Effect of Different Operating Points on Flow Fields around Tongue and in Scroll Casing of Small Sirocco Fan with Small Number of Blades

Abstract

Sirocco fan has been used to cool interior of electronics in narrow place especially because it has characteristics of high pressure and high flow rate. But noise of sirocco fan becomes loud easily so it's very important to reduce noise of sirocco fan. So far, there were a lot of attempts to reduce noise of fan by performing experiments and numerical analysis. However, there is little knowledge regarding sirocco fan with small number of blades. There is advantage that can reduce production cost of sirocco fan if it has small number of blades. Purpose of this study is to clarify flow field around scroll tongue and in casing of small sirocco fan with small number of blades, using LES. It was made clear that scroll tongue had negative pressure in height of S/B=0.65 at maximum flow rate (Q=0.0321 m³/s). Because fast flow which is flowing out between blades once in this height tends to recirculate inside casing again from exit side. In all operating points, pressure fluctuation around scroll tongue is decreasing by reduction of flow rate, but position where pressure fluctuation becomes large is S/B=0.40 at scroll tongue.