Overview
The AvAUNT proposal seeks to advance the state-of-the-art in understanding of the aerodynamic interference challenges associated with the Ultra High Bypass Ratio (UHBR) nacelle with an integrated Adaptable Area Nozzle (AAN) to Technology Readiness Level 4. The move towards higher bypass ratios can lead to significant reductions in emissions and noise; up to 10% propulsive efficiency enhancement and 2dB noise reductions from UHBR ~15 and above reported. However, by lowering fan pressure ratios, fan surge problems can emerge with increasingly larger variations in flight performance between sea-level and cruise. To overcome this, the adaptive area nozzle can provide the necessary increases in surge margin at low mass flow conditions at sea-level, but at the expense of additional system weight and complexity.
While many of the potential benefits of the UHBR configuration have been substantiated for isolated nacelle configurations, there is limited understanding of the installation interference effects that will be induced at these very high/ultra-high ratios, or how the incorporation of the AAN may affect the nature of these interference losses. In the current project, early stage candidate concepts for a nacelle with AAN technology will be studied through complementary experimental and computational simulation to ascertain the interference effects induced and to propose a verified modelling methodology which can be used in advance design studies. This will be used to inform best practice in the design of installed UHBR nacelles with AAN technology to support a move towards an integrated technology demonstrator within the Clean Sky 2 Joint Undertaking for late 2023.