Three-Dimension Deposited Soot Distribution Measurement in Silicon Carbide Diesel Particulate Filters by Dynamic Neutron Radiography

Exhaust emissions are well known to have adverse impacts on human health. Studies have demonstrated that there is an association between ambient particulate matter (PM) levels and various harmful cardiopulmonary conditions. Soot exhaust from diesel engines can be a significant contributor to airborne pollutants. A key component in PM level control for a diesel engine is a diesel particulate filter (DPF). This device traps soot while allowing other exhaust gases to pass unhindered. However, the performance of diesel particulate filters can change with increasing soot loadings and thus may require regeneration or replacement. Improved understanding of diesel particulate filters is dependent upon the knowledge of the actual soot loading and the soot distribution within the DPF. Neutron radiography (NR) has been identified as an effective means of non-destructively identifying hydrogen or carbon adsorbed in PM. Previous work has shown this technique to be relatively successful for cordierite type DPFs. In this feasibility study, the neutron radiography method is used to image a clean SiC DPF and a 3g/L soot loaded SiC DPF to measure the three-dimensional soot deposition profiles. The attenuation coefficients of SiC and soot are determined and quantitative soot loadings are determined. The resulting images show that soot deposition is generally uniform although some of the modules have higher soot deposition than others. The deposited soot distribution appears to be relatively uniform along the axial length of the SiC DPF with some variability. Radiography image of the deposited soot distribution in SiC DPFs compares well with deposited soot distribution in cordierite DPFs by the neutron radiography method.