Cooling device for a stationary ring of a gas turbine

1. A cooling device for a stationary ring surrounding a gas-turbine hot-gas flow path, said ring being made up of a plurality of ring segments that are fastened by upstream and downstream fastener systems onto a plurality of spacer segments forming a stationary annular support spacer surrounding said ring so as to co-operate therewith to define at least one annular impact cavity into which at least one cooling-air supply orifice opens out, each ring segment having walls that are pierced with a plurality of air exhaust holes opening out both into the impact cavity, and into the hot-gas flow path, the device further comprising a cooling circuit configured to channel the air coming from leakage through the seals of the fastener systems that fasten together the ring and spacer segments, and to direct, without reducing said leakage, said air towards at least one of the axial ends of the ring segments in contact with the hot gas so as to cool said at least one of the axial ends,

wherein said cooling circuit defines axial air flow paths for each upstream fastener system and/or downstream fastener system, said axial air flow paths being defined by recesses formed:

(a) for each upstream fastener system, in a radially inner surface of an outer upstream hook of each ring segment and/or in a radially outer surface of an inner upstream hook of each spacer segment, and

(b) for each downstream fastener system, in a radially inner surface of an outer downstream hook of each ring segment and/or in a radially outer surface of an inner branch of a clip surrounding the outer downstream hook.

2. A device according to claim 1 , wherein each upstream fastener system comprises:

an upstream notch of a ring segment that is radially defined between an upstream tip in contact with the hot gas, and said outer upstream hook; and

said inner upstream hook of a spacer segment onto which the ring segment is fastened, said inner upstream hook being axially engaged in said upstream notch of the ring segment,

wherein, at each upstream fastener system, the device includes an upstream circuit for channeling the air coming from leakage through the seals, and for directing said air towards the upstream tips of the ring segments so as to cool the upstream tips.

3. A device according to claim 2 , wherein the upstream circuit comprises at least one axial air flow path opening out both into an upstream circumferential space that is radially defined between the inner upstream hooks and the axial walls of the spacer segments, and into the upstream notches of the ring segments that are fastened onto said spacer segments.

4. A device according to claim 3 , wherein the upstream circuit comprises a plurality of axial air flow paths that are evenly spaced apart around its circumference.

5. A device according to claim 3 , wherein the air flow paths are formed in the outer upstream hooks of the ring segments.

6. A device according to claim 3 , wherein the air flow paths are formed in the inner upstream hooks of the spacer segments.

7. A device according to claim 1 , wherein each downstream fastener system comprises:

a downstream notch of a ring segment that is radially defined between a downstream tip in contact with the hot gas, and said outer downstream hook;

said outer downstream hook of a spacer segment onto which the ring segment is fastened, said outer downstream hook of the spacer segment bearing radially against said outer downstream hook of the ring segment; and

said clip surrounding the outer downstream hooks of the spacer and ring segments;

wherein, at each downstream fastener system, the device includes a downstream circuit for channeling the air coming from leakage through the seals, and for directing said air towards the downstream tips of the ring segments so as to cool the downstream tips.

8. A device according to claim 7 , wherein the downstream circuit comprises at least one axial air flow path opening out both into a downstream circumferential space that is radially defined between the outer downstream hooks of the ring and spacer segments, and into the downstream notches of the ring segments.

9. A device according to claim 8 , wherein the downstream circuit comprises a plurality of axial air flow paths that are evenly spaced apart around its circumference.

10. A device according to claim 8 , wherein the air flow paths are formed in the outer downstream hooks of the ring segments.

11. A device according to claim 8 , wherein the air flow paths are formed in the inner branches of the clips.

12. A stationary ring surrounding a gas-turbine hot-gas flow path, the stationary ring including a cooling device according to claim 1 .

13. A device according to claim 1 , wherein said cooling circuit defines said axial air flow paths for each upstream fastener system.

14. A device according to claim 13 , wherein said axial air flow paths are defined by recesses formed in said radially inner surface of said outer upstream hook of each ring segment.

15. A device according to claim 13 , wherein said axial air flow paths are defined by recesses formed in said radially outer surface of said inner upstream hook of each spacer segment.

16. A device according to claim 13 , wherein said cooling circuit defines said axial air flow paths for each downstream fastener system.

17. A device according to claim 1 , wherein said cooling circuit defines said axial air flow paths for each downstream fastener system.

18. A device according to claim 17 , wherein said axial air flow paths are defined by recesses formed in said radially inner surface of said outer downstream hook of each ring segment.

19. A device according to claim 17 , wherein said axial air flow paths are defined by recesses formed in said radially outer surface of said inner branch of said clip surrounding the outer downstream hook.