Water droplet size variation has been established in the literature as an important variable that influences the behavior and characteristics of water in fuel emulsion. However, with the growing demand for sustainable aviation fuels (SAF), no data is available that shows how these fuels will affect the size of dispersed water droplets and their frequency distribution. To address this lack of knowledge, this study explores and presents experimental results on the characterization of dispersed water droplets in alternative fuels and Jet A-1 fuel under dynamic conditions. The alternative fuels comprised of two fully synthetic fuels, two fuels synthesized from bio-derived materials, and one bio-derived fuel. The data and statistics presented reveal that water droplet frequency and size distribution are sensitive to changes in fuel composition. Observations showed an evident transition of the droplet percentile over time in the cumulative frequency distribution; this could be attributed to droplet coalescence to form larger droplets. Mean droplet diameters between 3 and 6 mu m were observed for all the fuels tested. With further analysis based on recommendations proposed in this work, the data may assist in providing insight to filter manufacturers.

The contamination and behaviour of water in aircraft fuel systems remains a significant global research interest following several aircraft incidents. To engineer a solution to the problem of icing in jet fuel, it is crucial to precisely identify the conditions and features that may exacerbate this phenomenon. This review will aid prospective researchers to identify work that has been done and work that is yet to be available for future study. In this review, conclusive data integrating a wide range of literature and also providing an in-depth description of the factors that influence the behaviour of trace water, ice formation in jet fuels was carefully summarised. On investigational studies, it was discovered that to date, no work is available that studies the impact of sustainable jet fuel and its blends on ice formation, size and frequency distribution of dispersed water droplets in aircraft fuel systems. Findings from comparative studies also reveal that surfaces will have an essential role in the growth pattern of ice in aircraft fuel systems. Furthermore, findings show that supercooled water droplets with sizes greater than or equal to 5 mu m can induce ice accretion. This review identified a common problem with the prominent methods of reporting results as a graphically fitted plot. Subsequently, it proposed that authors of any original technical work provide raw data as supplementary information to allow comprehensibility. The study further offers a system that could help manage the nature of ice in aircraft fuel tank systems-making it readily available and accessible.

Water in aviation fuel is a destructive contaminant and can cause serious problems that compromise aircraft's safe operation and reduce its efficiency and lifetime. Online monitoring of water content in aviation fuel would permit the control of water content before it builds up to dangerous level. Optical fibers made of PMMA have water affinity. In a PMMA based optical fiber Bragg grating (POFBG) its refractive index and volume vary with the water content. This feature is used to detect tiny water content in aviation fuel in this work. The sensing mechanism of POFBG is analyzed. POFBG wavelength is found to be the function of both temperature and equilibrium relative humidity (ERH). POFBG response to water content in fuel can be determined by the ERH. The sensor is experimented at different environmental conditions to identify its sensitivity. As a result, a general expression of POFBG response is achieved. Water content in Jet-A1 is measured by using POFBG sensor calibrated with both environmental chamber and coulometric titration. POFBG sensor is finally tested in a simulation fuel tank, demonstrating a better performance than coulometric titration. A sensitivity of POFBG wavelength change to water content of 33 pm/ppm is achieved at room temperature, indicating detectable water content of 0.03 ppm.

Cyclodextrins are promising building blocks for the synthesis of industrial binders. A new binder was prepared by cross-linking β-cyclodextrin with variable amounts of polyethylene glycol diglycidyl ether (40–60% w/w) to produce a soft polyether network that was soluble in water and alcohol, and the thermomechanical properties of the binder were determined. Increasing the amount of cross-linker reduced the glass transition temperature of the binder, as determined by differential scanning calorimetry and dynamic mechanical analysis. Cooling experiments revealed sudden stress relief below the glass transition temperature, reflecting the de-bonding of the polymer from the metallic supports. This was prevented by contact with polytetrafluoroethylene tape. Optical microscopy confirmed the stress relief in the form of cracking, and revealed self-healing by reptation, promoted by a higher cross-linker content and temperature. The information gained on the influence of the support medium on the thermomechanical properties of the cross-linked β-cyclodextrins can be used by industry for optimising manufacture and storage methods for new binders.

Water solubility-temperature curves were created experimentally for five kerosine fuels and one wide-cut fuel. The Karl Fischer Coulometer method was used to determine the saturated water content of each fuel over a range of temperatures between −5°C and 25°C. The affinity for water of each fuel with respect to the other fuels was measured and ranked. The experimental solubility curves are comparable to the water solubility curves of the Jet A-1 and JP-4 fuels reported in the CRC Handbook of Aviation Fuel Properties. There are subtle differences between the experimental solubility curves and the CRC curves. This may be attributed to batch-to-batch variation or recent changes in fuel chemistry owing to the need to exploit less favourable crude oil reserves. A generic equation has been proposed to estimate the water solubility when aromatics content and flash point are known.

Experimental studies were performed to gain a better understanding of ice growth in aviation jet fuel at low temperatures. Dissolved water precipitated from fuel to form fine water droplets of diameters typically no more than 5μm as the fuel was cooled. Some water droplets could remain in a metastable supercooled state to temperatures below −30°C. At temperatures below that, supercooled water droplets appeared to freeze to form metastable ice particles. Examples of this type of ice have been reported and may be stacking disordered ice (I) composed of randomly stacked layers of cubic ice (Ic) and hexagonal ice (Ih) sequences. Ice particles, exhibiting Ih polymorph characteristics, were found to nucleate and grow on surfaces at sub-zero temperatures. These hexagonal ice particles were observed to grow at the expense of the metastable ice particles near them. The observed mass transfer of water from metastable ice particles to deposition on the hexagonal ice particles in aviation jet fuel was attributed to the augmented Wegener–Bergeron–Findeisen (WBF) process and the Ostwald ripening process. The two processes supported the growth of hexagonal ice particles until the metastable ice particles near them were completely exhausted.