Noise Prediction of an Alternator Fan: Numerical Results and Experimental Validation

Fan is generally used for cooling of alternator and an undesirable side effect of these fans is generation of flow induced noise. With stricter regulations and growing importance on acoustic comfort in present day market, it's very important to address flow induced noise problems early in product development stage. With physical testing, it would not be possible to get information on source strengths thus, limiting its usage. Whereas simulation on the other hand would be able to provide source strengths, directivity pattern and source ranking. This paper focuses on numerical simulation of alternator's fan for prediction of air- borne noise. For this purpose, Computational Fluid Dynamics (CFD) based transient analysis is performed with high fidelity turbulence model using commercial software package, ANSYS Fluent. Ffowcs Williams and Hawkings (FW-H) model is used for modeling sound propagation. Overall sound pressure level for fan (source) is calculated at various receiver locations. Thus air induced fan noise, interaction of moving blades with surrounding air and the impact of the moving air on nearby static components is studied.