DEVICE FOR COOLING A TURBOMACHINE TURBINE CASING

Abstract

Device for cooling a turbine casing in a turbomachine, this turbine comprising several stages each including a nozzle assembly (18) formed of an annular row of fixed vanes (20) and an impeller mounted to rotate in a cylindrical shroud formed of ring sectors (34) fixed to the casing, and a cooling circuit comprising ducts carrying cooling air into cavities (46) formed in the vanes (20) of the nozzle assembly, and means for carrying air to casing upstream hooks (72) for suspending the ring sectors (34).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other characteristics, details and advantages thereof will become more clearly apparent from reading the description which follows, given by way of nonlimiting example with reference to the attached drawings in which:

FIG. 1 is a schematic part-view in axial section of a turbomachine equipped with the device according to the invention;

FIG. 2 is a view on a larger scale of part of FIG. 1 and depicts the nozzle assembly of the upstream stage of the turbine;

FIG. 2 a is an enlarged view of detail I₂ of FIG. 2;

FIG. 3 is a schematic part-view in perspective of the nozzle assembly of the upstream stage of the turbine, viewed in side view and from the upstream end;

FIG. 4 is a view corresponding to FIG. 2 and depicts an alternative form of embodiment of the device according to the invention;

FIG. 4 a is an enlarged view of detail I₄ of FIG. 4;

FIG. 5 is a schematic part-view in axial section of another alternative form of embodiment of the device according to the invention;

FIGS. 6 and 7 are schematic part-views in perspective of the external annular rim of the nozzle assembly of FIG. 5.

Claims

1. A device for cooling a turbine casing in a turbomachine particularly in an aviation turbojet engine or turboprop, this turbine comprising several stages each including a nozzle assembly formed of an annular row of fixed vanes borne by the casing of the turbine and an impeller mounted to rotate inside the casing in a cylindrical shroud formed of ring sectors fixed circumferentially to the casing, and a cooling circuit for cooling the vanes of the nozzle assembly of the upstream stage, comprising ducts for carrying cooling air into cavities formed in the vanes of the nozzle assembly, and means of carrying air to casing upstream hooks for suspending the ring sectors surrounding the impeller of the upstream stage, these air-carrying means connecting the internal cavities of the vanes of the nozzle assembly of the upstream stage to the annular space in which the upstream hooks lie, wherein: the internal cavities of the vanes are closed, at their radially external ends, by plates attached to the nozzle assembly; and the air-carrying means comprise drillings formed in these plates and drillings formed in an external annular rim of the nozzle assembly which extends radially between the radially external walls of the vane cooling cavities and the upstream hooks for suspending the ring sectors.

2. The device as claimed in claim 1, wherein the means for carrying air to the upstream casing hooks are distributed over the periphery of the nozzle assembly and are formed in each fixed vane.

3. The device as claimed in claim 1 or 2, wherein the drillings are formed by electro-discharge machining.

4. The device as claimed in one of claims 1 to 3, wherein the drillings formed in the external annular rim of the nozzle assembly extend obliquely with respect to this rim and with respect to the axis of rotation.

5. The device as claimed in claim 4, wherein the drillings at their downstream ends open directly into the annular space in which the upstream hooks lie.

6. The device as claimed in one of claims 1 to 4, wherein the drillings are formed at the internal periphery of the external annular rim and at their downstream ends open into an annular passage formed between the external annular rim of the nozzle assembly and an annular deflector attached and fixed to a downstream end part of the nozzle assembly.

7. The device as claimed in claim 6, wherein the annular deflector is engaged and fixed in an external annular groove of the nozzle assembly and bears axially on the upstream ends of the ring sectors.

8. The device as claimed in claim 6 or 7, wherein the annular deflector is split into sectors and made up of several parts assembled end to end via sealing strips.

9. The device as claimed in one of claims 1 to 3, wherein the drillings formed in the external annular rim of the nozzle assembly are more or less perpendicular to this rim and are supplied with cooling air via slots formed in regions where this rim catches on the casing of the turbine.

10. A turbine for a turbomachine such as an aviation turbojet engine or turboprop and which comprises a cooling device as claimed in one of the preceding claims.

11. A turbomachine turbine upstream nozzle assembly comprising an annular row of vanes which are connected at their radially internal ends to an internal wall of revolution and at their radially external ends to an external wall of revolution, the vanes comprising internal cavities for the flow of cooling air and the external wall comprising an external annular rim at its downstream end which rim is formed with means for catching on a casing of the turbomachine, wherein: the internal cavities of the vanes are closed, at their radially external ends, by plates attached to the external wall of the nozzle assembly; and these plates and the annular rim of the nozzle assembly comprise drillings for the passage of cooling air.

12. The nozzle assembly as claimed in claim 11, wherein the drillings are formed at the internal periphery of the annular rim.

13. The nozzle assembly as claimed in claim 11 or 12, wherein the drillings are formed obliquely or perpendicularly with respect to the annular rim.

14. The nozzle assembly as claimed in claim 11 or 12, wherein an annular deflector is fixed to the external wall of revolution downstream of the annular rim.

15. A turbomachine which comprises a cooling device as claimed in one of the claims 1 to 9.