MS student Jianqiao (Peter) Xiao with Advisor K. Haran

A direct-drive electric propulsor for an aircraft is a motor-propeller pair connected directly through a shaft without a gearbox. Because of its high efficiency and mechanical feasibility, the direct-drive design has great potential in an electric aircraft propulsion system. In such a design, the propeller prefers a smaller hub size, which gives a larger effective area that increases aerodynamic efficiency. However, the motor design prefers a larger hub size, since a larger radial dimension decreases the motor΄s electric frequency, which reduces electric loss. The hub-size effect on the efficiency of both the motor and the propeller has been studied using analytical equations. Initial results from the direct-drive electric propulsor co-design showed an optimal sizing point for efficiency in the motor-propeller subsystem for a given propeller geometry, as presented in Figure 6. This research is funded by NASA.

Efficiency in hub-size effect for electric propulsor

Figure 6. System-level efficiency vs hub size