Patent GB-741855-A (GB)
Title: Improvements in compound internal combustion engines
Inventor: BERTIN JEAN HENRI
IPC: F02B41/06
Filed: 1953-11-20
Abstract: 741,855. Compound engines. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Nov. 20, 1953 [Nov. 27, 1952], No. 32216/53. Class 7(2) In a compound engine comprises a large diameter L.P. cylinder 7 fed with gases which have already undergone partial expansion in a smaller diameter H.P. cylinder 7, controllable means, such as the fuel injectors 5 and 10 or a device for adding fresh air to the L.P. cylinder not shown, is provided for operating, during - limited periods, the L.P: cylinder 7 with acombustion cycle whereby a higher torque is produced at a lower efficiency than during normal--high-efficiency running at rated torque when the L.P. cylinder 7 merely completes the expansion of .the motive gases which has started in the H.P. cylinder 1, the controllable means permitting the flow of combustion gas and fuel in the two cylinders to be varied to achieve a progressive variation of the torque at constant speed.' CONSTRUCTION. The H.P. cylinder 1 is provided in its lower part with piston-controlled inlet and exhaust ports 2 and 3, respectively; the exhaust ports are connected by a pipe 3a to an exhaust collector-chamber 6 that communicates with the inlet valve 8 of the L.P. cylinder 7, the latter having an exhaust valve 9. The L.P. piston 11 may be coupled to the same shaft, not shown as the H.P. piston 4. one piston being- at T.D.C. whilst the other is at B.D.C. The Underside of piston 11 acts as a compressor, air being drawn in from atmosphere through a pipe 14 and a port controlled by a valve 12, and expelled when a valve 13 is open. into an air collector-chamber 15 to which the inlet ports 2 are connected. A by-pass. 16 which joins the chambers 6 and 15 is controlled by a valve 17. The cylinder 7 has a bore diameter which is for example twice that of the cylinder 1; the piston strokes are of the same order. The valves in the L.P. cylinder 7 7 may be replaced by sleeves which may be adjacent to vary the timing; the valves of cylinder I may also consist of sleeves to permit of asymmetric timing. Any number of - cylinder pairs 1 and 7 may be used and the engines may operate on cycles other than the two-stroke cycle described, for example, ,either one or both of the cylinders may function on a four-stroke cycle. In the case of a carburetter engine a valve 14a in pipe 14 is constituted by the carburetter throttle valve. A centrifugal or volumetric supercharger may be connected to the pipe 14 and the compressor may be combined with the H.P. piston. RATED TORQUE OPERATION. The valve 17 is closed and atmospheric air is drawn into cylinder- 7 by the upward travel of piston 11 the air being compressed by the first portion of its downwards movement after which the valve 13 opens so that the piston moves to B.D.C. and discharges the air into the chamber 15 at which point the piston 4 is at T.D.C. and fuel injection and combustion take place in cylinder 1. When the piston 4 approaches B.D.C. the exhaust gases flow into collector 6, and the air in collector 15 scavenges the cylinder 1; the piston commences its upward motion and compresses the air until the injection and combustion part of the cycle recur. As the piston 11 descends the valve 8 opens and the mixture of exhaust gas and scavenging air from the collector 6 is drawn into the cylinder 7; the valve 8 is closed and the mixture expands until at B.D.C. the valve 9 is opened to permit exhaust thereof during the following upward travel of the piston 11. HIGHER TORQUE' OPERATION. The fuel injection into the cylinder 1 is reduced, the volume of air entering the cylinder 7 is increased by manipulation of the valve 14a, in the pipe 14, the valve 17 is opened, and the injector 10 is set to direct fuel into the cylinder 7 at the end of the admission phase thereto and cause combustion therein. The closure of valves 8 and 12 may take place earlier than for rated torque operation and the opening of valve 13 may be delayed.