Operating Map for Regeneration of a Catalytic Diesel Particulate Filter

In the work presented in this paper, transient computational fluid dynamics-based simulations of soot combustion in a single-channel catalytic diesel particulate filter were run to investigate the combined effects of inlet gas velocity and catalyst activity on the dynamics of regeneration. From numerical results, the operating map of the filter was built in the plane maximum temperature versus time of regeneration. It has been found that all points fall within two zones of the map: a first zone of low temperature and long time of regeneration or, alternatively, a second zone of high temperature and short time of regeneration. The first zone corresponds to a regime of slow combustion (i.e., slow dynamics of regeneration with substantially uniform combustion), whereas the second zone corresponds to a regime of intense combustion (i.e., fast dynamics of regeneration that proceeds by a reaction front moving along the filter). At high inlet velocity, when the regime of intense combustion is established (at high catalyst activity), high temperatures involve the whole filter. At low inlet velocity, regardless of the catalyst activity, regeneration occurs according to the regime of intense combustion. However, an abrupt temperature rise is found only during the final stage of combustion of the residual cake accumulated close to the exit section of the filter, whereas most of the regeneration process occurs at lower temperatures. Thus, strategies able to prevent or mitigate such a burn-up phenomenon, which is well localized in both time and space, would be useful to allow reasonably fast regeneration under controlled temperature conditions.