An Experimental Study of the Effects of Swirl and Air Dilution on NG Non-Premixed Flame Stability

In this work, an experimental investigation of stability limits of natural city gas (NG) in a non-premixed swirling burner has been conducted. Air swirl motion is imparted through 30º, 45º and 60º vane swirlers to produce low and high swirling air streams. Air dilution with nitrogen (N2) was also performed because of the importance of dilution in practical applications. N2 was added to the swirling air to examine the stability limits under diluted air conditions. The purpose of this study is to examine the stability limits including lift and blow-out velocity in low swirl conditions and liftoff height as well as liftoff velocity in high swirl conditions. It was observed that swirl increased the stability limits of NG while it decreased the negative effects of dilution on flame stability.