Nose Cones

[newguy]

i would just like to know what information you all have about nose cones on the front of the windmill blades. do you have any links personal info on the subject any equations. i think a nose cone would more readily direct the wind across the blades face for more force right. i found a page where this person doesnt use a cone because it decreased efficiency i plan on testing this on my own but any info given will be greatly appreciated.

[jacquesm]

nose cones are installed for several reasons:

to protect the mechanics from the weather

to force the flow that would otherwise hit the front of the machine over the blades

to improve startup

I'd like to see your reference to the article that states that a nosecone decreased the performance of a machine. I can see an oversized - or undersized - nosecone having a neutral or slightly negative effect, but a properly designed one should be either neutral or positive.

One more remark about a possible negative effect of a nosecone. If your machine is starved for air to cool the coils then a nosecone might shield it from receiving enough air to keep the coils below meltdown. In that case it is probably better not to have one !

Nosecones are standard fare on almost all commercial windmills, the main reason they are used there is usually to protect the feathering mechanism from the weather.

 

[newguy]

its this site

http://www.hydrogenappliances.com/conecon.html

i dont know though

[p0lizei]

How about putting the turbine in a duct?  From what I've read, this would increase efficiency and safety while reducing noise.

[juiced]

Here is an example of an enclosed turbine.

http://www.juiced.ca/phpbb/viewtopic.php?t=5

[RatOmeter]

Having seen that link, I will echo Jacques' words.  

to protect the mechanics from the weather

well, the hydrogen appliances mills don't have any mech to protect out front

I can see an oversized - or undersized - nosecone having a neutral or slightly negative effect

the cone shown at that link appears to be enormous compared to the turbine diameter

I will say that, as unprofessional as hydrogen appliances website and R&D appears, their conclusion is right for them.  They "can't justify trying to sell you a cone"

[p0lizei]

Is that a radial flow turbine?  The one I saw when I was researching ducted wind turbines was basically a shrouded axial flow turbine.

Of course, if one were going to set up a ducted wt, they would probably need a more sturdy platform than what is required of traditional wind turbines.

What am I doing up this late!?

[jacquesm]

This is a cut - and - paste piece of crap designed to lure users away from fieldlines...

The reason for these posts is to generate ad revenue for the poster, pure and simple.

There has been a pattern to this lately, and I'm not sure that I like it.

It's called 'sitejacking'. Fieldlines is run by ethical people, giving you all kinds of ways to legitimately inform people about your internet presence, such as in your header, contact info or signature. To jump into every thread with an external link to lure traffic to your own site is really not friendly.

[TomW]

juiced;

I am fairly certain this sitejacking comment is directed at you. By now it has become obvious to many of us that while you may have started with good intentions you have crossed a line with these continuing posts with links to your so called website.

T

[Gary D]

No, they are trying to sell you more blades below that on the same page! Their alternators mustn't match their blade length very well... Dan B. and Hugh fix the problem by changing the ammount of coil windings or magnet gap, and overspeeding by the furling... Who says making a wind Generator isn't rocket science?  Gary D.

[juiced]

Read this. this isnt the thread to complain in.

http://www.fieldlines.com/story/2004/11/23/101557/24

[finnsawyer]

When a fluid, such as air, flows around an object, such as a nose cone, it's speed increases.  This increase in speed drops off with distance from the object.  Because of the speed increase, the power available in the air stream is greater.  In fact, for a hemisphere, the power available actually is greater for the air hitting the blades with the hemisphere (nose cone) than it is in the case of the entire cross section of the blade assembly without the nose cone.  If the nose cone has a radius of half the diameter of the windmill a maximum power gain of 22% is attained. At least that's what theory states.  Of course, to tap this power increase the pitch profile of the blades must be different.  If you think this effect is a crock and you live in an area of large snowfall, I suggest you go out and check out the depression that forms at the base of a tree or utility pole due to the wind.  Think about it.  There is definitely a concentration of energy taking place.  

[rotornuts]

I have the feeling the blades performed poorly with the addition of the nose cone because no compensation was made in their design. I also think it would have been wise to stand the blades off the nose cone somewhat to prevent any turbulance that may have been generated by the nose cone blade junction from propagating up the trailing edge of the blades.

[finnsawyer]

Yeah, you need to change the pitch angle and width of the blade as a function of radius to compensate for the speed up in the air stream.  When the air moves around a sphere it speeds up by 50%.  This then drops off with distance along the blade.  This speed up means an increase of over three times in the power density near the sphere, which drops off with distance.  While turbulence may occur, one would also be capturing the energy normally lost near the hub.

One thing that has occurred to me is to use a hub diameter 30% of the rotor diameter (a theoretical 15% gain in power) and extend the hub behind the rotor and then use a transmission using a rubber tire inside the hub to get say a factor of three speed up in shaft rpms.

The problem is that to undertake a rigorous study of this effect would be time consuming and expensive.  Best left for the University level?