System and method to reduce acoustic signature using profiled stage design

Abstract

To reduce noise and thereby increase turbine efficiency, the end walls and airfoils of a turbine are designed to reduce or eliminate radial pressure gradients on rotor blades and their incipient secondary flow vortices which may noisily excite downstream blade and vane rows. Instead of generating inefficient noise, the fluid energy may be properly directed into the shaft as efficient work.

1 . A turbine, comprising:
 at least one set of rotor blades mounted radially symmetrically about a rotating shaft, wherein each rotor blade has a hub and a tip; and   at least one stator axially-spaced from the at least one set of rotor blades and mounted radially symmetrically about the rotating shaft, wherein the at least one stator defines a plurality of radially-spaced vanes having inner and outer end walls that define end wall passages, wherein the end wall passages have a profile shaped to direct a working fluid to a plane substantially tangent to the inner and outer end walls.   
     
     
         2 . The turbine of  claim 1 , wherein the profile of the end wall passages is configured to substantially eliminate the radial pressure gradient incident between the hub and the tip of each rotor blade, whereby the resultant acoustic signature of the turbine is attenuated. 
     
     
         3 . The turbine of  claim 1 , wherein the turbine is a multiple-stage steam turbine. 
     
     
         4 . The turbine of  claim 1 , wherein each of the radially-spaced vanes have a convex surface and a concave surface with the convex surface of one vane and the concave surface of an adjacent vane defining the end wall passages. 
     
     
         5 . The turbine of  claim 4 , wherein the convex and concave surfaces are configured to cause the working fluid passing through the end wall passages to follow a path defined by a mean of the adjacent convex and concave surfaces. 
     
     
         6 . The turbine of  claim 1 , wherein the inner and outer end walls are configured to make the working fluid pressure at the hub substantially equal to the working fluid pressure at the tip. 
     
     
         7 . The turbine of  claim 1 , wherein the vanes are configured to direct fluid passing through the end wall passages circumferentially about and radially-spaced from a center line of the turbine. 
     
     
         8 . A stator for a turbine, comprising,
 an inlet and an outlet, wherein the outlet is adjacent to at least one rotor blade having a hub and a tip; and   a plurality of inner and outer end walls extending from the inlet to the outlet and defining a plurality of end wall passages having inner and outer radial limits, wherein the end wall passages have a profile configured to direct a working fluid to a plane substantially tangent to the inner and outer radial limits, wherein the plurality of inner and outer end walls are configured to substantially eliminate the radial pressure gradients incident between the hub and the tip of the at least one rotor blade, thereby attenuating resultant acoustic signature.   
     
     
         9 . The stator of  claim 8 , wherein, taken along an axial cross-sectional view, the tip of the at least one rotor blade is substantially tangent to the outer radial limit and the hub of the at least one rotor is substantially tangent to the inner radial limit. 
     
     
         10 . The stator of  claim 8 , wherein the profile is configured to direct fluid passing through the end wall passages circumferentially about and radially-spaced from a center line of the turbine. 
     
     
         11 . A method of reducing turbine acoustic signature, comprising:
 introducing a working fluid into a turbine having at least one stator adjacent to and axially-spaced from at least one rotor blade, wherein the stator comprises a plurality of radially-spaced vanes, each vane having an inlet and an outlet and defining a profile of an end wall passage including an inner and outer end wall;   receiving the working fluid through the inlet of the end wall passage;   channeling the working fluid through the profile of the end wall passage; and   directing the working fluid out the outlet of the vane and substantially tangent to the inner and outer end walls, thereby substantially decreasing the radial pressure gradient incident between a hub and a tip of the at least one rotor blade, and thereby attenuating resultant acoustic signature.   
     
     
         12 . The method of  claim 11 , wherein the turbine is a multiple-stage turbine and the working fluid is steam. 
     
     
         13 . The method of  claim 11 , wherein each of the radially-spaced vanes have a convex surface and a concave surface with the convex surface of one vane and the concave surface of an adjacent vane defining the end wall passages 
     
     
         14 . The method of  claim 11 , wherein, taken along an axial cross-sectional view, the tip of the at least one rotor blade is substantially tangent to the outer end wall of the end wall passage and the hub of the at least one rotor blade is substantially tangent to the inner end wall of the end wall passage. 
     
     
         15 . The method of  claim 11 , wherein each of the radially-spaced vanes have a convex surface and a concave surface with the convex surface of one vane and the concave surface of an adjacent vane defining the end wall passages. 
     
     
         16 . The method of  claim 15 , wherein the convex and concave surfaces are configured to cause the working fluid passing through the end wall passages to follow a path defined by the mean of the adjacent convex and concave surfaces. 
     
     
         17 . The method of  claim 11 , wherein the convex and concave surfaces are configured to cause the working fluid passing through the end wall passages to follow a path defined by the concave surface. 
     
     
         18 . The method of  claim 11 , wherein the convex and concave surfaces are configured to cause the working fluid passing through the end wall passages to follow a path defined by the convex surface. 
     
     
         19 . The method of  claim 11 , wherein the working fluid one of air, products of combustion, or a process fluid such as carbon dioxide.