Axial Flow Fan Broad-Band Noise Prediction and Application to Optimum Design

A broad-band noise prediction code based on the work of Carolus et al was written and incorporated into the low-pressure axial fan design program. For the convenience of design calculation, the turbulence statistics were determined by a semi-rational formula for fully-developed duct flow instead of the experiment. The code predicts 3 different forms of broad-band noise that were superimposed to calculate the total noise emission. The outputs include noise spectra, overall sound power and overall pressure level. In addition, Fukano´s model was also utilized for indicative comparison. The influence of the variation of the design parameters, including twisted power, hub ratio and solidity, on the fan noise characteristics was calculated and analyzed. It is indicated that the total sound pressure level is most sensitive to the flow relative velocity, while the chord length can be considered as a secondary cause.