Investigation on the Properties of Fibrous Material in the Acoustic Calculation model of Automotive Exhaust System

Fibrous material is widely used in automotive silencers in order to dissipate high frequency noise components and attenuate the high-level pressure wave propagating from the cylinders. Its accurate acoustic model is in demand with a highly increased reliance on acoustic simulation of automotive exhaust systems. In this investigation, several empirical formulae and fibrous models in one-dimensional CFD codes are reviewed and their acoustic characteristics, e.g. propagation constants and characteristic impedance, are compared. Also, they are applied to some typical automotive silencers in order to check the validity of each model. It was found that some default fibrous models in commercial one-dimensional CFD codes were not satisfying. For the improvement of those results, DOE (Design of Experiment) and a commercial optimization tool were applied to find the optimal input values in their fibrous model.