CFD Modeling of Sustainable Aviation Fuel Sensitivity on Aero-Engine Combustor

Sustainable aviation fuels (SAFs), which is produced from alternative sources, such as bio-derived feedstocks, provide essentially identical performance to that from petroleum-derived jet fuels. SAFs are identified as the best near- to mid-term solution for reducing carbon emissions, with carbon offsetting being the other major carbon mitigation strategy. The primary objective of the research in the paper is to determine if state-of-the-art computational fluid dynamics (CFD) models could predict the fuel effects in a realistic combustor as a pathway for original equipment manufactures (OEMs) to assess the risk of their combustor designs using SAFs. In order to develop a numerical simulation method of SAFs combustion, a simplified chemical reaction kinetic model has been developed to simulate the combustion of a SAF fuel, G + FT, selected for study. In this paper, Hybrid Chemistry (HyChem) method has been referred to reduce the kinetic models to small sets of species and reaction steps that enable CFD simulations. First, a surrogate fuel which contains 56% n-dodecane and 44% iso-octane in mole fraction has been proposed to mimic the G + FT fuel. Second, the HyChem method is applied to the surrogate fuel to establish the simplified mechanism which consists of 43 species and 293 steps, and the number of steps is only 10% of that in the detailed mechanism. Then, we have validated the accuracy of the simplified model with G + FT fuel’s combustion testing data. For example, the average relative error of the predicted laminar flame speed is only 8.8%. Besides, the simplified mechanism has been successfully applied to the CFD modeling. In order to study the fuel sensitivity and verify the CFD modeling with the simplified mechanism, we have conducted a series of combustor rig tests with a conventional petroleum-derived fuel (RP-3) and a blend fuel (90% RP-3: 10% G + FT). Relative difference in simulated values of combustion efficiency, NOx emission and pattern factor due to the change from RP-3 to lend fuel is less than 5%. And fuel sensitivity error between modeling results and testing data in combustor outlet temperature profile is less than 10%. Therefore, the simulation results show that the CFD modeling approach used in this paper can reveal fuel sensitivity and predict fuel effects on a realistic combustor, which can be applied to access the risk of using SAFs in aero-engines later.