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

liquid fuel the mass of fuel evaporated increased rapidly and was accompanied by an
equivalent (except for the negligible mass vented) increase in the mass of fuel stored in
the ullage. In addition, during part of this initial vaporization period the composition of
ullage species was insufficient to satisfy dew point conditions on the tank walls, and as
shown in figure 6.2, there was no condensation predicted until approximately 1800
seconds when such conditions were satisfied. As can be seen in figure 6.1, the liquid
temperature was a maximum at approximately 1700 seconds. The gradual buildup of
vapor species in the tank reduced the mass fraction difference between the liquid surface
and the ullage gas, and hence the rate of vaporization. Together with the onset of mass
removal by condensation, this resulted in a gradual reduction of the rate of increase of
ullage vapor stored. Cooling of the liquid fuel further decreased the rate of vaporization
and, as shown in figure 6.1, the mass stored eventually reached a maximum value at
approximately 2200 seconds signifying a balance between the rates of vaporization and
condensation. The mass stored then decreased continuously because of further cooling of
the liquid fuel. As can be seen in figure 6.2 the mass of vapor vented out did not
significantly affect the magnitude of the ullage mass.
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