TURBINE FOR A TURBINE ENGINE

Abstract

A turbine for a turbine engine extending along an axis includes an annular casing and at least one turbine stage having a nozzle and a rotor impeller wheel surrounded by a sealing ring with an abradable element. The impeller wheel and the sealing ring are located downstream of the nozzle, and the sealing ring has an upstream end held on the casing by locking means. The turbine includes elastic sealing means in contact with the locking means as well as with the nozzle or the casing so as to press the locking means against the sealing ring. The locking means includes a radially outer portion with a C-shaped cross-section and a radial portion extending radially inwards from the outer portion. The sealing means include two elastic seals bearing on the radial portion, respectively on either side of the radial portion.

Claims

1. A turbine for a turbine engine extending along an axis, including an annular casing and at least one turbine stage comprising a nozzle and a rotor impeller wheel surrounded by a sealing ring including an abradable element, the impeller wheel and the sealing ring being located downstream from the nozzle, the sealing ring including an upstream end held on the casing by locking means, elastic sealing means in contact with the locking means as well as with the nozzle or the casing so as to press the locking means against the sealing ring, the locking means including a radially outer portion with a C-shaped cross-section and a radial portion extending radially inward from the outer portion, the sealing means including two elastic seals bearing on said radial portion, respectively, on either side of the radial portion.

2. The turbine according to claim 1, wherein the sealing means further include at least one axially deformable annular seal.

3. The turbine according to claim 1, wherein the locking means further include a portion with a C-shaped cross-section.

4. The turbine according to claim 3, wherein the sealing means further include at least one additional annular seal located radially inside the radially outer portion with the C-shaped cross-section and which is in contact against the sealing ring as well against the nozzle or the casing.

5. The turbine according to, claim 1, wherein the sealing ring further includes a portion extending axially in an upstream direction, located at least partially facing at least one of the locking means and the sealing means.

6. The turbine according to claim 1, wherein the sealing ring is sectorized and includes a plurality of sectors arranged end-to-end on a circumference about the axis, sealing elements extending between the ends of the circumferentially adjacent ring sectors.

7. The turbine according to claim 5, wherein the sealing ring is sectorized and includes a plurality of sectors arranged end-to-end on a circumference about the axis, sealing elements extending between the ends of the circumferentially adjacent ring sectors, the sealing elements being located at least in said portion of the sealing ring extending axially in the upstream direction.

8. The turbine according to claim 1, wherein the nozzle includes a radially outer shell and a radially inner shell, connected by radial blades, the outer shell including at least one downstream edge extending radially outward from the outer shell and mounted on the casing, said edge extending axially, at least partially, facing the locking means.

9. The turbine according to claim 1, wherein the nozzle includes a radially outer shell and a radially inner shell connected by radial blades, the outer shell including at least one downstream edge extending radially outward from the outer shell and mounted on the casing, the radially outer end of said downstream edge being located radially inside the locking means.

10. The turbine according to claim 1, wherein the sealing ring includes a tab held radially bearing and axially bearing on a portion of the casing, by the locking means.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0102] FIG. 1 is an axial sectional half-view of a turbine engine turbine,

[0103] FIG. 2 is a sectional view of a portion of the turbine according to the prior art,

[0104] FIG. 3 is a sectional view of a portion of the turbine according to a first embodiment of the invention,

[0105] FIG. 4 is a sectional view of a portion of the turbine according to a second embodiment of the invention,

[0106] FIG. 5 is a sectional view of a portion of the turbine according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0107] FIG. 3 illustrates a portion of a turbine 1 according to a first embodiment of the invention. The latter includes an annular casing 4 and at least one turbine stage comprising a nozzle 2 and an impeller wheel 5 surrounded by a sealing ring 10, the impeller wheel 5 and the ring 10 being located downstream from the nozzle 2.

[0108] The nozzle 2 is sectorized. The outer shell 16 of the nozzle 2 includes an upstream edge 31 (seen in FIG. 4) and a downstream edge 21 each extending radially outward from the outer shell 16.

[0109] The radially inner surface 32 of the outer shell 16 is frustoconical and flares in the downstream direction. This surface 32 is intended to delimit the gas flow jet 17 in the turbine 1.

