Performance Comparison of Two Airfoil Rotor Designs for an Agricultural Unmanned Helicopter

Abstract

Purpose: The most important element of an agricultural helicopter is the rotor blade realizing lift force. In order to improve the performance of the rotor blades, two types (KA152313 and KB203611) of airfoils were designed and compared. Methods: The nose shape of the KB203611 airfoil was 'drooped' and 'sharp' compared to the leading edge of the KA152313 airfoil. The performance of the experimental airfoils was simulated using CFD-ACE program, and lifts were measured in situ using the 'AgroHeli-4G', a prototype helicopter. Results: Simulated lifts of the blade with the KA152313 airfoil showed proper values for a wide range of angles of attack between <TEX>$14^{\circ}{\sim}18^{\circ}$</TEX>, while the simulated lift of the KB203611 blade exhibited maximum values near <TEX>$13^{\circ}{\sim}14^{\circ}$</TEX>. In the lift measurements, the range of operable angles of attack was a collective pitch angle at the grip (GP) of <TEX>$12^{\circ}{\sim}18^{\circ}$</TEX> for the KA152313 blade. On the other hand, the range of angles of attack for the KB203611 blade was a GP of <TEX>$12^{\circ}{\sim}14^{\circ}$</TEX>. Conclusions: The blade of KA152313 performed well over a wide range of AoAs and the blade of KB203611 performed better at low AoAs. In this study, a variative airfoil blade, gradually emerging from grip to tip using the two different airfoils, was suggested.