Fouling in jet fuels: a new approach

The operating temperature of aircraft fuels is expected to increase significantly in the future due to the high temperature environment of high performance engines, ram air heating, and higher heat loads from cooling aircraft system components. As the fuel temperature increases, certain constituents in the fuel begin to break down to form gums and insoluble solids. These undissolved products clog filters and produce sticking in fuel control valves, and generally reduce the performance of fuel/oil heat exchangers and fuel nozzles. The accumulation of insoluble products on surface is referred to as fouling. CFDC modeling offers the potential of sorting out the complex coupling between the chemistry, fluid mechanics, and heat transfer processes that make fouling difficult to understand. The initial attempt to 'calibrate' a CFDC model was not fully successful but encouraging. At least two global Arrhenius rate expressions may need to be put into the model to cover a wide temperature range. Some capabilities of the model were illustrated for electrically heated tube experiments. However, the full potential of the model cannot be realized until additional chemistry and physics are implemented and data of local temperatures, velocities, particle size distributions and species concentrations are obtained from 'clean' experiments.