Emissions modelling for the optimisation of greener aircraft operations

This work focuses on the development and implementation of an emissions prediction model which allows the reliable calculation of emissions trends from current and potential future aircraft gas turbine combustors. The ultimate goal of the model developed involves its use in efficient aircraft trajectory optimisation processes, which eventually allow identifying aircraft "greener trajectories", minimizing in that way both aircraft fuel consumption and the pollutants emitted. From the three broad strategies that can be adopted for combustor emissions prediction: empirical correlations, stirred reactor models, and comprehensive numerical simulations involving detailed Computational Fluid Dynamics calculations, the second one was chosen for the development of the model described in this work. Thus, critical zones within the combustor are represented by individual stirred reactors, incorporating the processes of mixing, combustion heat release, and pollutant formation. To take into account inhomogeneities in gas composition and temperature which influence directly the rates of pollutant formation, a stochastic representation of turbulent mixing in the combustor primary zone is utilized. Results obtained from the simulations of an actual combustor using the emissions prediction model developed in terms of NOx, CO, UHC, and soot/smoke emitted show reasonable agreement with experimental data, reproducing the trends observed in practice.