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Filtration studies about the metal foam filters combined with electrostatic precipitation, which can be used as a new DPF device, have been performed. Filtration efficiency of the metal foam filter is significantly low because most particles are penetrated through the large filter-pores. However the efficiency was considerably improved by forming a high electric field on the filter surface. The pressure drop was not significantly increased by the particle deposition because the particles do not completely clog the filter pores.

Diesel burners have been used to regenerate diesel particulate filters (DPF) because of their simplicity in engine torque control and less oil dilution by fuel compared with the commonly used in-cylinder post fuel injection method. We previously developed a novel diesel burner using rotating plasma as an ignition source and found it to be effective in DPF regeneration. Here, we carry out in-depth studies on combustion efficiency of this plasma-ignited diesel burner and investigate the effects of influential factors such as plasma power, the amount of fresh air supplied, and O2 concentration in the exhaust gas on combustion characteristics of the burner. The obtained results show that fresh air supplied to the burner plays an important role in ignition and the early stage of combustion, and O2 concentration in the exhaust gas is identified as the most dominant factor for combustion efficiency.

A Diesel Particulate Filter (DPF) is an effective technology for reducing Particulate Matter (PM) emitted from diesel engines. In modern light duty diesel engines, DPF is regenerated by the post-fuel-injection method. In this method, the fuel is injected into the combustion chamber during the expansion stroke to produce heat to burn out the PM trapped in the DPF. However, this method also causes several problems, such as complicated engine torque control and oil dilution by fuel. In this study, a rotating plasma burner was developed for DPF regeneration as an alternative to the postfuel-injection method. Since it is important to reduce the electric energy consumption for plasma generation, which is directly related with electric noise and system cost, several design factors, such as the boosting voltage of transformers, electrode gaps, and plasma frequency were evaluated. A transformer with a low boosting voltage is desirable to ensure low electric noise.