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Means for reducing the particulate matter (PM) from swirl chamber type diesel engines were searched out, and the reducing mechanisms were examined using an optically accessible engine. The following points were clarified in this study. 1. At light load, the suppression of the initial injection rate reduces PM, because SOF is reduced by the change in ignition point and smoke is reduced by the retarded flowout of the dense soot from the swirl chamber 2. Under medium and high load conditions, the main cause of the exhaust smoke is fierce spray-wall impingement which leads to fuel adhesion on the wall and the stagnation of a rich fuel-air mixture. 3. Enlarging swirl chamber volume ratio suppresses the formation of dense soot in the swirl chamber. In the main chamber, however, the soot oxidization becomes insufficient due to the mixing effect reduced by the essentially decreased chamber depth. 4.

With the aim to successively remove particulate matter (PM) from exhaust emissions of diesel engines, non-thermal plasma (NTP) system is now under development for practical use. The model analyzer for generating plasma with unit-cell of the NTP reactor, was designed and developed for the quantitative analysis of discharged plasma. The novel NTP reactors with newly developed porous and wave-foil electrodes show excellent plasma specifics such as low Inception voltage for plasma discharge and strong radiation luminance. A virtual vehicle simulator using an engine dynamometer, aiming at the evaluation of the plasma PM removal properties in various modal driving schedules, was constructed. It is confirmed that the novel NTP reactor shows not only excellent PM removal properties but also minimized pressure loss. Especially, PM removal properties are strongly influenced by the increase in plasma radiation luminance.