Off-Design Installed Nacelles

Ultra-high bypass ratio engines offer propulsive efficiency improvements and potential fuel burn reduction. The associated larger diameter can lead to an increase in nacelle drag that can erode the expected cycle benefits. Also, larger engines are likely to be closely coupled with the aircraft. Consequently, compact nacelles are needed to counter these aspects and to translate cycle fuel burn benefits into combined engine-airframe performance. An objective of ODIN is to develop design capability and detailed aerodynamic knowledge for installed compact nacelles to operate at off-design conditions such as take-off high lift, windmill and idle. Within a wider context of future power-plant integration, ODIN’s objectives include the improved understanding of exhaust suppression and jet-flap interaction noise. The viable design space for compact nacelles will be determined, across cruise and off-design conditions, with a multi-objective, multi-point optimisation method. High fidelity computations, and state-of-the-art high-resolution measurements with a novel section test rig, will reveal detailed aerodynamics of the design-limiting flow separation mechanisms. A synthesis of the multi-fidelity computational and experimental data will provide a calibration of the medium fidelity methods required for industrial design. An advanced dual-stream exhaust rig test will quantify installed exhaust suppression and jet-flap interaction noise and provide unique data to calibrate the computational methods at design and off-design conditions. Design constraints imposed by noise levels will be identified through experiments and high fidelity acoustic computations, which will also propose acoustic sensor layouts for the UHBR flight test demonstrator. Overall, ODIN will deliver validated design guidelines for novel nacelles to ensure cruise and off-design performance as well as the validation of computational methods for jet noise and exhaust suppression modelling.