Reduction of NOx emissions from a four-cycle stratified charge internal combustion piston engine is accomplished by (a) spark ignition of a rich mixture in a first chamber containing residual exhaust gas, followed by (b) torch ignition of rich mixture in a second chamber under turbulent conditions, causing (c) torch ignition of a stratified charge in a lean mixture in the main combustion chamber. The result is a reduction in peak temperature in the combustion process, with consequent reduction in NOx emissions in the engine exhaust gases. Exhaust gas is not recirculated. Said first chamber, which contains residual gas from the previous combustion cycle, contains the spark gap between spark plug electrodes and the spark gap is located near a restricted connection between the first and second chambers and remote from a closed end of the first chamber. Means are provided for changing the volume of said first chamber while the engine is operating, in accordance with variations in load on the engine.
展开▼
