# Presentation: 223376

**MULTI-COMPONENT FUEL VAPORIZATION IN A SIMULATED AIRCRAFT FUEL TANK**

**C. E. Polymeropoulos**
**Department of Mechanical and Aerospace Engineering, **
**Rutgers University**
**98 Bowser Rd**
**Piscataway, New Jersey, 08854-8058, USA**

**MOTIVATION**

- Generation of a flammable mixture within aircraft center fuel tank may result in explosion hazard
- Experimentation with Jet A  vaporization in an instrumented  laboratory tank has been used to assess the effect of different test conditions on the resulting fuel vapor concentrations (Summer, 1999)
- Evaluation of the experimental results (Summer, 1999) requires analytical consideration of:
-  the influence of  different experimental  parameters
-  the multi-component fuel vaporization

**OUTLINE**

- Brief discussion  of the experiment and of the results (Summer, 1999)
- Description of the semi-empirical model
- Results and comparison with data
- Conclusions

## SCHEMATIC DIAGRAM OF APPARATUS SUMMER (1999) 

**SCHEMATIC DIAGRAM OF APPARATUS ****SUMMER (1999)**

**EXPERIMENTAL CONDITIONS/DATA**

- Mass loading (mass of liquid/tank volume):                   		0.08 - 5.46 kg fuel/m**3**
- Fuel pan area : 0.09 m**2** - 2.05 m**2**
- Mean liquid temperature: 52 °C
- Unheated tank walls

## Temporal Variation of Gas, Liquid and Mean Wall Temperatures, and of Propane Equivalent Hydrocarbon Concentration

**PREVIOUS EXPERIMENTAL FINDINGS**(Summer, 1999)

- Propane equivalent hydrocarbon concentration   reached a maximum steady value which increased with mass loading
- The time for reaching maximum hydrocarbon concentration decreased with increasing mass loading
- Measured hydrocarbon concentrations were lower than those expected with equilibrium vaporization at the liquid temperature (Woodrow, 1977, Shepherd, 1977)

**PHYSICAL CONSIDERATIONS**

- 3D natural convection heat and mass transfer within the tank.
- Liquid vaporization
- Vapor condensation
- Multicomponent vaporization and condensation

**PREVIOUS WORK**

- Numerous previous investigations of  heat transfer within enclosures
- Review papers: Catton (1978), Hoogendoon (1986),   Ostrach (1988), etc.
- Correlations
- Few studies of heat and mass transfer within enclosures:
- Single component fuel evaporation in a fuel tank,           Kosvic et al. (1971)
- Computation of single component liquid evaporation within cylindrical enclosures, Bunama, Karim et al. (1997, 1999)

- Well mixed gas and liquid phases
- Uniformity of temperatures and species concentrations the gas and evaporating fuel
-              Ra**g** ≈10**9****	**** ****,   **Ra**l** ≈ 10**5**-10**6**
- Use of experimental liquid, gas, and wall temperatures
- Mass transport using heat transfer correlations and the analogy between heat and mass transfer for estimating film mass transfer coefficients
- Low evaporating species concentrations

## PRINCIPAL MASS CONSERVATION AND PHYSICAL PROPERTY RELATIONS

**PRINCIPAL MASS CONSERVATION AND PHYSICAL PROPERTY RELATIONS**

## Mass Transfer Correlations

## Assumed Jet A Composition Based on data by Clewell, 1983, and adjusted to reflect for the presence of lower than C8 components

**Assumed Jet A Composition**** ****Based on data by Clewell, 1983, and adjusted to reflect for the presence of lower than C8 components**

## Assumed Jet A Composition by no. of Carbon Atoms

##  Computed and Measured Equilibrium Vapor MW

-  Computed and Measured Equilibrium Vapor MW

## Computed and Measured Equilibrium F/A

## Computed and Measured Equilibrium Vapor Pressure

## Effect of Fuel Loading on Measured and ComputedPropane Equivalent Fuel Vapor Concentrations

- Effect of Fuel Loading on Measured and ComputedPropane Equivalent Fuel Vapor Concentrations

## Evolution of Fuel Vapor in the Tank

**Evolution of Fuel Vapor in the Tank**

## Effect of Fuel Loading on ComputedFuel Vapor to Air Mass Ratio

- Effect of Fuel Loading on ComputedFuel Vapor to Air Mass Ratio

## Effect of Fuel Loading on ComputedFuel to Vapor Molecular Weight

- Effect of Fuel Loading on ComputedFuel to Vapor Molecular Weight

## Effect of Fuel Loading on the Steady State Vapor Mole Fraction  

- Effect of Fuel Loading on the Steady State Vapor Mole Fraction

## Results for the Floor Area Covered with Fuel  

**Results for the Floor Area Covered with Fuel **

## Results with a 30.5 x 30.5 cm Pan

**Results with a 30.5 x 30.5 cm Pan**

## CONCLUSIONS

**CONCLUSIONS**

- A semi-empirical model of Jet A vaporization together with previous experimental temperature data were used to compute the evolution of multi-component fuel vapor within the test tank ullage
- The liquid species composition was based on previous data adjusted to yield reasonable agreement with measured equilibrium vapor compositions at different fuel loadings
- There was good agreement between computed and experimental total vapor concentrations
- Computed results showed that  steady state vapor concentration in the test tank was reached when the rate of vaporization equaled the rate of condensation   on the tank walls

## CONCLUSIONS (continued)

**CONCLUSIONS (continued)**

- Condensation on the tank walls had a strong influence on the ullage vapor concentration
- Depletion of light components  as the fuel loading was decreased resulted in increase of the molecular weight of the resulting mixture
- For the cases considered computed vapor to air mass ratios  ratios were in good agreement with those calculated from experimental propane equivalent PPM data using a constant fuel vapor MW of 132.4 and a carbon ratio of 3/9.58
- The approach will be further tested to include current data with with  a different size tank, sub- atmospheric pressures, and a spark igniter
- Extension using data with a full size tank when available

## ACKNOWLEDGMENT

**ACKNOWLEDGMENT**

- The work was supported by the Fire Safety Division of the FAA William J. Hughes Technical Center, Atlantic City, New Jersey, USA.
- Helpful discussions with Richard Hill  and Steven Summer of the Fire Safety Division are gratefully acknowledged