Experimental and theoretical investigation of pathways to deposit formation in thermally stressed aviation fuel in the presence of nitrogenous additives

In new and future aircraft, an increase in the operating temperature of the engine allows for more powerful and efficient engines. As fuel is employed as the primary coolant for aircraft systems and engines, thermal stability of aviation fuel is of major concern, both in the context of conventional as well as synthetic fuels. In this paper, we present a systematic experimental investigation of the influence of nitrogen species on thermal stability. Experimental evidence obtained from a HiReTS thermal stability test rig indicates that aromatic nitrogen compounds, such as m-toluidine, have a detrimental impact on the stability of aviation fuel and lead to a significant increase in the rate of formation of deposits. A chemical kinetics model based on an autoxidation mechanism derived from an automatic mechanism generator, Reaction Mechanism Generator (RMG), has been extended to investigate possible mechanistic routes to deposit formation arising from the studied additives. Further the thermodynamic and kinetic parameters for the postulated interactions have been obtained from quantum mechanical calculations performed with Gaussian 09. We use these parameters to assess within the model, the feasibility of the postulated pathways to deposit formation.