Author Topic: Design and control type h darrieus rotor  (Read 2462 times)

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andreas27885

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Design and control type h darrieus rotor
« on: March 10, 2017, 04:15:16 AM »
Hi,
I want to construct one darrieus rotor type h.
How can I limited it's Speed with mechanical Way?
Thanks

electrondady1

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Re: Design and control type h darrieus rotor
« Reply #1 on: March 10, 2017, 05:05:13 AM »
mechanical governor that adds load as speed increases

andreas27885

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Re: Design and control type h darrieus rotor
« Reply #2 on: March 10, 2017, 09:15:58 AM »
Ok.thanks.
Are there other ways mechanical or electrical?
« Last Edit: March 11, 2017, 07:58:46 AM by andreas27885 »

Adriaan Kragten

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Re: Design and control type h darrieus rotor
« Reply #3 on: March 11, 2017, 12:23:41 PM »
For a horizontal axis wind turbine you have two ways to limit the power which is generated by the rotor, turning the rotor out of the wind like it is often done for small wind turbines or pitch control of the blades like it is done for big wind turbines. For a H-Darrieus rotor there are no realistic options to limit the power which is generated by the rotor. The only thing you can do it to use a strong mechanical brake which brings the rotor to a stand still when the wind speeds are too high. Using a mechanical brake for maintaining a constant high rotational speed will finally burn the brake. Limitation of the rotational speed by use of a strong generator will fail at very high wind speeds because there will always be a wind speed for which the rotor torque will be larger than the peak torque of the generator. Once this wind speed is reached, the generator will no longer be able to maintain the maximum rotational speed. So the rotor will run at very high rotational speeds and finally the generator will burn. The problem that the maximum rotor power can't be limited is one of the reasons why I advice not to start with Darrrieus rotors. Other reasons are given in my free public report KD 215.

A method to find the optimum chord for a H-Darrieus rotor with a certain rotor diameter D and three blades is given in my free public report KD 601. This report also describes a method to make a H-Darrieus rotor self starting without loosing the advantage that it accepts wind from any direction. The idea isn't tested and the problem that the maximum rotor power can't be limited isn't solved for this version of a H-Darrieus rotor.

Adriaan Kragten

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Re: Design and control type h darrieus rotor
« Reply #4 on: March 12, 2017, 07:09:54 AM »
I have travelled a lot by bike through Europe and I have seen many Darrieus rotors but never one which was running. If it is possible to solve all its intrinsic problems someone would have done it. Big companies like Fokker and Vestas have done research to develop this concept but finally gave up. So I think that non professionals are certainly not able to solve all the problems.

Adriaan Kragten

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Re: Design and control type h darrieus rotor
« Reply #5 on: March 13, 2017, 02:42:32 AM »
It depends on the diameters and the load if a Savonius rotor works as a brake. A Savonius rotor has an optimum tip speed ratio of about 1 and a H-Darrieus rotor has an optimum tip speed ratio of about 4. So if the diameter of the H-Darrieus rotor is four times the diameter of the Savonius rotor, both rotors run on the optimum tip speed ratio if the load is correct. However, a twin Savonius rotor with a diameter of only 1/4 of that of the H-Darrieus rotor will have a torque level which probably isn't large enough to bridge the part of the Cq-lambda curve of the H-Darrieus rotor for which the Cq-value is negative. So generally one takes larger twin Savonius rotors and then the optimum lambda for both rotors is no longer realised for the same rotational speed. Then the Savonius rotors will work as a brake if the H-Darrieus rotor runs above a certain tip speed ratio. But the ratio of the rotor diameters can be chosen such that the Savonius rotor is running just unloaded if the H-Darrieus rotor is running at the optimum tip speed ratio. You should know the Cp-lamba or Cq-lambda curves of both the H-Darrieus rotor and the twin Savonius rotors to find the ratio of the rotor diameters for which this is realised. For this ratio, the total height of the upper and the lower Savonius rotor must be chosen that large that the torque level of both Savonius rotors together is large enough to bridge the part of the Cq-lambda curve of the H-Darrieus rotor for which the Cq-value is negative.

