Turbine blade and gas turbine

1. A turbine blade comprising:

an airfoil portion;

a cooling passage extending in a blade height direction inside the airfoil portion; and

a plurality of cooling holes formed in a trailing edge part of the airfoil portion to be arranged in the blade height direction, the plurality of cooling holes communicating with the cooling passage and opening to a trailing-edge end surface of the airfoil portion in the trailing edge part, the trailing-edge end surface being an end surface facing downstream in an axial direction,

wherein a formation region of the plurality of cooling holes in the trailing edge part includes:

a center region including an intermediate position between a first end and a second end of the airfoil portion in the blade height direction, the center region having a constant index d_mid indicating opening densities of the plurality of cooling holes; and

an upstream region positioned upstream of a flow of a cooling medium in the cooling passage from the center region in the blade height direction, the upstream region having a constant index d_up indicating the opening densities of the plurality of cooling holes, and

wherein a relation of d_up<d_mid is satisfied.

2. A turbine blade comprising:

an airfoil portion;

a cooling passage extending in a blade height direction inside the airfoil portion; and

a plurality of cooling holes formed in a trailing edge part of the airfoil portion to be arranged in the blade height direction, the plurality of cooling holes communicating with the cooling passage and opening to a trailing-edge end surface of the airfoil portion in the trailing edge part, the trailing-edge end surface being an end surface facing downstream in an axial direction,

wherein the turbine blade is a rotor blade,

wherein a formation region of the plurality of cooling holes in the trailing edge part includes:

a center region including an intermediate position between a tip and a root of the airfoil portion in the blade height direction, the center region having a constant index d_mid indicating opening densities of the plurality of cooling holes;

a tip region positioned closer to the tip than the center region in the blade height direction, the tip region having a constant index d_tip indicating the opening densities of the plurality of cooling holes; and

a root region positioned closer to the root than the center region in the blade height direction, the root region having a constant index d_root indicating the opening densities of the plurality of cooling holes,

wherein a relation of d_tip<d_mid is satisfied, and

wherein each of the indexes d_tip, d_root and d_mid indicating the opening densities is represented by a ratio D/P of a through-hole diameter D of each of the cooling holes disposed so as to penetrate the trailing edge part to a pitch P between the cooling holes adjacent to each other in the blade height direction.

3. The turbine blade according to claim 1 ,

wherein the plurality of cooling holes open to the trailing-edge end surface of the airfoil portion,

wherein the formation region of the plurality of cooling holes in the trailing edge part includes a downstream region positioned downstream of the flow of the cooling medium from the center region in the blade height direction, the downstream region having a constant index d_down indicating the opening densities of the plurality of cooling holes, and

wherein a relation of d_up<d_mid<d_down is satisfied.

4. The turbine blade according to claim 1 ,

wherein the formation region of the plurality of cooling holes in the trailing edge part includes a downstream region positioned downstream of the flow of the cooling medium in the cooling passage from the center region in the blade height direction, the downstream region having a constant index d_down indicating the opening densities of the plurality of cooling holes, and

wherein a relation of d_up<d_down<d_mid is satisfied.

5. The turbine blade according to claim 2 ,

wherein a relation of d_tip<d_mid<d_root is satisfied, where d_root is an index in a region positioned closer to the root than the center region in the blade height direction,

wherein the index d_root indicating the opening densities is a ratio D/P of a through-hole diameter D of each of the cooling holes disposed so as to penetrate the trailing edge part to a pitch P between the cooling holes adjacent to each other in the blade height direction, and

wherein the formation region of the plurality of cooling holes in the trailing edge part includes a root region positioned closer to the root than the center region in the blade height direction and closest to the root in the formation region, the root region having the constant index d_root indicating the opening densities of the plurality of cooling holes.

6. The turbine blade according to claim 2 ,

wherein the plurality of cooling holes are formed in the trailing edge part of the airfoil portion to perform convection-cooling of the trailing edge part, the plurality of cooling holes penetrating the trailing edge part to open to the trailing-edge end surface, and

wherein a relation of d_tip<d_root<d_mid is satisfied, where d_root is an index in a region positioned closer to the root than the center region in the blade height direction, and

wherein the formation region of the plurality of cooling holes in the trailing edge part includes a root region positioned closer to the root than the center region in the blade height direction and closest to the root in the formation region, the root region having the constant index d_root indicating the opening densities of the plurality of cooling holes.

7. The turbine blade according to claim 1 ,

wherein the center region includes a plurality of cooling holes having the same diameter, and

wherein a tip region and a root region each include a plurality of cooling holes having the same diameter as the cooling holes in the center region, the tip region being positioned closer to a tip of the airfoil portion than the center region, the root region being positioned closer to a root of the airfoil portion than the center region.

8. The turbine blade according to claim 2 ,

wherein the center region includes a plurality of cooling holes having the same diameter, and

wherein a tip region and a root region each include a plurality of cooling holes having the same diameter as the cooling holes in the center region, the tip region being positioned closer to a tip of the airfoil portion than the center region, the root region being positioned closer to a root of the airfoil portion than the center region.

9. The turbine blade according to claim 1 , wherein the plurality of cooling holes are obliquely formed with respect to a plane orthogonal to the blade height direction.

10. The turbine blade according to claim 2 , wherein the plurality of cooling holes are obliquely formed with respect to a plane orthogonal to the blade height direction.

11. The turbine blade according to claim 1 , wherein the plurality of cooling holes are formed in parallel to each other.

12. The turbine blade according to claim 2 , wherein the plurality of cooling holes are formed in parallel to each other.

13. The turbine blade according to claim 1 , wherein the cooling passage is a last path of a serpentine flow passage formed inside the airfoil portion.

14. The turbine blade according to claim 2 , wherein the cooling passage is a last path of a serpentine flow passage formed inside the airfoil portion.

15. The turbine blade according to claim 1 ,

wherein the turbine blade is a rotor blade, and

wherein the cooling passage has an outlet opening formed at a tip of the airfoil portion.

16. The turbine blade according to claim 2 ,

wherein the turbine blade is a rotor blade, and

wherein the cooling passage has an outlet opening formed at a tip of the airfoil portion.

17. The turbine blade according to claim 1 ,

wherein the turbine blade is a stator vane, and

wherein the cooling passage has an outlet opening formed on an inner shroud of the airfoil portion.

18. A gas turbine comprising:

the turbine blade according to claim 1 ; and

a combustor for producing a combustion gas flowing through a combustion gas flow passage where the turbine blade is disposed.

19. A gas turbine comprising:

the turbine blade according to claim 2 ; and

a combustor for producing a combustion gas flowing through a combustion gas flow passage where the turbine blade is disposed.