Development of Silent Fan of a Hybrid between Disc Fan and Centrifugal Fan

Abstract

Recently, fan noise is severely restricted by ISO standard 14000, such as about 40 [dB(A)] noise level at night. Usually, small type fan includes centrifugal fan, axial flow fan, cross flow fan and so on. Although centrifugal fan is considered as the most silent one among them, further reduction of noise level is required. Fan noise is generated with the coherence between the blade and the tongue of the fan. Therefore fan noise can be reduced when the blade is removed or the blade is kept away from the tongue. In this study, two types of new idea fans were developed. The first is the multi disk friction type fan which was developed from a viewpoint of no blade fan. The second is the multi disk fan with blade, which we call hybrid fan. This is a combination of the multi disk fan and the centrifugal fan. In case of the hybrid fan, the blade was kept away from the tongue. Hybrid fan is expected to achieve low noise and high performance characteristics. Experimental apparatus was constructed. Fan performance and noise level were measured. Furthermore, power spectrum analysis was conducted. Multi disk fan with no blade showed the lowest noise level characteristics among the fans experimented. Hybrid fan shows much lower noise level than that of centrifugal fan. Desired noise level characteristics and performance characteristics can be obtained with hybrid fan.