Comparisons of Unit-Cell Filtration Models and Their Applications in Filtration Performance Predictions

Yujun  Wang, Cummins

As the particulate matter (PM) emission regulations become more stringent world widely, especially with the enforcement of particle number regulations, the initial and loaded filter filtration efficiencies are vital for internal combustion engine to meet low emission limits. Unit cell filtration models have been widely used, and have evolved into multiple variations such as cylindrical cell model, spherical cell model, constricted tube model, and so on.  In the present study, different types of unit cell models and their upgraded versions considering pore size distribution were built to evaluate their applications in engine particulate filters. This study summarizes the main input parameters for these unit cell models, and evaluates the difficulties in measuring/estimating these parameters (i.e., tortuosity and pore size distribution). Furthermore, the sensitivity of the filtration efficiency to these input parameters have been analyzed. And the analysis quantifies the resulting uncertainty caused by inaccurate measurements of key input parameters. Then, for a given filter, the predicted filtration efficiencies from unit cell models are compared against experimental data under multiple operating conditions. This study compares the tuning work needed for each type cell model, and summarizes the advantages and disadvantages of cell models. More importantly, current study demonstrates the necessity of considering pore size distribution to have more accurate filtration efficiency predictions.