Flow Distributions and Pressure Drops of Wall-Flow Diesel Particulate Filters

This paper describes an analytical and a numerical study of wall-flow filters with equilateral triangular channels. The flow fields of these filters are modeled analytically using a one-dimensional approach, and also simulated numerically using a three-dimensional approach. The flow distributions and pressure drops are presented and discussed in this paper. The results are also compared with experimental data. Among some interesting findings, re-circulation regions are observed in the areas near the filter entrance behind each front plug of outlet channels, and near the filter exit in front of and also behind each rear plug of inlet channels. Uneven distribution of wall flow velocity across the porous media is also observed. Pressure drop as a function of the Reynolds number, media permeability and inertial resistance coefficient, channel width, and channel length is discussed in this study. For wall flow velocity distributions which can be used to indicate the initial soot loading patterns, comparisons show good agreement between the analytical and the numerical approaches for flows closer to one-dimensional problems such as small channel width and large channel length. However, the analytical model is unable to predict the re-circulation and the two peaks of wall flow near the channel ends due to its one-dimensional limitation.

Although the performance of loaded filters is mainly of interest for engine applications, the study of clean filter characteristics will increase the understanding of initial flow distributions, particle movement, and filter performances. The information from this study will help optimize filter design and development.