Prediction and enhancement of the acoustic performance of a spark ignition engine intake air filter box

The present work has resulted in the development of numerical and experimental methodologies for prediction of the acoustic performance of an air filter box of an internal-combustion engine for automotive applications. With the aim of characterizing its fluid-dynamic behaviour and acoustic attenuation, the latter is first analysed as an isolated component. Typical performance parameters such as the discharge coefficient C-D, the pressure losses, the noise reduction and the transmission loss are experimentally and numerically evaluated. Different numerical approaches are considered, including complete three-dimensional computational fluid-dynamics analyses and finite element-boundary element procedures. The latter also take into account the interaction with the vibrating structure. The preliminary air-box design is also modified through the introduction of a column resonator and a Helmholtz resonator. Both the base and the modified system are finally coupled to the whole engine to estimate the gas-dynamic noise emitted by the intake system. The new architectural solutions of the intake system are characterized by improved acoustic performances and also preserve a good power output of the entire engine system. In each case the comparisons with experimental findings showed good correlation with the numerical predictions.