# Presentation: 347573

**JET A VAPORIZATION****IN AN EXPERIMENTAL TANK****Part 1 computed results****  **

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

## Motivation

**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 for the liquid fuel and tank walls**
**Ambient pressure and temperature**
**Time**

## Previous Work 

**Previous Work**

**Measurement of LFL of Jet A  using different methods: Nestor (1967), Ott (1970)**
**Model of vaporization in a fuel tank using single component fuel: Kosvic (1971)**
**Jet A Explosion Studies: Shepherd, 1997**
**Review of Flammability Hazard: DOT /FAA/AR-98/26**
**Jet A  multi-component, non-equilibrium model: Polymeropoulos and Summer (2002)**
**etc**
**Other work not available in the open literature?**

## Physical Considerations

**Physical Considerations**

**3D natural convection heat and mass transfer ****	**
- Liquid vaporization
- Vapor condensation
**Variable P****a**** and T****a**
**Multicomponent vaporization and condensation**
**Well mixed gas and liquid phases**
- Ralullage~o(109)
- Raliquid~o(106)

- Use of available empirical or experimental data on temporal variation liquid fuel, and tank  wall temperatures
- Possible CFD modeling of the 3D coupled heat and mass transfer processes in the tank
- Advantages:
-  Detailed spacial information on conditions within  the tank
-  Uncertainties with  turbulent modeling of the multi-component  mixing processes
-  Computational complexity with 3D flows
-  Computational time
- Possible use of well mixed tank model with spatially uniform but temporally varying fluid temperatures and compositions
- Advantages:
- Ease of implementation
- Globally correct results provided the fluids are well mixed
- Disadvantages
- Requires empirical correlations for heat and mass transport
- Uncertainties with respect to the degree of well mixedness

- Well mixed gas and liquid phases
- Uniformity of temperatures and species concentrations in the ullage gas 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

## Heat and Mass Transport

**Heat and Mass Transport**

## Liquid Jet A Composition

**Liquid Jet A Composition**

**Liquid Jet A composition depends on origin and weathering**
**Jet A samples with different flash points were characterized by Wodrow (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 120 °F < F.P. < 125 °F**
**Present results  use compositions corresponding to samples with F.P. =120 °F and F.P. = 125 °F from the Woodrow (2003) data    **

## Composition of the Fuels Usedfrom Woodrow (2003)

**Composition of the Fuels Used****from Woodrow (2003)**

## Dry Tank Ullage Temperature Comparison with Experiment (Ochs,2003), Ambient pressure

**Dry Tank Ullage Temperature ****Comparison with Experiment**** ****(Ochs,2003),** **Ambient pressure**

## Dry Tank Ullage Temperature Comparison with Experiment (Ochs,2003), 30,000 ft

**Dry Tank Ullage Temperature ****Comparison with Experiment**** ****(Ochs,2003),** **30,000 ft**

## Computed and Measured (Summer, 1992) Propane Equivalent Hydrocarbon Concentrations

**Computed and Measured ****(Summer, 1992)**** Propane Equivalent Hydrocarbon Concentrations**

**Atmospheric Pressure, **
**2.2 x1.22 x 0.93 m Vented Test Tank with heated floor and unheated walls**
**T****ma****x**** ****fuel**** = 52 °C**

- 2

- 3

## Model Predictions for a Given Flight ScenarioTank Dimensions (m): 0.9 W x 0.9 D x 0.6 HJet A. Flash point = 322.2 K (120 °F)

**Model Predictions for a Given Flight Scenario****Tank Dimensions (m): ****0.9 W x 0.9 D x 0.6 H****Jet A. Flash point = 322.2 K (120 °F)**

## Example of Model Input ParametersTfi= 325 K, Tf-Ts = 10 K

**Example of Model Input Parameters****T****fi****= 325 K, T****f****-T****s**** = 10 K**

## Fuel Vapor Mass Account after LiftoffL=32 Kg/m3,  Tfi  = 325 K,  Tf - Ts = 10 K

**Fuel Vapor Mass Account after Liftoff****L=32 Kg/m****3****,  T****fi  ****= 325 K,  T****f**** - T****s**** = 10 K**

## F/A Variation during FlightL=400 kg/m3, Tfi = 315 K, Tf-Ts=15 K

**F/A Variation during Flight****L=400 kg/m****3****, T****fi**** = 315 K, T****f****-T****s****=15 K**

## F/A, Effect of Fuel Temperature

**F/A, Effect of Fuel Temperature**

## Vapor Molecular Weight

**Vapor Molecular Weight**

## Conclusions

**Conclusions**

- The Jet A fuel to air ratio in a test tank can be estimated using spatially uniform but temporally varying properties in the tank
- Liquid Jet A  can be assumed to consist of a mixture of C5-C20 Alkanes obtained from fuel samples with F.P. in the range of those tested
- The computed results appear to agree with previous atmospheric pressure data from a test tank
- The model was used for estimating the F/A variation during an example flight scenario.  Examples of  computed results  demosntrate:
- The strong effect of liquid temperature on ullage A/F
- The considerable temporal variation of ullage species composition
- The model results must be compared with measurements appropriate to  different flight conditions