Filtration and Regeneration Performance of a Catalyzed Metal Foam Particulate Filter

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Abstract
The objective of this study is to present a particulate filter concept, based on a new porous material: INCOFOAM® HighTemp, a Ni-based superalloy foam. The paper examines the filtration and pressure drop characteristics as well as the regeneration performance of different filter configurations, based on experimental data and modeling. A number of different foam structures with variable pore characteristics are studied. The experimental testing covers flow and pressure drop behavior with air and exhaust gas, filtration efficiency measurements as function of particle size and regeneration rate measurements. The testing starts from mini-scale reactors and proceeds to real exhaust testing on the engine bench as well as vehicle tests on the chassis dynamometer and on-road. In parallel, a previously developed mathematical model is applied to study and understand the filtration and pressure drop mechanisms in the case of clean and soot loaded filters. Moreover, CFD studies are also employed to optimize the macroscopic structure of the metal foam filter. The results show that the foam filter has a potential for reaching a filtration efficiency of the order of 90% at an acceptably low pressure drop. This can be accomplished by a proper macroscopic design of the filter, as well as careful selection of the microscopic pore size parameters. For the case of catalyst coated foams, the regeneration rates measured at low temperatures are very high, suggesting a superior exploitation of the catalyst compared to conventional coated wall-flow filter concepts. Finally, dedicated experimental tests indicate that no blow-off of the accumulated soot is observed even during severe operating modes.

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