GB810804A - Improvements in or relating to fuel systems of gas turbine engines - Google Patents

Abstract

810,804. Gas turbine plant. ROLLS-ROYCE Ltd. July 13, 1956 [July 15, 1955], No. 20623/55. Class 110 (3). [Also in Group XXIX] The governed maximum speed of a gas-turbine engine is increased when the sensed airintake temperature is above a pre-selected value. The fuel for a gas-turbine passes from a tank 50 and booster pump 51 through a variable capacity swashplate pump 53 and fuel control device 73 to the combustion equipment 20c of the turbine. The pump 53 acts as an enginespeed governor by virtue of centrifugal pressure, generated in passages 68 in the pump rotor, transmitted to one side of a diaphragm 13 balanced against pump inlet pressure; the diaphragm controlling a valve 11 modifying pressure on a piston 60 controlling the angle of the swashplate in known manner. The diaphragm 13 is also controlled by a spring 16 connected to a differential area piston 17, the smaller area of which is subjected to pump delivery pressure through a duct 31. Delivery pressure is also fed to a chamber 29, open to the larger area of the piston 17, through restrictions 27 and 30, a bleed valve 25 being situated between the restrictions. The valve 25 is controlled by a spring 24 and a Bourdon tube 21a sensitive to air temperature at the compressor intake 20a of the engine. In operation at low altitude the engine speed is governed by a pre-selected maximum by the pressure difference on the diaphragm 13 together with the force exerted by the spring 16; the valve 25 being open under the influence of the Bourdon tube 21a and causing a lower pressure to exist in the chamber 29, such that the piston 17 is against a stop 32. As altitude increases and the intake temperature drops, the Bourdon tube contracts to close the valve 25 and equate the pressures on the two sides of the piston 17. The piston 17 moves to the left and relieves the diaphragm 13 of the load of the spring 16, thus lowering the maximum governed engine speed. The values of the engine speeds and intake temperatures are such that the value of N/T, where N is the engine speed and T the intake temperature, at which the engine tends to surge is not exceeded.