Modelling of Filtration and Regeneration Processes in Diesel Particulate Traps

The reduction of exhaust particulate emissions from diesel vehicles is a great upcoming challenge. As a result of their harmful effects, new legislation on diesel vehicles has been introduced throughout the world specifying low emission-levels. Today, the use of diesel particulate filter (DPF) in addition to engine modifications is the favoured method to fulfil these criteria. The principle of a DPF is based on the accumulation of particles in the alternating open and closed channels of the filter. The pressure drop over the DPF increases with time. This increase is associated with the rise of fuel consumption. For this reason, the deposited filter cake must be occasionally regenerated. To minimise complex and expensive investigations on test benches, a mathematical model has been developed describing the loading and regeneration behaviour of a DPF. The model is integrated in a commercial CFD-Code using user-defined subroutines (UDS). The CFD-Code was used for the calculation of the fluid flow and the particle tracks of different kinds of particles (e.g. soot, additives) in a two-dimensional model of the DPF. Thus, the axial and radial structure of the deposited particles on the filter can be determined. In the UDS models are implemented to calculate the pressure loss, the separation efficiency and the regeneration behaviour. Comparing the simulation results with the results gained experimentally, it can be seen that both sets of data concur. Further development concerning the implementation of a subroutine to describe the long-term behaviour and transport of the deposited particles will be carried out.