Micro-scale Simulations of Diesel Soot Oxidation

Mark  Stewart, PNNL

Rates of soot oxidation in DPFs depend upon local temperatures and concentrations of active gaseous species, including oxygen and NO2.
Active species produced at catalytic sites must diffuse to soot particle surfaces in order to take part in soot oxidation. Reaction kinetics at catalytic sites also depend upon local concentrations. Thus, global oxidation rates, which are critical metrics of DPF performance, may depend upon the complex interplay of three-dimensional temperature and concentration fields and upon the relative locations of soot and catalysts within the porous substrate microstructure. While challenges remain, progress has been made in micro-scale simulation of soot filtration using a relatively simple Eulerian/Lagrangian particle transport model. This type of simulation holds promise for elucidating the shapes and locations of soot deposits within the porous microstructure of DPF substrates. Soot oxidation and catalytic chemistry have also been incorporated into micro-scale models in an effort to better understand the role of transport phenomena in determining global oxidation rates.