Rotor Blades 7 - Number of Rotor Blade
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| Anzahl der Teile | 8 | |
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| Lizenz | CC-Namensnennung - Weitergabe unter gleichen Bedingungen 4.0 International: Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben. | |
| Identifikatoren | 10.5446/64918 (DOI) | |
| Herausgeber | 014nnvj65 (ROR) | |
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00:00
DiagrammComputeranimation
00:12
Besprechung/Interview
01:19
Computeranimation
02:51
ComputeranimationVorlesung/Konferenz
Transkript: Englisch(automatisch erzeugt)
00:13
Hello and welcome. In this video, we will talk now about the number of rotor blades that is best suited for a wind turbine.
00:22
Hannah, I do not understand why we at all should talk about the number of rotor blades. I remember, according to Betts, this power from one rotor blade element is not dependent on the number of rotor blades. So, the power is just 16 divided by 27 times one half the air density times the wind velocity to the 3 and then times 2 pr dr.
00:48
There is nothing mentioned of number of rotor blades. Yes, that is correct. The maximum power according to Betts is independent from the number of rotor blades. But the actual power, however, depends on the number of rotor blades.
01:04
It is calculated by the number of rotor blades times the circumferential velocity u times the tangential force f t, which shows in the direction of the velocity u. In this graph, you can see the relation between the number of rotor blades z, the mechanical power p and the tip speed ratio lambda.
01:29
You can see the number of rotor blades z on the left y-axis and the tip speed ratio lambda on the right y-axis. It is visible that the mechanical power increases with increasing number of rotor
01:44
blades, but the tip speed ratio decreases with increasing number of rotor blades. The tip speed ratio multiplied with the number of rotor blades is constant in all cases shown in the graph. And when regarding the mechanical power, you can see that an enhancement of one to two rotor blades leads to a
02:08
higher increase of the mechanical power than an enhancement of two to three rotor blades or three to four rotor blades. The range of the optimal tip speed ratio lambda for the dimensioning of
02:22
rotor with different number of blades differs for different number of rotor blades. For three blade rotors, the number is between seven and eight, and for two blade rotors, it is approximately ten. In theory, the power coefficient increases with increasing number of rotor blades.
02:44
But a high rotor blade density leads to a complicated aerodynamic flow distribution. And that's the reason why nowadays we only have wind turbines with three rotor blades. In very few exceptions, we also have two-bladed ones, but that's only an exception.
03:04
The reason why that, for an additional rotor blade, we have to complete costs of a further rotor blade, but only a very small gain in additional power. And that's the reason why nowadays it's only three-bladed rotor blades. When we consider one or two-bladed rotor blades, then we need to say in past we already had such wind turbines with one or two rotor blades,
03:32
but that had the consequence of higher dynamic stress, we have higher noise emissions due to higher speed tip ratios,
03:41
and also the turbulent optical effect is considered by the people as not that convenient. And so, the last video in this series, we have a few more general aspects for rotor blade design. Thank you very much.
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