GB887679A - Improved electrical fuel control system for gas turbine engines - Google Patents

Abstract

887,679. Automatic fuel control systems. DE HAVILLAND AIRCRAFT CO. June 17, 1960 [July 24, 1959], No. 25423/59. Class 38 (4). In an automatic fuel-control system for a gas turbine 1, Fig. 1, having a compressor 2, combustion chamber 3, turbine 4 and a jet-pipe 5, a wash-plate of a fuel pump 6, driven at compressor speed and delivering fuel to burners in the combustion chamber, is positioned by an electro-hydraulic servomotor 7 controlled through a magnetic amplifier. The compressor drives a tacho-generator 9 supplying a signal to a speed error senser 10 whose setting is adjusted by a selection lever 11. A speed error signal is fed from the senser to a governor 12, which is also responsive to jet pipe temperature, intake pressure and temperature. A signal from the governor is fed to a control winding of the magnetic amplifier to position the swash-plate so as to maintain speed constant. The relationship between the swash-plate angle, the ordinate in Fig. 5, and compressor speed, the abscissae is such that for a given ambient pressure and forward speed, at low compressor speeds a particular swash-plate angle may correspond to two compressor speeds. In order that the swash-plate angle can be controlled by a governing signal which increases with increase of engine speed, a second control winding on the magnetic amplifier is fed with a signal, from a circuit 29, which falls with increase in engine speed, as represented by line L. The circuit 29 comprises a resistance network whereby the signal from the tachogenerator 9 is opposed by a fixed reference voltage. A rectifier prevents the occurrence of a reverse potential when the tachogenerator voltage exceeds the reference voltage.