Control Technology Of Oxygen Concentration On Civil Aircraft Fuel Tank Ullage

Due to the demand of of the relative FAA airworthiness certification regulations, anddevelopment of membrane separation technology, onboard inerting technology which studies how tocontrol oxygen concentration of ullage in civil aircraft fuel tank currently has been widely appliedabroad to achieve the purpose of fire explosion suppression. In order to meet the requirements of theresearch tasks on the basis of inspecting and sorting relevant information, the methods of tank fireexplosion suppression and the status of onboard inerting technology were systematically summarizedin the present paper and the inerting process using numerical integration in the civil aircraft fuel tankwere studied, and theoretical washing models were established. Then Matlab was adopted to simulatethe process and some influence factors on washing inerting process including the effect of flow,oxygen dissolved from fuel and flow rate of inerting gas were analyzed in detail. Consequently, basedon these results above, an optimized inerting program was coded for the fuel tank of C919. As well,an experimental scheme for washing inerting means of civil aircraft multi-bay tank was designed.The studies result:(1) the manual regulations of flow directions require accurate judgments ofreal flow, so the method of pressure self-balancing to obtain the flow directions is much moreappropriate. The calculations of the ground-based inerting process reveal that two different methodscould obtain the same results, so it means the method of pressure self-balancing is acceptable.(2)When the dissolved oxygen in the fuel is considered, VTE increases accordingly with the rate of fuelload increasing, on the contrary, VTE will keep the same;(3) via the simulation contrasts of full timeinerting, it can be seen that the inerting effect of different bays are various, and sometimes volumeconcentration of oxygen in some bays may rise. Inerting efficiency, recovery level and rateconsidering the oxygen escaped from fuel are slightly lower than what not considering, volumeconcentration of oxygen in the vapor space within a certain period of time may be less than thevolume concentration of oxygen of NEA.(4) For multi-bay tank of C919, from simulation resultsusing Matlab, it can be seen that when inerting gas inject into bays numbered1,2,3,6,9whose flowrates are16.67%、16.67%、16.67%、25%、25%percentage of overall flow rate respectively, theinerting results are best.The study results obtained in this paper can be used as reference for inerting system designs andfuel tank inerting program options of multi-bay fuel tank.