Analysis and Design of a Small-ScaleWingtip-Mounted Pusher Propeller

The wingtip-mounted pusher propeller, which experiences a performance benefit from the interaction with the wingtip flowfield, is an interesting concept for distributed propulsion. This paper examines a propeller design framework and provides verification with RANS CFD simulations by analysing the wing of a 9-passenger commuter airplane with a wingtip-mounted propeller in pusher configuration. In the taken approach, a wingtip flowfield is extracted from a CFD simulation, circumferentially averaged and provided to a lower order propeller analysis and optimisation routine. Possible propulsive efficiency gains for the propeller due to installation are significant, up to 16% increase at low thrust levels, decreasing to approximately 7.5% at the highest thrust level, for a range of thrust from 5% up to 100% of the wing drag. These gains are found to be independent of propeller radius for thrust levels larger than 30% of the wing drag. Effectively, the propeller geometry is optimized for the required thrust and to a lesser degree for the non-uniformity in the flowfield. Propeller blade optimization and installation result in higher profile efficiency in the blade root sections and a more inboard thrust distribution.