IP Filter with DOC-Integrated DPF for an Advanced PM Aftertreatment System (1): A Preliminary Evaluation 2007-01-0924

Two or more aftertreatment systems will be required for diesel vehicles to reduce PM and NOx, simultaneously and achieve the same levels of exhaust emissions as gasoline vehicles. Thus, aftertreatment devices such as the DPF and DeNOx catalyst need to be compact and less restrictive to exhaust gas flow.

An IP Filter for removing particulate in exhaust gas has been developed to reduce both unit size and pressure drop and structured to integrate the DOC and DPF functions into one unit. A conventional wall-flow DPF has a cellular structure with either individual open-end or closed-end channels on both the inlet and outlet sides. The IP Filter has no plugs on the front end but has plugs at the interface of the DOC and DPF parts (internal plugs) in addition to the plugs at the rear end.

Several test IP Filters that were made of highly porous cordierite material were prepared for testing to evaluate their performance characteristics. Porosity of the substrate material was about 63 percent, and the cell density was 260 cells per square inch (12 mils). According to the test results, the conventional DPF used for production engines mostly traps soot near the plugs on the rear end. However, the IP Filter traps soot not only near the plugs at the rear end, but also near the internal plugs. As a result, the IP Filter can increase the maximum allowable soot loading and decrease pressure drop compared to a DPF currently mass-produced. In addition, particle size measurement results indicated higher filtration efficiency achieved by the IP Filter.

This paper reports the concept of the IP Filter, improvement of pressure drop with optimization of the internal-plug positions, the soot filtration mechanism, and the possibility of reducing the size of a particulate aftertreatment system using the IP Filter.