scholarly journals Analytical Algorithm for Oxygen Concentration of Aircraft Fuel Tank in Various Inerting Stages

2021 ◽  
Vol 11 (16) ◽  
pp. 7698
Author(s):  
Yuhao Wei ◽  
Yang Pei ◽  
Yuxue Ge
Keyword(s):  
Differential Equations ◽  
Oxygen Concentration ◽  
Fuel Tank ◽  
Conventional Model ◽  
Aircraft Fuel ◽  
Proposed Model ◽  
Fuel Tanks ◽  
Analytical Algorithm ◽  
Fire And Explosion ◽  
Derivatives Of

Ullage washing is an efficient inerting method to keep the ullage oxygen concentration under the safe value, thus reducing the hazard and loss of fire and explosion of aircraft fuel tanks. In the conventional model of ullage washing, the initial derivatives of oxygen concentration that are used to solve the differential equations are selected subjectively by researchers and the empirical select influences the accuracy of the result. Therefore, this paper proposes an analytical algorithm that can calculate the ullage oxygen concentration without selecting any initial derivative value. The algorithm is based on a fuel tank ullage washing model regarding various inerting stages. It has been experimentally validated with an average relative error of 5.781%. Moreover, sensitive analyses carried out on the proposed model show that ground-based inerting can effectively reduce the ullage oxygen, concentration in the climb phase. Increasing 5 min of pre-takeoff inerting duration can shorten the time of decreasing the ullage oxygen concentration to 9% after takeoff by 2.1 min.

Numerical Study of the Influence of Ambient Pressure on the Inerting Effect of an Aircraft Fuel Tank Inerting System

2014 ◽  
Vol 1061-1062 ◽  
pp. 1140-1143
Author(s):  
Dong Jie Liu
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Ideal Gas ◽  
Fuel Tank ◽  
Dissolved Oxygen Concentration ◽  
State Equations ◽  
Aircraft Fuel ◽  
Inerting System

The numerical study of the influence of the ambient pressure of the fuel tank on the inerting effect of an aircraft fuel tank inerting system was carried out. The mathematical model of ullage equilibrium oxygen concentration has been established using the differential time calculation method based on the mass conservation and ideal gas state equations. The variations of ullage oxygen concentration and dissolved oxygen concentration in the fuel with time under different working conditions have been obtained. The results have shown that the as the ambient pressure of the fuel tank became lower, the speed of the decreasing of oxygen concentration of the fuel tank ullge and the dissolved oxygen concentration of the fuel was slower.

Elementary Computer Modeling Applied to TWA800 Fuel Tank Forensic Issues

1998 ◽  
Author(s):  
Floyd A. Wyczalek
Keyword(s):  
Jet Fuel ◽  
Combustible Mixture ◽  
Scientific Data ◽  
Fuel Tank ◽  
Critical Conditions ◽  
Jet Fuels ◽  
Potential Hazard ◽  
Minimum Ignition Energy ◽  
Aircraft Fuel ◽  
Fuel Tanks

Abstract The specific mission was to identify the conditions of atmospheric pressure and ambient temperature under which a so-called empty-Boeing model 747-131 fixed wing jet aircraft center wing tank (CWT), containing a residual fuel loading of about 3 kg/m3, less than 100 gallons of aviation kerosene (JetA Athens refinery commercial jet fuel), could form hazardous air/fuel mixtures. The issues are limited to explosion safety concerns relating to certificated fixed wing jet aircraft in regularly scheduled commercial passenger service. It is certain that a combustible mixture does not exist in a fuel tank containing Jet-A type fuel at ambient temperatures below 38°C (100°F), which is the lean limit flash point (LFP) for commercial jet fuel at sea level. Never the less, although not included in this paper, the original study reported by Wyczalek and Suh (1997), identified six highly unlikely, but rationally possible critical conditions which can occur in a combination which may permit a combustible mixture to exist within a jet aircraft fuel tank and pose a potential hazard. The scope of this paper is limited to mathematical modeling concerns related to fixed wing jet aircraft fuel tanks and commercial jet fuels combustible air-fuel mixture ratios. It was further limited to a historical review of the scientific literature in the public domain from 1950 to the present time, which defined the thermodynamic and minimum ignition energy properties of aviation gasoline and commercial jet fuels; and, to comparisons with new thermodynamic data for JetA Athens flight test samples, released by the National Transportation Safety Board (NTSB) during public hearings on the TWA800 event in Baltimore, Maryland in December 1997. The original work reported by Wyczalek and Suh (1997) conclusively demonstrated that the USAF Wright Air Development Center and the US Bureau of Mines conducted and published comprehensive evaluations of the potential hazards relating to jet aircraft fuel tanks as early as 1952. This historical scientific data and the mathematical models for the new jetA and Athens refinery jetA in this paper, are relevant to pending TWA800 related litigation, and to the future implementation of NTSB recommendations resulting from the TWA800 event.

