Patent GB-866743-A (GB)
Title: Improvements in and relating to the controlling of installations comprising at leastone free-piston gas-generator and a turbine driven by power gas produced by the gas-generator
IPC: F02B71/00
Filed: 1958-02-20
Abstract: 866,743. Fluid-pressure servomotor-control systems. SOC. D'ETUDES ET DE PARTICIPATIONS EAU, GAZ, ELECTRICITE, ENERGIE S.A. Feb. 20, 1958 [April 5, 1957], No. 5602/58. Class 135. [Also in Groups XXVI and XXVII] A power plant comprising at least one freepiston gas generator and at least one turbine driven by the power gas from the gas generator in which control means operating in dependence upon the load on the turbine produces pressure variations in a fluid which controls the injection of fuel into the gas generator has the pressure variations arranged to act constantly as a correcting factor upon a stabilizer, which is controlled mainly by at least one internal pressure of the gas generator, so as to control the quantity of air in the cushion or cushions of the gas generator. A free piston gas generator, of which only the left-hand side is shown, comprising a pair of synchronized engine pistons 2 and compressor pistons 3,feeds a turbine with a governor both of which are not shown. The gas generator has the following control elements: (a) an element 11 for controlling the amount of fuel injected into the engine cylinder during each oscillation regulated by a toothed rack 16 ; (b) an element 17 for controlling the timing of the fuel injection; (c) an element 22 which limits the movement of the toothed rack 16; (d) a stabilizer 27 in the form of a slide valve interposed between the engine case 10 and each of the cushions b constituting the return energy accumulators; and (e) an element 35 which when the plant is running on reduced load permits compressed air to escape from the engine case. The fuel-regulating rack 16 and element 35 are controlled by impulses derived from the turbine governor which reach the respective controls through the conduit 36. These impulses are greater as the load on the turbine is greater. The toothed rack is controlled by a piston or bellows 38 acting through a bell-crank 25. The pressure in the conduit 36 controls the valve 35 so the valve is fully open for idling and gradually closes as the turbine load increases and at the intermediate load closes completely. The injection timing control element 17, the stop 22 and the stabilizer 27 are mainly controlled by internal control impulses. The elements 17 and 22 are mainly controlled by a pressure derived from the cushions b when the moving assemblies are in a predetermined position in their cylinders as determined by the position of the slide valve 69. The elements 17 and 22 are actuated by a piston 57 the position of which is determined by a spring-loaded piston 51 responsive to the pressure in the cushions b. The stabilizer 27 is controlled by a differential piston 60 responsive to the pressures in the cushions b and the engine case 10. The arrangement is such that if the pressure in the cushion b is predominant, the stabilizer 27 moves and allows air to escape from the cushion to the engine case and if the pressure in the engine case is predominant, the stabilizer moves to increase the amount of air in the cushions b. There is some time lag in the change of pressure consequent upon changes of load. To hasten the re-establishment of equilibrium after a change in load, the stabilizer is also controlled by impulses derived from the turbine governor. The piston 60 is made subject to the pressure in the conduit 36 so that sudden variations in this pressure will cause a movement of the stabilizer. A valve 69 is provided to disconnect the conduit 36 when starting up a gas generator connected through a common header to a number of gas generators The pressure in the conduit 36 may also act on the injection timing 17 and stop 22 only when there is an abrupt increase in the turbine loading. The pressure in the conduit 36 acts on a piston 66 against the action of a spring 68 to contact the piston 51 which actuates the control elements 17, 22. When the pressure in the conduit 36 falls due to a decrease of load, the piston 66 drops into its cylinder without moving the piston 51.