The noise prediction of automotive axial fan with different blade sweep angle using the unsteady CFD analysis

Abstract

This study was conducted on automotive axial fans with the three types of swept blades: forward, backward and straight, using the three dimensional unsteady CFD analysis. The acoustic analogy by the Ffowcs Williams-Hawkings was used to predict the sound propagation in the far-field. The unsteady RANS and SST turbulence models were used for the CFD analysis. The predicted results were validated with the following experiments. The three fans with different sweep angles showed quite different performance and noise levels. Especially the overall noise of the forward swept fan showed 4 to 5 dB(A) which was lower than the straight blade and backward swept fans' at the same rotation speed. The main purpose of this study is to explain what causes the differences in performance and noise level in terms of flow characteristics, and how the sweep angle of blade affects the overall fan noise level. The corresponding setup in the CFD analysis and experiments include just cooling fans and shroud without heat exchangers.