Experimental and numerical investigation of laminar burning velocities of artificial biogas under various pressure and CO₂ concentration

As a renewable and sustainable fuel made from digestion facility, biogas is composed predominantly of methane (CH₄) and carbon dioxide (CO₂). CO₂ in biogas strongly affects its combustion characteristics. In order to develop efficient combustors for biogas, fundamental flame characteristics of biogas require extensive investigation. In understanding the influence of CO₂ concentration and mixture pressure on biogas combustion, the effects of CO₂ concentration on the laminar burning velocity of methane/air mixtures were studied at different pressures. The studies were conducted using both numerical and experimental methods. The experiment was conducted using a constant volume high pressure combustion chamber. The propagating flames were recorded with a high speed digital camera by employing Schlieren photography technique. The numerical simulation was carried by utilizing CHEMKIN-PRO with GRI-Mech 3.0 employed as the chemical kinetics model. The results show that the laminar burning velocity of methane-air mixtures decreased with an increase in CO₂ concentration and mixture pressure. Therefore, the burning velocity of biogas mixtures may decrease as the amount of CO₂ in the gas increases.