The velocity field downstream of an axial fan was measured using probe 55 P 51 of a Hot Wire Anemometer to investigate characteristic of the flow. Flat blades were varied in length of blade\u27s span and angle of attack. The length of blade\u27s span was varied at 0.3, 0.5, 0.75 and 1 times of 450 mm, at various angles of attack at 50, 100 and 150, while it was operated at constant speed of 610 rpm. The measurement was conducted at vertical distances 210, 360, 510 and 660 mm from the fan.
The investigation was focused on the mean velocity in axial and tangential directions at measurement position 210 mm. Properties of the flow were computed based on integration of Reynolds momentum and continuity equations for determining flux of axial and angular momentum. The performance of the axial fan was determined by comparing values of torque, thrust, volume rate and consumed power. The swirling number of the flow was also calculated as a consideration to determine performance of the axial fan.
Results indicate that operating the axial fan in variation blade\u27s span have significant effect to the value of axial and tangential mean velocities and the area offlow, meanwhile variation in angle of attack just influence to the value of axial and tangential mean velocities. Increasing of blade\u27s span at constant angle of attack 10° increases volume rate, torque, and thrust of flow and consumed power of the fan. Investigation of increasing angle of attack at span blade 450 mm also increases those values. Span blade 450 mm at angle of attack 15° have a highest performance and consumed power. It can be shown also that swirling increase with respect to increase of angle of attack.
Keywords: velocity field downstream axial flow fan, span\u27s blade, angle of attac
