Wind turbine blades / fan

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Grelinette
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Wind turbine blades / fan




by Grelinette » 11/08/15, 14:22

While dismantling as a fan I wondered why the blades of fans, except those that are fixed to the ceiling, had blades very different from those of wind turbines.
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There is undoubtedly a question of space optimized for the fans, or perhaps of necessary torque for the wind turbines, but I imagine that the surface beating the wind, which is important on a pale fan, also plays a role. for recovering energy from moving air, in which case a large wind turbine with fan blades should have an attractive performance? ...
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by chatelot16 » 11/08/15, 14:57

the fans are not optimized for efficiency but for silence
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by Christophe » 11/08/15, 18:18

Yes, I think it's a story of compromise between flow (= efficiency) / rotation speed (= noise) / size (= manufacturing cost) ...

Consumption (= operating cost) is surely not one of the first criteria for designing a fan ...

The middle one looks a lot like a boat propeller ...

also plays a role in recovering energy from the moving air, in which case a large wind turbine with fan blades should have an interesting performance? ...


No I don't think so (but I didn't follow your whole idea .. ??): the best aerodynamic efficiency is obtained with the finest propellers / wings (since a propeller is a wing) ... to limit drag and the longer a wing chord (= wing width), the more drag there is.

ps: are the ceiling fan wings a drop like a plane propeller? I never paid attention ...
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by Grelinette » 11/08/15, 19:37

Christophe wrote:
also plays a role in recovering energy from the moving air, in which case a large wind turbine with fan blades should have an interesting performance? ...


No I don't think so (but I didn't follow your whole idea .. ??).

The principle of a pale wind turbine is to recover the kinetic energy of the wind, in other words, the mass of air which moves and strikes the blades of the wind turbine. Thus, the larger a wind turbine, the larger its blades have a large surface area and recover energy.

But in this logic, a pale fan type, certainly shorter (therefore also less drag!), But with a very large surface therefore in contact with more air ...

The question can also arise when comparing a wind generator of electricity (few pale, long and fine) and a pumping wind turbine (many pale, fine also elsewhere).
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In this case (pumping) the torque is increased by the number of blades which increases the surface area in the wind.

Would less blades but larger, like those of a fan, have the same performance?
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by chatelot16 » 11/08/15, 19:52

this type of wind turbine is old and is not optimum at all

current wind turbines with their fine blades are as efficient as a solid disc when they rotate at the right speed

big advantage just change the pitch to lose the equivalence of the full disc and support the wind and storm garnd

the wind turbine with a large number of blades that you are showing must be very solid to withstand high winds, not easy and not optimum

the current large wind turbines are not really the result of experience

the wind turbines to feed the cows were of this type ... in high winds they got in the way which did not necessarily prevent being demolished and no longer produced anything, modern wind turbines can adapt the pace to the wind and continue to produce
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by Remundo » 11/08/15, 20:12

there are 3 things to notice!

1) a wind turbine is not a propeller: the wind turbine is a receiver: it is the wind which makes it turn while slowing down, whereas a propeller is propellant: it is it which accelerates the wind.

2) for everything that is fan or even propeller, the thrust is worth the mass air flow x speed variation between upstream and downstream

3) for the same air flow, the longer the blades, the slower it turns with more torque, the shorter the blades, the faster it turns with less torque.

Thus for a wind turbine, a maximum torque is sought for a low speed of rotation. The drag of the blades must be as low as possible: we therefore design long blades very tapered, generating the maximum lift

And for a fan, there is an electric motor with low torque and high speed of rotation: we therefore design massive blades, of small radius, which maximize the air flow and its speed variation.

Indeed, the propulsion efficiency is not at all a priority for the fans, it is different for the propellers of ship or plane, in particular if one wishes economic displacements.

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by Remundo » 11/08/15, 20:30

chatelot16 wrote:the wind turbines to feed the cows were of this type ... in high winds they got in the way which did not necessarily prevent being demolished and no longer produced anything, modern wind turbines can adapt the pace to the wind and continue to produce

Good comments Chatelot,

but it should also be noted that pumping wind turbines rather exploit low wind speeds. In this range, the "sloping plate facing the wind" is more responsive than the tapered three-bladed wind turbines.

In fact, these pumping wind turbines operate on the impact of the wind (better on low speeds), while three-bladed wind turbines exploit its lift (better on high speeds).

Mecaflux is very complicated, and even if we can make calculations, nothing can replace real tests.
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by Grelinette » 11/08/15, 21:38

Thank you for your explanations.

To return to the old pumping wind turbines, in my region where the terrible breathtaking mistral regularly blows, there are still many very old wind turbines abandoned in the fields and which are still spinning!

They're all rusty, creaking all day long, but still spinning. One of my friends bought a piece of land that included one, he dismantled it to prevent it from falling on his head, and the most amazing thing is that some of the pieces are made of leather!

There is one by the side of a road that I take regularly and each time I see it, I tell myself that it turns like that, in the void, probably for decades and that it will still turn surely long time.
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by Grelinette » 11/08/15, 22:00

... and the propeller of the future, isn't it curious: Image


http://www.dailymotion.com/video/x8z8c9 ... futur_tech

source: http://www.dailymotion.com/popular/user/onera/1
(Very interesting what is presented on this site)
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by chatelot16 » 11/08/15, 22:19

How many water lilies does it take to turn this kind of propeller?
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