Performance Comparison between Copper and Aluminium Windings in a Rim Driven Fan for a Small Unmanned Aircraft Application

Rim Driven Fans (RDFs) are receiving increased attention amongst zero-emission aerospace technologists as they offer the potential for high Fan Pressure Ratios (FPR) to be efficiently generated and fan flow to be maximised compared with conventional (hub driven) electrical axial-flow fans. In other words; RDFs can provide higher thrust performance and exhaust air velocities than hub driven devices of the same intake area and also offer significant aerodynamic drag reductions. As such they are a feasible propulsion contender for fixed-wing, distributed-thrust, electrical aircraft designs. Thrust-to-weight ratio is a critical design parameter when considering aircraft propulsion devices and so design mass must be optimised accordingly. This paper presents an electromagnetic comparison of copper versus aluminium, slot-less, brushless DC motor (BLDC), stator-wiring architectures. The results of this study identify the performance benefits and limitations of these differing stator wiring materials in the context of a single rotor-stage RDF intended for the propulsion of a small unmanned aircraft.