GB827477A - Fuel control system for a gas turbine engine - Google Patents

Abstract

827,477. Automatic temperature control systems. UNITED AIRCRAFT CORPORATION. June 19, 1956 [June 21, 1955], No. 18927/56. Class 38 (4). In a system wherein the flow of fuel from a jet 20 into a combustion chamber 18 of a turbine engine is controlled in accordance with the temperature in a tailpipe by a thermocouple 22, the amplifier 26, into which a signal depending on the difference between the thermocouple output and a reference voltage 24 is fed, incorporates a dual feedback circuit comprising resistors 48 and 50 in parallel with a rectifier 56 and a low resistance 52 whereby the amount of feedback when the temperature signal is on one side of the predetermined datum varies from that on the other and the system sensitivity is in consequence similarly varied. This arrangement in conjunction with anticipation condenser 58, prevents overshooting during starting and produces a characteristic as shown in Fig. 5. The dotted curve 66 indicates the effect of the condenser. A solenoid switch 34 is actuated by a generator 32 coupled to the turbine shaft at 60% of the desired speed. Condenser 54 assists condenser 58 during starting but allows 58 to be of smaller capacity and thus reduces hunting during normal running. In a modification described with reference to Fig. 3 (not shown) a connection to earth through a rectifier bleeds the unwanted feedback signal on one side of the datum. Specification 827,476 is referred to.