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

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support ignition and the lower flammability limit is the leanest mixture that will support ignition. However, the flashpoints are generally higher than dictated by the lower flammability limit temperature due to nonequilibrium conditions in the testing, different modes of ignition, and the inherent nonconservatism in representing real upward flame propagation by a device with downward propagation [13]. It was also found that, in general, the FAR at the flashpoint was at least 15% greater than at the lower limit, although the data had much scatter [13]. For multicomponent fuels, since the vapor composition varies from that of the liquid, relative liquid-vapor mass loading and other factor affect flammability in generally unpredictable ways [13]. The lower flammability limit is the limit of most concern to fuel tank safety researchers. For multicomponent fuels, if the vapor composition is known the lower flammability limit can be estimated using Le Chatelier’s rule. Le Chatelier’s flammability rule [27] is an empirical formula that correlates flammability limits of multi-component hydrocarbon fuels with the flammability limits of the individual components. It accounts for both the concentration and composition of the fuel-air mixture, and can be calculated by: 15 xi LC = ( 1 . 02 − 0. 000721∗T )∑, i = 1 → N ( 2.1 ) LFL where LC is the calculated Le Chatelier ratio, the first term in parenthesis accounts for temperature compensation, xi is the i th species mole fraction in the mixture, LFLi is the lower flammability limit of the i th species and N is the total number of components in the fuel. The mixture is considered flammable if LC is greater than one. I An empirical criterion used for estimating the fuel to air mass ratio (FAR) at the LFL for most saturated hydrocarbons states that at the LFL the FAR on a dry air basis is i
0.035±0.004 at 0°C [26]. The published LFL of JP-8 [37] reflects this approach. Researchers from several institutions involved in the NTSB investigation of the TWA 800 accident [17] used these two methods to calculate fuel flashpoints from experimental fuel analysis data and compared the calculated and measured flashpoints. Both methods yield results that are in reasonable agreement for equilibrium mixtures and can be used for estimating if a given mixture of fuel and air is in the flammable region [17]. It should be noted, however, that there is lack of comprehensive experimental data on the flammability of aviation fuels as a function of temperature and ambient pressure Figure 2.2. Qualitative relation between flammability limits and temperature and altitude (pressure). 16
Page 1 and 2: DOT/FAA/AR-TT09/42 Air Traffic Orga
Page 3 and 4: 1. Report No. DOT/FAA/AR-TT09/42 4.
Page 5 and 6: ABSTRACT OF THE THESIS VAPORIZATION
Page 7 and 8: DEDICATION This thesis is dedicated
Page 9 and 10: 5.0 RESULTS 32 5.1 Validation Tests
Page 11 and 12: 5.7 JP-8 fuel vaporization at sea l
Page 13 and 14: LIST OF TABLES Table Page 2.1 Compa
Page 15 and 16: develop procedures to lessen the li
Page 17 and 18: When it was determined that a CWT e
Page 19 and 20: 1.3 Objectives of the Thesis The ul
Page 21 and 22: has more additives, such as an anti
Page 23 and 24: equilibrium is dynamic in nature, b
Page 25 and 26: factor in making these calculations
Page 27: Volume Fraction, % 30 25 20 15 10 5
Page 31 and 32: Raleigh numbers which were of order
Page 33 and 34: loading of fuel and be subjected to
Page 35 and 36: pressures. The heaters in the pump
Page 37 and 38: Figure 3.1. View of top surface of
Page 39 and 40: the tank and the ullage vapor conce
Page 41 and 42: attempted, but provided inaccurate
Page 43 and 44: pump that could draw samples from a
Page 45 and 46: 5.0 RESULTS When inputting the expe
Page 47 and 48: etween measured and predicted value
Page 49 and 50: 5.1.2 Isooctane Fuel Vaporization T
Page 51 and 52: higher altitudes, as continuous sam
Page 53 and 54: Temperature, Deg. F. 140 120 100 80
Page 55 and 56: Temperature, Deg. F. 70 60 50 40 30
Page 57 and 58: % Propane Equivalent 2 1.5 1 0.5 0
Page 59 and 60: % Propane Equivalent 3 2.5 2 1.5 1
Page 61 and 62: liquid fuel the mass of fuel evapor
Page 63 and 64: In the beginning of the test, the l
Page 65 and 66: 6.2 Flammability Assessment 6.2.1 F
Page 67 and 68: average measured liquid temperature
Page 69 and 70: Fuel to Air Mass Ratio 0.05 0.045 0
Page 71 and 72: 6.2.2 Fuel Tank Under Varying Ambie
Page 73 and 74: Fuel to Air Mass Ratio 0.045 0.04 0
Page 75 and 76: Fuel to Air Mass Ratio 0.05 0.04 0.
Page 77 and 78: temperature measurements would be r
Page 79 and 80:
Which is appropriate for Raleigh nu
Page 81 and 82:
d dt ( mg c pgTg ) = hb Ab ( Tb −
Page 83 and 84:
APPENDIX C: EXPERIMENTAL FUEL FLASH
Page 85 and 86:
13. Fuel Flammability Task Group, A
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Vaporization of JP-8 Jet Fuel in a Simulated Aircraft Fuel Tank ...

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