A numerical study on the effect of CO₂ enrichment on the CH₄/O₂ flame

In the present day, CO₂ emission has become a significant problem that needs to be resolved. One of the alternative solutions to decrease the CO2 emission is recycling CO₂ as flue gas in the combustion chamber. Then, the burning process with CO₂ enrichment needs to be understood. Therefore, a numerical study on laminar burning velocity (SL) characteristics of CH₄/O₂ with CO₂ enrichment on oxidizer was conducted using CHEMKIN package GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. As a result of the numerical study can explain the effect of CO₂ enrichment on CH₄ flame clearly. In detail, the results show that the SL of the CH₄/O₂/CO₂ mixture was decreased as CO₂ content increased. Next, CO₂ directly participates in the combustion process and contributes to the value of laminar burning velocity. By comparing the S_L of CH₄/O₂/N₂, CH₄/O₂/CO₂, and CH₄/O₂/F-CO₂, CO₂ dilution on oxidizer mainly contributed by thermal-diffusion rather than chemically. Besides the decrease of S_L due to CO₂ dilution, the intermediate product (O, OH, CO, CH) will decrease as the CO₂ dilution content increases. Finally, these intermediate species contribute positively to S_L.