H2/CO/air premixed and partially premixed flame structure at different pressures based on reaction limit analysis

Abstract

Premixed and partially premixed flames (PPFs) of H2/CO/air syngas are studied numerically to investigate the effect of pressure on syngas PPF structure. Chemical characteristics of the syngas flame at different pressures are investigated based on reaction limit analysis using a one-dimensional configuration. The results show that CO affects the syngas reaction limits through both physical effects that consist mainly in dilution and chemical effects that are related to both R23 (CO + OH = CO2 + H) and HCO pathway. In particular, the HCO pathway weakens the flame at low pressures due to the chain-terminating effect of R25 (HCO + O2 = CO + HO2) and R26 (HCO + H = CO + H2), and enhances the flame at high pressures because of the contribution of R25 to the HO2 chain-branching process. These CO chemical characteristics are also observed in the premixed zone of 50% H2 + 50% CO syngas PPFs whereas only R23 is important in the non-premixed zone.