Post stall propeller behavior at low Reynolds numbers

Abstract

Limited data exists for propeller and wind turbine post stall aerodynamics. Post stall aerodynamics was observed in small propellers at low Reynolds numbers. First, performance data (thrust, power, and efficiency) of set variable pitch propellers was acquired in a wind tunnel. The propellers were 6 to 9.9 inches in diameter and were able to pitch to extreme angles. Second detailed geometric characteristics (pitch, chord, airfoil) of the propellers were measured. Finally PROPID was used to simulate the propellers and predict the performance. Comparing the experimental and calculated results identified regions where post stall aerodynamics affected propeller performance. This understanding will assist in predicting post stall aerodynamics on small scale propellers. In addition three small propellers with tiplets similar to winglets on wings were tested and compared to traditionally tipped propellers. This comparison showed better designed traditional propellers were more efficient, but that tiplets improved performance of the specific propellers.