Abstract: In this paper, the influence factors of the lower explosive limit（LEL） of hydrogen—doped natural gas under pipeline leakage condition are analyzed. Based on the chemical reaction formula of lean fuel and the thermodynamic equilibrium in the combustion process, the calculation model of the lower explosive limit of multiple combustible gases for hydrogen—doped natural gas was established by using the adiabatic flame temperature method at the lower explosive limit. The results show that the influence of gas components on the lower explosive limit is great, while the influence of environmental factors on the lower explosive limit of hydrogen—doped natural gas under pipeline leakage condition can be ignored at normal temperature. When the model calculated the lower explosive limit of hydrogen—containing flammable gases with low inert gas content such as N2, the relative error of the model was all within 5%. The calculation accuracy is higher than Le Chaterlier formula and its improved method, which can meet the engineering needs and provide reference for the prevention of leakage and explosion accidents of hydrogen—doped natural gas in pipeline transportation.

Key words: hydrogen—doped natural gas, adiabatic flame temperature method, lower explosive limit, calculation model