Study of Aeroacoustic Phenomenons at ducted Cooling Fans

Abstract

Germany's vehicle industry is greatly concerned with advancing their engines to make them environmentally compatible. This often leads to higher temperatures which have to be reduced by improved fans. However, less experience exists for high efficient fans of large diameters and power as used for trucks and busses. Therefore, two ducted full-scale fan models have been investigated to reduce noise and energy losses. Aerodynamic design parameters were planformm blade number, hub to tip ratio and the size of the slit. the experiments were conducted with a sucking wind tunnel and afterwards with the bus. The first model fan was designed such that the temperature is reduced by 3 degree and the noise by 1.3 dB(A) when mounted inside the bus. However, more than 6 dB(A) less noise was obtained with a second model due to an improved airfoil and a special localization inside the duct. The results indicate some important guidelines for the optimization of fans in the future.