Gas turbine outer case active ambient cooling including air exhaust into a sub-ambient region of exhaust flow

Abstract

A gas turbine engine including an outer case extending circumferentially around the central longitudinal axis. A cooling channel is associated with the outer surface of the outer case, the cooling channel having a channel inlet and a channel outlet. An air duct is provided including an inlet end in fluid communication with the channel outlet and an outlet end in fluid communication with an exhaust gas flow from a turbine section of the gas turbine engine. An exit structure is located at the air duct outlet end, and the exit structure provides a sub-ambient pressure at the air duct outlet end to induce a flow from the air duct inlet end to the air duct outlet end.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 an outer case defining a central longitudinal axis, and an outer surface of said outer case extending circumferentially around the central longitudinal axis;   a cooling channel associated with said outer surface of said outer case, said cooling channel having a channel inlet and a channel outlet;   an air duct including an inlet end in fluid communication with the channel outlet and an outlet end in fluid communication with an exhaust gas flow from a turbine section of said gas turbine engine; and   an exit structure at said air duct outlet end, said exit structure providing a sub-ambient pressure at said air duct outlet end to induce a flow from said air duct inlet end to said air duct outlet end.   
     
     
         2 . The gas turbine engine of  claim 1 , wherein said exit structure interacts with a portion of said exhaust gas flow passing over said exit structure for effecting a reduced pressure at said outlet end to draw air from said cooling channel into said air duct. 
     
     
         3 . The gas turbine engine of  claim 2 , wherein said exit structure partially covers said air duct outlet end, shielding an upstream side of said outlet end and defining a downstream facing opening adjacent a downstream side of said outlet end. 
     
     
         4 . The gas turbine engine of  claim 1 , wherein said exit structure produces a jet pump effect at said air duct outlet end to produce a sub-ambient pressure within said air duct and draw heated cooling air from said cooling channel into said air duct. 
     
     
         5 . The gas turbine engine of  claim 1 , wherein said outer case surface comprises an exterior surface of said outer case, and said cooling channel is defined by a panel structure located radially outward from said exterior surface. 
     
     
         6 . The gas turbine engine of  claim 5 , wherein said cooling channel extends around the circumference of said outer case. 
     
     
         7 . The gas turbine engine of  claim 6 , wherein said channel inlet is at a first circumferential location, and said channel outlet is at a second circumferential location circumferentially spaced from said first circumferential location. 
     
     
         8 . The gas turbine engine of  claim 7 , wherein said first circumferential location of said channel inlet is diametrically opposite from said second circumferential location of said channel outlet. 
     
     
         9 . The gas turbine engine of  claim 1 , wherein said cooling channel is located at an axial location of an exhaust diffuser, and said air duct outlet is located downstream from said exhaust diffuser at an exhaust manifold. 
     
     
         10 . The gas turbine engine of  claim 1 , wherein said air duct inlet end is open to ambient air outside of said gas turbine engine to provide ambient cooling air to said cooling channel. 
     
     
         11 . A gas turbine engine comprising:
 an outer case defining a central longitudinal axis, and an outer surface of said outer case extending circumferentially around the central longitudinal axis;   an exhaust gas passage defined within said outer case for conducting an exhaust gas flow from a turbine section of said gas turbine engine;   a cooling channel extending circumferentially around said outer surface of outer case, said cooling channel having a channel inlet and a channel outlet located in circumferentially spaced relation to said channel inlet;   an air duct including an inlet end in fluid communication with the channel outlet and an outlet end in fluid communication with the exhaust gas flow; and   an exit structure at said air duct outlet end interacting with said exhaust gas flow for effecting a reduced pressure at said outlet end of said air duct to draw air from said cooling channel into said air duct.   
     
     
         12 . The gas turbine engine of  claim 11 , wherein said cooling channel is located at an axial location of an exhaust diffuser, and said air duct outlet is located downstream from said exhaust diffuser at an exhaust manifold. 
     
     
         13 . The gas turbine engine of  claim 12 , wherein said air duct is located outside of said outer surface of said outer case and extends axially between said exhaust diffuser and said exhaust manifold. 
     
     
         14 . The gas turbine engine of  claim 12 , wherein said exhaust manifold includes a manifold wall having a manifold outer surface and a manifold inner surface, a manifold opening extending between said manifold outer and inner surfaces, said air duct is attached to said manifold outer surface and said exit structure is mounted to said manifold inner surface. 
     
     
         15 . The gas turbine engine of  claim 14 , wherein said exit structure is defined by a plate-like exit shield plate having a first circumferential edge attached to the said manifold inner surface upstream of said manifold opening, and said exit shield having a second circumferential edge downstream of said first circumferential edge and spaced radially inwardly from said manifold inner surface. 
     
     
         16 . The gas turbine engine of  claim 15 , wherein said air duct defines a central axis extending generally parallel to flow of air through said air duct and said central axis intersects said exit shield. 
     
     
         17 . The gas turbine engine of  claim 15 , wherein said exit shield diverts flow of exhaust gas in said exhaust manifold away from said manifold opening and effects said reduced pressure at said outlet end of said air duct. 
     
     
         18 . The gas turbine engine of  claim 11 , including a thermal barrier/cooling system for controlling a temperature of the outer case, said thermal barrier/cooling system including:
 an internal insulating layer supported on an inner surface of said outer case opposite said outer surface of said outer case, the internal insulating layer extending circumferentially along said inner surface of said outer case and providing a thermal resistance to radiated energy from said exhaust gas passage located radially inwardly from said outer case; and   said cooling channel defined by a panel structure located in radially spaced relation to said outer surface of said outer case and extending around the circumference of said outer surface of said outer case, said cooling channel being generally axially aligned with said internal insulating layer and forming a flow path for an ambient air flow cooling said outer surface of said outer case.   
     
     
         19 . The gas turbine engine of  claim 18 , including an external insulating layer supported on and covering said panel structure.