Study on the Fan Noise Reduction for Automotive Radiator Cooling Fans

In order to improve radiator fan noise, it is necessary to consider the system's Blade-Passing-Frequency (BPF), in addition to over-all noise reduction. BPF is unpleasant to vehicle passengers and is chiefly caused by the non-uniformity of upstream and downstream flows of the fan rotor. As a result, this noise is remarkably influenced by the layout of heat exchangers, shroud and engine room. Although the BPF noise has conventionally been evaluated experimentally, authors have recently begun considering BPF noise prior to trial. This has been accomplished by developing and applying the BPF Noise Prediction Technique, which consists of a Computational Fluid Dynamics (CFD) analysis and a sound wave propagation theory. This paper explains the prediction technique of the BPF noise, and also reports the results of its accuracy verification.