CO2 addition and pressure effects on laminar and turbulent lean premixed CH4 air flames

An experimental study on CH4-CO2-air flames at various pressures is conducted by using both laminar and turbulent Bunsen flame configurations. The aim of this research is to contribute to the characterization of fuel lean methane/carbon dioxide/air premixed laminar and turbulent flames at different pressures, by studying laminar and turbulent flame propagation velocities, the flame surface density and the instantaneous flame front wrinkling parameters. PREMIX computations and experimental results indicate a decrease of the laminar flame propagation velocities with increasing CO2 dilution rate. Instantaneous flame images are obtained by Mie scattering tomography. The image analysis shows that although the height of the turbulent flame increases with CO2 addition rate, the flame structure is quite similar. This implies that the flame wrinkling parameters and flame surface density are indifferent to the CO2 addition. However, the pressure increase has a drastic effect oil both parameters. This is also confirmed by a fractal analysis of instantaneous images. It is also observed that the combustion intensity S-T/S-L increases both with pressure and the CO2 rate. Finally, the-mean fuel consumption rate decreases with the CO2 addition rate but increases with the pressure.