Assessing the influence of aircraft/engine integration and design on contrails

Aviation's environmental impact extends beyond CO2 to also include non-CO2 effects, with contrails and contrail cirrus as the dominant contributors. Understanding factors influencing contrail properties and mitigation pathways is key to climate-neutral aviation.

This thesis develops a workflow to assess how aircraft/engine design affects contrail properties while considering aerodynamic performance, bridging the gap between low-order models and LES to capture near-field exhaust and aircraft interactions.

A parametric aircraft geometry is used within power-on CFD simulations with a coupled engine model to simulate cruise conditions. A contrail microphysics model is developed and implemented within a CFD solver to assess ice particle formation, dynamics and evolution. Engine particle emissions are predicted using a machine-learning model trained on ground data and scaled to cruise conditions. These results are then applied as a CFD boundary condition for contrail simulations.

The workflow first assesses the influence of engine integration on contrail properties. It is shown that there is significant interaction between the engine exhaust and wingtip vortex, which dictates ice crystal distribution within a contrail. Including aircraft performance within the workflow makes beneficial changes regarding emissions via engine positioning complex without further airframe optimisation.

High-level engine architectures are also investigated regarding aircraft emissions. Contrail formation is first assessed using the engine model only, where a dependence on the detailed engine exit conditions used is shown to alter formation prediction results. A preliminary investigation of the potential benefits of mixed exhausts is outlined for higher fidelity studies. CFD shows contrail properties are dictated by emission particle number, then engine efficiency. Hence, future engine design choices must consider all engine emissions in a multidisciplinary manner to assess their overall environmental impact.

This thesis demonstrates a workflow which integrates aerodynamic, propulsion, and contrail modelling, providing a basis for design-based contrail mitigation strategies to be explored within a multidisciplinary framework.