Patent GB-1171589-A (GB)
Title: Gas Turbine Engines
IPC: F02C7/06
Filed: 1968-10-11
Abstract: 1,171,589. Gas turbine engines. GENERAL MOTORS CORP. Oct.11, 1968 [Dec.6, 1967], No.48230/68. Heading F1G. The invention relates to a gas turbine engine of the kind comprising a first turbine which drives the engine compressor and a second turbine which provides useful power, there being a bearing structure between the two turbines for supporting the two turbine shafts, a transfer member extending from the bearing structure along the axis of one of the turbines to an exterior point, the bearing structure and the transfer member being adapted to provide a heat sink and an escape means for soak-back heat upon engine shut-down. The engine shown comprises a centrifugal compressor 7, combustion equipment 14, a first turbine 33 connected by shaft 38 to drive the compressor, and a second turbine 34 mounted on shaft 45 and driving an external load. The engine comprises a rotary regenerative heat exchanger, not shown, a partition 27 being provided between the highpressure and low-pressure sides of the engine. The compressor-turbine shaft 38 is mounted at its forward end in a bearing 40; a stub shaft 77 is secured to the downstream side of the turbine rotor 33 and the stub shaft is supported in a bearing 63. The power turbine shaft 45 is supported in a bearing 65 at the upstream side of the turbine rotor 34 and in a second bearing 46 at the downstream end of the shaft 45, see Fig. 1b. The gases passing from the compressor-drive turbine 33 to the power turbine 34 pass through annular duct 21 defined by outer wall 19 and inner wall 22. A bearing support structure 57 is disposed between the two turbines 33 and 34 inwardly of the gas flow duct 21 and comprises a main member 58 and two end members 59, 61 which are secured together by through-bolts 62 which also secure a support member 68 which is integral with the outer wall 19 of the gas flow duct, the member 68 being of corrugated section. The shaft bearings 63 for the stub shaft 77 and 65 for the power turbine shaft 45 are supported within the main member 58. The turbine exhaust outlet is indicated at 35 and the gases flow from the outlet through arcuate openings 37 at each side of the casing 11 and then through the regenerator matrices not shown. The bulkhead 27 between the high and low-pressure sides is double-walled 187, 188 to permit flow of ambient air. The housing 11 has a conical portion 51 disposed around the power shaft, a seal means 78, 79 being provided between the conical portion and the shaft. The power turbine shaft 45 is hollow and a fixed transfer member 85 extends therethrough, being secured at its forward end 96 in the bearing housing 58 and its rearward end projecting into the gear casing 49. The transfer member is formed with a number of through-bores 87, 88, 89, 90, 91, as seen in Fig. 2, the bore 88 being for lubricating oil supply to the bearings 63 and 65, bore 91 for the lubricating oil return, and bore 89 for pressure air supply to shaft seals 66 and 67. Cooling oil is supplied through bore 87 and returned through bore 90. Lubricating oil supplied through bore 88 passes through ducts 101, 102, 103, 104 to the bearings 63 and 65, the oil passing from the bearings through bores 109, 111, 110, 112, 113 to the sump 106, the oil then passing through hollow bolt 115 to the return bore 91. Pressure air supplied through bore 89 passes through bores 121, 122, 123 in the bearing structure 58, see Fig.4 and thence through bores 124, 125 in the bearing housing end structures 59, 61 and thence to the shaft seals 66 and 67, Fig. 3, the air discharging from the seals through bores 109, 113 acting to cause the return flow of lubricating oil through bore 91. Bearing cooling oil supplied through bore 87 pores through a radial bore 133 in the bearing structure 58, see Fig.4 thence through axial bore 134 to an annular recess 135 in the end structure 61; the oil then flows through a series of axial bores 137 in the bearing structure 58 to an annular recess 138 in the forward face thereof; the cooling oil then flow through bores 139, 141, 142, Fig.2, to the axial bore 90 in the transfer member 85. The means for supply of pressure air to the bore 88 is indicated at 170, 171 in Fig. 1b. A power transfer shaft 86 extends through the transfer member 85 being secured at its forward end to the stub shaft 77 of the compressor-drive turbine 33 by means of a tapered portion 173. The rearward end of the shaft may be connectible to the power turbine shaft 45. A gear pinion 53, is formed on the shaft 45 and drives through gears 54 a ring gear 55, the ring gear having a pinion 56 secured to it by which further reduction gearing is driven. The shaft 86 is connected to drive the rotary regnerator matrices through sprocket and chain drive 157, 158, 159, Fig. 1a. The bearing structure 58, 59, 61 is covered with thermal insulation material.