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Analysis of the reasons for the cooling fan rotation stall

Time：2022-03-02Views：0

The working principle of the cooling fan is realized by energy conversion, namely: electrical energy → electromagnetic energy → mechanical energy → kinetic energy. The circuit principle is generally divided into various forms, and the performance of the cooling fan will be different depending on the circuit used.

In order to prevent unnecessary losses caused by the unexpected failure of the cooling fan, it is necessary to improve the design. In this way, the ability to be criticized is fundamentally eliminated and a fundamental change is achieved.

The formation of the rotating stall of the cooling fan: the structure and size of the impeller of the cooling fan are designed according to the rated air volume. When the cooling fan is working at a normal air volume, the direction of the gas entering the impeller is consistent with the installation angle of the blade air volume inlet, and the gas can be smoothly Entering the impeller, when the gas flow rate entering the impeller is less than the rated flow rate, the radial velocity of the gas entering the impeller decreases, and the direction angle of the relative velocity of the gas flow entering the impeller decreases, so it is inconsistent with the blade inlet installation angle. During the processing and installation of the blades of the cooling fan, due to various reasons, it is impossible for the blades to have exactly the same shape and installation angle. Therefore, when the operating conditions change and the flow direction deviates, the angle of attack at the inlet of each blade cannot be exactly the same. If the angle of attack at the inlet of a blade reaches a critical value, stall occurs on that blade first, instead of stalling on all blades at the same time, this phenomenon continues, causing the blockage area caused by stall to follow The impeller rotates in the opposite direction to propel, resulting in a phenomenon known as "rotational stall". When the cooling fan enters the unstable working condition area, one or several rotating stall areas will be generated in the impeller. Each time the blade passes through the stall area, it will be subjected to an exciting force, which can cause the blade to resonate. At this time, the dynamic stress of the blade increases, which may cause the blade to break. Therefore, from the absolute reference frame outside the impeller, the stall area still rotates along the rotation direction of the impeller, resulting in the mechanism of rotating stall. The pressure generated by the rotating stall on the impeller Fluctuation is the excitation force that excites the rotor to vibrate abnormally. The magnitude of the excitation force is related to the molecular weight of the gas, and they are proportional. The larger the molecular weight, the greater the excitation force.

Rotor rotation stall frequency: When the cooling fan is running normally, the direction of the impeller is consistent with the direction of the rotor. When the fluid direction is abnormal, the rotor will vibrate abnormally. So this is also the reason why the cooling fan rotates and stalls.

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Analysis of the reasons for the cooling fan rotation stall