GB808778A - Improvements in internal-combustion-operated, free-piston gas-generators - Google Patents

Abstract

808,778. Free-piston gas generators. MUNTZ & CO. Ltd., A. June 4, 1957 [June 19, 1956], No. 19005/56. Class 7(1) In an internal-combustion free-piston gas generator a duct connects the scavenge air reservoir directly with the compressor cylinder and a central valve is arranged to open the duct at low power levels and close the duct at higher power levels. As shown (Fig. 1), a duct interconnecting the compressor cylinder 13 with the scavenging reservoir 16 is controlled by a throttle valve 20 controlled by the scavenging air pressure which acts on a piston 21. In a modification, the arrangement is such that when the pressure in the engine case falls below a predetermined value, the throttle valve is opened by a cam fixed to the synchronizing mechanism of the pistons. In another modification, Fig. 3, the throttle valve 20 is controlled by a lever 25 which is acted on by pistons 21 and 32 which in turn are acted upon by pressures derived from the compressor cylinder and the engine case in the manner shown. In a further modification a piston similar to the piston 21 in Fig. 1 is acted upon by fluid pressure supplied by a control device rotated by the driven machine such as a turbine. The fluid pressure may be liquid or air pressure. The fluid pressure supplied by the control device may also be used for other control purposes such as the control of the fuel pump rack. The mechanical couplings used may be replaced by pneumatic or hydraulic couplings, the latter consisting for instance of a driving piston and driven piston connected by an enclosed column of oil. The control valve may be operated mechanically. It may be operated from the synchronizing gear provided to synchronize the movements of the two piston assemblies it may be opened for an equal fraction of the stroke before and after the inner dead point the period of opening being adjusted automatically by a mechanism controlled either directly or through a servo mechanism by the gas delivery pressure or by a control pressure for instance as described in Specification 787,430. Arrangements described in Specification 787,430 may be used with only such modifications as are needed in order to apply the invention. Connection with the compressor cylinder may be made through the cylinder wall near the inner end thereof where the suction valves are located.