Ambitious targets to reduce emissions caused by aviation in the light of an expected ongoing rise of the air transport demand in the future drive the research of propulsion systems with lower CO 2 emissions. Regional hybrid electric aircraft (HEA) powered by conventional gas turbines and battery powered electric motors are investigated to test hybrid propulsion operation strategies. Especially the role of the battery within environmentally friendly concepts with significantly reduced carbon footprint is analyzed. Thus, a new simulation approach for HEA is introduced. The main findings underline the importance of choosing the right power-to-energy-ratio of a battery according to the flight mission. The gravimetric energy and power density of the electric storages determine the technologically feasibility of hybrid concepts. Cost competitive HEA configurations are found, but do not promise the targeted CO 2 emission savings, when the well-to-wheel system is regarded with its actual costs. Sensitivity studies are used to determine external levers that favor the profitability of HEA.

This paper presents a method for wing aerostruc-tural analysis and optimization, which needs much lower computational costs, while computes the wing drag and structural deformation with a level of accuracy comparable to the higher fidelity CFD and FEM tools. A quasi-three-dimensional aerodynamic solver is developed and connected to a finite beam element model for wing aerostruc-tural optimization. In a quasi-three-dimensional approach an inviscid incompressible vortex lattice method is coupled with a viscous compressible airfoil analysis code for drag prediction of a three dimensional wing. The accuracy of the proposed method for wing drag prediction is validated by comparing its results with the results of a higher fidelity CFD analysis. The wing structural deformation as well as the stress distribution in the wingbox structure is computed using a finite beam element model. The Newton method is used to solve the coupled system. The sensitivities of the outputs, for example the wing drag, with respect to the inputs, for example the wing geometry, is computed by a Ali Elham a.elham@tudelft.nl Michel J. L. van Tooren combined use of the coupled adjoint method, automatic differentiation and the chain rule of differentiation. A gradient based optimization is performed using the proposed tool for minimizing the fuel weight of an A320 class aircraft. The optimization resulted in more than 10 % reduction in the aircraft fuel weight by optimizing the wing planform and airfoils shape as well as the wing internal structure.

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Abstract:It is always a strong motivation for aeronautic researchers and engineers to reduce the aircraft emissions or even to achieve emission-free air transport. In this paper, the impacts of different game-changing technologies together on the reduction of aircraft fuel consumption and emissions are studied. In particular, a general tool has been developed for the technology assessment, integration and also for the overall aircraft multidisciplinary design optimization. The validity and robustness of the tool has been verified through comparative and sensitivity studies. The overall aircraft level technology assessment and optimization showed that promising fuel efficiency improvements are possible. Though, additional strategies are required to reach the aviation emission reduction goals for short and medium range configurations.

This paper presents the development and implementation of a tool for wing structural sizing and aeroelastic optimization in early design steps, where the amount of available data about the wing structure is not enough to allow high-fidelity finite element analysis and optimization. The proposed tool consists of two levels. The first level is a quasi-analytical method for wing structural weight estimation and initially sizing of the wing box structure. The second level is an aeroelastic tool that uses a vortex lattice method and a finite beam element to compute the stress distribution in the wing box structure. The Newton method is used to solve the coupled system. The coupled adjoint sensitivity analysis method is used to compute the sensitivity of any function of interest with respect to the design variables. The tool was used for a series of wing aeroelastic optimizations to minimize the wing weight with a series of constraints on the wing structural failure modes and aileron effectiveness. Another series of optimizations is also used to find the wing jig shape for a predefined cruise shape. The outputs of the optimizations showed that the wing box weight varies quadratically with the required value for the aileron effectiveness.

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The feasibility of regional electric aviation to reduce environmental impact highly depends on technological advancements of energy storage techniques, available battery energy density, and high-power electric motor technologies. However, novel airframe technologies also strongly affect the feasibility of a regional electric aircraft. In this paper, the influence of novel technologies on the feasibility of regional electric aviation was investigated. Three game-changing technologies were applied to a novel all-electric regional aircraft: active flow control, active load alleviation, and novel materials and structure concepts. Initial conceptual design and mission analysis of the aircraft was performed using the aircraft design framework SUAVE, and the sensitivity of the most important technologies on the aircraft characteristics and performance were studied. Obtained results were compared against a reference ATR-72 aircraft. Results showed that an all-electric aircraft with airframe technologies might be designed with the maximum take-off weight increase of 50% starting from the battery pack energy density of 700 Wh/kg. The overall emission level of an all-electric aircraft with novel technologies is reduced by 81% compared to the ATR-72. On the other hand, novel technologies do not contribute to the reduction in Direct Operating Costs (DOC) starting from 700 Wh/kg if compared to an all-electric aircraft without technologies. An increase in DOC ranges from 43% to 30% depending on the battery energy density which creates a significant market obstacle for such type of airplanes. In addition, the aircraft shows high levels of energy consumption which concerns its energy efficiency. Finally, the sensitivity of DOC to novel technologies and sensitivities of aircraft characteristics to each technology were assessed.