Response of Premixed Stoichiometric Oxy Flames to Strain: Role of Chemistry and Transport

This study investigates stoichiometric premixed CH4/O2/CO2 flames. Our recent studies show that these oxy flames behave differently under turbulent versus laminar conditions, with the extinction strain rate being the key parameter for comparing flame stability. This work builds on that conclusion by investigating why there are differences in extinction strain rates and flame consumption speeds, and the effect of reactant inlet temperature on air and oxy flames. The Lewis number for oxy flames is less than one, whereas the methane-air flame is close to unity. This impacts the response of these two flames to strain. The dominant mechanism is the chemical effect of CO2 present in oxy combustion, which has a bigger impact on the consumption speed and flame extinction strain rate than the effect of transport properties change and Lewis number differences. Specifically, the extinction strain rate was found to be heavily impacted by the reaction CO2+H⇄CO+OH.