FLOW DISTRIBUTION OF GAS TURBINE EXHAUST USING WALLS SHAPED TO FACILITATE IMPROVED GAS FLOW
A gas turbine transition into an emission reduction catalyst is improved by adding properly curved surfaces so as to induce the Coanda effect. Such a surface allows for a reduction in pressure drop, shorter duct lengths, and elimination of some or all of traditionally used flow re-distribution devices.
1 . An exhaust duct for a gas turbine comprising:
a transition section having a top wall, a first side wall, a second side wall, and a bottom wall, said transition section having an intake for receiving turbine exhaust gas and a relatively larger outlet area;
wherein at least one of said top wall, said first side wall, said second side wall and said bottom wall define a curved surface; and
wherein said curved surface is between said intake and said outlet area.
2 . The exhaust duct according to claim 1 wherein:
said outlet area is sized to accommodate a catalyst having one of a height and width greater than a corresponding height and width of said intake.
3 . The exhaust duct according to claim 1 wherein:
said curved surface may be described by a second degree polynomial equation, thereby continuously expanding an area of said transition section as a distance from said intake is increased.
4 . The exhaust duct according to claim 1 wherein:
said curved surface may be described by a third degree polynomial equation.
5 . The exhaust duct according to claim 1 wherein:
said curved surface increases in slope as a function of distance from said intake.
6 . The exhaust duct according to claim 1 wherein:
said curved surface has a section that increases in slope and a second section that decreases in slope as a function of distance from said intake.
7 . The exhaust duct according to claim 1 wherein:
said curved surface has a section with a negative slope and has a section with a positive slope.
8 . A gas turbine unit comprising:
a gas turbine having an outlet for gas turbine exhaust;
an exhaust duct having an intake for receiving said gas turbine exhaust, said exhaust duct having a transition section and an expanded area;
said transition section having a top wall, a first side wall, a second side wall, and a bottom wall, and an outlet area having a larger cross-section area than a cross-sectional area of said inlet;
wherein said outlet area is adjacent to said expanded area;
wherein at least one of said top wall, said first side wall, said second side wall and said bottom wall of said transition section define a curved surface; and
wherein said curved surface is between said intake and said outlet area.
9 . The gas turbine unit according to claim 8 wherein:
said outlet area is sized to accommodate a catalyst having one of a height and width greater than a corresponding height and width of said intake.
10 . The gas turbine unit according to claim 8 wherein:
said curved surface may be described by a second degree polynomial equation, thereby continuously expanding an area of said transition section as a distance from said intake is increased.
11 . The gas turbine unit according to claim 8 wherein:
said curved surface may be described by a third degree polynomial equation.
12 . The gas turbine unit according to claim 8 wherein:
said curved surface increases in slope as a function of distance from said intake.
13 . The gas turbine unit according to claim 8 wherein:
said curved surface has a section that increases in slope and a second section that decreases in slope as a function of distance from said intake.
14 . The gas turbine unit according to claim 8 wherein:
said curved surface has a section with a negative slope and has a section with a positive slope.