Experimental Investigation of Flame Dynamics and Thermoacoustic Behavior of Real Sustainable Aviation Fuels

Abstract

Sustainable Aviation Fuels (SAFs) offer a practical route to decarbonize aviation, as they can replace or be blended with conventional kerosene without major engine modifications. However, their impact on operability and thermoacoustic instability in annular combustors is not well documented. The combustion dynamics that drives these instabilities is notably influenced by fuel composition, chemical conversion rate and unsteady release of heat. This dependence has been recently explored using SAF surrogates but experimental data on real SAFs are still limited.

This study concerns the flame dynamics and thermoacoustic behavior of three non-aromatic SAFs, Alcohol-to-Jet, Catalytic Hydrothermolysis Jet, and Hydroprocessed Esters and Fatty Acids, compared to a dodecane fuel, which serves as a reference. Experiments are carried out in a single-injector combustor using a spray-swirl injector with a swirl number S_N = 0.74, under equivalent operational conditions.

Velocity and particle size profiles are found to be quite similar but there are notable differences in flame structures. Results highlight important differences in velocity-based Flame Describing Functions (FDFs) and in phase average flame images during a cycle of modulation indicating that chemical composition and physical properties can influence thermoacoustic behavior and combustor stability.