Author Topic: free KD-reports and manuals  (Read 5896 times)

0 Members and 1 Guest are viewing this topic.

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
free KD-reports and manuals
« on: May 09, 2016, 02:53:07 AM »
At the menu "KD-reports" of my website www.kdwindturbines.nl you find more than 50 English written KD-reports which can be copied for free. These reports deal with different aspects of small wind turbines like rotor design and matching, airfoil characteristics, PM-generators and measurements, safety systems and water pumping. The folder at the top of the menu KD-reports gives an overview of all public KD-reports. Each report has a rather long tittle which gives a good impression of the content. At the bottom of the list with KD-reports you find four manuals of small wind turbines including detailled drawings. At the menu "VIRYA-folders" you find a folder which gives detailled information about these free VIRYA-wind turbines. At the menu "Home" you find a folder of my engineering office Kragten Design (KD), my curriculum vitae and a film (in Dutch) where I am interviewed about my VIRYA-windmills.

Bruce S

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 5370
  • Country: us
  • USA
Re: free KD-reports and manuals
« Reply #1 on: May 09, 2016, 09:11:52 AM »
---BEGIN GM MODE---
I would respectfully ask that you be very careful of the "licensing you speak about for the larger diameter 'mills.
The free part is very nice, the write up that I've already read are nice, however, if someone does complain about asking for a license and IF you're asking for money as is said in the April 2016 folder.
We will need to ask you to remove those. 
OR at the very least, explain in this post , what the license is in detail.
---END GM MODE---
I know you will understand our stance on this.
Bruce S

A kind word often goes unsaid BUT never goes unheard

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #2 on: May 10, 2016, 02:46:59 AM »
This post was not meant to advertise for my larger VIRYA-windmils for which a licence is required. I have only referred to the folder of the smaller types which can be built without a licence. Originally my engineering office Kragten Design was a professional company and I needed some income out of it but I am retired now and this is no longer necessary. About half a year ago I therefore decided to make all the public KD-reports available for free and also some designs of the smaller windmill types. I have certain good reasons to not make the bigger designs availble for free. So I thought that mentioning what is availble for free is not in conflict with the policy of your website. At this moment most of my attention goes to developing countries and people from those countries always get free support.

DamonHD

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 4125
  • Country: gb
    • Earth Notes
Re: free KD-reports and manuals
« Reply #3 on: May 10, 2016, 03:14:14 AM »
Thank you for the explanation.

Rgds

Damon
Podcast: https://www.earth.org.uk/SECTION_podcast.html

@DamonHD@mastodon.social

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: free KD-reports and manuals
« Reply #4 on: May 11, 2016, 11:49:47 PM »
Adriaan,
Well written reports and great ideas explored very thoroughly - and I've only read 3 of them so far!

Thank you for bring all of this work to our attention.  There's a lot to read there.

Have you built the 34-pole generator that you described in some of your reports yet?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #5 on: May 12, 2016, 03:28:45 PM »
The 34-pole PM-generator is described in public report KD 580 and it makes use of a stator with 36 slots. It has 34 * 36 / 2 = 612 preference positions per revolution. I have not built this generator. However, I have built a 22-pole PM-generator using a stator with 24 slots. This generator has 22 * 24  / 2 = 264 preference positions per revolution. If the armature is rotated slowly, one feels a light fluctuation of the sticking torque. The number of preference positions for a 34-pole PM-generator is a factor 612 / 264 = 2.318 higher than for a 22-pole PM-generator and therefore the preference positions will be almost gone for a 34-pole generator. So I expect that there will be no starting problems for a 34-pole PM-generator if the generator is used in combination with a windmill rotor with a low starting torque coefficient. This is one reason why report KD 580 is made public and why report KD 553, in which the tests with the 22-pole generator are described, is not made public. The other reason is that the 22-pole generator was developed in co-operation with an Indian company and that therefore it is confidential.

It might be that people don't know where to start if they want to study my KD-reports. I advise to start with the reports which give general information and one can best take the following sequence:
1) Note: Developing procedure of a range of wind turbines (1 page, at the bottom of the list of KD-reports).
2) KD 378: Basic knowledge about electrical, chemical, mechanical, potential and kinetic energy to understand literature about the generation of energy by small windmills (15 pages).
3) KD 35: Rotor design and matching for horizontal axis wind turbines (62 pages) + KD 196: Questions and answers about KD 35 (12 pages).
4) KD 485: Safety systems for small wind turbines which turn the rotor out of the wind at high wind speeds (24 pages).
5) KD 341: Development of the permanent magnet (PM) generators of the VIRYA windmills (14 pages).
6) Manual of electricity generating windmill VIRYA-1.36 (15 pages).
7) KD 571: Development of an 8-pole, 3-phase axial flux permanent magnet generator for the VIRYA-1.36 windmill -------, design report of the rotor ----- (19 pages).

