GB1133591A - Improvements in fluid controls particularly for turbine engines - Google Patents

Abstract

1,133,591. Fluid-pressure servomotor system; fluid analogue system. GENERAL ELECTRIC CO. April 4, 1966 [May 19, 1965], No.14789/66. Headings G3H and G3P. A fluid control system for a gas turbine engine comprises a fluid generator 40 producing a fluidpressure frequency proportional to the speed by rotating an inclined plate 44 to control the leakage from pipes 34, 36 which are supplied from an inlet 26 through equal restrictors 30. The frequencies produced in the pipes 34, 36, which are 180 degrees out of phase, act as control signals to a fluid amplifier having outlets 52, 54. The outlet 54 is connected to a resonance chamber 60, the volume of which is adjustable by an operator to set the required engine speed. When input frequency is the same as the resonance frequency the output 64 is at maximum strength with no phase shift; if the input frequency varies from the resonance frequency, the output signal is sharply attenuated and lags or leads depending on an increase or decrease in the frequency. The output from the chamber 60 is fed to a decoupler 14 which eliminates any steady state or slowly fluctuating pressures by causing the output of the chamber 60 to split into control signal passages 74, 84 of an amplifier 16. The input 72 to the decoupler is passed through passage 74 and into a large chamber 82 to the passage 84. The chamber 82 will attenuate the pressure frequency so that there will be no pressure variations in the control passage 84 due to the frequency. The outputs of amplifier 16 are used as control signals for a further amplifier 18 which contains chambers 108, 110 to provide a change in the phase of the signals such that the output signals from amplifier 18 are normally 90 degrees out of phase with the output signals in outlet 52 of generator 40. The outputs 122, 124 of the amplifier 18 form control signals 136, 142 of amplifiers 123, 125 of a discriminator 20, the other control signals 140, 138 being connected to the output 52 of the generator 40. When the frequency varies from the frequency of the resonance chamber 60, the net effective force due to the control pressures 136, 138 and 140, 142 causes a difference in pressure between the receivers 133, 135 and thus produce an error signal in a transducer 25 controlling the fuel valve. When it is required to vary the speed with the inlet temperature at the turbine, air is drawn off and passed through the resonance chamber 60.