A major breakthrough in the noise of DC fans

The noise of fixed fans is related to friction and airflow. The higher the fan speed, the greater the air volume and the greater the noise. In addition, the vibration of the fan itself can not be ignored. Of course, the natural vibration of high-quality fans will be very small, but the first two are difficult to overcome. To solve this problem, we can try to use larger fans. Under the same air volume, the operating noise of large fans at low speed should be less than that of small fans at high speed. Another factor that we usually ignore is the fan bearing. When the fan rotates at high speed, friction and collision will occur between the shaft and the bearing, so it is also the main noise source of the fixed fan.

The noise of DC fan comes from:

1. Vibration If the physical center of the rotor mass and the axis inertia center are not on the same axis when the fan rotor rotates, the rotor will be unbalanced. The linear distance between the physical mass center of the rotor and the shaft inertia center is called eccentricity. The unbalance of the rotor causes eccentricity. When the rotor rotates, the centrifugal force generates a force on the shaft bracket, and the vibration is transmitted to all parts of the machine through the basic path.

2. When the wind noise fan works, the blades periodically transmit the pulsating force of uneven airflow to the outlet, causing noise; On the other hand, due to the uneven pressure distribution of the blade and blade itself, the interference of surrounding gas and components in the process of rotation is also rotation noise; In addition, when the gas flows through the blade, it will produce turbulent boundary layer, vortex and vortex, which will cause the pressure distribution on the blade to fluctuate and generate vortex noise. The noise caused by these three reasons can be collectively referred to as "shear noise". Generally speaking, the shear noise of large air volume and pressure fans is also very high.

3. Incorrect wind noise sounds like pure wind noise, while incorrect sound is different. When the fan is running, if there are other sounds besides wind noise, it can be determined that the fan sound is incorrect. Collision caused by foreign matters or bearing deformation, incorrect assembly or looseness caused by uneven motor winding may cause abnormal noise.

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