Contoured axial-radial exhaust diffuser

Abstract

In accordance with one embodiment, a system includes a gas turbine diffuser. The gas turbine diffuser includes an axial diffuser section including a first duct portion having an axial flow path along a centerline of the gas turbine diffuser. The gas turbine diffuser also includes an axial-radial diffuser section coupled to the axial diffuser section, wherein the axial-radial diffuser section includes a second duct portion having a curved flow path along the centerline from the axial flow path to a radial flow path and the axial-radial diffuser section excludes any turning vane in the second duct portion.

1 . A system, comprising:
 a gas turbine diffuser, comprising:
 an axial diffuser section comprising a first duct portion having an axial flow path along a centerline of the gas turbine diffuser, wherein the first duct portion has a first cross-sectional area that expands along the axial flow path; and 
 an axial-radial diffuser section coupled to the axial diffuser section, wherein the axial-radial diffuser section comprises a second duct portion having a curved flow path along the centerline from the axial flow path to a radial flow path, the second duct portion has a second cross-sectional area that expands along the curved flow path, the curved flow path has a radius of at least greater than or equal to approximately 30 centimeters, and the axial-radial diffuser excludes any turning vane in the second duct portion. 
   
     
     
         2 . The system of  claim 1 , wherein the gas turbine diffuser comprises a radial diffuser section coupled to the axial-radial diffuser section, the radial diffuser section comprises a third duct portion having the radial flow path along the centerline of the gas turbine diffuser, and the third duct portion has a third cross-sectional area that expands along the radial flow path. 
     
     
         3 . The system of  claim 1 , wherein the radius is at least greater than or equal to approximately 100 centimeters. 
     
     
         4 . The system of  claim 1 , wherein the second duct portion comprises a first curved wall offset from a second curved wall, the first curved wall curves along the curved flow path with a first radius of curvature, and the second curved wall curves along the curved flow path with a second radius of curvature. 
     
     
         5 . The system of  claim 4 , wherein the first curved wall is proximate relative to a rotational axis of a gas turbine, and the second curved wall is distal relative to the rotational axis of the gas turbine. 
     
     
         6 . The system of  claim 4 , wherein the first and second radii are the same as one another. 
     
     
         7 . The system of  claim 4 , wherein the first and second radii are different from one another. 
     
     
         8 . The system of  claim 4 , wherein the first and second curved walls diverge from one another along the curved flow path. 
     
     
         9 . The system of  claim 1 , wherein the first duct portion comprises a first wall offset from a second wall, the first wall is proximate relative to a rotational axis of a gas turbine, the second wall is distal relative to the rotational axis of the gas turbine, and the first and second walls diverge from one another along the axial flow path. 
     
     
         10 . The system of  claim 9 , wherein the first wall extends along the axial flow path at a first angle relative to the rotational axis, the second wall extends along the axial flow path at a second angle relative to the rotational axis, and the first and second angles are not 0 degrees. 
     
     
         11 . The system of  claim 10 , wherein the first angle is less than or equal to approximately 8 degrees, and the second angle is greater than or equal to approximately 16 degrees. 
     
     
         12 . The system of  claim 10 , wherein the second duct portion comprises a first curved wall offset from a second curved wall, the first curved wall curves along the curved flow path with a first radius of curvature, the second curved wall curves along the curved flow path with a second radius of curvature, and the first and second angles of the first duct portion extend directly to the first and second curved walls. 
     
     
         13 . A system, comprising:
 a gas turbine diffuser, comprising:
 an axial diffuser section comprising a first duct portion having an axial flow path along a centerline of the gas turbine diffuser; and 
 an axial-radial diffuser section coupled to the axial diffuser section, wherein the axial-radial diffuser section comprises a second duct portion having a curved flow path along the centerline from the axial flow path to a radial flow path, and the axial-radial diffuser section excludes any turning vane in the second duct portion. 
   
     
     
         14 . The system of  claim 13 , wherein the first duct portion comprises first and second walls disposed opposite from one another about the axial flow path, the first wall is configured to mount nearer to a rotational axis of a turbine than the second wall, the first wall extends along the axial flow path at a first angle relative to the rotational axis, the second wall extends along the axial flow path at a second angle relative to the rotational axis, and the first and second angles are not 0 degrees. 
     
     
         15 . The system of  claim 14 , wherein the second duct portion comprises first and second curved walls disposed opposite from one another about the curved flow path, the first curved wall is configured to mount nearer to the rotational axis than the second curved wall, the first curved wall curves along the curved flow path with a first radius of curvature, the second curved wall curves along the curved flow path with a second radius of curvature, and the first and second angles of the first duct portion extend toward the first and second curved walls. 
     
     
         16 . The system of  claim 15 , wherein the first and second angles of the first duct portion extend directly to the first and second curved walls. 
     
     
         17 . The system of  claim 15 , wherein the first angle is less than or equal to approximately 8 degrees, the second angle is greater than or equal to approximately 16 degrees, the first radius of curvature is at least greater than 100 centimeters, and the second radius of curvature is at least greater than 100 centimeters. 
     
     
         18 . A method, comprising:
 axially-radially diffusing an exhaust flow from a turbine through a curved duct along a curved flow path without any turning vanes, wherein the curved flow path has a radius of at least greater than or equal to 2 times a cross-sectional width of the curved duct.   
     
     
         19 . The method of  claim 18 , wherein axially-radially diffusing the exhaust flow comprises expanding the exhaust flow between first and second curved walls that curve along the curved flow path, wherein the first curved wall is oriented nearer to a rotational axis of the turbine than the second curved wall. 
     
     
         20 . The method of  claim 19 , comprising axially diffusing the exhaust flow prior to axially-radially diffusing the exhaust flow, wherein axially diffusing the exhaust flow comprises expanding the exhaust flow between first and second angled walls that are angled relative to an axial flow path, wherein the first angled wall is oriented nearer to the rotational axis than the second angled wall.