[0110] The upstream edge 31 is mounted on an upstream rail 32 of the casing 4. Similarly, the downstream edge 21 is mounted on a downstream rail 24 of the casing 4.

[0111] The casing 4 includes two portions, respectively upstream 4a and downstream 4b, each comprising a frustoconical wall and a fastening clamp 33, 34.

[0112] The upstream portion 4a of the casing 4 surrounds the nozzle 2. The downstream portion 4b of the casing 4 surrounds the sealing ring 10 and the impeller wheel 5.

[0113] The two portions 4a, 4b are fastened to one another at the clamps 33, 34. Each rail 32, 24 extending radially inside the frustoconical wall of the first portion 4a. Each rail 32, 24 extends in the downstream direction from said frustoconical wall.

[0114] The radially outer end of the upstream edge 31 radially bears on a radially outer cylindrical surface of the upstream rail 32 of the first portion 4a.

[0115] A portion of the downstream edge 21, for example the radially outer end 22, radially bears on a downstream rail 24 of the casing 4. In particular, the downstream edge 21 includes an axial portion 22 extending in the upstream direction from a radial portion of said downstream edge 21, said axial portion 22 being engaged by shape complementarity in a groove 23 provided in the casing 4 and forming the downstream rail 24.

[0116] The second portion 4b of the casing 4 includes an upstream rail 20 for mounting an upstream tab 18 of the sealing ring 10. The portion 4b of the casing 4 furthermore includes a downstream rail 26 for mounting a downstream zone of the sealing ring 10.

[0117] The upstream rail 20 extends axially in the upstream direction. The downstream zone of the sealing ring 10 includes a cylindrical surface bearing on a complementary cylindrical surface of the downstream rail 26.

[0118] The sealing ring 10 includes a radially outer support 13 and a radially inner block of abradable material 14, fastened to the support 13.

[0119] The sealing ring 10 is sectorized. Sealing elements 36, for example strips or foils, are engaged in slots provided at the circumferential ends of the sectors of the sealing ring 10.

[0120] The sealing elements 36 extend along most of the axial dimension of the sectors, for example along at least 50%, preferably at least 80% of said axial dimension.

[0121] The sealing ring 10 includes a radially inner surface including at least an upstream cylindrical zone 37 and a downstream cylindrical zone 38, the diameter of the upstream zone 37 being less than the diameter of the downstream zone 38.

[0122] Each vane 8 of the impeller wheel 5 includes an outer platform 39 from which at least an upstream strip 40 and a downstream strip 41 extend radially outward. The outer platform 39 is frustoconical and flares in the downstream direction. The upstream strip 40 cooperates with the upstream cylindrical zone 37 of the sealing ring 10, the downstream strip 41 cooperating with the downstream cylindrical zone 38.

[0123] The turbine 1 includes at least one locking member 12, for example several locking members 12 regularly distributed along the circumference, each locking member 12 including a generally C-shaped locking zone 12a.

[0124] The locking zone 12a includes a radially outer axial branch 42 and a radially inner axial branch 43, connected by a radial base 44. The radially outer branch 42 bears radially on the radially outer surface of the corresponding upstream rail 20 of the casing 4. The radially inner branch 43 bears on an upstream tab 18 of the sealing ring 10. The inner 43 and outer 42 branches make it possible to keep the tab 18 bearing on the corresponding upstream rail 20. The base 44 bears on the upstream end 18 of the tab, so as to press said upstream end of the tab 18 on the upstream end of the corresponding upstream rail 20 of the casing 4.

[0125] The tab 18 of the sealing ring 10 includes a portion 18a extending axially in the upstream direction from a main zone of the sealing ring 10, said axial portion 18a radially bearing on the corresponding upstream rail 20 of the casing 4. The tab 18 furthermore includes a portion 18b extending radially outward from the upstream end of said radial portion 18a of the tab 18. Said radial portion 18b is capable of bearing on the upstream end of the upstream rail 20 of the casing 4.

[0126] The locking member 12 includes a positioning or centering zone 12b extending radially inward from the locking zone 12a.

