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Hoveroz - n/a
11-Feb-08, 07:42 AM
Can anybody shed light on the use of Centrifugal Fans for lift .



Cheers, Mark

profqwerty - n/a
11-Feb-08, 05:49 PM
I looked into it for a bit to see if it was viable. It seems they are much more expensive for the power you'd be putting through them.

Also it's very difficult to find anyone who'd actually sell you a fan for you to put on a shaft - they all come in blower type housings with electric motors.



I suppose they would be more efficient than axial fans? Certainly more durable.

bufo - n/a
11-Feb-08, 07:34 PM
Try this link...



http://www.imp-klimat.si/?k=116&j=1 (www.imp-klimat.si/?k=116&j=1)



Page is only in Slovenian language, just click the immages, and you will get complete product range...

Paul Fitz - n/a
14-Feb-08, 11:05 PM
Generally two types of commercial Centrifugal fans are available

Forward curved (many thin blades) in aluminium, Mild steel or plastics.

smallest of the two types, has an overloading characteristic with increasing speed (ie power consumption continues to climb) runs at slow speeds n=750-1500. n=3000rpm on smaller sizes only. Needs volute to work well. Impeller measured externally (blade thickness usually only 15-40mm). ie inlet dia about 30-80mm dia less than stated Dia.. Note: when sold in a fan, fan inlet dia is given and this is not always the same as the impeller inlet size.



Backward curved (fewer wider blades) mostly steel or plastic.non-overloading (reaches maximum power absorption). run at higher speeds than equiv. FC CF typ. n=3000rpm. much larger impeller but will work without volute albeit at lower efficiency. Measured internally. (Blade thickness typically 120-200mm). Generally has a higher efficiency than a FC CF when used with a volute.



In either case you are unlikely to obtain an adequate duty without using a fan(s) of 450mm or larger. making the fans much bigger than an equivalent axial. All CF fans must be perfectly balanced or they will shake themselves apart. Axials are rarely seriously affected by out-of-balance unless they lose a blade. It is unwise to run a CF fan much over the manufacturers recommended speed. This normally makes them unsuitable for smaller craft (up to 4-5mtr) unless designed and built for the job.



Generally large dia narrow fans produce higher pressure, broader fan (eg double inlet) are designed to move more air at lower pressures.



In short unless you are building a 6mtr plus craft-cheaper easier and lighter to use axials (worth considering series axials even then).



HTH.

Irish Falcon - n/a
15-Feb-08, 05:55 PM
Hi, here are some pics of a Russian built craft with centrifugal fans, double inlet, for lift, its based near Cork. Sorry about the poor quality phone pics. Philipindex.php?t=getfile&id=1199&private=0index.php?t=getfile&id=1200&private=0index.php?t=getfile&id=1201&private=0