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.