Exhaust system for gas turbine

1. An exhaust system for channeling streams from a by-pass gas turbine, the system comprising:

a stream-channeling nozzle;

an exhaust casing for connecting the stream-channeling nozzle to the outlet of the gas turbine;

said stream-channeling nozzle comprising a primary nozzle including an upstream end fastened to the exhaust casing and a secondary nozzle placed around the primary nozzle and including an upstream end fastened to the exhaust casing;

means for fastening the secondary nozzle directly to the exhaust casing at the upstream end of the secondary nozzle, said secondary nozzle being supported by the exhaust casing independently of the primary nozzle, said means for fastening comprising a plurality of connection elements distributed around the upstream end of the secondary nozzle, said connection elements being fastened to the inner wall of the secondary nozzle and to a flange of the exhaust casing; and

a plurality of flexible connection elements distributed around the upstream end of the primary nozzle, said flexible connection elements being fastened to the outer wall of the primary nozzle and to the flange of the exhaust casing.

2. An exhaust system according to claim 1 , characterized in that the primary nozzle is made of a ceramic matrix composite material.

3. An exhaust system according to claim 1 , characterized in that at least a portion of a flexible connection element of the primary nozzle is engaged with a connection element of the secondary nozzle in such a manner that orifices for fastening to the flange of the exhaust casing in said elements are aligned with one another.

4. An exhaust system according to claim 1 , characterized in that the secondary nozzle is made up of an upstream secondary nozzle fastened at the upstream end to the exhaust casing, and a downstream secondary nozzle connected to a downstream end of the upstream secondary nozzle that is opposite from the upstream end fastened to the exhaust casing.

5. An exhaust system according to claim 4 , characterized in that the upstream secondary nozzle is made of a metallic material and the downstream secondary nozzle is made of a ceramic matrix composite material.

6. An exhaust system according to claim 5 , characterized in that the edge portion of the upstream secondary nozzle and the edge portion of the downstream secondary nozzle are engaged one in the other with little or no clearance, and in that one of the two secondary nozzles presents along an engagement edge a succession of tongues that are separated from one another by slots and that are formed integrally with said one of the secondary nozzles, said secondary nozzles being assembled together by being mutually fastened via at least some of the tongues.

7. An exhaust system according to claim 6 , characterized in that the tongues are formed in the upstream secondary nozzle.

8. A by-pass gas turbine for an aeroengine, the gas turbine including an exhaust system according to claim 1 .

9. An exhaust system according to claim 1 , wherein:

the primary nozzle is made of a ceramic matrix composite material;

at least a portion of a flexible connection element of the primary nozzle is engaged with a connection element of the secondary nozzle in such a manner that orifices for fastening to the flange of the exhaust casing in said elements are aligned with one another;

the secondary nozzle is made up of an upstream secondary nozzle fastened at the upstream end to the exhaust casing, and a downstream secondary nozzle connected to a downstream end of the upstream secondary nozzle that is opposite from the upstream end fastened to the exhaust casing;

the upstream secondary nozzle is made of a metallic material and the downstream secondary nozzle is made of a ceramic matrix composite material;

the edge portion of the upstream secondary nozzle and the edge portion of the downstream secondary nozzle are engaged one in the other with little or no clearance, and in that one of the two secondary nozzles presents along its engagement edge a succession of tongues that are separated from one another by slots and that are formed integrally with said one of the secondary nozzles, said secondary nozzles being assembled together by being mutually fastened via at least some of the tongues; and

the tongues are formed in the upstream secondary nozzle.

10. A by-pass gas turbine for an aeroengine, the gas turbine including an exhaust system according to claim 9 .

11. An assembly method for assembling an exhaust system for channeling the streams from a by-pass gas turbine, the system comprising a stream-channeling nozzle and an exhaust casing for connection to the channeling nozzle at the outlet from the gas turbine, said stream-channeling nozzle comprising a primary nozzle including an upstream end fastened to the exhaust casing and a secondary nozzle placed around the primary nozzle and including an upstream end fastened to the exhaust casing,

the method being characterized in that the secondary nozzle is fastened directly to the exhaust casing at the upstream end of the secondary nozzle so as to support said secondary nozzle via the exhaust casing independently of the primary nozzle, wherein a plurality of connection elements are placed around the upstream end of the secondary nozzle, said connection elements being fastened to the inner wall of the secondary nozzle and to a flange of the exhaust casing; and

a plurality of flexible connection elements are placed around the upstream end of the primary nozzle, said flexible connection elements being fastened to the outer wall of the primary nozzle and to the flange of the exhaust casing.

12. An assembly method according to claim 11 , characterized in that the primary nozzle is made of a ceramic matrix composite material.

13. An assembly method according to claim 11 , characterized in that at least a portion of a flexible connection element of the primary nozzle is engaged with a connection element of the secondary nozzle in such a manner that orifices for fastening to the flange of the exhaust casing in said elements are aligned with one another.

14. An assembly method according to claim 11 , characterized in that the secondary nozzle is made up of an upstream secondary nozzle fastened at the upstream end to the exhaust casing, and a downstream secondary nozzle connected to a downstream end of the upstream secondary nozzle that is opposite from the upstream end fastened to the exhaust casing.

15. An assembly method according to claim 14 , characterized in that the upstream secondary nozzle is made of a metallic material and the downstream secondary nozzle is made of a ceramic matrix composite material.

16. An assembly method according to claim 15 , characterized in that the edge portion of the upstream secondary nozzle and the edge portion of the downstream secondary nozzle are engaged one in the other with little or no clearance, and in that a succession of tongues that are separated from one another by slots are formed along the engagement edge of one of the two secondary nozzles, the slots being obtained by cutting out or machining the material of said one of the secondary nozzles, and the secondary nozzles are assembled together by fastening at least some of the tongues to the edge portion of the other secondary nozzle.

17. An assembly method according to claim 16 , characterized in that the tongues are formed in the edge portion of the upstream secondary nozzle.

18. An assembly method according to claim 11 , characterized in that:

the primary nozzle is made of a ceramic matrix composite material;

at least a portion of a flexible connection element of the primary nozzle is engaged with a connection element of the secondary nozzle in such a manner that orifices for fastening to the flange of the exhaust casing in said elements are aligned with one another;

the secondary nozzle is made up of an upstream secondary nozzle fastened at the upstream end to the exhaust casing, and a downstream secondary nozzle connected to a downstream end of the upstream secondary nozzle that is opposite from the upstream end fastened to the exhaust casing;

the upstream secondary nozzle is made of a metallic material and the downstream secondary nozzle is made of a ceramic matrix composite material;

the edge portion of the upstream secondary nozzle and the edge portion of the downstream secondary nozzle are engaged one in the other with little or no clearance, and in that a succession of tongues that are separated from one another by slots are formed along the engagement edge of one of the two secondary nozzles, the slots being obtained by cutting out or machining the material of said one of the secondary nozzles, and the secondary nozzles are assembled together by fastening at least some of the tongues to the edge portion of the other secondary nozzle; and

the tongues are formed in the edge portion of the upstream secondary nozzle.