To obtain a better understanding of the combustion process in a spark ignition engine with or without an unscavenged horizontal prechamber, the flame propagations in both the pre-and main chambers are simultaneously visualized with a high speed camera. By using a CCD video camera and a A/D converter, the flame photographs are converted into digital data and are image-processed with a personal computer to make more clear the flame front and to clarify its brightness level in the burnt gas region.
Consequently, the images of flame front for each crank angle enhanced by thresholding and edge-detecting techniques are used to make flame propagation maps, which are able to examine in detail the effect of torch jet on the combustion process. In addition, the brightness distributions of burnt gas obtained from the flame image data in the main combustion chamber show a resonable agreement with the gas temperature diagrams measured by an infrared pyrometer.
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