GB924141A - Improvements in or relating to liquid fuel systems - Google Patents

Abstract

924,141. Gas turbine Jet-propulsion plant; centrifugal pumps. ROLLS-ROYCE Ltd. Nov. 3, 1959 [Nov. 11, 1958], No. 36279/58. Classes 110 (1) and 110 (3). In a liquid fuel system comprising a number of liquid fuel pressurizing pumps delivering in parallel to a common liquid fuel supply line, delivery control means comprising a number of fuel-delivery-varying throttle valve parts are allocated one to each pump to vary its delivery into the common liquid fuel supply line, and a common actuating mechanism is provided for the throttle valve parts whereby they are adjusted simultaneously and in a like manner. In the gas turbine engine shown, two centrifugal fuel pumps 22 deliver through separate non-return valves 22b and separate throttle valves 24e to a common delivery line 23 containing a metering valve 26 and a non-return valve 27 and leading to a reheat burner 21. The throttle valves 24e are operated in unison by a piston 36 subjected on one side through a conduit 39 to an air pressure derived from the space between the flame tubes 12a and the surrounding air casing and controlled by a selector valve 40, and subjected on the other side through a conduit 38 to the static pressure in the jet pipe 18, the difference between these pressures acting on piston 36 tending to open the valves 24e while the fuel delivery pressure, applied through a conduit 29 to a chamber 24f, tends to close the valves 24e. When the engine is of the by-pass type, as shown, the valves 24e may also be urged in the opening direction by the air pressure in the by-pass duct 20, applied through a conduit 47 to an additional piston 45. To control the pressure applied through conduit 39 to piston 36, the selector valve 40 has a throttle valve element 41a which varies a bleed to atmosphere past a spring-loaded valve 44. The pumps 22 are driven by air turbines 30 supplied by way of a shut-off cock 32 with air from the space between the flame tubes 12a and the surrounding air casing. When the selector valve 40 is moved from the no-reheat position shown, a land 41c closes the end of a bleed conduit 35 to allow pressure to build up in the conduit 35 to open the cock 32. If the jet pipe temperature becomes too high, a thermostat 70 operates a solenoid 71 to open a bleed valve 72, whereby the pressure in conduit 35 drops to atmospheric and the cock 32 closes to shut off the supply of air to the turbines 30. Ignition at the reheat burner 21 is effected by means of a pump piston 51 which delivers a shot of fuel to auxiliary injectors 61 in the main combustion equipment to cause a flash of flame through the engine into the jet pipe 18. For this purpose, a bleed-off valve 55 is closed to cause fuel pressure to build up to the right of piston 51 and move the piston to the left. Closure of the valve 55 occurs when the pressure in the delivery line 23 has been built up sufficiently by the pumps 22 and is effected by means of a diaphragm 62 subjected on one side to the pressure in the jet pipe 18 and on the other side to the pressure in the delivery line 23.