Comparative Analysis of Inerting Effects of Open and Closed Vent Systems Fuel Tanks

The ability to suppress fuel tank ignition and explosion is related to passenger safety and aircraft survivability. To enhance aircraft fuel tank safety, the on-board fuel tank inerting technology is applied to reduce the probability of fuel tank ignition and explosion, whether the fuel tank has open or closed vent system. This paper takes the single-bay fuel tank of a certain type of aircraft as the research object, establishes mathematical models of the inerting process of open and closed vent systems fuel tanks, and writes programs to carry it out based on MATLAB R2019b combined with the numerical calculation method of microelement integration according to the actual on-board hollow fiber membrane separation performance. On this basis, this paper analyzes the variation of oxygen concentration in the ullage of open and closed vent systems fuel tanks, compares their advantages and disadvantages, and explores the influence of factors on the inerting effect, such as initial oxygen concentration, fuel loading, aeration pressure, and valve diameter. The results show that for the same nitrogen-enriched air (NEA) flow rate and concentration, the inerting effect of the closed vent system fuel tank is better than the open vent system fuel tank, which can better meet the airworthiness regulations requirements on the flammability exposure time. The initial fuel loading and oxygen concentration have a more significant effect on the initial stage of inerting. Within the range of the vent valve diameters considered in this study, any appreciable difference in the oxygen concentration behavior could not be identified. When the tank pressure conditions permit, it is recommended to use a larger valve threshold to better utilize the good inerting effect of the closed vent system fuel tank.