Bruce S

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Re: Design and control type h darrieus rotor
« Reply #6 on: March 13, 2017, 10:00:05 AM »
That works for me.
Thanks
A kind word often goes unsaid BUT never goes unheard

electrondady1

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Re: Design and control type h darrieus rotor
« Reply #7 on: March 13, 2017, 10:30:23 AM »
apis21,  thanks.
 there was a lot of good info posted there over the years as it was open source like field lines is but  towards the end, a couple of the members who had learned how to make windmill there wanted to go commercial and would not share their research so along with the admin  the site became a platform for their product. didn't need to be a part of that.

mbouwer

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Re: Design and control type h darrieus rotor
« Reply #8 on: March 15, 2017, 06:00:57 AM »
Electrondady,

Is it possible to share details about your vawts with us?


apis21

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Re: Design and control type h darrieus rotor
« Reply #9 on: March 15, 2017, 02:05:42 PM »
.
« Last Edit: March 15, 2017, 10:27:47 PM by apis21 »

kitestrings

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Re: Design and control type h darrieus rotor
« Reply #10 on: March 15, 2017, 06:56:58 PM »
Did something happen here when I blinked?  I'd been loosely following this thread.  I know that I post once, maybe twice on it.  I know SparW posted on it.  I know some of the mods did and there was discussion regarding past biases regarding VAWTS.  Where'd it all go?  Big brother...?

JW

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Re: Design and control type h darrieus rotor
« Reply #11 on: March 15, 2017, 07:10:38 PM »
The topic was getting too hostile.

We had the original topic starter(member) and a newbie(member) so the thread was hijacked by the newbie.

we sorted it all out no harm no foul. But a lot of posts were deleted.

Hopefully the original topic starter will chime in at some point

Jeremy

kitestrings

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Re: Design and control type h darrieus rotor
« Reply #12 on: March 15, 2017, 07:22:45 PM »
I'm confused J, because I thought the OP was with regard to VAWT Darrieus design, governing, self-starting...it seems like there was some constructive comments being shared.  Seems like the foul is the loss of that exchange.  ~ks

electrondady1

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Re: Design and control type h darrieus rotor
« Reply #13 on: March 16, 2017, 06:10:39 AM »
 strange, mbouwer asked for details about my mill.  i responded  i couldn't divulge details  at this time but would be  happy to talk about concepts.  looks like apis21 has withdrawn his posts. too bad they were very handy interactive design tools.  but how did mine disappear?
« Last Edit: March 16, 2017, 06:25:49 AM by electrondady1 »

JW

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Re: Design and control type h darrieus rotor
« Reply #14 on: March 16, 2017, 06:32:30 AM »
Its my fault. I deleted the posts that are missing.

Adriaan Kragten

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Re: Design and control type h darrieus rotor
« Reply #15 on: March 22, 2017, 02:21:44 AM »
A H-Darrieus rotor can be made self starting if the blades are oscillating in such a way that the front blade has a positive blade angle and that the back blade has a negative blade angle. This can be realised by a lever connected to each blade and to an eccentric. The line through the rotor axis and the eccentric axis must be kept in parallel to the wind direction. But now the main advantage, that the rotor accepts wind from any direction is lost. So you need a vane or another mechanism to realise correct position of the eccentric. If the position of the eccentric is placed such that the line through the rotor axis and the eccentric axis is perpendicular to the wind direction, the angles of attack are completely wrong and it might be possible to use this position of the eccentric as a way to limit the generated rotor power. But oscillating blades makes the rotor a lot more complicated and expensive than a normal H-Darrieus rotor with fixed blades. Solving one of the problems of a H-Darrieus rotor often creates a new other problem.

Using oscillating blades is about similar to the Voith Schneider ship propulsion. A very nice description of the functioning of the Voith Schneider system is given on: www.voithturbo.de/545950.htm

JW

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Re: Design and control type h darrieus rotor
« Reply #16 on: March 22, 2017, 07:31:18 PM »
I wont be Moderating this thread. Its nice to see the original poster chime back in. The other guy apis21 was not the original poster and only commented on this thread.


electrondady1

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Re: Design and control type h darrieus rotor
« Reply #17 on: March 23, 2017, 05:43:12 AM »
my computer shows the o.p. was andreas27885 from Cyprus.
looking for a speed control for a Darius mill.
hasn't posted since .

JW

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Re: Design and control type h darrieus rotor
« Reply #18 on: March 23, 2017, 02:55:09 PM »
Ya I screwed up