A steam turbine is provided having a rotor which rotates around a machine axis, and a stator which concentrically encompasses the rotor with clearance, between which an annular passage is formed which is exposed to throughflow by steam in the axial direction and in which a multiplicity of rotor blades, which are fastened on the rotor, and fixed stator blades are arranged in a plurality of stages, wherein the stator blades of the last stage have a sweep with a sweep angle which changes in sign over the relative blade height.
1. A steam turbine ( 10 ) with a rotor ( 11 ) which rotates around a machine axis ( 17 ), and a stator ( 12 ) which concentrically encompasses the rotor ( 11 ) with clearance, between which an annular passage ( 13 ) is formed which is exposed to throughflow by steam ( 20 ) in the axial direction and in which a multiplicity of rotor blades ( 14 , 15 ), which are fastened on the rotor ( 11 ), and fixed stator blades ( 16 ) are arranged in a plurality of stages, wherein the stator blades ( 16 ) of the last stage have a sweep with a sweep angle (α, α 1 , α 2 , α 3 , β, ε) which changes over the relative blade height (h/h m ), the sweep is formed with an S-shape with a sweep angle (α, α 1 , α 2 , α 3 , β, ε) which both adjacent to the stator ( 12 ) and adjacent to the rotor ( 11 ) is positive, and at mid-height of the stator blade ( 16 ) is negative.
2. The steam turbine ( 10 ) as claimed in claim 1 , wherein the stator blades ( 16 ) of the last stage have a leading edge ( 16 b ), a trailing edge ( 16 a ) and a center of gravity line, and the S-shaped sweep extends along the leading edge ( 16 b ), the trailing edge ( 16 a ) and the center of gravity line.
3. The steam turbine ( 10 ) as claimed in claim 1 , wherein the stator blades ( 16 ) of the last stage have a leading edge ( 16 b ), a trailing edge ( 16 a ) and a center of gravity line, and the S-shaped sweep extends along two of the three lines which are trailing edge, leading edge and center of gravity line.
4. The steam turbine ( 10 ) as claimed in claim 1 , wherein the stator blades ( 16 ) of the last stage have a leading edge ( 16 b ), a trailing edge ( 16 a ) and a center of gravity line, and the S-shaped sweep extends along either the trailing edge, the leading edge or the center of gravity line.
5. The steam turbine ( 10 ) as claimed in claim 1 , wherein the stator blades ( 16 ) of the last stage have a trailing edge ( 16 a ) and the S-shaped sweep extends along the trailing edge ( 16 a ).
6. The steam turbine ( 10 ) as claimed in claim 3 , wherein the curve progression of the sweep angle (α, α 1 , α 2 , α 3 , β, ε) in dependence upon the relative blade height (h/h m ) is homogeneous for the leading edge ( 16 b ), for the trailing edge ( 16 a ) and for the center of gravity line.
7. The steam turbine ( 10 ) as claimed in claim 3 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 20°, and at mid-height lies in the range of between −6° and −10°.
8. The steam turbine ( 10 ) as claimed in claim 3 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 25°, and at mid-height lies in the range of between 0° and −15°.
9. The steam turbine ( 10 ) as claimed in claim 1 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) is negative in a range of the relative blade height (h/h m ) of 30% to 80%.
10. The steam turbine ( 10 ) as claimed in claim 1 , wherein the stator blades ( 16 ) of the last stage have an inclination (δ) in the circumferential direction, with regard to a radial to the turbine rotor axis ( 17 ).
11. The steam turbine ( 10 ) as claimed in claim 10 , wherein the inclination angles (δ) vary over the blade height (h).
12. The steam turbine ( 10 ) as claimed in claim 11 , wherein the inclination angles continuously decrease over the blade height (h) from the hub to the casing of the steam turbine.
13. The steam turbine ( 10 ) as claimed in claim 11 , wherein the inclination angle (δ) of the trailing edge ( 16 a ) with regard to a radial to the rotor axis ( 17 ) of the steam turbine lies in a range of between −5° and +5° with minimum blade height (h), and lies in a range of between −10° and +5° with maximum blade height (h).
14. The steam turbine ( 10 ) as claimed in claim 1 , wherein the pitch ratio (T/S) of the stator blades ( 16 ) of the last stage of the steam turbine ( 10 ) lies in a range of between 0.4 and 0.5 with minimum blade height (h), and lies in a range of between 0.45 and 0.65 with maximum blade height (h).
15. The steam turbine ( 10 ) as claimed in claim 4 , wherein the curve progression of the sweep angle (α, α 1 , α 2 , α 3 , β, ε) in dependence upon the relative blade height (h/h m ) is homogeneous for the leading edge ( 16 b ), for the trailing edge ( 16 a ) and for the center of gravity line.
16. The steam turbine ( 10 ) as claimed in claim 4 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 20°, and at mid-height lies in the range of between −6° and −10°.
17. The steam turbine ( 10 ) as claimed in claim 5 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 20°, and at mid-height lies in the range of between −6° and −10°.
18. The steam turbine ( 10 ) as claimed in claim 4 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 25°, and at mid-height lies in the range of between 0° and −15°.
19. The steam turbine ( 10 ) as claimed in claim 5 , wherein the sweep angle (α, α 1 , α 2 , α 3 , β, ε) adjacent to the rotor ( 11 ) and adjacent to the stator ( 12 ) lies in the range of between 10° and 25°, and at mid-height lies in the range of between 0° and −15°.