Designing, Building and Testing a Darivonius VAWT
WOW, here we are, about a month into this project. The designing part will soon be ending and the building will begin.
After I have considered the great advice and suggestions, here is my tentative plan:
The turbine will be 72 inches tall by 48 inches in diameter (24 Sq. Ft – 2.23 m Sq.) For the Darrieus section, it will have three blades approximating the profile of a NACA0015 or NACA0018. I say approximate, because I will build those using common parts and easy construction.
I will buy a solid steel shaft 1 ¼ by 72 inches long (32mm x 1.83 meters). I chose 48 inches for the diameter because I want to use one sheet of 4 x 8 plywood for the bottom and top rotors of the turbine.
I have not yet decided on the configuration and the number of blades for the drag section in the center that will help start the turbine spinning. The ratio between the Darrieus and the Savonius-like center will be according to Adriaan's recommendations of 0.381 times the diameter of the Darrieus. It will be about 18 inches in diameter.
This is what I will be doing in the near future:
To determine the configuration and number of blades for the drag section, I will build a small specimen to do extensive testing. That small specimen will be 36 inches tall and 18 inches in diameter.
I made these patterns for possible configurations for the center section. The blade is an approximation of the CFD optimized Benesh blade. The small specimen for testing I will build in a way that I can easily change the number and the position of the blades. That way I can try many configurations to find the one that works best. These patterns are for three blades but I will be testing two blades also.
I would really appreciate your opinions about these patterns. Don't be afraid to be wrong, because as far as I know, nobody has evaluated anything like this, so no matter what you say, you can't be wrong. The one with five blades, how would that behave concerning TSR and RPM?
After I determine the best configuration for the center section, I will build the full size center section and test it using the alternator that I will build for the turbine.
I'm beginning to get excited about this.
Today I received my anemometers. I checked my fan and the highest speed I got was 18 MPH. I might have to build a shroud for the fan to concentrate the flow to see if I can get higher wind speed.
These anemometers are nice little gadgets, very sensitive. I went outside and the wind speed was 3 MPH. Then I came inside and I tested my normal walking pace. It was about 2.4 MPH. Next thing I want to do is give it to one of my kids when they are upstairs so they can measure how fast they come down when my wife calls them for ice cream.
Ed