GB756976A - Improvements in or relating to lubricating systems for gas-turbine engines - Google Patents

Abstract

756,976. Lubricating systems. ROLLS-ROYCE, Ltd. Dec. 31, 1954 [Feb. 18, 1954], No. 4863/54. Class 12 (3). A lubricating system for a gas turbine engine, of the type in which the lubricating oil after use is not returned to the source of supply, comprises a source of oil under pressure, conduit means to convey the oil from the source to be distributed, a sharp-edged restrictor in the conduit, and heating means in part at least surrounding the conduit immediately upstream of the restrictor to heat the oil at least to a predetermined temperature above which the change in viscosity of the oil on change of temperature is small, whereby the change in the rate of flow of oil for a given pressure difference across the restrictor is maintained within desired narrow limits. As shown, the compressor of a gas turbine engine has a housing 15 in which is mounted a casing 18 which accommodates a centrifugal pump including an impeller 19. The impeller is driven through a shaft 28 which has an enlarged head 28a splined to engage parts of an oil distributer tube 29 rotatable with the compressor shaft 13b. The impeller has an inlet duct 20 extending from a fuel booster pump 21 and a delivery duct 22 leading to a throttle on the casing 18 and thence to a delivery duct 23 leading to fuel injectors in the engine combustion equipment. The booster pump 21 draws fuel from a tank 24 and is driven by a hydraulic motor 25 which is operated by fuel taken from the delivery of the pump 19 through a spill duct 26. The fuel in this duct heats lubricating oil as it flows from an oil reservoir 30 through a line 31 to the distributer tube 29. The line contains a restrictor 33 of the sharp-edged type. The oil in the reservoir 30 is kept under pressure by compressed air leading from the compressor through a pipe 34 and passing through a sharp-edged restrictor 35. A relief valve 36 is fitted in a branch 34a from the pipe 34 to maintain the pressure substantially constant in the oil tank 30. In a modification the oil is heated by compressed air instead of fuel. Specifications 735,874, [Group XXVI], and 745,213 is referred to.