Annular or ring-segment-shaped cavities ( 2, 7 ) which are formed in particular in multi-shell ( 11; 12, 13 ) casings of turbomachines are preferably provided with suitable means for compensating for forming temperature stratifications. According to the invention, an overflow passage ( 14 ) connects two points of the cavity to one another which are situated in different circumferential positions. Arranged in the overflow passage ( 14 ) is an ejector ( 17 ) which can be operated with a motive fluid and which serves to drive a flow through the overflow passage from an upstream end ( 15 ) to a downstream end ( 16 ).
1. A turbomachine comprising at least one cavity having an annular or ring-segment-shaped cross section, an overflow passage connecting two points of the cavity to one another which are situated in different circumferential positions, an ejector arranged inside the overflow passage for driving a flow through the overflow passage from an upstream end to a downstream end of the overflow passage, and a discharge guide device arranged at the downstream end of the overflow passage through which the overflow passage opens out in the cavity to impart a single circumferential flow direction on the discharging flow in the cavity, wherein the outflow direction of the discharge guide device is inclined in the axial direction at an angle of less than 30° relative to the circumferential direction of the cavity.
2. The turbomachine as claimed in claim 1 , wherein the discharge guide device is a nozzle.
3. The turbomachine as claimed in claim 1 , wherein the ends of the overflow passage are arranged in different axial positions of the overflow passage.
4. The turbomachine as claimed in claim 1 , wherein openings for drawing off fluid from the cavity are arranged in the cavity.
5. A method of operating a turbomachine as claimed in claim 1 , wherein when the turbomachine is at rest, in particular during a cooling phase following a shutdown, a fluid flows into the overflow passage through the ejector and thus drives a flow in the overflow passage.
6. The method as claimed in claim 5 , wherein the mass flow through the overflow passage is proportioned in such a way that the volume of the cavity is circulated between 4 and 8 times per minute.
7. The method as claimed in claim 6 , wherein the mass flow through the ejector is between 8% and 15% of the mass flow through the overflow passage.
8. The method as claimed in claim 5 , wherein the mass flow through the ejector is between 8% and 15% of the mass flow through the overflow passage.
9. The method as claimed in claim 5 , wherein the fluid is heated before the inflow to the ejector.
10. The turbomachine as claimed in claim 1 , wherein the discharge guide device is arranged at a downstream orifice of the overflow passage.
11. The turbomachine as claimed in claim 1 , wherein the outflow direction of the discharge guide device is inclined in the axial direction at an angle of less than 10° relative to the circumferential direction of the cavity.
12. A turbomachine comprising at least one cavity having an annular or ring-segment-shaped cross section, an overflow passage connecting two points of the cavity to one another which are situated in different circumferential positions, an ejector arranged inside the overflow passage for driving a flow through the overflow passage from an upstream end to a downstream end of the overflow passage, and a discharge guide device arranged at the downstream end of the overflow passage through which the overflow passage opens out in the cavity to impart a single circumferential flow direction on the discharging flow in the cavity, wherein the outflow direction of the discharge guide device is oriented essentially in the circumferential direction of the cavity.
13. The turbomachine as claimed in claim 12 , wherein the discharge guide device is a nozzle.