Exhaust Gas Diffuser Wall Contouring

Abstract

A diffuser for diffusing the exhaust gas produced by an engine is provided. The diffuser includes a wall or walls defining sections of the diffuser, the diffuser including a first section and a second section following the first section, wherein the rate of increase of the cross-sectional area of the diffuser, which includes using an outer annular wall as an outer boundary and the inner annular wall as an inner boundary, in a direction of fluid flow is greater in the first section than it is in the second section. An upstream end of the inner annular wall or an upstream end of the outer annular is bent.

1 . A diffuser for diffusing an exhaust gas produced by a gas turbine engine, comprising:
 an inner annular wall defining sections of the diffuser, where the sections comprise a first section and a second section following the first section, a first upstream end of the inner annular wall is bent or a second upstream end of the outer annular wall is bent, wherein the rate of increase of a cross sectional area of the diffuser, which includes using an outer annular wall as an outer boundary and the inner annular wall as an inner boundary, in a direction of fluid flow is greater in the first section than it is in the second section, and   the outer annular wall coaxially aligned and surrounding the annular inner wall,   wherein the inner annular wall diverges away from an axis of the gas turbine engine, and   wherein the diffuser diffuses the exhaust gas produced by the gas turbine engine.   
     
     
         2 . The diffuser according to  claim 1 , wherein the inner annular wall is conical and the outer annular wall is concave curving toward the inner annular wall. 
     
     
         3 . The diffuser according to  claim 2 , wherein at the entry to the first section of the diffuser the ratio of the radius of the outer annular wall to the radius of the inner annular wall is between 1.4 to 1.8. 
     
     
         4 . The diffuser according to  claim 3 , wherein the diffuser L/H ratio is between 7 to 12, where L is the total length of the diffuser along the axis of the inner and outer annular walls, and H is the distance between the inner and outer annular walls at entry to the diffuser in a direction perpendicular to the axis. 
     
     
         5 . The diffuser according to  claim 4 , wherein the angle between the conical inner annular wall and the axis of the inner and outer annular walls is between 5 to 15 degrees. 
     
     
         6 . The diffuser according to  claim 5 , wherein the ratio of the cross-sectional area of the diffuser at entry to the diffuser to the cross-sectional area of the diffuser at exit from the diffuser is less than 3.5. 
     
     
         7 . The diffuser according to  claim 1 , wherein the outer annular wall is conical and the inner annular wall is generally concave and curves toward the outer annular wall.