Patent GB-1177634-A (GB)
Title: Fuel Control Systems for Gas Turbine Engines.
Inventor: LAWRENCE OWEN NAPIER
Filed: 1966-02-15
Abstract: 1,177,634. Gas turbine jet engine combustion equipment. JOSEPH LUCAS (INDUSTRIES) Ltd. Feb.14, 1967 [Feb.15, 1966], No.6513/66. Heading F1J. A gas turbine engine fuel system comprises a first passage connected to the outlet of a pump, further passages connected between the first passage and primary and main burners respectively, means responsive to changes in a predetermined variable to control the pressure of fuel supplied to the primary burners, a servo-operated throttle in the first passage to control the supply of fuel to the primary and main burners, the throttle being controlled from the means for controlling the primary burner pressure, a variable operatorcontrolled valve in series with the throttle in the first passage and also controlling the supply of fuel to the primary and main burners, and a device between the further passages and communicating with them, the device being responsive to the pressure of the fuel supplied to the primary burners, to control the pressure of the fuel supplied to the main burners, so that the flow rate to the main burners is maintained as a function of the flow rate to the primary burners. The invention is described with reference to a fan-type engine in which fuel is burnt in the fan duct to provide additional thrust, particularly an engine of this type in which the direction of thrust and the effective area of the exhaust outlet can be varied, additional thrust being required when the exhaust outlet is directed to provide a component of lift. The invention is also applicable to by-pass type engines. A fuel pump 18 is driven by an air turbine 17, the air being conveniently obtained from the engine compressors. Air inlet valve 15 and fuel inlet valve 19 are opened by a manual control 13. Another manual control 14 controls an air inlet valve 16 and actuates a drive mechanism (not shown) for inclining the exhaust outlet; in addition, it controls a multiple valve 20 having three lands for controlling the supply of fuel to the primary, main and igniter burners respectively of the fan duct. A throttle valve 21 between the pump 18 and the multiple valve 20 is controlled in accordance with, say, the pressure rise across the fan. For this purpose, a diaphragm 25 subjected on opposite sides to the air-pressures upstream and downstream of the fan operates a half-ball valve 31 in opposition to an evacuated capsule 26 and a piston 41 which is subjected to the pressure downstream of a restrictor 43. The throttle valve 21 is actuated by a piston 36 having a restricted passage through it, the valve 31 acting via a passage 34 as a bleed-off valve to control the position of the piston. The effect of this arrangement is to maintain the fuel pressure downstream of the restrictor 43 at a valve dependent on the pressure rise through the fan. This fuel pressure is applied to the primary burners 10 via a pressureresponsive spring-loaded valve 44 which controls the fuel flow to be proportional to the fuel pressure and therefore dependent on the pressure rise through the fan. The valve 44 may be omitted, a known type of burner 45 then being provided to obtain the same effect. Fuel is supplied to the main burners 11 through an orifice controlled by a diaphragm 49 subjected on one side to the pressure downstream of the restrictor 43 and on the other side to the pressure downstream of the part of the multiple valve 20 supplying the main burners, whereby the flow to the main burners is a predetermined function of the flow to the primary burners.