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This paper is concerned with the formation of Particulate Matter (PM) in direct-injection (DI) diesel engines. A system featuring an electromagnetically actuated sampling valve was used for sampling of gas directly from the combustion chamber. The concentrations of total particulate matter (TPM) and of its two components, the Soluble Organic Fractions (SOF) and the Insoluble Fractions (ISF), were determined at different locations in the combustion chamber at different sampling times (different crank angles). High concentrations of SOF were found at sampling positions along the spray flame axis. The concentrations of SOF and ISF were higher at sampling positions close to the wall than away from the wall. The results suggest that SOF formation is significantly affected by wall quenching. Also, the PM concentrations were much higher in the combustion chamber than in the exhaust.

A new mixture formation and combustion process for reducing both emissions and fuel consumption has been developed, where the fuel impinges onto the impinging surface and spreads into the free space, named the OSKA process. A single cylinder engine particulate emission test was conducted with full flow dilution tunnel. The OSKA process shows lower TPM (total particulate matter) emission than the conventional DI diesel at the corresponding operating condition. ISF(insoluble fractions) and SOF(soluble organic fraction) are lower than DI diesel's. Correlation between SOF and THC of OSKA engine is, however different from that of conventional DI diesel. OSKA emits lower THC than conventional DI diesel does at the same SOF emission. This is because the wall quenching effect is smaller in OSKA than in conventional DI diesel. A NEW MIXTURE FORMATION and combustion technology, impinging diffusion one named OSKA, has been developed by the authors.

A comparative study was performed by use of blends of Jatropha oil-diesel fuel and Jatropha oil-kerosene in order to investigate the feasibility of direct utilization of Jatropha oil in a DI diesel engine. Experimental results at low load demonstrated that mixing 60 vol.% of Jatropha oil into both diesel fuel and kerosene gave less impact on indicated thermal efficiency, whereas further increase of Jatropha oil deteriorated it. Jatropha oil-kerosene decreased particulate matter compared to Jatropha oil-diesel fuel, although particulate matter increased with the increase of Jatropha oil fraction. At partial load where double injection was applied, mixing 80 vol.% of Jatropha oil gave no significant impact on indicated thermal efficiency, exhaust gas emissions and particulate matter and no significant difference was observed between diesel fuel blends and kerosene blends.