Mixed 3D numerical approach on the exhaust radiated noise prediction

The paper describes a comparative analysis between numerical and experimental study on an exhaust system of a single-cylinder diesel engine. Previous experimental investigations concerned the gas-borne noise characterization of the engine and an experimental campaign on the evaluation of the transmission loss factor of the tested exhaust system. Contemporarily, a 3D numerical model of the system has been created in order to obtain a validate tool able to predict the radiated noise in the environment. The created model represents a mixed FEM-BEM application. In addition, a CFD model has been created in order to better simulate the fluid flow pulsation and to calculate the flow interactions with the external skin of the muffler, too, in terms of structural vibrations. Based upon this information, the radiated power has been evaluated on the FEM-BEM 3D model and then compared with the experimental data. The results have shown a good numerical approach able to simulate the fluid flow pulsation and the acoustic-radiated noise. Future interventions could concern the possibility to improve the muffler design in order to reduce not only the exhaust-radiated noise but also its structural vibrations.