Oxide Based Particulate Filters for Light-Duty Diesel Applications - Impact of the Filter Length on the Regeneration and Pressure Drop Behavior

Diesel particulate filters are becoming a standard for most light duty diesel applications designed for European EU5 and EU6 regulations. Oxide based filter materials are continuing to gain significant interest and have been in high volume serial application since 2005. Compared to carbide materials they show some unique properties. With respect to the design, the length of a filter is a key variable. Usually the prime design consideration is the desired filter volume. The diameter or frontal area is then usually defined by packaging constraints. Finally, the length is adapted. The paper provides experimental data on the impact this key design parameter has on the pressure drop and the thermal behavior under "worst case" regeneration conditions. A wide range of soot loads (from 4 g/dm(3) to 9 g/dm(3)) as well as filter lengths from 6" to 12" is considered and evaluated under comparable experimental conditions. The discussion is based on experimental data as well as numerical simulations with a 2D simulator. The simulator is shown to be in good agreement with the experimental observations. In general shorter filters are found to be of advantage. They provide for lower pressure drop and yield lower temperatures and gradients during worst case regeneration conditions. Data are provided that can help to estimate the impact of the filter length on the soot mass limit.