LABYRINTH SEAL COMPRISING AN ABRADABLE ELEMENT WITH VARIABLE CELL DENSITY

Abstract

The present invention relates to a labyrinth seal for a turbine engine, in particular of an aircraft, comprising a rotor element and a stator element extending around the rotor element, the rotor element being suitable for rotating relative to the stator element about an axis of rotation having an axial direction (DA), the rotor element comprising an annular lip having an outer radial end extending towards an abradable element (57) carried by the stator element, the outer radial end of the annular lip having a corrugation in the axial direction (DA) and a non-zero axial expanse (E.sub.5) associated with the corrugation, the abradable element (57) comprising a plurality of cells (50a, 50b) arranged adjacent to one another along the axial direction (DA) and an ortho-radial direction (O), the cells (50a, 50b) comprising walls which extend in an essentially radial direction, the cells being distributed with a first cell density in a first densified annular zone (Z.sub.51) of the abradable element, said densified annular zone (Z.sub.51) being located opposite the radial end of the lip, said densified annular zone having an axial expanse less than or equal to the axial expanse of the outer radial end of the lip, the cells being distributed according to a reference density of cells outside said first zone, the first density being greater than the reference density.

Claims

1. A labyrinth seal for a turbomachine, comprising: a stator element; a rotor element being configured to rotate relative to the stator element about an axis of rotation along an axial direction, the rotor element comprising—an annular wiper; the stator element extending around the rotor element; the stator element comprising an abradable element; the annular wiper having an outer radial end extending towards the abradable element, the outer radial end of the annular wiper having a corrugation along the axial direction, the corrugation having a non-zero axial extent; the abradable element including cells disposed adjacent to each other along the axial direction and along an orthoradial direction; the cells comprising walls which extend in a substantially radial direction; wherein the cells are distributed according to a first cell density in a first densified annular area of the abradable element; the first densified annular area being located directly facing the outer radial end of the wiper; the first densified annular area having an axial extent less than or equal to the axial extent of the corrugation; the cells being distributed according to a reference cell density outside the first densified annular area, the first cell density being superior to the reference cell density.

2. The labyrinth seal according to claim 1, wherein the cells are distributed according to respectively a second cell density and a third cell density in respectively a second densified annular area and a third densified annular area of the abradable element, each of the first, second and third densified annular areas being configured to be located directly facing the outer radial end of the wiper during different flight phases of the aircraft, the second cell density and the third cell density each being superior to the reference cell density.

3. The labyrinth seal according to claim 1, wherein at least one densified annular area among the first, second and third densified annular areas has an axial extent between 40% and 100% of the axial extent of the corrugation.

4. The labyrinth seal according to claim 1, wherein at least part of the cells have a honeycomb shape.

5. The labyrinth seal according to claim 1, wherein at least part of the cells in a densified annular area have a disc, square, triangle or rhombus shape.

6. A method for manufacturing a labyrinth seal for a turbomachine, including a rotor element and a stator element extending around the rotor element, the rotor element being configured to rotate relative to the stator element about an axis of rotation along an axial direction, the rotor element including an annular wiper having an outer radial end extending towards an abradable element carried by the stator element, the outer radial end of the annular wiper having a corrugation along the axial direction, the corrugation having a non-zero axial extent, the abradable element including cells disposed adjacent to each other along the axial direction and along an orthoradial direction, the cells comprising walls which extend in a substantially radial direction, the method comprising: manufacturing the wiper; and manufacturing the abradable element including a first densified annular area located directly facing the outer radial end of the wiper, the first densified annular area having a first cell density, the first densified annular area having an axial extent less than or equal to the axial extent of the corrugation, the cells being distributed according to a reference cell density outside the first densified annular area, the first cell density being superior to the reference cell density.

7. The method for manufacturing a labyrinth seal according to claim 6, wherein the manufacture of the abradable element further includes the manufacture respectively of a second densified annular area and of a third densified annular area of the abradable element, in which the cells are distributed according to respectively a second cell density and a third cell density, each of the first, second and third densified annular areas being located directly facing the outer radial end of the wiper during different flight phases of the aircraft, the second cell density and the third cell density each being superior to the reference cell density.

