Turbulence and Cycle-by-Cycle Variation of Mean Velocity Generated by Swirl and Tumble Flow and Their Effects on Combustion

Abstract

Combinations of swirl flow and tumble flow generated by 13 types of Swirl Control Valves were tested using both an impulse swirl meter and LDV. The LDV used in this study was developed especially for engine research to realize stable beam crossing at very narrow beam waists to achieve high spatial resolution measurement. It is shown that tumble flow generates turbulence in the combustion chamber more effectively than swirl flow, and that swirl reduces the cycle variation of mean velocity in the combustion chamber. Performance tests are also carried out to determine the combustion characteristics under the condition of homogeneous charge. Tumble flow promotes combustion to a greater extent than expected from its turbulence intensity. It is also shown that the lean-limit air/fuel ratio is not strongly related to cycle variation of mean velocity but to turbulence intensity.