GB597952A - Improvements in the governing of free piston internal combustion operated compressors or gas generators - Google Patents

Abstract

597,952. Elastic-fluid turbines. ENGLISH ELECTRIC CO., Ltd., and WELSH, R. J. May 17, 1945, No. 12433. [Class 110 (iii)] [Also in Group XXVII] In the free piston gas generator shown (Fig. 1), a centrifugal governor 16 connected to an exhaust gas turbine 15 driven by exhaust gases from the exhaust pipe 12 of the generator controls an air inlet throttle 10 controlling the supply of air to the compressor cylinders. The reduction of the air pressure in the air inlet manifold caused by operation of the throttle valve is transmitted by a pipe 18 to a pressureresponsive device 19 which reduces the fuel supply by operating a control rack 28 of an engine fuel pump 29. The pressure-responsive device continues to reduce the fuel supply in step with a reduction in the pressure in the inlet manifold until a piston 34 of the pressureresponsive device comes up against a stop 26b. After the piston has reached the stop, further reduction in pressure in the air inlet has substantially no effect on the fuel supply. Further regulation is carried out by closing the throttle, the stroke being kept substantially constant by a device 22 responsive to the length of stroke. An increase of stroke reduces the fuel supply by operating the control rack 28. The device comprises a spring-pressed piston 23 supplied with air through a non-return valve 24 from the compressed air cushion 7a. A leak 22a is provided to enable air to escape from the working side of the piston. If the stroke increases, the pressure on the piston rises and moves the rod 26a so that it reduces the fuel supply and tends to return the stroke to normal. A modified stop is described which is spring pressed so that it can yield slightly under reduction of pressure in the inlet manifold and cause a slight reduction of the, fuel supply, but at a much lower rate than is the case prior to engagement with the stop. This is to reduce the tendency for the stroke of the pistons to increase during the second stage of regulation. In a modification, the centrifugal governor directly controls the fuel supply by operating the control rack 28 of the fuel pump. The air inlet throttle is operated by a device dependent on the stroke of the pistons similar to that previously described. In this arrangement during the first stage of operation, an inlet throttle valve is fully open and remains fully open until the governor has reduced the fuel supply to that value at which minimum length of stroke is obtained. After this, the device dependent on the stroke comes into action and closes the throttle valve, thus relieving the load on the compressor pistons and keeping the stroke substantially constant. A number of gas generators can be arranged to supply a single turbine and the throttle valve can be located in a single air supply pipe to a manifold common to the three generators or separate throttles for each generator can be operated by a single control. The operation of the throttle valve and the fuel supply need not be by means of a governor, but can be manual. A first member responsive to the pressure at the inlet to a compressor cylinder and a second member responsive to the maximum pressure in a cushion cylinder are coupled to a fuel supply control member, an air inlet throttle is operated by a governor of a prime mover in supply connection with the compressor or gas generator or by a manual member and the output is controlled in two stages by progressive closure of the air inlet throttle in the first stage, the length of stroke being progressively reduced to minimum stroke and the fuel supply being reduced by the first member and in the second stage the length of the stroke being kept substantially constant by throttling the air inlet and by the second member reducing the fuel supply. In a modification, the member responsive to maximum pressure in a cushion cylinder is coupled to the air inlet throttle, the manual member or governor is connected to the fuel supply member and the member responsive to the pressure at the inlet to a compressor cylinder is deleted. Specification 594,764, [Group XXVII], is referred to. Reference has been directed by the Comptroller to Specification 452,225.