8. The method for manufacturing a labyrinth seal according to claim 6, further comprising: measuring the axial extent of the corrugation; determining an axial extent of at least one among the first, second and third densified annular areas of between 40% and 100% of the measurement of the axial extent of the corrugation.

9. The method for manufacturing a labyrinth seal according to claim 8, further comprising: determining a cell density of at least one among the first, second and third densified annular areas by taking into account the measurement of the axial extent of the corrugation.

10. The method for manufacturing a labyrinth seal according to claim 6, wherein the manufacture of the abradable element includes the manufacture of cells having a honeycomb shape.

11. The method for manufacturing a labyrinth seal according to claim 6, wherein the manufacture of the abradable element includes the manufacture in a densified annular area of cells having a disc, square, triangle or rhombus shape.

12. A turbomachine comprising a labyrinth seal according to claim 1.

13. The labyrinth seal according to claim 1, wherein the turbomachine is a turbomachine of an aircraft.

14. The method according to claim 6, wherein the turbomachine is a turbomachine of an aircraft.

Description

DESCRIPTION OF THE FIGURES

[0035] Other characteristics, aims and advantages of the invention will emerge from the following description which is purely illustrative and not limiting, and which should be read in relation to the appended drawings in which:

[0036] FIG. 1, already discussed, represents a labyrinth seal.

[0037] FIG. 2, already discussed, represents an abradable element.

[0038] FIG. 3a, already discussed, represents an opened and laid flat abradable element as well as the outer radial end of a facing wiper.

[0039] FIG. 3b, already discussed, represents an abradable element opened and laid flat as well as the outer radial end of a facing wiper.

[0040] FIG. 4, already discussed, represents an axial cross section of an abradable element and of a facing wiper.

[0041] FIG. 5 represents an abradable element opened and laid flat as well as the position of the outer radial end of a facing wiper.

[0042] FIG. 6 represents an abradable element opened and laid flat.

[0043] FIG. 7 represents an abradable element opened and laid flat.

[0044] In all of the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

[0045] FIG. 5 represents an abradable element 57 opened and laid flat and the position of the end of a facing wiper symbolized by the dotted line 59. The dotted line 59 does not follow an orthoradial direction and has a corrugation. The outer radial end of the wiper has deviations in the shape of a regular circle. The deviation in the form of a regular circle can be characterized by the axial extent E.sub.5 of the outer radial end of the wiper which is the projection of the line 59 along the direction D.sub.A.

[0046] FIGS. 1, 2 and 5 propose a labyrinth seal 10 for a turbomachine, particularly of an aircraft, including a rotor element 1 and a stator element 3 extending around the rotor element 1, the rotor element 1 being adapted to rotate relative to the stator element 3 about an axis of rotation A, the rotor element including an annular wiper 5 having an outer radial end extending towards an abradable element 7, 57 carried by the stator element 3, the outer radial end of the annular wiper having a corrugation along the axial direction and a non-zero axial extent E.sub.5 associated with the corrugation, the abradable element including a plurality of cells 20, 50a, 50b disposed adjacent to each other along the direction D.sub.A of the axis of rotation A and an orthoradial direction O, the cells 20, 50a, 50b comprising walls 22 which extend in a substantially radial direction R, the cells 20, 50a, 50b being distributed according to a first cell density in a first densified annular area Z.sub.51 of the abradable element, said densified annular area Z.sub.51 being located facing the radial end of the wiper, said densified annular area having an axial extent less than or equal to the axial extent of the radial end of the wiper, the cells being distributed according to a reference cell density outside said first area, the first density being greater than the reference density.

[0047] The walls 22 of the cells of the abradable element extend in a substantially radial direction means that the wall(s) 22 contributing in the definition of a cell is/are a surface which has a direction of elongation which is close to the radial direction R. A direction close to another direction means here that the angle separating the two directions is less than 2 degrees. The first densified annular area Z.sub.51 represented in FIG. 5 corresponds to cells 50b of the abradable element which are smaller in size than the cells 50a located outside this first densified annular area Z.sub.51, in the areas Z.sub.5R. It is therefore possible to place a larger number of cells per surface unit in the first densified annular area Z.sub.51 that is to say to obtain a first density greater than the reference density.

