Development of Large Size High Efficiency and Low Noise Fan Series

A lot of small fans with three-dimensional, wide chord length, forward swept figure, and/or shroud ring have been developed and manufactured by injection molding. When we see large size fans, they are still two-dimensional old-fashioned steel fans. Therefore, a new series of hybrid fans (plastic blades + steel hub) was developed to meet the requirement of low noise and high efficiency. Key technologies of high performance hybrid fans are blade contours that generate gradual load change and the best compromise among noise, efficiency and strength. Using CFD and FEM, several blade contours are investigated varying curvature distribution and blade turning angles. Further, the total cooling system was re-examined to increase the effect of new fans. One candidate is the attachment of noise-absorbing material around the fan and the other is selecting most appropriate shroud contour. Noise-absorbing material was found to be the most effective when it forms a bell mouth fan shroud and the fan itself also has the same outer shape. Test results showed significant noise attenuation and flow increase as well.