Study on Proportions of Flammable Gas in Lightning Test of Aircraft Fuel System
In lightning tests of aircraft fuel system,the ignition energy and ignition probability of flammable gas are great-ly affected by a slight change in the mixture proportions of flammable gas.Using flammable gas with improper mixture proportions may lead to under-assessment or over-assessment of the lightning test,which will influence the accurate eval-uation of the effectiveness of lightning protection design.A high-precision and dynamical gas ratio control system is used to establish the flammable gas ignition test verification system,and the minimum ignition energy and related influence factors of ignition under different proportions of flammable gas are studied and analyzed by experiments.The results show that,using the flammable gas with a 5.0％hydrogen concentration,can detect all ignition sources with energy of 200μJ and above,and can avoid over-assessment of lightning test,so it is recommended to prioritize the selection.With the increase of hydrogen proportion,the ignition energy required for ignition of flammable gas decreases gradually.The higher the hydrogen proportion concentration is,the more the lightning test of fuel system is over-assessed.In consider-ation of the safety impact of flammable gas explosion shock,it is not recommended to use flammable gas with a hydrogen proportion of 6.5％or above in fuel system lightning test.The experimental data and analysis conclusions can provide ref-erence and guidance for lightning protection design and lightning test implementation of aircraft fuel system.
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