Design study of a Martian rotor blade using a triangular airfoil

Abstract

The Martian atmosphere is characterized by a low density and low speed of sound, which result in the low Reynolds number compressible flows. In this regime, conventional airfoils perform poorly due to the boundary layer separation and the formation of shack wave. The current paper investigates the hovering performance and the structure analysis of a Martian rotor blade built with a triangular airfoil using numerical analysis. The airfoil, with a thickness-chord ratio of t / c = 5% at 30% chord, has been shown through experiments to exhibit non-linear lift enhancement due to the roll-up vortex caused by the sharp leading edge at high angles of attack. The designed blade has a pitch axis of 40% chord, close to the airfoil center of gravity. In order to evaluate the blade thickness distribution along the radial station, Carbon Fiber, due to its high strength-to-weight ratio is applied to the blade. It is found that the main source of stress is inertia force rather than aerodynamic loads and that the blade is structurally safe. Finally, the blade reaches a Figure of Merit of FM = 0.73 at the collective pitch angle of 8 deg and the minimum tensile and compressive factor of safety of 2.90 and 1.74 respectively.

Keywords

• numerical analysis
• triangular airfoil
• rotor blade design
• Martian atmospheric conditions
• Figure of Merit
• structural analysis