Sealing ring element for a turbine comprising an inclined cavity in an abradable material

Abstract

A sealing ring element of a turbomachine includes: a sealing portion with a first area and a second area, with the inner surface of a first area being at the same radial distance from the axis of the turbomachine. The sealing portion includes an annular cavity which opens into an inner surface of the second area and extends into the first area, the annular cavity defining an upstream lateral wall and/or a downstream lateral wall forming an angle which is strictly between 0 and 90°.

Claims

1. A seal for a turbomachine, used to provide the seal between first and second elements of the turbomachine in rotation with respect to one another and being of revolution about an axis of the seal comprising: a wiper, annular about the axis of the seal, intended to be supported by the second element of the turbomachine; and a sealing ring element of the turbomachine arranged about a turbomachine axis, the sealing ring element being annular about the axis of the seal and intended to be supported by the first element of the turbomachine, the sealing ring element being made from an abradable material and comprising a sealing portion able to engage with the wiper, said sealing portion comprising a first area and a second area adjacent to the first area in a direction of the turbomachine axis, with an inner surface of the first area being at a same radial distance from the turbomachine axis for any sealing surface portion of the first area, and an annular cavity formed in the abradable material by machining the second area and which opens into an inner surface of the second area and extends into the first area, the inner surface of the second area being defined by a bottom wall of the annular cavity and disposed radially outward of the inner surface of the first area, the bottom wall of the annular cavity being parallel to the axis of the seal, and the annular cavity defining at least one of an upstream lateral wall or a downstream lateral wall connected to the bottom wall and forming an angle with the inner surface of the first area strictly between 0 and 90°, in such a way that a portion of the abradable material of the first area is radially superimposed on a portion of the annular cavity such that the portion of the abradable material and the portion of the annular cavity overlap each other, and an end point of the first area overlaps the inner surface of the second area, wherein said wiper comprises a downstream lateral wall, intended to come opposite the downstream lateral wall of said annular cavity, and, through observation as an axial section, an angle formed between a plane of the downstream lateral wall of the annular cavity and a plane along which extends the inner surface of the first area associated with said annular cavity being greater than or equal to an angle formed between a plane along which extends the downstream lateral wall of said wiper and the plane along which extends the inner surface of the first area associated with said annular cavity, in such a way that said wiper can penetrate into said annular cavity without blocking the annular cavity during reignition of the turbomachine.

2. The seal according to claim 1, wherein at least one of the upstream lateral wall or the downstream lateral wall extends respectively, through observation as the axial section, along an upstream axis of the annular cavity and along a downstream axis of the annular cavity that are not perpendicular to the turbomachine axis of the turbomachine, and wherein the abradable material comprises an upstream lateral wall and a downstream lateral wall extending respectively, through observation as an axial section, along an upstream axis of the abradable material and a downstream axis of the abradable material parallel to the upstream axis of the annular cavity and/or the downstream axis of the annular cavity.

3. The seal according to claim 2, wherein the abradable material is a honeycomb material, with cells of the honeycomb being oriented along at least one of the upstream axis of the annular cavity or the downstream axis of the annular cavity.

4. The seal according to claim 1, wherein said annular cavity is formed over an entire circumference of the abradable material about the turbomachine axis.

5. The seal as claimed in claim 1, wherein said annular cavity is formed at an internal periphery of the abradable material and opens radially inwards.

6. A turbine of a gas turbine engine, comprising a seal according to claim 1, said first area of said sealing portion corresponding to a nominal operation zone of the turbine and said second area of said sealing portion corresponding to an operation zone in a reignition phase after an extinction of a combustion chamber.

7. A turbomachine comprising a turbine according to claim 6.

8. The seal according to claim 1, wherein the second area of the sealing portion is disposed downstream of the first area of the sealing portion.

