Efficient design for wind turbine blades?

[Isiah]

Which blade design on a wind turbine would be most effective in spinning? And how many blades? Flat blades? Curved in towards the wind source? Or anything else? Please help, this is for a project im doing for fun, thus it is fairly small scale (the turbine diameter would be around a foot or so).

 

[steveh]

Look up savonious rotor.This might give you some ideas.(spelling might not be right)

 

[jpopelish]

The problem is very similar to the design of an airplane wing, except that the design has to shift from hub to tip to account for the increasing speed across the air stream as the distance from the hub increases. Think of the turbine blade as a wing that produces its lift in the direction that produces turning force. You want to maximize that force while minimizing drag forces in the direction of the air flow. So the optimum shape is an air foil similar to a wing, but turned so that the blade moves away from the concave side of the wing as it 'lifts' around the hub. Since the rotational velocity is low near the hub, the wing needs to be thick and wide, there. At the tip, the rotational velocity is high, so the wing needs to be thin and narrow out there. This is very similar to how propeller blades are shaped, except, there, you supply the rotation and the blade makes the wind.

In principle, one blade with a counter weight could work as well as a higher number of blades, except that the counter weight only balances the weight of the blade, not the drag forces on it caused by the passing wind. So two blades are usually the lowest practical number. Then you have ot consider that every time a blade passes in front of the tower, its air flow is disturbed, and if there are only two blades, that is a big power drop, twice per rotation. For this reason, three blades are probably most common. But a higher number of blades can work, too, but this usually increases the cost more than it smooths the performance.

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Regards,

John Popelish