GB1442740A - Gas turbine exhaust duct - Google Patents

Abstract

1442740 Jet propulsion nozzles GENERAL MOTORS CORP 10 Dec 1970 58809/70 Heading F1J An exhaust duct structure adapted for cooling to minimize the visible or infrared radiation from the exhaust of a gas turbine engine comprises an annular exhaust passage 21 extending from the turbine 6 to the engine outlet 22 and defined between outer and inner walls 25 and 26, respectively. The outer wall 25 is of a double-walled construction and is fixed to a bolting flange 29 on the engine casing 15. A stiffener ring 30 is bolted to the flange 29 and an outer sheet 31 continues downstream to the engine outlet 22. An inner sheet 33 is made up of a number of overlapping sections 34, 35, 36, 37 and 38 connected to each other by corrugated strips 41 which space the adjacent sections slightly from each other to provide gaps for entrance of film cooling air. An external wall 42 extends from the outer sheet 31 to the stiffener ring 30 and is shaped so as to define between its leading edge and the ring 30 a number of ram air scoop inlets 45 which reeeive air propelled by a ducted fan (not shown) driven by the turbine 6. The air is received in an annular plenum chamber 46 between the external wall 42 and the outer sheet 31. The inner wall or inner body 26 is of bulbous configuration, as a result of which the exhaust passage 21 is blocked from direct sight through it into the turbine 6, and comprises a forward section 49 diverging rearwardly and three converging, overlapping sections 50, 51 and 52 extending to the tip of the inner body. The sections 49, 50, 51 and 52 are connected by corrugated strips 54 in the same manner as the sections of the inner sheet of the outer wall. Sections 49, 50 and 51 include stiffener rings or flanges 55 which prevent direct radiation from the inner surface of the inner body 26 through the film air outlets. The inner body 26 is supported by six radial hollow struts 58 which extend from the external wall 42 through the sheets 31 and 33 of the outer wall 25 to the section 49 of the inner body. The struts open at their inner ends into the body 26 and at their outer ends into the annular plenum chamber 46. Cooling air is thus supplied to the interior of the inner body 26 through the gaps provided by the corrugated strips 54 and also to the space between the sheets 31 and 33 of the outer wall 25 through a number of metering openings 61 in the sheet 31. The size and number of openings 61 is such as to provide the desired division of the air and rate of flow as between the outer and inner walls of the exhaust passage. Each strut 58 comprises a forward U-shaped section 62 and a trailing V-shaped section 63, these being connected by corrugated strips 65 which define outlets 67 for cooling air. The trailing portion 63 which is partially visible from outside the engine is thus bathed in a film of cooling air.