a basic wind blade analysis

This vid. is about basic blade analysis, specifically the angle of the blade with respect to the wind. Perhaps I used the wrong (origin or reference position of the) angle, but I was consistent and in general it was ok.
Though the thought process was a bit sporadic, you should of at least got a drift about this subject.


Key points:

A blade "flat" into the wind will not rotate. A blade should be rigid, that is, not to waste the wind energy bending the blade in the direction of the wind.

A blade completely "out of" the wind will not rotate.

At any angle inbetween those mentioned above, the blade will rotate (towards the lower pressure side of the blade). They will rotate away from the applied wind pressure (wind force/power).

At a 45 degree angle to the wind, the apparant values of the collected wind force that will cause rotation, and the resistance (drag force impeding rotation) due to rotation will be equivalent.

To reduce resistance force (drag) the angle is reduced.

When the blade angle is low (to reduce wind drag) the available rotational force is reduced per a given blade width. To increase the rotational force, the blade width can be increased.

Naturally due to "overcrowding" near the center or axis of rotation when many blades are used, the blade part near the axis will be (or can be) narrower than the wider blade segments farther out from the center. Wind forces applied to the blade farther out from the axis of rotation will cause more torque (rotating) force.


Here are the encyclopedia entries for the VAWT and HAWT wind turbines:

http://en.wikipedia.org/wiki/HAWT#Horizontal_axis

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

Here are two very important articles I came across recently, after making this video, on the power to expect from a wind-electric generator, and wind turbine types - and beneficial "lift" (due to the blades construction) is mentioned.

http://www.otherpower.com/windbasics1.html
http://www.otherpower.com/windbasics2.html#http://www.windturbine.net/

otherpower.com is a common source for green energy projects. Also, a big "wind power" site is : gotwind.org

What what I can understand for now, after reading on otherpower.com is that the tip (or "farther out from the center") of the blade is going faster (but still the same angular velocity per sec, min, etc); you can imagine it as going a greater distance per unit time. And the blade will be curved a certain way as it gets farther from the center, to do something, to enhance the performance. Not exactly sure yet, it could be since the tip is moving faster there might be more drag/wind resistance encountered there and the angle of the blade is reduced? is this correct?? I could say to reduce drag forces on the outer parts of the blade one could start with tapering the blade thinner out to the tips. Does anyone know since it's not too intuitive, even if it's simple concepts and we shouldn't take it for granted? I believe this is correct. And the increased drag forces farther out of the blade can cause the blade possibly break so this is one reason they are smaller farther out. Another reason that they are or should be smaller farther out is that if you think of the blade as a lever, and the fulcrum is at the axis area, the forces of the wind farther out will have more "lever action" there and can bend the blade along into the direction that the wind is going and could potentially break the blade.

I recently found this discussion(s):

http://www.windpower.org/en/tour/wtrb/rotor.htm

http://www.windpower.org/en/tour/wtrb/blades.htm


http://adsabs.harvard.edu/abs/1985iece....3U...3S

Also, the edges of the blade should be airodynamic. And from my simple "tilted-board" blade, it means a rounded or smooth thin edge, rather than square from its front to its backide. That goes for leading side (into the wind) and trailing side of the blade since you don't want a (partial) vacuum on the trailing side of the blade slowing the blade down.

As of Feb, 6, 2006 I was given a link to some relatively new videos that are about 3 months old now here on YouTube that have a good analysis of Wind Energy/Power: Here is the first in the series:

http://www.youtube.com/watch?v=GExTwRNkQBg&feature=channel_page

OR to see them all: http://www.youtube.com/profile?user=nptelhrd&view=videos&query=wind

The second video in that series mentioned above basically explains that the lift and torque forces on the blade must be balanced along the blade (because they can basically break). As you can see and imagine, there are alot of forces acting on the blades and system to consider. These need to be considered for for safety and efficiency (where power absorbtion/transfer is increased and losses are reduced) of the system. Thats enough about those vids, just go watch them all yourself.

Category:

Howto & Style

Tags:

• blade
• analysis