Multidisciplinary Design of Transonic Fans for Civil Aeroengines

Licentiate thesis, 2023

For current state-of-the-art turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. A complex set of system requirements and objectives, combined with component technology of high maturity level, demands performance predictions with higher accuracy that are sensitive to more detailed design features at an early conceptual design phase. Failing to meet these demands may result in a sub-optimal choice of aircraft-engine system architecture.

The emphasise of this thesis work is on fan-stage design and performance prediction in terms of aerodynamic efficiency and stability. The aspect of accuracy when it comes to establishing engine cycle performance for existing state-of-the-art technology based on open literature data is undertaken in the first paper. In the second paper a strategy to expand the parameter interdependencies of a fan-stage performance model with a multidisciplinary perspective is explored. The resulting model is integrated into an engine systems model and coupled with a simplified weight model to investigate the trade-off between weight and specifc fuel consumption. Results implied that being able to predict the rotor solidity required to maintain a given average blade loading - in addition to stage efficiency - is of high importance.