Transition Quality Between Spark Ignition and Homogeneous Charge Compression Ignition Modes Using Two Different VVT strategies: Cam Profile Switching and Phasing Strategy vs Fully Variable Valve Train Strategy

摘要

In a future ''hybrid'' mode internal combustion engine capable of running in spark ignition (SI) and Homogeneous Charge Compression Ignition (HCCI) modes, transition between these modes, during changes in engine load and speed, will play a crucial role. The valve train and engine management system must provide a fast and smooth transition between these two very different combustion modes keeping all relevant engine and combustion parameters in an acceptable range. To accommodate such transition a valve event (comprising duration, timing and lift) has to be variable, which consequently leads to high demands on the valve train and therefore a need for a high degree of flexibility. Two valve train concepts, one a cam profile switching (CPS) and phasing device, and the other Fully variable (Lotus AVT™) are presented. The use of both concepts for transitions from SI to HCCI to SI are experimentally investigated on a single cylinder research engine fuelled with commercially available gasoline fuel. Experimental results obtained together with benefits and obstacles in using each of these strategies are presented and discussed.