Non-catalytic after-treatment for diesel particulates using carbon-fiber filter and experimental validation

Abstract

Recently, the stricter diesel emission standards have been setting and an after-treatment of exhaust gas is needed. In this study, as a potential non-catalytic system, the after-treatment using a carbon-fiber filter was investigated, where soot particulates are burned by an electric heater. In the vehicle tests, the experimental validation for our proposed system was conducted, where the soot volume fraction and particle size distribution in diesel exhaust gas were measured. Since the filter was attached to the exhaust pipe, the filter backpressure increased with higher soot emission. Thus, the performance of the filter was evaluated under the same pressure condition. It is confirmed that, the soot emission is greatly reduced by trapping the diesel soot. In addition, the particle number concentration is smaller, so that most of soot particulates are trapped and burned inside the filter. However, in the after-treatment process, particulates less than 30nm are newly formed. In experiments, the information on the soot oxidation process was limited, and the numerical simulation was performed to investigate temperature field and soot oxidation rate in the filter. It is found that the continuous regeneration is largely promoted by increasing the filter wall temperature. Hence, it is necessary to pay more attention on the effect of filter wall temperature on the particle size for more reduction of smaller particulates.