Can we use the fan laws on fan with different blade width?

[Cheetos]

For the same fan OD and rpm, how can we estimate the fan performance (CFM, SP and BHP) when we vary the blade width, like 1" vs. 10"? Fan laws don't seem to account for that.

 

[LittleInch]

You would have thought flow was proportional to depth of blade until the depth of the blade started to interfere with the other blades.

But that's just an educated guess.

Fans come in many shapes, sizes and designs so I doubt there is a simple formula.

Testing would seem like a good idea.

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

 

[BrianPetersen]

There is no straightforward way of doing that.

 

[Cheetos]

I agree that testing is probably the best way to do this. For a simple straight bi-directional fan, I always assume there's a simpler way to estimate the performance. Maybe I'm just not that familiar with other companies, but when non-fan manufacturers create a fan, do they always send the design out to be tested? I can't imagine people send out a simple fan for testing. The cost of testing will probably be more than manufacturing one.

 

[hydtools]

I would expect a non-fan company would buy a fan rather than create one.

Ted

 

[Jacc]

This part of the forum is for Hydraulics and Pneumatics (aka Fluid Power), hydrostatic principle are used here.

Try this part of the forum instead, they do hydrodynamics: Pump engineering

 

[electricpete]

You just raised a question for me. Your question implies the pump laws apply for scaling by diameter and not blade width. And indeed if I look for the pump laws as described in some locations they show proportionalities involving diameter.

BUT I have seen derivations of pump laws from dimensional analysis (with some assumptions, like neglecting viscous effects). The only thing important about the diameter is that it is a characteristic length (where the word "length" just means something I'd measure in meters). That leads me to think that proper application of the pump laws should involve scaling ALL dimensions of the impeller by the same factor (not just scaling the diameter while leaving the other dimensions alone).

When we are trimming an impeller, then we know that physically the only thing we will change is the diameter without changing any other dimensions, and yet we still estimate the trimmed performance using the pump laws which (in my understanding) are based on scaling ALL dimensions by the same amount. Maybe it's just a convenient approximation which (for small changes like impeller trimming) results in small enough errors to be acceptable ? It's a bit of a puzzle to me.

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(2B)+(2B)' ?