Integrity Energies - Wind
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  Multiple element airfoils found in nature? The sandhill crane wings in this photo below are a good example. Copied temporary "fair use" from a Nature Conservancy calendar credited to George Sanker/ AKM Images, Inc. The location is the Myakka State Park, Florida, USA.





The success of the small turbine BiFoil double element blades in use with the tip profile in the photo shown below is well established. No one thought approaching the Betz Limit could be so easy.



But how about the NoDrag Flap double element mod for the blades of the utility grade turbines, of which plenty are available in California wind projects. Skewed photos of blade tip profiles are amazing and amusing. As mentioned on the home page, skewing is a means of showing approximately how the blades look in the Earth Frame of Reference. What happens is that the NoDrag Flap, without actually doing so, effectively makes the blade wider depending on the TSR. This "widening" is without the weight and penalties of making the blade itself wider for extra performance. Here is a photo of a blade tip for an intermediate scale turbine with the NoDrag Flap mod to its upwind trailing edge:



Now here is a photo of the profile of this same blade tip turned upside down so as to show the direction of the approaching wind to be arriving from beneath. The NoDrag Flap profile is now on the right side:



Now the blade tip is skewed 59 degrees, representing a TSR of 1.67, equal to a 60 mph wind acting on the 100 mph blade tip velocity:



Now the blade tip is skewed 66 degrees, representing a TSR of 2.22, equal to a 45 mph wind acting on the 100 mph blade tip velocity:



Now the blade tip is skewed 73 degrees, representing a TSR of 3.33, equal to a 30 mph wind acting on the 100 mph blade tip velocity:



Now the blade tip is skewed 76 degrees, representing a TSR of 4.0, equal to a 25 mph wind acting on the 100 mph blade tip velocity:



Now the blade tip is skewed 79 degrees, representing a TSR of 5, equal to a 20 mph wind acting on the 100 mph blade tip velocity:



Now the blade tip is skewed 82 degrees, representing a TSR of 6.67, equal to a 15 mph wind acting on the 100 mph blade tip velocity:



The NoDrag Flap, despite its small size and short distance from the blade surface, appears surely to have an appreciable effect on the airflow passing through the rotor, particularly in adding to its deflection between the blades. Greater deflection means greater power.

As demonstrated by the success of the similar BiFoil blades, it can be "magic" that works(!).
 
 

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