The mechanism of an engine hybrid combustion concept with controlled auto ignition and spark ignition

Controlled Auto Ignition (CAI) uses the internal energy of the compressed charge to auto-ignite the mixture. Using internal exhaust gas re-circulation (IEGR) as an indirect control method, CAI offers superior fuel economy and pollutant emission reductions. Practically, this can readily be achieved by a method of early exhaust valve closure and late inlet valve opening to trap a large quantity of exhaust gas residuals within the cylinder from one cycle to the next. Although the emission and fuel economy can be largely improved, the engine power output is limited to part-load conditions only. At high-load, conventional Spark Ignition (SI) is required. In this research, both SI and CAI and the transition between the two were investigated on a single-cylinder research engine equipped with Lotus’ Research Active Valve Train (AVT) System. It was found that the potential hybrid combustion concept is consisted of four regions: conventional spark ignition combustion, spark ignition controlled auto ignition, spark ignition assisted auto ignition, spark ignition free controlled auto ignition.