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What is the hub ratio of an axial fan

The ratio of the diameter of the hub of the stainless steel axial flow fan to the outer diameter of the impeller is called the hub ratio. It is an important structural parameter. It has an impact on the pressure, flow and efficiency of the fan. Therefore, when the pressure, flow and speed of the ventilator are certain, the hub ratio cannot be selected arbitrarily.

From the value of the formula for calculating the hub ratio, the hub ratio is proportional to the total pressure of the axial fan and inversely proportional to the efficiency. Therefore, when the pressure or pressure coefficient of the axial flow fan is high, a larger hub ratio should be taken. However, if the hub ratio is too large, the blades are too short, and the gas flow loss in the blade channel increases, which deteriorates the performance of the fan, reduces the efficiency, and increases the axial size of the tail diffuser. It is also known that the hub ratio is inversely proportional to the circumferential speed of the impeller, and that a smaller hub ratio may be selected if a larger circumferential speed is selected. For fans with high wind pressure and small flow, a larger hub ratio can be used; for fans with low wind pressure and large flow, a smaller hub ratio can be used.

It should be noted that if the hub ratio is too small, the performance of the axial fan is also unfavorable, which will cause the separation of the airflow at the root of the blade.

When the stage scheme of the axial fan uses only a single impeller, a hub ratio of 0.3-0.45 is desirable. For the ventilator of other schemes, 0.15-0.7 is preferable, and some are lower than 0.5.

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