Salient White Elephant

March 2, 2009

Wind Turbine Flow Accelerator for Downwind Rotor

Filed under: Wind Turbine Auxilliary Devices — Tags: , , , , — Salient White Elephant @ 10:46 am

wind-turbine-flow-accelerator-for-downwind-rotor

The shroud and the cone are connected. They form a teardrop shaped unit called the “flow accelerator”. The accelerator is supported by rods that are not seen in the diagram because they are inside the accelerator. These supporting rods are connected to the extended rotor shaft in a way that allows the accelerator to rotate about the extended rotor shaft. This allows the rotor to turn while the accelerator remains more or less stationary. Wind accelerates as it veers to avoid the flow accelerator. This causes the wind that passes through the outer portions of the rotor blades (the portions furthest from the rotor shaft) to be traveling faster than it would have been traveling had the accelerator not been present. In this way, the accelerator prevents air from “escaping” through the “aerodynamic doughnut hole” in the center of the rotor, and directs it instead to the outer sections of the blades where its energy can be extracted.  The flow accelerator must be carefully designed not to produce turbulence. This is so because turbulence can rob the rotor of some of its energy harvesting capabilities.

The size of the annular airfoil like ring is exaggerated in the diagram above. A practical design will minimize the size of this component, and will maximize the size of the windsock. This allows the sock to open up so that it has a near zero drag profile when the turbine is shut down for high wind conditions.

The flow accelerator might be a good combination with a rotor that has variable length blades. As the blades are extended to sweep more area, the section near the hub where there is no root will be in front of the flow accelerator, so it won’t matter that there’s no root section there.

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