In the reference of each of these reports you find other KD-reports which give detailed information about a certain subject. 

I get many questions from people who want to build vertical axis wind turbines but I don't like those windmills. The reasons why, are explained in KD 215 and KD 601 for Darrieus rotors, in KD 416 for drag machines, in KD 417 for the rotating blade turbine and in KD 599 for Savonius rotors. If people still want to build them after reading these reports, I wish them all luck but I don't want to spend time in discussions about VAWT's.

Mary B

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 3169
Re: free KD-reports and manuals
« Reply #6 on: May 12, 2016, 07:46:03 PM »
A description of each report on the download page would be a massive help!

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #7 on: May 13, 2016, 03:22:08 AM »
The first folder at the menu KD-reports gives an overview of all public KD-reports. The title of each report is rather long and gives a good impression of the content. This must be enough to decide if the report contains information in which you might be interested.

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: free KD-reports and manuals
« Reply #8 on: May 23, 2016, 11:29:36 AM »
Adriaan,
I found some time to read further and was rewarded by finding #571 and 35 again.

Since most of the turbines I see on your site have aluminum blades i am curious about your experience with those.  There is a bias in the public eye, as far as I have seen, that prefers smooth aerodynamic shapes and prejudiced against simpler shapes, such as aluminum plate.  As a turbine builder and designer you have clearly become aware that the difference doesn't matter, and chose aluminum, despite the force.of public percption.

How did you overcome this bias?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #9 on: May 31, 2016, 04:14:13 PM »
I use aluminium blades only in the two smallest designs of the VIRYA-1 and the VIRYA-1.04. The reason is that the generators of these wind turbines have a 9.5 mm bicycle shaft with thread on it and the shaft is therefore rather weak. The highest bending moment in the shaft is caused by the gyroscopic moment and this moment is proportional to the moment of inertia of the rotor. I thought that only for aluminium blades, the gyroscopic moment can be made small enough. Normally I don't advice to use aluminium because it is sensible to fatigue.

But I use cambered stainless steel or galvanised steel blades in my medium size windmills and therefore one might have the same doubts about the aerodynamic quality of the airfoil. The maximum power coefficient Cp depends very much on the minimum Cd/Cl ratio of the airfoil (see KD 35 chapter 4.3) and the miniumum Cd/Cl ratio depends strongly on the airfoil camber. In my report KD 398 I give the aerodynamic characteristics for three different cambers 7.14 %, 10 % and 12.5 %. If you compare the Cd/Cl curves for different cambers, you will see that only for 7.14 % camber, the miniumum Cd/Cl ratio is low enough (0.03) to expect an acceptable high maxiumum Cp for a fast running rotor. So for all my rotors I use 7.14 % camber. From my calculations of different 2-bladed rotors with a constant chord and a linear twist I have found that a maximum Cp of 0.38 is possible. I have measured a rotor with a tapered chord and a cambered airfoil in the open wind tunnel of UT-Delft and found a maximum Cp of more than 0.4 but rotor blades with a constant chord are much easier to manufacture and therefore a somewhat lower maximum Cp for a rotor with constant chord blades is acceptable.

My bigger windmills have wooden blades with a constant chord and a constant blade angle (so no twist) and a Gö 623 or Gö 711 airfoil. The minimum Cd/Cl ratio for these airfoils is about 0.02 (depending on the Reynolds value) and the maximum Cp is in between 0.4 and 0.42. For rotors designed with an optimum lift coefficient, resulting in increase of the chord and the blade angle at decreasing radius, the maximum power coefficient is about 0.45 if the Reynolds values are high enough but these blades are much more difficult to manufacture from massive wood and much more wood is needed. A big advantage of a constant chord, not twisted wooden blade is that the back side of the blade can be manufactured using a rotating cutter with the airfoil shape in it.

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: free KD-reports and manuals
« Reply #10 on: May 31, 2016, 11:24:23 PM »
Indeed, it is true that the gains in efficiency get smaller and smaller - and the increased effort to make an aerodynamically "perfect" airfoil cannot be justified when a flat sheet-metal blade will suffice.

