Method and device for cooling steam turbine generating facility

A cooling method, for a steam turbine generating facility having an opposed-flow single casing steam turbine which is arranged at a higher pressure side of a low pressure turbine, the opposed-flow single casing steam turbine having a plurality of turbine parts installed with respect to a shaft of a turbine rotor and housed in a single casing and a dummy seal which isolates the plurality of turbine parts from one another, the method comprising:

• supplying cooling steam generated in the steam turbine generating facility to a cooling steam supply path formed in the dummy seal, the cooling steam having a temperature lower than a temperature of working steam which has been supplied to each of the plurality of turbine parts of the opposed-flow single casing steam turbine and which has passed through a first-stage stator blade, and the cooling steam having a pressure which is not less than a pressure of the working steam which has passed through the first-stage stator blade;
• cooling the dummy seal and the shaft of the turbine rotor arranged on an inner side of the dummy seal by introducing the cooling steam, which reaches an outer surface of the shaft of the turbine rotor and branches off toward both sides of the shaft of the turbine rotor, to a clearance formed between the dummy seal and the shaft of the turbine rotor and streaming the cooling steam in the clearance against steam from an exit of the first-stage stator blade, with the branched cooling steam streaming toward turbine blades respectively provided at both sides of the shaft of the turbine rotor;
• and
• after the cooling the dummy seal and the shaft of the turbine rotor, discharging the cooling steam through a cooling steam discharge path formed in the dummy seal to a discharge steam pipe to supply steam to a subsequent steam turbine,
• wherein:
• the opposed-flow single casing steam turbine includes a high pressure side turbine part and a low-pressure side turbine part, the working steam supplied to the high pressure side turbine part is different in pressure from the working steam supplied to the low-pressure side turbine part;
• the cooling steam supply path is configured to open to the clearance at a position between the low-pressure side turbine part and the cooling steam discharge path;
• the cooling steam reaching the clearance from the cooling steam supply path branches into a third cooling steam flow that streams toward the low-pressure side turbine part and a fourth cooling steam flow streaming toward the high-pressure side turbine part;
• the cooling steam of the third cooling steam flow is supplied to a turbine blade cascade part of the low-pressure side turbine part through the clearance against the steam from the exit of the first-stage stator blade of the low-pressure side turbine part streaming from the low-pressure side turbine part into the clearance;
• and
• the cooling steam of the fourth cooling steam flow is discharged through the cooling steam discharge path along with the steam which branches from the exit of the first-stage stator blade of the high-pressure side turbine part.

A cooling device for a steam turbine generating facility which has an opposed-flow single casing steam turbine, a low pressure turbine having a higher pressure side with the opposed-flow single casing steam turbine arranged on the higher pressure side, and a very high pressure turbine arranged on a higher pressure side of the opposed-flow single casing steam turbine, the opposed-flow single casing steam turbine comprising a plurality of turbine parts which are installed with respect to a shaft of a turbine rotor and housed in a single casing and a dummy seal which isolates the plurality of turbine parts from one another, and the very high pressure turbine being separate from the opposed-flow single casing steam turbine, the device comprising:

• a cooling steam supply path in the dummy seal configured to open to a clearance between the dummy seal and the shaft of the turbine rotor at an inner side of the dummy seal;
• a cooling steam pipe connected to the cooling steam supply path so as to supply cooling steam generated in the steam turbine generating facility to the cooling steam supply path at a temperature lower than that of working steam which has been supplied to each of the plurality of turbine parts of the opposed-flow single casing steam turbine and has passed through a first-stage stator blade and at a pressure not less than the pressure of the working steam at an exit of the first-stage stator blade;
• and
• a cooling steam discharge path formed in the dummy seal, configured to open to the clearance, and connected to an exhaust steam pipe which supplies steam to a subsequent steam turbine,
• wherein:
• the opposed-flow single casing steam turbine includes a high pressure side turbine part and a low-pressure side turbine part, and the working steam supplied to the high pressure side turbine part is different in pressure from the working steam supplied to the low-pressure side turbine part;
• the cooling steam discharge path is configured to open to the clearance on a side of the cooling steam supply path nearer to the low-pressure side turbine part than the cooling steam supply path;
• the cooling device is configured so that the cooling steam reaches an outer surface of the shaft of the turbine rotor and branches off toward both sides of the shaft of the turbine rotor so as to form a first cooling steam flow streaming toward the low-pressure side turbine part and a second cooling steam flow streaming toward the high-pressure side turbine part;
• the cooling device is configured so that the cooling steam streams into the clearance between the dummy seal and the shaft of the turbine rotor so as to cool the dummy seal and the shaft;
• the cooling device is configured so that a part of the cooling steam of the first cooling steam flow is be discharged through the cooling steam discharge path;
• the cooling device is configured so that the remnant of the cooling steam of the first cooling steam flow is supplied to a turbine blade cascade part of the low-pressure side turbine part;
• and
• the cooling device is configured so that the cooling steam of the second cooling steam flow reaches a turbine blade cascade part of the high-pressure side turbine part.