Fan and Motor Co-Optimization for a Distributed Electric Aircraft Propulsion System

Abstract

An integrated modeling approach is presented for the conceptual design of electric aircraft propulsors, with application to NASA’s hydrogen fuel-cell powered transport aircraft concept, being developed under the CHEETA (Center for High-Efficiency Electrical Technologies for Aircraft) program. The distributed boundary layer ingesting (BLI) fan module and the fan-hub embedded MgB2 based fully superconducting (SC) electric motors are modeled together using Signomial Programming (SP). An all-at-once SP optimization eliminates external design iterations between modules and provides sensitivities to design parameters as part of the optimization solution. In addition, the approach developed here is modular and component models can be easily added to study various aircraft architectures. A trade space exploration of CHEETA propulsors indicates a highly-distributed 32 wing and fuselage mounted propulsors configuration, powered by 0.5 MW and 1.6 MW motors, respectively, as the optimal, yielding 16% reduction in the aircraft electric energy consumption relative to a conventional twin electric under-wing propulsors design. However, the design selected is a 9 propulsors configuration with 2.4 MW motors (power range more suitable for fully SC architecture), with about 14% power savings. The fan-embedded motor architecture leads to fan hub-to-tip ratios of up to 0.5, which are higher than typical.