[0048] The densified annular area Z.sub.51 located facing the radial end of the wiper is reflected in FIG. 5 by the fact that along the axial direction A, the first densified annular area Z.sub.51 and the dotted line 59 are centered at the same position.

[0049] For example, the difference in position between the central axis of the first densified annular area Z.sub.51 and the central axis of the dotted line 59 can be chosen less than 0.5 mm, even a lower value.

[0050] The densified annular area Z.sub.51 can be characterized by its axial extent, that is to say the width of the area along the axial direction. This axial extent of the densified area is chosen to be less than or equal to the axial extent of the radial end of the wiper.

[0051] The technical effect associated with a higher cell density of the abradable element facing the wiper is to improve the tightness of the seal. The gas flow which attempts to flow between the abradable element 57 and the wiper from upstream to downstream of the turbomachine encounters more disturbance due to the greater number of present cells 50b.

[0052] A greater cell density of the abradable element further upstream or further downstream of the wiper does not substantially modify the tightness of the seal, so that it is not necessary for the densified annular area to present an axial extent greater than the axial extent of the radial end of the wiper.

[0053] FIG. 6 represents an abradable element 67 laid flat. The position of the end of a facing wiper has not been represented, but in this situation, the radial end of the wiper has an axial corrugation or deviations in the form of a regular circle.

[0054] As in the case of FIG. 5, the abradable element 67 includes a plurality of cells 60a, 60b disposed adjacent to each other along the direction D.sub.A of the axis of rotation A and an orthoradial direction O, the cells 60a, 60b being distributed according to a first cell density in a first densified annular area Z.sub.61 of the abradable element, said densified annular area Z.sub.61 being located facing the radial end of the wiper, the cells being distributed according to a reference cell density outside said first area Z.sub.61, the first density being greater than the reference cell density.

[0055] FIG. 6 proposes an abradable element of a labyrinth seal as presented above and in which, moreover, the cells 60a, 60b are further distributed according to respectively a second cell density and a third cell density in respectively a second densified annular area Z.sub.62 and a third densified annular area Z.sub.63 of the abradable element, each of the first, second and third densified annular areas Z.sub.61, Z.sub.62, Z.sub.63 being adapted to be located facing the radial end of the wiping during different flight phases of the aircraft, the second density and the third density each being greater than the reference density.

[0056] During the different flight phases, the turbomachine is more or less loaded so that the temperature and the expansion of the parts change within the turbomachine. Particularly, the temperature is lower in the “cold” phase, that is to say when the turbomachine is started, than in the “cruise” phase, that is to say when the turbomachine is in a mode that allows the flight. Likewise, the temperature is lower in the “cruise” phase than in the “climb” phase, that is to say when the turbomachine is in a mode that allows the take-off.

[0057] At the system formed by the abradable element and the wiper, the position of the wiper relative to the abradable element in the direction D.sub.A of the axis A of rotation changes depending on the flight phase. Three axial positions “cold”, “cruise” and “climb” of the wiper relative to the abradable element can be identified for each of the flight phases “cold”, “cruise” and “climb”, the axial position “cruise” being between the two other axial positions “cold” and “climb”.

[0058] In the situation where the abradable element has only one densified annular area, and if, while switching from a first flight phase to a second flight phase, the wiper is no longer located facing the densified annular area then the improvement in the tightness of the seal obtained during the first flight phase is lost during the second flight phase.

[0059] The technical effect associated with the presence of three densified annular areas located facing the three axial positions “cold”, “cruise” and “climb”, of the wiper is to maintain the improvement of the tightness of the seal during each of the three flight phases “cold”, “cruise” and “climb”.

[0060] The labyrinth seals proposed in this application have at least one densified annular area, whose axial extent can be more precisely defined. Particularly, it can be specified that the ratio between the axial extent of the densified annular area and the axial extent of the outer radial end is comprised between 40% and 100%.

[0061] The presence of a densified annular area located facing the outer radial end of the wiper allows improving the tightness of the seal. However, the greater number of walls within the abradable element that are present facing the wiper decreases the abradable nature or “abradability” of the abradable element. The abradable nature here corresponds to the fact that in the event of contact between the abradable element and the wiper, it is the abradable element that loses material and deteriorates on contact with the wiper and not vice versa.

