Fin Angle to have a better performance?

[Mechamz Mz]

Hi,

I'm going to redesign my turbine's fin, and change it to an aerodynamic shape.

This is my previous design.
http://img49.imageshack.us/img49/6526/p1010005va2.th.jpg
http://img49.imageshack.us/img49/6526/p1010005va2.th.jpg

http://img239.imageshack.us/img239/5967/photo0022cz0.th.jpg
http://img239.imageshack.us/img239/5967/photo0022cz0.th.jpg

and I redesign the fin from a semi circle to an aerodynamic shape.
this the idea,

http://img87.imageshack.us/img87/7835/turbinelu5.png
http://img87.imageshack.us/img87/7835/turbinelu5.png

however I'm not sure which angle of the fin can have a better performance
and these are the angle that I figure out,

1.
http://img529.imageshack.us/img529/4084/fin1yy8.png
http://img529.imageshack.us/img529/4084/fin1yy8.png

2.
http://img366.imageshack.us/img366/8122/fin2eu0.png
http://img366.imageshack.us/img366/8122/fin2eu0.png

3.
http://img528.imageshack.us/img528/5084/fin3eg1.png
http://img528.imageshack.us/img528/5084/fin3eg1.png

4.
http://img395.imageshack.us/img395/1659/fin4jg7.png
http://img395.imageshack.us/img395/1659/fin4jg7.png

A guide vane will be added for tested too, but I wonder if there is a guide vane to direct the wind, will the angle of the fin be not so important anymore?

and other idea to enhance are most welcomed =)

thanks

[Rob Beckers]

Mechamz, very interesting concept! Though I have to admit that I have no clue how one would go about analyzing this. If you have access to metal working machinery then maybe you can relatively easily mass-produce the vanes and build one for testing. Looks a bit like a squirrel fan (used in reverse). Please keep us posted!

-RoB-

[Mechamz Mz]

i just tried idea 1 today. it failed :(

1.
http://img529.imageshack.us/img529/4084/fin1yy8.png

turbine was turning anti-clockwise instead of what i expected(clockwise).

http://img381.imageshack.us/img381/8782/finresultwb3.png

the result was not satisfied, so I changed the angle into second idea.

2.
http://img366.imageshack.us/img366/8122/fin2eu0.png

the result was improved, and turbine was able to turn @ 2m/s. (without guid vane)

I'm in doubt and don't understand the failure of idea 1. Why it turned at an opposite direction?? and why second idea is better than first idea? is there any formula or software to determine the resultant force of this aerodynamic fin??

thanks =)

[Rob Beckers]

Your original drawing showed a pretty fierce angle-of-attack for the flow over that airfoil. It probably was stalled badly, still just from drag I'd expect it to turn clockwise. Who knows, interference of the other blades can do weird things to the air flow.

This may be a bit too much for your particular project, but NASA has free computational fluid dynamics software called "Overflow" (https://www.nas.nasa.gov/Resources/Applications/applications.html) that could simulate the airflow over your structure, and calculate forces. A friend of mine used it quite a bit for airflow simulations of a jet engine turbine. Not the easiest thing to learn though.

-RoB-