Darrieus blade angle problem?

[PoLe]

what is the best angle for those fixed blades, so that they would generate the biggest energy amount.





I think that it is something 45 angle?





Anybody knows how this angle can calculate?

[PoLe]

formula for a drag coefficient (Cd):





so, I think that blade which is 180 degrees has Cd = 1


The angle will be something like 30-45 degrees?

[vawtman]

Hi

 The formula i used was just common sense and practical.Airplanes don't fly in little round circles so why design a profile that wants to go straight when it can't?

 What are your thoughts sizewise?

[spinningmagnets]

I could be wrong, but...

I believe the design consideration that makes a VAWT a "Darrieus" is a linkage that varies the angle of the blades so that the trailing blade is experiencing as much drag as possible, and the advancing blade changes its angle to experience the least amount of drag as possible.

If you VAWT has fixed blades, it is similar to a wind-speed meter called an "anemometer", but larger.

A high RPM 3-blade prop HAWT seems to be the best producer of electricity, but there are a variety of reasons many people are playing with VAWTs. For a VAWT, I believe you may get more bang for your buck with a "Benesh" or a "Lenz2". Best of luck and have fun.

[vawtman]

Yep your wrong :>) Many ways to skin a cat.

[PoLe]

OK... you guys misunderstood me.


I want to know example Cup-type anemometer drag coefficient those cups. forget those darrieus blades.


what is drag coefficient for cups which is adverse wind and tail wind?


when I know those values, then I can calculate performance of this anomometer.


but finally I need to know what is the best angle to angular shape...

[dinges]

Googling for 'drag coefficient various shapes' yields:

http://www.grc.nasa.gov/WWW/K-12/airplane/shaped.html

http://en.wikipedia.org/wiki/Drag_coefficient

http://www.aerospaceweb.org/question/aerodynamics/q0231.shtml

Etc.etc. More googling left as an exercise to the reader.

Peter.

[PoLe]

Thanks Peter! That is what I looking for.

[PoLe]

The shape is that kind of:

[vawtman]

Hey pole you stated

"What is the best angle for those fixed blades,so that they would generate the biggest energy amount"

 Now its a anemometer and darrieus is lift based.So no use for that purpose.

 Sorry i got confused and still am.

[spinningmagnets]

This looks interesting. The most useful VAWT applications I've seen so far have been used for generating 12 volts at low amps (due to low RPM's), but, VAWTs are cheap and fairly easy to make.

I haven't seen one like this before. Did you get the idea from someone else, or should we call it the "PoLe VAWT"?

Just as a fun mind exercise, lets talk about one with two vertical blades. With each blade having two halves like an aircraft "split aileron" used on flying wings with no tail (Northrop, Horton).

I would try having the inner half of each blade fixed at an angle determined by the well-researched "Lenz2", leaving the outer half to flop open or shut as wind strikes it. Heres pics and a blade angle discussion.

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=418

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