FAN Nozzle effect on the Centrifugal Fan

[Curious3110]

Hello All,
A very quick question to all. Could somebody explain me the the effect of the GAP on the performance of the blower in the image attached? How closly that gap needs to be controlled?
Blue is Air OUT, Green is AIR IN from the blower.

Also- Any learning material on the same is highly appreciated.

 

[LittleInch]

That's an odd looking fan, but that looks like the inlet seal between a higher pressure area and a lower pressure one.

The bigger the gap the worse the recirculating air and loss of efficiency.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

The impeller of the blower gives air a velocity. A restriction on the outlet of the blower converts some of this velocity to pressure. The more pressure that you have at the outlet of the blower, the more back-flow of air you will have through this gap, and the more important the size of the gap is. With no backpressure, the gap is unimportant. The shape of the entrance nozzle is important to reducing energy loss due to turbulence in the suction to the blower.

 

[Curious3110]

Thanks @LittleInch and @Compositepro.
So in nut shell the closer I maintain the gap between blower and nozzle better my efficiency will be.

 

[MintJulep]

It's common for the inlet bell to end inside the fan wheel.

See, for example, the operations and maintenance manual available here.

https://www.chicagoblower.com/Products/Airfoil-Fans/SQA-Square-Fans