GB852290A - Engine liquid fuel supply system - Google Patents

Abstract

852,290. Gas turbine engines. ROLLSROYCE Ltd. Jan. 28, 1958 [Jan. 28, 1957], No. 3043/57. Class 110 (3). A fuel system for a continuous combustion gas turbine engine comprises primary and secondary fuel injectors, a main pump with control means metering the total fuel delivery to the injectors, through a main fuel line, branch fuel lines leading from the main fuel line to the primary and secondary fuel injectors respectively and a pressurizing arrangement, including a pump mechanically driven from the engine, in the branch line leading to the primary injector or injectors to ensure adequate pressure for atomization at all total fuel flows. Fuel is supplied to the combustion equipment 41 from a tank 9 by a fuel pump 10. The fuel is heated in an oil cooler 13 and then passed to the control and metering mechanism 14. The fuel pump may be driven by the engine or by an air turbine 8. The fuel dividing system comprises branch lines 17a, 17b leading to a manifold 46 for the primary fuel injectors 15 and to a manifold 47,for the secondary injectors 16. The branch line 17a contains an auxiliary engine-driven pump 18. A relief valve 22 in a by-pass 21 limits the delivery pressure of the pump 18. A fuel recirculating by-pass conduit 23 is also provided around the pump 18. The branch line 17b has a non-return valve 24 and a shut-off cock 25 which is coupled with a shut-off cock 19 in the line 17a. At low fuel flows the suction effect of pump 18 prevents the pressure in the pipe 12 from exceeding that necessary to open the valve 24 so that the whole of the fuel is delivered to the primary injectors 15. As the fuel flow increases, the delivery pressure of the pump 18 increases until the relief valve 22 opens. Any further increase in total fuel flow increases the pressure in the pipe 12 so that the valve 24 opens and allows fuel to flow to the secondary injectors 16. Under some conditions of operation, e.g. at high altitude, the total engine fuel requirements may be so low that cavitation will tend to occur in the pump 18. When cavitation tends to occur there is no flow in branch line 17b so that combustion chamber pressure acts on one side of the land 28a and displaces the piston valve 28 to the right against the action of the inlet pressure of the pump 18 plus the load of the spring 32 (or less the load of the spring when the spring is in chamber 29) until the chamber 30 opens the conduit 23. The pressures in the chambers 30, 31 are balanced by a passage 34. A filter may be incorporated in the line 17a.