Turbine blade, turbocharger, and method of producing turbine blade

1. A turbine blade configured to be coupled to a rotational shaft and rotated around an axis, the turbine blade comprising:

a hub having a hub surface which is inclined with respect to the axis in a cross section along the axis

a rotor blade disposed on the hub surface;

at least one rib formed on a blade surface of the rotor blade, the at least one rib extending in a direction which intersects with a span direction of the rotor blade in a meridional plane of the rotor blade,

wherein, in the meridional plane of the rotor blade, the at least one rib is formed on a position which

satisfies a relationship Hl>0.5×Hb, where Hb is an entire height of the rotor blade in the span direction and Hl is

a height from the hub surface to the at least one rib in the span direction,

wherein the at least one rib includes:

a suction-surface side rib formed on a suction-surface side blade surface of the rotor blade and

farthest from the hub surface; and

a pressure-surface side rib formed on a pressure-surface side blade surface of the rotor blade

and farthest from the hub surface, and

wherein, in the meridional plane of the rotor blade, a relationship Hln<Hlp is satisfied, where Hln is a

height from the hub surface to the suction-surface side rib in the span direction and Hlp is a height from the hub

surface to the pressure-surface side rib in the span direction.

2. The turbine blade according to claim 1 ,

wherein, in the meridional plane of the rotor blade,

the at least one rib has an upstream end formed so as to be oriented in a first direction which is a direction away from the axis and a downstream end formed so as to be oriented in a second direction, and

a relationship θ 1 >θ 2 is satisfied, where θ 1 is an angular degree of an acute angle formed by the first direction and a direction parallel to the axis, and θ 2 is an angular degree of an acute angle formed by the second direction and the direction parallel to the axis.

3. The turbine blade according to claim 1 ,

wherein the at least one rib has an arc shape protruding toward the axis in the meridional plane of the rotor blade.

4. The turbine blade according to claim 1 ,

wherein at least a part of the at least one rib extends along a meridional line of the rotor blade in the meridional plane of the rotor blade.

5. The turbine blade according to claim 1 ,

wherein the at least one rib is configured to satisfy a relationship L≥2t, where L is a length of the at least one rib in the meridional plane and ‘t’ is a thickness of the at least one rib.

6. The turbine blade according to claim 1 ,

wherein the at least one rib has an oblique portion whose height increases gradually from an upstream end of the at least one rib toward a downstream side.

7. The turbine blade according to claim 1 ,

wherein the at least one rib is formed on the pressure-surface side blade surface of the rotor blade and at a position which satisfies a relationship Hl>0.7×Hb.

8. The turbine blade according to claim 7 ,

wherein, in the meridional plane of the rotor blade, when a reference meridional line is a meridional line which passes a region of the blade surface where the at least one rib is formed,

the region includes a section where a curve degree of the blade surface on the reference meridional line is maximum.

9. The turbine blade according to claim 1 ,

wherein the rotor blade and the at least one rib comprise the same metal material, and

wherein the at least one rib has a smaller density than the rotor blade.

10. A turbocharger, comprising:

a rotational shaft;

a compressor wheel coupled to a first end side of the rotational shaft; and

a turbine blade according to claim 1 , coupled to a second end side of the rotational shaft.

11. A method of producing a turbine blade according to claim 1 , comprising:

forming the hub, the rotor blade, and the at least one rib integrally by additive manufacturing of metal powder.