CoolIP index                                                          Most recent edit: Wednesday October 24, 2012

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Optimal Camber for Dual-Mode (Motor/Generator) Rotors

This is an old topic on this Forum, but its a good time to update it-

Its known that optimal rotor airfoil camber reverses between AWES motor/generator modes, and that two sets of solutions exist, but at added cost and complexity-

One general method is a reversible camber blade that warps chord-wise or uses slats and flaps. This could be a mix of active servo mechanism and passive compliance. High passive compliance is revolutionary for engineered turbines, but could be quite simple and cheap* (tuna fin model).

The other known solution is a finely profiled fixed-camber variable pitch blade that "tacks" its incidence between modes. A reversed helical-pitch elastic warping* is required, with a full rotor rotation reversal. Conventional transmissions can drive this sort of action by differential gearing and clutching, but this is high-cost high-complexity mechanism, of marginal "bleeding edge" value. It may pay in "perfected" versions, especially with the added power management advantages of multi-gearing. A key is maintaining the motor/generator in smooth unidirectional operation by precise clutching and gearing, to buffer rotor churn between modes.

* Aero-turbine blades are evolving to have a tough compliant (fiber-reinforced) rubbery consistency, much like tire construction.

CoolIP*                      ~Dave Santos                 7Jan2012                     AWES5322

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