Turbine rotor assembly, turbine, and rotor blade

1. A turbine rotor assembly comprising:

a rotor shaft on which a blade groove extending along a circumferential direction is defined; and

a rotor blade, the rotor blade including:

a blade section on an outer side of the rotor shaft in a radial direction of the rotor shaft; and

a blade root section integrally formed with the blade section and configured to be fitted in the blade groove,

wherein the rotor shaft includes:

two protrusions which are separated from each other in an axial direction of the rotor shaft and define a first part of a wall surface of the blade groove and an opening of the blade groove, the two protrusions each protruding outward from an outer circumferential surface of the rotor shaft in the radial direction of the rotor shaft;

two bearing surfaces on an inner side of the outer circumferential surface of the rotor shaft in the radial direction of the rotor shaft, the two bearing surfaces facing inward in the radial direction of the rotor shaft, the two bearing surfaces being separated from each other in the axial direction of the rotor shaft and the two bearing surfaces defining a second part of the wall surface of the blade groove;

two first facing surfaces which face each other in the axial direction of the rotor shaft and define a third part of the wall surface of the blade groove, the two first facing surfaces being between the two bearing surfaces and outer circumferential surfaces of the two protrusions in the radial direction of the rotor shaft; and

two second facing surfaces between the two bearing surfaces and the outer circumferential surfaces of the two protrusions in the radial direction of the rotor shaft, on an outer side of the two first facing surfaces, the two second facing surfaces facing each other in the axial direction of the rotor shaft with a gap therebetween which is larger than a gap between the first facing surfaces, the two second facing surfaces defining a fourth part of the wall surface of the blade groove, and

wherein the blade root section includes:

two contact surfaces which are separated from each other in the axial direction of the rotor shaft, and are contactable with the two bearing surfaces in the radial direction of the rotor shaft, respectively;

two first side surfaces each facing a corresponding one of the two first facing surfaces;

two second side surfaces each facing a corresponding one of the two second facing surfaces with a gap therebetween that is smaller than a distance between a corresponding one of the two first facing surfaces and a corresponding one of the two first side surfaces facing the corresponding one of the two first facing surfaces; and

two flange sections which are each positioned, when the blade root section is fitted in the blade groove, adjacent to the outer circumferential surface of a corresponding one of the two protrusions in the radial direction of the rotor shaft, the two flange sections defining a part of a platform section continuing to a blade profile section of the rotor blade.

2. The turbine rotor assembly according to claim 1 , wherein a length, in the axial direction of the rotor shaft, of the blade root section including the two contact surfaces, at a position where the two contact surfaces are defined, is 1.2 times a length of the platform section or less.

3. The turbine rotor assembly according to claim 2 , wherein the length, in the axial direction of the rotor shaft, of the blade root section including the two contact surfaces, at the position where the two contact surfaces are defined, is not longer than the length of the platform section.

4. The turbine rotor assembly according to claim 1 , wherein:

the two protrusions include:

a first protrusion on an upstream side in a flow direction of a working fluid; and

a second protrusion on a downstream side in the flow direction of the working fluid,

a first of the two flange sections is adjacent to the outer circumferential surface of the first protrusion in the radial direction of the rotor shaft; and

a second of the two flange sections is adjacent to the outer circumferential surface of the second protrusion in the radial direction of the rotor shaft, and

a length of at least the first of the two flange sections is shorter than a length between the outer circumferential surface of the rotor shaft and the outer circumferential surface of the first protrusion, in the radial direction of the rotor shaft.

5. The turbine rotor assembly according to claim 1 , wherein the rotor shaft has a drum shape.

6. A turbine comprising:

the turbine rotor assembly according to claim 1 ;

a housing enclosing the turbine rotor assembly; and

a stator blade attached to the housing.

7. The turbine rotor assembly according to claim 1 , wherein a length, in the axial direction of the rotor shaft, of the blade root section including the two contact surfaces, at a position where the two contact surfaces are defined, is 0.7 times a length of the platform section or more.

8. The turbine rotor assembly according to claim 1 , wherein each of the two bearing surfaces is planar.

9. The turbine rotor assembly according to claim 1 , wherein each of the two contact surfaces is planar.

10. The turbine rotor assembly according to claim 1 , wherein:

each of the two bearing surfaces is planar; and

each of the two contact surfaces is planar.

11. The turbine rotor assembly according to claim 1 , wherein:

each of the two bearing surfaces is planar;

each of the two first facing surfaces is planar;

each of the two second surfaces is planar;

each of the two contact surfaces is planar;

each of the two first side surfaces is planar; and

each of the two second side surfaces is planar.

12. The turbine rotor assembly according to claim 1 , wherein the rotor blade is one of a plurality of rotor blades.

13. The turbine according to claim 6 , wherein the stator blade is one of a plurality of stator blades.

14. The turbine according to claim 6 , wherein:

the rotor blade is one of a plurality of rotor blades; and

the stator blade is one of a plurality of stator blades.