Abstract

While vertical takeoff and landing aircraft show promise for urban air transport, distributed electric propulsion on existing aircraft may offer an immediately implementable alternative. Dis- tributed electric propulsion has the potential of increasing the aircraft thrust-to-weight ratio and lift coefficient high enough to enable takeoff distances of less than 100 meters. While fuel based propulsion technologies generally increase in specific power with increasing size, electric propul- sion typically can be decreased in size without a decrease in specific power. The smaller but highly power-dense propulsion units enable alternative designs including many small units, optionally powered units, and vectored thrust from the propulsion units, which can all contribute to better runway performance, decreased noise, adequate cruise speed, and adequate range. This concep- tual study explores a retrofit of continuously powered, invariant along the wingspan, open bladed electric propulsion units. To model and explore the design space we used a set of validated models including a blade element momentum method, a vortex lattice method, linear beam finite element analysis, classical laminate theory, composite failure, empirically-based blade noise modeling, mo- tor mass and motor controller empirical mass models, and nonlinear gradient-based optimization. We found that while satisfying aerodynamic, aerostructural, noise, and system constraints, a fully blown wing with 16 propellers could reduce the takeoff distance by over 50% when compared to the optimal 2 propeller case. This resulted in a conceptual minimum takeoff distance of 20.5 meters to clear a 50 ft (15.24 m) obstacle. We also found that when decreasing the allowable noise to 60 dBa, the fully blown 8 propeller case performed the best with a 43% reduction in takeoff distance compared to the optimal 2 propeller case. This resulted in a noise-restricted conceptual minimum takeoff distance of 95 meters.Takeoff distances of this length could open up thousands of potential urban runway locations to make a retrofit distributed electric aircraft an immediately implementable solution to the urban air transport challenge.

Degree

MS

College and Department

Mechanical Engineering

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2018-11-23

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd10418

First Advisor

Andrew Ning

Second Advisor

Scott L. Thomson

Third Advisor

Steven E. Gorrell

Keywords

Distributed Electric Propulsion, Aircraft Design Optimization, Propeller Aerostructural Design

Language

English

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