Author Topic: Darius Airfoil Profiles (Read 7405 times)

alterfuels · « **on:** February 09, 2006, 07:25:56 PM »

Hey all! I am new to this site but love it already! So much info I have been looking for. I live on Lasqueti Island a small gulf island of vancouver Island BC. I am hopeing to build a darius mill to produce hydrogen for a fuel source. I would love to get a naca 0021 profile to try for my first attempt at a small mill. Also any info on suggested dimensions. Thanks for any info and the great forum! Jason

bobn · « **Reply #1 on:** February 09, 2006, 03:19:44 PM »

Here is a pic of a naca 0012 airfoil. click on contour data for the numbers.

http://www.nasg.com/afdb/show-airfoil-e.phtml?id=888

or go here for additional infomation on airfoils.

http://www.ae.uiuc.edu/m-selig/ads/coord_database.html#N

Bobn

vawtman · « **Reply #2 on:** February 09, 2006, 06:04:25 PM »

How do you plan on storing it and why?I wouldnt mess with it.Has far has the blade profile goes I tried to load it up and my com got mad at me.Could you post a pic?Thanks and have fun.

bobn · « **Reply #3 on:** February 09, 2006, 06:20:58 PM »

The naca 0012 airfoil section pic is also available in the Irc otherpower photo album here.

http://www.anotherpower.com/gallery/airfoils/naca_0012

Also many other photos of RE projects from people all over the worldin the main album

Bobn

vawtman · « **Reply #4 on:** February 09, 2006, 06:45:27 PM »

Thanks Bobn,What made you decide on that shape for a Darrius?And whats your plan to attach it?Got a drawing in your head you could may maybe post.I cant post drawings worth a crap but maybe you can. Thanks.

wind4Reg · « **Reply #5 on:** February 09, 2006, 07:42:06 PM »

Hi Jason, glad to see another Darieus enthusiast. I was curious though, have you done much research into hydrogen production yet? Not that I want to discourage you but it takes a heck of a lot of H2 to power even a small engine for a short time. I started looking at H2 a while back and after I did the math I realized that I would need a huge storage capability and a very expensive 3 - 4 stage compressor to make it all work as a fuel. In the end it was so costly that I put it on the back burner of my mind for a while if you know what I mean. Personally I think a huge manure pile holds more possibilities that H2 right now. I hope you build the wind turbine though, that is a great place to start.

wind4Reg

whirlybird · « **Reply #6 on:** February 10, 2006, 12:10:34 AM »

G'day Alterfuels

Good luck with your project Hydrogen is no more dangerous than any other fuels

a little common sense goes a long way.

All that aside I have made several Hydrogen machines using electrolosis principles

if you need a bit of help you can contact me at beverlec@tpg dot com

regards

whirlybird

Marty · « **Reply #7 on:** February 10, 2006, 12:10:38 AM »

hey great to see someone workin on a vawt as mentioned the 0012 would be a good place to start might also look at 0014 or even thicker depending on what you want there is no one airfoil that works for everything

Marty

alterfuels · « **Reply #8 on:** February 10, 2006, 01:04:10 AM »

Thanks all! I know I know h2 is complicated and expensive but if I don't start somewhere then I'll never learn. I live on a small gulf island in BC and don't need much fuel for 1 round trip so even a 100# propane tank should be enough to make a trip or to. I am looking to play with it and eventually start a business. I have my eye on a couple big creeks up an inlet to produce power. Expensive is right though priced it out to be half a million start up! OUCH!!!! But what fun is life without dreams. And what if dreaming makes them come alive. Anyway enough of that. Will the oo12 self start, and if so what angle from the support should I start with? Thanks for the info and keep dreaming! Jason

alterfuels · « **Reply #9 on:** February 10, 2006, 01:22:48 AM »

Hey marty! Could you give me some basic proportions to make my wing? Lenght to hieght and hieght to space between the wings? Thanks for all the intrest!

