31-08-2017, 12:04 PM
An axial fan is a type of compressor that increases the pressure of the air flowing through it. The blades of the axial flow fans force the air to move parallel to the axis around which the blades rotate. In other words, the flow is axially inward and axially outward, linearly, hence its name. The design priorities in an axial fan revolve around the propeller design that creates the pressure difference and hence the suction force that retains the flow through the fan. The main components that must be studied in the design of the propeller include the number of blades and the design of each blade. Applications include propellers in airplanes, helicopters, hovercraft, boats and hydroplanes. They are also used in wind tunnels and cooling towers. If the propeller is exerting propulsion, then efficiency is the only parameter of interest and other parameters such as required power and flow are considered of no interest. In case the propeller is used as a fan, the parameters of interest include power, flow, pressure increase and efficiency.
An axial fan consists of far fewer blades, ie two to six, compared to duct fans. Axial fans operate at a specific high speed, ie a high flow rate and a low head, and therefore the addition of more blades will limit the high flow rate required for their operation. Because of the smaller number of blades, they can not impose their geometry on the flow, making the rotor geometry and the input and output velocity triangles meaningless. In addition, the blades are made very long with sections of blades that vary along the radius.
An axial fan consists of far fewer blades, ie two to six, compared to duct fans. Axial fans operate at a specific high speed, ie a high flow rate and a low head, and therefore the addition of more blades will limit the high flow rate required for their operation. Because of the smaller number of blades, they can not impose their geometry on the flow, making the rotor geometry and the input and output velocity triangles meaningless. In addition, the blades are made very long with sections of blades that vary along the radius.