Size-Dependent Filtration of Non-Loaded Particulate Traps

This work investigates the filtration efficiency of uncoated, commercial Diesel Particulate Filter (DPF) substrates of three porosities (55.8%, 61.1%, 65.0%) for particulate sizes representative of Gasoline Direct Injection (GDI) exhaust, and also refines a model suitable for predicting filtration efficiency for these non-loaded particulate traps. GDI produces lower concentrations of smaller particulates as compared to diesel combustion, which results in the absence of a soot-cake and yields changes in filtration behavior compared to diesel particulate. To produce a model that simulates the filtration efficiency of non-loaded particulate traps, an existing flow field model of DPF filtration was modified to better capture the fundamental physics of deep-bed filtration. The improved model includes additional sedimentation and thermophoretic modes of filtration and the soot-cake related filtration approximations were removed. Size-dependent particulate concentrations were measured using a Scanning Mobility Particle Sizer (SMPS), both upstream and downstream of the filters. By comparing upstream and downstream particle number concentrations, the particle size-dependent filtration efficiency of filter samples was determined. Experimental results were compared to model predictions, and showed excellent agreement.