Souichi Sasaki

Flow Characteristics in Scroll Casing of Sirocco Fan

The sirocco fan is advanced in compact with high pressure and large flow rate. But the efficiency of it is relatively low. One of the reasons is the complex and large flow in the scroll casing. Then it is expected to clear the influence of the geometry of the casing to the fan performance and to make compact the fan without reduce the performance. This paper presents the flow characteristics in the scroll casing for four types geometries. The flow characteristics are examined in experiments and numerical simulations. The net flow out of the impeller is biased to the hub side and the circulating flow is generated near the shroud in the scroll casing. The pressure is large in the hub side and gradually decreased toward to the shroud. The pressure distributions are different for each scroll casing until the end of the scroll, and then it is emerged the pressure drop near the end of scroll casing. After it, there are a rapid pressure raise in all types. The pressure out of the fan becomes almost the same in a...

103 Relationship between Aeolian tone and Wake Vortex from Inclined Flat Blade : Characteristics of Vortex Shedding in Spanwise Direction

The three dimensional structure of the wake vortex was investigated in relating to the aeolian tone from the inclined blade. It was pointed out that the aeolian tone is largest not at zero, but at ten degree of the inclined angle. The correlation length of the wake vortex in span becomes large at small inclined angles. The large scale structures of the wake vortex are generated in zero and ten degree of inclined angle. The shape of the structure is influenced with the span-wise velocity in the dead air region. There are small scale spots of the pressure fluctuation at the trailing edge. The spots are interacted each other and make a large cluster of the pressure fluctuation. It is proposed that the scale of it is decided by the timing of the wake vortex formation. And the shape of the wake vortex structure is closely related with the scale of it. The correlation length of the wake vortex is calculated from the shape of the structure. The estimation of aeolian tone by using the length with Fukanos model is well coincided to experiments.