Apparatus and Method for Controlling a Gas Stream Temperature or Rate of Temperature Change

Abstract

The invention provides various designs of an apparatus and method for attemperating a gas stream temperature. The apparatus of the present invention provides a body through which a gas stream passes that permits, as desired, a second gas, such as gas outside of the gas duct or such as ambient air, to be added to the main gas stream to attemperate the temperature of the main gas stream. The body or device may be referred to as a variable eductor having a plurality of openings through which a second gas may pass into the main gas stream. The openings may be opened or closed, and the variable eductor provides control over which openings and the degree to which each opening is opened. In some designs the variable eductor is inserted between two portions of a gas duct. The variable eductor has widespread application, such as downstream of a gas turbine to attemperate the exhaust gas temperature during startup.

What is claimed is: 
     
         1 . An apparatus for controlling a temperature of a gas stream, comprising:
 a first body having a first end and a second end and defining a passageway for passing a gas stream having a temperature from said first end to said second end, wherein said body defines at least one opening through which a second gas from outside of said passageway can pass into said passageway; and   at least one second body attached to said first body adjacent to said at least one opening that moves between a first position and a second position, wherein said at least one second body closes said at least one opening at said first position and opens said at least one opening at said second position, thereby permitting the second gas to pass through said at least one opening into said passageway to change the temperature of the gas stream.   
     
     
         2 . The apparatus of  claim 1 , wherein said first body comprises an outer surface defining the passageway, wherein said at least one opening comprises a plurality of openings in said outer surface, wherein said at least one second body comprises a plurality of shutters each movably connected to said outer surface and adjacent to a corresponding one of said openings, and wherein each of said shutters opens inwardly into the passageway. 
     
     
         3 . The apparatus of  claim 2 , wherein each of said plurality of shutters is configured to independently move to a plurality of positions between said first position and said second position, and wherein each of said plurality of positions has a corresponding flow rate of the second gas through each of said corresponding openings. 
     
     
         4 . The apparatus of  claim 3 , further comprising:
 at least one control mechanism configured to open at least one of said plurality of shutters to at least one of said plurality of positions and configured to close said at least one of said plurality of shutters.   
     
     
         5 . The apparatus of  claim 1 , wherein said first body is configured to attach to a first gas duct at said first end and to a second gas duct at said second end to pass the gas stream from the first gas duct through said passageway to the second gas duct. 
     
     
         6 . The apparatus of  claim 1 , further comprising:
 a gas turbine having an exhaust gas outlet duct that is fluidly connected to said first body at said first end; and   a heat recovery steam generator that is fluidly connected to said first body at said second end.   
     
     
         7 . The apparatus of  claim 1 , wherein said first end is configured to receive an end of a gas duct providing the gas stream; wherein said at least one opening is defined between said first body and the gas duct; wherein said first body is configured to slide between a first position and a second position; wherein said second body comprises a collar attached to an inside surface of said first body that traverses said at least one opening and seals against an outer surface of the gas duct when said first body is in said first position, thereby closing said at least one opening, and that is separated from the outer surface of the gas duct when said first body is in a second position, thereby permitting the second gas to pass through said at least one opening into said passageway. 
     
     
         8 . The apparatus of  claim 8 , wherein said first body is configured to slide between a plurality of positions between said first position and said second position, thereby partially opening said at least one opening. 
     
     
         9 . The apparatus of  claim 8 , wherein said first body comprises a cylindrical shape. 
     
     
         10 . The apparatus of  claim 8 , further comprising:
 a gas turbine having an exhaust gas outlet, wherein the gas duct is fluidly connected to said exhaust gas outlet; and   a heat recovery steam generator having a gas stream inlet that is fluidly connected to said first body at said second end.   
     
     
         11 . The apparatus of  claim 1 , wherein said first end of said first body is configured to receive an end of a gas duct providing the gas stream; wherein said at least one opening is defined between said first body and the gas duct; wherein said second body comprises a first collar attached to an inside surface of said first body that traverses said at least one opening and that defines a plurality of openings; wherein the gas duct comprises a second collar disposed on its outer surface adjacent to said first collar that defines a second plurality of openings, each one of said second plurality of openings corresponding to one of said first plurality of openings; and wherein said first body is configured to rotate between a first position at which said first plurality of openings is offset from said second plurality of openings and a second position at which said first plurality of openings is at least partially aligned with said second plurality of openings thereby permitting the second gas to pass through said at least one opening into said passageway. 
     
     
         12 . The apparatus of  claim 12 , wherein said body is configured to rotate to a plurality of positions. 
     
     
         13 . The apparatus of  claim 1 , wherein said first end of said first body is configured to receive an end of a gas duct providing the gas stream; wherein said at least one opening is defined between said first body and the gas duct; wherein said second body comprises a collar attached to an inside surface of said first body that traverses said at least one opening and that defines a plurality of openings and a plurality of shutters each movably connected to said collar and adjacent to a corresponding one of said openings, and wherein each of said shutters opens inwardly toward said passageway. 
     
     
         14 . An apparatus for controlling a temperature of a gas stream, comprising:
 a first body having a first end and a second end and defining a passageway for passing a gas stream having a temperature from said first end to said second end, wherein said body defines at least one opening through which a second gas from outside of said passageway can pass into said passageway; and   at least one second body attached to said first body adjacent to said at least one opening that moves between a first position and a second position, wherein said at least one second body closes said at least one opening at said first position and opens said at least one opening at said second position, thereby permitting the second gas to pass through said at least one opening into said passageway to change the temperature of the gas stream; and   at least one control mechanism configured to move said at least one second body between said first position and said second position.   
     
     
         15 . The apparatus of  claim 15 , further comprising:
 a gas turbine having an exhaust gas outlet duct that is fluidly connected to said first end of said first body; and   a heat recovery steam generator that is fluidly connected to said second end of said first body.   
     
     
         16 . A method for controlling a temperature of a gas stream, comprising:
 passing a gas stream having a first gas temperature through a gas duct, wherein a portion of the gas duct comprises a first body having a first end and a second end and defining a passageway for passing the gas stream from said first end to said second end, wherein said body defines at least one opening, and at least one second body attached to said first body adjacent to said at least one opening to open and close said at least one opening;   moving said second body to open said at least one opening, thereby creating a gas pressure lower than a gas pressure of a gas outside of said passageway, wherein said gas outside of said passageway has a second gas temperature different from said first gas temperature, and pulling the gas outside of said passageway into said passageway and into the gas stream, thereby changing the temperature of the gas stream.   
     
     
         17 . The method of  claim 17 , further comprising:
 monitoring the first gas temperature of the gas stream; and   controlling a degree of opening of at least one of the plurality of openings in response to said monitoring.   
     
     
         18 . The method of  claim 17 , wherein said gas duct comprises a inlet end and an outlet end, wherein said passing comprises passing the gas stream from a gas turbine to said inlet end of said gas duct and through said duct to said outlet end, and further comprising:
 passing the gas stream from said outlet end to a heat recovery stream generator.   
     
     
         19 . The method of  claim 19 , wherein said passing the gas stream from the gas turbine is performed during a startup of the gas turbine.