Propeller sizing 2

[BigInch]

How to size a wind turbine prop? No problem with diameter, my trouble is how many blades and how wide should they be at the widest point? I know two arn't good, cause they give the worst bending moment on the shaft when considering tower shielding of the airstream. I also assume even numbers of blades have the same problem to some extent. Any hints?

Call before you dig.

 

[Sparweb]

You asked the wrong people, if you're looking for wind turbine info. Google search my alias, and look at the "other" forum that comes up.
When you get there, just start reading...

Steven Fahey, CET

 

[BigInch]

Thx I'll try, but I've searched quite some time for specific information available on the web for designing props for wind turbines and found nothing on anything other than setting diameter, which is why I already know how to do that.

 

[AminG]

There are several propeller design programs (ie. Blade Gen, CFX, etc.) One can also write a potential flow program to determine blade profile, possible selecting a profile at an angle to minimize induced drag.

There are several documents on this subject (freely available) at the NASA document server. Hope this helps.

 

[Sparweb]

I could have been a bit less cryptic...

http://www.otherpower.com

The site is difficult to search, but you can also ask questions in the forum and people will be glad to help.

Speaking very broadly, the same "blade-element theory" that can be used for aircraft propellors and helicopter rotors can be used for wind turbines. The angles are backwards so you really have to watch out if you're using aircraft prop references, but you can make it work. Watch the Reynolds number...

Tower shielding gets progressively less important the more blades you put on the wind mill. Think about it: if there are more blades, then a brief effect on one at a time constitutes a smaller proportion of the whole.

Optimizing the overall rotor in # of blades and solidity is the subject of research done by Denmark's wind industry, the US NREL, and many other state research organizations, plus many private individuals.

If you want something more mundane than lofty NASA research papers, track down documents published by folks like Hugh Piggott, who make it simple for the layman.

Going back up the technology scale, the NREL published design guidelines for blades, generators, towers and all, which are now used as certification requirements for commercial wind turbines operating in the US (and other countries, too, I bet).


Steven Fahey, CET

 

[WKTaylor]

Big Inch

Suggest looking on STINET for some very interesting reports. All have an abstract so that the document can be pursued thru a technical library. Note: Many recent reports are downloadable (*.pdf format). Beware: they can be very large files.

Go To:

http://stinet.dtic.mil/

Search for " wind turbine ".

Regards, Wil Taylor