The in-cylinder flow field of gasoline engine comprises unsteady compressib
le turbulent flows caused by the intake port, combustion chamber geometry.
Thus, the quantitative analysis of the in-cylinder flow characteristics pla
ys an important role in the improvement of engine performances and the redu
ction of exhaust emission. In order to obtain the quantitative analysis of
the in-cylinder gas flows for a gasoline engine, the single-frame particle
tracking velocimetry was developed, which is designed to measure 2-dimensio
nal gas flow field. In this paper, influences of the swirl and tumble inten
sifying valves on the in-cylinder flow characteristics under the various in
take flow conditions were investigated by using this P-TV method. Based on
the results of experiment, the generation process of swirl and tumble flow
in a cylinder during intake stroke was clarified. Its effect on the tumble
ratio at the end of compression stroke was also investigated.