Performance analysis and operating potential of a hybrid-electric regional aircraft with box-wing lifting architecture
Creators: name:  G. PALAIA 
name:   K. ABU SALEM 
name:   V. CIPOLLA 
name:   V. BINANTE 
name:   D. ZANETTI 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: AERONAUTICS
FUTURE DESIGN

description: Abstract: Aeronautical research is increasingly driven towards developing solutions to reduce the environmental impact of aviation, in agreement with the requirements and constraints imposed by authorities. The European Commission aims to achieve climate neutrality for aviation in the EU by 2050; furthermore, an intermediate requirement is set for 2030, whereby a 55% reduction in greenhouse gas emissions must be reached. Introducing hybrid-electric propulsion systems is currently considered as a possible solution to reduce direct greenhouse gas emissions of commercial aviation; for this applications, different kinds of accumulators, such as batteries or fuel cells, can be adopted. Technological limitations related to such storage systems, which exhibit very low gravimetric energy densities compared to kerosene, make the development of medium and long-range hybrid-electric aircraft very unlikely, even considering optimistic future outlook for the improvement of accumulators performance. The development of hybrid-electric aircraft in the short-range aircraft categories appears more feasible. For this reason, the present paper focuses on the regional aircraft class, which is the candidate for the earliest introduction of electrification of propulsion systems among commercial transport aircraft; an investigation of the synergies between new propulsive technologies and disruptive airframe architectures, which can increase the fuel efficiency in comparison to conventional tube-and-wing configurations, is provided. In particular, this research describes the design and the performance achieved from the integration of the hybrid-electric propulsion with the box-wing architecture. In the paper, the possible advantages of the synergic implementation of these two technological advances in the aircraft design are highlighted, combining the benefit of CO2 reduction of hybrid-electric propulsion systems with the higher aerodynamic performance of the box-wing architecture [1]. This latter, introduced in 1924 by L. Prandtl as the best wing system for the minimization of the induced drag for given lift and wingspan, allows to reduce the energy demand to accomplish a reference mission. As a consequence, while maintaining the same wingspan of traditional aircraft, this lifting system allows to transport larger weights without penalties in terms of aerodynamic performance [2]. This peculiarity of the box-wing provides the possibility of embarking large quantities of batteries, hence fully exploiting the potential of hybrid-electric systems to minimize fuel burnt and CO2 emissions. A detailed performance study of the regional box-wing hybrid-electric aircraft is subsequently presented. In particular, possible different utilization strategies for the aircraft are analysed and discussed, starting from the definition of its payload-range envelope. The double energy source allows the optimisation of distinct figures of merit through different split strategies for power supply throughout the mission. For example, power management strategies can be identified to minimise fuel consumption inside the whole payload-range envelope; alternatively, power management profiles can be optimized to extend the nominal range of the aircraft, thus expanding the boundary of the payload-range diagram at the expense of higher fuel consumption. The shape of the payload-range diagram may vary according to the different figures of merit selected, and therefore to the power split supply strategy adopted. In conclusion, an extensive discussion of the performance potential of the hybrid-electric box-wing aircraft is presented, highlighting the possible advantages achievable from the introduction of this configuration in the regional transport segment. Limits and capabilities of this innovative architecture are then compared with the ones of aircraft with a traditional tube-and-wing architecture; this comparison shows that the implementation of the box-wing architecture for regional aircraft can be an effective solution to promote the introduction of hybrid-electric propulsion in commercial transport aircraft. References: [1] Palaia, G.; Zanetti, D.; Abu Salem, K.; Cipolla, V.; Binante, V.; THEA-CODE: A design tool for the conceptual design of hybrid electric aircraft with conventional or unconventional airframe configurations, Mechanics and Industry, 22, 2021. [2] Abu Salem, K.; Cipolla, V.; Palaia, G.; Binante, V.; Zanetti, D.; A physics-based multidisciplinary approach for the preliminary design and performance analysis of a medium range aircraft with box-wing architecture, Aerospace, 292, 2021.