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Adriaan Kragten
Newbie
Joined: 14/10/2015
Location: NetherlandsPosts: 9 |
| Posted: 08:59am 20 Oct 2015 |
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I have studied the nice article "How to mount Extruded Blades" on this website and to my opinion the expression "the angle of attack" is used not correctly in this article. It is written: The blades work best with an angle of attack between 8 degrees and 10 degrees.
The angle of attack alfa is the angle in between the direction of the relative wind W and the zero-line of the airfoil. The blade angel beta is the angle in between the zero-line of the airfoil and the rotor plane. The angle in between the direction of the relative wind W and the rotor plane is called phi. It is valid that phi = alfa + beta (I can't write Greek letters here). So in stead of "angle of attack" one should write "blade angle".
The general aerodynamic definitions and the theory how to design windmill rotor blades are given in my public report KD 35: Rotor design and matching for horizontal axis wind turbines. A folder with the content of this report can be found on my website: www.kdwindturbines.nl at the menu KD-reports. |
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Jarbar
Senior Member
Joined: 03/02/2008
Location: AustraliaPosts: 224 |
| Posted: 01:42pm 20 Oct 2015 |
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Adriaan,
welcome to the forum. Are you looking to sell your reports,or have i missed something.
Anthony.
"Creativity is detirmined by the way you hold your tounge".My Father
"Your generation will have to correct the problems made by mine".My Grandfather.
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Adriaan Kragten
Newbie
Joined: 14/10/2015
Location: NetherlandsPosts: 9 |
| Posted: 01:00am 21 Oct 2015 |
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Most of my reports can be copied for free from my website but for some reports which have taken a long time to write them, like KD 35 or reports for which a large investment has been made like most reports of generator measurements, I ask a certain fee. An overview of all my reports and the corresponding fees is given in the folder "List public KD-reports". Every report has a rather long title which gives a good impression of the content. All reports are written in English.Edited by Adriaan Kragten 2015-10-22 |
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Downwind
Guru
Joined: 09/09/2009
Location: AustraliaPosts: 2333 |
| Posted: 01:42am 21 Oct 2015 |
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In someways its a nice offer for you to sell us information on what we share here for free as general knowledge.
Perhaps our political correctness here in not up to your standard, although we do offer information here free of charge, and for that reason im sure most people who follow the information don't really care what its called, as long as they can follow the information given, and they don't need to pay a fee to get all the Greek terms correctly applied.
With being a site that asks nothing in the line of fees or even requiring a membership to view information, this may not be your best choice to advertise your product for sale on.
Should you wish to offer members of this site free access to view your information then it would be seen as a value and not just spam.
Good luck with your venture.
Sometimes it just works |
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Adriaan Kragten
Newbie
Joined: 14/10/2015
Location: NetherlandsPosts: 9 |
| Posted: 12:08pm 21 Oct 2015 |
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Sorry Downwind but you don't read my posts carefully. I offer 35 reports and two manuals about many aspects of small wind turbines for free and 10 reports for which a certain fee has to be paid. If you you are only interested in free knowledge, you should study only my free KD-reports. But if you want to design a windmill rotor which works well, you need to have at least the basic aerodynamic knowledge of rotor design and matching given in report KD 35 and the knowledge about generators and safety systems given in for instance free reports KD 341 and KD 485. It isn't fair to call my mail spam if you have not visited my website and studied at least some of the free reports. Only very few people in the world have made that much basic knowledge about small windmills available for free as I did. |
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flc1
Senior Member
Joined: 20/11/2011
Location: New ZealandPosts: 242 |
| Posted: 01:14am 22 Oct 2015 |
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Adriaan,somtimes theory doesn't work in the real world aswell as it is sapposed to,I think most people on this site who have built there own windturbines DO have a at least the basic knowledge of rotor design etc, just woundering... have you built a windturbine ,or blades for a wind turbine?? |
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Adriaan Kragten
Newbie
Joined: 14/10/2015
Location: NetherlandsPosts: 9 |
| Posted: 08:12am 22 Oct 2015 |
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I have designed three water pumping windmills in the 15 years that I worked in the Wind Energy Group of the University of Technology Eindhoven and all these windmills were built and tested. I have designed about 20 different electricity generating windmills when I worked for my engineering office Kragten Design (starting in 1989). I have built nine of them and tested them on my testfield. If you go to the menu VIRYA-folders on my website you find several folders in which the current types are described including photo's. The rotors of all my windmills are designed using the theory as given in report KD 35. I have given many wind energy courses about the rotor design theory and report KD 35 is used in several countries because it can be understood by people with only some basic knowledge of mechanical engineering.
I doubt if many people in your group have the basic knowledge of aerodynamics, at least what I call basic knowledge. But this is only necessary if you want to design a rotor and find the optimum blade geometry for a rotor with a certain diameter, a certain number of blades, a certain design tip speed ratio and a certain airfoil. The design theory gives the optimum variation of the chord and the blade angle as a function of the radius for blades designed with the optimum lift coefficient and for blades designed with a constant chord. Examples of rotors designed with this theory are given in free reports KD 467, KD 511, KD 518, KD 571 and KD 578.
