We propose the development of a very high specific power integrated electric turbofan directly driven with a high frequency, air-core synchronous motor. If the target specific power is achieved, this technology could increase the viability of turbo-electric airplanes for commercial air transport, leading to significantly lower carbon emissions and energy use in aviation. The key innovation is the use of high fundamental operating frequencies, and a mostly air-core electromagnetic architecture, to obtain high specific power in electrical machines and drives. The aerospace industry employs 400 Hz ‘ac’ to keep component weights low. Hinetics is planning to introduce products that push these frequencies up by an order of magnitude to 3-10 kHz fundamental. The machine is transformed from the traditional metal-intense design to a composite and silicon-intense design. The new architecture is projected to improve machine power density by a factor of two over current best-in-class machines, with simple self-pumped air cooling, while achieving 98% efficiency. Additionally, the radially thin geometry, with simple self-pumped air cooling, lends itself nicely to integration within a ducted turbofan. A proof of concept high frequency MW scale motor has been developed by the University of Illinois under a NASA funded project. The design leverages recent advances in Wide Band-Gap (WBG) power electronic devices to obtain the high fundamental frequency while keeping current and voltage harmonics low. Hinetics LLC will build on this technology to develop an integrated electric tail-cone propulsor for commercial transport aircraft. The key question the team would like to answer within this SBIR Phase I project is whether the high frequency motor can be tightly integrated with a propulsion fan at the scale of NASA's STARC-ABL airplane concept and retain the promised power-to-weight advantages.
The initial target of the proposed technology is in the Tail Cone Thruster of NASA's STARC-ABL airplane concept. More broadly, the high frequency motor being developed could be an attractive choice for use in series hybrid electric propulsors and for integration into parallel hybrid jet engines, and become a viable option for all electric/hyrbid-electric propulsion applications at NASA and the aerospace industry in general.
The tightly integrated electric propulsor concept described in this proposal offers weight and efficiency advantages over a range of power and speeds, the technology could be applied to a number of emerging air vehicle concepts ranging from commercial transport airplanes to on-demand mobility vehicles.