Uncertainty analysis of updated hydrogen and carbon monoxide oxidation mechanisms

Abstract

Uncertainty analysis was used to investigate H 2/air and wet CO/air combustion mechanisms. The hydrogen/carbon monoxide submechanism of the Leeds Methane Oxidation Mechanism was updated on the basis of the latest reaction kinetic and thermodynamic data. The updated mechanism was tested against three hydrogen oxidation and two wet CO bulk experiments. Uncertainties of the simulation results, caused by the uncertainties of the kinetic parameters and the heat of formation data, were analysed. The methods used were the local uncertainty analysis and Monte Carlo analysis with Latin hypercube sampling. The simulated flame velocity had a relatively large uncertainty in both hydrogen–air and wet CO flames. In the case of ignition experiments, for both fuels the uncertainties of the simulated ignition delay times were small and comparable with the scatter of the experimental data. There was a good agreement between the simulation results and the measured temperature and concentration profiles of hydrogen oxidation in a flow reactor. However, accurate ignition delay is not a result of the flow reactor experiments. The uncertainty of the required time correction for matching the simulated 50% consumption of H 2 to that of the experimental one (corresponding to the simulated ignition delay) was found to be very large. This means that very different parameter sets provide very different ignition delays, but very similar concentration curves after the time correction. Local uncertainty analysis of the wet CO flame revealed that uncertainties of the rate parameters of reactions O 2 + H (+M) = HO 2 (+M), and CO + OH = CO 2 + H cause high uncertainty to the calculated flame velocity, temperature, and peak concentrations of radicals. Reaction H + HO 2 = H 2 + O 2 also causes high uncertainty for the calculated flame velocity. The uncertainty of the enthalpy of formation of OH is highly responsible for the uncertainty of the calculated peak OH concentration.