Steam Turbine, and Steam Turbine Stationary Blade

1 . A steam turbine comprising a turbine stage having a stationary blade, with a slit to guide liquid droplets deposited on a blade wall surface to the inside of the stationary blade, in the blade wall surface, and a moving blade provided on the downstream side of the stationary blade in a working fluid flow direction,

wherein the stationary blade is a hollow-blade shaped stationary blade formed by deformation processing a metal plate, and

wherein a blade tail part of the stationary blade has the slit formed by overlaying an airfoil suction-side metal plate and an airfoil pressure-side metal plate with a gap therebetween.

2 . The steam turbine according to claim 1 , further comprising second slits provided in a plurality of positions in a blade height direction on the upstream side of the slit in a mainstream flow direction,

wherein the second slits are connected to a gap provided between the airfoil suction-side metal plate and the airfoil pressure-side metal plate.

3 . The steam turbine according to claim 2 ,

wherein the slit and the second slits are provided on the pressure side of airfoil, and

wherein the second slits are provided in a position in a range of 0.65 to 0.75 as l/L ratio between a distance l along a blade surface from the airfoil leading edge of the stationary blade to an arbitrary position of the blade surface and a distance L along the blade surface from the airfoil leading edge to the trailing edge of the stationary blade, and the slit is provided in a potion in a range of 0.75 to 0.9 as the l/L ratio.

4 . The steam turbine according to claim 1 , further comprising:

a pair of piece holes provided in the airfoil suction-side metal plate and the airfoil pressure-side metal plate;

a positioning piece having a spacer, held between the airfoil suction-side metal plate and the airfoil pressure-side metal plate, to form a gap, and a convex member, provided at both ends of the spacer and inserted in the piece holes, to fix mutual positions of the airfoil suction-side metal plate and the airfoil pressure-side metal plate, and

a step part, provided on the blade inner surface side of the airfoil suction-side metal plate, overlaid on the trailing edge side end of the airfoil pressure-side metal plate with a gap therebetween, to form the slit.

5 . The steam turbine according to claim 4 , wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are respectively formed with a separate metal plate of a metal plate forming the main body of the stationary blade.

6 . The steam turbine according to claim 5 , wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are respectively formed with the separate metal plate of the main body of the stationary blade at a part of a region on the outer peripheral side in the stationary blade height direction.

7 . The steam turbine according to claim 4 ,

wherein the airfoil suction-side metal plate is formed with the same member as the metal plate forming the main body of the stationary blade, and

wherein the airfoil pressure-side metal plate is formed with a separate metal plate of the metal plate forming the main body of the stationary blade.

8 . The steam turbine according to claim 7 ,

wherein the stationary blade has a reinforcing rib, to reinforce a welded part between the metal plate forming the main body of the stationary blade and the airfoil pressure-side metal plate, in the blade hollow part, and

wherein the reinforcing rib has a vent hole to communicate the blade hollow parts divided with the reinforcing rib into two sections.

9 . A steam turbine stationary blade having a slit, to guide liquid droplets deposited on a blade wall surface to the inside of the stationary blade, in the blade wall surface,

wherein the stationary blade is formed in a hollow blade shape by deformation processing a metal plate, and

wherein the slit is formed by overlaying an airfoil suction-side metal plate and an airfoil pressure-side metal plate with a gap therebetween in a blade tail part of the stationary blade.

10 . The steam turbine stationary blade according to claim 9 , further comprising second slits provided in a plurality of positions in a blade height direction on the upstream side of the slit in a mainstream flow direction,

wherein the second slits are connected to the gap provided between the airfoil suction-side metal plate and the airfoil pressure-side metal plate.

11 . The steam turbine stationary blade according to claim 10 ,

wherein the slit and the second slits are provided on the pressure side of airfoil, and

wherein the second slit is provided in a position in a range of 0.65 to 0.75 as l/L ratio between a distance l along a blade surface from the airfoil leading edge end of the stationary blade to an arbitrary position of the blade surface and a distance L along the blade surface from the airfoil leading edge end to the trailing edge of the stationary blade, and the slit is provided in a potion in a range of 0.75 to 0.9 as the l/L ratio.

12 . The steam turbine stationary blade according to of claim 9 , further comprising:

a pair of piece holes provided in the airfoil suction-side metal plate and the airfoil pressure-side metal plate;

a positioning piece having a spacer, held between the airfoil suction-side metal plate and the airfoil pressure-side metal plate, to form a gap, and a convex member, provided at both ends of the spacer and inserted in the piece holes, to fix mutual positions of the airfoil suction-side metal plate and the airfoil pressure-side metal plate; and

a step part, provided on the blade inner surface side of the airfoil suction-side metal plate, overlaid on the trailing edge side end of the airfoil pressure-side metal plate with a gap therebetween, to form the slit.

13 . The steam turbine stationary blade according to claim 12 , wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are respectively formed with a separate metal plate of a metal plate forming the main body of the stationary blade.

14 . The steam turbine stationary blade according to claim 13 , wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are respectively formed with the separate metal plate of the main body of the stationary blade at apart of a region on the outer peripheral side in the stationary blade height direction.

15 . The steam turbine stationary blade according to claim 12 ,

wherein the airfoil suction-side metal plate is formed with the same member as the metal plate forming the main body of the stationary blade, and

wherein the airfoil pressure-side metal plate is formed with a separate metal plate of the metal plate forming the main body of the stationary blade.

16 . The steam turbine stationary blade according to claim 15 , wherein the stationary blade has a reinforcing rib, to reinforce a welded part between the metal plate forming the main body of the stationary blade and the airfoil pressure-side metal plate, in the blade hollow part, and

wherein the reinforcing rib has a vent hole to communicate the blade hollow parts divided with the reinforcing rib into two sections.

17 . The steam turbine according to claim 2 , further comprising a rib formed on the blade inner-side surface of the airfoil suction-side metal plate or the airfoil pressure-side metal plate,

wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are joined via the rib.

18 . The steam turbine stationary blade according to claim 10 , further comprising a rib formed on the blade inner-side surface of the airfoil suction-side metal plate or the airfoil pressure-side metal plate,

wherein the airfoil suction-side metal plate and the airfoil pressure-side metal plate are joined via the rib.