GB920886A - Improvements in or relating to gas turbine engines - Google Patents

Abstract

920,886. Gas turbine Jet propulsion plant. ROLLS-ROYCE Ltd. Oct. 26, 1959 [Nov. 24, 1958], No. 37822/58. Class 110 (3). A gas turbine jet propulsion plant comprising a ducted fan encircling the turbine of the engine which includes rotor blades formed as radial extensions of the turbine rotor blades, has means to deliver air to parts of the turbine for cooling those parts and to deliver the air from these parts to parts of the ducted fan which are liable to icing. The rear part of a ducted fan gas turbine jet propulsion engine, Fig. 2, comprises a combustion chamber 11 feeding gases to rotor blades 17 through nozzle guide vanes 18. The blades 17 are attached to a rotor disc 16 carried by a shaft 15 supported by bearing 14 mounted in an inner casing 13. The ducted fan and its driving turbine comprise a hollow shaft 21 supported by a bearing 22 within shaft 15 and by a main thrust bearing 23. The shaft 21 has a flange 21a to which is secured a rotor disc 24 and has secured to its end a second rotor disc 25. The discs 24, 25 are spaced apart by a sleeve 26. The disc 24 carries a ring of blades, each of which comprises a root 27a, a turbine blade portion 27b, a connector piece 27c and fan rotor blade portion 27d. The disc 25 carries a ring of similar blades. The blades also have flanges 27e, 28e forming parts of the walls of the working fluid ducts of the turbine and ducted fan. Atmospheric air is supplied through the space 42a to ports 52 leading to manifold 53. The manifold 53 discharges through ports 54 into the annular space between the flanges 27e, then through the ports 74 in the box-like structures 64 and the space between the flanges 28e to the space 71 from which it flows outwardly through the outlet guide vanes 33 to manifold 67 which discharges to atmosphere through ports 75. This air is used to seal the ducted fan air passage from the turbine hot gas passage. To assist the air flow the connector pieces 27c, 28c may be formed as impeller elements. Cooling air, e.g. low pressure air tapped from the compressor of the engine, is fed rearwards through the shaft 15 into shaft 21. This air then passes through ports 76 into spaces 77 to cool the bearing 23 and from spaces 77 into annular space 79 from which it passes outwardly through passages 39 in the vanes 36 to cool them. The heated air flows through manifold 46 and tubes 48 into the ducted fan stator vanes 31 so heating them. The air leaving the vanes 31 passes through chambers 65, 66 and is exhausted to atmosphere through ports 70. The arrangement shown in Fig. 2 also embodies the invention of Specification 920,887 in which sealing air at high pressure is fed to manifold 51 from which it flows through ports 50 to passages 40 in the stator vanes 36. The passages 40 are connected by elbows 55 to a space 56 between a pair of labyrinth seals 57. Part of this air leaks past the outer seal 57 to prevent radial inward flow of hot gases from the working gas passage. Another part of the air from space 56 flows through axial tubes 80 into space 81 and leaks from space 81 through labyrinth seal 82 to seal the inner ends of the turbine blade portions 27b and through seal 83, holes 84, space 85 and radial channels 86 into space 87. From space 87 the air flows through holes 88 to provide sealing air for the inner ends of the interstage guide vanes 37. High pressure air from space 81 passes also into spaces 81a formed between the blade root portions 27a and then flows through radial passages 27f to cool the turbine blades 27b from which it passes into passage 27h to heat the ducted fan rotor blades 27d. In a modification, Fig. 3 (not shown), the cooling air is passed in parallel through two sets of turbine guide vanes to cool them. The guide vanes are connected to a discharge manifold by bobbins connected to the vanes and the manifold. A modified high pressure air sealing arrangement is also described.