Abstract
Keywords:Diesel aftertreatment system, Non-thermal plasma, Dielectric barrier discharge, Particulate matter, Transient modal analysis
In order to successively remove particulate matter (PM) from exhaust emissions of diesel engines, a non-thermal plasma (NTP) system is under development for practical use. In the NTP system, a dielectric barrier discharge (DBD) reactor driven by highvoltage pulses has been mainly investigated.
A newly designed electrode has been developed in order to remove PM efficiently in a transient mode that the volume of exhaust gases and amounts of PM change frequently. This electrode shows wide discharge space and has a function of temporary trap, different from partial or full trap such as a diesel particulate filter (DPF). PM removal properties of the plasma reactor with developed electrodes were evaluated in the Japanese JC08 test mode using a virtual vehicle simulator system with 2-cycle diesel engine (1.2 L). It was confirmed that PM emission was reduced to 0.038 g/km below the Japanese post new long-term emission regulation (JP 2009) or Euro5 level by the plasma reactor using discharge power of only 210 W. The plasma reactor showed high removal capability for soot which is not easily oxidized with catalytic reaction. PM removal by using the plasma reactor was achieved effectively even under the low temperature of below 170 °C. Also, the plasma reactor showed lower pressure drop below 3.2 kPa during JC08 mode by comparison with conventional DPF systems.
This NTP system without precious metals such as platinum group metals (PGM) is expected to be the promising technology for diesel emission control, and to be one of the solutions for not only emission control but also PGM resources problems.