Effect of Number of Blades on Flow Field around Blades of Small Sirocco Fan

Abstract

Recently, fans have been used for cooling electric devices. A sirocco fan has been used in narrow places especially because it has the characteristics of high pressure and high flow rate. But the noise of a sirocco fan becomes loud, so it's very important to reduce the noise of a sirocco fan. So far, there were a lot of attempts to reduce the noise of the sirocco fan with large number of blades such as 40∼80 blades by performing experiments and numerical analysis. However, there is little knowledge for reducing the noise regarding the sirocco fan with small number of blades. There is the advantage that can reduce the production cost of the sirocco fan if it has small number of blades. The purpose of this study is to clarify the flow field around the blades of the small sirocco fan with small number of blades (Z=22, 11) by using LES compared with general number of blades (Z=40). As a result, it was clarified that the pressure fluctuation on the blade surface in the case of Z=22 was high compared with Z=40 and Z=11 at the maximum efficiency point. Because the spacing between the blades in the sirocco fan with Z=40 was smaller than Z=22, which restricted the flow separation on the suction side surface due to pressure fluctuation.