Study on combustion characteristics of natural gas-hydrogen-air mixtures

The combustion characteristics of natural gas-hydrogen-air mixtures were studied in a constant volume bomb under various ratios of hydrogen to natural gas, equivalence ratios and initial pressures. Meanwhile, a two-zone model was proposed for predicting combustion parameters based on the pressure data. The study shows that, with the increase of hydrogen fraction in mixture, the normalized mass burning rate will increase and the flame development duration and combustion duration will decrease at various equivalence ratios and initial pressures. Little influence of hydrogen addition on the maximum combustion pressure is found at the equivalence ratios near to the stoichiometric equivalence ratio. However, for lean mixture combustion and rich mixture combustion, the maximum combustion pressure will increase with the increase of hydrogen fraction in mixture. Moreover, wide ranges of equivalence ratio for getting shorter combustion duration are presented with the increase of hydrogen fraction in mixture. The decrease in flame development duration shows more obviously at lean mixture combustion and rich mixture combustion.