Exhaust gas stack

Abstract

An exhaust gas stack includes an elongate, tubular stack member having inlet and outlet ends and a central longitudinal axis. An end section is mounted on the outlet end and has open first and second ends, the first end connected to the outlet end of the stack member and a frustoconical passage extending between these ends. An inner duct section has a central axis co-axial with the axis of the stack member and is mounted centrally in the end section. An annular gas passage is formed between the duct section and the end section. An air plug is movable between an open position at which exhaust gases can flow through the inner duct section and another position at which the plug restricts or prevents passage of exhaust gases through this duct section. An actuator is connected to the plug in order to move it between an open and other positions.

1 . An exhaust gas stack comprising:
 an elongate, tubular stack member having an inlet end, an outlet end, a central longitudinal first axis, and an exhaust gas passage extending between said inlet and outlet ends, said stack member adapted to extend vertically with said inlet end being a bottom end when said exhaust gas stack is installed for use;   an end section mounted on said outlet end and having open first and second ends and a frustoconical passage extending between the first and second ends, said first end being connected to the outlet end of said stack member;   an inner duct section, which is substantially circular in transverse cross-section, has a first duct end, an open second duct end, and a central, longitudinal axis coaxial with said first axis, said duct section being mounted centrally in said passage in the end section whereby a gas flow passage is formed around the duct section and between the duct section and the end section, said duct section having a first axial portion adjacent said first duct end and a second axial portion adjacent said second duct end with the two axial portions meeting at an annular junction of reduced diameter relative to the diameter of said first axial portion at said first duct end;   an air plug member movable between an open position at which exhaust gases can flow past said plug member and through said inner duct section and another position at which said plug member restricts or prevents flow of exhaust gases through said inner duct section; and   an actuator connected to said plug member and capable of moving said plug member between said open position and said closed position.   
     
     
         2 . An exhaust gas stack according to  claim 1  wherein an annular duct wall forming said first axial portion of the inner duct section curves radially inwardly and upwardly as seen in cross-section through said central, longitudinal axis of the duct section and said second axial portion has a frustoconical shape which diverges upwardly from said annular junction. 
     
     
         3 . An exhaust gas stack according to  claim 2  wherein said plug member has a hemispherical top portion with a convex exterior surface directed upwardly during use of said stack and a substantially cylindrical skirt extending from said top portion towards the inlet end of the stack member. 
     
     
         4 . An exhaust gas stack according to  claim 3  wherein a section of said convex exterior surface of the plug member extends parallel to and is spaced apart from said annular duct wall when said plug member is in the open position. 
     
     
         5 . An exhaust gas stack according to  claim 1  wherein an elongate central airflow-defining member is mounted in said stack member, extends along at least a substantial major portion of said longitudinal first axis, and has a top end arranged adjacent said air plug member. 
     
     
         6 . An exhaust gas stack according to  claim 5  wherein said airflow defining member has a substantially cylindrical exterior shell made of sheet metal perforated with numerous small holes distributed over at least a substantial major portion of the exterior shell and containing sound attenuating material arranged within said exterior shell in the region of said numerous small holes. 
     
     
         7 . An exhaust gas stack according to  claim 1  wherein said actuator includes a linear actuator unit mounted in said stack member along the longitudinal first axis and an elongate connecting member extending from said actuator unit to said plug member and operatively connected to said actuator unit so as to be axially movable thereby in order to move said plug member between said open position and said closed position. 
     
     
         8 . An exhaust gas stack according to  claim 5  wherein said actuator includes a linear actuator unit mounted in said airflow-defining member, and said exhaust gas stack includes an electronic controller for controlling operation of said linear actuator and a sensor located at said end section for measuring velocity pressure of exhaust gases flowing from said end section and generating an electrical signal indicative thereof, said sensor being electrically connected to said controller and wherein said controller is programmed to operate said actuator unit from electrical input that includes said electrical signal so as to move said plug member to a controller calculated position amongst a range of positions between said open and closed positions in order to seek or maintain desired airflow velocity for the exhaust gases flowing from said end section of the stack. 
     
     
         9 . An exhaust stack according to  claim 8  wherein said airflow defining member has a substantially cylindrical exterior shell made of sheet metal perforated with numerous small holes distributed over at least a substantial major portion of the exterior shell and containing sound attenuating material arranged within said exterior shell in the region of said numerous small holes. 
     
     
         10 . An exhaust stack according to  claim 1  including an air induction collar extending around and mounted on said end section, said collar during use of said exhaust stack providing induction of outside air into the flow of exhaust gases from said second end of the end section. 
     
