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

higher altitudes, as continuous sampling with the high flow sample pump would cause
false readings by the FID due to air entering the ullage through the vents, and continuous
sampling with the FID’s built-in pump would not draw enough sample for the FID to
give accurate readings. Therefore, the comparison was performed at sea level, where the
continuous sampling with the FID’s built-in pump was known to be accurate.
The two tests were intended to be identical, but varied slightly due to different
initial conditions. Figure 5.9 compares the liquid fuel temperatures and measured vapor
concentrations for the two tests. Considering the differences between the test conditions
for the two tests, there is good agreement between the two methods of ullage vapor
sampling, indicating that minor difference is noticed between intermittent and continuous
ullage vapor sampling; thus, intermittent sampling can be used in lieu of continuous
sampling when necessary.
Liquid Temperature, Deg. F.
140
120
100
80
60
40
20
0
Thermocouple
Error
FID Error
Liquid Temp
Measured THC
Calculated THC, 115 FP
Calculated THC, 120 FP
0 500 1000 1500 2000 2500 3000
Time, seconds
Figure 5.6. JP-8 fuel vaporization at sea-level, constant ambient pressure and temperature;
comparison of calculated and measured ullage vapor concentration, M.L. =31.5kg/m 3 .
3
2.5
2
1.5
1
0.5
0
% Propane Equivalent
38