An investigation of DME HCCI combustion using spectroscopic analysis

In order to control the ignition timing and overall combustion rate of HCCI, it is important to have a firm understanding of the chemical reactions of fuel because HCCI can be characterized as controlled chemical auto-ignition process. One technique that can be employed to gain a better understanding of the HCCI combustion process is chemiluminescence, which is the light emission from the excited state of intermediates or radicals. The objective of this study is to experimentally investigate the correlation between chemiluminescence of the active species, which play important role in the ignition, and HCCI combustion characteristics for providing the way to control auto-ignition process. In addition, a combination of experimental and computational results is employed. The experiments were conducted using optical accessible engine, photo-multiplier and band-pass filters. Senkin application of the CHEMKIN-II kinetics rate code was used for computation. As the result, there was a precise correlation between the rate of heat release and chemiluminescence intensity of OH (307.4 nm) and all band (350-700 nm) by tracing the in-cylinder mass-averaged. The start timing of emitting luminescence in OH coincided with H₂O₂ dissociation, and the peak timing of emitting luminescence in all band corresponded to the CO-O recombination spectrum.