Large eddy simulations of sustainable aviation fuel combustion: influence of chemical reaction mechanisms and fuel properties in a model aero-engine injector

Sustainable aviation fuels (SAF) offer a promising solution to reduce the environmental impact of aviation; yet, their behaviour in aero-engine combustors remains difficult to predict due to the effects of their composition on spray dynamics and chemical kinetics. In this work, large eddy simulations (LES) are performed for a single-cup, swirl-stabilised atmospheric model combustor equipped with a triple annular research swirler (TARS) to investigate fuel sensitivity and the influence of chemical reaction mechanisms. Three fuels are considered, including conventional Jet A and two Category C fuels with contrasting physical and chemical properties. Each fuel is simulated using two distinct families of reaction mechanisms, Z79 and HyChem, to explicitly assess chemistry model dependence. The results show that fuel-dependent trends in flame structure, heat release distribution, wall interaction and emissions are consistently observed, but the absolute values are strongly conditioned by the choice of reaction mechanism, with chemistry-induced differences often exceeding fuel-to-fuel variations. Despite this limitation, some relative fuel trends are robust across mechanisms. The findings indicate that LES is a useful comparative tool for fuel sensitivity assessment and emphasise the importance of cross-validating trends across multiple chemical mechanisms to extract physically meaningful and design-relevant insights from inherently complex simulations.