民用飞机惰化系统富氮气体分配方案分析与研究

Analysis and study of nitrogen-enriched air distribution scheme in inerting system of civil aircraft

提出了飞机惰化系统富氮气体(nitrogen-enriched air,简称NEA)分配系统的主要设计要求,并以A320和波音737飞机为代表,分析了窄体机的NEA分配系统。进一步分析了波音787和A350飞机的惰化系统NEA分配方案,发现其采用限流孔、气体喷嘴、排气笛形管、引射器等相结合的方案来实现NEA在燃油箱内的快速均匀分配,然而这两种方案并不能根据各燃油箱气相空间的实时变化而及时、主动地调节气流量的大小。提出利用燃油液面进行自动流量调节的NEA分配方案,通过在油箱内布置垂直向下的排气管路,并在管路分支上不断增加排气孔来实现排气量随着燃油箱气相空间实时正向变化的目的,达到按照每个隔舱气相空间的变化,调节排气量和排气位置的效果。对比A350和波音787飞机的NEA分配方案的主要特点在于能够主动根据燃油箱内液面变化,及时调节NEA流量,以达到更好的快速、均匀分配的效果,值得进行深入的理论和试验研究。

This paper puts forward the main design requirements for the NEA(nitrogen-enriched air)distribution system of aircraft inerting system and analyzes the NEA distribution system of narrow-body aircraft,taking A320 and Boeing 737 aircraft as examples.The NEA distribution scheme of the inerting system of Boeing 787 and A350 aircraft was further analyzed.It was found that the NEA distribution scheme adopts a combination of flow limiting hole,gas nozzle,exhaust flute pipe,and ejectors to achieve the rapid and uniform NEA distribution in the fuel tank.However,these two schemes cannot adjust the air flow in time and actively according to the real-time changes of the gas phase space of each fuel tank,and the optimal design of NEA distribution cannot be realized.This paper proposes a NEA distribution scheme using fuel fluid level for automatic flow adjustment,which achieves the purpose of real-time positive change of exhaust volume with the gas phase space of the fuel tank by arranging a vertical downward exhaust pipeline in the fuel tank and increasing the exhaust holes through the pipeline branches,so as to achieve the effect of adjusting the exhaust volume and exhaust position according to the size of the gas phase space of each compartment.Compared with the NEA distribution scheme of A350 and Boeing 787 aircraft,this scheme could adjust the NEA flow automatically by the fuel level,which is worthy of further in-depth theoretical and experimental research.