[0062] Also, in order to set the extent of a densified annular area, there is a compromise between the abradability of the abradable element and the tightness of the seal. Particularly, the closer the axial extent of the densified annular area is to the axial extent of the outer radial end of the wiper, the more the tightness of the seal is improved and the less the abradable element has an abradable nature.

[0063] A ratio between the axial extent of the densified annular area and the axial extent of the outer radial end between 40% and 100% allows an interesting compromise between the abradability of the abradable element and the tightness of the seal.

[0064] Particularly, a ratio between 40% and 80% allows an interesting compromise for systems where the differential expansions are important and where the need for abradability is significant.

[0065] A ratio between 80 to 100% allows an interesting compromise when it is certain that the abradable element and the wiper do not or almost come into contact with each other and that the quality of the tightness can therefore be enhanced.

[0066] Different shapes can be chosen for the cells of the abradable element.

[0067] The honeycomb shape i.e. regular hexagon shape can be chosen.

[0068] Other geometric shapes can be chosen such as a disc, a square, a triangle or a rhombus.

[0069] It should be noted that part of the cells may be of a certain shape and another part of the cells may be of another shape.

[0070] In this manner, a labyrinth seal as presented above is proposed in which at least part of the cells has a honeycomb shape.

[0071] In this manner, a seal as presented above is proposed in which at least part of the cells has a disc, square, triangle or rhombus shape.

[0072] FIG. 7 represents an abradable element of a labyrinth seal as shown above, with areas Z.sub.7R where the cells of the abradable element are distributed according to the reference density. In these areas, the cells 70a have a honeycomb shape. The abradable element further includes three densified annular areas Z.sub.71 Z.sub.72 Z.sub.73. Each densified annular area corresponds to a different shape of cells.

[0073] In the area Z.sub.71 the cells 70b have a disc shape.

[0074] In the area Z.sub.72 the cells 70c have a shape given by the intersection of a periodic array of wavy lines.

[0075] In the area Z.sub.73 the cells 70d have a more complex and angular shape with many points where the shape has an acute cutting angle for its outline.

[0076] There is also proposed a method for manufacturing a labyrinth seal for a turbomachine, particularly of an aircraft, including a rotor element and a stator element extending around the rotor element, the rotor element being adapted to rotate relative to the stator element about an axis of rotation, the rotor element including an annular wiper having an outer radial end extending towards an abradable element carried by the stator element, the outer radial end of the annular wiper having a corrugation along the axial direction and a non-zero axial extent associated with the corrugation, the abradable element including a plurality of cells disposed adjacent to each other along the direction of the axis of rotation and an orthoradial direction, the cells comprising walls which extend in a substantially radial direction, the method including the following steps: [0077] manufacturing the wiper; [0078] manufacturing the abradable element including a first densified annular area located facing an outer radial end of the wiper, said densified annular area having a first cell density, said densified annular area having an axial extent less than or equal to the axial extent of the outer radial end of the wiper, the cells being distributed according to a reference density outside the first annular reference area less than the first cell density.

[0079] The manufacture of the abradable element may further include the manufacture respectively of a second densified annular area and of a third densified annular area of the abradable element, the cells being distributed according to respectively a second cell density and a third cell density, each of the first, second and third densified annular areas being located facing the outer radial end of the wiper during different flight phases of the aircraft, the second density and the third density each being greater than the reference density.

[0080] The method for manufacturing a labyrinth seal as just presented may further include the following steps: [0081] measuring the axial extent of the outer radial end of the wiper; [0082] determining an axial extent of at least one densified annular area comprised between 40% and 100% of the measurement of the axial extent of the outer radial end of the wiper.

[0083] The method for manufacturing a labyrinth seal as just presented may further include the determination of a cell density of at least one densified annular area by taking into account the measurement of the axial extent of the outer radial end of the wiper.

[0084] The manufacturing method can be adapted to manufacture cells of different honeycomb, disc, square, triangle or rhombus shapes.

[0085] As previously mentioned, there is a compromise between the abradability of the abradable element and the tightness of the seal to set the axial extent of a densified annular area.

[0086] Similarly to the axial extent of the densified annular area, the greater the cell density, the more the tightness of the seal is improved and the less the abradable element has an abradable nature.

[0087] It is possible to use the compromise between the abradability of the abradable element and the tightness of the seal to set the density of abradable cells.