[0127] The locking zone 12a and the positioning zone 12b are formed from one piece or, on the other hand, from at least two pieces fastened to one another. The positioning zone 12b includes a portion 45 extending radially inward from the locking zone 12a and a cylindrical portion 46 extending axially on either side of the radially inner end of said radial portion 45.

[0128] A first annular sealing member 48 extends axially between a radial face of the downstream edge 21 of the nozzle 2 and the positioning zone 12b. A second annular sealing member 49 extends axially between the positioning zone 12b and a radial face of the sealing ring 10. The first annular member 48 and/or the second annular member 49 are elastically deformable in the axial direction. The first annular member 48 and/or the second annular member 49 have a generally omega- or W-shaped cross-section.

[0129] An annular edge 50 edge extends axially in the downstream direction from the downstream edge 21 of the nozzle 2. An annular edge 51 edge extends axially in the downstream direction from the sealing ring 10. The edges 50, 51 are located radially outside the sealing members 48, 49.

[0130] The sealing ring 10 includes a portion 52 extending axially in the upstream direction, located at least partially facing the sealing members 48, 49 and the locking member 12. The sealing elements 36 also extend in the axial portion 52.

[0131] It will be noted that holes or bores 21a, 45a and 18c are formed respectively in the downstream edge 21, the radial portion 45 and the upstream tab 18, these holes or bores allowing the flow of a cooling or ventilation air stream.

[0132] The sealing members 48, 49 and the sealing elements 36 ensure sealing on the entire circumference, unlike the discontinuous sealing means, as they are sectorized and have no circumferential overlap, of the prior art. These sealing members and elements 48, 49, 36 also make it possible to protect the locking means 12a due to the radially inner position thereof in relation to said locking means 12a. In particular, they make it possible to limit the heating of the locking means 12a by a hot gas leakage flow from the gas flow jet 17 from the combustion chamber and passing through the turbine 1.

[0133] Moreover, such a structure is adapted for a mounting of the elements cited above of the turbine 1 via the upstream.

[0134] FIG. 4 illustrates a second embodiment of the invention, which differs from that described above with reference to FIG. 3 by the features described hereinafter. In this embodiment, the locking member 12 only includes a C-shaped locking zone 12a.

[0135] A first annular sealing member 48 extends axially between the base 44 of the locking member 12 and a radial face of the casing 4. A second sealing member 49 extends axially between a radial face of the sealing ring 10 and a radial face of the casing 4. The first sealing member 48 is housed in a groove 53 of the casing 4. The first sealing member 48 and the second sealing member 49 are axially offset in relation to each other.

[0136] The radially outer end of the downstream edge 21 of the nozzle 2, formed by the axial portion 22, is located radially inside the first sealing member 48, the second sealing member 49 and the locking member 12. Some portions can be scalloped, i.e. include hollow zones, in order to facilitate air flow. Holes or bores 4b and 18c are formed respectively in the casing and the upstream tab 18, these holes or bores allowing the flow of a cooling or ventilation air stream.

[0137] FIG. 5 illustrates a third embodiment, which differs from those described above with reference to FIGS. 3 and 4 in that an intermediate element 54 is mounted on the casing 4 downstream from the downstream edge 21 of the nozzle 2. The intermediate element 54 is positioned in relation to the downstream edge 21 by means of at least one positioning or centering block 55. Said intermediate element 54 extends radially. The radially outer periphery of the intermediate element 54 is fastened between the radial clamp 33 of the first portion 4a of the casing 4 and the radial clamp 34 of the second portion 4b of the casing 4.

[0138] The intermediate element 54 includes an axial edge 56 extending in the upstream direction, radially bearing on a cylindrical surface of the casing 4.

[0139] An annular sealing member 57 is mounted between the downstream edge 21 and the intermediate element 54. Said sealing member 57 is mounted in a groove 58 of the intermediate element 54. The first sealing member 48 and the second sealing member 49 are located in the same radial plane. It is possible to place a groove on the intermediate element 54 if it is sought to use an Omega type seal.

[0140] Holes or bores 54a and 18c are respectively formed in the intermediate element 54 and the upstream tab 18, these holes or bores allowing the flow of a cooling or ventilation air stream.