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International audience; The EU-funded project ALTERNATE aims to explore the possibility of broader use of sustainable aviation fuels (SAFs). Part of the project assesses the effect of SAFs on soot production using experimental results and model predictions. In this regard, the combustion of two fuels was investigated under high-pressure conditions on the MICADO test rig at ONERA. This combustor allows a detailed analysis of soot formation based on advanced laser diagnostics. During the experimental campaign, the effect of Jet A-1 and Alcohol to Jet (ATJ) on soot levels was studied for three operating conditions in which the pressure of the combustion chamber varied from 4.5 to 9 bar, while maintaining almost constant the fuel-to-air ratio. An investigation of spray formation, flame shape and combustion dynamics is carried out to shed light on the impact of fuel composition on soot formation. In addition, the sooting behavior of the two fuels is compared, and it is observed that ATJ has a lower sooting capacity than Jet A-1 for the studied conditions. In parallel, Safran Tech and CERFACS worked jointly to perform Large Eddy Simulation (LES) for the case 4.5 bar fueled with Jet A-1. Semi-detailed chemistry for fuel oxidation and gaseous soot precursors together with the Lagrangian Soot Tracking model, both developed by CERFACS, is applied, and a first comparison against the available experimental data in terms of spray evolution and flame shape is obtained. The present work gives an overview of the experimental data collected during ALTERNATE, of SAF effects on soot generation and a first comparison obtained with LES for the Jet A-1 case at 4.5 bar.

Experimental studies have suggested that soot particles formed along different streamlines in a diffusion flame may have different morphologies. However, the uncertainties linked to the sampling and their analysis make difficult the quantification of these morphological differences. In this work, this problem is explored from a numerical point of view thanks to a coupling of nanoscale and macroscale simulations. This shows remarkably larger and more compact aggregates near the wings of the flame compared to its centerline. The analysis of morphological parameters such as anisotropy, monomers overlapping and coordination number reveals the complex morphology of soot and shows the presense of chain-like aggregates along the different streamlines of the flame., Des études expérimentales ont suggéré que les particules de suie formées le long de différentes lignes de courant dans une flamme de diffusion peuvent avoir des morphologies différentes. Cependant, les incertitudes liées à l'échantillonnage et à leur analyse rendent difficile la quantification de ces différences. Dans ce travail, ce problème est exploré d'un point de vue numérique grâce à un couplage de simulations aux échelles macroscopique et nanoscopique. Ces simulations montrent des agrégats remarquablement plus grands et plus compacts dans les ailes de la flamme comparativement à ceux rencontrés le long de l’axe central. L'analyse des paramètres morphologiques tels que l'anisotropie, le recouvrement des monomères et le nombre de coordinance révèle la compléxité de la morphologie des particules de suie ainsi que la présence d'agrégats en chaîne le long des différentes lignes de courant de la flamme