A methodology for the determination of optimal operational schedules of hybrid electric architectures

Abstract

Hybrid electric aircraft have been proposed as a means to achieve the ambitious fuel burn reduction goals set for future air transports. Many of these hybrid aircraft supplement the fuel they carry with batteries, resulting in propulsion systems which can meet a thrust requirement in multiple ways until the battery runs out of charge. The choice of when to supplement the gas turbine with electrical power can change the fuel burn even if the same total amount of battery is used due to the weight change from fuel burn being different than that for battery and the fuel efficiency change from adding electricity changing depending on the thrust being produced and the flight condition. Choosing the proper power schedule for the electric motors is essential to efficient flight and to accurate estimates of fuel burn during design. This research examined the state of the art for hybrid electric power scheduling in aircraft and in cars, where this technology has already reached the market. Several different hybrid electric power scheduling methods are identified from the literature. A methodology was then proposed for choosing appropriate schedulers for future hybrid electric aircraft designs. A hybrid electric aircraft simulation framework was developed to explore the problem and test the methodology on an example hybrid aircraft. An application of the methodology was then demonstrated by applying it to the battery sizing problem for a hybrid electric aircraft.