GB626045A - Improvements in or relating to automatic controls for internal-combustion gas turbines - Google Patents

Abstract

626,045. Automatic control systems for gas turbines. JAMISON, R. R., and REYNOLDS, D. July 10, 1945, No. 17635. [Class 38 (iv)] [Also in Group XXVI] Speed ; temperature ; flow control.-In an internal-combustion gas turbine, the temperature of the working fluid is regulated by a temperature-responsive device, an electrical property of which varies with temperature from a value corresponding to a datum temperature, such variations, transmitting a signal to an electronic amplifier, the output of which operates means for adjusting the supply of fuel to the turbine in order to restore the temperature of the working fluid to the datum value. In Fig. 1, fuel is supplied through a pipe 14 to a pump 16 driven by the engine and is impelled to a fuel injection device 12 through a valve 19 manually controlled by a throttle lever 20. A pump byepass pipe 21 has a control valve 22, operated by an induction motor 23 supplied with A.C. from an electronic amplifier shown diagrammatically at 25 by which the input of fuel to the engine is regulated. A thermocouple 26 in the exhaust pipe 11 generates a D.C. voltage which is balanced against a steady D.C. voltage derived from a potentiometer 29, the position of the slider of which determines its magnitude. Any out-out-of-balance voltage is applied to a magnetically polarized vibratory 2-way switch which supplies alternate and opposed half-cycles to the dual input of a transformer, the output of which is amplified and applied to one winding of the induction motor, the other winding of which is. energized by an A.C. supply which also operates the vibratory switch. The phase relationship between the vibrator output and the A.C. supply depends on the thermo-couple voltage being above or below the datum voltage set by the potentiometer, and determines the direction of rotation of the induction motor which operates the byepass valve in such a way as to restore the working fluid temperature to the datum value, which is variable according to the setting of the potentiometer ganged to the hand throttle. Between throttle positions 1 and 2 the switch arm 35 is in contact with 37, and the datum temperature is the maximum, consequently no automatic control is exerted. Between positions 2 and 3 the switch arm is in contact with 35, and the potentiometer slider sweeps an extended contact 34, so that the datum temperature is fixed at a low value. As the throttle opens from position 3 to position 4, and from 4 to 5 (maximum setting) the potentiometer delivers a steadily increasing voltage, and the datum temperature rises steadily to its maximum value. Control may be applied to an exhaust jet re-heating device, to the injection of coolant, to the adjustment of the jet nozzle area, to variable pitch airscrews or turbine blades, or to the proportion of working fluid delivered to the various working components such as a power turbine and a heat interchanger. Alternative control valve sys. tems may be used, or separate controls may be provided for throttle and engine temperature. A bridge-type resistance thermometer supplied with A.C. or D.C. may be used as the temperature responsive device instead of a thermocouple. The Provisional Specification refers to the intervalue control of variables other than temperature.