Turbine blade

1. A turbine blade which is arranged in plural in the circumferential direction of a turbine driven by a working fluid,

wherein said turbine blade is formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a constant value in a region from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a point most projecting on the blade suction surface side and is decreased monotonously from said point most projecting on the blade suction surface side toward a blade trailing edge defined as the downstream-most point of the blade in the axial direction.

2. A turbine blade according to claim 1 , wherein, assuming that a point at which a vertical line drawn from the blade trailing edge toward a tangential line with respect to the blade suction surface at the blade trailing edge crosses a blade pressure surface is defined as a trailing edge of the blade pressure surface, an angle at which the tangential line with respect to the blade suction surface at the blade trailing edge and a tangential line with respect to the blade pressure surface at the blade pressure-surface trailing edge cross each other is set to be not larger than 6 degrees.

3. A turbine blade according to claim 1 , wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of the blade suction surface at the trailing leading edge by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a certain value between 6 and 9.

4. A turbine blade according to claim 1 , wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of the blade suction surface at a throat position, defined as a position where an inter-blade flow passage is narrowest, by a pitch, is set to a value between 0.5 and 1.5.

5. A turbine blade which is arranged in plural in the circumferential direction of a turbine driven by a working fluid,

wherein said turbine blade is formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction is set to a constant value in a region from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a point most projecting on the blade suction surface side, is provided by a straight line or a curve expressed by a function of the second degree, which has no inflection point, in a region from said point most projecting on the blade suction surface side toward a point where the distance to a pressure surface of another adjacent blade is minimized, and is decreased continuously and monotonously in a region from said point where the distance to the pressure surface of another adjacent blade is minimized toward a blade trailing edge defined as the downstream-most point of the blade in the axial direction such that a reduction rate decreases toward the trailing edge.

6. A turbine blade which is arranged in plural in the circumferential direction of a turbine driven by a working fluid

wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of a blade suction surface defined by the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a certain value between 6 and 9 in a region from a blade leading edge defined as the upstream-most point of the blade in the axial direction to a point most projecting on-the blade suction surface side, and is set to a value between 0.5 and 1.5 at a throat position defined as a point where the distance to a pressure surface of another adjacent blade is minimized, and the dimensionless blade suction surface curvature is decreased linearly monotonously in a region from said point most projecting on the blade suction surface side to said throat point, and is decreased monotonously in a region from said throat point to the blade trailing edge such that a reduction rate of the dimensionless blade suction surface curvature decreases toward the trailing edge.

7. A turbine blade which is arranged in plural in the circumferential direction of a turbine driven by a working fluid,

wherein the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the curvature of a blade suction surface defined by the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction, is set to a certain value between 6 and 9 in a region from a blade leading edge defined as the upstream-most point of the blade in the axial direction to a point most projecting on-the blade suction surface side, and is set to a value between 0.5 and 1.5 at a throat position defined as a point where the distance to a pressure surface of another adjacent blade is minimized, and the dimensionless blade suction surface curvature in a region from said point most projecting to the blade suction surface side to said throat point is provided by a straight line or a curve expressed by a function of the second degree, which has no inflection point, or a curve expressed by a function of the third degree, which has only one inflection point, and is decreased monotonously in a region from said throat point to the blade trailing edge such that a reduction rate of the dimensionless blade suction surface curvature decreases toward the trailing edge.

8. A turbine comprising a plurality of stator blades and moving blades arranged in the circumferential direction of a rotor, a row of said stator blades and a row of said moving blades constituting a turbine stage,

wherein said stator blades are each formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction is set to a constant value from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a point most projecting on the blade suction surface side, and is decreased monotonously from said point most projecting on the blade suction surface side toward a blade trailing edge defined as the downstream-most point of the blade in the axial direction.

9. A turbine blade comprising a plurality of stator blades and moving blades arranged in the circumferential direction of a rotor, two rows of said stator blades and said moving blades constituting a turbine stage,

wherein said stator blades are each formed such that the dimensionless blade suction surface curvature, which is defined as a value resulting from multiplying the reciprocal of the radius of curvature of a blade surface on the blade suction surface side by a pitch defined by the distance between two adjacent blades in the circumferential direction is set to a constant value in a region from a blade leading edge defined as the upstream-most point of the blade in the axial direction toward a point most projecting on the blade suction surface side, is provided by a straight line or a curve expressed by a function of the second degree, which has no inflection point, in a region from said point most projecting on the blade suction surface side toward a point where the distance to a pressure surface of another adjacent blade is minimized, and is decreased monotonously in a region from said point where the distance to the pressure surface of another adjacent blade is minimized toward a blade trailing edge defined as the downstream-most point of the blade in the axial direction such that a reduction rate decreases toward the blade trailing edge.