3D Unsteady Modelling of the Loading Process in a Diesel Engine PM-Filter

Particulate Matter (PM) filters are becoming a standard component of Diesel engines exhaust aftertreatment devices to comply with the forthcoming engine emission regulations. However, cost reduction and durability are still critical issues in particular for the integration of the PM-filter with other components of the after-treatment system (e.g. pre-turbo-catalyst, close-coupled-catalyst,PM-filter, SCR). To respect functional (available temperature and gas composition) and space restraints, very complex shapes may result from the design causing tortuous flow patterns and influencing the flow distribution into the PM-filter. Uneven soot distributions in the filter may cause a non-homogeneous development of filter regeneration, leading to failures, for example due to the occurrence of large temperature gradients during the oxidation of soot deposits. A detailed analysis of flow fields during the loading phase may represent an useful tool to design the filter and its integration into the exhaust system. In this work an effort for the development of a comprehensive model able to describe both large scale phenomena related to the complete exhaust system and local processes acting in the filter channels is presented. The model is based on a multilevel approach, built on FLUENT CFD solver, and it is capable of predicting the dynamic PM-loading 3D field into the filter. The model may be effectively used for the integration of the PM-filter into the after-treatment device, being able to capture the fundamental dynamic behavior of filtration process with reasonable computational efforts.