A Hybrid Economy Bleed, Electric Drive Adaptive Power and Thermal Management System for More Electric Aircraft

Minimizing energy use on more electric aircraft (MEA) requires examining in detail the important decision of whether and when to use engine bleed air, ram air, electric, hydraulic, or other sources of power. Further, due to the large variance in mission segments, it is unlikely that a single energy source is the most efficient over an entire mission. Thus, hybrid combinations of sources must be considered.

An important system in an advanced MEA is the adaptive power and thermal management system (APTMS), which is designed to provide main engine start, auxiliary and emergency power, and vehicle thermal management including environmental cooling. Additionally, peak and regenerative power management capabilities can be achieved with appropriate control. The APTMS is intended to be adaptive, adjusting its operation in order to serve its function in the most efficient and least costly way to the aircraft as a whole.

This paper presents a hybrid APTMS, which balances the use of economy bleed air and electric drive in a single architecture that automatically adapts to changing aircraft conditions to optimally regulate its function. Bleed air is used when it is relatively "cheap" (i.e., requires the lowest fuel consumption compared to other available power sources), but is reduced and supplemented with electric power from the main engine generator when bleed air becomes more expensive and electric power becomes cheaper. Through proper control, this strategy can find the most efficient balance of bleed air and electric power, increasing aircraft range and capability. This architecture, abbreviated "e₂", is presented, describing its components, functionality, and features. Comparisons to more traditional systems highlight the potential for energy savings afforded by the e₂ system. The analysis shows that the e₂ architecture has the potential to significantly reduce energy use compared to previous systems, without upsizing the primary generating system (PGS). Additional anticipated benefits include the ability to provide both cooling and supplemental power growth without upsizing the turbomachinery.