GB1254612A - An improved fuel control system for a gas turbine engine - Google Patents

Abstract

1,254,612. Gas turbine engine fuel systems. H.M. HOBSON Ltd. April 17, 1970 [Jan.20, 1969], No.3119/69. Heading F1G. A fluidic vortex valve meters the fuel flow to the main burner of a gas turbine engine, a governor controllable by the pilot adjusts the fuel-pressure at the control port of the vortex valve to maintain the required steady-state engine speed, and means for varying the pressure drop across the vortex valve are operable during acceleration and when the main flow through the vortex valve is saturated, so that the fuel flow is limited during acceleration. Fuel is supplied via a centrifugal pump 1, a cooler 2, a positivedisplacement pump 3 and a vortex metering valve 4 to the main burner. The line 31 supplying fuel to the primary burner also supplies fuel to the control port 5 of the vortex valve 4 via a valve 6 actuated by a all-speed governor 7 under the control of the pilot's throttle lever 9, whereby the main flow through the vortex valve 4 is governed to maintain the required engine speed. During acceleration, the main flow through the vortex valve 4 becomes saturated, i.e., it cannot be further increased by any further reduction of the pressure at the control port 5. The vortex valve 4 then behaves as a fixed orifice, the main flow through it being controlled solely by varying the pressure drop across it. Variation of the pressure drop is effected by by-passing some of the output of the pump 3 to its inlet via a vortex valve 17. The by-pass flow through the vortex valve 17 is controlled by varying the pressure at its control port 25 by means of a by-pass valve 23 located downstream of a fixed orifice 24. The valve 23 is controlled in accordance with engine speed by a governor 22 and in accordance with compressor pressure by a diaphragm 21 subjected to the pressure drop across a valve 16. The valve 16 is controlled by a capsule 18 subjected internally to a compressor pressure P 3 and an evacuated capsule 27, both capsules being subjected externally to a pressure P x developed by a potentiometer 19, 20 subjected to the pressure P 3 and a higher compressor pressure P 4 . The valve 16 is located in a by-pass line 11, in series with valves 12 and 13, the valve 13 being controlled by a diaphragm 14 subjected on opposite sides to the pressures downstream of the vortex valve 4 and downstream of the valve 12, whereby these pressures are equalized. The pressure drops across the vortex valve 4 and the valve 12 are thereby equalized, whereby the main flow through the vortex valve is proportioned to the flow through the valves 12, 16 and therefore a function of engine speed and compressor pressure. The valve 12 is opened by an electronic unit, thereby reducing the fuel flow through the vortex valve 4, when the safe operating limit of, e.g. the speed of another engine shaft or turbine inlet pressure is approached. In another embodiment, Fig.3 (not shown), the vortex valve 17 is arranged in series with the vortex valve 4 and acts as a throttle valve instead of a by-pass valve.