new model vawt

[rotornuts]

Well this is basicly just like Ed's with some changes in the venturi and cambered wings. I built it as I had drawn it and it far outperforms the first one in all respects, self starts easilly as well.





This is the template. I literally blew this image up to 14" diameter and used it for the template.





This is another crude model but as far as testing goes I'm satisfied enough now that I'll put the effort into a well done working unit for further testing.

IMHO these things are easier to build than HAWT's

These are the links back to the other posts on the topic:

http://www.fieldlines.com/story/2005/5/22/75439/4056

http://www.fieldlines.com/story/2005/5/21/204220/623

http://www.fieldlines.com/story/2005/5/20/204046/109

Definitely having fun now!

Thanks everyone for the input.

Mike

[zap]

Looks like the rotor of a Wankel.  You could call it the WWW VAWT (Wankel With Wings)

[gizmo]

Hi Mike

I've been reading your VAWT posts with great interrest. Now that you have a working profile you should see if you can get some rpm figures, and maybe even connect it to a generator and get some power from it.

Glenn

www.thebackshed.com

[richhagen]

I'd be curious to read about the power performance.  I suspect it will be significantly lower than a hawt of the same cross sectional area into the wind, but it looks simple to assemble.  Rich

[windstuffnow]

  Nice work Mike!

    Looks like your well on your way to a very nice little H unit.  Your right they are much simpler in construction than their counterpart.  Just as fun to watch though!

    One thing that was changed on mine, which I haven't posted on my site, was the round nose of the wing.  The round shape creates a Cd of almost 1 which will absorb alot of the upwind lift your creating.  I tested mine at various angles in a locked rotor position with a single blade and measured the torque from the shaft.  In any case, that was changed to a better air foil shape and the drag was reduced to a Cd of .4 and more torque was added to the shaft output.  You might consider reducing the solidity as well, the shorter wing chord gives the air a bit more time to re-establish a flow after being diverted from the front wing.

    Once again, very nice work!  I think you'll be quite surprised at the overall output of the machine.  

Hav eFun

Windstuff Ed

[ghurd]

Looks great.

Is that made of scrap paper and cardboard???

What is inside the wings?

G-

[Ungrounded Lightning Rod]

I'd really appreciate a comparison of the performance between this and a Sandia Savonius of the same dimensions.

[rotornuts]

Hello all. Gizmo and zap, thanks for the thumbs up(I think).

Rich, I'm going to build a unit that I can attach an alt to for actual testing but till then it's just visual observations and gut feelings(seat of the pants science). I do expect this to perform somewhat better than I would have thought a VAWT would untill I actually tried it.

Ed, I'm going to reproduce this as is for now to establish a benchmark before I fiddle with the design. I was originally concerned about the solidity but the wider wings seemed to work better with the venturi on paper and so far I'm seeing impressive rpm in a stiff wind suggesting it may be ok. The part that impresses me most so far is 50 rpm in no decernable wind at all! I would dance like a school kid on the last day of the year if I could wind tunnel test things with a smoke stream for visualizing airflows. I'll make the test unit so I can swap pieces to do comparisons

ghurd, It's a corrugated cardboard center, heavy posterboard wing skins and plywood ends and wing/center hub forms. I used salvaged skate rolls(not roller skates but material transfer types)for bearings. Total cost not including stuff I had on hand: $7.50 The wings are hollow, the whole thing is held together with the poster board and cardboard.

Underground, I'm very excited about this unit(thanks ed) and will post all test results in the future. I expect this will beat the pico turbine type savonius if that's what your referring to. I think the sandia savonius would have greater start torque but the curves would intersect quickly as the rpm increases as the above unit likely has significantly less drag on the upwind side. I'd also expect much better high wind performance with out the associated failure issues. I have much to learn yet though.

Thanks all,

Mike

[XRay]

Hi Mike,

I see your making paper models to, looks good!

Hopefully I can free some time and make an exact replica.

This sort of Lenz turbine is a lift type, it must exceed tsr 1. So comparing it with a Savonius, which never ever reaches tsr 1, will be something like comparing apples with pears isnt it? Anyway I never came across good scientific research documents for a VAWT lift type, like Sandia did for a Savonius drag type :[

Benchmark it, you will dance a lot of RPM ))

Ray

[Kwazai]

http://www.aerotecture.com/

with what I see in the background of the pic- you might want to try it on top of the building like the ones pictured on the page above.

L8r

Mike

[RobD]

Me too. I haven't built Ed's yet but my little Sandia machines do quite well. They aren't the same config. as the pico. I think that's basically just a couple of half drums.
How does it fair in high winds?

I'm thinking of using cogged belts to the alternator.

[rotornuts]

So far things are going well considering the model is crude. I don't think this will have prodlem in high speed. It will likely self regulate while providing good power output. wishfull thinking and speculation based on solidity and it's overall cylindrical form. If the wind becomes too high it will effectively present itself as a solid cylinder and shed the wind nicely with relatively low drag.

[richhagen]

Interesting, they are right near me and I had never heard of them.  Interesting that they propose to mount these on building roofs similar to some of mine.  Hawts larger than a foot or 18" make me nervous in an urban environment, two by fours rotating at high speed in an urban environment don't sound like a good idea to me, too much kinetic energy in a failure.  Rich

[hvirtane]

I've been playing with

an idea to put there

inside a savonius.

 

Also I'm thinking that

the wings should be skewed

to get it working smoothly...

but how to make that

isn't so easy...

- Hannu

[rotornuts]

Hannu, I think you'd be surprise at how smooth the the posted model runs.

[electrondady1]

well, my comp. goes down for a week and i miss this ! i wont't be left behind! a vawt once again becomes the hot ticket.rotonuts, congratulations on leaving the dark side of the force(hawt),this research your doing is very interesting and propably important. i am curious as to a comparison in torque/rpm over a three bladed drag type unit (the configuration i've been working with).  what are the criteria for deciding the lengh/profile of the air foils ? i'm thinking the lengh controls the size of the aperature to the inner shape. there must be some sort of balance/compromise there. also,  the details of the inner shape, propably no  limit to the amount of design work possiple there. i'm also interested in the limits the profile could be scaled up to, like ,12 to 18 feet in diameter.good luck, keep us informed.

[Kwazai]

I'd be thinking it no more dangerous than a roof top airconditioner unit-still some possibility of a failure mode though. the vawt you are woking on would probably work as well in hawt mode though. I would wonder about a helical configuration for self starting. The available wind powere on top of a five story building in an urban environment would probably make it worth the effort. From what I understand where I live-you need to be a good 65FT up in open area to have a steady wind(Piedmont/coastal plain -North Carolina).

Makes for very tall towers for wind and there's not much there in the first place.

anyway- I like the design you've got. I wonder if the selfstarting would be improved with just a small (18 degree or less) offset in the internal and external rotors.

L8r

Mike

[Kwazai]

I like it, and will build one at some point. I'm curious as to how it behaves with one side blocked from the wind (whether the forward moving side is producing noticeable lift?).

L8r

Mike

[healerenergy]

Rotornuts

Have you done anymore work on your new model turbine.  If you have I would really like to see what you have come up with.

George