GB1095129A - Improvements in gas turbine engines - Google Patents

Abstract

1,095,129. Bearings. BRISTOL SIDDELEY ENGINES Ltd. May 9, 1966 [May 10, 1965], No. 19652/65. Heading F2A. [Also in Division F1] In a gas turbine engine which comprises air compressors in flow series, there being at least one shaft bearing in a chamber between the compressors and at least one mechanical seal which requires to be pressurized by air, at least one zone which requires to receive a flow of coolant air, and bleed-off ducting for conveying air compressed by the high pressure compressor to the seal and to the zone, a heat exchanger is incorporated in the ducting for cooling the air before it reaches the seal and the zone. The invention is described with reference to a gas turbine jet engine designed for operation at Mach 2 in which air tapped from the compressor would be too hot for the pressurizing and cooling purposes. The engine is of the two-spool type comprising low-pressure compressor 35, highpressure compressor 37, combustion equipment 40, high-pressure turbine 39, and low-pressure turbine 34, the H.P. turbine driving the H.P. compressor through shaft 38, and the L.P. turbine driving the L.P. compressor through shaft 36. The L.P. shaft 36 is mounted in a bearing 42 and the H.P. shaft 38 is mounted at its forward end in twin bearings 62, the bearings being supported by stationary structure comprising inner easing 41, vanes 43 and outer casing 20. Air is tapped from between stages 51, 61 of the H.P. compressor and passes through duct 28 to the heat exchanger 22 where it is cooled by flow of boundary layer ram air in duct 15, Fig. 1, not shown. The cooled air then passes through ducting 23 to the space 52 within the inner casing 41, some air then passing to space 54, through passage 55 and bores in the shaft 38 to the space 56 between the two shafts 36, 38 where it serves to cool the shafts which are disposed adjacent the combustion equipment 40. The air finally discharges through seal 50 into the space between the two turbines 39, 34. The seal 50 is provided to prevent the back-flow of turbine gases. The space 56 is defined at its forward end by a tube member 66 adjacent the L.P. shaft 36. Lubricating oil is supplied to the bearings 42, 62 and discharges therefrom through annular scavenge chamber 46. Seals are provided at i, c and f, Fig. 4, to prevent leakage of oil from the bearings, the seals being pressurized by air. Further labyrinth seals are provided at g, h, a, b, e, d. The seals c and f are pressurized by air from the chamber 54 which leaks through the seals b, d, e, the air passing back to the chamber 53 and thence being discharged to atmosphere through duct 69. The seal i is pressurized by air from the chamber 52 which leaks through seal h, this air also passing back to chamber 53 and thence to atmosphere.