     
         11 . A velocity control apparatus for use at a top end of an exhaust stack, said apparatus comprising:
 a hollow member adapted for mounting on said top end of the exhaust stack and having open first end, an open second end of smaller diameter than the first end, and a frustoconical passage extending between the first and second ends, said first end being connected to said top end during use of said apparatus;   an inner duct section having a first duct end, an open second duct end, and a central longitudinal axis which is aligned with a central longitudinal axis of said exhaust stack when said apparatus is mounted on the exhaust stack, said duct section being mounted centrally in said hollow member whereby a gas flow passage is formed around the duct section and between the duct section and the hollow member;   an air plug member movable between an open position at which exhaust gases can flow past said plug member and through said inner duct section and another position at which said plug member restricts or prevents flow of exhaust gases through said inner duct section and thereby at least reduces the amount of exhaust gases flowing through said inner duct section during use of said apparatus; and   an actuator connected to said plug member and adapted to move said plug member between said open and said another position.   
     
     
         12 . A velocity control apparatus according to  claim 11  wherein said inner duct section has a first axial portion adjacent said first duct end and a second axial portion adjacent said second duct end, the two axial portions meet at an annular junction of reduced diameter relative to the diameter of said first axial portion at said first duct end, and said second axial portion has a frustoconical shape which diverges in an axial direction away from said junction. 
     
     
         13 . A velocity control apparatus according to  claim 11  wherein said plug member has a hemispherical top portion with a convex exterior surface directed upwardly during use of said apparatus and a substantially cylindrical skirt extending from said top portion towards an inlet end of the exhaust stack during use of said apparatus. 
     
     
         14 . A velocity control apparatus according to  claim 11  wherein said actuator includes a linear actuator unit adapted for mounting in said exhaust stack and an elongate connecting member capable of extending from said actuator unit to said plug member and of being connected to said actuator unit so as to be movable lengthwise thereby in order to move said plug member between said open position and said another position. 
     
     
         15 . A velocity control apparatus according to  claim 11  wherein said actuator includes a linear actuator unit adapted for mounting in said exhaust stack and said apparatus further includes an electronic controller for controlling operation of said linear actuator and a sensor for measuring velocity pressure of exhaust gases flowing from said hollow member and generating electrical input signals indicative thereof, said sensor being electrically connected to said controller, and wherein said controller is programmed to operate said actuator unit upon receiving said electrical signals so as to move said plug member to a controller calculated position amongst a range of possible positions between said open position and said another position in order to seek or maintain a desired airflow velocity for the exhaust gases flowing from said hollow member. 
     
     
         16 . An exhaust gas stack comprising:
 an elongate, tubular stack member having an inlet end, an outlet end, and an exhaust gas passage extending between said inlet and outlet ends, said stack member adapted to extend vertically upwardly from said inlet end when said stack is installed for use, said stack member including an exterior wall, an interior wall made of perforated sheet metal having numerous small holes distributed over its surface and spaced inwardly from said exterior wall, and sound attenuating material sandwiched between said exterior wall and said interior wall;   an elongate central airflow defining member mounted in said stack member and having a central, longitudinal axis which is coaxial with a central, longitudinal axis of said stack member, said exhaust gas passage being an annular passage along the length of the airflow defining member, said airflow defining member having a sheet metal exterior shell perforated with numerous small holes distributed over at least a substantial portion of the exterior shell and containing sound attenuating material arranged within said exterior shell;   an end section mounted on said outlet end of the stack member and having an open first end, an open second end, and a frustoconical passage that tapers upwardly from the first end to the second end, said first end being connected to the outlet end of the stack member; and   an exhaust gas velocity control mechanism having an inner duct section which is coaxial with and mounted in said end section and an air plug member movable between an open position at which exhaust gases can flow through said inner duct section and another position at which said plug member restricts or prevents passage of exhaust gases through said inner duct section, a further passage being formed around said inner duct section between this duct section and the end section.   
     
     
         17 . An exhaust gas stack according to  claim 16  wherein said control mechanism includes a linear actuator connected by an elongate connecting member to said plug member and capable of moving said plug member between said open position and said another position, said linear actuator is mounted in a lower portion of said airflow defining member, and said connecting member extends along said longitudinal axis of the airflow defining member. 
     
     
         18 . An exhaust gas stack according to  claim 16  wherein said air plug member has a rounded top portion adapted to engage an interior surface of said inner duct section in said another position and a substantially cylindrical skirt portion extending from said top portion towards said inlet end of the stack member and wherein said exterior shell of said airflow defining member is substantially cylindrical and has a substantially hollow upper portion, said skirt portion being mounted for telescoping, sliding movement in said hollow upper portion. 
     
     
         19 . An exhaust gas stack according to  claim 16  including a drain system for draining off water that enters an upper portion of the airflow defining member via the second end of said end section, wherein an inlet of said drain system is arranged above the substantial portion of the exterior shell containing sound attenuating material.