9. The seal according to claim 1, wherein the wiper is only opposite of the first area during normal operation of the turbomachine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be understood better when reading the following detailed description of non-limiting embodiments of the latter, as well as the examination of the figures, diagrammatical and partial, of the annexed drawing, wherein:

(2) FIG. 1 shows, as a partial axial cross-section, an example of a low-pressure turbine of a gas turbine engine representative of the technical context of the invention,

(3) FIG. 2 shows, very diagrammatically as a partial cross-section, a known embodiment of a stator sealing element of a labyrinth seal,

(4) FIGS. 3 and 4 show, very diagrammatically as a partial cross-section, two embodiments of stator sealing elements of a labyrinth seal in accordance with the invention,

(5) FIG. 5 is a view similar to that of FIG. 4 and makes it possible to show the operating principle of a sealing element according to the invention, and

(6) FIG. 6 is a view similar to that of FIG. 4 and makes it possible to show the configuration of the cavity of a sealing element according to the invention opposite that of a corresponding wiper.

(7) In all of these figures, identical references can designate identical or similar elements.

(8) In addition, the various portions shown in the figures are not necessarily shown according to a uniform scale, in order make the figures more legible.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(9) In all of the description, it is noted that the terms upstream and downstream are to be considered in relation to a main direction F, shown in FIG. 1, of the normal flow of gas (in a downstream direction) for a turbomachine. Moreover, the axis X of the seal or of the turbomachine refers to the radial axis of, the axis of radial symmetry of the seal or of the turbomachine. The axial direction of the seal corresponds to the direction of the X axis of the seal. A radial direction of the seal is a direction perpendicular to the X axis of the seal. Furthermore, unless mentioned otherwise, the adjectives and adverbs axial, radial, axially and radially are used in reference to the aforementioned axial and radial directions. In addition, unless mentioned otherwise, the terms inner and outer are used in reference to a radial direction in such a way that the inner portion of an element is closer to the X axis of the seal than the outer portion of the same element.

(10) FIGS. 1 and 2 were described hereinabove in the portion relative to prior art and in the technical context of the invention.

(11) In reference to FIGS. 3 to 6, embodiments of a sealing ring element 6s of a labyrinth seal in accordance with the invention shall now be described. In these examples, the sealing ring element 6s is of the stator type. It forms a labyrinth seal in association with two annular wipers 2l about the axis X of the labyrinth seal. However, these choices are in no way limiting.

(12) As can be seen in these FIGS. 3 to 6, the sealing ring element 6s comprises an abradable material with two sealing surface portions 6p, with each one able to engage with a corresponding wiper 2l.

(13) Each sealing portion 6p axially comprises a first area 6p1 with a first wiper penetration resistance 2l and a second area 6p2, adjacent to the first area 6p1 and located downstream from the latter, with a wiper penetration resistance 2l that is reduced with respect to the first area 6p1.

(14) In other words, the second area 6p2 makes through it configuration the first area 6p1 more resistant to wiper penetration in the radial direction.

(15) In addition, as can be seen in these FIGS. 3 to 6, the inner surface 6i of the first areas 6p1 is at the same radial distance from the axis X of the labyrinth seal for the two sealing surface portions 6p. In other words, the abradable material is advantageously not of the “staged” type.

(16) Moreover, in accordance with the invention, each second area 6p2 comprises an annular cavity 6c, formed in the abradable material, in particular by machining.

(17) The first upstream cavity 6c comprises an upstream lateral wall 6m and a downstream lateral wall 6v extending respectively, through observation as an axial section, along an upstream axis of the cavity Cm and along a downstream axis of the cavity Cv. These lateral upstream 6m and downstream 6v walls are connected by a bottom wall 6f of this first upstream cavity 6c.

(18) The second downstream cavity 6′c comprises only an upstream lateral wall 6m extending along an upstream axis of the cavity Cm, connected to a bottom wall 6f.

(19) In other words, the first upstream cavity 6c opens onto the inner periphery of the abradable material, and the second downstream cavity 6′c also opens onto the inner periphery of the abradable material and also onto its downstream lateral wall 7v.

(20) Advantageously, the upstream cavity axis Cm and downstream cavity axis Cv are not perpendicular to the X axis of the labyrinth seal. In particular, they are here parallel to each other and form an angle α with the axis Ci along which extends the inner surface 6i of the first areas 6p1 which is strictly between 0 and 90°, being for example between 30 and 60°. In this way, a portion P1 of the abradable material of the first areas 6p1 is superimposed radially on a portion P2 of the cavities 6c, 6′c of the second areas 6p2.

