Cooling arrangement

1. A cooling arrangement for the admission of a cooling gas to a first cavity, comprising:

a first cavity, a second cavity spaced from the first cavity, and a third cavity spaced from the first cavity;

a first component having a wall separating the first cavity from the second cavity, the wall having a bearing side;

at least one cooling-gas passage arranged in said wall and communicatingly connecting the first cavity to the second cavity;

a second component bearing against the wall on the bearing side remote from the second cavity and separating the first cavity from the third cavity;

the second component being displaceable along the wall within a predetermined range of displacement;

the at least one cooling-gas passage including an orifice region facing the first cavity dimensioned, positioned, or both, so that an orifice cross section projects from the range of displacement at least to such an extent that the orifice region is open at least with a predetermined minimum cross section in any position of the second component within the range of displacement;

wherein the first component comprises a heat shield of a gas turbine, said heat shield, with respect to a rotation axis of a rotor of the gas turbine, being exposed radially on the inside to the third cavity and radially on the outside to the first cavity and to the second cavity;

wherein the wall projects radially outward from the heat shield;

wherein the wall extends in the circumferential direction;

wherein the at least one cooling-gas passage comprises a plurality of circumferentially distributed cooling-gas passages arranged in the wall;

a gap connecting the first cavity to the third cavity; and

wherein the second component comprises a seal which bears against the wall of the heat shield and is configured and arranged to bear against a second heat shield or against a root of a guide blade of the gas turbine, and seals said gap.

2. The cooling arrangement as claimed in claim 1 , wherein the cooling-gas passage has a predetermined nominal cross section outside said orifice region, the nominal cross section being smaller than the cross sections of the cooling-gas passage in the orifice region.

3. The cooling arrangement as claimed in claim 2 , wherein outside the orifice region the cooling-gas passage cross-section is constant and is the nominal cross section.

4. The cooling arrangement as claimed in claim 2 , wherein the minimum cross section is the same as or larger than the nominal cross section.

5. A cooling arrangement as claimed in claim 1 ,

wherein the plurality of cooling-gas passages, in said orifice region, widen towards the first cavity up to the orifice cross section.

6. The cooling arrangement as claimed in claim 5 , wherein the orifice region comprises a bevel.

7. The cooling arrangement as claimed in claim 1 , wherein:

the cooling-gas passage further comprises an abrupt cross-sectional widening, and the cooling passage merges into said orifice region by the abrupt cross-sectional widening; and

the cross section in the orifice region is constant from the cross-sectional widening up to the orifice cross section.

8. The cooling arrangement as claimed in claim 1 , wherein said at least one cooling-gas passage comprises at least two cooling-gas passages; and further comprising

a groove formed in the wall on the bearing side, the groove connecting the at least two cooling-gas passages to one another so that the orifice regions of said cooling-gas passages are formed by the groove or merge into the groove.

9. The cooling arrangement as claimed in claim 1 , further comprising:

a third component comprising said second heat shield or said root of a guide blade of the gas turbine; and

wherein said gap is formed between the first component and the third component.

10. The cooling arrangement as claimed in claim 1 , wherein the positioning, dimensioning, or both, of the orifice region is selected so that the orifice cross section is not open toward the third cavity in any position of the second component within the range of displacement.

11. The cooling arrangement as claimed in claim 1 , wherein the first component, the second component, and the wall extend annularly relative to a common longitudinal center axis;

wherein the wall separates the first cavity axially from the second cavity;

wherein the second cavity separates the first cavity radially from the third cavity;

wherein the second component is radially displaceable relative to the first component; and

wherein the cooling-gas passage opens into the first cavity in the region of an outer side, lying radially on the outside, of the second component.

12. The cooling arrangement as claimed in claim 1 , wherein the first cavity comprises a cavity in a gas turbine of a power plant.

13. A cooling arrangement for the admission of a cooling gas to a first cavity, comprising:

a first cavity, a second cavity spaced from the first cavity, and a third cavity spaced from the first cavity;

a first component having a wall separating the first cavity from the second cavity, the wall having a bearing side;

at least one cooling-gas passage arranged in said wall and communicatingly connecting the first cavity to the second cavity;

a second component bearing against the wall on the bearing side remote from the second cavity and separating the first cavity from the third cavity;

the second component being displaceable along the wall within a predetermined range of displacement;

the at least one cooling-gas passage including an orifice region facing the first cavity dimensioned, positioned, or both, so that an orifice cross section projects from the range of displacement at least to such an extent that the orifice region is open at least with a predetermined minimum cross section in any position of the second component within the range of displacement;

wherein the first component, the second component, and the wall extend annularly relative to a common longitudinal center axis;

wherein the wall separates the first cavity axially from the second cavity;

wherein the second cavity separates the first cavity radially from the third cavity;

wherein the second component is radially displaceable relative to the first component;

wherein the at least one cooling-gas passage opens into the first cavity in the region of an outer side, lying radially on the outside, of the second component;

wherein said at least one cooling-gas passage comprises at least two cooling-gas passages;

a circumferentially extending, axially open groove formed in the wall on the bearing side, the groove connecting the at least two cooling-gas passages to one another so that the orifice regions of said cooling-gas passages are formed by the groove or merge into the groove; and

wherein a plurality of circumferentially distributed cooling-gas passages are formed in the wall.