Noise Reduction for Automotive Radiator Cooling Fans

A3 - Tip Leakage Noise of Axial Fans

Engine cooling fans have long been recognized as one of the major noise sources in a vehicle. As the engine and other vehicle components are made quieter, the need to reduce fan noise has become more and more urgent. To reduce fan noise in a cost-effective manner, it is necessary to incorporate the component of noise reduction into an early design stage. In this paper a detailed experimental study on an automotive vehicle cooling system is presented.
The aim is to investigate the flow generated noise, characterize the heat exchanger damping properties and investigate the use of near-field noise control by so called micro-perforated plates (MPP) and quarter-wave resonators (QWR). Different concepts were tested ranging from exchanging the plastic shroud with micro-perforated plates and the use of quarter-wave resonators. For the tested standard automotive cooling fan system the MPP shroud gave a reduction in the range 1.5 to 4.5 dB(A) depending on the fan speed. Also the absorption on the back-side is significantly increased which can reduce the noise further. The near-field QWR concept is also promising and gives a reduction around 3 dB(A) at the operating points.