Flame modes and combustion characteristics of a triple port burner

Increasing concerns of issues on global warming and climate change have urged stringent expectation on new energy conversion devices for much higher thermal efficiency and carbon dioxide capture and sequestration. Considering the practicability and safety, multi-port burners are widely used in industry to achieve the purpose of safety and emission control. Therefore, in this study co-annular triple port burner was used to investigate the flame phenomenon. The flame phenomenon was observed by varying the velocity of oxidizer stream (mixture of N2 and O2) and oxygen concentration ratio in central tube. Flame images showed that the increase in the velocity of oxidizer stream can effectively inhibit the soot formation before the presence of the inverse diffusion flame (IDF). In addition, the hysteresis of flame was also observed by means of adjusting flow velocities in the central tube. The flame modes were classified into six types, namely normal diffusion flame, partially-premixed flame, closed-tip inverse diffusion flame, opened-tip inverse diffusion flame, lifted-off edge flame and plume flame, respectively. Especially, the positions of rich-premixed branch for inner and outer triple flames were reverse because of the layout of the oxidizer stream and fuel stream. The rich-premixed branches for inner flame and outer flame were merged in the downstream and meanwhile trapped soot in flame. It explains the flame with opened-tip and bright flame. The gas analyzer was carried out the measurement of burned gas. As the result of Ω=33%, 40% and 60%, it can be conjectured that the flame temperature increases significantly due to the well combustion reaction when the flame is form of lifted-off flame or IDF, resulting in an increase of the thermal NOx.