Methods, systems and/or apparatus relating to steam turbine exhaust diffusers

Abstract

An axial flow steam turbine flow path that includes a rotor and a casing defining the axial steam flow path; and a toroidal diffuser for diffusing the exhaust steam and turning the exhaust steam from a generally axial flow direction to a generally transverse or vertical and tangential direction; wherein the toroidal diffuser comprises a diffuser that, at least in part, incorporates the shape of a toroid or a section of a toroid; and wherein a toroid comprises the shape generated by revolving a circular or oval shape in three dimensional space about an axis coplanar with the circular or oval shape, which does not touch the circular or oval shape.

1 . An axial flow steam turbine flow path comprising:
 a rotor and a casing defining the axial steam flow path; and   a toroidal diffuser for diffusing the exhaust steam and turning the exhaust steam from a generally axial flow direction to a generally transverse or vertical and tangential direction.   
   
   
       2 . The flow path according to  claim 1 , wherein the toroidal diffuser comprises a diffuser that, at least in part, incorporates the shape of a toroid or a section of a toroid. 
   
   
       3 . The flow path according to  claim 1 , wherein a toroid comprises the shape generated by revolving a circular or oval shape in three dimensional space about an axis coplanar with the circular or oval shape, which does not touch the circular or oval shape. 
   
   
       4 . The flow path according to  claim 3 , wherein a toroid comprises the shape generated by revolving a circle in three dimensional space about an axis coplanar with the circle, which does not touch the circle. 
   
   
       5 . The flow path according to  claim 1 , wherein a toroidal diffuser comprises:
 a conical guide, which functions as the initial guide for the steam as it exits the last turbine section;   a toroidal section, which defines the upper half of the main chamber of the toroidal diffuser; and   a rectilinear section, which defines the lower half of the main chamber of the diffuser and provides a flow path to an outlet.   
   
   
       6 . The flow path according to  claim 5 , wherein the toroidal section comprises approximately one half of a toroid shape. 
   
   
       7 . The flow path according to  claim 5 , wherein the toroidal section engages the rectilinear section at a circumferential location that is approximately horizontal with the rotor. 
   
   
       8 . The flow path according to  claim 5 , wherein the axis of the toroid that forms the toroidal section comprises the rotor of the turbine. 
   
   
       9 . The flow path according to  claim 5 , wherein the upstream end of the conical guide is coupled to the casing by a flexible joint; and
 wherein the conical guide comprise an outer radial boundary for steam exiting a final stage of the turbine.   
   
   
       10 . The flow path according to  claim 5 , wherein the conical guide includes an expanding conical shape such that the cross-sectional diameter of the conical guide increases as the distance downstream from the flexible joint increases. 
   
   
       11 . The flow path according to  claim 5 , wherein at a downstream end the conical guide comprises a flared lip. 
   
   
       12 . The flow path according to  claim 5 , wherein the conical guide extends into the toroidal section and the rectilinear section. 
   
   
       13 . The flow path according to  claim 12 , wherein the conical guide extends across approximately half the axial width of the toroidal section and the rectilinear section. 
   
   
       14 . The flow path according to  claim 5 , wherein an inner boundary for the steam moving through the conical guide comprises a cylindrical rotor plate that is disposed around the rotor of the turbine, the cylindrical rotor plate comprising a smooth cylindrical shape that substantially encloses the rotor and extends axially from the last stage of the turbine to a downstream wall of the toroidal diffuser. 
   
   
       15 . The flow path according to  claim 1 , wherein the casing and the toroidal diffuser are independently mounted relative to one another on a foundation. 
   
   
       16 . The flow path according to  claim 1 , wherein a flexible connection connects the casing and the toroidal diffuser. 
   
   
       17 . The flow path according to  claim 16 , wherein the flexible connection comprises expansion bellows that are configured to allow for differential thermal expansion. 
   
   
       18 . The flow path according to  claim 1 , wherein bearings for the rotor are supported on one or more stanchions that are directly supported by the foundation of the turbine. 
   
   
       19 . An axial flow steam turbine flow path comprising:
 a rotor and a casing defining the axial steam flow path; and   a toroidal diffuser for diffusing the exhaust steam and turning the exhaust steam from a generally axial flow direction to a generally transverse or vertical and tangential direction;   wherein the toroidal diffuser comprises a diffuser that, at least in part, incorporates the shape of a toroid or a section of a toroid; and   wherein a toroid comprises the shape generated by revolving a circular or oval shape in three dimensional space about an axis coplanar with the circular or oval shape, which does not touch the circular or oval shape.   
   
   
       20 . The flow path according to  claim 19 , wherein a toroidal diffuser comprises:
 a conical guide, which functions as the initial guide for the steam as it exits the last turbine section;   a toroidal section, which defines the upper half of the main chamber of the toroidal diffuser; and   a rectilinear section, which defines the lower half of the main chamber of the diffuser and provides a flow path to an outlet.