The Oxygen Concentration Measurement of an Aircraft Fuel Tank Inerting System

2014 ◽  
Vol 568-570 ◽  
pp. 137-140
Author(s):  
Yan Cai ◽  
Gui Ping Lin
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Concentration ◽  
Light Absorption ◽  
Suitable Condition ◽  
Operating Conditions ◽  
Fuel Tank ◽  
Concentration Measurement ◽  
Fuel Vapor ◽  
Aircraft Fuel ◽  
Optical Fluorescence

There are several oxygen concentration measurement methods applied in aircraft fuel tank inerting systems. In this work, an aircraft fuel tank inerting experiment system was built and oxygen concentration of the fuel tank ullage (fuel tank space above the surface of the fuel which is filled with fuel vapor and air) and the dissolved oxygen in the fuel was detected with the methods of light absorption and optical fluorescence. The experiment was conducted through different operating conditions and results has illustrated that the light absorption method as well as the optical fluorescence method has the same accuracy sensing calibration gases, but the suitable condition of the two methods are different. Results have shown that the method of light absorption is more suitable to test oxygen concentration of gas mixture, and the method of optical fluorescence is more suitable to detect the concentration of dissolved oxygen in liquid substance.

Modeling of fuel transport in pressure-fed systems with flow passage opening devices

2021 ◽  
pp. 095441002199499
Author(s):  
Seong Ho Im
Keyword(s):  
Numerical Model ◽  
Fuel Tank ◽  
Cross Sectional ◽  
Flow Passage ◽  
Proposed Model ◽  
Air Vehicle ◽  
Fuel Tanks ◽  
Sectional Plane ◽  
Transport Condition ◽  
High Degree

This study presents a numerical model of a pressure-fed system with flow passage opening devices (FPODs) designed for an air vehicle with a high degree of maneuverability. The FPOD is a mechanical device that connects two separate fuel reservoirs and functions as a valve allowing liquid fuel to flow while minimizing the movement of pressurizing gas from upstream fuel tanks into downstream fuel tanks. A reduced-order model for the fuel motion in an annular fuel tank was developed to configure the depth and inclination angle of the free fuel surface on the cross-sectional plane of an annular fuel tank under accelerating conditions during flight. Furthermore, a newly proposed model that reflects the dynamic characteristics of the FPOD is used to determine the fluid type that is transported through the device. A simulation example shows that the full numerical model captures changes of the fuel transport condition over time in a complete pressure-fed system of annular fuel tanks with FPODs subject to acceleration.

scholarly journals Dimensional modelling of the fuel outgassing phenomenon: Improving flammability assessment of aircraft fuel tanks

2011 ◽  
Vol 115 (1172) ◽  
pp. 605-614 ◽  
Author(s):  
A. P. Harris ◽  
N. M. Ratcliffe
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Transfer Rate ◽  
Fuel Tank ◽  
Aviation Fuel ◽  
Evolution Rate ◽  
Time Constants ◽  
Oxygen Evolution Rate ◽  
Aircraft Fuel ◽  
Wide Range ◽  
Fuel Tanks

