GB706743A - Improvements relating to mechanism for controlling the speed of prime movers - Google Patents

Abstract

706,743. Speed governor; gas turbine plant. S. U. CARBURETTER CO., Ltd., and ROLLSROYCE, Ltd. Feb. 2, 1953 [Feb. 20, 1951], No. 4439/32. Classes 57 and 110 (3). [Also in Group XXIX] A speed-limiting governor contains an osci!- latable control device 2, Fig. 3, comprising an elastically-constrained pendulum with a liquidfilled bob divided into two chambers 5, 5A connected by means permitting transference of liquid to take place from one chamber to the other more readily in one direction than in the opposite direction to produce a pressure difference which is applied to a pressure-responsive system arranged to control the power regulator of a prime mover. Periodic impulsers, of frequency correlated with the instantaneous rotational speed of the prime mover, are applied to the pendulum which reacts to them at resonant response only when their frequency is close to, or at, the value which corresponds to the predetermined maximum speed of the prime mover which may be an internal-combustion engine, gas turbine, steam reciprocating engine or steam turbine. The impulse may be derived from a magnet 12 rotated by the engine and co-operating with a pole-piece 13. At resonant frequency the liquid, which may be mercury, surges through a venturi duct 6 or a non-return valve to produce the pressure difference which is communicated by ducts 9A either to bellows or capsules connected with opposite ends of a first-order lever linked to the engine regulator or to a spring-loaded diaphragm 86 in a servo mechanism. The diaphragm tilts a flexibly-mounted bar 90 to open a ball valve 94 which allows fuel to flow from a centrifugal pump 79 to a cylinder 98 provided with an outlet restrictor 101. A spring-loaded piston 99, displaced by the fuel, restricts the opening in a throttle 82 and hence reduces the speed of the engine. The chambers 5, 5A have distensible walls, and to prevent the possibility of the engine accelerating rapidly past the resonant frequency of the governor, a spring- loaded piston 14 may be provided so that when the pendulum is initially set into vibration the pressure difference acting through ports 16, 17 raises the piston against its spring and increases the resonant frequency. Alternatively, this result may be achieved by providing rigid cam surfaces to constrain the swing of the pendulum. The piston 14 may be controlled by a separate venturi duct. Figs. 8A and 9 show a torsional pendulum in which two chambers 46, 47 connected by venturi ducts 45 produce a pressure difference across a diaphragm 50 connected by a push rod 52 to the engine. Two spring-loaded piston 54, which are displaced inwardly by the pressure difference once the pendulum starts to vibrate, may be provided to increase the resonant frequency. Alternatively, the pendulum shaft may have splines to co-operate with cam surfaces. The pendulum may be excited by a rotating magnet 12 or by a pair of air-discharge pipes which are rotated through gearing from the engine and directed onto inclined vanes on the pendulum periphery.