SI engine combustion wall thermal management potential without the presence of control limitation

Tight future CO2 emission targets have encouraged extensive research in options for improving internal combustion engine efficiency. Amongst those, engine thermal management is a promising area to improve fuel economy, engine power and even reliability. Earlier studies have shown that engine thermal management was not just protecting engine from overheating but it also can improve engine performance, fuel consumption and even emissions. However, the effects and limits of thermal management are highly complex, and a better understanding is required to reach the full potential. The aim of this paper is to demonstrate the potential of manipulating combustion wall temperature for improving engine efficiency. A 1D numerical model of a 2.2L natural aspirated engine was developed using GT-Suite software for this purpose. The spark timing and fuelling in the engine model was also recalibrated to explore the indirect influence of thermal management influence on engine efficiency. The model assumes that the optimal temperature can be achieved at all times, ignoring some of the control implementation issues for now. The results show that optimized combustion wall temperature produces significant fuel consumption improvements at low to medium engine speed at both low and high load. The comparison with conventional temperature control was made using 7 legislated and academic test cycles. The highest fuel economy improvement of about 4% was recorded in urban test cycles. A smaller improvement of more than 2% was found for motorway driving. The results are due to improved combustion and lubrication only, not including reduced hydraulic losses.