Buch, Englisch, Band 2023-04, 214 Seiten, Format (B × H): 150 mm x 210 mm, Gewicht: 400 g
Reihe: NFL-Forschungsberichte
Buch, Englisch, Band 2023-04, 214 Seiten, Format (B × H): 150 mm x 210 mm, Gewicht: 400 g
Reihe: NFL-Forschungsberichte
ISBN: 978-3-947623-62-4
Verlag: Technische Uni Braunschweig NFL
In the context of increasing air traffic volume and associated fuel consumption and emissions, ultra-high aspect ratio wing (UHARW) concepts have the potential to significantly improve aircraft fuel efficiency and contribute to the achievement of sustainable aviation goals. To solve the structural problems associated with the slender wings of the UHARW concept, unconventional aircraft configurations and advanced design and optimization methodologies are required to realize promising UHARW aircraft designs. Within this thesis, two promising unconventional aircraft configurations that benefit the UHARW designs are identified, i.e., strut-braced wing (SBW) and twin-fuselage (TF). The objective of this study is therefore to develop the conceptual design and analysis procedures and multidisciplinary design optimization (MDO) frameworks for these two unconventional configurations, taking into account the impact of novel airframe technologies being studied for the next generation of transport aircraft. As weight estimation is the first and most important step in aircraft initial sizing, semi-empirical and semi-analytical weight estimation methods are presented and developed for the SBW and TF aircraft configurations. Existing semi-empirical and physics-based methods are used for propulsion system analysis, point performance estimation, etc. Especially, the aerodynamic analysis methods for SBW aircraft, and fuselage, tailplane, and landing gear sizing methods for TF aircraft are described. A multi-fidelity aircraft design and assessment environment, featuring convergent iterations for the evaluation of aircraft weight breakdown and mission profile is used and extended for the SBW and TF aircraft configurations, as well as the impact of novel airframe technologies. A multi-fidelity MDO procedure consisting of a conceptual-level MDO and an aerostructural optimization is developed. The conceptual-level MDO is used to optimize the aircraft mission and geometric parameters at the conceptual design phase with respect to the mission profile of the aircraft based on a gradient-based optimization algorithm. The initially optimized configuration is used for higher fidelity aerostructural optimization. A coupled adjoint aerostructural optimization tool is improved with geometrically nonlinear structural analysis models and extended for SBW and TF aircraft configurations. In particular, the aerostructural optimization method uses a quasi-three-dimensional aerodynamic solver with the ability to analyze and optimize natural laminar flow wings. The methodology is utilized to perform comparative studies of the SBW and TF aircraft configurations with UHARW designs. For this purpose, an SBW and a TF configuration are designed for short-range (SR), medium-range (MR), and long-range (LR) missions, respectively. Subsequently, the MR-SBW and MR-TF aircraft are used for MDO research. The conceptual-level MDO is first conducted for the two aircraft before the aerostructural optimization. In aerostructrual optimization, a free boundary layer transition optimization and a fully turbulent boundary layer optimization are performed respectively for the two aircraft for comparison purposes. Boundary layer ingesting (BLI) distributed propulsion, a promising novel propulsion concept for improving aircraft fuel efficiency, is researched in this thesis. Disciplinary analysis modules and MDO framework for BLI distributed propulsion aircraft, especially with the TF configuration, are developed. Two study cases, a wing segment with distributed propulsors and a TF distributed propulsion aircraft, are used to demonstrate the developed methods and investigate the characteristics of the BLI distributed propulsion aircraft.
