Further insights into the core mechanism of H₂/CO/NO_x reaction system

The core H₂/CO/NO_x mechanism is important in understanding the mechanism of NO_x formation during combustion as it forms the base model in developing kinetic models of larger hydrocarbons/NO_x systems. Recently, the Goldsmith group at Brown University performed high-level ab-initio calculations of the chemistry of HONO and HNO₂ and proposed that the thermal rate constant of isomerization of HONO to HNO₂ is orders of magnitude lower than that used in all previous models. This discrepancy may lead to a deviation in understanding the formation mechanism of NO_x. With this in mind, coupling with the latest rate constants obtained by experimental measurements and high-level quantum chemistry calculations, the H₂/CO/NO_x model was circularly updated and re-verified against multi-type datasets over a wide range of initial conditions and experimental devices. The proposed model (XJTUNO-2021) can accurately reproduce almost all of the fundamental combustion data including 156 shock tube datasets, 87 JSR datasets, 114 flow reactor datasets and six laminar flame speed datasets in the literature from 1959 to 2021. Moreover, this study clarifies the shortcomings of the Zhang mechanism of CO/NO_x systems. Finally, the updated model has been used to simulate the formation of NO at practical gas-turbine conditions to give more kinetically information of NO control technologies.