Salient White Elephant

March 20, 2009

Wheel in the Sky

This is a horizontal axis machine. Imagine a giant wheel with six spokes – three upwind and three downwind:

Spoked Wheel

The spokes are airfoils. The rim simultaneously provides three functions – it is a vortex spoiler, flow accelerator, and it is an aerodynamic shroud that contains the parts of a giant ring generator. Just as the spokes of a wheel rotate with the wheel, the aerodynamic rim rotates with the turbine blades. Generator windings are embedded in the rim along its entire circumference. The permanent magnets are embedded in a component that is shaped like a 60 degree arc. (I’m not sure how many radians the arc needs to sweep. I’m just guessing it might be in the neighborhood of 60 degrees.) When the turbine isn’t turning, the 60 degree arc rests on top of the ring that carries the windings in the 6 o’clock position. The arc has wheels beneath it that regulate the small gap between the magnets and the surface of the ring that carries the windings:

Ring Generator, Wheel in the Sky

Now when the turbine rotor begins to turn, the arc with its magnets will turn as well. However, it won’t turn very far before the gravity generated counter-moment will balance the force that tends to drag it along with the (generator) rotor. At this point the machine will begin to produce electricity.

Precision Air Gap Variation

This variation employs segmented arcs that are connected end-to-end. This allows the air gap to be independently and accurately regulated for each stator segment:

Wheel in the Sky Ring Generator, Precision Air Gap Variation

Advantages and Disadvantages of Wheel in the Sky

It is unfortunate that the outer surface of the aerodynamic ring must travel at blade tip velocity. This will certainly generate a great deal of turbulence. But consider the benefits:

  • diminished blade tip vortices,
  • accelerated flow near blade tips,
  • airfoils supported at both ends (lighter, stronger airfoils),
  • low noise (six blades mean diminished rotor rpm),
  • precision direct drive generator,
  • extremely large diameter ring generator (high speed generator rotor),
  • zero torque main rotor shaft.

That’s an impressive list of benefits. Will these advantages outweigh the aerodynamic losses of the rotating rim?

By the way, it might be a good idea to combine the Wheel in the Sky and the Highly Scalable Turbine.

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