a .

[0023] In other embodiments, the core of the inner ferrule may have a general sinusoidal shape. In still other embodiments, as shown in figures 6a et 6b , the core 601 or 602 has a substantially U shape whose ends are extended by core portions extending parallel to the longitudinal extent of the internal shell.

[0024] Advantageously, the variation of the axial position of the core along the longitudinal extent of a rectifier sector results in a local variation in the rigidity of the internal shell and, consequently, a variation in the vibration responses of the rectifier. In this case, the rigidity of the internal shell is locally reduced and this results in a reduction in the vibration responses of the sector.

[0025] The person skilled in the art will be able to adapt the shape of the core to obtain these effects in a given rectifier. In particular, the shape of the core may be modified so as to reduce the vibration responses specific to certain given vibration frequency ranges.

[0026] Furthermore, to achieve such an effect, the core may extend in the axial direction over a sufficient dimension to reduce its rigidity, for example, over a dimension that represents at least 200% of an axial thickness of the core. Thus, the local modification of the axial position of the core necessarily produces an effect on the vibration responses of the sector. Furthermore, in all cases, the core extends between the axial edges of the inner shell. In other words, the core does not protrude from the rest of the shell in the axial direction.

[0027] In the different embodiments of the rectifier, depending on the geometry of the sectors, the core of the internal shell of a sector can form a right angle with the edge of said sector (as for example for the embodiments of the figures 6a et 6b ) or be inclined relative to this slice (as for example for the embodiments of the figures 5a et 5b). In other words, the core portion of each sector which comprises at least one concavity, comprises circumferential ends which extend in a plane perpendicular to the axis around which the rectifier extends, or which extend in planes inclined relative to this axis. Advantageously, the manufacture of a rectifier using the rectifier sector geometries according to the invention can be obtained both by machining and by additive manufacturing.

[0028] Finally, in all embodiments of the rectifier, only the shape of the internal shell of the rectifier sectors is modified. The impact on the aerodynamic design or the integration of said rectifier is therefore zero.

Claims

1. A guide vane assembly (300) for an aircraft turbine engine, this guide vane assembly comprising two annular shells (304, 303), an internal and an external respectively, extending around a common axis (X) and connected together by blades (302), said internal shell having substantially, in axial cross-section, an I shape and comprising two cylindrical walls (305, 307), respectively internal and external, and connected to each other by an annular core (306), the guide vane assembly being sectorised and comprising a plurality of sectors (301) arranged circumferentially next to each other about said axis (X), characterised in that each of the sectors (301) comprises a core segment which comprises at least one concavity oriented in the axial direction.

2. The guide vane assembly of claim 1, wherein each of the sectors comprises a core segment which comprises at least one concavity oriented towards upstream with respect to a flowing direction of the gases through the guide vane assembly in operation.

3. The guide vane assembly of claim 1, wherein each of the sectors comprises a core segment which comprises at least one concavity oriented towards downstream with respect to a flowing direction of the gases through the guide vane assembly in operation.

4. The guide vane assembly according to any of the preceding claims, wherein each of the sectors comprises a core segment which comprises at least two concavities axially oriented in a same direction.

5. The guide vane assembly according to any of the preceding claims, wherein the guide vane assembly sectors are identical.

6. The guide vane assembly according to any of the preceding claims, wherein said core extends in an axial direction over a dimension that is at least 200% of an axial thickness of the core.

7. The guide vane assembly according to any of the preceding claims, wherein the core has a general sinusoidal shape about said axis.

8. The guide vane assembly according to any of the preceding claims, wherein the core segment of each sector comprises circumferential ends which extend in a plane perpendicular to the axis, or which extend in planes inclined with respect to that axis.

9. The guide vane assembly according to any of the preceding claims, wherein said internal cylindrical wall carries an annular coating of abradable material.

10. An aircraft turbine engine, comprising at least one guide vane assembly according to any of the preceding claims.