Fluid flow, combustion and efficiency with early or late inlet valve closing

摘要

This paper is a study of the effects of valve timing and how it influences the in-cylinder fluid flow, the combustion, and the efficiency of the engine. An engine load of 4.0 bar imep{sub}(net) was achieved by setting the inlet valve closing time early or late to enable unthrottle operation. Inlet valve deactivation was also used and asymmetrical valve timing, i.e., valve timing with the two inlet valves opening and closing at different times. The valve timing was altered by switching cam lobes between the experiments. The results indicate a longer flame development period but a faster combustion with early inlet valve closing compared to the throttled case. For late inlet valve closing, a variation in the combustion duration results. As expected, the pumping mean effective pressure (PMEP) was greatly reduced with early and late inlet valve closing compared to the throttled case.