Turbine including exhaust hood

Abstract

A turbine includes an inner casing, a rotor extending in a longitudinal direction, and rows of buckets transversely disposed on the rotor. A bearing cone covering a portion of the rotor and a flow guide extending from the inner casing define an annular passage for flow of exhaust gases. Exhaust gas movement is facilitated by a guide cap having a streamlined surface and situated in a downstream direction of the flow guide, a tip leakage flow injection channel to inject exhaust gases at the inner surface of the flow guide, an incline of the casing of the turbine surrounding the last stage buckets relative to the longitudinal axis, or use of a first portion of the annular passage with a substantially constant surface area and a second portion of the annular passage with a progressively increasing surface area.

1 . A turbine comprising:
 an outer casing;   an inner casing enclosed by the outer casing;   a rotor enclosed by the inner casing and extending along a longitudinal axis of the turbine;   a plurality of rows of buckets transversely disposed on the rotor;   a bearing cone surrounding at least a portion of the rotor;   a flow guide extending from the inner casing;   an annular passage for flow of exhaust gases defined by the flow guide and the bearing cone, wherein the bearing cone and the flow guide form an inner wall and an outer wall of the annular passage respectively; and   a guide cap having a streamlined surface provided in a downstream direction of the flow guide.   
     
     
         2 . The turbine according to  claim 1 , wherein the guide cap comprises an airfoil shape. 
     
     
         3 . The turbine according to  claim 1 , wherein the exhaust gases comprise steam. 
     
     
         4 . A turbine comprising:
 an outer casing;   an inner casing enclosed by the outer casing;   a rotor enclosed by the inner casing and extending along a longitudinal axis of the turbine;   a plurality of rows of buckets transversely disposed on the rotor;   a bearing cone surrounding at least a portion of the rotor;   a flow guide extending from the inner casing;   an annular passage for flow of exhaust gases defined by the flow guide and the bearing cone, wherein the bearing cone and the flow guide form an inner wall and an outer wall of the annular passage respectively; and   at least one tip leakage flow injection channel configured to inject flow of exhaust gases at the inner surface of the flow guide to prevent boundary layer separation of the exhaust gases at the inner surface of the flow guide.   
     
     
         5 . The turbine according to  claim 4 , wherein the at least one tip leakage flow injection channel comprises at least one pipe. 
     
     
         6 . The turbine according to  claim 4 , wherein the at least one tip leakage flow injection channel comprises at least one slot in the flow guide. 
     
     
         7 . The turbine according to  claim 4 , wherein the at least one tip leakage flow injection channel is situated at a shoulder portion of the flow guide. 
     
     
         8 . The turbine according to  claim 4 , wherein the exhaust gases comprise steam. 
     
     
         9 . The turbine of  claim 4 , wherein one or more rows of buckets are provided at an optimal radial clearance from the inner casing to energize flow of exhaust gases in the annular passage, wherein the optimal radial clearance is increased by about 8% to 15% relative to a baseline clearance. 
     
     
         10 . A turbine comprising:
 a rotor extending along a longitudinal axis of the turbine;   a plurality of rows of buckets transversely disposed on the rotor; and   a casing surrounding the plurality of rows of buckets,   wherein a portion of the casing for a last row of buckets is inclined at an angle in a range of 5 degrees to 15 degrees with respect to the longitudinal axis.   
     
     
         11 . The turbine according to  claim 10 , wherein the angle is in a range of 6 degrees to 10 degrees with respect to the longitudinal axis. 
     
     
         12 . The turbine according to  claim 10 , wherein the exhaust gases comprises steam. 
     
     
         13 . A turbine comprising:
 an outer casing;   an inner casing enclosed by the outer casing;   a rotor enclosed by the inner casing and extending along a longitudinal axis of the turbine;   a plurality of rows of buckets transversely disposed on the rotor;   a bearing cone surrounding at least a portion of the rotor;   a flow guide extending from the inner casing; and   an annular passage for flow of exhaust gases defined by the flow guide and the bearing cone, wherein the bearing cone and the flow guide form an inner wall and an outer wall of the annular passage respectively,   wherein a first portion of the annular passage comprises a substantially constant surface area and a second portion of the annular passage comprises a progressively increasing surface area.   
     
     
         14 . The turbine according to  claim 13 , wherein in the first portion a radius of curvature of the flow guide is substantially equal to a radius of curvature of the bearing cone. 
     
     
         15 . The turbine according to  claim 14 , wherein in the second portion the radius of curvature of the flow guide is smaller than the radius of curvature of the bearing cone. 
     
     
         16 . The turbine according to  claim 13 , wherein the exhaust gases comprises steam.