Cooling structure for turbine, and gas turbine

A cooling structure for a turbine, the cooling structure comprising:

• disks configured to rotate integrally with blades about a rotational axis in a rotational direction, the disks being disposed in a plurality of stages along the rotational axis;
• and
• disk holes defined in the disks along a circumferential direction, the disk holes being configured to supply cooling air to the disks on a downstream side so as to cool the blades,
• wherein:
• at least one of the disks, from among the disks from a second of the disks onward from an upstream side in a flow direction of the cooling air, is configured as a motive power recovery disk in which at least one of the disk holes is set such that an outlet absolute circumferential velocity vector, which is a component in the rotational direction of a velocity vector of the cooling air at an outlet of the at least one of the disk holes, is smaller than an inlet absolute circumferential velocity vector, which is a component in the rotational direction of a velocity vector of the cooling air at an inlet of the at least one of the disk holes;
• the rotational direction of the motive power recovery disk is defined as a positive direction and a direction opposite the rotational direction of the motive power recovery disk is defined as a negative direction;
• and
• the cooling air is configured to be supplied to the motive power recovery disk from one of the disks disposed further to the upstream side in the flow direction of the cooling air than the motive power recovery disk.