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No through road for soot particles

Be it for making coffee, vacuuming the carpet or cleaning diesel exhaust fumes – filters are needed in many different places. However, finding the ideal design can be a costly and time-consuming process. New 3-D simulation software saves the trouble of building prototypes.

Diesel particulate filters are gradually making their way into series production – most car manufacturers build them into their diesel vehicles during the manufacturing process to keep emissions of fine dust to a minimum. But which filters are most efficient at extracting the noxious particles? How do the geometrical details of the filter materials affect the filter properties? Until now, researchers and developers have had to conduct a series of tests to answer questions like these: They build a prototype of each filter, which then has to prove its abilities in a practical test. This involves using a huge number of test filters – possibly as many as several hundred. New simulation software could in future significantly reduce the number of prototypes required, cutting the time and cost of development – and offer some powerful new features, as well: »Our FilterDict 3-D simulation program for the first time gives us full insight into the filter processes – information which often cannot be obtained from practical tests,« says simulation developer Dr. Stefan Rief of the Fraunhofer Institute for Industrial Mathematics ITWM in Kaiserslautern. »This allows us to simulate how fast and how far particles penetrate into the filter, for example – using any kind of filter material.« As its input variables, FilterDict requires the filter material model from the GeoDict micro-structure generator, various physical parameters, and the particle size distribution. Depending on the type of filter material, other parameters – such as the direction of the fibers in fibrous filters – may also be taken into account. On the basis of this information, the program calculates the path of the soot particles through the filter media – for each one of the billions of particles. »The simulation helps us to find out how much soot is deposited in which part of the filter. We optimize the design of the filter to achieve long regeneration intervals, low fuel consumption and a high engine rating,« Rief explains. The simulation program has already passed its first practical test. In an experiment conducted with fellow scientists at Bosch, the researchers examined two diesel particulate filters, with and without a fiber matrix, and compared the results with those of the simulations. Now Bosch and ITWM are extending their cooperation to simulate up to a hundred filters. Unsuitable types of filter can then be excluded from the outset – the researchers only build prototypes of filters that achieve satisfactory results in FilterDict. Only these are tested in the laboratory. The simulation program will be presented at the Filtech trade fair in Wiesbaden from February 27 to March 1 (Hall 1, Stand E7).


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