Abstract
In this study, the basic characteristics of the broad band noise (BBN) generated by an ultra-multi-blade sirocco fan were researched. In the impeller constituted by the forward curved blade such as sirocco fan, the flow between the blades is separated at the leading edge of the blade. In this case, it could be considered that the distribution of the pressure fluctuation made by the wake vortices in the share layer becomes a major factor for the sound pressure of the arbitrary observing point. As results of analyzed data of this experiment, it became clear that the characteristic of the fan noise was proportional to the index number K(=2.0〜3.0) of the flow rate coefficient. The predicted sound pressure of the BBN proposed in this study was proportional to the 2.6th power of the flow rate coefficient including the design point of the fan.
