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Characteristics of PM and its compositions inside and outside of flame were required to develop reduction technologies for combustion origin PM. In this paper, relationship between PM size distribution and compositions such as soot and soluble organic fraction (SOF) of PM sampled with filter were investigated. Number distributions of PM (30 nm-10 μm) were measured using an ELPI (Electrical Low Pressure Impactor). Dry-soot and SOF in PM that was captured an individual stage of ELPI were analyzed using a combustion type PM analyzer (MEXA-1370PM). It was clarified that nuclei mode particle included more SOF than accumulation mode particle. PM characterization showed that there were many differences between in-flame PM and out-flame PM. In-flame PM contained much of low boiling point SOF and dry-soot composition was thermally unstable. Further, similarities between SOF in PM sampled with filter and gaseous hydrocarbons passing through PM filter were discussed.

New empirical equations to represent the Sauter mean diameter of a spray injected by a diesel nozzle are presented in this paper. In order to determine the new equations, drop sizes of a diesel spray were analyzed by a laser diffraction technique. Liquids with different viscosities and different surface tensions were tested to obtain the generalized empirical equations. The maximum injection and maximum ambient pressures were 90 MPa and 3.0 MPa respectively. Both the minimum value of the injection pressure to produce a fine spray and the Sauter mean diameter increase the greater the viscosity and the surface tension of the liquid. At a high injection velocity, the Sauter mean diameter increases with an increase in ambient pressure, but it decreases when ambient pressure is increased at a low injection velocity.