ΚΩΔ. 21.1.3 CN
How to select an axial fan blade.
There are typically four criteria used in the design of propeller blades or fan blades.
The material it is made from.
The number of blades.
The blade shape.
The blade pitch angle.
The material used in industrial propellers or fan blades is generally fabricated steel, cast or fabricated aluminum, fabricated stainless steel or other exotic metals. Plastic propellers have become common, but typically only in commercial fans. Fiberglass is also available for corrosion or chemicals resistance.
Number of Blades:
The number of fan blades is generally only limited by the size (diameter) of the propeller. Props will generally have as few as 2 blades, up to 16 blades. Some even have an odd number of blades such as 3, 5 or 7. The most common are 4 and 6 blade props.
The shape of the fan blade can be almost anything from square to round to rectangular. The corners are typically always rounded for greater efficiency and less noise. In most cases, large square blades are used to obtain the highest volume with the lowest noise.
Blade Pitch Angle:
The blade pitch angle is a critical factor in the overall performance of the propeller. In general, the greater the pitch angle, the slower the fan can turn. Some propellers or fan blades are made with adjustable blade pitch angles either set at the factory or adjustable while operating (in-flight adjustable).