Multi-Instrumental Assessment of Diesel Particulate Filters

As different Diesel Particulate Filter (DPF) designs and media are becoming widely adopted, research efforts in the characterization of their influence on particle emissions intensify. In the present work the influence of a Diesel Oxidation Catalyst (DOC) and five different Diesel Particulate Filters (DPFs) under steady state and transient engine operating conditions on the particulate and gaseous emissions of a common-rail diesel engine are studied. An array of particle measuring instrumentation is employed, in which all instruments simultaneously measure from the engine exhaust. Each instrument measures a different characteristic/metric of the diesel particles (mobility size distribution, aerodynamic size distribution, total number, total surface, active surface, etc.) and their combination assists in building a complete characterization of the particle emissions at various measurement locations: engine-out, DOC-out and DPF-out. The results provide useful guidelines for the selection of various filter media and measuring methodologies. In this paper, among other themes, the inter-comparison of SMPS and EEPS measurements is discussed since these instruments exhibit small but systematic differences. In addition, the evolution of the collection efficiency of each filter medium (evaluated with respect to each of the characteristic metrics measured by each instrument) under steady state and transient engine operation conditions, as a function of soot load of the filter and the particle emissions during filter regeneration is investigated.