Effect of Reynolds Number on Combustion Stability and Flame Macrostructure in a Dual Annular Combustor

This study was conducted to investigate the impact of Reynolds number on combustion stability and flame macrostructure in a dual annulus stratified swirl burner. Stratified burners are known for their lower NOx and increased flame stability, but their stability also depends on combustor geometry, stratification ratio, equivalence ratio, and flow dynamics. The study revealed that flame static stability decreases with increasing Reynolds number. The flame blowout equivalence ratio increases by 11.6% as Reynolds number increases from 1000 to 3500 which was due to low vortical temperature with less residence time in the recirculation zone. Flame macrostructure also revealed that at lower Reynolds numbers, the flame stabilizes at inner and central shear layers, while at higher Reynolds numbers, it stabilizes at only central shear layer. Thermoacoustic instability is not observed at lower Reynolds numbers up to 2000, but thermoacoustic instability is observed at higher Reynolds numbers of 2500 and above. An interesting phenomenon of beating oscillation was observed at 2500 Reynolds number at stoichiometric conditions.