Why Is The Number Of Blades in A Fan Blade Odd Rather Than Even?

The motor cooling fan is usually not used alone, but in conjunction with a radiator. Its components include motors, bearings, blades, casings (including fixing holes), power plugs, and wires.
Usually, the number of blades in a fan blade is odd rather than even, as this can reduce vibration and make the fan smoother. Due to the fact that the fan blades rotate at a certain angle, if the number of blades is even, they will form two opposite symmetrical groups, which will cause vibration during operation of the fan. If the number of blades is odd, they will not form a symmetrical group, which can reduce vibration and make the fan smoother. If the number of blades of a fan is even, forming a symmetrical arrangement, not only is the balance of the fan itself difficult to adjust, but the fan is also prone to more resonance during high-speed operation, leading to long-term resonance and fatigue of the blades, ultimately leading to blade fracture. In addition, it is difficult to achieve symmetrical point balance of double blades in the mold.
Working principle of Jiance electronic fan
From an energy-saving perspective, having an odd number of cooling fan blades can make the airflow generated during fan rotation more uniform. If it is an even number, there will be a "dead zone" during fan rotation, where the airflow will be slower and not conducive to heat dissipation. For example, a fan with three blades will save more energy than a fan with four blades. Because three blades can form an asymmetric and reasonable mechanical power, when one blade has no power potential energy, the other two blades are in a potential energy state, and the two blades with potential energy can easily drive a blade that has no potential energy temporarily, which saves both electricity and energy.
Moreover, having too many blades can shorten the chord length, increase the curvature of the blades, increase the reverse pressure gradient, and make the airflow easy to separate, leading to a decrease in efficiency. Therefore, increasing the number of blades is limited by the minimum blade chord length. So many designs are odd number blades with asymmetric axes. This principle is widely used in various fan blade designs, including some helicopter propellers.
So for fans with larger individual blades and independent installation of blades, the blades are generally 3-7. For fans with smaller integrated blades and requirements for silent effects, more blades will be used, such as fans with an external cooling base for laptops, which use nine or eleven blades.