wind4Reg · « **Reply #10 on:** February 10, 2006, 05:31:07 AM »

Hi Jason, with enough wind the NACA 0012 will eventually self start, but it has to be real windy. I think you were on the right track with the NACA 0021 in your first post. The fatter profiles self start much better than the thin profiles. If you do some internet scouring you will find that the only Darrieus style straight bladed VAWTs that have been built for sale by companies that claim self starting (without the assistance of a motor, savonius rotor or giro-mechanism) have fat profiles. There are all sorts of claims of better performance from other thin configurations but no one I have found is producing any turbines commercially to back up these claims. I'll leave the technical explanation of why fatter profiles self start better to the experts, in my own understanding it is because the fatter profiles produce lift over a larger angle of attack than do the thin profiles. That is why you see all the thin profile experimental machines with variable geometry so that they can have the blades oriented so that they are able to produce lift and self start by optimizing the angle at which they produce lift. I built a model using NACA 0018 profiles and it self started reliably. You can see it in action here:

My H-Rotor

wind4Reg

wind4Reg · « **Reply #11 on:** February 10, 2006, 05:36:25 AM »

Hi Jason, I like to go with a ratio of about 3:2 (crossarm : blade height) for a 2 bladed H-Rotor configuration. Can I prove this is the ideal ratio, not a chance, just my own preference cause I know it works.

wind4Reg

wind4Reg · « **Reply #12 on:** February 10, 2006, 05:45:45 AM »

Hi Jason, here is a link to some FREE software that is real easy to use and it lets you print out your airfoil so you can make a template to build it:

Profili2

It has a database of a lot of different profiles, and if you register it (the registration is real cheap) then you get quite a few more features. I have the unregistered version and in the version I have if you try to save as an autocad drawing from the file menu it says you need the full version, but if you try to save as an autocad drawing from the button menu it works. Just an oversite on the part of the author of the software I am sure, but it is a feature/bug I like.

wind4Reg

IntegEner · « **Reply #13 on:** February 10, 2006, 08:24:27 AM »

Lots of surprisingly good websites on blade profiles. I get mine from the book by Abbot and von Doenhoff. Trouble is that it is easy to invent profiles that don't exist in any of this aviation material, including doubled blades or partially doubled blades, each with different cambers and thickness-to-chord ratios.

If the folks there in Canada, who seem to favor these Darrieuses, would please knuckle down and do some more theorizing instead of relying on your blessed government to do it for you all, maybe a start can be gained on making something work in the long run!

Meanwhile, I am sure everyone has heard by now that the nation of Iceland has taken the lead on doing hydrogen things.

Anthony C.

IntegEner-W

www.integener.com

DanB · « **Reply #14 on:** February 10, 2006, 02:17:14 PM »

"Lots of surprisingly good websites on blade profiles."

Yes, agreed...

" I get mine from the book by Abbot and von Doenhoff. "

There are lots of fun places to get information.

"Trouble is that it is easy to invent profiles that don't exist in any of this aviation material, including doubled blades or partially doubled blades, each with different cambers and thickness-to-chord ratios."

There's lots of research involved with airfoil profiles for aircraft - and wind turbines. Usually with airfoils my understanding is the 'guessing' doesn't work so well, they are hard to predict - trial and error (testing them in wind tunnels or on wind turbines) yeilds the only really useful information. I think folks would be very curious to see actual tests of your ideas on machines with known swept area with well matched alternators - but without such testing then you either leave it to faith - leave it for somebody else to do... or it all means very little.

"If the folks there in Canada, who seem to favor these Darrieuses, would please knuckle down and do some more theorizing"

How about some 'testing' -theorizing means very little without testing.

"instead of relying on your blessed government to do it for you all"

Lots of folks here are doing lots of testing and lots of testing is being done by many companies - not just governments. This is important stuff though and it is nice that governments are spending their money wisely to help figure some of this stuff out.

