GB596808A - Improvements in fuel supply systems for internal combustion engines, e.g. gas turbines - Google Patents

Abstract

596,808. Fluid-pressure servomotor-control systems. HOBSON (AIRCRAFT & MOTOR) COMPONENTS, Ltd., H. M., and GREENLAND. L. S. May 3, 1945, No. 11309. [Class 135] [Also in Groups XXVI and XXVII] In an internal-combustion engine, e.g. a gas turbine, having a servomotor controlling means for varying the rate of flow of fuel to the engine, and a governor for applying to the control valve of the servomotor, against a substantially constant biassing pressure, a force which varies with engine speed, speed selecting means is provided for adjusting the relationship between engine speed and the force applied to the valve by the governor. As shown in Fig. 1, liquid fuel is delivered by a pump 11 through a conduit 12 to a burner manifold 13, the rate of flow to the burners being determined by a needle valve 18 in a byepass 17. An enginedriven centrifugal impeller 30, constituting the governor, has its inlet connected to the byepass and to one side of a spring-loaded diaphragm 36 by conduits 32, 34, and its outlet connected, through a manually-operable rotary valve 39 for varying the effective radius of the impeller, to the other side of the diaphragm. A control valve 48 connected to the diaphragm, determines the position of the needle valve 18 by controlling the escape of fuel under pressure from one end of the servomotor cylinder 23, said end being supplied with fuel from the conduit 12 through a restriction 25, whilst the other end is subjected to the unrestricted pressure in the conduit 12. Rotation of the valve 39 causes a change in the pressure difference across the diaphragm 36 and consequently a change in the governed speed. The restriction 25 limits the rate at which the valve 18 tends to close should the valve 39 be rotated rapidly to reduce the effective radius of the impeller, i.e. to increase the speed, whilst an adjustable stop 51 associated with the diaphragm limits the opening of the valve 48 to regulate the rate of opening of the valve 18 when the valve 39 is rotated to reduce the speed. A normally open minimum-pressure valve 54, actuated by a diaphragm 55.,subjected on one side to the fuel pressure and on the other side to the combustion chamber pressure controls the servomotor to prevent the fuel pressure from falling below a minimum value under conditions requiring low fuel flow. In a modification, a mechanical governor 130, Fig. 3, which replaces the impeller, acts through a lever 63 upon a spring-loaded control valve 148. Adjustment of the speed is effected by moving the fulcrum 72 of the lever in a slot 73. In a modification of the arrangement shown in Fig. 1, the servomotor controls the output of a variable-displacement pump instead of a byepass valve, whilst in a further modification, also embodying a variable-displacement pump, the valve 39 is replaced by a valve controlling a connection between ,the eye and the tip of the impeller. The servomotor may be of the vane type. Specification 582,084 is referred to,