Modeling of silencers for internal combustion engines: 1D-3D coupling, network of 1D elements and a generic 3D cell approach

Increasing demands on the capabilities of engine simulation and the ability to accurately predict both performance and acoustics has lead to the development of multiple approaches, ranging from fully 3D to simplified 1D models. In this work it will be described the development and application of hybrid 1D-3D approaches and an innovative one based on the 3D cell element. This is designed to model the acoustics of intake and exhaust system components used in internal combustion engines. Models of components are built using a network or grid of 3D cells based primarily on the geometry of the system. This means that these models can be built without fundamental knowledge of acoustically equivalent systems making their range of application larger as well as making them simpler to construct. Due to the 3D nature of these models it is also possible to predict higher order modes and improve the accuracy of models at high frequencies compared to conventional plane wave approaches. The solution of the 3D cell is based on a staggered grid approach. The equations of mass and energy are solved at cell centers and the momentum equation at cell connections or boundaries. The 3D acoustic cell has been validated by comparing the predicted transmission loss to measured values for a number of standard configurations found in intake and exhaust systems. These include expansion and reverse flow chambers. The transmission loss has been measured using the two load technique.