"maybe a start can be gained on making something work in the long run!"

Lots of good stuff has been figured out that works just fine.

"Meanwhile, I am sure everyone has heard by now that the nation of Iceland has taken the lead on doing hydrogen things."

Speaking of relying on the 'blessed government' to do it all.... ;~)

Ungrounded Lightning Rod · « **Reply #15 on:** February 10, 2006, 04:00:16 PM »

Using electricity to make hydrogen and then burning the hydrogen to power a heat engine (like an auto engine) means throwing away more than 4/5ths of your energy.

If the distance you need to drive is low enough and trips far enough separated you'd be FAR ahead to use a battery-powered electric car for the trip and recharge it from your mill (or your local battery bank). Even taking into account the power you burn hauling the weight of the batteries around.

The difference is a factor of maybe 4 or more in the number of mills you need to build, or a factor of 2 or more in their diameter.

alterfuels · « **Reply #16 on:** February 10, 2006, 09:48:18 PM »

Batteries suck ass high upkeep and shotrt life expectance and toxic to My game is less efficient but that is not everything in life. Plus hydrogen is fun! If I was worried about efficience (and spelling) I would build a hawt! I want to experiment. that is how great things are created! Anyways I am intrested in trying it so I can produce energy in remote places and transport it. In BC canada we have a huge amount of remote micro hydro sites that tyeing into the grid is impossible so this is a way to transpurt energy with a lower setup cost. So I want to start at home so I can learn about something without an enginerring degree! Thanks everyoune for the support and info! Jason

alterfuels · « **Reply #17 on:** February 10, 2006, 09:55:16 PM »

Iceland also has the advantage of lots of energy from thermal power and little natural resources besides that so they started before people with lots of resources or bigger sticks to beat thoughs with the resources! Keep playing and enjoying our benefit of first world so we can find new and exciting things! Jason

elvin1949 · « **Reply #18 on:** February 11, 2006, 04:00:19 AM »

Dan

Well said.

Elvin

IntegEner · « **Reply #19 on:** February 11, 2006, 07:23:15 AM »

The images on my website are all I have to offer. They not only say what has been done but also tell everyone where I am headed. Don't need to copy me or be bowled over by something new. They ask me from the grant program that is reviewing my proposals, "Where is the innovation?" I tell them that the innovation is in recognizing that something can be gained from doing this. People tell me it is dumb to just make 8 foot tall microrotators that are so small they only can occasionally light a few LED lights but I tell them it suits me fine because I am just a dummy. Besides, sales are beginning to trickle in on these things.

Anthony C.

IntegEner-W

www.integener.com

finnsawyer · « **Reply #20 on:** February 11, 2006, 09:23:35 AM »

One advantage of Government research is that the people doing it are trained in how to report the results, so things are not ambiguous. Based on what you have written here, you should be qualified to do this. Yet nearly everything you have said here is ambiguous. This includes your response to the grant people. If you get the grant let me know, because do I have a story for them or their counterparts.

Ungrounded Lightning Rod · « **Reply #21 on:** February 15, 2006, 10:01:56 AM »

I just want to be sure you know, before you dive in, that you're biting off TWO very difficult and dangerous problems that caused a lot of very well-traned trained engineers a LOT of trouble.

Darrieus mills are interesting but have a major fatigue problem which makes them tend to come apart after a while - with a LOT of kinetic energy to turn into flying pieces when they do. They've mostly been abandoned after a number of disasters, in favor of horizontals for efficiency or the safer savonius for vertical designs. If you really want to do a vertical, a savonius design gets maybe 2/3s the energy from a given cross section and is easily scaled up to compensate.

