Taking the pollution out of diesel
Fine particles generated during the high-temperature combustion that takes place inside a diesel engine present a health hazard. In the 1990s, engineers began adding special filters to the exhaust systems of diesel-powered vehicles to remove these particles. In the first decade of this century, the European Union if funding research aimed at improving filter technology. Centro Ricerche Fiat tinkered with different filter designs hoping to boost efficiency without sacrificing flow characteristics or filter regeneration. A new prototype was created during the STYFF-DEXA project. Lateral slits in the ceramic foam filters create increased filter surface area without increasing filter volume. This increases particle removal without slowing down the exhaust flow. The prototype is comprised of seven modular foam stacks, each of which holds up to fifteen filters. This allows for the necessary degree of flexibility. Fluid dynamics simulation tools were employed to identify and avoid any possible flow irregularities that might impair performance. Initial laboratory tests indicated performance improvements over the wall-flow type filters currently in use. These were followed by tests with a Euro IV compliant 1.9-liter diesel engine, which revealed excellent filter regeneration capabilities. A significant pressure drop was observed during high engine output, but the researchers at Centro Ricerche Fiat believe an alternative filter design based on drilled holes could resolve this issue. They are also investigating the use of catalysers to improve performance. These developments will help auto manufacturers meet the next generation (Euro V) emissions standards.
