Jet Fuel Vaporization and Condensation: Modeling and Validation - PowerPoint PPT Presentation

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Jet Fuel Vaporization and Condensation: Modeling and Validation

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Jet Fuel Vaporization and Condensation: Modeling and Validation Robert Ochs and C.E. Polymeropoulos Rutgers, The State University of New Jersey International Aircraft – PowerPoint PPT presentation

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Title: Jet Fuel Vaporization and Condensation: Modeling and Validation


1
Jet Fuel Vaporization and Condensation Modeling
and Validation
  • Robert Ochs and C.E. Polymeropoulos
  • Rutgers, The State
  • University of New
  • Jersey
  • International Aircraft
  • Systems Fire Protection
  • Working Group Meeting
  • Grenoble, France
  • June 21, 2004

2
Part I Physical Considerations and Modeling
3
Motivation
  • Combustible mixtures can be generated in the
    ullage of aircraft fuel tanks
  • Need for estimating temporal dependence of F/A
    on
  • Fuel Loading
  • Temperature of the liquid fuel and tank walls
  • Ambient pressure and temperature

4
Physical Considerations
  • 3D natural convection heat and mass transfer
  • Liquid vaporization
  • Vapor condensation
  • Variable Pa and Ta
  • Multicomponent vaporization and condensation
  • Well mixed liquid and gas phases
  • Rayleigh number of liquid o(106)
  • Rayleigh number of ullage o(109)

5
Principal Assumptions
  • Well mixed gas and liquid phases
  • Uniformity of temperatures and species
    concentrations in the ullage and in the
    evaporating liquid fuel pool
  • Use of available experimental liquid fuel and
    tank wall temperatures
  • Quasi-steady transport using heat transfer
    correlations and the analogy between heat and
    mass transfer for estimating film coefficients
    for heat and mass transfer
  • Liquid Jet A composition from published data from
    samples with similar flash points as those tested

6
Heat and Mass Transport
  • Liquid Surfaces (species evaporation/condensation)
  • Fuel species mass balance
  • Henrys law (liquid/vapor equilibrium)
  • Wagners equation (species vapor pressures)
  • Ullage Control Volume (variable pressure and
    temperature)
  • Fuel species mass balance
  • Overall mass balance (outflow/inflow)
  • Overall energy balance
  • Natural convection enclosure heat transfer
    correlations
  • Heat and mass transfer analogy for the mass
    transfer coefficients

7
Liquid Jet A Composition
  • Liquid Jet A composition depends on origin and
    weathering
  • Jet A samples with different flash points were
    characterized by Woodrow (2003)
  • Results in terms of C5-C20 Alkanes
  • Computed vapor pressures in agreement with
    measured data
  • JP8 used with FAA testing in the range of 115-125
    Deg. F.
  • Present results use compositions corresponding to
    samples with F.P.120 Deg. F. and 125 Deg. F.
    from the Woodrow (2003) data

8
Composition of the Fuels Usedfrom Woodrow (2003)
9
Dry Tank Tests
  • Tests run without fuel in the tank to check the
    accuracy of the heat transfer correlations
    without the added variable of mass transfer
  • Ullage temperature was measured in three
    different locations to verify the well-mixed
    assumption
  • The measured ullage temperature was compared with
    the calculated ullage temperature

10
Dry Tank Ullage TemperatureComparison of
measured vs. calculated ullage temperatureShows
validity of well-mixed ullage assumption
Measured ullage temp
Calculated ullage temp
11
Part II Experimental Validation of Modeling
12
Overview
  • Fuel vaporization experimentation is performed at
    W.J.H. Technical Center at Atlantic City Airport,
    NJ
  • Experimental data consists of hydrocarbon
    concentrations and temperatures as functions of
    time
  • Data is input into computer model and compared to
    calculated vapor composition

13
Model Inputs
  • Fuel and tank surface temperature profiles
  • Pressure and outside air temperatures as
    functions time
  • Fuel composition (volume fractions of C5-C20
    Alkanes) from Woodrow (2003)
  • Tank dimensions and fuel loading

14
Model Outputs
  • Hydrocarbon concentration profile
  • Propane equivalent hydrocarbon concentrations
  • Parts per million or percent propane can be
    converted into F/A ratio
  • Ullage temperature profile

15
Experimental Setup
  • Fuel tank 36x36x24, ΒΌ thick aluminum
  • Sample ports
  • Heated hydrocarbon sample line
  • Pressurization of the sample for sub-atmospheric
    pressure experiments
  • Intermittent (10 minute intervals) 30 sec long
    sampling
  • FID hydrocarbon analyzer, cal. w/2 propane,
    check w/4
  • 12 thermocouples
  • Blanket heater for uniform floor heating
  • Unheated walls and ceiling
  • JP-8 Fuel

16
Experimental Setup (continued)
  • Fuel tank inside environmental chamber
  • Programmable variation of chamber pressure and
    temperature using
  • Vacuum pump system
  • Air heating and refrigeration system

17
Experimental Setup (continued)
18
Thermocouple Locations
19
Experimental Procedure
  • Fill tank with specified quantity of fuel
  • Adjust chamber pressure and temperature to
    desired values, let equilibrate for 1-2 hours
  • Begin to record data with DAS
  • Take initial hydrocarbon reading to get initial
    quasi-equilibrium fuel vapor concentration
  • Set tank pressure and temperature as well as the
    temperature variation
  • Experiment concludes when hydrocarbon
    concentration levels off and quasi-equilibrium is
    attained

20
Experimental Results
21
Experimental Results
22
Experimental Results
23
Flight Profile Tests
24
Simulated Flight
25
Pure Component Fuel
  • Use isooctane (C8H18) as test fuel
  • Pure component removes the ambiguity of
    multi-component fuel composition
  • Highly volatile at room temperature need to
    cool fuel to approx 0 deg. F. to stay within
    range of hydrocarbon analyzer

26
Isooctane
27
Conclusions and Future Work
  • Measure flammability with NDIR type hydrocarbon
    analyzer and compare results with FID type
    analyzer
  • Use experimental data from flight tests to
    compare measured with calculated flammability
  • Simulate flight test scenarios in the lab to
    compare flammability of flight tests, lab tests,
    and calculated results
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