A new technique for non-catalytic after-treatment system of diesel particulates

Abstract

Although diesel vehicles have features of low fuel consumption and high durability, stricter diesel emission standards have been set, and the after-treatment of exhaust gas is needed. In this study, as a potential catalyst-free continuous regeneration, the after-treatment system using a carbon-fiber filter was investigated, where diesel particulates are burned by electric heating. In experiments, the vehicle test was conducted to monitor the soot volume fraction and particle size in exhaust gas, in order to evaluate the proposed system. Additionally, the numerical simulation was performed to investigate the deposition and oxidation processes of soot particles in the system. Based on observation of the filter surface, soot adheres to the carbon-fibers, more than doubling their diameter. By equipping the filter, the backpressure increases to promote the soot production in exhaust gas. The backpressure with the filter is the same as that with the packing whose orifice diameter is 26 mm. When the performance of the filter was evaluated under the same pressure condition, the soot emission was greatly reduced. Since it is confirmed that the primary soot particle size in exhaust gas decreases by soot oxidation, most of soot particles are trapped and burned through the after-treatment system. Based on the simulation, soot oxidation is promoted by increasing the filter temperature. Continuous regeneration could be achieved by setting the filter temperature at 800 degrees centigrade or higher.