Abstract: The lower flammability limits of syngas/air mixtures with CO₂ and N₂ inert dilution were experimentally studied under atmospheric conditions via a self-developed closed cylindrical stainless steel vessel. The experimental data were used to validate the performance of the Le Chatelier’s Rule. The experimental results showed that， the lower flammability limit of fuels mixtures decreases with the increase of H₂ fraction. A small amount of H₂ in the fuels presents the significant effect on the lower flammability limit of mixtures due to the variation of the controlled mechanism of the reaction. The lower flammability limits of mixtures almost linearly increases with an increase in inert dilution ratio. CO₂ has a stronger inert effect than N₂ due to CO₂’s stronger thermal and chemical kinetic effect in reducing the flame temperature and radical concentrations. The prediction by Le Chatelier’s Rule has great discrepancy against the experimental results when H₂ fraction is small or with the high presence of inert species in the mixture. Moreover， the different inter effect between CO₂ and N₂ on the lower flammability limit cannot be calculated using Le Chatelier’s Rule.

Key words: syngas, lower flammability limit, hydrogen fraction, CO₂/N₂ inert dilution, Le Chatelier’s Rule