Abstract Fuel outgassing (oxygen evolution) within aircraft fuel tanks presents a serious flammability hazard. Time constants representing oxygen transfer rate, from the fuel into a tank’s ullage, are used to model the effect of outgassing on tank flammability. These time constants are specific to a single aircraft type and flight envelope and may not accurately represent fuel outgassing behaviour for other aircraft types with differing fuel tank configurations and flight envelopes. To improve current modelling practice for more accurate flammability analysis dimensional modelling has been used to determine the rate of oxygen evolution from Jet A-1 fuel in an aircraft fuel tank. Measurements of oxygen evolution rate, made on a dimensionally similar model, have been projected to an A320 aircraft. The evolution of oxygen from the fuel was found to increase monotonically with time. Fitting the test data with an inverse-exponential function enabled oxygen release rate and its associated time constant (τ) to be determined. Dimensional modelling of aviation fuel outgassing using model fuel tanks will enable oxygen evolution rate from aviation fuel to be determined for a wide range of aircraft fuel tank configurations and environments without the need for flight testing. In turn the accuracy of flammability assessment of aircraft fuel tanks will be improved and significant cost savings made.

scholarly journals Experimental Aircraft Fuel Tank Vapour/Air Explosions Using Jet A and Jet A / Gasoline Blend Fuels

2021 ◽  
Vol 2 (2) ◽  
pp. 55-71
Author(s):  
M. N. Abdulmajid ◽  
N. P. Herodotos ◽  
E. A. Gordon
Keyword(s):  
Initial Pressure ◽  
Severity Index ◽  
Fuel Tank ◽  
Ignition Point ◽  
Aircraft Fuel ◽  
Fuel Tanks ◽  
Vapour Cloud ◽  
Lower Flammability Limit ◽  
Typical Design ◽  
Cylindrical Test

The potential of a fuel tank explosion is a well-known hazard in the aircraft industry. In this study, an investigation of a lab scale aircraft fuel tank in a flight situation at varying initial pressures of 400 - 1,000 mbar (equivalent to altitudes of 0 - 22,300 ft) and at variable temperatures was conducted in a 100-litre cylindrical test rig. A standard Jet A fuel and with a type Jet B fuel (which in this case was a Jet A with 10% of gasoline by mass) were used. Their flashpoints were measured to be 45oC (Jet A) and 20 oC (Jet B). In the simulated fuel tank explosions ignition occurred when the fuel liquid temperature was much higher than the flash point - 71 – 107 oC depending on initial pressure (altitude) for Jet A and 57 – 95 oC for the more volatile Jet B. The resulting maximum explosion overpressures were high, ranging from 0.7 to 5.8 bar, much higher than typical design strengths of aircraft fuel tanks, and much stronger than anticipated overpressures on the basis of ignition at or close to the lower flammability limit (LFL). It is postulated that these pressures are due to the distance between the liquid fuel surface and the ignition point and the formation of a vapour cloud with decreasing concentration with height above the fuel (being at LFL at the ignition point) and hence an overall concentration much higher than LFL. This demonstrated that severe explosions are fuel tanks are likely and the assumption that the explosion will be a near lean limit event is not safe. The work also provided explosion severity index data which can be used in design of suppression and venting systems for the mitigation of aircraft fuel tank explosions and provided other quantitative data to help manage this explosion risk appropriately.

Cleaner Fuel Through Nitrogen Inserting

1971 ◽  
Author(s):  
W. Q. Brookley
Keyword(s):  
Fuel Tank ◽  
System Component ◽  
Fuel System ◽  
Fuel Additives ◽  
Fuels Reduction ◽  
Aircraft Fuel ◽  
Aircraft Performance ◽  
Fire And Explosion

Development of an aircraft fuel tank nitrogen system to suppress fire and explosion has been underway for several years. As work progressed it was learned that such a system could also reduce contamination in the fuels. Reduction of contamination will reduce fuel system component malfunctioning, improve aircraft performance, and possibly eliminate the need for fuel additives and exotic fuels.

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