I don't know if you have carefully observed the fan blades of the electric fan. In fact, their structure is not a wild imagination, nor a creative creation. Most of the fan blades of electric fans have the same or similar shape: oblique, with a certain angle, and the number of fan blades is mainly 3, 5, and singular.
For a qualified electric fan, the air volume is critical, and this element is precisely determined by the spatial structure of the fan blade. It has been found through experiments that compared with the use of even number fan combinations such as 4 and 6, odd number fan combinations have more and more obvious advantages.
First of all, the odd-number blades are more stable and avoid shaking during operation. Even the number of blades makes it more difficult for the electric fan to keep balance, and it is also easy to cause resonance problems. When the blade is in frequent resonance, it may break because it cannot bear excessive vibration energy. For manufacturers, the subsequent after-sales maintenance problems are also quite difficult.
Relatively speaking, the odd number of blades can avoid this problem. The blades arranged in an asymmetric shape can effectively reduce noise and self-jitter.
Secondly, electric fans with odd blades are more environmentally friendly and meet the expectations of the public in terms of energy saving. Taking the electric fan with three blades as an example, its structure can form a reasonable power for each other in mechanics. That is to say, as long as two blades are in a potential energy state, they can drive another blade without dynamic potential energy to rotate together to save power and energy.
Therefore, we can find that most household electric fans have three blades. On the one hand, this design can ensure a large flow to meet people's cooling needs; On the other hand, it conforms to the principle of fluid mechanics and gives better play to the "power" of the electric fan.
At the same time, the problem of noise and unwarranted jitter is avoided, the loss of bearing is reduced, and the service life is improved. Therefore, not only the electric fan but also many blade mechanical systems have adopted this design concept. For example, some propeller helicopters also have an odd number of blades.
Of course, in real life, the statement that "all fans are odd" is not absolute.
For example, helicopters also have 2-blade and 4-blade propellers, and small electric fans also use a 4-blade design. Whether to use even blades in product design is more important to consider than the actual situation of the body.