Fire Extinguishing Performance Optimization Research Of HFC-125 Composite Inhibitor

Fire is one of the most important threats to the safe flight of aircraft,and high performance fire extinguishing agents are an important guarantee to prevent and control the development of aircraft fires and reduce casualties.Halon 1301 fire extinguishing agent is a mature fire extinguishing agent used in aircraft,but it will be banned in 2040 because it causes ozone layer depletion and greenhouse effect.Therefore,it is urgent to develop a new environmentally friendly and high-efficiency halon replacement agent.Pentafluoroethane(HFC-125)has zero ozone depletion potential and similar mobility to halon 1301 and has been declared by the FAA as the most promising halon replacement agent,but its fire extinguishing efficiency is lower than Halon 1301.In this paper,we expect to enhance the fire extinguishing efficiency of HFC-125 through a composite approach while ensuring environmental friendliness to meet the urgent need for a new halon replacement gas fire extinguishing agent.The main research works are as follows:(1)Fire extinguishing performance and synergy study of HFC-125 compound fire extinguishing agent.C3H2F3Br(2-BTP)contains efficient chemical inhibition groups Br and CF3,and 2-BTP was selected to be compounded with HFC-125.A gas-liquid fire extinguishing experimental platform was built to test the minimum fire extinguishing concentration,which was used to obtain the minimum fire extinguishing concentration of different compound volume ratios of HFC-125 composite fire extinguishing agent to suppress methane-air coaxial laminar flow flame.The experiments show that the minimum fire extinguishing concentration for suppressing 280 mL/min methane fire is 6.9%at λ=16.7/83.3,which is 39%lower than that at X=0/100.The extinguishing mechanism of composite extinguishing agent on methaneair coaxial laminar flow flame was analyzed,and the effect of different methane flow rates on the minimum extinguishing concentration was explored.Finally,the synergistic index calculation verifies the synergistic extinguishing effect of the composite extinguishing agent,and proves that the HFC-125 composite extinguishing agent has the best synergistic extinguishing effect when λ=16.7/83.3.(2)Research on the suppression mechanism of composite extinguishing agent on methane-air laminar flow flame.The chemical kinetic mechanism of the composite extinguishing agent was constructed and its accuracy was verified;the flame structure,main reactive radical consumption/generation reaction,main heat absorption/exothermic reaction and heat release rate before and after the composite were compared;the suppression mechanism of the composite extinguishing agent on laminar premixed flame was revealed.The physical and chemical contributions of the composite extinguishing agent to the flame speed of methane laminar flow under poor combustion conditions were quantified,and the results showed that the chemical contribution of 2%volume fraction of composite extinguishing agent compared with pure HFC-125 extinguishing agent was reduced from 5.33 cm/s to 1.88 cm/s atλ=16.7/83.3.The similarities and differences between the extinguishing mechanism of composite extinguishing agent and HFC-125 extinguishing agent were compared.The similarities and differences of the fire suppression mechanism between the composite and HFC-125 agents were compared,indicating that the consumption of H radicals and the brominated recombination cycle are the key to the synergistic effect.(3)Fire extinguishing suitability study based on FAA minimum standard test.PSR(Perfectly Stirred Reactor)was used to investigate the changes of temperature,overall reaction rate,heat release rate and heat release amount of the composite fire extinguishing agent in a closed aerosol tank.The effects of different oxidant contents and different compounding ratios on the active radicals and the temperature inside the chamber were investigated to determine the overall reaction rate and heat release amount of the composite fire extinguishing agent inside the chamber with different oxidant contents and different compounding ratios.At λ=25/75,the overall heat release was reduced by 42.4%.It was shown that the overall reaction rate and overall heat release were better at λ≤50/50,where the compound fire extinguishing agent reduced the concentration of reactive radical OH in the chamber.