Electrostatic Charging and Precipitation of Diesel Soot

Exhaust treatment systems consisting of new catalyst technologies and particulate filters are indispensable to meet increasingly stringent global regulations on limits particulate matter and nitrogen oxide (NOX) emissions from heavy-duty to light-duty diesel vehicles. Diesel particulate filter (DPF) has been established as a key technology in reducing diesel particulate emission. However, technological improvements to pressure drop, durability, and insufficient collection efficiency for nanoparticles are still required. Electrostatic precipitator (ESP) is another leading technology used in exhaust treatment, but it is currently limited to applications for stationary sources. In this paper, we have proven that concurrent use of ESP and DPF shows synergetic effects with very high collection efficiency and slower increase of the pressure drop. The number concentration of particles observed downstream of the combined system was 98% less compared with that of DPF only. At the same time, it was confirmed that increase in the pressure drop of DPF was slower. In this paper, the filter that was exposed to exhaust gas was observed by using scanning electron microscope. In addition, potential increase by charged particles on the surface of the filter was measured with a suction-type Faraday cage. The influence of the diesel particulate exerting on DPF by such an experiment was able to be clarified.