Hydrogen for vehicles is a problem mainly due to the lack of an efficient storage system for it (other than by attaching it to a carbon backbone), but also because of the extreme danger of handling it. It gives off only INvisible light when burning, so you walk right into it - and burns VERY hot so it damages you before you know it. And it's so easy to light that hydrogen leaks are USUALLY lit - but not QUITE often enough to prevent explosions that tear apart buildings and throw the pieces large distances as they set them on fire. (NASA engineers used to find hydrogen leaks by holding out a piece of cardboard as they walked around. When it burst into flame they'd found it.)

This stuff is dangerous not just to you, but to your family and neighbors. If you are single living alone out in the country, with a lot of area around your site for flying pieces to come down in, in an area where wildfires aren't a problem, it's your life. If you have dependents, housemates, or live in a town, city, or fire-prone area I recommend you avoid both projects (and only take up ONE of them if you get major engineering training and funding).

Henry Swayze · « **Reply #22 on:** February 15, 2006, 08:29:18 PM »

Thanks for your inputs. I was not aware of the fatigue problems of strait darious machines. I did know that I would be building big and that their would be list of strain. I had planed to go fiberglass over foam with carbon fiber tension inlays like a stunt plane. My overall purpose is to generate all the power I need at a reasonable cost with out making a many year project out of it. I may succumb to a horizontal. The breezy 5.5 has my attention as a practical performer for a modest wind site. http://www.prairieturbines.com/

As to hydrogen, I wasn't planning to go there. I live in rural Vermont with long travel mileages even to the supermarket. I had thought of a hybrid with extra batteries after they get the price under control. We have net metering and I am hooked to the grid.

Ungrounded Lightning Rod · « **Reply #23 on:** February 16, 2006, 04:42:13 PM »

A darrieus mill has a TSR up around 6 or more - but that whole blade is the "tip" so the whole thing is moving somewhere just below mach 1 in a high wind - with its whole mass being accellerated through a tight loop every turn, resulting in enormous forces required to pull it toward the axle. (That's why the "eggbeater" versions are the shape they are: They're modified catenaries, so the centripital forces are pure tension in the rotor. Straight blades experience this as a strong bending moment.)

As with all vertical mills the force on the rotor blades goes full circle as the rotor turns. But with a Savonius-style design the force is spread out over a broad blade. A darrieus decelerates the air just as much, and so experiences as much force - but it's all concentrated on those narrow blades. So it has an enormously concentrated force working on the blades. Additionally, each blade experiences a shock as it passes the windshadow downwind of the axis, and additional stresses as it goes through the windshadows of the other blades. (These are shocky for a straight blade, propagate along the blade in an eggbeater.)

So you've got all these giant flexing and near-constant forces on this narrow blade. Eventually it breaks. Of course that happens in a high wind, when both the forces and speeds are highest, so pieces that come off are going several hundred MPH. B-)

When a piece leaves it goes nearly horizontal in essentially any direction.

A horizontal axis machine has blades that make such speeds at the tip. But on the average their mass is goiong less than half as fast. They experience the forces, but distributed over the length of the blade. And the forces are always from the same side and vary only a little through the rotational cycle. They can still come apart. (Especially if you screw up and let the blade flex back to hit the mast or the tail over-furl and hit the blade.) But they're a lot easier to design so they don't, and they don't wear out from fatigue anywhere near as easily. (Just don't use something like aluminum, which will fatigue from only small flexing.)

When a horizontal axis mill comes apart the pieces tend to be thrown in the plane of rotation - which is roughly predictable from the weather patterns. So not only are they much less likely to shoot or throw just-subsonic baseball bats around (and still less likely to do it as a surprise after several years of peaceful operation), but if they do throw chunks they tend to throw them in a smaller number of moderately predictable directions.

Henry Swayze · « **Reply #24 on:** February 19, 2006, 07:55:23 PM »

All good input. I will go slow on getting to a large vertical.

Any thoughts on attempting a 100' tilt up lattice tower for a heavy 19' sweep horizontal? I own a utility line truck with a winch in the boom end and a big winch in the bed.

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Author Topic: Darius Airfoil Profiles (Read 7405 times)