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In the last decades the continuously tightening limitations on pollutant emissions has led to an extensive adoption of after-treatment devices on the exhaust systems of modern internal combustion engines. While these devices are primarily introduced for reducing and controlling the emissions, they also play an important role influencing the wave motion inside the exhaust system and so affecting the acoustics and the performances of the engine. In this paper a novel approach is proposed for the modeling of two after-treatment devices: the catalyst and the Diesel Particulate Filter. The models are based on a fast quasi-3D approach, named 3Dcell, originally developed by the authors for the acoustic modeling of silencers. This approach allows to model the wave motion by solving the momentum equation along the three directions.

The acoustic simulation of internal combustion engine exhaust systems is an important aspect to meet customer expectations and legislation targets. One dimensional gas dynamic simulation tools are used for the calculation of the exhaust orifice noise in the early stages of the engine development process. This includes the prediction of the acoustic performance of individual components in the exhaust line. One common element used in exhaust systems to increase the acoustic damping is the plug flow muffler. This study looks at the prediction of acoustic performance of various plug mufflers at different flow velocities. These include a single plug muffler, a double plug muffler and an eccentric plug muffler with different porosities for the perforated sections. To this purpose a generic 3D cell approach was developed and applied.