Characteristics of Aerodynamics and Noise for a Centrifugal Fan without Scroll Casing : Effects of Inducer

The characteristics of aerodynamics and noise for a centrifugal fan with inducer were investigated by comparison with the fan without inducer. The noise generated by these two kinds of fan consists of the discrete frequency noise and the turbulent noise. The discrete frequency noise can be controlled by some method. Therefore, the noise radiated from the centrifugal fan without scroll casing is mostly the turbulent noise. The noise level radiated from the fan with inducer is similar to that of without inducer. In relation to the aerodynamic characteristics, such as the pressure and the fan efficiency, the former is higher than the latter. Then the specific noise level of the former is lower than that of the latter over the wide flow rate. Therefore, the centrifugal fan with inducer is superior to that without inducer. We predicted the sound pressure level of the turbulent noise with the help of predicted width of wake and inlet relative velocity. The agreement between the predicted values and measured values of the sound pressure level agreed well in the range about ± 3 dB within the limits of this experiment