Patent GB-932202-A (GB)
Title: Improvements in fuel supply systems
Inventor: TYLER STANLEY RALPH
IPC: F23K5/04
Filed: 1958-09-29
Abstract: 932,202. Supplying liquid fuel to burners. DOWTY FUEL SYSTEMS Ltd. Sept. 28,1959 Sept. 29, 1958], No. 31064/58. Class 75 (1). [Also in Groups XXVI and XXIX] Fuel is supplied to a spill burner of a gas turbine engine by a variable displacement pump 7 and a centrifugal circulating pump 6 (both engine-driven) and a valve 12 is disposed in the supply pipe 2 and is adapted to reduce the flow of fuel from the circulating pump 6 to the burner as the pressure in the spill pipe 3 is increased by increased output from the variable displacement pump 7. At low burner rates fuel is returned by the spill pipe 3 but at high burner rates fuel is supplied to the burner by the spill pipe 3 as well as by the supply pipe 2. The valve 12 comprises a waisted piston 15 adapted to control fuel flow between inlet and outlet ports 16, 17 in a cylinder 14 connected at one end to the spill line 3 and at the other end to the combustion chamber of the engine. The valve 12 causes fuel to flow along the spill line to the burner at lower supply rate from the variable displacement pump 7. In order to prevent fuel being supplied by the spill line 3 to the burner when the pressure is insufficient to effect atomization, for instance at starting; a non- return valve la is disposed in the return line and is opened by the fuel pressure in the supply line 2. A practical form of the piston valve 12 is shown in Fig. 5 and comprises a piston 15 sliding in a bore 14 formed by two spaced portions, the left-hand portion being formed as a part of an outer casing and the right-hand portion being an insert 23 locked in the casing by a nut 27. A cylindrical member 25 is secured to the part of the piston 25 between the two bore portions and slides in a sleeve 26 in the casing to obturate a port 28 in the sleeve. Fuel supplied to the casing at 16 passes through the port 28 and then through a further port 29 in the sleeve to a discharge port 17. The lefthand portion of the bore is connected to the spill line and the right-hand portion to the engine compressor output. In the modified construction shown in Fig. 6 the fuel flow in the supply line is controlled by a valve 36 secured to a servo piston 39 in a cylinder 39. The piston is operated by flow of fuel from the output of the variable displacement pump 7 through a pipe 43, a slide valve 53a, pipe 34a, a restrictor 33a in the piston, pipe 35a back to the control valve. The latter is disposed in a casing connected to the inlet side of the variable displacement pump 7 by a pipe 51 and is actuated by a pivoted lever 52 operated by a rod 59 connecting a bellows 55 connected to compressor output pressure with a rubber pressure pad 56 responsive to spill pressure. In operation as spill pressure increases slide valve 53a rises and consequently piston 39 rises to throttle the flow of fuel at valve 36. In the embodiment shown in Fig. 7, the pump 107 supplying the circulating pump 106 is a vapour-cored centrifugal kind, as disclosed in Specification 842,354. Fuel is fed to the inlet 109 of the vapour-cored pump 107 by a pipe 118 and the inlet flow is controlled by a valve 117 actuated by a servo piston 114 in a cylinder 115. The position of the piston 114 is determined by the flow of fuel from the output 111 of the vapour-cored pump 107 through a pipe 119 to one side of the piston 114, through a restrictor 121 to the other side of the piston and then through a vent valve 113 controlled by a control unit 108. The fuel flow from the circulating pump 106 to the burner 101 is controlled by a piston valve 132 actuated by a piston 134 which on one side is acted on by the fuel output pressure of the vapour-cored pump and at the other side by the pressure of fuel flowing through a restrictor 136 and through a servo vent 131 controlled by a lever 125 actuated by a rod 128a connecting two opposed bellows 126, 127. Bellows 126 is connected to a passage 123, terminating in the vapour-cored pump 107 at the minimum desirable radius for the fuel annulus within the pump, and bellows 127 is connected to a passage 128 opening at the centre of the pump. During normal operation both bellows are subjected to vapour pressure and do not cause opening of the vent 131. If the control unit demands a large fuel flow the fuel annulus in the vapour-cored pump 107 covers the end of the passage 123 and the pressure in bellows 126 causes vent 131 to close more closely, thus causing piston 134 to move to throttle valve 132 so that less fuel flows from the circulating pump to the burner. In a further embodiment, Fig. 8 (not shown), a single vapour-cored pump serves both as the main supply pump and the circulating pump and the controls are similar to those of Fig. 7. The burner nozzle is described in Specification 649,970. Reference has been directed by the Comptroller to Specification 843,344.