Patent GB-787430-A (GB)
Title: Improvements in or relating to gas-generators of the internal-combustion-operated free-piston type
IPC: F02B71/06
Filed: 1955-02-22
Abstract: 787,430. Gas turbine plant. SOC. D'ETUDES ET DE PARTICIPATIONS, EAU, GAZ, ELECTRICITE, ENERGIE SOC. ANON. Feb. 22, 1955 [July 22, 1954], No. 5344/55. Class 110 (3). [Also in Group XXVII] An internal-combustion operated free-piston gas generator feeding a gas turbine comprises an engine cylinder, a compressor cylinder, a piston assembly including an engine piston connected to a compressor piston, these pistons operating in two cylinders respectively, gas passages coupling the compressor cylinder through a reservoir such as the engine case to the engine cylinder and coupling the engine cylinder through exhaust ports controlled by the engine piston to a load, means for varying the final compression pressure in the engine cylinder automatically in dependence upon the quantity of fuel supplied to the engine cylinder in such a manner that this pressure increases and decreases when the quantity of fuel is increased and decreased respectively, the final compression pressure during idling at low levels of fuel supply being so low that self-ignition of the charge in the engine does not occur even with the engine at its normal running temperature when the air supplied to the compressor cylinder is at atmospheric temperature and means for heating the air before it enters the engine cylinder during idling and at low levels of fuel supply in such a manner that selfignition takes place. As shown below a predetermined load, a valve 45 is opened, being operated by a piston 46 controlled by pressure from a governor 20 driven by the turbine 16. The valve allows hot air from the engine case to pass to the inlet of the compressor 8a and thus increases the temperature of the air supplied by the compressor. The valve 45 may be open when the final compression pressure is below 25 atmospheres. A valve 41 also controlled by the pressure from the governor 20 by-passes some of the gases from the generator at reduced loads. It is stated that the heat contained in the gases which escape through 42 may be used to heat the air supplied to the compressor. The fuel supply may be regulated by the governor 20 as shown or by hand. The regulator may be so arranged that with increase in load on the turbine the rod 15 is moved to the right to increase the fuel supply. A fuel stop 28 is controlled by the pressure in the engine case. At starting adjustable wheel 50 is used in order to obtain a relatively high final compression pressure. The governor 20 supplies a fairly high pressure to a fluid preferably a liquid. In a modification, the valve 41 and the reservoir 18 are omitted and the air instead of passing from the engine case 11 to the compressor inlet valves, is passed from the compressor cylinder back to these valves. The invention is applicable to opposed piston gas generators with synchronizing mechanism between the free pistons. Instead of using the mean pressure in the cushion 8b to act on the face S<SP>1</SP>, use may be made in known manner of the pressure in the cushion at a predetermined position of the piston 7.