Filtration Efficiency and Pressure Drop Performance of Ceramic Partial Wall Flow Diesel Particulate Filters

A simple 1-dimensional filter model, with symmetric and asymmetric channels, has been developed to investigate the fundamental behavior and performance of ceramic partial diesel particulate filters (PFs). The governing equations of mass and momentum are similar to those of a full DPF [(7) under bar, (15) under bar]. A standard DPF with the plugs at its inlet face removed has been referred to as a 'rear-plugged PF' while, one with the plugs at the outlet face removed has been referred to as a 'frontplugged PF' in the present study. Removal of some of the plugs from a standard ceramic DPF reduces the (i) overall pressure drop (Delta P) across the filter, (ii) filtration efficiency (FE) of the DPF, and (iii) manufacturing cost. Partial filters stand a high chance of being deployed in diesel exhaust after-treatment systems for the emerging markets (Brazil, Russia, India, China) that follow Euro 4 emission regulations. The model has been used for predicting the pressure drop and filtration efficiency of the PF for a variety of situations and practical filter sizes. The effects of filter length, soot load, channel asymmetry, mass flow rate, wall permeability and multi-staging of filters on the pressure drop and filtration efficiency performance of the PF have been studied. An iterative approach to simulating a real-world non-uniform soot layer, instead of the uniform layer commonly assumed in DPF models, has been proposed. A standard DPF, front-plugged PF, and a rear-plugged PF have been modeled and the differences in their fundamental behavior are discussed. The model performance has been demonstrated to be reasonably similar to that of an existing 3-dimensional simulation. The filtration efficiency of and pressure drop across PFs have been predicted at various soot loads for filter sizes typical of light-duty diesel applications. A method to model DPFs with any fraction of the inlet/outlet faces plugged has been proposed.