Development of Low-temperature Aftertreatment of Diesel Exhaust Participates Using plasma Actions

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Diesel engines are widely used in transportation and other purposes, due to their low fuel cost and high energy efficiency. However, emission of particulates from exhausts, which mainly consist of various forms of carbon, has received particular attention because of health concern. Thus, there have been many attempts to aftertreatment them, but considerable difficulties exist to satisfy both requirements of sufficient aftertreatment and low initial/operating costs. This work has been undertaken to seek a possibility of exploiting the combination of barrier discharges with densifications using catalysts. Also, aftertreatments of SOF (Soluble Organic Fraction) are to be pursued. The main emphasis is to perform these functions at low pressure losses by utilizing a honeycomb structure, which has a large surface to volume ratio.The main results are summarized below.(1) The scheme of trapping of diesel particulates by a filter and their subsequent low temperature burning using barrier discharges has been demonstrated.(2) Absorption of NOX at low temperature and its release at above 300℃ using PZA (Pt-ZrO_2-Al_2O_3) were confirmed. The formation of honeycomb structure using the PZA was also demonstrated.(3) A barrier discharge was successfully formed between copper electrodes separated by mica sheet with PZA embedded honeycomb-shaped sheets inserted in the spaces. Thus, it has become possible to absorb and release NOX using discharge cycles.(4) Particulates were successfully collected toward bare electrodes between honeycomb-structured barrier discharge elements using the principle of electrostatic precipitation.Based on these results, the elements for the aftertreatment of diesel exhaust particulates have been demonstrated, and we intend to carry out the system test of the whole elements.