GB980088A - Improvements in or relating to fuel control in internal-combustion turbine engines - Google Patents

Abstract

980,088. Gas turbine plant. PLESSEY CO. Ltd. June 8, 1961 [June 10, 1960], No. 20427/60. Heading FIG. A fuel control device for gas turbine engines comprises a spool valve axially displaceable within a ported sleeve, means being provided for continuously rotating the sleeve, further means being provided-responsive to at least one operating condition of the engine to cause axial movement of the sleeve upon a predetermined operating condition being reached so as to increase the flow resistance through the valve. In Fig. 1, the fuel metering unit 14 comprises a spool valve, 16 disposed within a sleeve 17 having metering ports 18, the sleeve being disposed within a bore in the valve body 15. A chamber at the upper portion of the valve body is divided into two compartments 24, 25 by means of a diaphragm 26 which is secured to the spool 16, the compartment 24 being connected to compressor delivery pressure through restricted orifice 30 and the compartment 25 being connected to atmosphere through port 28. An orifice interconnecting the compartments 24, 25 is normally closed by a spring-loaded half-ball valve 31, the stem of which slides within a sleeve 33, the axial position of which is set by means of a control lever 36. A head 34 on the stem of the valve 31 can engage the sleeve 33 whereby at certain conditions, the spool valve 16 can move away from the valve 31 so connecting the compartment 24 to compartment 25 and so to atmosphere. The spool valve is loaded upwardly by spring 27 so as to restrict the metering orifice 18. The sleeve 17 is rotated continuously during operation by means of gearing 21 at a speed proportional to engine speed, and the sleeve carries at its lower end a governor device 38 which in operation tends to move the sleeve 17 downwardly against the loading of spring 39. Fuel is supplied to the metering device by means of an engine driven pump 10 and after passing through the metering orifices 18 passes to a burner device 20, a shut off valve 19 being disposed downstream of the metering orifices. The pressure drop across the metering orifices is maintained constant by means of a diaphragm 22 and valve 23, the fuel at pump pressure being connected to the upper side of the diaphragm 22 so as to tend to open the valve 23 which would allow fuel to pass back to the pump inlet, while metered fuel pressure downstream of the orifices 18 is connected to the lower side of the diaphragm 22 and tends to close the valve 23. If the compressor delivery pressure should rise above a valve pre-determined by the setting of the control lever 36, the pressure in the compartment 24 will cause the diaphragm 26 to move the valve seat away from valve 31 and so pressure in the compartment 24 will be vented through compartment 25 to atmosphere and the spool valve 16 will move upwardly under the action of spring 27 to restrict the metering orifices 18.