Aeroacoustic Characteristics of Efficient Automotive Engine Cooling Fan Systems

Recent studies on automotive engine cooling fan systems carried out in partnership between LEMFI and Valeo have led to the definition of a range of efficient stator designs. It was shown that an adequate rotor-stator coupling could yield significant efficiency gains over the whole range of Valeo fans with diameters ranging from 280 mm to 460 mm. Efficiency gains ranging from 12 percentage points for the 350 mm fan diameter to 2 points for the 460 mm were estimated by using a simplified radial equilibrium design (SRE). These predictions have been verified experimentally by recent designs for various fan system diameters. The present study then describes a newly developed aeroacoustic test facility dedicated to automotive fan systems. The influence of the rotor-stator coupling is then shown by comparing the rotor alone and rotor-stator configurations, not only on the overall performances and velocity fields at the system outlet measured by a 5-hole probe, but also on the noise generated by the fan systems for various flow conditions. At the nominal flow rate, the efficient stators are shown to bring little or no extra noise if the number of stators and the rotor-distance are carefully chosen. At other flow rates, additional noise might be expected.