Chemiluminescence spectral analysis and photographic observation in homogeneous charge compression ignition combustion

The chemiluminescence spectra were obtained sequentially during the Homogeneous Charge Compression Ignition (HCCI) combustion. At the same time, the combustion processes were photographed using a high-speed camera with image inensifier or a color high-speed camera. The image of the cool flame was captured, and the Emeleus cool flame band was observed. Then blue flame became evident. During the main heat release duration, the hot flame emission spectrum was observed where the distinct OH emission appeared, and it was superimposed on the carbon monoxide continuum. After the main heat release, the broad peak of the spectrum was shifted to the longer wavelength side, and the images of the flames change to red, especially at higher equivalence ratios. This red coloration must be originated from the H₂O vibration-rotation bands. The chemiluminescence spectra and the color high-speed images of combustion initiated by Pulsed Flame Jet (PFJ) were also obtained. In PFJ, the emission spectrum obtained was composed of the distinct OH emission and CH emission superimposed on the carbon monoxide continuum.