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Keywords:

  • syngas;
  • shock tube;
  • ignition delay;
  • kinetic analysis

Ignition delays of four typical syngas mixtures were investigated using both experimental and simulated methods. The shock tube experiments were conducted behind the reflected shock waves at temperature ranges from 870 to 1 350 K, pressures of 0.2, 1.0 and 2.0 MPa. Six available kinetic models were evaluated by comparing them to the new ignition delay data obtained. NUIG C3 model was in good agreement with the experimental results. The effect of the pressure on ignition delay of all four syngas mixtures was similar to that of hydrogen. The promoting and inhibiting ignition were experimentally observed at high and moderate temperatures, respectively. Sensitivity analyses were conducted at different temperatures and pressures to identify the dominant elementary reactions in the ignition process of the syngas. The results indicated that the ignition delay was generally most sensitive to the chain branching reaction H + O2 = O + OH at both high and low temperatures. Decomposition reaction H2O (+M) = H + OH (+M) was of importance for the syngas with relative inert gas CO2 and N2 at a high temperature. The reaction CO + OH = CO2 + H involving CO kinetic dominated the ignition at a high temperature for the syngas with a high CO level. The inhibiting effect of pressure was attributed to the decrease of sensitivity of the reactions H + O2 = O + OH and O + H2 = H + OH and the increase of sensitivity of the reaction H + O2 (+M) = HO2 (+M) at a moderate-low temperature.