Wind turbine, 3 or 5 blades?

[Alain G]

Since the engine was originally made for torque and the engine is probably made to turn only in one direction for maximum torque, they may have voluntarily given advance to increase this torque.

Mark the right place and try to turn the carbon holders to see if you can't increase the voltage that way.

[darwenn]

The concern is that the coals are cut to fit the shape of the rotor, they are half-moon-cut at their end, so if I change the angle I will have to re-cut the coals, I'm not sure it is a good idea if in the end it didn't change anything, especially since it wouldn't save me 10 volts, so I don't know if it's worth it. I need more volts, a lot more volts, I have to turn faster or find the miracle multiplication ratio, one that will ask me for low torque and give me the volts I expect. Well already I will see with the completed propeller and adjusted what it gives, I will put my multiplier x7 to see, I had 7,5 Volts max with it.

[Alain G]

No you don't have to cut the coals, just turn the support.

it also seems to me from the video that your rudder is not large enough and is positioned too low and is hidden by the case which probably does not position the blades correctly facing the wind.

[darwenn]

Ha yeah, it's possible Alain, I can always see to put a bigger rudder, it's not a problem, I take note that it can play indeed.

[Philippe Schutt]

Regarding the number of blades, it seems to me that it is because of the efforts on the mast that we prefer fewer blades but longer. at an equal moment of rotation, there is less thrust on the mast.
Besides, what did you use as a tube, will it hold in the storm?

[darwenn]

No worries for the mat, it's 3mm thick stainless steel tube 36 inside 42 outside, it won't break and this is what I will use when I place it in the garden at 6 meters, seal in the concrete at the base and guyed. Finally, if I get my way.

[loop]

good evening everyone

Philippe wrote

Regarding the number of blades, it seems to me that it is because of the efforts on the mast that we prefer fewer blades but longer. at an equal moment of rotation, there is less thrust on the mast.

This would be true only when stopped with a fixed timing
When the wind turbine turns, it is the surface of the disk swept by the blades that counts.
A three-bladed blade will rotate faster than a 5-bladed blade (with equal length, rope and profile), so we reach the speed of start of production more quickly and it is also more economically advantageous (an industrial blade made of composites is very expensive)

For the speed of rotation which seems limited on the Darwenn wind turbine, it seems to me that:
- The drive torque of the rotating assembly (pulleys + motor) consumes power, due to friction.
In this case, it must be checked by hand if this is not the case (the rotation is started and the rotor must make a few turns before stopping)
- The blades are not cut profiled in the most important area, that is to say the last outer third of the length.
It is imperative to thin the profile at the end of the blade so that the relative thickness does not exceed 15% (see 12% if you choose a naca 4412) of the rope.
In other words, the blade tip, if the width (rope) is for example 10 cm, the thickness of the profile must not exceed 1.5 cm.
A good three-bladed blade must have a TSR of at least 5, which means that the tangential speed at the tip of the blade is very high (100 km / h for a wind of 20 km / h). In this case, you need a studied aerodynamic profile and an impeccable surface condition.
A propeller in the form of a single plank can never reach such a speed because the drag ends up increasing faster than the lift.

We await the rest of your tests impatiently, especially since the next few days could be properly windy.

A+

[darwenn]

Thank you for your looping details, but when you say:

In this case, you must check by hand if this is not the case (we start the rotation and the rotor must make a few turns before stopping

You talk about the propeller removed, only by launching the rotor by hand, right? because yes in this case I have friction, I have no inertia. When empty, that with the bearings of the rotor bearing (without generator socket) there I have some internals of a few turns, so yes my pulley / belt assembly causes friction which surely pelanizes and I do not see a solution. ..

I will therefore thin the end of the blades in addition to thinning for the line of flight and planing so as to create on the rear part of the blades, a curved shape. And in the end find a good timing compromise. And change the gourvernail to a bigger and higher one. Try tomorrow if time permits.

[loop]

To get an idea of ​​the profile, here are some examples

http://users.swing.be/compagnons-eole/e ... tm#Profils

The Clark Y, the best known here, is missing

http://epervier.sudluberon.free.fr/spp/recueil.pdf

For thinner profiles, mechanical resistance is also involved in the design of the blades, and as in wind power the efforts are very important, security must be guaranteed by the robustness of the blades.

In terms of friction, that of the shaft of your engine / generator is inevitable, but the multiplication amplifies the fault. That's why I prefer direct training, but in your case, you have no choice.
Difficult to say if this friction is excessive, but in principle if the wind is sufficient, the critical threshold will be exceeded and the rotor will normally take its turns, unless the blades are permanently in aerodynamic stall.
Start by "working" your blades and we'll talk about it again.

A+

[Philippe Schutt]

This would be true only when stopped with a fixed timing
When the wind turbine turns, it is the surface of the disk swept by the blades that counts.

at maximum speed, yes.