Effects of Swirl and Spark Plug Shape on Combustion Characteristic in a High Speed Single-Shot Visualized SI Engine

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 obtain a better understanding of the flow field in this combustion chamber. Spark plugs were located at half-radius (R/2) and center of bore. High-speed Schlieren photographs at 20,000, frames/sec were taken to visualize the detailed formation and development of the flame kernel with cylinder pressure measurements.

This study showed that high swirl favorably affected combustion-related performances in terms of the maximum cylinder pressure and flame growth rate regardless of spark position. However, at R/2 ignition the low swirl showed desirable effects at low engine speed, and degraded performance as engine speed increased than without swirl. The effects of spark plug shapes and rotations on combustion performances at R/2 ignition and swirl were found.