QBLADE: a blade design and analysis software

[opo]

You probbably already heard of the Qblade program:

http://qblade.npage.de/

It is a graphical interface to xfoil and xflr5 programs plus it includes the designs of blades by stations and one can also define the rotor (2, 3, etc blades).

Basically one chooses an airfoil(naca or custom) for each station, specify a chord, pitch angle and ofset(?) at each station. And then one can run several types (which can be defined) of simulations on the turbine, airfoil,etc.

Anyway, jus liked to share this find. The first two comparisons I did was between the goe222 no taper no twist vs the blades I'm currently ussing, both at 4'. The windcharger type blade beat the $%&/ out of my blades.

Cheers,

Octavio

[opo]

Here are some examples  of the graphs that can be obtained with this software. Of course, I now need to understand the meaning of all the parameters and variables involved, but otherwise I'm having a lot of fun.

Foil analysis:



Blade simulation:


Turbine simulation:


The rotor is 13000mm in dia, 3 blades with goe222 profile, straight 180mm constant chord and 20 deg pitch.
Cheers,

Octavio

[SparWeb]

Hi,
I downloaded a copy, but I haven't tried it yet.  Oops!

Looks like it covers the non-dimensional factors (Reynold's number, lift/drag coefficients, angles of attack, etc.)

How about the subtler performance variables, like induced flow ratio, or coning angle?

But maybe I should try it for myself and find out!

[opo]

Hi,

I cannot tell if such parameters/variables are considered. I'm new in airfoil/blade/rotor theory and I'm starting to enjoy it.

There is a very general description of the program and some of the variables it uses in the guidelines:

http://qblade.npage.de/get_file.php?id=13112771&vnr=503997

That's about all I have found as far as documentation. I read somewhere this software was part of a graduate thesis from the author but I cannot find this info anymore.

Good luck,

Octavio

[SparWeb]

Qblade's author doesn't explain BEM theory - they assume you are already familiar with it.  So you can experiment with Qblade for a while until the "plug-and-chug" method gets confusing or you just dive in with both feet and do the calculus!

Have I scared you yet!?   

For general learning about wind turbines and how they perform, I think the general web encyclopedia is fine, especially since most folks don't really want the math they just want to know how variable A affects variable B.  For real depth you have to go "off the grid" so to speak, by that I mean that the internet just doesn't cater to your needs.  What you need are books and research papers.  If you'd like to read up on the subject I can send you a lot of things that will lay it all out, and you can go as far into the mathematics as you like!

PS the references at the back of Qblade's buide book PDF are useful, but most will be difficult to obtain.  See if you can find the last one:

TANGLER, J.: The Nebulous Art of usingWind-Tunnel Airfoil Data for Predicting Rotor Performance, NREL/CP-500-31243, National Renewable Energy Laboratory, Golden, Colorado, 2002
Which is probably available on the NREL website somewhere.
Apart from that I would only recommend looking for the book by Martin Hansen, Aerodynamics of Wind Turbines. Earthscan, London, 2nd Edition, 2008.

All the rest seem to be about small subjects of performance correction factors, not the "big picture".
I've got a tonne more if that's not enough for you!

[opo]

Thanks for the references, I have the article now, will look into the library latter to see if they have Hansen's  book. I'm not afraid of math, I make a living out of them  . And yes please send me the papers (or references) you consider useful.

I must confess now I was partially inspired by your and Flux' write ups on "matching the blades to the alternator".

Cheers,

Octavio

[SparWeb]

Wow,
I usually scare people away with that kind of talk.

Right off the top of my head, I think you want to look through the NREL and Sandia's websites with an eye for "BEM" or "blade element theory" of course.  There is a webpage of publications (can't find the exact link right now) which get very detailed, explain the concepts and teach a lot about how to analyse the rotor.  Doing searches for the authors "Wilson, Lissaman and Walker" will turn up excellent scientific papers from the 70's that lay it all out with examples.

Attempting to find the links, and Google search has turned up a lot of recent articles that cite W,L&W, but not the actual papers....  Aha here it is:

http://wind.nrel.gov/designcodes/papers/

That's a great site to explore, plus if you want to play with software, check out WTPerf!

Have fun!
(I don't expect we'll hear from you for a few weeks, eh?)

[opo]

Thank you SparWeb, that should do it. It will take more than just a couple of weeks to digest all the info. But already I saw there is very interesting information concerning furling machines. For example in

http://wind.nrel.gov/designcodes/papers/Swift_YawedFlow.pdf

page 22, second paragraph, it is stated that, under some conditions, there could be more power available at the rotor if yawed at a positive angle than heading square onto the wind! (see graph in page 21)

Maybe that explains somewhat why some turbine builds fail to flatten the power production curve when partially furled.

Ok, too much to read..., so little time.

[SparWeb]

There are many reasons that the power curve would not flatten out.
One way is that the angle of "partial" furling is much less partial than one thinks!
I can't say much for yours, knowing so little about your turbine, but on my own I simply had to tie a ribbon to the tail to realize that the direction of the wind was VERY different from what I perceived on the ground, or expected from the direction the turbine faced.  There is always a balance of forces, such as the lift force on the tail plate, that requires the turbine to move slightly away from the wind before they take effect.  These angles can be large, and yet the turbine can still perform well because the action of the turbine on the airflow is more complicated than just deflecting the flow to the right or left.  It also slows the airflow, expands the "tunnel" of air arriving at the disk of the rotor, gives the whole mass a slight rotation, and many eddies are formed from the tips, too.  Not so simple any more!
I don't throw my hands up.  Some people are alienated by science and fluid mechanics and such things.  I love the fact that nature is so complex.  These things make the machine in my back yard have a "personality".

