A Comparison Between Water Addition and CO₂ Addition to a Diffusion Coflow Flame

This work compares the effects of adding water vapor and CO2 as diluent to fuel for a diffusion flame at different ambient pressures. The approach of this research is to study numerically a methane diffusion flame with various amounts of water vapor and CO2 added to the fuel, and to compare the flame behaviors with various percentages of water vapor and CO2 content (0% to 65%). This work uses a coflow burner in the PeleLM numerical framework for simulating the flame and computing the combustion behavior. The flame was simulated with pressures of 1.0, 1.4, 5.7, and 11.1 atm. The results extracted and analyzed include temperature profiles at fixed heights and various species mole fractions compared with their values at an equilibrium state condition. The results show that most of the diluent impact does not involve changes in flame chemistry but primarily changes to heat release and heat capacity in the flames. The results also show that the diluent amount has a much larger impact on flame behavior than do changes in pressure.