GB1459560A - Method of reducing pollutants in engine exhaust gas before emission into the atmosphere - Google Patents

Abstract

1459560 Controlling composition of total exhaust gas NISSAN MOTOR CO Ltd 28 Oct 1974 [8 Nov 1973] 46485/74 Heading F1B A method of operating an I.C. engine in order to reduce the concentrations of harmful products in the exhaust gases before emission to atmosphere, the engine being one having an even number of combustion chambers, comprising the steps of dividing the combustion chambers into first and second groups each consisting of one half of the total number of combustion chambers, supplying a richer-than-stoichiometric mixture to the first group and a leaner-than-stoichiometric mixture to the second group, operating the engine so that each combustion chamber of the first group discharges a first exhaust gas simultaneously with discharge of a second exhaust gas from a predetermined combustion chamber of the second group and mixing said first and second exhaust gases in an afterburner. Engine 10 has a carburreter 20 which supplies a 12:1 air-fuel mixture to cylinders 11, 12 and 13, and a second carburetter 21 which supplies an 18:1 mixture to cylinders 14, 15 and 16. Valve and ignition timings are set so that cylinders 11 and 16 fire simultaneously, then cylinders 13 and 14 and finally cylinders 12 and 15. Cylinders 11, 12 and 13 exhaust into manifold 30 and the remaining cylinders into manifold 31. Manifold 30 opens tangentially into circular section reactor 53 and manifold 31 is positioned on the axis of the reactor and terminates in a swirl vane 59 to promote mixing of the gases. Unburned fuel and carbon monoxide in the exhaust gas from the first manifold is oxidized by the excess oxygen in the exhaust gas from the second manifold. In a modification, the tube 57 is closed-ended and the terminal wall portion is perforated. Air injection nozzles 61, 62 and 63 may be provided to supply secondary air under low load conditions. The pairing of the cylinders may be changed so that cylinders 11 and 12, 13 and 14, 15 and 16 fire simultaneously. Consequential modification of the manifolding is necessary. Fig. 4 (not shown) shows a four-cylinder engine in which cylinders 11b and 12b fire simultaneously and then cylinders 13b and 14b. The exhaust manifold 34 has a central partition 36 in its outlet 35 which leads into an inner cylindrical reaction chamber 73. Gases entering the chamber pass through perforated partitions 78, then through perforations 76 in the end portions of the cylinder into a space 74 between the inner chamber and surrounding outer chamber 72. Secondary air injection nozzles are provided. Pairing of the cylinders may be altered as in the sixcylinder engine.