An empirical study of the dry soot filtration behavior of a metal foam filter on a particle number concentration basis

A metal foam filter is a porous metal DPF (Diesel Particulate Filter) that has different deposition characteristics to wall-flow-based filters. In this study, the soot particle deposition characteristics of a metal foam filter were examined using a 450 μm pore size filter. The pressure drop and the deposited mass were measured and filtration efficiency was derived by measuring the soot particle number concentration at the front and rear side the filter, using a scanning mobility particle sizer. The temperature range under which deposition occurred was set as 150 °C, 250 °C, and 400 °C. The total flow rate was about 30 sLPM (Standard liter per minute), and deposition time was 1 h. The mode diameter and number concentration of generated particles was 41 nm, 4.39 × 109/cm3; 128 nm, 3.12 × 109/cm3; and 190 nm, 9.24 × 108/cm3. The filtration efficiency was derived and expressed as a function of the particle diameter and the total number concentration. Mode diameters of 128 nm and 190 nm were selected for the quantitative measurement of number concentration. The results indicated that the filtration efficiency of a metal foam filter is determined predominantly by the particle mode diameter, but is also affected by the deposition temperature.