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Particulate matter emissions can jeopardize good health. Diesel particulate matter (PM), of diameters less than 10,000nm, was measured from a high-speed direct injection (HSDI) diesel engine by using an electrical low pressure impactor (ELPI). Results were obtained for the smoke level and the PM level (masses and numbers) from this engine by using the ELPI and the Bosch smoke meter, and the results were compared. The effects of a diesel oxidation catalyst (DOC) were also investigated. Under a high speed and high load condition, HSDI diesel engine exhausts a considerable mass of particulate matter with diameter over 100nm, and considerable number of PM from 7 to 100nm at the same driving condition. DOC showed reduction in the total mass of PM, but showed increase in the number of ultra fine PM. At low temperature, before light-off temperature of the soot, the DOC adsorbs the PM, and oxidizes the PM after the light-off temperature. Finely-sized PM could be created during oxidation.

We analyzed the in-cylinder flow fields of an optical-access single cylinder diesel engine with the PIV and STAR-CD CFD code. The PIV analysis was carried out in the bottom and side view mode during a compression stroke (ATDC 220°-340°) at 600 rpm. The flow pattern traced by the streamlines, the location of vortex center, the generation and disappearance of tumble, and the squish effect agreed well, as visualized by the PIV and CFD. Vorticity and spatial fluctuation intensities abruptly increased from ATDC 310, reflecting more complicated flow pattern as approaching TDC. In a quantitative sense, the velocity magnitudes obtained from the PIV were, on an average, higher than those from the CFD by 1 m/s approximately and the difference in velocity magnitude between them was about 26 %. In the CFD analysis, the standard high Reynolds κ-ε and RNG k-ε model were adopted for calculation with tetra and hexa or their hybrid meshes, to determine the turbulence model dependencies.