Evaluation of net propulsive force in subsonic aircraft engines through low-fidelity propulsion integration methods
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Date
2026-10-09
Authors
Χατζημιχάλης, Θεολόγος
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Abstract
The shift towards Ultra-High Bypass Ratio turbofans in modern aviation offers significant improvements in specific fuel consumption but introduces severe aerodynamic integration challenges. The increased physical dimensions of UHBR nacelles lead to enhanced aerodynamic coupling with the airframe, producing interference drag and flow suppression that can offset uninstalled performance gains. This thesis presents a robust, computationally efficient, semi-empirical framework to evaluate the aerodynamic drag and Net Propulsive Force of aero-engine nacelles, transitioning from an isolated baseline to a fully installed wing-mounted configuration.
First, the isolated nacelle aerodynamic drag is estimated using Engineering Sciences Data Unit methods and interpolated data to rapidly calculate skin friction, profile, pre-entry, spillage, and wave drag components. A comprehensive Thrust and Drag Book-keeping system is subsequently established to properly account for the installed engine. To capture complex localized fluid-dynamic phenomena, such as shockwave-boundary layer interactions and the adverse "gulley" effect, high-fidelity CFD-derived integration coefficients, specifically modified thrust Coefficients, are applied onto an ideal theoretical thrust model. Furthermore, an interference drag factor, mapped multidimensionally as a function of the engine's longitudinal and vertical installation coordinates, is applied to quantify the aerodynamic penalty of the airframe integration.
The proposed methodology is validated against established reference data using two distinct case studies: an Intercooled Core engine integrated on an A330-type configuration, and an Active Core engine on an A320-type platform. The results demonstrate the model's high fidelity in predicting NPF sensitivities to engine positioning, accurately capturing the aerodynamic benefits of forward horizontal placements and the performance deficits associated with close-coupled or vertically extended installations. Ultimately, this framework provides a reliable low-fidelity tool suitable for the preliminary aircraft design phase, enabling the iterative optimization of engine-airframe integration prior to the deployment of computationally expensive full-scale CFD simulations.
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Keywords
Aeroengine integration, Nacelle aerodynamics, Thrust and drag book-keeping, Net propulsive force, Interference drag