Effect of Blade Angle on Power Output of wind turbine

[memoguy]

Homework Statement

Hi all! I am been working on an EEI. Basically I recorded the power output (P=VI) of a wind turbine with the blades at different angles. I went from 0 degrees (flat) to 180 degrees in 15 degree increments. Averaging the data I see a graph like this:

Also, just to clarify, when at 0 degrees the wind turbine looks like this (also not how the wings are not airofoils):
http://oi48.tinypic.com/9ab66e.jpg

I am trying to write the discussion but I can't find the science behind the phenomena which causes the wind turbine to be most effective at 15 degrees. I am assuming it is some kind of trade off between drag and something else but I am just not sure what to google. If anyone could point me in the right direction, or even just tell me what terms I should be googling that would be amazing! Don't get me wrong, I certainly do not want anyone to do this assignment for me. I simply want a nudge toward some relevant information.

Homework Equations

NA

The Attempt at a Solution

Much googling...

 

[AJ Bentley]

I would have though this had more to do with the blade shape than anything else.
It looks like an aerodynamics question - an angle of attack of 15 degrees sound like an efficient sort of climb just short of a stall.

 

[rcgldr]

So why didn't 165° output the same power as 15° (just reversed direction)? Are the blades assymetrical (is the "back" side different than the front)? Is there a direction sensitivity to the power generator or whatever is used to generate a load?

 

[CWatters]

Lots of reasons why the power at 15<>165..

The blades appear to be crude injection moulded flat plate sections with square/blunt edges so the stalling angle could easily be different.

The difference might be down to the way the pitch angle is measured.

How was the wind generated? It might have been generated by a desk fan and have a rotating component making the angle of attack different at 15 vs 165.

To answer the question I suggest you google for images showing lift vs Angle of attack for other wing sections. Most have a sudden loss of lift at around 15 degrees although it can vary...

https://www.google.co.uk/search?hl=...urce=og&sa=N&tab=wi&ei=9JCWUJWiNqPX0QWdvoCYCg

Someone (including me) has already used the magic word that explains the name given to this effect.

 

[Nickie]

I would first like to commend you for your thorough research and data collection on this topic. It is clear that you have put a lot of effort into your EEI project.

To address your question about the science behind the phenomenon of the wind turbine being most effective at a blade angle of 15 degrees, there are a few key factors at play. The first is the concept of aerodynamics, which is the study of how air flows around objects. In the case of a wind turbine, the shape and angle of the blades are crucial in determining how the air flows and how much energy can be extracted from it.

When the blades are at a 0 degree angle (flat), they are not able to effectively capture the energy from the wind. This is because the air simply passes over the blades without creating much lift or drag. On the other hand, when the blades are at a 180 degree angle (completely vertical), they create a lot of drag which can slow down the rotation of the turbine and reduce its power output.

At a blade angle of 15 degrees, there is a balance between lift and drag. The shape of the blades, as seen in the image you provided, is designed to create lift as air flows over them. This lift force is what allows the blades to rotate and generate power. At the same time, the angle is not so steep that it creates too much drag, allowing the turbine to continue rotating efficiently.

Another factor to consider is the wind speed. As the wind speed increases, the optimal blade angle may also change. This is because a higher wind speed may require a steeper blade angle to maintain the balance between lift and drag.

In summary, the most effective blade angle for a wind turbine depends on the design of the blades and the wind speed. It is a delicate balance between lift and drag, and finding the optimal angle is crucial for maximizing power output.

I hope this explanation has been helpful in guiding your discussion on the topic. Keep up the good work in your research and data analysis!