Ash inside a honeycomb-configured diesel particulate filter (DPF) inlet channel accumulates both as a cake layer along the channel walls and as a “plug” towards the back of the channel. Experimental studies of DPF ash distribution have shown both an axial variation of deposits along channels and accumulation towards the end plugs. This study evaluates the sensitivity of DPF pressure drop on ash axial distribution and the potential to reduce flow restrictions by controlling and optimizing the spatial distribution of ash inside DPF channels.
A computational model has been used in conjunction with experimental data to illustrate the sensitivity of ash spatial distribution on DPF performance. The classical constant-thickness DPF one-dimensional models have substantially been updated to include layer thickness axial variations.
Material properties, such as ash characteristics, are provided by recent experiments at the authors' laboratory. The experiments tested six types of lubricant formulations with different additives and determined their effects on DPF performance. By analyzing the DPF pressure-drop variations with ash loading, the ash cake-layer permeability and the substrate wall permeability can be estimated using the information contained in the DPF pressure drop data. With these experimental ash properties data, simulations are conducted to study the ash distribution effects.
The simulation results show that DPF pressure drop is not very sensitive to the specific shape of the cake-layer profile along the filter channel. However, accumulating ash along the channel walls versus accumulating ash at the end plug does make noticeable differences. Hence detailed dimensional analyses have been conducted to illustrate the subtle effects of the controlling physical parameters.