| As a clean energy,hydrogen energy plays a crucial role in solving the fossil energy crisis and mitigating climate change.However,due to the fast diffusion rate,wide explosion limit,low ignition energy and many other factors,hydrogen is easily ignited and exploded.Due to the high-temperature hot surfaces and frictional sparks generated during the use of industrial production equipment such as conveyors,grinders,and polishing machines,hydrogen can be ignited to cause explosion accidents.However,the energy characterization of metal friction sparks and hot surfaces is still unclear,and the ignition mechanism of metal friction on flammable substances is still unclear.Therefore,in this paper,the research on the law of friction sparks and the change of the characteristic parameters of the friction hot surface,the research on the ignition mechanism of metal friction on hydrogen,and the ignition mechanism of metal friction on hydrogen in an inert gas atmosphere are revealed.The main conclusions are as follows:(1)The effects of friction speed,friction pressure,metal type and inert gas on metal friction spark and friction hot surface temperature were studied.With the increase of friction speed and friction pressure,the distribution range of metal friction sparks increases,and the temperature of friction hot surface gradually increases.The lower the thermal conductivity of the metallic material,the higher the maximum temperature reached by the frictional hot surface.Under the frictional pressure of 44.48 N and the frictional velocity of 10.47 m/s,the highest temperatures reached by the frictional hot surfaces of cast iron,304 stainless steel and316 stainless steel are 826 ± 8.3 ℃,948 ± 9.5 ℃ and 999 ± 10.0 ℃,respectively.The maximum spark temperatures are 1132 ± 11.3 ℃,1365 ± 13.7 ℃ and 1401 ± 14.0 ℃,respectively.The inhibition effect of carbon dioxide on metal friction is more obvious than that of nitrogen.When the concentration of carbon dioxide is increased by 40%,the maximum temperature of the friction hot surface of cast iron,304 stainless steel and 316 stainless steel is reduced by 48.1%,47.7% and 49.5%,respectively.The highest friction spark The temperature decreased by 32.6%,31.6% and 30.6%,respectively.Scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS)analysis of metal friction products showed that the oxygen atomic percentage of friction products decreased with the increase of inert gas content.(2)The ignition mechanism of metal friction on hydrogen was studied.Metal friction on hydrogen has two ignition modes: friction particle ignition and friction hot surface ignition.Metal materials with high thermal conductivity(cast iron)have a lower ignition temperature for hydrogen under the same ignition probability.Under the friction conditions of ignition probability of 0.5,friction pressure of 44.48 N and friction velocity of 10.47 m/s,the ignition temperatures of the friction particles of cast iron,304 stainless steel and 316 stainless steel are570 ℃,587 ℃ and 590 ℃,respectively.In an inert gas atmosphere,the ignition probability of hydrogen by metal friction decreases.When the ignition probability is 0.5,increase the nitrogen content by 40%,and the critical hot surface temperature of cast iron to ignite hydrogen needs to reach 645 ℃;increase the carbon dioxide content by 40% to ignite hydrogen The critical hot surface temperature needs to reach 693 °C.The metal friction strength increases,and the lower the thermal conductivity of the metal material,the lower the lower limit of hydrogen explosion that can be ignited.316 stainless steel has the lowest hydrogen explosion limit that can be ignited,and cast iron has the highest.The lower explosion limits of hydrogen that can be ignited by cast iron,304 stainless steel and 316 stainless steel are 5.9%,5.8%,and 5.8%(44.48 N,10.47 m/s).When the friction pressure increased from 11.12 N to 44.48 N,the lower explosion limit of hydrogen in the ignition of cast iron dropped from 7.7% to 5.9%. |
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