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The current generation of particulate filters are effective within domestic diesel cars and are very good at reducing particulate emissions. However, a rising demand for improvements in filter designs is being demanded by governmental agencies especially with respect to their regeneration behavior during normal cyclic operating conditions out on the street. Parallel to this growing need to improve the increasing number of diesel filters in our cities, manufacturers have identified a need for a software prediction tool to assess the behavior of such filters in the early design phase. Ideally, they want to take into account the condition of a given car's exhaust, the mileage of the car, its filter size and its filter shape in a flow modeling tool.
Fluent Deutschland GmbH, based in Darmstadt , Germany , and Eberspächer have generated a combined 3D/1D modeling tool, using the popular FLUENT CFD code and MATLAB from Mathworks Inc., to calculate diesel filter soot distribution, pressure, and regeneration under any operating condition. Eberspächer's MATLAB based diesel filter tool simulates 1D channels during loading and regeneration and then because it is closely coupled with FLUENT's 3D CFD flow modeling datasets it can simulate a complete diesel filter's behavior for local particulate buildup and regeneration over time. This modelling approach can allow for the effects of non-uniform filter inlet flow conditions in a particular car to be simulated thus permitting an assessment of the soot distribution inside. A custom filter design that prevents damaging soot build up can then be determined in the computer before it is manufactured.
A further requirement to a filter's design that the software tool provides is the ability to predict the local soot oxidation as the filter is exposed to regeneration under different driving conditions. The filter's loading behavior after partial regeneration when it has experienced different types of driving cycles is of special interest to manufacturers, and that too can be predicted using the tool. This diesel filter design tool can simulate both a clean filter as well as a loaded filter after the car experiences high mileage. In the latter case effects like ash deposits (resulting both from oil ash or ash from fuel additives) can be considered.
Dr. Gerd Gaiser, Director Pre-Development Exhaust Technology of Eberspächer, comments on this tool, "The software resulting from this cooperation allows us to design optimum filter geometries with regard to soot loading distributions and the avoidance of partial regenerations even under difficult design conditions. The ability to predict the local regeneration behavior and thereby avoid excessive local temperatures is a major requirement for the design of diesel filters consisting of less expensive but more temperature sensitive material."
Werner Seibert, Global Automotive Segment Manager for Fluent Inc., sees this modeling tool as a significant step forward. "Our collaboration with Eberspächer has produced a unique design methodology that I believe will transform the design process for complex automotive diesel filters. The net effect will be a new tool to improve filter design and thereby reduce particulate emissions at the early design stage which should lead to an improved environment for everyone."
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