Effects of late intake valve closing (LIVC) and rebreathing valve strategies on diesel engine performance and emissions at low loads

The results show that low NOx emissions can be achieved for these valve strategies with high In-EGR or Ex-EGR. However, the differences among various valve strategies on other emissions (CO, HC and Smoke) and combustion characteristics are sensitive to engine loads. Improved combustion and emissions can be achieved with rebreathing strategies at low loads (1-2 bar IMEPg), however, higher Smoke emissions and lower thermal efficiency are observed at higher loads. The lowest Smoke emissions can be obtained with the late IVC strategy, but at the same time with high CO and HC emissions, especially at lower loads. The suggestion is to use the rebreathing valve strategies at lower engine load from 1 to 2 bar IMEPg and then change to the standard and late IVC strategies at higher loads.