Steam turbine

1. A steam turbine, comprising:

a rotor configured to rotate about an axis;

a casing which houses the rotor; and

a first stage including a first-stage stationary vane fixed to an inner wall portion of the casing and a first-stage rotor blade fixed to the rotor at downstream of the first-stage stationary vane,

wherein the rotor includes a first cavity having a concave shape and being formed on a portion facing the first-stage stationary vane, the first cavity being in communication with an inner space defined between the inner wall portion and the rotor at upstream of the first-stage stationary vane,

wherein the first-stage stationary vane includes a first-stage through hole which is in communication with the first cavity and which is formed through the first-stage stationary vane in a radial direction, and

wherein the steam turbine is configured such that steam introduced from the first cavity via an inlet opening of the first-stage through hole flows through the first-stage through hole.

2. The steam turbine according to claim 1 , wherein the first stage is positioned upstream of a final stage of the steam turbine.

3. The steam turbine according to claim 1 , wherein the first stage is positioned in a wet region which is a region downstream of a change position where main steam flowing through the inner space changes from dry steam to wet steam, the first stage being a most upstream stage in the wet region in a case where a plurality of stages are disposed in the wet region.

4. The steam turbine according to claim 1 ,

wherein the first-stage stationary vane includes a stationary-vane body portion extending from the inner wall portion toward the rotor, and a partition plate having an annular shape and being disposed on a tip portion of the stationary-vane body portion, and

wherein the inlet opening is formed on the partition plate.

5. The steam turbine according to claim 4 ,

wherein the partition plate includes a first seal portion configured to seal a gap between the partition plate and the rotor, and

wherein the inlet opening is formed downstream of the first seal portion, or on a position overlapping with a region where the first seal portion is formed in an axial direction of the rotor.

6. The steam turbine according to claim 5 ,

wherein the partition plate further includes a second seal portion configured to seal a gap between the partition plate and the rotor, at downstream of the first seal portion, and

wherein the inlet opening is formed upstream of the second seal portion, or on a position overlapping with a region where the second seal portion is formed in an axial direction of the rotor.

7. The steam turbine according to claim 1 ,

wherein the casing further includes an outer wall portion defining an outer space formed on a radially outer side of the inner space, between the outer wall portion and the inner wall portion,

wherein the outer space is formed on a position overlapping with a region where the first-stage stationary vane is formed in an axial direction of the rotor, the outer space being in communication with the inner space at downstream of the first-stage stationary vane, and

wherein the steam turbine is configured such that steam after flowing through the first-stage through hole is discharged to the outer space from an outlet opening of the first-stage through hole.

8. The steam turbine according to claim 1 ,

wherein the steam turbine further includes a second stage including a second-stage stationary vane fixed to the inner wall portion and a second-stage rotor blade fixed to the rotor at downstream of the second-stage stationary vane, the second stage being positioned downstream of the first stage,

wherein the rotor includes a second cavity having a concave shape and being formed on a portion facing the second-stage stationary vane, the second cavity being in communication with the inner space at upstream of the second-stage stationary vane,

wherein the second-stage stationary vane has a second-stage through hole being in communication with the second cavity and being formed through the second-stage stationary vane in the radial direction,

wherein the steam turbine further includes a connection passage connecting the first-stage through hole and the second-stage through hole, and

wherein the steam turbine is configured such that the steam after flowing through the first-stage through hole is discharged to the second cavity from an outlet opening of the second-stage through hole via the connection passage and the second-stage through hole.

9. The steam turbine according to claim 8 ,

wherein the first stage and the second stage are continuous stages.

10. The steam turbine according to claim 8 ,

wherein, when A 1 is an area of an inlet opening of the first-stage through hole, A 2 is a flow-passage area of the connection passage, and A 3 is an area of the outlet opening of the second-stage through hole, expressions A 3 >A 1 and A 3 >A 2 are satisfied.

11. The steam turbine according to claim 8 ,

wherein the outlet opening of the second-stage through hole has an opening toward a farthest back portion of a bottom portion of the second cavity, in a cross-sectional view taken along an axial direction of the rotor.

12. The steam turbine according to claim 8 ,

wherein the outlet opening of the second-stage through hole has an opening toward a downstream side in a rotational direction of the rotor.

13. The steam turbine according to claim 1 ,

wherein the first stage is positioned upstream of a final stage of the steam turbine,

wherein the final stage includes a final-stage stationary vane fixed to the inner wall portion and a final-stage rotor blade fixed to the rotor at downstream of the final-stage stationary vane,

wherein the rotor includes a final-stage cavity having a concave shape and being formed on a portion facing the final-stage stationary vane, the final-stage cavity being in communication with the inner space at upstream of the final-stage stationary vane,

wherein the final-stage stationary vane includes a final-stage through hole which is in communication with the final-stage cavity and which is formed through the final-stage stationary vane in the radial direction, and

wherein the steam turbine is configured such that steam introduced from an inlet opening of the final-stage cavity flows through the final-stage through hole.

14. The steam turbine according to claim 13 ,

wherein the final-stage stationary vane is formed to have a hollow shape in cross section, including a pressure side portion having a plate shape and a suction side portion having a plate shape and defining a cavity portion between the pressure side portion and the suction side portion,

wherein the pressure side portion of the final-stage stationary vane has a slit being in communication with the cavity portion, and

wherein the final-stage stationary vane includes a division plate dividing the cavity portion into a droplet-removing flow passage being in communication with the slit and the final-stage through hole.

15. The steam turbine according to claim 14 ,

wherein, when defining a super-cooled suction side portion as a downstream side of a throat position, of the suction side portion of the final-stage stationary vane, the final-stage through hole is formed so as to face the super-cooled suction side portion inside the final-stage stationary vane.

16. The steam turbine according to claim 1 ,

wherein a first-stage annular space having an annular shape and being in communication with the first-stage through hole is formed inside the inner wall portion supporting the first-stage stationary vane.

17. The steam turbine according to claim 1 ,

wherein the first-stage stationary vane is formed to have a hollow shape in cross section, including a pressure side portion having a plate shape and a suction side portion having a plate shape and defining a cavity portion between the pressure side portion and the suction side portion.

18. The steam turbine according to claim 17 ,

wherein the first-stage stationary vane includes a division plate dividing the cavity portion into the first-stage through hole and a space other than the first-stage through hole, and

wherein, when defining a super-cooled suction side portion as a downstream side of a throat position, of the suction side portion of the first-stage stationary vane, the first-stage through hole is formed so as to face the super-cooled suction side portion inside the first-stage stationary vane.