Effects of Swirl/Tumble Motion on In-Cylinder Mixture Formation in a Lean-Burn Engine

Flow measurement by laser Doppler velocimetry and visualization of in-cylinder fuel vapor motion by laser induced fluorescence were performed for various types of intake systems that generated several different combinations of swirl and tumble ratios. The measured results indicate that certain swirl and tumble ratios are needed to achieve charge stratification in the cylinder. Performance tests were also carried out to determine the combustion characteristics of each intake system. Then, the features of combustion when the charge stratification was realized was analyzed.