(21) In addition, the axes according to which extend the bottom walls 6f of the cavities 6c, 6′c are advantageously parallel to the X axis of the labyrinth seal.

(22) As such, in order to solve the problem of rotor lock while still preserving the performance of the engine during operation, the invention implements a solution of a cavity or notch that is inclined or encore bevelled.

(23) In the example of FIG. 3, the lateral upstream 7m and downstream 7v walls of the abradable material are perpendicular to the X axis of the labyrinth seal.

(24) However, as the abradable material is advantageously of the honeycomb type, carrying out cells of the honeycomb in an inclined manner is preferable in order to obtain an optimum resistance of the abradable material. Then, it is also preferable to carry out lateral walls 7m and 7v of the abradable material in an inclined manner.

(25) As such, FIG. 4 shows the configuration of the sealing ring element 6s wherein the lateral upstream 7m and downstream 7v walls of the abradable material have the same inclination, in relation to the X axis of the labyrinth seal, as that of the cavities 6c and as that of the cells of the honeycomb. The choice of having meshes according to this slope for the honeycomb makes it possible to facilitate the machining of the cavities 6c. In addition, choosing a slope of inclined meshes that is similar to that of the cavities 6c makes it possible to not lose in performance, for example via air leaks through the cells, contrary to solutions that would consider only the carrying out of holes in the abradable material. There is no loss of performance if the angle of inclination of the honeycomb is at most equal to the angle α. If the angle of inclination of the honeycomb is lower than the angle α, there is no impact on performance.

(26) FIG. 5 makes it possible to show the operating principle of the invention. Indeed, thanks to the invention, it is possible, during normal operation, to retain the performance of the engine because the wipers 2l will be opposite the non-machined abradable material, in other words a portion of the abradable material devoid of the presence of an annular cavity 6c, and therefore with an optimum resistance to the passage of air, which corresponds to the plot T1 as a dotted line in FIG. 5.

(27) On the other hand, during a reignition, the wiper 2l will pass through only the tip of the abradable material, as shown by the plot T2 as a solid line in FIG. 5, and break it without causing any rotor lock phenomenon. During the return to normal operation, the loss of performance will then be only the opening due to the loss of the abradable material peak broken.

(28) It is moreover to be noted that the invention makes it possible to easily create two cavities or more on the abradable material, in particular by machining, with the same diameter, without having to make use of a solution of the staged abradable type.

(29) In addition, the carrying out of the cavities 6c is done over 360° in the abradable material.

(30) Advantageously, the slope of the machining of an annular cavity 6c must be sufficient to allow for the rupture of the abradable material during a reignition and to allow the wiper 2l to go into the annular cavity 6c without blocking it. As such, the number of cavities 6c advantageously corresponds to the number of wipers 2l opposite. Further more precisely, the slope downstream from the annular cavity 6c must be at least equal to the slope of the wiper 2l in order to allow the latter to go to the cavity bottom as shown in FIG. 6. In other words, through observation as an axial section, the angle α formed between the downstream axis of the cavity Cv and the axis Ci along which extends the inner surface 6i of the first area 6p1 associated with the annular cavity 6c is greater than or equal to the angle β formed between the axis Lv along which extends the downstream lateral wall 2v of the wiper 2l and the axis Ci, in such a way that the wiper 2l can penetrate into the annular cavity 6c.

(31) Moreover, the depth of the annular cavities 6c, in other words the distance between the axis Ci and the bottom walls 6f such as shown for example in the FIGS. 3 and 4, can in particular be determined by the predicted wear during a restarting in windmilling phase.

(32) Consequently, the solution proposed by the invention makes it possible to have an operability found in reignition mode while still avoiding the risk of rotor lock, and also makes it possible to not degrade the performance in nominal operation.

(33) Of course, the invention is not limited to the embodiments that have just been described. Various modifications can be made thereto by those skilled in the art.