Steam turbine stationary blade

1. A steam turbine stationary blade with a hollow region therein, the steam turbine stationary blade comprising:

a plurality of slots arranged in lines in a direction of a chord length, the plurality of slots each communicates with a working fluid flow passageway and with the hollow region, and extends in a direction of a blade length; and

at least one connecting portion disposed so that for each of the most downstream slot of the plurality of slots, a surface directed toward the working fluid flow passageway is positioned closer to the hollow region than to a surface of the steam turbine stationary blade, and so that the connecting portion connects both sidewall surfaces of each of the most downstream slot, in the direction of the chord length, wherein

the plurality of slots communicate the working fluid flow passageway and the hollow region over an entire length thereof in the blade length direction,

the connecting portion connects both sidewall surfaces of the most downstream slot, with only a part of the most downstream slot in the blade length direction.

2. The steam turbine stationary blade according to claim 1 , wherein:

the connecting portion is disposed inside each of the most downstream slots and connects inner surfaces of the most downstream slot that face each other, in the direction of the chord length.

3. The steam turbine stationary blade according to claim 1 , comprising:

at least one connecting portion positioned so that a surface directed toward the working fluid flow passageway is positioned closer to the hollow region than to the surface of the steam turbine stationary blade, for at least one upstream slot disposed upstream in the direction of the chord length with respect to the most downstream slots, the connecting portion connecting both sidewall surfaces of the upstream slot, in the direction of the chord length.

4. The steam turbine stationary blade according to claim 3 , wherein:

the plurality of slots are provided on a pressure side of the airfoil.

5. The steam turbine stationary blade according to claim 4 , wherein:

the upstream slot is provided at a position falling within a 0.6 to 0.8 range of a dimensionless value l/L obtained by dividing a distance l as measured from a leading edge portion to a given position on the pressure side of the airfoil, by a distance L as measured from the leading edge portion to a trailing edge portion, along the pressure side of the airfoil; and

the most downstream slots are positioned so that they fall within a range exceeding the dimensionless value l/L of the upstream slot.

6. The steam turbine stationary blade according to claim 1 , wherein:

the plurality of slots are provided on a suction side of the airfoil.

7. The steam turbine stationary blade according to claim 1 , wherein:

the connecting portion is disposed inside the hollow region and connects both sidewall surfaces of the most downstream slot in the direction of the chord length, across the most downstream slot.

8. A steam turbine with a turbine stage, the steam turbine including:

the steam turbine stationary blade of claim 1 ; and

a steam turbine moving blade provided downstream of a direction in which a working fluid flows, relative to the steam turbine stationary blade.

9. A steam turbine stationary blade with a hollow region therein, the steam turbine stationary blade comprising:

a plurality of slots arranged in lines in a direction of a chord length, the plurality of slots each communicates with a working fluid flow passageway and with the hollow region, and extends in a direction of a blade length; and

at least one connecting portion disposed so that for each of the most downstream slots of the plurality of slots, a surface directed toward the working fluid flow passageway is positioned closer to the hollow region than to a surface of the steam turbine stationary blade, and so that the connecting portion connects both sidewall surfaces of each of the most downstream slots, in the direction of the chord length, wherein:

the connecting portion is disposed inside the hollow region and connects both sidewall surfaces of each most downstream slot in the direction of the chord length, across the most downstream slot, and

the connecting portion is in contact with a surface opposed to each of the most downstream slots, across the hollow region.

10. A method for modifying a steam turbine stationary blade including a hollow region inside the blade, the method comprising:

forming a plurality of slots arranged in lines in a direction of a chord length, each communicating with a working fluid flow passageway and the hollow region, the slots extending in a direction of a blade length; and

providing at least one connecting portion that connects both sidewall surfaces of each of the most downstream slots, in the direction of the chord length, in such a form that for each of the most downstream slots of the plurality of slots, a surface directed toward the working fluid flow passageway is positioned closer to the hollow region than to a surface of the steam turbine stationary blade, wherein:

the connecting portion is disposed inside the hollow region and connects both sidewall surfaces of each of the most downstream slots in the direction of the chord length, across the most downstream slots, and

the connecting portion is in contact with a surface opposed to each of the most downstream slots, across the hollow region.