Improving Acoustic Performance of an Air Filter Box. TL Analysis and Device Optimization

The characteristics of the intake system affect both engine power output and gas-dynamic noise emissions. The latter is particularly true in downsized VVA engines, where a less effective attenuation of the pressure waves is realized, due to the intake line de-throttling at part-load. For this engine architecture, a refined air-box design is hence requested. In this work, the Transmission Loss (TL) of the intake air-box of a commercial VVA engine is numerically computed through a 3D FEM approach. Results are compared with experimental data, showing a very good correlation. The validated model is then coupled to an external optimizer (ModeFRONTIERTM) to increase the TL parameter in a prefixed frequency range. The improvement of the acoustic attenuation is attained through a shape deformation of the inner structure of the base device, taking into account constraints related to the device installation inside the engine bay. The shape deformation is realized by means of a dedicated software (SculptorTM), which allows to "morph" the base 3D mesh through a number of control points. In this way, the optimization procedure does not require the reformulation of the numerical mesh for the TL analysis of the modified device. At the end of the optimization loop, a significant improvement of the TL parameter is obtained for the optimized device.