Effects of dilution on premixed methane/air combustion are investigated through experiments and numerical simulations on laminar burning velocities. Experiments are carried out at atmospheric pressure and 393 K; computed results are obtained using the GRI mechanism and the Premix code of the Chemkin package. Laminar burning velocities are determined for several diluents (nitrogen, carbon dioxide, vapor water, a mixture of the three previous gases representative of exhaust gases, helium, and argon) and for different dilution percentages. The equivalence ratio is kept constant equal to stoichiometric. Excellent agreements between experimental data and computed results are obtained. Because heat capacity seems to possess the predominant effect on the laminar flame, an explicit correlation between the heat capacity of the diluent and the laminar burning velocity is proposed.

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