Stator blade for a turbomachine, especially a stream turbine

Abstract

The invention relates to a stator blade ( 4 ) of a turbomachine, especially of a steam turbine, which has the following geometric features. A lean curvature, a swept curvature, a twist in the radial direction of the respective blade ( 4 ), a hub-side circumferential step ( 14 ) which in the direction of flow ( 15 ) falls away inwards and radially to the rotational axis ( 8 ) of the turbomachine, a chord length (s) of the blade which varies over the radial extent of the stator blade ( 4 ), and also a cross-sectional profile of the blade ( 4 ) which varies over the radial extent of the stator blade ( 4 ).

1 . A stator blade for a turbomachine, especially for a steam turbine, characterized by the following geometric features:
 a lean curvature perpendicular to the blade chord, essentially in the circumferential direction,   a sweep curvature parallel to the blade chord, essentially in the axial direction of the turbomachine,   a twist in the radial direction of the respective blade,   a hub-side circumferential step, which in the direction of flow falls away inwards and radially to the rotational axis of the turbomachine,   a chord length of the blade which varies over the radial extent of the stator blade,   a cross-sectional profile of the blade which varies over the radial extent of the stator blade.   
     
     
         2 . The stator blade as claimed in  claim 1 , wherein
 the lean curvature varies along the radial blade length, and/or   the lean curvature decreases along the radial blade length from the hub to the casing, and/or   a curvature angle (γ) between a tangent which lies against the blade surface at a trailing edge or at a leading edge of the stator blade, and a radial line which extends orthogonally to the rotational axis of the turbomachine, lies within a range of 0°≦γ≦15°, and/or   the stator blade has a positive lean curvature in the direction of rotation.   
     
     
         3 . The stator blade as claimed in  claim 1 ,
 wherein
 the sweep curvature of the stator blade varies along the radial blade length, and/or 
 the sweep curvature of the stator blade along the radial blade length has a positive value in the region of the hub and has a negative value in the region of the casing, and/or 
 a curvature angle between a meridional tangent which lies against the blade surface at a leading edge or at a trailing edge, and a radial line which extends orthogonally to the rotational axis of the turbomachine, lies within a range of 15°≦δ≦−20°. 
   
     
     
         4 . The stator blade as claimed in  claim 1 ,
 wherein
 a metal angle at the trailing edge is defined between a circumferential line in the circumferential direction of the turbomachine and a tangent to the curvature center line at the trailing edge, and/or 
 the metal angle varies along the radial blade length, and/or 
 the metal angle is larger at the hub than in the region of the casing, and/or 
 the metal angle between a tangent to the curvature center line at the trailing edge of the stator blade and the rotational axis of the turbomachine lies with a range of 25°≦α 2 ≦10°. 
   
     
     
         5 . The stator blade as claimed in  claim 1 ,
 wherein
 the hub-side circumferential step has an S-shaped profile between a leading edge and a trailing edge of the stator blade or extends linearly between the two edges, and/or 
 the leading edge and the trailing edge do not extend in a parallel manner, and/or 
 an angle between a tangent to the circumferential step and the rotational axis of the turbomachine lies within a range of −20°≦β≦20°. 
   
     
     
         6 . The stator blade as claimed in  claim 1 ,
 wherein
 a pitch ratio, that is to say a quotient of a blade spacing between adjacent stator blades in the circumferential direction and a chord length varies over the radial extent of the stator blade, and/or 
 the pitch ratio at the hub is smaller than in the region of the casing, and/or 
 the pitch ratio lies within a range of 0.45≦t/s≦0.75. 
   
     
     
         7 . The stator blade as claimed in  claim 1 ,
 wherein
 an inflow-side incidence angle of the curvature center line varies over the radial blade length of the stator blade, and/or 
 the inflow-side incidence angle of the curvature center line is smaller at the hub than in the region of the casing, and/or 
 the inflow-side incidence angle of the curvature center line lies within a range of 55°≦α 1 ≦110°. 
   
     
     
         8 . The stator blade as claimed in  claim 1 ,
 wherein
 a wedge angle between a surface tangent to a pressure side and a surface tangent to a suction side at a trailing edge of the stator blade varies over the radial blade length of the stator blade, and/or 
 the wedge angle is larger at the hub than in the region of the casing, and/or 
 the wedge angle lies within a range of 15°≦WE≦0°. 
   
     
     
         9 . The stator blade as claimed in  claim 1 ,
 wherein   a narrowest flow cross section between adjacent stator blades shifts from the hub towards the casing against the direction of flow.