GB620625A - Improvements relating to fuel-systems for gas-turbine-engines - Google Patents

Abstract

620,625. Fluid-pressure servomotor-control systems. HOOKER, S. G. Jan. 23, 1947, No. 2195. [Class 135] [Also in Group XXVI] In a gas-turbine plant comprising one combustion equipment and two independent rotors, over-speeding of either rotor produces a reduction in the fuel supply. Two fuel pumps 23, 24, operating in parallel are driven from rotor 14. They comprise speed-responsive means which reduce the pump outputs when a certain speed is passed. The other rotor is geared to a centrifugal pump 45, the delivery pressure of which also controls the pump output, to reduce it when a certain speed is passed. In an alternative arrangement, the pump 45 is omitted and the pumps 23, 24 are driven separately by the two turbine rotors. Each pump 23, 24 comprises a swash-plate 30, or, equivalent, the inclination of which is controlled by a piston 31. The piston is pressed upwards by a spring and is subjected above to the pump delivery pressure and below to the same pressure by fluid passing through a constricted orifice 34. The pump rotor 28, which carries the pistons 29, has radial passages 37 forming a centrifugal pump and the delivery pressure of this pump is applied to one side of a spring-loaded diaphragm 39. At an excessive speed, this pressure is sufficient to cause the opening of a valve 36 and the consequent lowering of the fluid pressure below the piston 31. The piston then moves to reduce the inclination of the swash-plate 30 and the output of the pump. The pumps are connected in parallel between the pipes 21, 27 and the spaces below the pistons 31 are connected by a pipe 32 so that the pistons 31 move together. The delivery of the pump 45 is applied to one side of another spring-loaded diaphragm and similarly controls a leak-valve 52 connected to the pipe 32. In the arrangement shown, one of the pumps 23, 24 may be omitted.