Experimental and numerical study of CO2 content effects on the laminar burning velocity of biogas

In the present work, the adiabatic laminar burning velocity of methane diluted with carbon dioxide, the two main components of biogas, is investigated both experimentally and numerically. The burning velocity of five mixtures with different CO2 content (up to 50% in fuel volume) were measured using the heat flux method at atmospheric conditions (298 K and 1 atm). The experimental results were compared to data and correlations form literature and also to predictions from four detailed kinetic mechanisms. Results showed that CO2 dilution reduces the burning velocity and shifts the maximum burning velocity towards leaner mixtures. The Gri-Mech 3.0 mechanism showed the best agreement with measurements for 10% and 20% CO2 fuel content mixtures. For 30%, 40% and 50% CO2 fuel content mixtures, the Konnov mechanism presented the highest determination coefficients. The numerical model is further explored to show that the shifting of the maximum burning velocity towards leaner mixtures is determined by a combination of CO2 dilution and reaction effects.