Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with experimental investigation is presented. Patented hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been studied along with recent patents. An experimental investigation of the interaction of two flows with the flow around hollow airfoil NACA series in a low-speed wind tunnel was studied. The determination of flow structure on the hollow airfoil was performed with computer-aided visualization. With the introduction of the internal flow and interaction with the external flow, a reduction of circulation effects on the fan hollow blade was achieved. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. Aerodynamic characteristic of the axial fan reached higher degree of pressure difference and efficiency through the entire fan working conditions.
Keywords: Axial fan, hollow blade, aerodynamic characteristic, wind tunnel and computer-aided visualization
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