飞机燃油箱惰化中氧体积分数控制指标分析

Analysis on oxygen volume fraction control index in aircraft fuel tank inerting

对油箱惰化的氧体积分数控制指标,即极限氧体积分数,测定标准、理论与实验研究成果进行了较为系统地梳理与总结,并基于前人研究成果提出:(1)采用N2惰化时,对于RP-3燃油,其地面状态下,可采用12%作为油箱氧体积分数控制指标。(2)对于民机,飞行包线内燃油箱氧体积分数控制指标可为从海平面到3 048 m高度,油箱内气相空间极限氧体积分数不超过12%,3 048~12 192 m高度,不超过从12%线性增加到14.5%;对于军机,可以考虑在民机标准上增加20%安全裕度,即从地面的9%线性增加至12 192 m的12%。(3)目前国内军机惰化系统研制中,规定在整个飞行包线内控制燃油箱气相空间氧体积分数不超过9%的要求值得商榷,它将直接带来因过度防护而产生的代偿损失过大等问题。

The current standard test methods for limiting oxygen volume fraction, theoretical and test research results on limiting oxygen volume fraction for aircraft fuel were systematically summarized, then some suggestions were presented by extensively drawing on previous research results:(1) When N2 inerting was adopted on the ground, 12% oxygen volume fraction can be used as the control index of oxygen volume fraction in the fuel tank for RP-3 fuel.(2) For civil aircraft, the control index of oxygen volume fraction in the fuel tank within the flight envelope can be determined, indicating that the limited oxygen volume fraction in the ullage of fuel tank at sea level through 3 048 m was approximately within 12%, with a linear increase from 12% at 3 048 m to approximately 14.5% at 12 192 m;for military aircraft, it can be considered to add a 20% safety margin on the civilian aircraft standard, the limited oxygen volume fraction increased linearly from 9% at sea level to 12% at 12 192 m.(3) At present, in the development of the inerting system of domestic military aircraft, the requirement of controlling the oxygen volume fraction in the ullage of fuel tank within 9% during the whole flight envelope was debatable, which would directly lead to excessive compensation loss caused by excessive protection.