Question about fan thrust direction on the shaft for centrifugal fan

Cheetos · Apr 4, 2024

I have a centrifugal fan directly coupled to the motor shaft. For centrifugal fan, since the air is pulled into the middle of the fan and is flung out due to centrifugal force, the thrust should be pushing against the motor shaft. Maybe I'm mistaken, because I've heard the other way around. The fan thrust is actually pulling on the motor shaft, rather than pushing. Can someone clarify this for me?

MintJulep · Apr 8, 2024

Draw a free body diagram of the fan wheel.

Here's a hint, from your post.

Cheetos said:
air is pulled into the middle of the fan

Compositepro · Apr 10, 2024

Some blower wheels are designed to draw air from both sides to prevent thrust. One sided blowers have suction force on one side and output pressure on the other side.

MTES93 · Apr 12, 2024

So the air inlet is opposite the motor, I assume (which is normal). And a centrifugal fan has a 90 degree inlet to outlet direction. The force (ie... mass) is coming directly at the shaft side of the motor. I think you are correct.

I'm assuming a SWSI fan. Single Width, Single Inlet Fan (means the motor is hogging up the other side). Compositepro did mention the other alternative, a double wide double inlet fan (DWDI). That was done to even out the forces you are talking about.

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Question about fan thrust direction on the shaft for centrifugal fan

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