Patent GB-728921-A (GB)
Title: Means for controlling the supply of liquid fuel to engines
Inventor: LAWRENCE OWEN NAPIER
IPC: F02C7/22
Filed: 1952-09-01
Abstract: 728,921. Gas turbine plant. LUCAS (INDUS. TRIES), Ltd., J. Aug. 25, 1953 [Sept. 1, 1952; Oct. 6, 1952; Nov. 20, 1952], Nos. 21912/62, 24947/52 and 29318/52. Class 110 (3). [Also in Group XXIX] Mechanism for actuating the control means of a liquid-operated servomotor for regulating the supply of liquid fuel to a jet-propulsion or gas turbine engine comprises interconnected diaphragms or pistons operable by oil pressures one of which is related to engine speed and the other of which is dependent in part on variations of viscosity of the oil. The arrangement is such that variations in viscosity and hence in the density of the oil are compensated. Fig. 1 shows the invention applied to the variable delivery pump described in Specification 577,016, [Group XXIX]. The swash-plate 14 of the pump is adjusted by the spring-loaded servopiston 11 under the control of a vent valve k carried by a spring-loaded lever i operated by a pair of diaphragms e, f of different area, connected by a stem g and loaded by a spring h. The diaphragms divide a body part a into three compartments b, c, d. Compartment b is subject to a pressure related to engine speed and generated by the pump rotor r which has inclined passages s and is driven from the engine. The compartment d is open to a source of low pressure such as the pump inlet t. The intermediate compartment is connected to a point between a restricted orifice 7 fed from a constant pressure chamber u and a viscosity sensitive device 10 connected on its outlet side to the pump inlet t and consisting for instance of a number of parallel wires or a plug of wire gauze in a cylindrical chamber. The constant pressure chamber u is fed from the pump delivery conduit 5 by a passage 4 the outlet of which is regulated by a valve carried by a spring-loaded lever 2 actuated by a diaphragm w subject to the load of a spring x and to pump inlet pressure on one side and to the pressure in the chamber u on the other side. In a modification (Fig. 2, not shown) the upper diaphragm e is smaller than the lower diaphragm f and the positions of the restricted orifice 7 and the viscosity-sensitive device 10 are interchanged. In a further modification of the form shown in Fig. 1, the constant pressure chamber u is dispensed with and the chamber c is fed through a restricted orifice from the pump casing q with oil at a pressure related to engine speed. An outlet from the chamber c passes through the viscosity sensitive device. In Fig. 3 the body part a has two chambers each divided into two compartments c, d and b, d by the diaphragms e, f these being of equal area. The two outer compartments d are connected to the pump inlet t. The compartment b is connected to the pump casing q and therefore to the source of oil pressure related to engine speed. The compartment c is connected to a constant pressure chamber such as u, Fig. 1, through a restricted orifice 7 and to the pump inlet t through the viscosity-sensitive device 10. In a development of this modification, the compartment c is connected through a restricted orifice to the pump casing q instead of to the constant pressure chamber. The servomotor may alternatively regulate a throttle, or a by-pass or other means for varying the fuel supply and may itself be controlled by a shutter which controls the supply of motive fluid to the servomotor.