How does the number of blades in a fan affect the flux of air? I read that 3 blades are the best option but some companies uses more blades because there's a misconception among people that more blades generates more air.
$\begingroup$
$\endgroup$
1
-
1$\begingroup$ What is your fan trying to do? Does it try to move air without (significant) pressure difference or does it try to build pressure? Those are completely different applications requiring different solutions. I believe that fewer blades are better for the first case, but fan compressors have to be built with a large number of blades, as the case of gas turbines shows. $\endgroup$– CuriousOneSep 6, 2014 at 14:51
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
3 blades would be indeed close to optimum for power efficiency and require less material during manufacturing.
But typical engineering goal for fans is different: maximum performance / noise. More blades $\implies$ slower rotation for same performance $\implies$ less turbulence $\implies$ less noise.
Also, check out my older relevant question: Wind generators - why so few blades?
answered Sep 6, 2014 at 14:55
$\begingroup$
$\endgroup$
You have to balance competing issues, so it's an optimization problem.
Yes, more blades move more air, but also cost more power. (Like in a small aircraft, each propeller blade can't consume more than about 100 hp.)
If the air is moved through a smaller diameter fan, then it has to move at higher velocity (to get the same overall flow), and power goes as the square of velocity.
answered Sep 9, 2014 at 16:44