Steam turbine and method for adjusting thrust forces thereof

Abstract

A steam turbine having at least a HP blade cascade, an IP blade cascade and a plurality of dummy members that are attached to a common rotor shaft, is provided with, but not limited to, a detection unit that detects a steam flow into an IP chamber, a pressure reducing unit that reduces a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the IP chamber stops, the target dummy member having one side communicating with a part of the IP chamber, and a control unit that controls the pressure reducing unit based on a detection result obtained by the detection unit.

1 . A steam turbine having at least a high-pressure blade cascade, an intermediate-pressure blade cascade and a plurality of dummy members that are attached to a common rotor shaft, the steam turbine comprising:
 a detection unit that detects a steam flow into an intermediate-pressure chamber;   a pressure reducing unit that reduces a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the intermediate-pressure chamber stops, the target dummy member having one side communicating with a part of the intermediate-pressure chamber; and   a control unit that controls the pressure reducing unit based on a detection result obtained by the detection unit.   
     
     
         2 . The steam turbine according to  claim 1 ,
 wherein the pressure reducing unit comprises:   a first conduit that connects the both sides of the target dummy member; and   a first valve that is provided in the first conduit to adjust the pressure difference between the both sides of the target dummy member.   
     
     
         3 . The steam turbine according to  claim 2 , further comprising:
 a third conduit that connects the one side of the pressure reducing unit to an outlet of the intermediate-pressure chamber; and   a third valve that is provided in the third conduit,   wherein, when the first valve opens while the steam flow into the intermediate-pressure chamber is not stopped, the control unit controls the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.   
     
     
         4 . The steam turbine according to  claim 1 ,
 wherein the pressure reducing unit comprises:   a second conduit that connects the part of the intermediate-pressure chamber and the one side of the target dummy member; and   a second valve that is provided in the second conduit to adjust the difference between the both sides of the target dummy member,   wherein the second valve is closed when the steam flow into the intermediate-pressure chamber stops.   
     
     
         5 . The steam turbine according to  claim 4 , further comprising:
 a bypass conduit that is provided to bypass the second valve; and   an orifice that is provided in the bypass conduit.   
     
     
         6 . The steam turbine according to  claim 4 , further comprising:
 a third conduit that connects the one side of the pressure reducing unit to an outlet of the intermediate-pressure chamber; and   a third valve that is provided in the third conduit,   wherein, when the second valve closes while the steam flow into the intermediate-pressure chamber is not stopped, the control unit controls the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.   
     
     
         7 . A method of adjusting a thrust force of a steam turbine having at least a high-pressure blade cascade, an intermediate-pressure blade cascade and a plurality of dummy members that are attached to a common rotor shaft, the method comprising the step of:
 reducing a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the intermediate-pressure chamber stops, the target dummy member having one side communicating with a part of the intermediate-pressure chamber.   
     
     
         8 . The method of adjusting the thrust force of the steam turbine according to  claim 7 ,
 wherein the pressure difference between the both sides of the target dummy member is reducible by use of a first valve provided in a first conduit that connects the both sides of the target dummy member.   
     
     
         9 . The method of adjusting the thrust force of the steam turbine according to  claim 8 ,
 wherein, when the first valve opens while the steam flow into the intermediate-pressure chamber is not stopped, the pressure difference is generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the intermediate-pressure chamber.   
     
     
         10 . The method of adjusting the thrust force of the steam turbine according to  claim 7 ,
 wherein the pressure difference between the both sides of the target dummy member is reducible by use of a second valve provided in a second conduit that connects the part of the intermediate-pressure chamber and the one side of the target dummy member.   
     
     
         11 . The method of adjusting the thrust force of the steam turbine according to  claim 10 ,
 wherein, when the second valve closes while the steam flow into the intermediate-pressure chamber is stopped, the pressure difference is generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the intermediate-pressure chamber.