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Experimental studies of homogeneous charge compression ignition (HCCI) combustion have been conducted by using a compact rapid compression machine. The image of the cool flame was captured by a high-speed camera with image intensifier, and during the cool flame appearance the Emeleus cool flame band was observed. Then blue flame became evident, its emission spectrum being similar to that of the cool flame with overlapping by HCO bands. 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 oxidation 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 changed to red, especially at higher equivalence ratios. This red coloration must originate from the H 2 O vibration-rotation bands (580.7-966.9 nm). On the other hand, it has been revealed that a pulsed flame jet (PFJ) has the potential for directly controlling the start of HCCI combustion. In the jet of PFJ, the emission spectrum obtained was composed of distinct OH and CH emissions superimposed on the carbon monoxide oxidation continuum.

Experimenta1 studies of the Homogeneous Charge Cempression Ignition (HCCI) combustion have been conducted by using a compact rapid cornpression machine,The chemiluminescence spectra were obtained sequentially during the HCCI cornbustion, At the same tirne, the combustion processes were photographed using a high-speed carnera with image intensifier or a color high-speed camera. The image of the cool flame was captured by the high-speed carneTa with image intensifieg and during the cool flarne appearance, the Emeleus cool fiame band which originated from the formaldehyde chemiluminescence was observed in the obtained emission spectrum.Then blue flame became evident, its emission spectmm being similar to that of the cool flame with overlapping by HCO bands. During the main heat release duration, the hot fiame emissien spectrum was observed where the distinct OH emission at 306.4 nm 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 H20 vibration-rotation bands (580.7 -966.9 nm).On the other hand, it has been revealed that Pulsed Flame Jet (PFJ) has a potential for controlling the start of HCCI combustion directly. [[1ie chemiluminescence spectra and the color high-speed images of comhustion initiated by PFJ were also obtained,In the jet of PFJ, the emission spectrurn obtained was composed of the distinct OH emission at 306.4 nrri and CH emission at 43 1,5 nm superimposed on the carbon monoxide contirruum, chamber.Compressed air was accumulated in the driving air reservoir. wnen the diaphragm between the reservoir and the driving cylinder was ruptured by a needle actuated

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