Blade Testing for Best Windmill Performance

Overview

Objectives/Goals The goal of my project was a to discover the best windmill blade angle which would create the fastest rotation speed. I also evaluated the width of the windmill blades and its effect on rotation speed. A windmill that spins the fastest will produce the most energy. I made the body of the windmill from a K-nex set and made the windmill blades from balsa wood, same in length (12") but at different widths. For a wind source, I used a floor fan placed 2 feet and 6 inches away from the actual windmill. The fan was operated at various speeds. I measured the blade angles using a protractor. I measured the blade speed using the cadence feature from a bicycle cyclometer and attached that to the body of the mill. The blade rotation measurements were in RPM (Rotations Per Minute). My hypothesis is that the thin, 75-degree angle blade design will spin the fastest. My hypothesis was based upon my assumption that the 75-degree angle would push the blade more into the direction of the rotation creating a faster spin. The thin blade will be lighter so it would be easier to turn. Methods/Materials K-nex set for the windmill structure Sets of four balsa wood strips 12# long at different widths for the windmill blades 1 floor fan Cyclometer - cadence function (used for bikes) Washers (to counterweigh the cadence meter weight) Results The 5-degree thin blade produced the fastest spin; however, under high wind conditions, the 5-degree wide blade toppled the entire windmill structure. Larger angles were able to withstand higher wind speeds without toppling over. Conclusions/Discussion I was way off! The 5-degree blade angle produced the fastest spin under low and moderate wind conditions. The 5-degree angle had the largest surface area to catch incoming wind and had the least wind resistance in the direction the blades were rotating. However, the 5-degree wide blade caught too much wind and caused the structure to fall. The thin blade spun slightly faster than the wider blade because it was lighter and had a smaller cross section for wind resistance. I recommend further study to testing see if a windmill could be invented which automatically adjust to the best blade angle for the wind speed at that time.

Competition history

• CSEF 2002 Aerodynamics/ Hydrodynamics · Entry J0117

Resources

• CSEF project summary ↗

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