Gas turbine stationary blade and gas turbine

A turbine stationary blade, comprising:

• a blade body;
• and
• a shroud formed in an end portion of the blade body in a blade height direction,
• wherein the shroud includes:
• a bottom plate in contact with a combustion gas flow passage;
• a peripheral wall formed in the blade height direction and along a peripheral edge of the bottom plate;
• a recess forming a space surrounded by the peripheral wall and the bottom plate;
• a plurality of partition ribs connecting the blade body and the peripheral wall, dividing the recess into a plurality of cavities;
• and
• an impingement plate dividing each cavity into an outer cavity formed on an outer side in the blade height direction and an inner cavity formed on an inner side of the outer cavity, and having a plurality of through holes via which the outer cavity and the inner cavity communicate with each other,
• wherein the peripheral wall includes:
• a leading edge end portion extending to a leading edge side of the blade body;
• a suction side end portion extending from a leading edge to a trailing edge on a suction side of the blade body, and internally including a suction side passage;
• a pressure side end portion extending from a leading edge to a trailing edge on a pressure side of the blade body, and internally including a pressure side passage;
• and
• a trailing edge end portion extending to a trailing edge side of the blade body,
• wherein the plurality of cavities are formed from the inner cavity, and include:
• a first cavity disposed on a leading edge pressure side of the blade body so as to surround a circumference of the blade body between the blade body and the peripheral wall, connected to a cooling hole formed in the bottom plate, and connected to the pressure side passage;
• and
• a second cavity disposed adjacent to an axially downstream side of the first cavity, the second cavity being disposed on an axially downstream side of a plurality of sides of the pressure side of the blade body among the partition ribs, disposed via a first partition rib connecting the pressure side end portion of the peripheral wall and a pressure surface of the blade body, and having a plurality of cooling holes in the bottom plate,
• wherein an opening density of the through holes of the impingement plate in the second cavity is lower than the opening density of the through holes of the impingement plate in the first cavity,
• wherein the second cavity includes a plurality of intermediate cavities which are divided by a second partition rib constituted by a plurality of intermediate partition ribs connecting the pressure side end portion of the peripheral wall and the pressure surface of the blade body, the plurality of intermediate partition ribs being disposed along the pressure surface of the blade body from an axially upstream side of the plurality of sides of the pressure side toward the axially downstream side of the plurality of sides, and
• wherein the opening density of the through holes of the impingement plate in the intermediate cavities decreases toward the axially downstream side, and is lower in the intermediate cavities disposed axially downstream via the intermediate partition ribs than in the intermediate cavities on the axially upstream side of the pressure side of the blade body.

A cooling method for a turbine stationary blade including:

• a blade body;
• and
• a shroud formed in an end portion of the blade body in a blade height direction,
• the shroud including:
• a bottom plate in contact with a combustion gas flow passage;
• a peripheral wall formed in the blade height direction and along a peripheral edge of the bottom plate;
• a recess forming a space surrounded by the peripheral wall and the bottom plate;
• a plurality of partition ribs connecting the blade body and the peripheral wall, dividing the recess into a plurality of cavities;
• and
• an impingement plate dividing each cavity into an outer cavity formed on an outer side in the blade height direction and an inner cavity formed on an inner side of the outer cavity, and having a plurality of through holes via which the outer cavity and the inner cavity communicate with each other,
• wherein the peripheral wall includes:
• a leading edge end portion extending to a leading edge side of the blade body;
• a suction side end portion extending from a leading edge to a trailing edge on a suction side of the blade body, and internally including a suction side passage;
• a pressure side end portion extending from a leading edge to a trailing edge on a pressure side of the blade body, and internally including a pressure side passage;
• and
• a trailing edge end portion extending to a trailing edge side of the blade body,
• wherein the plurality of cavities are formed from the inner cavity, and include:
• a first cavity disposed on a leading edge pressure side of the blade body so as to surround a circumference of the blade body between the blade body and the peripheral wall, connected to a cooling hole formed in the bottom plate, and connected to the pressure side passage;
• and
• a second cavity disposed adjacent to an axially downstream side of the first cavity, the second cavity being disposed on an axially downstream side of a plurality of sides of the pressure side of the blade body among the partition ribs, disposed via a first partition rib connecting the pressure side end portion of the peripheral wall and a pressure surface of the blade body, and having a plurality of cooling holes in the bottom plate,
• wherein the cooling holes of the first cavity and the second cavity form a plurality of cooling hole rows consisting of a plurality of the cooling holes, each cooling hole having a first end and a second end, whose first ends are connected to respective inlet openings formed in the bottom plate and second ends are connected to respective outlet openings formed in a gas path surface of the bottom plate,
• wherein the cooling hole rows include an opening center line which consists of a linear first opening center line connecting the outlet openings of the cooling holes, and a linear second opening center line disposed in parallel to the first opening center line and connecting the inlet openings of the cooling holes,
• wherein the first opening center line is disposed in parallel to the first partition rib,
• wherein an opening density of the through holes of the impingement plate in the second cavity is lower than the opening density of the through holes of the impingement plate in the first cavity, and
• wherein the first partition rib includes a cooling hole row consisting of the plurality of cooling holes which join the inlet openings formed on an inner surface side of the bottom plate on a leading edge side of the first partition rib and the outlet openings formed on a gas path surface side of the bottom plate on a trailing edge side of the first partition rib,
• the cooling method for the turbine stationary blade comprising:
• externally supplying cooling air to the outer cavity;
• reducing a pressure of the cooling air, where the cooling air is supplied from the outer cavity to the inner cavity via the through holes formed in the impingement plate, an internal pressure of the cavities decreases toward the axially downstream side, and a differential pressure between the inner cavity and the combustion gas flow passage is maintained constant;
• impingement-cooling an inner surface of the bottom plate with the cooling air;
• and
• film-cooling the gas path surface when the cooling air after the impingement cooling is discharged from the cooling holes formed in the bottom plate to the combustion gas flow passage.