Patent GB-1107643-A (GB)
Title: Improvements in or relating to engine fuel-control mechanisms
Inventor: GOSLIN GEOFFREY WALTER
IPC: F02C9/28
Filed: 1964-04-13
Abstract: 1,107,643. Gas turbine engine fuel systems; engine stopping. HAWKER SIDDELEY DYNAMICS Ltd. April 5, 1965 [April 13, 1964], No. 15181/64. Headings F1G and F1K. The invention relates to fuel control apparatus of an engine in which the fuel supply is arranged to be modified in the event of overspeeding of the engine so as to reduce the overspeeding, the invention being described with reference to a fuel control apparatus of a gas turbine engine in which the fuel supply is cut off in the event of overspeeding. The apparatus includes electrical generating means responsive to the speed of the engine to generate electric signal upon overspeeding which signal is utilized to cut off the fuel supply to the engine. In Fig. 1 fuel in line 1 passes to the inlet of pump 5 and passes by way of lines 6, 8 to a fuel control valve 11 which when fuel pressure is above a certain minimum valve opens to allow fuel to pass through line 13 to the engine combustion equipment. The fuel system comprises also a dump valve 22 which comprises a valve member 23 which controls communication between lines 20 and 19, the valve being shown in the closed position in which the lines 20 and 19 are not in communication. In the event of engine overspeed the dump valve is arranged to open so allowing lines 20 and 19 to communicate whereby fuel from the pump outlet passes back to the pump inlet. The pressure in line 8 thus falls and the valve member 14 of the fuel control valve 11 is moved by the spring 18 to the closed position shown so that the valve member 14 cuts off supply of fuel to the combustion chamber. The dump valve 22 comprises a valve member 23 disposed within cylinder 24 the cylinder extending into a chamber 29 to which fuel at high pressure within the line 8 passes through line 20 and restriction 44. The chamber 29 also communicates through a line containing filter 46 through an electro hydraulic valve 48 with a line 56 which connects with line 19 and so to the inlet of the fuel pump 5. The valve 48 is shown in the closed position so that high pressure prevails within the chamber 29 and so the dump valve member 23 is held in the closed position shown. In the event of engine overspeed an electric signal is applied to the solenoid 54 which acts to open the valve member 53 against loading of spring 55. The chamber 29 is thus placed in communication with the low-pressure at the inlet of the pump 5, and the high-pressure prevailing in the annular chamber 26 acts to move the valve member 23 to the right so placing lines 20 and 19 in communication so that fuel is diverted from line 8 back to the pump inlet and so fuel supply to the combustion chamber is cut off. When the valve member 23 moves to the right to the open position it acts against a plunger member 30 which is loaded by a spring 37. Also, the arms 33 which are pivotally mounted at 34 engage in the recess 39 in the valve member so that the valve member is locked in the open position. When it is desired to re-start the engine, the re-set plunger 31 is urged to the left so disengaging the arms 33 from the groove 39 and the valve member 23 is moved to the left to the closed position by the action of spring 37 on plunger 30. The electrical circuit of the solenoid 54 comprises a tacho-generator 61, Fig. 2, which supplies current to a transformer 63 from which pass two lines 64, 65. Current from line 64 passes to a rectifier 60 which supplies direct current to two lines 66, 67 across which are connected two trigger circuits 69 and 70, also two switches 74, 76 which are in series with the solenoid 54. The other output from the transformer 63 passes through line 65 to the high pass filter 68 from which currents pass to the two trigger circuits 69 and 70. In the event of engine overspeed the filter 68 permits signals to pass to the trigger circuits 69, 70 which act to close the switches 74, 76 so completing the circuit through the solenoid 54 so that the dump valve 22 is caused to open as described with reference to Fig. 1. Acceleration sensing units 71, 72 are also provided so that in the event of acceleration in addition to overspeeding further signals will be supplied to the trigger circuits 69, 70 to ensure quick operation thereof. The invention is applicable in the case of a gas turbine engine of the kind having a separate power turbine, the tacho-generator 61 being responsive to the speed of the separate power turbine. The acceleration responsive units 71, 72 would be effective in the event of rapid engine acceleration which might occur in the event of failure of the transmission.