Explosions of Syngas/CO2 Mixtures in Oxygen-Enriched Air

Most of the scientific works on syngas combustion deal with dry air as oxidizer, whereas very few studies have been carried out on syngas combustion in oxygen-enriched air (i.e., oxy-combustion). In this work, the explosion behavior (peak pressure and burning velocity) for H2/CO/O2/N2/CO2 mixtures has been evaluated experimentally and numerically, for different H2/CO ratios, fuel (H2+CO) concentrations with respect to O2, molar percentages of CO2, and for values of the oxygen-enrichment factor, E (= O2/O2+N2), ranging from 0.21 (i.e., air) to 1 (i.e., pure oxygen). The Sandia PREMIX module of the CHEMKIN package, coupled to the detailed Davis reaction scheme, was used to calculate the unstretched laminar burning velocity. Results have shown a good agreement with the experimental data. Through ad hoc simulations, the role of CO2 has been also evaluated. Furthermore, the ranges of validity of the additivity rule for the burning velocity have been identified. All tests show the typical trend of pressure time history of explosions occurring in a closed combustion chamber. However, some compositions show anomalous impulses that could not be explained by classical theory for deflagration/detonation. Explanation for this behavior is based on results of previous works by the same authors on combustion-induced Rapid Phase Transition (c-RPT).