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fan torque vs speed general relationship

fan torque vs speed general relationship

fan torque vs speed general relationship

(OP)
I was under the impression that the torque-speed characteristic for fans is similar to centrifugal pumps pumps, generally torque ~ speed^2... (not exact but pretty close).

The attached excerpt from "COMPUTER ANALYSIS OF POWER SYSTEMS"
by Arrillaga and Arnold suggests that a linear relationship (torque ~ speed) is generally more appropriate for fans.

Is there any basis for that? Or are they out to lunch?

=====================================
(2B)+(2B)'  ?

RE: fan torque vs speed general relationship

(OP)
Both the 1st and 3rd links say that for constant impeller or wheel diameter: Power~N^3 which implies Torque~N^2

The middle link has:
(W1/W2) = (D1/D2)^5  (N1/N2)^3  (ρ1/ρ2)
where W1/W2 is power ratio D1/D2=1 if we're fixing the wheel diameter.   IF the system operates close to atmospheric pressure with maybe 0.15 psi or less dp, then the absolute pressure varies by less than 1% and rho is for all purposes constant.  I think most ventilation and cooling type fans do not fall into this category.... ok to treat density as constant.  Then again power proportional to speed^3 and torque proportional to speed^2

 

=====================================
(2B)+(2B)'  ?

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