Technology Demonstration of a Megawatt-Class Integrated Motor Drive for Aircraft Propulsion

An integrated compressor-generator concept, in which the electromagnetic rotor elements of a generator share a common rotor structure with the blades of the Low Pressure Compressor (LPC), is proposed as an approach to integrating megawatt-scale generators with a gas turbine. The benefits of this concept include the elimination of windage loss on the generator’s outer rotor surface, which is now used as the LPC hub, a reduction in overall number of bearings required, and an improvement in system volumetric power density by housing the generator inside the LPC. The lower temperatures of the LPC module provide the most favorable generator operating environment, and close access to a source of bleed air for cooling purposes. An outer-rotor permanent magnet electric machine reduced-order model framework that captures critical structural, thermal, and electromagnetic constraints is developed to identify key enabling technologies for maximizing specific power. A tooth-and-slot stator with an outer rotor Halbach array rotor architecture is identified to maximize electric machine specific power with current technology across a range of power levels from 100 kW to 3.6 MW. A fully air-cooled 1 MW integrated motor drive is developed to demonstrate the viability of the identified architectures and technologies. The motor drive is estimated to have electric machine and power electronics specific powers of 17.1 kW/kg and 20.2 kW/kg respectively, exceeding NASA’s 2030 performance targets for electrified aircraft propulsion. One key differentiator of the motor drive design is the attention afforded to its manufacturability and assembly. This includes additional constraints placed on material selection and the development of design features that minimize the risk of damage to components during assembly. A novel channel-type heat exchanger is developed and experimentally demonstrated to meet the combined structural and thermal performance requirements of the motor drive. Optimum heat exchanger geometry depends strongly on channel surface roughness, as system cooling flow limits constrain its operation to the flow transition regime. Synchronous excitation of the spindle modes via the destabilizing electromagnetic rotor-stator forces is a key challenge for the overhung rotor architecture due to the absence of an effective source of damping. The spindle root must be sufficiently stiffened to ensure the natural frequencies of the spindle modes are above operating frequencies. Motor drive rotordynamic operability is enabled with solid dampers controlled by a novel in-situ damper tuning mechanism, which produces changes in damper stiffness and damping without requiring disassembly and reassembly of the bearing housing module. The demonstrator outcomes are scalable and applicable to a wide variety of applications in transportation, power generation, and industry.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2023

Author dc:creator

• Chen, Yuankang

Advisor dc:contributor.advisor

• Spakovszky, Zoltán S.

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright MIT

Licence dc:rights.uri

• http://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/154196

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/154196