Gap control arrangement for a gas turbine

Abstract

A screw-type gap control arrangement for a gas turbine with at least one row of variable vanes 2 and with a gas-wetted surface 4 adjacent to a blade row, wherein the surface 4 has essentially the form of a spherical surface ring and, at the same time, a contraction of a gas path with an aerodynamically favorable form of an annulus is obtained.

1 . A screw-type gap control arrangement for a gas turbine with at least one row of variable stator vanes, which at a radially outer end are held by a casing and which are located at a radially inner end on an inner shroud, with the radially inner end of the variable stator vane and a gas-wetted surface of the inner shroud being designed spherically, wherein 
 a radius of a sphere for cutting a stator vane tip is equal to a radial distance from a machine axis to the vane tip at a nodal point of a stator vane rotary axis divided by a sine of an angle of inclination of the stator vane rotary axis to the machine axis,    a radius of the sphere for cutting the inner shroud is smaller than the radius for cutting the inner stator vane tip, to compensate for tolerances or thermal movements,    the angle of inclination is selected such that an aerodynamically required radial height difference between a leading and a trailing edge at the axially sectioned inner shroud is provided, and    a distance of all points on the axially sectioned inner shroud to the machine axis is smaller than the sphere radius.    
   
   
       2 . A screw-type gap control arrangement in accordance with  claim 1 , wherein curvature discontinuities in the gas path are placed in a gap between the inner shroud  3  and a subsequent rotor stage.  
   
   
       3 . A screw-type gap control arrangement in accordance with  claim 2 , wherein a gas flow exposed portion of a screw of the vane is cut by the form of a sphere so as not to extend into and impede the gas flow.  
   
   
       4 . A screw-type gap control arrangement in accordance with  claim 3 , wherein the optimal spherical form is obtained in a hot engine state, and a cold-state geometry produced by machining deviates from the ideal form.  
   
   
       5 . A screw-type gap control arrangement in accordance with  claim 2 , wherein the optimal spherical form is obtained in a hot engine state, and a cold-state geometry produced by machining deviates from the ideal form.  
   
   
       6 . A screw-type gap control arrangement in accordance with  claim 1 , wherein the optimal spherical form is obtained in a hot engine state, and a cold-state geometry produced by machining deviates from the ideal form.  
   
   
       7 . A screw-type gap control arrangement in accordance with  claim 1 , wherein a portion of a screw of the vane lying within the gas flow is cut by the form of a sphere and does not impede the gas flow.  
   
   
       8 . A screw-type gap control arrangement in accordance with  claim 7 , wherein the optimal spherical form is obtained in the a engine state, and a cold-state geometry produced by machining deviates from the ideal form.  
   
   
       9 . A screw-type gap control arrangement for a gas turbine with at least one row of single-end borne variable vanes, which at a radially outer end are held by a casing and at a radially inner end seal against a rotor, with the radially inner end of the variable vane and an area of the rotor being designed spherically, wherein 
 a radius of a sphere for cutting a stator vane tip is equal to a radial distance from a machine axis to the vane tip at a nodal point of a stator vane rotary axis divided by a sine of an angle of inclination of the stator vane rotary axis to the machine axis,    a radius of a sphere for cutting the rotor in the area is smaller than the radius for cutting the inner stator vane tip, to compensate for tolerances or thermal movements,    the angle of inclination is selected such that an aerodynamically required radial height difference in the area of the rotor is provided, and    a distance of all points in the area to the machine axis is smaller than the sphere radius.    
   
   
       10 . A screw-type gap control arrangement in accordance with  claim 9 , wherein the optimal spherical form is obtained in a hot engine state, and a cold-state geometry produced by machining deviates from the ideal form.