Analytic Solution for the Flow Distribution and Pressure Drop of Ceramic Partially-Plugged Wall Flow Diesel Particulate Filters 2015-01-1056

A 1-dimensional analytic solution has been developed to evaluate the pressure drop and filtration performance of ceramic wall-flow partial diesel particulate filters (PFs). An axially resolved mathematical model for the static pressure and velocity profiles prevailing inside wall-flow filters, with such unique plugging configurations, is being proposed for the first time. So far, the PF models that have been developed are either iterative/numerical in nature [1], or based on commercial CFD packages [7]. In comparison, an analytic solution approach is a transparent and computationally inexpensive tool that is capable of accurately predicting trends as well as, offering explanations to fundamental performance behavior. The simple mathematical expressions that have been obtained facilitate rational decision-making when designing partial filters, and could also reduce the complexity of OBD logic necessary to control onboard filter performance. The boundary conditions applicable to these partially-plugged filter configurations have been established before by our research group [1]. Removing few of the rear or frontal plugs from a standard wall-flow DPF reduces the (i) overall pressure drop (ΔP) across the filter, (ii) filtration efficiency (γ) of the DPF, and (iii) manufacturing cost. Partial filters have been deployed in diesel exhaust after-treatment systems for the emerging markets that follow Euro 4 emission regulations, especially in light-duty vehicle applications.

In the present work, the filtration efficiency and ΔP across PFs have been computed at various soot loads and flow rates for filter sizes typical of light-duty diesel applications. The effects of channel asymmetry, multi-staging of the PFs, and varying soot loads have been successfully captured in the proposed mathematical solution. The model predictions are in good agreement with experimental data obtained from both, single as well as multi-staged PF systems. The model results have also been demonstrated to be similar to simulations obtained from a numerical/iterative PF model reported in literature. [2].