Study on the effect of H2O on the formation of CO in the counterflow diffusion flame of H2/CO syngas in O2/H2O

The effects of H2O addition on the CO production by one-dimensional laminar counterflow diffusion flame of H2/CO syngas in O2/H2O = 27.5/72.5 were studied. Davis, Li and the USC II mechanisms are mainly used for the combustion of syngas and a large number of studies have been made on these mechanisms by researchers. However, most of the existing studies were based on the numerical calculation in air condition. Therefore, the existing mechanisms (Davis, Li, USC II) were not suitable for the combustion in high H2O condition. A modified mechanism was used to simulate the counterflow diffusion flame with the OPPDIF code. Four groups of artificial species (FH2O and H2O, TH2O and FH2O, XH2O and FH2O, RH2O and FH2O) were introduced to break up the couplings between the chemical, thermal, transport and radiative effects of H2O. The four effects of H2O on the CO production at the flame front (the max temperature) are numerically studied. The results show that the oxidation of CO is mainly through CO + OH = CO2 + H. The chemical and radiative effects of H2O have a significant impact on the production of CO, which inhibit CO production and decrease CO concentration. The other effects of H2O have little impact on CO formation. In addition, the chemical effect of H2O improves the flame temperature, the thermal and radiative effects reduce the flame temperature, and the transport effect on the temperature is almost negligible. The influence of these four pairs of H2O on temperature is consistent with the effects on the heat release rate.