GB1247218A - Improvements in fuel supply systems for aircraft engines - Google Patents

Abstract

1,247,218. Gas turbine engine fuel systems. H. M. HOBSON Ltd. Feb.13, 1970 [Jan.16, 1969], No.2656/69. Heading F1G. An aircraft engine fuel supply system comprises a pump, a metering valve and a fluidic vortex valve traversed by fuel and controlling the pressure drop across the metering valve. In the system shown in Fig.4, a centrifugal pump 100 supplies fuel through a metering valve 11. A fraction of the pressure drop across the metering valve 11 is tapped off by a fluid potentiometer comprising a fixed restrictor 27 and a needle valve 25 (the positions of which could be reversed) and applied to a diaphragm 13 in opposition to a spring 14 to control the flow through a nozzle 22 and hence the pressure drop across a restrictor 20 so as to vary the flow through the control port 29 of a vortex valve 28 and hence the main flow through the vortex valve. This in turn controls the pressure drop across a restrictor 30 and hence the flow through the control port 18 of a vortex valve 23 which controls the flow through the metering valve 11. The effect of this arrangement is to maintain the pressure drop across the metering valve 11 at a value determined by the needle valve 25. The vortex valve 28 may be omitted, the vortex valve 23 then being controlled directly by the nozzle 22 and the diaphragm 13 being subjected to the entire pressure drop across the metering valve 11. The spring 14 may be replaced by a centrifugal governor so that the pressure drop across the metering valve 11 is proportional to the engine speed. For a given position of the metering valve 11 the fuel flow to the engine is then proportional to the engine speed. As shown in Fig. 5, the vortex valve 23 may control the flow through a by-pass line 21, and the centrifugal pump may then be replaced by a positive-displacement pump 10. Fig. 5 also shows a modification in which the diaphragm 13 and nozzle 22 act to maintain the pressure drop across a fixed restrictor 31 equal to that across the metering valve 11, thereby controlling the pressure drop across a needle valve 40 arranged downstream of the restrictor. This latter pressure drop is applied to a diaphragm 50 in opposition to a spring 60 to control the flow through a nozzle 70 and hence the pressure drop through the fixed restrictor 20. As before, this controls the flow through the vortex valve 23. The resultant flow through the by-pass line 21 controls the pressure drop across the metering valve 11 in accordance with the function introduced by the needle valve 40. A function of some other variable may be introduced as a mechanical force acting on the diaphragm 50 in place of the spring 60.