Exhaust diffuser for a gas turbine engine exhaust system

Abstract

An exhaust diffuser for a gas turbine engine includes a diffuser inlet, a diffuser exit, an inner diffuser wall, and an outer diffuser wall. The inner diffuser wall may include a first tubular member with a flared downstream portion. The outer diffuser wall may include a second tubular member at least partially about the inner diffuser wall and with a second flared downstream portion. The outer diffuser wall and the inner diffuser wall extend between the diffuser inlet and the diffuser exit, and form a diffusing flowpath therebetween. The second flared downstream portion may include a lower section and an upper section, with the upper section extending further downstream in an axial direction than the lower section, relative to the diffuser axis.

What is claimed is: 
     
         1 . An exhaust diffuser for a gas turbine engine, the exhaust diffuser comprising:
 a diffuser inlet;   a diffuser exit;   an inner diffuser wall including a first tubular member about a diffuser axis extending between the diffuser inlet and the diffuser exit, the first tubular member including a first flared downstream portion proximate the diffuser exit, and   an outer diffuser wall including a second tubular member about the diffuser axis and at least partially about the inner diffuser wall and extending between the diffuser inlet and the diffuser exit, the outer diffuser wall and the inner diffuser wall forming a diffusing flowpath between the diffuser inlet and the diffuser exit, the second tubular member including a second flared downstream portion, the second flared downstream portion including
 a lower section, and 
 an upper section, the upper section extending further downstream in an axial direction than the lower section, relative to the diffuser axis. 
   
     
     
         2 . The exhaust diffuser of  claim 1 , wherein the an outer diffuser wall further includes
 a uniform section extending downstream from the diffuser inlet, the uniform section including a surface of revolution, the surface of revolution defined by a two-dimensional curve rotated about the diffuser axis, the two-dimensional curve including a linear segment and a curved segment, and   an offset extension extending downstream from the uniform section to the diffuser exit, the offset extension including a truncated surface of revolution terminating in an offset end, the offset end substantially defining a truncation plane ( 549 ), the truncation plane ( 549 ) forming a cutback angle ( 546 ) with a normal plane ( 548 ), the normal plane ( 548 ) normal to the diffuser axis, the cutback angle ( 546 ) between 1 degree and 5 degrees from the normal plane ( 548 ); and   wherein the uniform section and the offset extension together encompass the lower section and the upper section.   
     
     
         3 . The exhaust diffuser of  claim 1 , wherein the first flared downstream portion extends radially outward from the diffuser axis, and includes a surface of revolution about the diffuser axis including a flare with between 75 degrees and 105 degrees of arc, the flare terminating in a substantially normal direction to the diffuser axis at the diffuser exit. 
     
     
         4 . The exhaust diffuser of  claim 1 , further comprising a plurality of diffuser struts circumferentially distributed around the diffuser axis and extending between the outer diffuser wall and the inner diffuser wall. 
     
     
         5 . An exhaust system for a gas turbine engine, the exhaust system comprising the exhaust diffuser of  claim 1 , and further comprising an exhaust collector configured to receive exhaust gas circumferentially from the diffuser exit, the exhaust collector including
 an exhaust collector exit located substantially opposite from the lower section, relative to the diffuser axis,   a forward wall,   an aft wall, and   a circumferential wall extending between the forward wall and the aft wall, the circumferential wall encircling a majority of the diffuser exit.   
     
     
         6 . The exhaust system of  claim 5 , wherein the exhaust collector further includes an exhaust collector turning region opposite the discharge direction; and
 wherein the forward wall is maintained a minimum axial distance from the aft wall, the minimum axial distance being at least double a distance between the inner diffuser wall and the outer diffuser wall at the diffuser exit measured in a plane including the diffuser axis and a point on a maximum cutback of the lower section.   
     
     
         7 . The exhaust diffuser of  claim 5 , further comprising a minimum gap between the diffuser exit at a maximum cutback of the lower section and the circumferential wall, the minimum gap being at least one half a distance between the inner diffuser wall and the outer diffuser wall at the diffuser exit, and as measured in a plane including the diffuser axis and a point on the maximum cutback. 
     
     
         8 . The exhaust system of  claim 5 , wherein the gas turbine engine includes a center axis; and
 wherein the exhaust collector exit is configured to discharge the exhaust gas in a discharge direction radially between positive 135 degrees and negative 135 degrees around the center axis from top dead center, relative to the gas turbine engine.   
     
