Multichannel Simulation of Soot Oxidation in Diesel Particulate Filters

In recent years advanced computational tools of Diesel Particulate Filter (DPF) regeneration have been developed to assist in the systematic and cost-effective optimization of next generation particulate trap systems. In the present study we employ an experimentally validated, state-of-the-art multichannel DPF simulator to study the regeneration process over the entire spatial domain of the filter. Particular attention is placed on identifying the effect of inlet cones and boundary conditions, filter can insulation and the dynamics of “hot spots” induced by localized external energy deposition. Comparison of the simulator output to experiment establishes its utility for describing the thermal history of the entire filter during regeneration. For effective regeneration it is recommended to maintain the filter can Nusselt number at less than 5. For the case studied, insulation of the inlet cones can lead to a gain of 30% in regeneration efficiency by eliminating radial temperature gradients at the inlet filter face. A model of ash transport and deposition in the filter channels has been derived, opening the door to the mechanistic description of filter aging by ash accumulation. In this way a number of variables and their effect on the soot oxidation potential of each regeneration technology can be assessed. In addition, filter thermo-mechanical behavior can be now analyzed by coupling the thermal history of the filter to a stress analysis code. In the present study, different filter technologies (catalyzed and NO₂ assisted), which have been assessed experimentally in the exhaust of a passenger car diesel engine, are analyzed comprehensively with the suite of the developed simulation tools. Based on these comparisons a ranking of filter material technologies with respect to their soot oxidation potential is obtained providing a means for their systematic improvement.