A Numerical Investigation of the Combined Effects of Initial Temperature and Catalyst Activity on the Dynamics of Soot Combustion in a Catalytic Diesel Particulate Filter

In the work presented in this paper, the combined effects of initial temperature and catalyst activity on the regeneration dynamics of a catalytic diesel particulate filter (DPF) have been investigated. To this end, CFD-based simulations of soot combustion in a single-channel configuration were performed. In the model, all the soot trapped inside the filter was assumed to be in contact with the catalyst. The initial temperature of the filter was varied over a wide range independently of the inlet gas temperature, which was kept constant. Numerical results have shown that three main different behaviors arise depending on catalyst activity. At low catalyst activity, as the initial temperature is increased, an abrupt transition occurs from a regime of slow regeneration, characterized by long times (around 10 min) and low peak temperatures (~ 700 K), to a regime of fast regeneration, characterized by short times (< 60 s) and high peak temperatures (up to ~ 1100 K). At high catalyst activity, whatever the initial temperature, regeneration is always a fast process leading to peak temperatures ~ 1000 K. Interestingly, at intermediate catalyst activity, fast regeneration can be carried out with concomitant lower peak temperatures (~ 880 K), provided that the initial temperature does not exceed a threshold limit coinciding with the inlet gas temperature. Under such conditions, the best trade-off between time for regeneration and peak temperature is achieved with the initial temperature of the filter set equal to the inlet gas temperature. This optimal operating point can be further developed in a continuous functioning mode for catalytic DPFs, with regeneration performed during (and not after) filtration at the temperature conditions of the exhaust gas fed to the filter.