Patent GB-1293811-A (GB)
Title: Improvements in gas turbine engine lubricant sump vent and circulating system
IPC: F02C7/06
Filed: 1970-02-18
Abstract: 1293811 Gas turbine engines - bearings and lubrication GENERAL ELECTRIC CO 18 Feb 1970 [24 Feb 1969] 7776/70 Heading F1G The invention relates to a gas turbine engine bearing and lubrication system in which means are provided to pressurize the bearing chambers to prevent loss of lubricant therefrom. The engine shown is a gas turbine ducted fan twoshaft engine comprising LP compressor or fan 18, HP compressor 26, combustion equipment 48, HP turbine 30 and LP turbine 22, also an inner LP shaft 12 and an outer HP shaft 14, the inner shaft comprising an intermediate portion 19 which is in splined connection at 21 with the LP compressor rotor 16 and with the LP turbine rotor 20. The shafts are supported in a system of bearings 50, the forward system of bearings being shown in Fig. 2, the bearings being disposed within chambers 60 to which lubricant is supplied at 68. Seal means are provided at 70, 72 between stationary structure 32 and the inner and outer shafts respectively; seal means 74 are provided between the shafts. The bearing chambers 60 are enclosed within pressurized chambers 86 and 96 to which air is supplied from the LP compressor through openings 88 into the strut members 52 thence through openings 90, 94 to the chambers 86, 96. The air passes through the seals 70, 72 into the bearing chambers 60 and then passes through radial ducts 114 into a central duct 104 which extends within the inner shaft 12 being closed at its upstream and open at its downstream end 112 for discharge of air into the engine exhaust 38. The radial ducts are designed so that lubricating oil does not pass into the central duct but is returned to the bearing chamber. Some air from the pressurized chamber 86 passes through radial ducts 118 to an inner annular passage 108 which extends between the inner shaft 12 and the central duct 104 and through which air is supplied to the pressurized chambers 100, 102 enclosing the downstream bearing chambers 64, 66, Fig. 4, the air entering the pressurized chambers through openings 120, 122. Some air from the pressurized chamber 96, Fig.2 passes through openings 132, 134 to a passage 126 where it passes in part through inter-shaft seal 74 and in part to the intershaft seal 80 to the downstream bearing chamber 64. A further portion of air from the chamber 96 passes through openings 132 to the passage 140 disposed around the passage 126. Air passes from the passage 140 through openings 142 to the pressurized chamber 98 enclosing the intermediate bearing chamber 62 the air passing through the seals 76 into the bearing chamber 62. The air and oil vapour discharges from the bearing chamber 62 through ducting 144 to the bearing chamber 60, Fig.2 discharging with the air and oil vapour in that chamber through the radial ducts 114. The air supplied through the annular passage 108 passes to the pressurized chamber 100, 102 around the downstream bearing chambers 64, 66 through openings 120, 122 all respectively, Fig.4, the air passing through seals 78, 82 and 84 into the bearing chambers 64, 66. The air and oil vapour discharges from the chambers 64, 66 through radial ducts 114 into the central vent duct 104, the oil droplets being passed back to the bearing chambers, as before. Some oil may pass from the central duct 104 through the radial duct 148 in order to lubricate the spline coupling 21, Fig. 2. Oil is removed from the bearing chambers by scavenge pumps not shown.