Numerical studies of CO formation during biogas combustion

This work deals with the LES (Large Eddy Simulation) of methane (CH4) and biogas non-premixed jet flames with the goal of examining the impact of CO2 addition on the formation of carbon monoxide. To model the chemistry, Equilibrium Chemistry (EC) as the cheapest approach was considered first, followed by a global kinetic model and a reduced reaction mechanism describing the combustion of syngas (CO + H2) combined with the reaction CH4 + 0.5 O2 → CO+ 2 H2. Highly diluted laminar jet flames were studies first to decouple the chemistry from the turbulence. All three models predict a considerable increase in the mass fractions of CO in the presence of CO2 in the fuel. Turbulent jet flames were subsequently considered which could not be simulated using equilibrium chemistry owing to numerical problems. The two chemical kinetic models predict a strong increase in CO.