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What are the noise reduction methods for plastic fans?
1. Enhance the aerodynamic load of the cascade and reduce the circumferential speed
For plastic fans, the choice of strong front blades and multi-blade impellers is beneficial to increase the aerodynamic load of the blade cascade. Under the premise of obtaining the same air volume and air pressure, the circumferential velocity of the inner hole of the impeller blade can significantly reduce the noise of the fan.
2. Reasonable snail-tongue clearance and snail-tongue radius
When the airflow moves relative to the blade, the velocity and pressure at the trailing edge of the blade are lower than those in the main flow area, which makes the distribution of airflow velocity and pressure after the cascade uneven. This uneven airflow is rotating. Because the airflow outlet of the moving blade has a volute tongue, the interaction between this unstable flow and the volute tongue will produce noise. The closer to the noise, the stronger the noise. Generally speaking, a larger front radius of the wind tongue can reduce the rotation noise and eddy current noise of the plastic fan.
3. Tilt of snail tongue
The periodic impulsive dynamics formed by the periodic impulsive rate of the impeller cascade airflow also causes the volute-lingual interaction to generate rotational noise. The magnitude of this noise is related to the intensity of the impulse power and the windward area of the vortex tongue. If the volute tongue is tilted, the effect area of the in-phase pulse power is small and the radiation noise is reduced.
4. Add turbulence equipment to the impeller inlet (outlet)
Adding turbulence equipment (metal mesh) at the inlet or outlet of the plastic fan impeller blade can immediately convert the laminar attachment layer on the back of the blade into a turbulent attachment layer, and delay the separation of the attachment layer on the back of the blade, even without separation. The trailing edge of the blade is installed on the Internet, and the airflow velocity and pressure gradient behind the network can be rapidly symmetrical. If the net is in the vortex area, the vortex area can be greatly reduced, which can further reduce the noise.
5. Set serrated structure beside the air inlet and inlet of the moving blade
The serrated structure is arranged beside the inlet and outlet of the moving blade, so that the laminar attachment layer on the blade can be converted into turbulent flow at an early stage, so as to avoid vortex separation caused by unstable waves in the laminar attachment layer, and reduce vortex separation and noise.
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