Prediction of Pressure Drop in Diesel Particulate Filters Considering Ash Deposit and Partial Regenerations

Published investigations on the calculation of pressure drop of diesel particulate filters consider the contribution of substrate, soot, channel flow and inertial effects at the inlet and outlet of the channels. The model presented in this work considers further contributions as the oil ash and additive ash and their effects on the DPF pressure drop. It is shown that different types of ash deposit which are caused by different driving cycles and different regeneration modes, will result in a significantly different pressure drop even at the same total amount of ash. It will be shown that in the case without soot load the ash deposit at the wall will result in a higher pressure drop than the same amount of ash being deposited at the rear end of the channels. It is also shown that at a higher soot load this behaviour will be inverted. In addition this work considers a variable permeability of the soot layer varying with the soot load of the filter. Using the model described the effects of different ash distributions on the pressure drop are discussed. In a further point it is shown how the ash distribution affects the optimum filter design.

A further feature of the model is the calculation of the pressure drop of partially regenerated filters. It is shown that a local regeneration even in a small part of the filter will result in significant reduction in pressure drop.

In a further extension the pressure drop model is linked to CFD calculation data. The resulting system of equations is integrated over time. This allows the calculation of the evolution of soot and ash distribution over the cross section of the particulate filter.