Experimental investigations on laminar burning velocity variation of CH4 + air mixtures at elevated temperatures with CO2 and N2 dilution

Experimental investigations have been performed to examine the role of CO2 and N2 dilution on the laminar burning velocity variation of CH4 + air premixed mixtures at high mixture temperatures using the externally heated diverging channel method. The experiments on diluted CH4 + air mixtures are carried out for various mixture equivalence ratios (ϕ = 0.8–1.2) at higher mixture temperatures (300–650 K) and atmospheric pressure. The numerical predictions using three extensively used chemical kinetic models (GRI Mech 3.0, FFCM-1 and Aramco 2.0) are used to delineate the effect of CO2 and N2 dilution on laminar burning velocity variation. The volume fraction of both the diluents, i.e., CO2 and N2, is varied from 0 to 30% by volume distinctively in CH4 fuel. The burning velocity is observed to decrease sharply with CO2 dilution as compared to N2 dilution case. Detailed sensitivity analysis is carried out to understand the role of various key reactions on the variation of laminar burning velocity of the mixture with dilution. FFCM-1 kinetic model shows a good agreement of the measured values of laminar burning velocity as compared to the kinetic models of Aramco 2.0 and GRI Mech 3.0 mechanisms at various mixture temperature and dilution conditions.