Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture

The ignition delay times of methane/air mixture diluted by n2 and co2 were experimentally measured in a chemical shock tube. the experiments were performed over the temperature range of 1300-2100 k,pressure range of 0.1-1.0 mpa,equivalence ratio range of 0.5-2.0 and for the dilution coefficients of 0%,20% and 50%. the results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. meanwhile,with ignition temperature and pressure increasing,the measured ignition delay times of methane/air mixture are decreasing. furthermore,an increase in the dilution coefficient of n2 or co2 results in increasing ignition delays and the inhibition effect of co2 on methane/ air mixture ignition is stronger than that of n2. simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. results show that gri_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of n2 and co2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by n2 and co2 show excellent agreement,and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of n2 or co2. © 2014 production and hosting by elsevier b.v.