Using CFD simulation as a tool to identify optimal operating conditions for regeneration of a catalytic diesel particulate filter

In the work presented in this paper, CFD-based simulations of the regeneration process of a catalytic diesel particulate filter were performed with the aim of identifying optimal operating conditions in terms of trade-off between time for regeneration and peak temperature. In the model, all the soot trapped inside the filter was assumed to be in contact with the catalyst. Numerical results have revealed that optimization can be achieved at low inlet gas velocity by taking advantage of the high sensitivity of the soot combustion dynamics to the availability of oxygen. In particular, optimal conditions have been identified when operating with highly active catalysts at sufficiently low inlet gas temperatures, so as to lie on the boundary between kinetics-limited regeneration and oxygen transport-limited regeneration. As catalyst activity is increased, this boundary progressively shifts towards lower inlet gas temperatures, resulting in lower peak temperatures and shorter times for filter regeneration. Under such conditions, in order to further speed up the process while still ensuring temperature control, it is essential to keep the filter adequately hot, thus minimizing the time required for the preheating phase, which may be a significant part (up to 65%) of the total time required for regeneration (preheating plus soot consumption).