     
         9 . An exhaust system for a gas turbine engine, the exhaust system comprising:
 an exhaust diffuser including
 a diffuser inlet, 
 a diffuser exit, 
 an inner diffuser wall extending between the diffuser inlet and the diffuser exit, the inner diffuser wall defining a surface of revolution with a first flared downstream portion about a diffuser axis, and 
 an outer diffuser wall extending between the diffuser inlet and the diffuser exit, the outer diffuser wall defining a truncated surface of revolution with a second flared downstream portion about the diffuser axis, the second flared downstream portion obliquely truncated proximate the diffuser exit and relative to a plane normal to the diffuser axis, the second flared downstream portion including a maximum cutback, the inner diffuser wall and the outer diffuser wall forming a diffusing flowpath between the diffuser inlet and the diffuser exit; and 
   an exhaust collector including
 an exhaust collector exit configured to discharge exhaust gas along a discharge direction, the exhaust collector exit located substantially opposite from the maximum cutback, relative to the diffuser axis and along the discharge direction, 
 a forward wall, 
 an aft wall, and 
 a circumferential wall extending between the forward wall and the aft wall, the circumferential wall encircling a majority of the diffuser exit. 
   
     
     
         10 . The exhaust system of  claim 9 , wherein the gas turbine engine includes a center axis; and
 wherein the exhaust collector exit is configured to discharge exhaust gas in a discharge direction radially between positive 90 degrees and negative 90 degrees around the center axis from top dead center, relative to the gas turbine engine.   
     
     
         11 . The exhaust system of  claim 9 , wherein the first flared downstream portion extends radially outward from the diffuser axis, and includes a flared surface of revolution about the diffuser axis including a flare with between 75 degrees and 105 degrees of arc, the flare terminating in a substantially vertical direction at the diffuser exit. 
     
     
         12 . The exhaust system of  claim 9 , wherein the exhaust collector further includes an exhaust collector turning region opposite the discharge direction; and
 wherein the forward wall is maintained a minimum axial distance from the aft wall, the minimum axial distance being at least double a distance between the inner diffuser wall and the outer diffuser wall at the diffuser exit measured in a plane including the diffuser axis and a point on the maximum cutback.   
     
     
         13 . The exhaust system of  claim 9 , further comprising a minimum gap between the diffuser exit at the maximum cutback and the circumferential wall, the minimum gap being at least one half a distance between the inner diffuser wall and the outer diffuser wall at the diffuser exit, and as measured in a plane including the diffuser axis and a point on the maximum cutback. 
     
     
         14 . The exhaust system of  claim 9 , wherein the exhaust collector further includes an exhaust collector turning region opposite the discharge direction; and
 wherein the forward wall is maintained a minimum axial distance from the aft wall, the minimum axial distance being approximately the same as an axial distance between the forward wall and the aft wall opposite the exhaust collector turning region and proximate the diffuser exit.   
     
     
         15 . The exhaust system of  claim 9 , wherein the truncated surface of revolution is at least partially defined by a two-dimensional curve rotated about the diffuser axis, the two-dimensional curve including linear segment at an upstream end and a curved segment at a downstream end, the linear segment aligned with a tangent of the curved segment at an interfacing point. 
     
     
         16 . An exhaust system for a gas turbine engine, the gas turbine engine having a center axis and a turbine, the exhaust system comprising:
 an exhaust diffuser including a diffuser inlet, a diffuser exit, an inner diffuser wall, and an outer diffuser wall, the inner diffuser wall, and the outer diffuser wall extending between the diffuser inlet and the diffuser exit and forming a diffusing flowpath therebetween, the diffuser inlet configured to axially receive exhaust gas from the turbine, the diffuser exit configured to radially discharge the exhaust gas,
 the inner diffuser wall including a first surface of revolution about the center axis, the first surface of revolution including a first conic region and a first flared downstream portion, the first flared downstream portion including a first flare radius, 
 the outer diffuser wall including a second surface of revolution about the center axis, the second surface of revolution including a second conic region and a second flared downstream portion, the second flared downstream portion including a second flare radius and an cutback portion with a maximum cutback located substantially radially opposite from the exhaust collector exit; and 
   an exhaust collector including an exhaust collector exit, a forward wall, a circumferential wall, and an aft wall, the circumferential wall extending between the forward wall and the aft wall, the exhaust collector configured to receive the exhaust gas circumferentially about the center axis from the diffuser exit, the exhaust collector exit configured to discharge the exhaust gas in a discharge direction radially between positive 135 degrees and negative 135 degrees around the center axis from top dead center, the discharge direction substantially radially opposite from the maximum cutback, relative to the center axis.   
     
     
         17 . The exhaust system of  claim 16 , wherein the first flared downstream portion extends radially outward from the center axis, and includes a flared surface of revolution about the center axis including a flare with between 75 degrees and 105 degrees of arc, the flare terminating in a substantially vertical direction at the diffuser exit. 
     
     
         18 . The exhaust system of  claim 16 , wherein the forward wall is substantially vertical. 
     
     
         19 . The exhaust system of  claim 16 , wherein the first flare radius and the second flare radius are concentric; and
 wherein the second flare radius is constant.   
     
     
         20 . The exhaust system of  claim 16 , wherein the discharge direction is radially between positive 5 degrees and negative 5 degrees around the center axis from top dead center.