Joke: Why does the fan have three leaves?

The reason why an electric fan has three leaves:

(1) This is the optimal result under the comprehensive consideration and action of many factors, among which the main factor is the optimization and balance between aerodynamic efficiency and structural complexity, which determines the important index of manufacturing and maintenance costs.

(2) The specific working conditions of the impeller include the tip wind speed ratio \ λ (the ratio of the tip linear speed to the wind speed) and the blade pitch angle \ θ. The efficiency of the impeller has an optimal value. Historically, the optimal c_{PR} of modern three-leaf fans has reached the highest level, about 0.48~0.49.

(3) Blade fan has high torque conversion efficiency and is suitable for various wind speeds. (3) The blade fan has a good torque conversion efficiency at a low tip wind speed ratio λ, which means that the impeller can generate enough torque to drive itself and the whole rotating chain at a low wind speed.