The aerodynamic noise is mainly generated by the rotati […]
The aerodynamic noise is mainly generated by the rotating rotor of the fan and the motor. When the diameter of the fan in the small and medium-sized motor is much larger than the diameter of the rotor, the fan noise is the main one. The Ms. is summarized and shared with you.
The noise of the fan increases with increasing flow, especially as the peripheral speed of the fan increases. In order to reduce the size of the motor and reduce the weight of the motor, it is always trying to increase the utilization of the effective material, which generally requires an increase in the flow rate of the fan. Therefore, there is a contradiction in improving the utilization rate of effective materials of the motor and reducing the requirement of ventilation noise. When designing, only the structural form and geometric size of each part of the fan and ventilation system can be reasonably selected so that both requirements can be properly taken care of. .
The motor's built-in fans are mainly radial centrifugal and axial flow. The axial fan and the rearward blade centrifugal fan produce less noise than the radial fan centrifugal fan. From a noise point of view in high speed motors, axial ventilation systems are better than radial ventilation systems.
When the fan uses equally spaced blades, if the fan interferes with one or several fixed obstacles, it will generate discrete frequency noise. In this case, changing the fan pitch blades to unequal pitch blades can significantly reduce noise. At the same time, this noise can also be reduced by increasing the gap between the outer circumference of the fan and the fixed obstacle. Generally, the gap δ should not be less than 10-15% of the outer diameter of the fan. In order to reduce fan loss and noise, the area at the inlet of the fan airflow should be smaller than the axial cross-sectional area of the fan at the inlet.