Development of the Diesel Exhaust Filtration Analysis System (DEFA)

The development of the Diesel Exhaust Filtration Analysis system (DEFA), which utilizes a rectangular wafer of the same substrate material as used in a full-scale Diesel Particulate Filter (DPF), is presented in this paper. Washcoat variations of the wafer substrate (bare, washcoat, and catalyzed washcoat) were available for testing. With this setup, the complications of flow and temperature distribution that arise in the full-scale DPF can be significantly minimized while critical parameters that affect the filtration performance can be fully controlled.

Cold flow experiments were performed to test the system's reliability, and determine the permeability of each wafer type. A Computational Fluid Dynamics (CFD) package was utilized to ensure the flow uniformity inside the filter holder during the cold flow test. The system was then exposed to several engine exhaust flow rates drawn by a sampling probe in the exhaust line to test the consistency of emissions measurements with other standardized techniques. Particulate Matter (PM) size distribution measurements from this new sampling system were found nearly identical to the measurements found with a commercial dilution system. Finally, the system was tested in a PM filtration condition. The DEFA proved to have the capability for performing PM filtration experiments at various filtration velocities.