Abstract
An increase of the compression ratio is enumerated as one of the methods of improving thermal efficiency in the internal combustion engine. However, when the compression ratio is only increased, the knocking is generated. So, a knocking phenomenon is a problem for the thermal efficiency improvement. With the aim of understanding a knocking better, we paid attention to preflame reactions before the autoignition. And we tested it with spectroscopic measurement. And we measured a wavelength of the light emission of 306.4nm (an unusual range of OH) and 395.2nm (HCHO). By this experiment, we report the influence of preflame reactions.
