Vaporization of JP-8 Jet Fuel in a Simulated Aircraft Fuel Tank ...

It was shown that the fuel vapor composition as well as the vapor to liquid
volume ratio (V/L) had significant effects on the vapor pressure and the flashpoint [21].
The vapor pressure decreased with increasing sample flashpoint, due to the abundance of
lighter low molecular weight-high vapor pressure hydrocarbons in the low flash point
samples, while the fuel samples with higher flash points had higher concentrations of
heavy, high molecular weight-low vapor pressure hydrocarbons. For samples with the
same flash point, decreasing the V/L ratio decreased the vapor pressure, due to the
depletion of high vapor pressure hydrocarbons at the low V/L ratio. The significance of
these findings is that the variation of flash point among samples of Jet-A reflects the
relative concentration between high and low vapor pressure components which control
the low temperature vaporization processes typically seen in a fuel tank.
The fuel used in this experimentation was tested for flashpoint in order to
determine which of the characterized fuels [21] would be best suited for modeling the
experiments. The experimental fuel had a measured flashpoint of 117°F, therefore, the
two fuel compositions from ref. 21 chosen to “bracket” the fuel composition used in the
present experiments were the fuels with flashpoints of 115°F and 120°F. Figure 2.1
shows the distribution of n-alkane species by number of carbon atoms in the two fuel
compositions chosen from ref. 21. It is apparent that the 115 °F flashpoint fuel has a
higher concentration of low molecular weight-low boiling point species than the 120°F
flashpoint fuel, which has a broader range over the high molecular weight-high boiling
point species. This figure helps to visualize the fact that fuels with higher concentrations
of light components will have lower flashpoints and be more flammable than fuels with
higher concentrations of heavy components.
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