Patent GB-759033-A (GB)
Title: Improvements in or relating to gas turbine engines
Inventor: FLETCHER ARTHUR HOLMES
IPC: F02C3/36
Filed: 1953-08-19
Abstract: 759,033. Gas turbine plant. ROLLS-ROYCE, Ltd. Oct. 26, 1954 [Aug. 19, 1953], No. 22924/53. Class 110(3) [Also in Group XXXIV] In a gas turbine plant comprising a low pressure compressor driven by a low pressure turbine feeding a high pressure compressor driven by a high pressure turbine and a useful power turbine, the power turbine is arranged between the high and low pressure turbines, the high and low pressure compressors are arranged on the sides of their respective turbines remote from the power turbine and the output shaft extends from the power turbine through the low pressure turbine and compressor and is positioned coaxially within a hollow shaft connecting this turbine and compressor. The low pressure compressor 10, Fig. 2A, is driven by a two stage low pressure turbine 16, through a shaft 38 an internally toothed muff coupling 43 and stub shaft 20. The low pressure compressor supplies air through an intercooler, if desired, to the inlet 90, Fig. 2B, of the high pressure compressor 11 which is driven by a, two stage high pressure turbine 14 through a shaft 67 and splined coupling 69. The high pressure compressor discharges through an exhaust gas heat exchanger to the combustion chambers which supply combustion products to the turbine entry volute 75. After passing through the high pressure turbine 14, the gases enter the three-stage power turbine 15 mounted on a shaft 56 supported by bearings 57, 58 carried in a housing 59. The housing 59 is supported by radial spokes 60 from a main cylindrical outer casing 61 surrounding the high pressure and power turbines. The exhaust gases from the power turbine 15 pass to the low pressure turbine through ducting 62 which changes from a fully annular section to a number of annularly arranged ducts to pass between the spokes 60. The power output shaft 56 is connected by a splined coupling 44a, 56a with a shaft 44 which is supported by a bearing 45 in the low pressure turbine shaft 38. The shaft 44 is connected to another shaft 34, supported by a thrust bearing 35 in the low pressure compressor casing and a bearing 36 in the stub shaft 20 of the low pressure compressor rotor, by an internally toothed muff coupling 46. Rotors. The low pressure compressor rotor consists of a number of annular discs 17, one for each stage carrying blades 18 at their peripheries. At the ends of the rotor are hollow frusto-conical stubshafts 19, 20 having radial flanges 19a, 20a, at their wider ends and cylindrical parts 19b, 20b at their narrower ends. The parts 19b, 20b are supported by bearings 25, 30 mounted in the compressor casing. The rotor is held together by bolts 21. The stubshaft 19 is made in two parts secured together by flanges 19d and a sleeve 22, inserted in the central apertures of the discs 17, is carried by inwardly directed flanges 19c, 20c within the stubshafts. The high pressure compressor rotor is of similar construction. The low pressure turbine rotor comprises two discs 37 having apertures at their centres and interengaging dogs 37a on their abutting faces. The discs 37 are secured on the shaft 38 by a shoulder 38a and a nut 39. The high pressure and power turbines are of similar construction but differ in the manner of attachment to their shafts. Casings. The low pressure compressor casing consists of an inlet casing 23 connected to an outlet volute casing 27 by a diametrically, split casing 31 carrying the stator blades. The high pressure compressor'casing is of similar construction. The high pressure turbine casing comprises an axially extending frusto-conical portion 70 surrounding the high pressure turbine shaft 67 and a diaphragm 71 which extends outwards from the bearing 68. The diaphragm 71 engages at its periphery the high pressure turbine stator vanes 72 to prevent leakage around the vanes. A two part casing 73, 74, which surrounds the turbine entry volute 75, is secured to the portion 70. A. cylindrical casing 76 connected to the high pressure compressor outlet casing 77 is also secured to the portion 70. The stator vanes 72, 81 and shrouds 80 are carried by a diaphragm 78 bolted to the casing 73 and main cylindrical casing 61. The shroud 80 has a spigot engagement with the upstream end of the power turbine nozzle guide vane ring 63. The inlet volute 75 is of double skinned construction and the space between the skins is filled with air drawn from the space around the flame tube assembly. The space between the outer skin 83 and the two part casing 73, 74 is filled with air at the same pressure taken from the compressor delivery. The nozzle guide vanes 63 and shroud rings 64 of the power turbine 15 are supported by a flange 65 of the casing 61. The low pressure turbine guide vanes 54 are supported from a manifold 48b through which cooling air is drawn through hollow struts 48d, and the space around the bearing housing 50. Bearings. The bearing housing 50 is bolted to a flange 49 and supports the thrust bearing 40 and journal bearing 41 of the low pressure turbine shaft. The housing is maintained centrally within the exhaust casing 48 at the end adjacent the bearing 41 by interengaging dogs 51, to allow for axial and radial expansion of the housing. The whole plant consists of two units, one unit consisting of the low pressure compressor and the other of the turbines and high pressure compressor.