GB838323A - Improvements in automatic control systems - Google Patents

Abstract

838,323. Automatic control systems for jet engines. SMITH & SONS (ENGLAND) Ltd., S. Oct. 27, 1958 [Oct. 25, 1957], No. 33449/57. Class 38 (4). An automatic control system for controlling the operation of a jet tur. bine is so arranged that it is stable for small or large discrepancies between actual and demanded operational conditions of the turbine. A jet turbine 1 is normally controlled by a throttle 2 attached to a fuel supply system 3, the fuel system 3 having an over-riding control in the form of a solenoid controlled valve in accordance with an electric signal in a line 4. Thermocouples in the jet pipe of the turbine 1 develop a signal representing the actual operating value of the turbine exhaust temperature which signal is fed into a comparator 7 by way of an amplifier 5. A further signal is generated in a function generator 8 from signals 9, 10, 11 representing turbine speed and intake temperature and pressure respectively, the generated signal representing the demanded exhaust temperature, which signal is fed into the comparator 7 in opposition to the " actual value " signal such that any signal appearing at the output of the comparator 7 represents a discrepancy between the actual and demanded operation conditions of the turbine 1. The discrepancy signal is fed to a second comparator 14 by way of two parallel circuits the first of which is a T-network comprising components 16-19 which transmits the discrepancy signal whatever its value but with a phase lag, the second of which circuits comprises components 21-23 and a by-pass diode 28 which circuit transmits the discrepancy signal only when it exceeds a predetermined value but which is then transmitted with a phase advance. The output of the comparator 14 is fed to a phase shift circuit 33, the output of which constitutes the signal 4 controlling the solenoid in the fuel supply system 3 whereby the turbine is controlled according to the demanded conditions.