Numerical Studies on the Effect of Design Trim on Aerodynamic Performance of a Micro Propeller for MAV Application

Of late, the aerospace industry has taken increasing interest in Micro Air Vehicles (MAV) powered by electric motor driven micro propellers. The endurance of the MAV largely depends upon the propulsive efficiency of its propeller. This has created a need for improved design of propellers through an in-depth understanding of the relevant aerodynamics. Design of micro propellers operating at low Reynolds numbers with sufficiently high propulsive efficiency is a challenging task. This paper deals with the parametric studies on a micro propeller for MAV application through numerical simulations. A propeller of known geometry was selected from the published literature. Geometrical model of the baseline propeller was prepared using CATIA V5 software and CFD analysis was carried out using ANSYS FLUENT 12.0 software. The baseline geometry of the micro propeller was modified by varying the spanwise position of maximum blade chord, maximum chord length, and pitch to diameter ratio to generate new design variants. The performances of these design variants were analysed through CFD simulations and compared in terms of variation of efficiency, torque coefficient and thrust coefficient against advance ratio. No significant change was observed in performance by changing the location of maximum blade chord. However, the required thrust of 1 N was achieved by increasing the chord length by 1.2 times the base line design at an efficiency of 64.2%. The propeller efficiency was further increased to 70.8% at an increased pitch to diameter ratio of 1.2 and at an advance ratio of 1.033.