Characterization of ice particles in jet fuel at low temperature: 3D X-ray tomography vs. 2D high-speed imaging

The formation of ice crystals in aviation fuels at low temperatures is a major problem to the aviation industry. In this work, a fuel-icing bench from the Institut de la Filtration et des Techniques Séparatives (IFTS) was used to develop two characterization methods for the ice particles in jet A-1 fuel: (i) a 3D ex-situ method using X-ray tomography at low temperature, giving full access to the geometric complexities of the ice particles at 5.5 μm resolution and (ii) a 2D in-situ method using high-speed imaging at 4 μm resolution, allowing real-time measurements of ice particles flowing at high velocity. A large set of process parameters was studied: the circulation time (τ), the water concentration (C) and the interfacial tension (γ) at fixed temperature (θ) ∼ -18±2 °C. Overall, both methods gave consistent results, with particle sizes not exceeding 1 mm and mean sizes between 100 to 300 μm. The shapes of the particles were mainly spherical in 3D (∼ 50%) and circular in 2D (≥ 60%). Same trends were observed with both methods in relation to the process parameters. The grinding effect induced by an increased τ seems to be the most influencing phenomenon in the process, leading to the decrease of the particle size. In contrast, the effect of C is not conclusive, given the detection limit of particles in 2D for high concentrations. This study highlights the specificities of both characterization methods and the influence of the process parameters on the properties of the ice particles in jet fuel.