Design and analysis of an optimal electric propulsion system propeller

Abstract

There has been an increased interest in the field of electric power aircraft propulsion systems in recent years mostly due to the technological improvements in power electronics, energy storage and permanent magnet electric motors. This is not unusual since these systems can provide a large increase in efficiency and reliability while decreasing the carbon footprint. In most small and medium size UAVs the fully electric propulsion system is implemented. To obtain a propulsion system with an overall high efficiency one must take into consideration the efficiencies of all individual components as well as their matching meaning that the individual characteristics of all components have to be considered when designing the propulsion system. In this paper a propeller design methodology for a fully electric propulsion system is presented. The electric components were represented via simplified mathematical models while the propeller design was performed by the blade momentum theory with vortex wake deflection including corrections for the tip losses. The airfoil aerodynamic characteristics for different Reynolds numbers were determined by XFOIL and corrected for Mach number and post stall effects due to rotation. An off-design point analysis of the designed propeller was then performed and discussed. It was shown that an efficient fully electric propulsion system for initial design purposes can be created with the methodology. Some recommendations regarding the limitations and the possible improvements are also given in the paper.