Moisture removal provisions for steam turbine

Abstract

Disclosed herein is a moisture removal system for a steam turbine including at least one perforated ring in an outer casing enclosing a stage of the steam turbine. The ring is configured to allow moisture to pass therethrough out of a steam path of the steam turbine.

1 . A moisture removal system for a steam turbine, the system comprising:
 a ring for positioning in an outer casing enclosing a stage of the steam turbine, wherein the ring includes one or more holes extending from an inner diameter to an outer diameter of the ring, the holes configured to allow moisture to pass therethrough out of a steam path of the steam turbine.   
     
     
         2 . The moisture removal system of  claim 1 , wherein the ring is positioned between a bucket and a nozzle of the stage. 
     
     
         3 . The moisture removal system of  claim 2 , further comprising at least one moisture removal slot extending through the outer casing, the slot configured to allow moisture to pass therethrough out of the steam path of the steam turbine. 
     
     
         4 . The moisture removal system of  claim 3 , wherein one moisture removal slot is positioned to be in-line with a trailing edge of a rotating blade of a previous stage bucket. 
     
     
         5 . The moisture removal system of  claim 2 , further comprising:
 a channel extending from a first end within the nozzle and through the outer casing to a second end;   a pressure side slot on a pressure side of the nozzle, the pressure side slot in fluid communication with the first end of the channel; and   a suction side slot on a suction side of the nozzle, the suction side slot in fluid communication with the first end of the channel, the pressure side slot and the suction side slot configured to allow moisture from a surface of the nozzle to flow through the slots into the first end of the channel.   
     
     
         6 . The moisture removal system of  claim 5 , wherein the pressure side slot and the suction side slot extend substantially longitudinally along the nozzle. 
     
     
         7 . The moisture removal system of  claim 5 , wherein the second end of the channel is connected to a source of exhaust pressure. 
     
     
         8 . The moisture removal system of  claim 1 , wherein the ring includes a plurality of rings, at least one first ring positioned downstream of a next-to-last stage bucket and upstream of a nozzle, and at least one second ring positioned upstream of a last stage bucket and downstream of the nozzle, wherein the plurality of rings each include one or more holes extending from an inner diameter to an outer diameter of the ring, the holes configured to allow moisture to pass therethrough out of a steam path of the steam turbine. 
     
     
         9 . The moisture removal system of  claim 8 , further comprising:
 a channel extending from a first end within the nozzle and through the outer casing to a second end;   a pressure side slot on a pressure side of the nozzle, the pressure side slot in fluid communication with the first end of the channel; and   a suction side slot on a suction side of the nozzle, the suction side slot in fluid communication with the first end of the channel, the pressure side slot and the suction side slot configured to allow moisture from a surface of the nozzle to flow through the slots into the first end of the channel.   
     
     
         10 . The moisture removal system of  claim 9 , wherein the pressure side slot and the suction side slot extend substantially longitudinally along the nozzle. 
     
     
         11 . The moisture removal system of  claim 9 , wherein the second end of the channel is connected to a source of exhaust pressure. 
     
     
         12 . The moisture removal system of  claim 8 , further comprising at least one moisture removal slot extending through the outer casing, the slot configured to allow moisture to pass therethrough out of the steam path of the steam turbine. 
     
     
         13 . The moisture removal system of  claim 12 , wherein one moisture removal slot is positioned to be in-line with a trailing edge of a rotating blade of the next-to-last stage bucket. 
     
     
         14 . The moisture removal system of  claim 8 , further comprising one of: a recessed bucket cover on the last stage bucket or an overshooting bucket cover on the last stage bucket. 
     
     
         15 . A moisture removal system for a steam turbine, the steam turbine having a last stage bucket, a next-to-last stage bucket, and a nozzle positioned between the last stage bucket and the next-to-last stage bucket, the nozzle and buckets positioned within an outer casing, the moisture removal system comprising:
 at least one moisture removal slot extending through the outer casing, wherein one moisture removal slot is positioned to be in-line with a trailing edge of a rotating blade of the next-to-last stage bucket;   a first ring in the outer casing, the first ring positioned downstream of the moisture removal slot and upstream of the nozzle, the first ring including one or more holes extending from an inner diameter to an outer diameter of the ring, the holes configured to allow moisture to pass therethrough out of a steam path of the steam turbine;   a channel extending from a first end within the nozzle and through the outer casing to a second end;   a pressure side slot on a pressure side of the nozzle, the pressure side slot in fluid communication with the first end of the channel;   a suction side slot on a suction side of the nozzle, the suction side slot in fluid communication with the first end of the channel, the pressure side slot and the suction side slot configured to allow moisture from a surface of the nozzle to flow through the slots into the first end of the channel;   a second ring in the outer casing, the second ring positioned downstream of the nozzle and upstream of the last stage bucket, the second ring including one or more holes extending from an inner diameter to an outer diameter of the ring, the holes configured to allow moisture to pass therethrough out of a steam path of the steam turbine; and   one of: a recessed bucket cover on the last stage bucket or an overshooting bucket cover on the last stage bucket.   
     
     
         16 . The moisture removal system of  claim 15 , wherein the pressure side slot and the suction side slot extend substantially longitudinally along the nozzle. 
     
     
         17 . The moisture removal system of  claim 15 , wherein the second end of the channel is connected to a source of exhaust pressure.