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Numerical simulation of dilution effect on combustion and flame properties is desirable for various industrial or scientific applications. Predicative capabilities of the simplified (one- and two-step) chemical kinetic mechanisms of methane oxidation in highly diluted flames were evaluated on the basis of mathematical modelling in one-dimensional (axisymmetric) configuration. Profiles of temperatures and concentrations of reactants, combustion products and intermediates in premixed flat flame and nonpremixed counterflow flame burning methane and air/diluent mixture were determined. Detailed chemical kinetic modelling was performed additionally in order estimate the flame temperature and speciation and to quantify the effect of elevated argon and nitrogen concentration and oxygen deficiency on diluted combustion. Global chemical kinetic models were implemented into computational fluid dynamics tool to approve their applicability for numerical simulations of diluted flames in more complex geometries.

Pulsation frequency of the cup-burner flame was determined by means of experimental investigations and numerical simulations. Simplified chemical kinetics was successfully implemented into a laminar fluid flow model applied to the complex burner geometry. Our methodical approach is based on the monitoring of flame emission, fast Fourier transformation and reproduction of measured spectral features by numerical simulations. Qualitative agreement between experimental and predicted oscillatory behaviour was obtained by employing a two-step methane oxidation scheme.