Steam turbomachine having a bypass circuit for throttle flow capacity adjustment

Abstract

A steam turbomachine includes a housing having a shell that defines a steam flow path, a first stage bowl cavity formed in the shell, a first stage including a plurality of first stage nozzles and a plurality of first stage buckets arranged downstream of the plurality of first stage nozzles, a second stage including a plurality of second stage nozzles and a plurality of second stage buckets arranged downstream of the plurality of second stage nozzles. The second stage is arranged downstream of the first stage along the steam flow path. A bypass circuit is formed in the shell. The bypass circuit extends from a first end fluidically connected to the first stage bowl cavity to a second end fluidically exposed to the steam flow path upstream of the second stage. A valve element is positioned in, and selectively blocks, the bypass circuit.

What is claimed is: 
     
         1 . A steam turbomachine comprising:
 a housing having a shell that defines a steam flow path;   a first stage bowl cavity formed in the shell;   a first stage including a plurality of first stage nozzles and a plurality of first stage buckets arranged downstream of the plurality of first stage nozzles;   a second stage including a plurality of second stage nozzles and a plurality of second stage buckets arranged downstream of the plurality of second stage nozzles, the second stage being arranged downstream of the first stage along the steam flow path;   a bypass circuit formed in the shell, the bypass circuit extending from a first end fluidically connected to the first stage bowl cavity to a second end fluidically exposed to the steam flow path upstream of the second stage; and   a valve element positioned in and selectively blocking the bypass circuit.   
     
     
         2 . The steam turbomachine according to  claim 1 , further comprising: a valve element access passage extending through the shell, the valve element access passage being fluidically connected to the bypass circuit. 
     
     
         3 . The steam turbomachine according to  claim 2 , wherein the shell includes an inner shell and an outer shell, wherein the valve element access passage includes a first passage portion extending through the inner shell and a second passage portion extending through the outer shell, the first passage portion being aligned with the second passage portion. 
     
     
         4 . The steam turbomachine according to  claim 2 , wherein the valve element access passage includes a threaded region configured and disposed to engage with the valve element. 
     
     
         5 . The steam turbomachine according to  claim 4 , wherein the valve element includes a threaded portion configured to engage with the threaded region. 
     
     
         6 . The steam turbomachine according to  claim 5 , wherein the valve element includes a non-threaded portion extending from the threaded portion, the non-threaded portion extending into the bypass circuit. 
     
     
         7 . The steam turbomachine according to  claim 2 , further comprising: a locking member arranged in the valve element access passage outboard of the valve element, the locking member preventing inadvertent removal of the valve element from the valve element access passage. 
     
     
         8 . The steam turbomachine according to  claim 1 , further comprising: a recess formed in the shell and fluidically connected with the bypass circuit, the recess extending annularly about the housing. 
     
     
         9 . The steam turbomachine according to  claim 8 , further comprising: one or more bypass grooves extending from the recess to the steam flow path. 
     
     
         10 . The steam turbomachine according to  claim 9 , further comprising a nozzle diaphragm assembly connected with one of the plurality of second stage nozzles, each of the one or more bypass grooves extending across the nozzle diaphragm assembly. 
     
     
         11 . The steam turbomachine according to  claim 10 , wherein the one or more bypass grooves are formed on an upstream surface of the nozzle diaphragm assembly. 
     
     
         12 . The steam turbomachine according to  claim 1 , wherein the second end of the bypass circuit is fluidically exposed to the steam flow path upstream of the plurality of second stage nozzles. 
     
     
         13 . A method of adjusting throttle capacity in a steam turbomachine, the method comprising:
 guiding steam along a steam flow path of the steam turbomachine, the steam passing through at least a first stage and a second stage; and   delivering an amount of steam from a first stage bowl cavity to the steam flow path upstream of the second stage bypassing the first stage.   
     
     
         14 . The method of  claim 13 , wherein delivering the amount of steam includes selectively guiding steam through a bypass circuit that fluidically connects the first stage bowl cavity and the stem flow path upstream of the second stage. 
     
     
         15 . The method of  claim 14 , wherein selectively guiding steam through the bypass circuit includes selectively adjusting a cross-sectional area of the bypass circuit. 
     
     
         16 . The method of  claim 15 , wherein selectively adjusting the cross sectional area of the bypass circuit includes selectively positioning a valve element along a valve element access passage that bisects the bypass circuit. 
     
     
         17 . The method of  claim 16 , wherein selectively positioning the valve element includes one of threading the valve element into the valve element access passage and threading the valve element out of the valve element access passage. 
     
     
         18 . The method of  claim 16 , wherein selectively positioning the valve element includes removing the valve element from the bypass circuit. 
     
     
         19 . The method of  claim 16 , wherein selectively positioning the valve element includes removing the valve element from the valve element access passage. 
     
     
         20 . The method of  claim 16 , further comprising: installing a locking member in the valve element access passage to prevent movement of the valve element.