Steam turbine

Abstract

In a steam turbine including a turbine rotor 7; a moving blade 1 secured to the turbine rotor 7; a shroud 3 provided on an outer circumferential side distal end of the moving blade 1; and an outer circumferential side stationary wall 4 internally embracing the turbine rotor 7 and forming an outer circumferential side passage wall of a steam path, the shroud 3 has an inner circumferential surface 14 so formed that a moving blade outlet flare angle α 3 is greater than a moving blade inlet flare angle α 2 ; an angle α 1 formed between the outer circumferential side stationary wall 4 and the turbine central axis 50 is generally equal to the moving blade inlet flare angle α 2 ; and an angle α 4 formed between the outer circumferential side stationary wall and an turbine central axis 50 is generally equal to the moving blade outlet flare angle α 3 .

1 . A moving blade for a steam turbine, the moving blade having a shroud formed at an external circumferential side distal end,
 wherein the shroud has an inner circumferential surface so formed that:   a moving blade outlet flare angle is greater than a moving blade inlet flare angle;   the moving blade inlet flare angle is generally equal to a moving blade upstream side flare angle of an outer circumferential side stationary wall adjacently provided on an upstream side of the shroud; and   the moving blade outlet flare angle is generally equal to a moving blade downstream side flare angle of the outer circumferential side stationary wall adjacently provided on a downstream side of the shroud.   
   
   
       2 . The moving blade according to  claim 1 ,
 wherein an outer circumferential surface of the shroud has a surface including a downstream side distal end and being parallel to a turbine central axis, and   a distance between an upstream side distal end of the outer circumferential surface and the turbine central axis is smaller than a distance between the downstream side distal end of the outer circumferential surface and the turbine central axis.   
   
   
       3 . The moving blade according to  claim 1 ,
 wherein an outer circumferential surface of the shroud is formed of a surface generally parallel to a turbine central axis, and   the shroud is hollow.   
   
   
       4 . The moving blade according to  claim 2 ,
 wherein the moving blade constitutes a final stage of a low-pressure turbine.   
   
   
       5 . The moving blade according to  claim 3 ,
 wherein the moving blade forms an extraction stage adjacently provided on an upstream side of an extraction channel adapted to extract steam from a steam passage.   
   
   
       6 . A steam turbine comprising:
 a turbine rotor;   a moving blade secured to the turbine rotor;   a shroud provided on an outer circumferential side distal end of the moving blade; and   an outer circumferential side stationary wall internally embracing the turbine rotor, the stationary wall forming an outer circumferential side passage wall of a steam path;   wherein the shroud has an inner circumferential surface so formed that:   a moving blade outlet flare angle is greater than a moving blade inlet flare angle;   the moving blade inlet flare angle is generally equal to a moving blade upstream side flare angle of an outer circumferential side stationary wall adjacently provided on an upstream side of the moving blade; and   the moving blade outlet flare angle is generally equal to a moving blade downstream side flare angle of the outer circumferential side stationary wall adjacently provided on a downstream side of the moving blade.   
   
   
       7 . The steam turbine according to  claim 6 ,
 wherein an outer circumferential surface of the shroud has a surface including a downstream side distal end and being parallel to a turbine central axis, and   a distance between an upstream side distal end of the outer circumferential surface and the turbine central axis is smaller than a distance between the downstream side distal end of the outer circumferential surface and the turbine central axis.   
   
   
       8 . The steam turbine according to  claim 6 ,
 wherein an outer circumferential surface of the shroud is formed of a surface generally parallel to a turbine central axis, and   the shroud is hollow.