GB1327017A - Fuel injection systems for gas turbine engines - Google Patents

Abstract

1327017 Gas turbine engine fuel systems ROBERT BOSCH GmbH 27 Aug 1971 [27 Aug 1970 7 Nov 1970] 40218/71 Heading F1G [Also in Division F2] A fuel system for a vehicle gas turbine engine comprises a fuel governer having an electromagnet arranged in the governer housing and connected directly to a control spool of a fuel metering valve, the pressure drop across the metering valve being maintained substantially constant by a valve in the fuel line downstream of the metering valve and responsive to the pressure drop, and the electromagnet being controlled by means responsive at least to the engine speed. The governer 1, Fig.11, comprises a shaft 2 driven by the compressor turbine of the engine and driving a gear pump 3 for the fuel and a toothed disc 49 which co-operates with correspondingly toothed yokes 50 to induce voltage pulses in coils 51 indicative of the speed of the compressor turbine. The fuel metering valve comprises a rotary spool 11 journalled in conical pivots and rotatable by means of a rotary magnet 18, Figs.4 and 11, acted on by coils 19 in opposition to a spring 77. The angular position of the spool 11 is communicated to an inductive transducer 32 via a cam 30 and a follower 31. Stop surfaces 75, 76 on the cam 30 co-operate with a stop plate 74 to limit the angular movement of the spool 11. The pressure drop across the metering valve is kept constant by a valve 36 located downstream of the metering valve and controlled by a diaphragm 37 subjected to the pressure drop. The valve 36 may comprise an axially movable spool valve or, as shown, the diaphagm 37 forms the movable element of the valve in co-operation with a valve seat 39. To protect the diaphragm 37 from excessive pressure differential, a valve 170 which opens on the occurrence of a pressure differential in excess of the normal maximum value may be provided in parallel with the valve 36. An electromagnet 66, Figs.5 and 11, holds open a shut-off valve 67 upstream of the pump 3. When the valve 67 is closed, it opens a return passage from the delivery side to the suction side of the pump 3. The valve 67 may instead be upstream of the burner nozzle. The various electrical connections are made via contact springs 59, 60 and a printed circuit board 58 to a socket 57 by means of which connection is made to an electronic governor which thus receives a signal indicative of the compressor turbine speed and also receives signals indicative of the accelerator pedal position, the temperature within the combustion chamber, and the atmospheric pressure. The electronic governor controls the metering valve and also the inlet guide vanes of the useful output turbine. It also de-energizes the electromagnet 66 to shut off the fuel supply in the event of an electronic fault, overspeeding or excessive temperature. In a modification, the metering valve and its operating electromagnet are of axially movable type and are co-axial with the valve position transducer.