Need help with wind turbine development

[darwenn]

Hello everyone, so for those who followed my wind turbine construction, this one is finished. Made with a 24v 1000w generator from future energy. Completely rebuilt with feathering and pivot on bearing. Everything works fine, charging batteries etc ... but I have a problem. and not the least. My propeller stalls quickly even in winds of 60 to 70kmh, which means that I only have good rotational speed intermittently and without feathering being involved. The problem is the Propeller. some concerns about vibration even if the propeller is perfectly symmetrical, the balance is surely not perfect although all the geometry is correct, it does not reverse, stops in any position, between axes ok etc ... no worries on this side there I did not do it randomly either, it is essential.

I know it is badly designed but I can't get out of it. It is made of reinforced sheet 0,5 on the back, fixed on a flat iron 3mm by 30 and on a 10mm plywood hub, diameter 30mm. Here is a photo of the shape of the blade according to photos on the net, I think the shape is correct in any case. Here are the dimensions of a blade

Length: 85cm (wingspan 1,70)
Wide width: 120mm
Blade tip width: 40mm:

The worry of dropping out in my opinion, is that the blades are too flexible, too flexible and that is what leads net, my loss of performance. I suppose that a propeller must be perfectly rigid, do not bend under any circumstances, is that it? . Can you confirm it to me ? is my wingspan insufficient? the widths?

If yes, I plan to make the same blades in 1mm sheet, on flat iron 5mm thick by 40 or 50mm wide mounted on 10mm aluminum hubs.

I came back in 3 blades, why? because after many tests I observed this.

A 5 blade, starts in a weaker wind, offers better torque but in the end with a lower rotation speed than a 3 blade and lower efficiency. I observed it by the measurements of tensions.

A 3 blade, requires a little stronger wind, offers less torque but a significantly higher speed of rotation and a much better yield going up to double on the tensions measured by identical wind. Here is my conclusion. So I opt for a three-blade after my many tests.

Thank you for your advice, I need a perfectly reliable propeller with a very good performance. My current propeller works but picks up too quickly. I know that you don't make a propeller like that, that it requires very precise rules, and that's why I take all good advice.

[elephant]

would it not be once again the turbulence of the roof?

[loop]

Bonjour,

Clearly, if it is the rotor in photo that you use, its setting is much too strong.
Start by reducing the angle of incidence by slightly tilting the blade (leading edge must be more "in the wind" than the trailing edge)
a normal setting for a tsr of 6 is 4 °
There, with the profile you have chosen, you are closer to -4 °
So stall guaranteed as soon as the alternator goes into action.
Experiment with several calibrations, starting from the strongest
You stop when you no longer gain power and the rotation speed becomes oscillating.

A+

[darwenn]

For Elephant, not there the wind turbine has been moved since early August, so no worries with the roofs.

Looping so you advise me to reduce the curve by opening it is that it? I had already made a test by opening it clearly almost at the level of the rotor and it was worse, it hardly started any more, I had perhaps too open, but I think that my propeller is too flexible in strong wind , I should make it more rigid. I don't really understand the concept of TSR or how it is calculated and what it represents ... i will watch on google

I will do other tests by modifying the timing, thank you in any case.

[loop]

Hello

A small image to help you visualize the different factors that come into play

A+

[loop]

Darwenn, given the shape you have given to the profile of the blade, your setting is bad.
On the attached sketch I represented the hollow profile in purple, and here is what it looks like.
Reminder, the aerodynamic stall occurs for an angle of incidence greater than 15 ° / 18 °.
But if the setting is too strong, as in my first image (deliberately exaggerated) the TSR will level off at a low value, so the speed of rotation (i.e. the speed of the blade tip) will never reach 5 or 6 times (see plus) wind speed.

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[darwenn]

Thank you, here is which should already help me a lot, I can't find anything explicit on the net, just relating to airplane propeller blades. Thank you for these explanations. There's more than that because now I only have that for everything to work, a reliable propeller.

[darwenn]

By cons why tell me that my angle should be 4 degrees while yours is 20. I measure 18 ° on your photo with a reporteur. Your pitch angle is 18 °.

[darwenn]

Here's how I did it this morning. I find myself in a configuration that indeed I had never tried and my propeller in more mouth. I have already returned 3 blades from my 5 blades which worked well and which I had profiled with the plane. Then I removed the offset I had with the blade attachments to bring them back in the extension of the rotation plane. Then the looping explanations allowed me to better understand the propeller diagrams that I could find. I chose a setting angle of 13 ° and drew to scale what I did.

Blade length: 75cm
At widest: 135mm
at blade tip: 55mm
At the thickest leading edge: 10mm
At least thick trailing edge: 4mm



Correctly set the center lines, checked the balance everything is ok. All that's missing is the wind, completely absent this morning. as if by chance.

Here are other photos after modification.

[loop]

Hi Darwenn

In my blade setting image, the latter is deliberately exaggerated.

On your sketch, the profile is upside down, although in your photos, the assembly seems to be correct.
I made appear some inscriptions on your last image below.

A+