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

Volume Fraction, %
30
25
20
15
10
5
0
115 Deg. Flashpoint
120 Deg. Flashpoint
0 5 10 15 20 25
n-alkane Carbon Atom
Figure 2.1. Distribution of n-alkane components by carbon atoms in two fuels with flashpoints of
115°F and 120°F, from [21].
2.1.7 Flammability Limits
The flammability limits of of a fuel-air mixture are defined as “the leanest and
richest concentrations that will just self-support a flame [22].” These two points define a
flammability range at a specified pressure. As the temperature and pressure are both
decreased, these two points typically converge, and likewise as the temperature and
pressure are increased the two points diverge, making a flammability envelope, outside of
which no flammable mixtures exist, as shown qualitatively in figure 2.2. Addition of
inert diluents, such as CO2, CO2, N2, Ar, He, or halogen compounds, into the vapor space have
the effect of converging the flammability limits or even eliminating flammability
altogether [22]. This is the basis in developing nitrogen inerting systems for commercial
and military aircraft fuel tanks [8].
Intuition would lead to the belief that at the lower flammability limit the fuel is at
the flashpoint temperature, since the flashpoint is the lowest fuel temperature that will
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