2016年7月21日星期四

Centrifugal Fans---Forward Fan, Radial Fan, Backward Fan

Centrifugal Fans---Forward Fan, Radial Fan, Backward Fan

Centrifugal Fans---Forward Fan, Radial Fan, Backward Fan

The impeller is an important part of centrifugal fan,and its geometric shape, size, number of blades, and the manufacturing accuracy have great influence on centrifugal fan performance. Impeller static balance or balancing correction can ensure smooth rotation of centrifugal fan.

According to different direction of the blade outlet, the impellers are divided into forward, radial and backward impeller. 

Forward impeller blades incline to the impeller rotation direction; radial impeller blades are in the radial direction; backward impeller blades incline to the reverse impeller rotation direction. 

As for the same air flow and speed, forward impeller generates the maximum pressure,required the minimum impeller diameter, with low efficiency. On the contrary, backward impeller generates the minimum pressure,required the maximum impeller diameter, with high efficiency. The performance of radial fan are in between.  
forward curved impeller,radial impeller, backward curved impeller 


Straight blades is the most simple,while in order to have a suitable velocity distribution on blade surface, the centrifugal fan is always equipped with curved blades impeller. 
The front disc on fan impeller increases the impeller strength and reduces air leakage between the blades and casing. The impeller and frond disc are coupled by welding or riveting. Welding impellers have light weight, smooth flow channel.

During the centrifugal fan working, the motor drives the impeller rotate inside the volute casing, the air is sucked through impeller center by air inlet. 

Since the dynamic action of the blade on the gas, the air pressure and speed are improved,
Then under the centrifugal force, the air goes along the blade and is discharged from the air outlet. In general, centrifugal fan has one side air inlet with single suction impeller;
If the air flow is very large, centrifugal fan can have two side air inlet with double suction impeller, two back to back impellers. 
single suction and double suction blower

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