Aerodynamic Noise Prediction of Automobile Engine Cooling Fan Noise

자동차 엔진 냉각홴의 공력 소음 예측에 관한 연구

Aerodynamic noise generated by automobile cooling fan is investigated. Automobile cooling fans radiate both discrete frequency noise as well as broadband noise. In the present work, the former is considered through free-wake panel method coupled with acoustic analogy fully considering the retarded time variation on the blade surface, while the latter is taken into account by three well-established broadband noise components. Experiments were performed to supplement necessary inputs as well as to provide the final comparison with the predicted noise spectrum. The predicted noise levels at blade passing frequencies agree well with the experimental data for the first few harmonics. Although the predicted broadband noise levels at higher frequencies fall below the experimental data due to the fundamental shortcomings of the utilized formulations, the analysis offers a detailed physical understanding of the fan noise generation processes.