US Egypt Cooperative Research: Simulation of Diesel Particulate Filters in Exhaust Systems

Project Summary Intellectual Merit A diesel particulate filter is an after-treatment device used to trap and capture soot from diesel engines. Due to increasingly stringent regulations, diesel particulate filters will be required in Europe and perhaps the United States as early as 2013. Though their primary purpose is to reduce exhaust pollutants, diesel particulate filters are also effective sound attenuation devices in exhaust systems. For one-dimensional acoustic analysis of exhaust systems it is usually assumed that only plane waves can propagate, which limits the frequency range of the simulation. This assumption is appropriate for applications like small automotive mufflers. However, the duct dimensions are large compared to the acoustic wavelength for large diesel engine silencers like those used in trucks, heavy equipment, ships and generator sets. More sophisticated approaches like the Finite (FEM) or Boundary Element Methods (BEM) are essential analysis tools in that case. The objective of this project is to refine and validate a BEM approach to predict the attenuation from exhaust systems including diesel particulate filters. In this newly developed model, the diesel particulate filter is modeled as a collection of one-dimensional wave guides. This assumption has been checked experimentally. Though the DPF itself is modeled one-dimensionally, the BEM technique allows for three-dimensional wave behavior up or down stream to the filter. The new model will be validated against measurements to be made by the Egyptian team at Ain Shams University (ASU). A parametric study will be conducted to provide guidance on the placement and selection of DPF units. Broader Impacts Currently, noise control engineers are solving these problems in a costly trial-and-error fashion experimentally. This wastes raw materials plus the solution to the noise problem is sub-optimal and costly. Consequently, a validated analysis tool which accurately predicts noise attenuation will meet a pressing need in these industries. Furthermore, the developed methodology should be appropriate for other after-treatment devices like catalytic converters.