[opo]

Well, I wish to take a peak at the theory to see if there is anything useful for us hobbist with limited tools.

I wish also my next mill to be a theoretical exercise as much as a building exercise. Eventually I wish to build a well behaved mill from a motor conversion for example.

What I have flying now is a motor conversion with 1.3m wood blades, no twist no taper in a poor site. But it is ok for playing and learning the many bits of wind generation. I have a better site under construction where I will be playing soon.

Hows your blade matching coming up?

[WindriderNM]

I know from my days designing and racing ice boats that you reach max speed at about 105 deg off the wind. Up to 5 times wing speed. I wonder how this relates to windmill blades?

[SparWeb]

I worked on it pretty vigorously last year, but I shelved the analysis work last spring to get on with building and installing the Baldor.  I haven't returned to it since, which is not really a bad thing because once a subject like this gets overwhelming in my head I need time away from it.  Let it soak in, think through in the back of my mind, see if what I thought was right stays that way when I come back to it later.

Over the winter I have had numerous opportunities to collect performance data from the turbine I have.  This will help as a tool to "validate" what I calculate with the theory.  This seemed to be a prudent step (and one that also interests me) before going ahead and carving a set of blades that I predict to be "perfect" for the Baldor conversion.  One of the things that made me stop fussing with the theory and calculations was that I had assumptions built into the math, but no way to check them against reality.  That's where the data logger comes in.

Well, I wish to take a peak at the theory to see if there is anything useful for us hobbist with limited tools.
I wish also my next mill to be a theoretical exercise as much as a building exercise. Eventually I wish to build a well behaved mill from a motor conversion for example.
What I have flying now is a motor conversion with 1.3m wood blades, no twist no taper in a poor site. But it is ok for playing and learning the many bits of wind generation. I have a better site under construction where I will be playing soon.
Hows your blade matching coming up?

[ChrisOlson]

Anyway, jus liked to share this find. The first two comparisons I did was between the goe222 no taper no twist vs the blades I'm currently ussing, both at 4'. The windcharger type blade beat the $%&/ out of my blades.

I found that out on the tower comparing GOE222's to S809's.  If you build a generator for S809's that's a good match, remove the blades and install GOE222's of the same rotor size, the GOE222's will reduce your generator to a pile of ash.

I'm still working on some of the issues of controlling those GOE222's in higher wind speeds.  I've gotten fairly close, meaning I can now keep my 12 foot 24 volt machine under 3 kW running fully furled.
--
Chris

[MattM]

The tilted angle isn't only optimum in axial windmills.  The only vertical design I tried that spun with any decent rotational speed was tilted at 30 degrees and used flat blades rather than scoops. 

[opo]

I'm still working on some of the issues of controlling those GOE222's in higher wind speeds.  I've gotten fairly close, meaning I can now keep my 12 foot 24 volt machine under 3 kW running fully furled.
--
Chris

Hey Chris,
What are your blade parameters?
    Diameter=   (12ft?)
         Pitch=
        Chord=
     Hub Dia=


Octavio

[ChrisOlson]

Hey Chris,
What are your blade parameters?
    Diameter=   (12ft?)
         Pitch=
        Chord=
     Hub Dia=

Diameter 12.31 feet
Pitch 10°
Cord 6.25"
Hub Dia 35"
--
Chris

[opo]

Very impressive blade set up Chris. I assumed a cut in @ 3ms and obtained the following graphs


The power production curve is almost linear. There is a "saddle" in the power curve between 30 and 35 ms and then again an almost linear curve similar (as in parallel) to the 0 to 30 ms one. 

Cheers,

Octavio

[ChrisOlson]

The power production curve is almost linear. There is a "saddle" in the power curve between 30 and 35 ms and then again an almost linear curve similar (as in parallel) to the 0 to 30 ms one. 

Interesting because that's pretty much how they act on the tower too.  I'm cutting them in at 2.6 m/sec to try to keep them under control in high winds.  All I can tell you is that at anything above 40 mph with the machine running fully furled you'd better sit down, shut up and hang on because this ain't no hay ride.  I've had my 24 volt machine pushing 140 amps with the bus being pushed up to 39 volts because the dump load can't keep up, and they still don't give up.  If I manually crank the tail then they tame down.  But if there's any pressure at all steering them back into the wind they'll continue to run at well over 400 rpm with the machine furled.

I've tried a bigger tail fin, longer tail boom - still got the same problem.  Now I got a different furling setup that latches at fully furled to remove the pressure steering them back into the wind.  I'm waiting for the next big blow to see if that works.
--
Chris

[opo]

I've tried a bigger tail fin, longer tail boom - still got the same problem.  Now I got a different furling setup that latches at fully furled to remove the pressure steering them back into the wind.  I'm waiting for the next big blow to see if that works.
--
Chris

Chris,

You've probably tried this:

Since you are playing around with furling, maybe you will be able to try a yaw angle of 10 deg. That is, instead of pointing your (RoyalFab) rotor square into the wind before furling starts, point it at 10 deg in the direction of furling, and then let the mill furl as usual. By pointing the machine 10 deg off the wind your rotor will be closer to the maximum of its power curve so furling will be more effective then. Because if the machine is pointing straight into the wind and furling starts, then when the machine furls from 0 to 10 deg the rotor will be increasing its power, and only when the mill furls beyond 10 deg it will begin to loose power due to furling.

The figure of 10 deg comes from the paper (pages 97-99)

http://wind.nrel.gov/designcodes/papers/Swift_YawedFlow.pdf

I already mentioned before.

Octavio