Patent GB-1224141-A (GB)
Title: Fuel systems for gas turbine engines
Inventor: GASCOIGNE DENIS
Filed: 1966-08-23
Abstract: 1,224,141. Gas turbine engine fuel systems. JOSEPH LUCAS (INDUSTRIES) Ltd. Nov.23, 1967 [Aug.23, 1966; Dec.21, 1966], Nos.37676/66 and 57183/66. Heading F1G. In a gas turbine engine fuel system comprising a fuel pump supplying fuel to the engine via a control device with which is associated a manually controllable throttle, an emergency fuel-flow passage means is provided for by-passing the control device, the flow through the emergency passage means being controlled by a second throttle which is connected by a linkage to the manual control for the first throttle, and a device to act upon the linkage to control the position of the second throttle in accordance with at least one variable related to conditions within the engine. The fuel system shown in Fig.2 comprises a fuel pump 10 supplying fuel to main burners 12 via a control device 16 containing a throttle operated by a manual control 17, and a governor device 19 responsive to engine speed. The pilot burners 13 are fed from the control device 16 via a passage 14b. A servocontrol 11 controls the pump output in accordance with the fuel pressure at the main burners 12. Normally, a valve 15 is positioned to allow flow from the pump discharge passage 14 to the control device 16. If the control device 16 fails, the valve 15 is turned to the emergency position shown, in which the pump 10 feeds the burners 12, 13 through passages 21, 22 by passing the control device. The valve 15 can then be controlled by the manual control 17 to variably throttle the flow to the passages 21, 22. For this purpose, the valve 15 is connected to the manual control 17 by a linkage having a input member 27 connected to the manual control and an output spindle 26 directly connected to the valve, the linkage being of the form described in Specification 1,224,142. The changeover of the valve 15 from a normal positon to an emergency position, and vice versa, is effected by movement of a second input member 28 of the linkage by means of a piston 42. The piston 42 operates within a cylinder having its right-hand end connected to the pump discharge via a passage 60 and its left-hand end connected to the passage 60 via a restrictor 61. The left-hand end is also connected to a drain passage via a passage 62, a valve 63, a passage 58 and a half-ball valve 51 carried by a lever 49. During normal operating, the valve 63 is closed by a piston 64 which abuts it. To effect the changeover to emergency operation, the piston 64 is moved to the position shown. This allows the valve 63 to open to reduce the pressure acting on the lefthand end of the piston 42, which consequently moves to a position in which, acting through the second input member 28, it moved the valve 15 to an emergency position. Thereafter, control of the valve 15 as an emergency throttle is effected partly by the manual control 17 and partly by the piston 42, the latter beingunder the control of the compressor discharge pressure acting through bellows 55 in oppositon to an evacuated bellows on the half-ball valve 51. Follow-up is effected by a cam 46 acting through a follower 47 and a spring 48. Movement of the piston 64 from its normal position to its emergency position and vice-versa, is effected by opening the appropriate valve 70 or 71 by means of a respective solenoid 72 or 73 to admit fuel at discharge pressure to one side or the other of an enlarged central portion of the piston 64. After de-energization of the solenoid, the piston 74 is retained in the selected position by pressure communicated through the opened valve 63 or a duct 79, as the case may be. In another embodiment, Fig.1 (not shown) the changeover to emergency operation is effect by opening a solenoid valve (34). The second input member (28) is then controlled by a piston (31) acting through a spring (32), the fluid-pressure acting on the piston being varied by a half-ball valve (36) under the control of engine air intake pressure, engine speed or compressor discharge pressure.