The effects of swirl on early flame development and late combustion characteristic were investigated using a high speed single-shot visualized SI engine. LDV measurements were performed to get better understanding of the flow field in this combustion chamber. Spark plugs were located at half radius (R/2) and central location of bore. High speed shadowgraphs at 20,000 frames/sec were taken to visualize the detailed formation and development of the flame kernel with cylinder pressure measurements.
This study shows that high swirl gives favorable effects on combustion-related performances in terms of the maximum cylinder pressure and flame growth rate regardless of spark position. However, at R/2 ignition the medium swirl shown desirable effects at low engine speed gives worse performances as engine speed increases than without swirl. There were distinct signs of slow-down in flame growth during the period when the flame front expanded from 2.5mm in diameter until it reached 5.0mm apparently due to the presence of ground electrode.