某中央翼燃油箱全程惰化流场的数值模拟研究

Numerical simulation of inert gas distribution in the whole flying process in the central wing tank

在特定的飞行包线下,对某中央翼燃油箱全程惰化过程进行了数值模拟,得到在不同的惰化气体流量和惰化气体进气方式下燃油箱内氧体积分数的空间分布和平均氧体积分数随时间的变化规律。结果表明,降落阶段燃油箱内平均氧体积分数的最大回升值随着惰化气体流量的增加而减小;且相同流量下,适当的调整惰化气体的分配方式,可以有效降低降落阶段燃油箱内氧体积分数的最大回升值,使燃油箱内氧体积分数的空间分布更均匀,从而提高燃油箱的防火抑爆能力。

This paper wants to present a numerical simulation model we have developed to simulate the nitrogen-enriched air （NEA） flow in the whole flying process of a commercial transport aircraft center wing tank （CWT）. The simulation results not only prove the validity of the variation ratio curve of the average oxygen concentration of each bay vs time, but also the truthfulness of the space distribution of oxygen concentration within the CWT by contours. A comparative analysis of the numerical results shows that the mass flowing rate of the nitrogen-abound air determines the inert ratio of each bay, and the entire descending stage of the flight tends to envelop the highest average oxygen concentration of the fuel tank decrease with the in- crease of mass flux rate. This conclusion of ours is consistent with the actual flight reality. And, therefore, it can be said that for all the different distribution methods of the NEA, the space distribution of oxygen concentration in the fuel tank ought to have a significant dif- ference. And, the results of our simulation also show that the distri- bution methods of the NEA have a great effect on the average oxygen concentration during the descending stage. And better distribution methods would make the space distribution of oxygen concentration more uniform and balanced within the CWT though they may reduce the inerting ratio of each bay. The reason is that some NEA may not have mixed enough with the vapors of the CWT. However, under the same mass flux rate, the more uniform the space distribution of oxy- gen concentration is within the CWT, the greater safety the aircraft fuel tank would bring about during the descending stage. Thus, it can be said that our simulated research results can provide a theoretical basis for the study of how the design of transportation airplanes may affect the incrting system of the machine.