The demand for air travel is increasing as the world becomes more interconnected and interdependent and as a consequence, the aviation industry continues to produce greenhouse gas emissions and pollutants like soot, which contribute to climate change. Among the non-CO2 effects caused by aviation, the production of soot, a by-product of burning carbon-based fuels, is considered the second largest contributor to global warming and contrail formation, after CO2.
In this context, the project ESTiMatE was proposed in view of future emission regulations for smoke and particulate limitations in lean burn aero-engine architectures and addresses the fundamental issue of soot formation for kerosene-type fuels under lean burn conditions.
ESTiMatE is dedicated to the development of advanced soot models and its application in combustion simulations for the prediction of soot formation from oxidation to particle formation at conditions of relevance for aeroengines. Having advanced and reliable models for high-fidelity simulations is fundamental, since Computational Fluid Dynamics (CFD) is a key element for the design of next generation low-emissions engines, leading to important savings in time and cost.
To achieve the ambition introduced above, ESTiMatE was built to fulfil the following specific objectives:
- Identification of the main precursors and polycyclic aromatic hydrocarbons (PAHs) for soot formation from the analysis of chemical kinetics of kerosene-like surrogates.
- Identification of chemical paths for soot formation from precursors and PAHs.
- Generation of detailed and reduced chemical kinetics for fuel oxidation that also account for soot chemistry.
- Development of particle size distribution models to represent the dynamics of soot.
- Integration of the developed chemical kinetics and soot models into different turbulent combustion models.
- Development of a primary breakup model for air blast injectors based on high-fidelity numerical simulations.
- Development of reference experiments for combustion from laminar to turbulent conditions to generate specific data for model development and validation.
- Assessment of models for the prediction of soot under conditions relevant to aero engine combustors.
During the project, these objectives have been successfully achieved providing valuable results for the modelling of soot formation from nucleation to particle formation, oxidation and dynamics. In particular, a new chemical mechanism that accurately reproduces the chemistry involved in the soot formation was generated and applied along with advanced turbulent combustion models to the complex simulation of turbulent flames with a high degree of agreement in comparison to experiments. In addition, a primary breakup model for air blast injectors was developed, tested and validated using Lagrangian sprays.
As a consequence, the highly advanced models envisaged in this project have enabled a detailed description of the combustion and emission-formation phenomena in the complex environment of the combustion chamber of aeroengines. On the other hand, such models are being used to design engines with lower pollutant emissions, with the subsequent benefits for both the environment and the society.
