Modeling Aspects of Asymmetric Channel Configuration DPFs

Recently there has been a substantial interest in adopting asymmetric geometry design inside wall-flow diesel particular filters (DPFs) with larger inlet channel width to accommodate soot/ash accumulation and to reduce back pressure and thus to increase filter operation life time. The current work is sought to develop a model based approach to investigate various aspects of this strategy and to compare results with conventional channel design.

This paper describes assumptions and modeling methodologies used to evaluate the impact of asymmetries arising out of geometric design as well as due to ash deposition/accumulation on the overall pressure drop across the filter. Special attention is given to the challenges and strategies associated with flow and thermal solutions (during soot loading or regeneration) since transient ash accumulation causes a time varying reduction of effective wall-flow filtration length. A finite difference method with dynamically adjusted uniform grid for both fluid and solid phases has been found to be much more numerically stable than conventional approach with a fixed grid or using Runga-Kutta shooting method. These analyses are carried out within 1D representative channel level.

This study found that with identical total cross sectional flow area, asymmetric channel cell design with larger inlet channel width than outlet channel width has more ash storage capability and lower pressure drop across the filter. However, the asymmetric designs exhibit slightly higher back pressure than comparable conventional channel designs at the unloaded state. The proposed model is able to reproduce experimental results and trends. Consequently, the proposed model can be used for predicative studies if properly calibrated.