Patent GB-843059-A (GB)
Title: Improvements relating to gas turbine engine fuel controls
IPC: F02C9/16
Filed: 1958-05-21
Abstract: 843,059. Gas-turbine plant. GENERAL MOTORS CORPORATION. May 21, 1958 [May 28, 1957], No. 16305/58. Class 110 (3). In a fuel system of a turbo-propeller engine comprising a main fuel meter valve adjustable so as to maintain a constant turbine inlet temperature for a given throttle setting and a lowflow fuel control which below a given throttle setting takes over the full supply control from the main meter valve, the low-flow control has a loaded valve which closes when the flow from the main meter valve falls below a given rate and a pipe which starts from upstream of the main meter valve and supplies fuel to the engine by way of two valves one of which is positioned by means responsive to compressor inlet temperature and the other by means responsive to static atmospheric pressure. The normal fuel supply path to the engine from pump 10 is through line 13, main metering valve 14, line 16, pressurizing valve 17, line 18 and fuel shut-off valve 19. The main metering valve 14 is regulated by a control 23 which responds to the setting of the pilot's power control lever, rotational speed of the engine, engine air inlet temperature, compressor discharge pressure and the temperature of the combustion gases at the inlet of the turbine. Ram pressure may be used to control, instead of compressor outlet pressure. The metering head across the valve 14 is maintained constant by a by-pass valve 24. If the fuel pressure is insufficient to open the valve 17, the fuel will flow through a pipe 36 to a low flow control 37 which consists of a valve 68 controlled by bellows 76 responsive to the ambient static atmospheric pressure. The fuel then flows through a speed-controlled valve 39 which shuts off the low fuel control during starting of the engine. A by-pass around the main metering valve is also provided. This by-pass is provided with a make-up valve 43 which is controlled by a diaphragm 52 responsive to the pressure drop across the throttling valve 37 when the cut-off valve 39 is open and the loading of a spring 55 which is adjustable in response to changes in compressor inlet temperature. In a modification the cam 58 may be made responsive to ambient pressure and the valve 37 responsive to compressor inlet temperature. Under normal flight conditions fuel is metered by the valve 14 and flows through both valves 37 and 17 to the engine. If the throttle lever is now moved towards the closed position, a point will be reached in which all the fuel can be supplied through valve 37. Valve 17 then closes. When the control is set to flight idle, the main metering valve 14 will almost or entirely close, fuel then flows through line 42, make-up valve 43, lines 44, 16 and 36 and throttle valve 37 to the engine. The diaphragm 52 and spring 55 then control the valve 43 so that the pressure drop across the throttling valve 37 is proportional to the engine inlet temperature. The opening of the valve 68 is a function of ambient atmospheric pressure so that the fuel flow is proportional to ambient pressure and inlet temperature which factors are particularly suited to maintain constant engine power outputs.