Search Results

This paper focuses on the investigation of the nature, process and effects of ice accretion on different feed pump strainers upstream of the aircraft feeding system. A suitable test rig was designed to circulate Jet A-1 containing water/ice contaminants at cold temperatures through the strainers. Following an extensive literature review, a number of screening tests were performed. These provided a strong base for an exhaustive study of fuel icing in the dynamic environment offered by the test rig. The effects of the rate of fuel cooling on the nature of ice were examined. As expected, it was observed that the yield of ice generated on the mesh screen increased with the water concentration in the fuel. It was also revealed that at higher cooling rates, a crust of snow formed on top of softer ice on the mesh screen.

The paper presents an extensive assessment of the hygroscopic characteristics of a number of alternative jet fuel blends. These are blended with conventional Jet A-1 to conform with current aviation standards at a 50:50 ratio by volume, except for DSHC (Direct Sugar to Hydrocarbon), which is blended at 10% DSHC and 90% Jet A-1. Given the lack of information available on the water solubility of alternative jet fuels, an effective analysis of experimental data about this characteristic in six different alternatives was performed. These included four ASTM approved alternatives (two Fischer-Tropsch (FT) synthetics from coal and natural gas, one HEFA (Hydroprocessed Esters and Fatty Acids) derived from camelina and DSHC. An extra two alternatives currently under consideration for ASTM approval were also tested; ReadiJet and an ATJ (Alcohol to Jet).

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).