Device for controlling clearance in a gas turbine

1. A device for controlling clearance between the tips of rotary blades and a stationary ring assembly in a gas turbine, said device comprising a circular control box surrounding said stationary ring assembly,

wherein said control box comprises:

at least two annular air circulation strips spaced apart from each other in the axial direction and each having a plurality of perforations for modifying the temperature of the stationary ring assembly by discharging air;

an annular air feed channel radially spaced from said air circulation strip;

at least one air duct for feeding said feed channel with air; and

a plurality of hollow distribution spacers connecting said air feed channel to said air circulation strips in order to feed the strips with air while allowing the air that has been discharged against the stationary ring assembly to flow between said feed channel and said circulation strips in order to be exhausted therefrom.

2. A device according to claim 1 , wherein the stationary ring assembly comprises an inner casing which is surrounded by an outer casing of the gas turbine so as to define an annular chamber in which said control box is mounted.

3. A device according to claim 2 , wherein said control box bears in leaktight manner at an upstream axial end against the outer casing, and at a downstream axial end against the inner casing so as to define, inside said angular chamber, an air discharge upstream enclosure and an air exhaust downstream enclosure that is air-tight relative to said upstream enclosure.

4. A device according to claim 3 , wherein said inner casing presents an air opening at a downstream axial end, opening out into the air exhaust downstream enclosure in order to exhaust the air that has been discharged against the stationary ring assembly.

5. A device according to claim 2 , wherein the inner casing includes annular fins, and wherein the air circulation strips match substantially the shape of said fins.

6. A device according to claim 1 , wherein said control box is made up of at least two distinct angular box sectors.

7. A device according to claim 1 , wherein the hollow distribution spacers connecting the feed channel to one of the air circulation strips are angularly offset relative to the hollow distribution spacers connecting said feed channel to at least one of the other air circulation strips.

8. A device according to claim 1 , wherein the hollow distribution spacers connecting the feed channel to one of the air circulation strips are angularly aligned relative to the hollow distribution spacers connecting said feed channel with the other air circulation strips.

9. A device according to claim 1 , wherein the angular spacing between two successive hollow distribution spacers does not exceed about 45°.

10. A turbomachine including a device according to claim 1 .

11. A device for controlling clearance between the tips of rotary blades and a stationary ring assembly in a gas turbine, said device comprising a circular control box surrounding said stationary ring assembly, said control box comprising:

at least two annular air circulation strips spaced apart from each other in the axial direction and each having a plurality of perforations for modifying the temperature of the stationary ring assembly by discharging air;

an annular air feed channel radially spaced from said air circulation strip;

at least one air duct for feeding said feed channel with air; and

a plurality of spacing means for connecting said air feed channel to said air circulation strips in order to feed the strips with air while allowing the air that has been discharged against the stationary ring assembly to flow between said feed channel and said circulation strips in order to be exhausted therefrom.

12. A device according to claim 11 , wherein the stationary ring assembly comprises an inner casing which is surrounded by an outer casing of the gas turbine so as to define an annular chamber in which said control box is mounted.

13. A device according to claim 12 , wherein said control box bears in leaktight manner at an upstream axial end against the outer casing, and at a downstream axial end against the inner casing so as to define, inside said angular chamber, an air discharge upstream enclosure and an air exhaust downstream enclosure that is air-tight relative to said upstream enclosure.

14. A device according to claim 13 , wherein said inner casing presents an air opening at a downstream axial end, opening out into the air exhaust downstream enclosure in order to exhaust the air that has been discharged against the stationary ring assembly.

15. A device according to claim 12 , wherein the inner casing includes annular fins, and wherein the air circulation strips match substantially the shape of said fins.

16. A device according to claim 11 , wherein said control box is made up of at least two distinct angular box sectors.

17. A device according to claim 11 , wherein the spacing means connecting the feed channel to one of the air circulation strips are angularly offset relative to the spacing means connecting said feed channel to at least one of the other air circulation strips.

18. A device according to claim 11 , wherein the spacing means connecting the feed channel to one of the air circulation strips are angularly aligned relative to the spacing means connecting said feed channel with the other air circulation strips.

19. A device according to claim 11 , wherein the angular spacing between two successive spacing means does not exceed about 45°.

20. A turbomachine including a device according to claim 11 .