SHAPE ADAPTIVE TECHNOLOGY FOR AIRCRAFT ENGINE NACELLE INLETS

摘要

The ambitious emission reduction goals defined by the Advisory Council for Aviation and Innovation in Europe (ACARE), demand new technologies enabling ways to significantly improve aircraft performance. In the European Commission funded low Technology Readiness Level (TRL) project "Morphing Enabling Technologies for Propulsion System Nacelles" (MorphElle) conducted between October 2013 and November 2015, an initial investigation took place to modify the inlet of an Ultra-High Bypass Ratio turbofan nacelle with adaptive structure technology to enhance its aerodynamic performance. The goal was to be able to adopt the inlet lip to different flight conditions and therefore, increase engine performance while at the same time reducing the aerodynamic nacelle drag. A pool of concepts for an adaptive nacelle inlet was established and a down selection was performed and the most promising identified. The selected concept was further elaborated and the impact at aircraft level was examined. Designing an adaptive structure mechanism for the circular shape of a nacelle inlet has different requirements compared to an adaptive structure mechanism, for example, a flap or a slat. For a circular shape, the deformation of the adaptive mechanism in circumferential direction has to be considered as well. A structural concept was established, which consists of flexible outer skin with pneumatic tubes as actuators, which is able to handle the deformation in circumferential direction. With this mechanism it is possible to change the inlet of the used reference nacelle geometry. Numerical tools were used to perform structural and aerodynamic simulations. The results of these simulations served as input for an aircraft assessment. The inputs were nacelle weight, nacelle aerodynamic drag and thrust specific fuel consumption of the engine. With this data an aircraft model was set up and compared to two reference aircraft. The first reference aircraft is a year 2000 reference (comparable to Airbus A330-300). The second reference aircraft is similar to an Airbus A330-300 with projected Entry-Into-Service (EIS) 2025+. For the aircraft equipped with the adaptive nacelle an EIS of 2025+ was assumed as well. The results were that the adaptive nacelle showed improved values for SFC and nacelle aerodynamic drag compared to the reference nacelle geometry. Furthermore, a first prototype of the shape adaptive mechanism as proof of concept was developed.