GB776347A - Improvements in and relating to liquid fuel supply systems for gas turbine engines - Google Patents

Abstract

776,347. Gas turbine plant. DOWTY FUEL SYSTEMS, Ltd. April 28, 1955 [Jan. 28, 1954], No. 2635/54. Class 110 (3). [Also in Group XXIX] A governor for controlling the supply of liquid fuel to a gas turbine engine comprises a spring- loaded servo-piston 7 controlling a fuel by-pass 4 around a pump 1 or, alternatively, strokevarying means of a variable displacement pump, a vent valve 18 controlling the pressure in a cylinder 10 and carried by a lever 19 actuated by a bellows 23 subject internally to a pressure which is a function of turbine speed, and a pair of pistons and cylinders 24, 26 and 25, 27 for moving the fulcrum 21 of the lever to obtain proportional, differential, and integral control effects. A dashpot arrangement 36 between the bellows 23 and lever 19 functions as an anticipator by opening the vent valve earlier upon a rapid increase in speed. The force exerted by the bellows 23 is balanced by a manually adjustable spring 22. The pressure in the conduit 17 between the cylinder 10 and the vent valve is communicated to the cylinder 26 through a conduit 31 so as to move the fulcrum 21 to provide proportional control but a restriction 32 introduces a differential function. The integral action is obtained by a connection 33 including a restriction 34 to the cylinder 27 whereby piston 25 resets the fulcrum 21. An hydraulic accumulator 35 permits liquid to escape from the cylinder 27 on initial movement of the pistons 24, 25. Motive fluid for the servo piston 7 is obtained from the fuel conduit 3 through a constant pressure valve 12. Instead of the governor being responsive to speed it may, alternatively, be controlled by some other engine operating variable such as jet pipe temperature. of priming liquid can be trapped in the casing. On starting, the liquid is pumped out into a volute 7, and passes by way of an opening 31 into an arcuate duct 30 which opens at a port 13 into a chamber 14. From chamber 14, the liquid passes through an open valve 15 back to the inlet 4 of the impeller 3, carrying some air from a suction passage 25. When the air reaches the volute 7 with the re-circulated liquid, it separates and escapes through the discharge 10. The removal of air allows liquid to enter the pump through the suction branch 23, forcing a non-return flap valve 12 upwardly. A toe-piece 17 on the valve 12 engages a collar 18 on the spindle 16 of the valve 15 to raise the valve 15 towards its closed position, this action being assisted by the pressure of liquid in the chamber 14 acting on the underside of the valve 15. Closure of valve 15 stops the priming action. When the pump is stopped, valve 12 closes to prevent liquid from siphoning back from the pump to the suction pipe. The impeller 3 is of double-sided type, with opposite inlets 4 and 5 connected to alternate blade passages, so that during normal operation the flow occurs alternately through the inlets 4 and 5. During the priming operation, the priming liquid is pumped from the inlet 4 only, and the blade passages connected to the inlet 5 are empty except for liquid flowing back in from the volute 7. This liquid is immediately returned by centrifugal action to the volute 7 carrying air with it. Valve 12 may be of the ball type.