Patent GB-913483-A (GB)
Title: Gas turbine engine fuel system
IPC: F02C7/236
Filed: 1961-09-01
Abstract: 913,483. Gas turbine engine fuel systems; centrifugal pumps. GENERAL MOTORS CORPORATION. Sept. 1, 1961 [Sept. 2, 1960], No. 31454/61. Classes 110 (1) and 110 (3). A fuel system for a gas turbine engine comprises a source of fuel, two fuel pumps which are driven concurrently by the engine, one being a circumferential flow or vortex or turbine type pump supplied from the source and the other being a centrifugal type pump which may be supplied by the circumferential flow pump, the centrifugal pump being of greater volumetric capacity than the circumferential flow pump, an engine fuel flow control being interposed between the centrifugal pump and the engine, a conduit connecting the fuel source to the centrifugal pump so as to by-pass the circumferential flow pump, a check valve being disposed in the conduit allowing flow only from the source. The engine shown in Fig. 1 comprises a centrifugal pump 22 and a circumferential flow pump 24 mounted on shafts 21, 23, respectively, and driven from the engine through shaft 17 and gearing. Fuel may pass from a source thereof through duct 26, check valve 27 and duct 28 to the inlet of the centrifugal pump 22, the fuel discharging therefrom through duct 36, fuel control unit 37, duct 38 and shut-off valve 39 to the engine. Fuel may also pass from the duct 26, upstream of the check-valve 27, through duct 32 to the inlet of the circumferential flow pump 24, fuel discharging therefrom through duct 31 into the duct 28 between the check valve 27 and the inlet to the centrifugal pump. A relief valve 33 is disposed in a duct 34 connecting the outlet and inlet of the circumferential flow pump. The arrangement of the pumps is shown in Fig. 2, the reference numerals corresponding to those in Fig. 1. At starting the pressure rise developed across the circumferential flow pump 24 maintains the check valve 27 closed, fuel passing from the ducts 26 and 32 to the inlet 49 of the circumferential flow pump, fuel discharging therefrom through outlet 51 and duct 31 into the duct 28. The fuel then passes into the inlet 42 of the centrifugal pump and discharges therefrom through outlet 36. At low speeds, the circumferential flow pump develops considerably greater pressure than the centrifugal pump and is capable of meeting the engine fuel flow requirement. As the engine speeds up, the increased suction of the centrifugal pump causes the check valve 27 to open, and this pump then supplies the full pressure and quantity of fuel. The circumferential flow pump then merely runs idle. The spring-loaded relief valve 33 is disposed in the duct 34 interconnecting the ducts 31, 32 to relieve any excess pressure developed in the pump 24 when the shut-off valve 39 is closed. In a further arrangement, the relief valve 33 is omitted but a pressure-responsive shut-off valve is disposed in the inlet duct to the circumferential flow pump, the valve being responsive to the pressure in the outlet duct of the centrifugal pump. When this pressure reaches a certain value, the shut-off valve closes and thereafter the circumferential flow pump runs empty. A check valve is disposed in the outlet from the circumferential flow pump. The circumferential flow pump comprises a rotor disc 47 having radiallyextending vanes 48 on each side thereof adjacent the periphery, so as to form a series of pockets.