Synthetic Blend Component Study: The Effects of Hydrocarbon Composition on Aviation Fuel Dielectric Constant

The dielectric constant is used in aircraft for onboard fuel density and volume gauging, which is essential for safety and efficiency. The goal of this paper is to report the effects of synthetic blend components (SBCs)─which have compositions that deviate from conventional Jet A fuels─on density gauging. Dielectric constant and density measurements were taken using the newly developed Stanhope-Seta JetDC, which was designed to align with aircraft gauging equipment. Measurements were taken for blends of SBCs with both Jet A and synthetic aromatic kerosene (SAK), with a total of 269 observations generated from 0 to 40 °C. The gauging slope, which is the industry standard for correlating dielectric constant with density, was calculated using the measured values and compared to a distribution of 169 conventional fuels from the literature. It was found that the gauging slope varies significantly for SBCs, with values as low as 0.2946 for neat cycloparaffinic kerosene and as high as 0.4546 for neat SAK, relative to the average conventional fuel value of 0.3557. The dielectric constant data was coupled with two-dimensional gas chromatography to explore the effect of fuel composition on gauging. Partial least-squares regression indicates that alkylbenzenes and cycloaromatics have a positive correlation with the gauging slope, while iso-alkanes, n-alkanes, and cycloalkanes have a negative correlation. Despite the influence of fuel composition on the gauging slope, it was found that the resulting density errors were below the 1.2% threshold for effective fuel gauging at the temperatures tested.