飞机燃油箱地面预洗涤技术理论研究

Theoretical Research on Ground-Based Prescribing Technology for Aircraft Fuel Tank

摘要:

基于氧氮质量守恒关系,建立了飞机燃油箱爬升过程中气相空间、燃油中平衡氧浓度及地面预洗涤的数学模型,并采用微元段法对其进行了求解。计算结果显示,当采用富氮气体进行地面预洗涤后时达到的平衡浓度越低,则可达到的安全巡航高度越高。由于爬升过程中逸出的氧气很多会排出燃油箱外,因而地面预洗涤时,并不需要将燃油中氧质量浓度降低至安全气相浓度所对应极限质量浓度,且飞机燃油箱中的初始载油率对洗涤后的氧质量浓度有直接要求,当载油率越高,需要将燃油中的氧质量浓度洗涤的越低。计算还显示,在地面洗涤时,油罐中的油量也对换气次数有直接影响。通过选择合适浓度的富氮气体在地面预洗涤燃油箱,可保证飞机在巡航高度下氧浓度在安全范围内,但是会在一定程度上增加设备的初投资费用。文章的研究结果可为燃油地面预洗涤的工程设计奠定初步的理论基础

Abstract:

Based on mass conservation law of oxygen and nitrogen, in this paper, two mathematic models were establishedfor equilibrium oxygen concentration in ullage and fuel along with the altitude during aircraft climbing as well as nitrogen-rich gas performing ground-based prescribing for fuel tank. And solution was worked out via infinitesimal method. Resultof calculation showed the lower the equilibrium concentration was reached after ground-based prescribing using nitrogen-rich gas, the higher the achievable safety cruising altitude could be. Since much of the escaped oxygen would be dis.charged out of fuel tank during climbing, therefore when performing ground-based prescribing, it was not necessary to re.duce oxygen mass concentration of the fuel to limit concentration corresponding with safety ullage concentration. Besides,initial fuel load rate in the aircraft fuel tank had direct requirement for the scribed oxygen concentration that the higher thefuel load rate was, the lower the oxygen concentration of fuel was needed to be scribed. Calculation also showed that duringground-based scribing, quantity of fuel in the tank also had direct impact on ventilation rate. By choosing nitrogen-richgas with proper concentration to perform ground-based prescribing for fuel tank, it could be guaranteed that the oxygenconcentration would be within safety scope at aircraft cruising altitude, however, initial investment fee for equipment wouldalso increase to some extent. Research findings of this paper could lay a preliminary theoretic basis for the engineering de.sign of fuel ground-based prescribing.