Innovative power train configurations for aircraft auxiliary power units focused on reducing carbon footprint

Abstract

Auxiliary power units constitute a non-negligible source of pollution not only in flight conditions but also at airports and their surrounding areas. This work compiles a technical feasibility assessment focused on the analysis of innovative alternatives to the traditional aircraft gas turbine based auxiliary power unit arrangement. The proposed innovations involve both new power train configurations and the use of different fuels, with the purpose of reducing both the primary energy consumption and the environmental impact of these systems. The core innovation proposed here consists in the use of a supercharged rotary engine as an alternative configuration to traditional auxiliary power units in aircraft. The rotary engine can achieve higher thermal efficiencies than gas turbines, which corresponds to a lower specific fuel consumption and, thus, a lower carbon footprint. Additionally, the proposed alternatives will involve hybrid configurations, providing thermal energy generation with electrical storage devices. Finally, the assessed arrangements will be based on the “more electric aircraft” concept, which implies a simplification of the aircraft non-propulsive power system design and allows the addition of batteries to the generating unit. In order to perform this assessment, different thermal models and simulations have been developed, allowing the quantification of the improvements related to the alternative proposed configuration.