Aerodynamic Optimization of an UHBR Engine Position on a Short Range Aircraft Configuration at Cruise Flight Conditions

Abstract

The trend towards more efficient engines with larger diameters is expected to continue for future commercial transport aircraft. One crucial aspect caused by the increasing engine size is the integration of the engine on the wing. This issue is being investigated in the European Project CleanSky2 within the platform Large Passenger Aircraft (LPA) by combining a conventional single-aisle aircraft with an ultra high-bypass ratio (UHBR) engine (Bypass ratio BPR=15). The work within this project focuses on the low-speed configuration during take-off and especially landing, because the large engine diameter and the close coupling of wing and engine leads to a shortened leading edge device in spanwise direction. This slat cut-back affects the high-lift performance adversely because of the locally missing leading edge device, which is crucial to reach the required lift coefficients. As a consequence, a mitigation needs to be devised to stabilizethe flow on the wing in the wake of the engine and recover the performance loss. A promising option is active flow control (AFC) to suppress a significant flow separation at relevant angles of attack. In order to study the low speed configuration, an optimization was set-up to generatea realistic UHBR single-aisle short-range configuration. Therefore, an optimization of the engine’s position along the wing was accomplished in cruise flight conditions. A subsequent optimization refined the obtained design through a shape adaptation of nacelle and pylon. This paper will cover the engine position optimization. For this purpose, a fully automated process chain including geometry adaptation, mesh generation, CFD calculation and evaluation was established. With the aid of a surrogate based optimizer, a design of experiments (DoE) was performed to investigate the influence of the horizontal distance, vertical distance, pitch and toe-in angle within a defined parameter space. An adaptive sampling approach following the DoE found the optimal engine position for minimum drag at cruise flight conditions.