A diesel particulate filter technology developed in a German project funded by the European Regional Development Fund (ERDF) is set to clean up emissions from off-road construction vehicles.
Reduction of nitrogen oxide and particle emissions from diesel vehicles has been a major problem. Satisfactory solutions have been found for small and medium-sized cars to meet applicable emission standards. But filters for short-run specialist vehicles such as diggers and off-road construction machinery have been more difficult to produce economically.
Conventional diesel soot filters consist of cylindrical ceramic blocks crisscrossed by numerous channels. Such blocks cannot be made in one piece, so individual quadratic honeycomb segments are bonded together to form a large block. The bonds act as expansion joints that offset temperature stresses during operation – vital as a solid ceramic block would break apart. The drawback of these square honeycombs is that the bonded block has to be ground into a cylindrical shape at the end of production, wasting valuable material. What is more, this smooth finishing takes time and requires expensive machinery.
Sponsored by Saxony’s economics ministry with funding from the ERDF, developers at Fraunhofer IKTS developed a honeycomb structure with a different geometry. Rather than being rectangular, it takes an irregular four-cornered shape. This allows a wide variety of filter geometries to be created – even close-to-cylindrical. Grinding is no longer necessary.
An added advantage of this development is the altered geometry of the channels. Conventionally, the gas flows into the filter through four-sided channels. The Dresden researchers opted for a smaller, triangular cross-section. This enlarges the filter surface in the tiny channels. The triangular shape is also more stable, and the filter is less sensitive to lateral pressure.
“As far as the performance and quality of our new development is concerned, we can hold our own against anything on the market,” says IKTS project manager Jörg Adler. CDC is currently building its first plant near Dresden to produce some 40,000 filters a year using this technology for installation in construction machinery as an upgrade kit.
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