Local and Monte Carlo uncertainty analyses of NO production during methane combustion were carried out, investigating the effect of uncertainties of kinetic parameters and enthalpies of formation. In Case I, the original Leeds methane oxidation mechanism with the NOx reaction block was used, but the enthalpies of formation of all species were updated. In Case II, the NCN-containing reactions of the prompt NO formation route were added and the rate parameters of several reactions were also updated. The NO production was examined at the conditions of the Bartok et al. experiments (PSR, T = 1565-1989 K, φ = 0.8-1.2, residence time 3 ms). The Monte Carlo analysis provided the approximate probability density function and the variance of the calculated NO concentration, and also its attainable minimum and maximum values. Both mechanisms provided similarly good to acceptable agreement with the experimental results for lean and stoichiometric mixtures, whereas only mechanism Case II could reproduce the experimental data for rich mixtures after a realistic tuning of the parameters. Local uncertainty analysis was used to assess the contribution of the uncertainty of each parameter to the uncertainty of the calculated NO concentration. Enthalpies of formation of NNH and HCCO, and rate parameters of 20 reaction steps cause most of the uncertainty of the calculated NO concentrations at all conditions. The relative importance of the four main NO formation routes was investigated via the inspection of the reaction rates, embedded in the Monte Carlo analysis. NO formation in rich mixtures was dominated by the prompt route, whereas in leaner mixtures the share of the NO formation routes depended very much on the values of rate parameters, when varied within the uncertainty limits of kinetic data evaluations.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry