Steam turbine blade, and steam turbine and steam turbine power plant using the blade

Abstract

An object of the invention is to provide a steam turbine blade having a high degree of strength reliability that reduces the stress caused by a steam force acting on a steam turbine blade during the operation of a steam turbine and increases rigidity in the circumferential and axial directions of a turbine rotor to suppress vibration of the steam turbine blade resulting from the steam force, and a steam turbine and a steam turbine power plant using the same.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a steam turbine blade according to a first embodiment of the present invention as viewed from the turbine rotor axial direction and the steam inflow side.

FIG. 2 is a perspective view of the steam turbine blade of FIG. 1.

FIG. 3 is a cross-sectional view of the steam turbine blade taken along line A-A of FIG. 1.

FIG. 4 is a front view of a steam turbine blade according to a second embodiment of the present invention as viewed from the turbine rotor axial direction and the steam inflow side.

FIG. 5 is a front view of a steam turbine blade according to a third embodiment of the present invention as viewed from the turbine rotor axial direction and the steam inflow side.

FIG. 6 is a front view of an axial entry steam turbine blade having a single blade root with a T-head for a single blade, in which a throat on blade root hooks has the minimum width of hb as viewed from the turbine rotor axial direction.

FIG. 7 is a front view of an axial entry steam turbine blade having dual T-head blade roots with the same shape for a single blade, in which a throat on blade root hooks has the minimum width of (½)hb as viewed from the turbine rotor axial direction.

FIG. 8 is a diagram showing the relationship between the minimum width hb of the throat on the blade root hooks and bending stress occurring at the throat when a circumferential load of 10 kN is applied to the turbine rotor radial outermost portion of the shroud in the respective configurations of FIGS. 6 and 7.

FIG. 9 is a perspective view of a steam turbine blade having the convention grouped blade structure.

Claims

1. A steam turbine blade comprising: a blade;a shroud attached to a tip of the blade;a blade root projecting toward the radial inner circumferential side of a turbine rotor so as to be fitted into a blade groove provided in an outer circumferential portion of the turbine rotor; anda platform disposed between the blade and the blade root;wherein the blade root is inserted into the blade groove along the axial direction of the turbine rotor; andwherein the blade, the shroud, the blade root and the platform are integrally molded; andwherein the number of the blade roots is larger than that of the blades.

2. The steam turbine blade of claim 1, wherein a plurality of the blades form part of a unitary grouped blade having the single shroud and the single platform, the blades, the shroud, the blade roots and the platform are integrally molded, the number of the blades is one through four, and the number of the blade roots is larger than that of the blades.

3. The steam turbine blade of claim 1, wherein adjacent surfaces of at least one of the shrouds adjacent to each other and the platforms adjacent to each other are joined together by any one of welding, brazing, and friction stir welding.

4. The steam turbine blade of claim 1, wherein each of the blade root and the blade groove is symmetrical with respect to the centerline of each of the blade root and the blade groove as viewed from the axial direction of the turbine rotor, the blade root and the blade groove are respectively provided with blade root hooks and blade groove hooks on both sides of the centerline so that the blade root hook and the blade groove hook form a pair on each side of the centerline, andthe blade root hook and the blade groove hook are abutted against each other to support a centrifugal force acting on the steam turbine blade.

5. The steam turbine blade of claim 4, wherein a portion where the blade root hook is in contact with the blade groove hook is provided with a hole adapted to receive a fixing pin joined thereto so as to extend to the blade root hook and the blade groove hook, the fixing pin being inserted into the hole toward the axial direction of the turbine rotor, and the insertion of the fixing pin into the hole fixes the turbine rotor and the blade root with each other in the circumferential and radial directions.

6. The steam turbine blade of claims 1, wherein the blade, the shroud, the blade roots and the platform are integrally molded by precision casting or forging.

7. The steam turbine blade of claims 1, wherein a material strength σrb of the blade root, a material strength σrw of the blade groove, a minimum width hb of a throat on the blade root hook as viewed from the axial direction of the turbine rotor, and a minimum width hw of a throat under the blade groove hook of the turbine rotor as viewed from the axial direction of the turbine rotor are set to fall in a range specified by the following formula: σrb×hb≦σrw×hw.

8. A steam turbine comprising: turbine blades; anda turbine rotor having a plurality of stages into which the turbine blades are inserted;wherein the turbine blade used in at least one of the stages is the steam turbine blade according to claims 1.

9. The steam turbine of claim 8, wherein the at least one of the stages is a control stage.

10. The steam turbine of claim 8, wherein the turbine rotor includes a shaft and a disk contiguous to the shaft, and the disk is formed along the axial direction of the shaft with a plurality of disk portions into which the turbine blades are inserted.

11. A steam turbine power plant in which any one of a high pressure turbine, a high-intermediate pressure integrated type turbine and a high-low pressure integrated type turbine is the steam turbine according to claims 8.