Effect analysis on the macrostructure and static stability limits of oxy-methane flames in a premixed swirl combustor

In this study, the changes in macrostructure and static stability limits of CH4/O2/CO2 flames were recorded experimentally in a premixed swirl combustor over ranges of equivalence ratio (φ) and oxygen fraction (OF: volumetric percentage of O2 in the O2CO2 oxidizer mixture) and under fixed Reynolds (Re) operation to isolate its dynamic effect on flame stabilization. Two-dimensional stability maps are presented as function of φ and OF. The maps are presented on contours of inlet velocity (Uin), combustor power density (PD) and adiabatic flame temperature (Tad) to correlate these parameters with the stability limits. Selected flames were imaged to analyze the effects of φ, OF, Uin, Tad and Re on flame stability. The results showed that sustaining premixed oxy-flames is not possible for OF below 29% and above 70%. Reactions kinetic rate is a more relevant parameter than Re for determining flashback limit. PD has a leading role for controlling flame stability near the lean blow out limit. Uin is more relevant than Re for controlling flame transition from the inner shear layer to the outer recirculation zone. Increasing Re widens the operability window by shifting blow out limit to leaner conditions.