Influence of Obstacles on Flow Characteristics of Axial Flow Fan

The system environments of the axial flow fan are various. The axial flow fans are often used under unsuitable operatingcondition. Especially, the cases where the obstacles are distributed in upstream of the fan to downsize are increasing, inrecent high density design of equipment. An attempt is made to clarify the influence of the obstacle on the flow characteristics of axial-flow fans. In this study, a blockage disk is installed upstream of a test fan which is a typical cooling axial-flowfan. Blockage disks with various diameters are set up. The performance curves of axial-flow fan with blockage disks are measured. In addition, flow instabilities with a cell structure are demonstrated on typical condition. The main objects of thepresent study are : to evaluate the performance degradation when obstacles are installed in upstream of the test fan, toelucidate causes of positive slope for the performance characteristics curves and reverse flow, to clarify the generationmechanism of flow instabilities when the blockage disks which are larger than diameter of the test fan are installed.