You can build a windmill without this knowledge but then you need a proven design. However, the person who has made this design should have used the required knowledge otherwise everyone is copying the same mistakes.
Designing a proper working windturbine which survives heavy storms without being damaged is not easy. The design procedure which I advice is given in a folder at the bottom of the menu KD-reports. My experience with home built windmills, designed by amateurs in The Netherlands is that most of them don't survive heavy storms where wind speeds over 25 m/s may occur. 15 years ago there was a large group op people in my neighbourhood who have built their own windmill and none of those windmills existed after three years. All my VIRYA windmills have the hinged side vane safety system which turns the rotor fluently out of the wind at high wind speeds. Most of them have been tested for more than 10 years and have survived all storms while still rotating. Only one rotor was lost because the blades have touched the tower at about 25 m/s because they were too flexible. This problem was solved by increasing the distance in between the blade tip and the tower. |
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flc1
Senior Member
Joined: 20/11/2011
Location: New ZealandPosts: 242 |
| Posted: 04:59pm 22 Oct 2015 |
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I think before you make a comment that most people on this site don't understand how to build a good windturbine, you should first check out there designs etc, and allso if you had bothered te read some of the posts here in depth, you would notice that there are a number of pilots on here,including myself, who do have at least a basic understanding of tip speeds and rotors bla bla bla,its just that we don't have to try and covince everybody that we are of superior interlect than than others here,because we know we are not,I have built a windturbine that has and will continue to survive many southern ocean storms. Maybe you should take your superior interlect somewhere else  |
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Adriaan Kragten
Newbie
Joined: 14/10/2015
Location: NetherlandsPosts: 9 |
| Posted: 09:48pm 22 Oct 2015 |
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I have not said that people one this side don't know how to build a good windmill. If they have a proper design available it is possible. But to design a rotor according to the aerodynamic theory is something different. The knowledge how to do this is difficult to obtain and to understand for people without a degree in aerodynamics. My experience with people who build their own windmills in the Netherlands is that most rotors are designed by try and error or by wrong or too much simplified theories. With only a little study one can design a rotor which functions well and for which the characteristics can be predicted. If the characteristics are known, it is also possible to match the rotor to the generator, at least if the generator characteristics have been measured.
I have started this discussion because there was a real mistake in an article on this forum. Clearly no one else has noticed this mistake other wise the article would have been changed. But I feel that my contribution to this forum isn't appreciated and I stop to give comment. |
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Clockmanfr
Guru
Joined: 23/10/2015
Location: FrancePosts: 429 |
| Posted: 10:58pm 22 Oct 2015 |
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I looked at the ‘Adriaan Kragten’ stuff and checked out his flying stuff…….
Posted on 22/09/2013……Hugh Piggott's site, ……. “Here is an invitation from Adriann Kragten to test his design ideas and develop a pumping wind turbine project. Please note that Adriaan has never built an axial flux generator, so these instructions are not like my Recipes which are based on decades of experience, but the document is very rigorous and mathematical, and covers every theoretical detail.”
For the time being I will stay with the Hugh Piggott Design, and the Dan Bartmann design.
Hugh Piggott has spent most of his Life, 35 plus years, perfecting the under 5 meter diameter Wind Turbine and releasing his knowledge to the World.
His designs are easily available and in many languages.
Hugh’s Wind Turbines are in the real World, and they are Simple to make, Work Efficiently by matching the PMG to load to blades, Extremely Robust, and very Cost Effective. Surely the, ‘Holy Grail‘, of any Machine.
yep all that vegetation will be going as winter arrives.
I have 3 off Hugh’s 3.7m diameter design flying, with No 2 & 3 having his blade design in fibreglass from my own created moulds.
My No 1 has been flying producing electricity for nearly 10 years now, and has survived Real Hurricane winds here in France, so they are definitely robust.
I do not know the bloke, and I have never met him, but Personally, I feel Hugh Piggott deserves a Medal.
Edited by Clockmanfr 2015-10-24
Everything is possible, just give me time.
3 HughP's 3.7m Wind T's (14 years). 5kW PV on 3 Trackers, (10 yrs). 21kW PV AC coupled SH GTI's. OzInverter created Grid. 1300ah 48v. |
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flc1
Senior Member
Joined: 20/11/2011
Location: New ZealandPosts: 242 |
| Posted: 05:04pm 23 Oct 2015 |
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Adriaan,You don't need to have a degree in aerodynamics to understand aerodynamics,some of the most famous inventors, scientists etc never had a degree in anything, some did not even complete highschool, there are smart people and there are people who are not smart.Just because sombody reads o few books at uni or whatever and gets the big tick at the end of it does not make them smart,having a degree means very little in my world. |
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domwild
Guru
Joined: 16/12/2005
Location: AustraliaPosts: 873 |
| Posted: 12:57pm 01 Dec 2015 |
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Adriaan,
Thanks for your comments. Personally I do not mind if you charge for some of the more time-consuming articles, seeing that you give others away free of charge.
What people are doing on this forum is copying established designs or just learning from their mistakes and improving. There is a "good feeling" to be gotten from building something and many times dearer than just buying a Chinese mill, especially if the only tool in the workshop is one big hammer!
Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.
Winston Churchill |
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