Why do fan blades have more odd numbers?

Introduction Why do fan blades have more odd numbers? Even blades are symmetrical fan blades. In injection molding, if we use mold flow analysis software to discuss it, we can see that the fan blades with smooth sides on both sides are actually infinite.

Why do fan blades have more odd numbers?

Even blades are symmetrical fan blades. When injection molding, if we use mold flow analysis software to discuss it, we can see that it is actually impossible to inject saturated fan blades on both sides. at the same time, based on this factor, if you want to inject a complete fan blade, the fan blade on one side will be oversaturated (that is, the weight of the fan blades on both sides is different). odd number.

It is not that the more blades the better, but this must be taken into account depending on the air volume and pressure required. When there are more blades and the air volume is high, the fan noise will increase. the speed reaches the limit. If you want to increase the air volume, the only way is to change the angle of the fan blades or add blades, the number of fan blades is directly ment proportional to the volume of air. ?

The main thing is to choose an appropriate number of blades to achieve the heat dissipation goal. How to choose the appropriate air volume. I already answered this question

Because it is. is so asymmetrical! So it spins faster and smoother than even numbers! If it is an even number, the number of revolutions will definitely decrease and there will be no inertial force!

As we all know, the actual heat dissipation effect of the radiator largely depends on the design of the blade tilt angle, number of blades, etc. Among them, the number of leaves plays a very important role. ?

Usually, radiator manufacturers invariably adopt the method of increasing the number of blades in fan design to ensure a certain air volume and air pressure.

However, whatever the numberblades of an axial flow fan, its blade structure is mainly a combination of odd blades such as 7, 9 and 11. This is because odd blade combinations can bring more performance benefits than odd blade combinations of even blades. If the number of blades is designed to be an even number and arranged symmetrically, this will not only make it difficult to adjust the balance of the fan itself, but will also easily cause the fan to generate more resonance when operating at high speed. , which means that the blades cannot resist resonance for a long time. The resulting fatigue will eventually lead to blade breakage.

Therefore, the design of axial fans is mainly an asymmetrical odd-blade design. The same design philosophy is reflected in the design of electric fans or propeller-driven helicopters intended for everyday use.tidien.

To improve the motor fan blades, you can refer to the following aspects:

(1) About the blade material

The blade material should be light and hard. If conditions permit, it is best to use carbon fiber.

Pultruded fiberglass reinforced blades have good durability and corrosion resistance, resist acid, alkali and atmospheric corrosion. They have uniform material, high flexibility, consistent size and standard weight. , smooth surface and other characteristics. Mainly used for: wind turbines, wind water pumps, highway anti-glare signs.

Most rotor blades on large wind turbines are made of glass fiber reinforced plastic (GRP). Using carbon fiber or aramid as reinforcement is another option, but such blades are not economical for large wind turbines.Wood, epoxy wood or epoxy wood fiber composites are currently not used in rotor blades. The cinema market has emerged, although developments have already been noted in this area. Steel and aluminum alloys respectively present problems such as weight and metal fatigue. They are currently only used in small wind turbines.

(2) About the structure of the blades

The variables on the blades are:

1. Theoretically, the more there is on the blades, the better, which helps maximize the air in contact with the blades. But this is obviously not possible in practice. If it is too dense, the flow fields between the blades will interfere with each other. If they overlap, it won't be practical. If 3D printing is applied, it can greatly modify the existing design. ideas. If it is too thin, the efficiency will be low.

2. Transverse shape of the blade. EtaSince aircraft design and manufacturing has a long history, investments are large, the industry is developed, and there is a huge amount of aerodynamic data. Currently, aircraft airfoils are commonly used in blade airfoils, such as Göttingen airfoil, L-S airfoil and NACA series. , and high lift airfoil type, etc. Each type of airfoil has its own temperament and scope of application. Domestic and industrial fans do not have this problem. They are straight and can be turned using an iron plate.

3. Installation angle (the angle of inclination of the blade). Simply put, it's about how to maximize the conversion of air into axial flow as the fan blades rotate. For fan blades, the degree of inclination between the blade root and the diameter exmaximum is different, that is to say the angle of inclination of each ray is different.

4. Angle of deviation. That is, the bottom edge of the blade extends in a certain arc shape and does not radiate in a straight line. It can be understood here as the shape of the bottom edge, which can be straight or deviated at different angles; it can be arc-shaped with different curvatures, it can be elliptical, U-shaped or W-shaped; All sorts of strange things.

The most important ones would have to be these four. The complexity lies in the fact that all factors are interdependent. Even the first number of leaves does not determine which specific leaves are best. If the situation changes, everything changes. There are many situations for 2, 3 and 4, which can only be simplified during research, but simplification means giving up many possibilities, so there is a hugeroom for improvement in which form has the greatest advantage.

Also, the leaf tips were cut off, the dorsal fins were added, the teeth were opened at the bottom, etc., etc., etc., but they had to be thrown away.

The suction power of the motor is low. Generally, the power of the fan motor is small and the effect of changing fan blades is small. If the fan blade angle is changed manually and the change is not precise enough, it can easily cause an imbalance and cause the fan to run at a lower speed. However, it is still necessary to improve the fan blades, because it can improve the operating efficiency of the motor to a certain extent and reduce the waste of electricity.

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