A semi-empirical formulation is developed for predicting noise radiation from an engine cooling fan. This formulation is based on the mathematical model previously derived by the authors (Wu et al., 1997) for predicting noise spectra of axial flow fans running in a free field. The effects of shroud, radiator/condenser, and engine block on the ingested and discharged flow fields around the fan blades are taken into account by using certain shape functions. The computer model thus developed is used to predict the noise spectra from different fan assemblies under various working conditions, and the results thus obtained are compared with the measured data. Also, this model is used to calculate the overall sound pressure levels from dimensionally similar fans running under different working conditions, and the results are compared with those predicted by the fan laws currently used by engineers in the automotive industry.

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