But, the life of a wind turbine is only beginning when it leaves the factory.  What to the purchasers say?  Do they approach you with preconceived ideas about the shape of the blades?  Do you have to break this down for them, with proof or persuasion?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #11 on: June 01, 2016, 07:44:27 AM »
During the last 10 years my focus was on developing countries and people from those countries don't have a fixed idea of how rotor blades should look like. The most important aspect for them is that the windmill can be manufactured with non sophisticated machines. Cutting a piece of sheet and camber it is much simpler than making blades from polyester or carbon fiber using a mould like it is done for blades of big wind turbines.

But using the 7.14 % cambered sheet airfoil also has its limitations. An important disadvantage is that the torsion stiffness becomes too low if the sheet thickness is chosen too small. A too low torsion stiffness makes the blade sensible to flutter at high tip speeds. If the blade thickness is 2 mm, the maximum free blade length can be 0.8 m. Rotors with blades with cambered sheet airfoils are more heavy than rotors with massive wooden blades of the same rotor diameter and design tip speed ratio. Another aspect is that the noise production is higher because of the sharp airfoil nose and only acceptable if the design tip speed ratio is chosen not higher than about 4.5 and if the generator is loading the rotor strong enough at high wind speeds. 

SparWeb

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 5452
  • Country: ca
    • Wind Turbine Project Field Notes
Re: free KD-reports and manuals
« Reply #12 on: June 08, 2016, 02:08:23 PM »
Adriaan,
Thank you for for that perspective.  Yes it does indeed depend on where one gets the "fixed ideas".  In fact, it's another case where we designers can arrive with our own fixed ideas, and apply them to an environment where it's not needed, or worse, needlessly complicated.

7.14% camber is very specific...  1cm camber / 14cm chord = 0.0714 ?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #13 on: June 08, 2016, 04:35:46 PM »
The measurements for 7.14 % camber have originally been performed by Imperial College. In don't know why they have choosen the strange value of 7.14 % and not 7 % but I follow their definition. The camber is defined as the ratio in between the airfoil thickness at the heartline, devided by the chord times 100 %. Because of the camber, the chord is a little smaller than the non cambered sheet width. If the sheet width is 100 mm, the chord is 98.660 mm and the thickness is 7.055 mm for 7.14 % camber. In chapter 5 of KD 398 I give the formulas for the airfoil geometry for three different cambers and I have calculated all critical measures for a sheet width of 100 mm. In chapter 6 of KD 398 I give the formulas for the bending moment of resistance W, the bending moment of inertia I and the position of the neutral line for bending.

As I said before, a fast rotating cambered sheet airfoil is sensible for flutter if the sheet thickness is choosen too low. Flutter is a combined torsion-bending vibration. Flutter is mainly caused by a too low torsion stiffness. For a cambered sheet, the torsion stiffness is proportional the the cube of the thickness if the thickness is small with respect to the sheet width. The torsion stiffness is independent of the rotational speed. However, the bending stiffness increases by increase of the rotational speed because the centrifugal force in the blade has a tendency to bend the blade frontwards. The blade has a certain natural frequency for bending and a certain natural frequency for torsion. For a non rotating rotor, the natural frequency for bending is much lower than for torsion but if the rotor speed increases, the nature frequency for bending also increases. Flutter happens if both natural frequencies become equal. This is a very sudden effect and I have measured it long ago in the wind tunnel for an unloadred rotor with slender cambered blades. Suddenly the rotor becomes very noisy and if you look at the rotor from the side, you see that the rotor becomes much thicker at the tip. It is an oscillating effect because the airfoil drag becomes very large if the blade is fluttering and this reduces the rotational speed below the flutter speed. Flutter may also happen for unloaded slender wooden blades at high tip speeds. A fluttering wooden blade can be destroyed within some minutes and you get many cracks in the length direction of the blade.

Adriaan Kragten

  • Hero Member
  • *****
  • Posts: 1154
  • Country: nl
Re: free KD-reports and manuals
« Reply #14 on: June 13, 2016, 02:55:30 AM »
I got a private e-mail from someone who asks me if I know were to find building plans. As I have said in my first post, you find manuals of some small VIRYA wind turbines at the bottom of the list of KD-reports on my website www.kdwindturbines.nl. There is a separate folder of these five windmills which you find at the menu VIRYA-folders. A manual contains detailled drawings of all windmill components for the VIRYA-1.04 and the VIRYA-1.36. The VIRYA-1.04 uses a bicycle hub dynamo. Report KD 608 gives the drawings of an alternative axial flux generator and a 2-bladed rotor for the VIRYA-1. Separate from the manual, there is a design report available of the rotor and the generator for each windmill. For the two biggest free designs, the VIRYA-1.66 and the VIRYA-2.2 only the drawings of the rotor and the generator are included in the manual. You have to design the head and the tower yourself but this is not really difficult if you scale up the geometry of the VIRYA-1.36.