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Increasing power output by reducing the windmill blade-tip vortex.


As the blade of a horizontal axis windmill passes through the air, air pressure forms a vortex at the tip. The vortex takes energy away, making less available for the conversion into electric power. My study compares the performance of a symmetrical and a flat-bottomed airfoil to those with a winglet added to the blade tip. My hypothesis is that the airfoils with the winglet will produce greater electrical output than the airfoils without winglets. The windmill I used was inspired by a US DOE report in 2009. For each series of experiments, after the rotor reached a steady state of rotation, I recorded 20 observations. I averaged the results and calculated the standard deviation. I calculated the T statistic for each pair of experiments. For the 2 in symmetrical and flat blade experiments, no pair of data sets had a statistically significant difference in the observations with and without the winglet, to produce a confidence level of 95%. The five and ten degree static angle tests for the 5 inch flat blade did have winglet output average results greater than the results for blades without winglets; however the confidence level T statistic was not statistically significant. Therefore the analysis of the experimental data shows that my hypothesis could not be supported to a 95% level of confidence.

E.O. Frost. Chaminade College Preparatory, West Hills, CA

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Author:Frost, E.O.
Publication:Bulletin (Southern California Academy of Sciences)
Article Type:Author abstract
Geographic Code:1USA
Date:Aug 1, 2014
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