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Experimental studies were performed to gain a better understanding of the behaviour of water in jet fuel at low temperatures. The transition of water in fuel from dissolved water to free water, and its subsequent precipitation behaviour when the fuel was cooled down, were investigated using a 20 litre glass-windowed aluminium tank. The effects of cooled internal surfaces were explored with chilled plates at the top and bottom of the aluminium tank. The tank was fitted with an array of thermocouples, which allowed horizontal and vertical temperature profiles to be measured. A laser visualisation system incorporating image processing software was used to capture images inside the simulated tank without interfering with the convective flow of the fuel. Fuel will precipitate any excess dissolved water when cooled below the saturation temperature. The excess water may then appear in the form of fine water droplets or ice particles as a fine cloud (fog).

Air traffic has been steadily increasing for the last years. Moreover, fuel availability at a reasonable cost seems more and more uncertain. Climate change implies that greenhouse gases emissions should be reduced. In this context, the search for new alternative fuels for aircraft seems to be a promising solution. Nevertheless, aeronautic represents a very specific transportation mode, due to its usage (short range, middle range, long range with the same fuel, worldwide distribution of the fuel…) and its compulsory security constraints. In the first part of the European project ALFA-BIRD (Alternative Fuels and Biofuels for Aircraft development - FP7), a selection of the best candidates to become the fuels for the future of aircraft has been done. The selection process was very complex, due to multiple criteria (physical properties, economical issued, environmental issues…).

Water is always present in jet fuel, usually in a mixture of forms. At very low temperatures this phenomenon can lead to the formation of ice crystals within the aircraft fuel system, which can then stay in suspension within the entire volume of fuel. Pumps within the fuel system transfer fuel around the system. Pumps such as boost pumps that are typically used in fuel systems are protected by a weave type filter mesh at the inlet. Ice accretion on the surface of this mesh has operational implications as it can cause non optimal fuel flow. In this investigation, two fundamental tools are being used: 1) a high fidelity MATLAB model of a mesh strainer, pick-up line and pump, and 2) a test rig of the modelled system. The model is being used to investigate fuel system performance when exposed to fuel containing water/ice contaminants at cold temperatures.