Physico-chemical Properties of Diesel Exhaust Particulates

Diesel particulate matter (PM) has brought about huge environmental problems. The diameter of diesel PM is smaller than 1 μm that could be easily inhaled into the respiratory system. The PM diameter is smaller if turbocharger and common rail are used. Restrict exhaust emission legislations were carried out to decrease diesel PM emissions both in mass and number level. The formation mechanism of diesel PM is complex, and the cylinder combustion conditions have a huge effect on PM physico-chemical properties. In this chapter, the detailed analysis of diesel PM physico-chemical properties is made such as particulate ingredients, diameter and mass distributions, microstructures and oxidation behaviours. Diesel PM mainly contains soot, soluble organic fraction and ash whose percentages change with PM formation conditions such as engine load and speed, engine type and fuel type. Diameter distributions of diesel PM show a peak value around 100 nm that is caused by nucleation mode, while the mass distributions present double peaks around 40 and 300 nm, where the nucleation and accumulation mode particulates dominate, respectively. And, the researches of microstructures and oxidation behaviour make the foundation of decreasing PM emission and optimizing PM after-treatment device.