Emission Characteristics of OH and C₂ Radicals under Engine Knocking

抄録

Emission from the area of autoignition in an actual S. I. engine is observed under knocking operation using optical fibers. The difference in emission intensity observed between knocking and nonknocking operation is mainly due to the emission intensities of the OH and C₂ radicals. The emission intensity from these two species increases sharply when autoignition occurs. In addition, emission intensity from the C₂ radical shows two peaks in some cycles. Since the first peak is due to the autoignition reaction, the second peak is thought to be caused by soot formation in some cycles under knocking operation. This second peak corresponded to shadowlike matter seen in high-speed shadowgraphs taken during the expansion stroke.