Patent GB-719012-A (GB)
Abstract: 719,012. Gas turbine plant SOC. DU. CARBURATEUR ZENITH. Nov. 25, 1952 [Nov. 26, 1951], No. 29803/52. Class 110(3) [Also in Groups XXVII and XXIX] A device 6, Fig. 1, for balancing the delivery of fuel from a number of reservoirs 1a, 1b, 1c, to an aircraft engine comprises a manifold 11, Fig. 2, connected to the engine and supply conduits 7a, 7b, 7c, from the-reservoirs containing metering restrictions 12a, 12b, 12c, upstream of which, are situated respectively a restriction 13 in the conduit 7a and throttle members 14b, 14c, in the conduits 7b, 7e, each throttle member being controlled by the pressure at a part 27 of the conduit 7a downstream of the restriction 13 and by the pressure at a point 15b, 15c, in its associated conduit downstream of the throttle member, whereby the pressure drops across and hence the flow through the metering restrictions are maintained in a predetermined ratio. The throttle members 14b, 14c, comprise shuttle valves 29b, 29c, movement of which to the right closes ports 21b, 21c to reduce the fuel flow in the pipes 7b, 7c. The chambers 23b, 23c are connected to the parts 15b, 15c, of the conduits 7b, 7c and the chambers 24b, 24c are connected to the part 27 of the conduit 7a, whereby the valves 29b, 29c, are actuated to maintain the pressures at the points 15b, 15c, equal to that at the point 27 and the flows from the reservoirs are thus maintained proportional to the size of the metering restrictions. The fixed restriction 13 may be replaced by a variable restriction comprising a spring-loaded valve which reduces the size of the restriction at low outputs. In a modification, Fig. 6, a throttle member 29a replaces the restriction 13 the chambers 24a, 24b, 24c all being connected to a pipe 37 which is connected by pipes 39a ... 39c to the parts 15a ... 15c of the conduits 7a ... 7c. Restrictions 40a ... 40c may be provided in the pipes 39a ... 39c so that if, e.g. the pressure at 15a is higher than that at 15b or 15c a pressure intermediate the two is produced in the pipe 37, whereby valve 29a moves to the right and valves 29b, 29c move to the left until equilibrium is restored, the system thereby being capable of balancing even if one valve abuts against its end stop. The throttle members 29a ... 29c may be arranged vertically in which case equilibrium is reached with one valve e.g. 29a in fully open position against its stop 17 and the other valves in intermediate position, the pressure at 15a being a small but negligible amount lower than that at 15b and 15c to produce an intermediate pressure in the pipe 37 which produces pressure differentials across the valves 29b, 29c, balancing their weight. A similar state of equilibrium i.e. with one valve in fully open position, can be arranged when the valves are disposed horizontally by producing a slight excess pressure in the pipe 37, either by inserting restrictions in the pipes 15a ... 15c between the points at which the pipes 25a ... 25c and 39a ... 39c open thereinto, or by connecting the pipe 37 to the conduit 7a upstream of the throttle member Alternatively the pipes 25a ... 25c may open into the throats of Venturi restrictions in the pipes 15a ... 15c. In a modification, Fig. 17, the shuttle valves 47 are formed with hollow pistons and the restricted passages 39a ... 39c, Fig. 6, are replaced by orifices 51 interconnecting the opposite ends of the valves. A leakage path past the part 52 of the valves may also serve to connect the pipe 37 to the upstream side of the throttling members. The fixed restrictions 12a ... 12c are also replaced by variable restrictions formed by slots 99a ... 99c in a spring loaded member 100 which is moved by the fuel pressure acting on the end 102 thereof through a pipe 103. In all of the above embodiments the restrictions 12a ... 12c may be replaced by Venturi restrictions to the throats of which the pipes 25a ... 25c, Fig. 6, are connected, for example as shown at 105a ... 105c in Fig. 20. In this modification two of the shuttle valves are replaced by a single shuttle 120 arranged to close the conduit 7a when the conduit 7b is opened and vice versa. In a further modification, the shuttle valves are replaced by diaphragm-actuated valves.