Combustion optimization of a port-array inverse diffusion flame jet

This paper is an experimental study on the combustion optimization of an Innovative Inverse Diffusion Flame (IDF) characterized by a central air jet surrounded by an array of fuel jets for impingement heating. An extensive investigation has been performed to explore the effects of the diameter ratio between air port and fuel port (dair/dfuel) on the IDF structure, particularly on its thermal and emission characteristics. Small, moderate and large dair/dfuel are investigated. It is found that under the same air flow rate (Q˙air) and dfuel, dair exerts a significant influence on the behavior of the IDF by changing air/fuel hydrodynamics including air/fuel mixing intensity and air entrainment intensity. The experimental results show that smaller dair produces a blue flame with better thermal characteristics, with higher maximum flame temperature (Tf,max), wider range of air jet Reynolds number (Reair) for flame stability, and wider operation range of the overall equivalence ratio, Φ. On the emission side, smaller dair is found to produce more incomplete combustion products of CO and HC but less NOx, which is attributed to lower volume of high-temperature zone and shorter flame residence time. The current investigation provides a valuable input for combustion and design optimization of this innovative IDF burner for impingement heating.

► This is an experimental investigation on combustion and design optimization of an innovative port-array inverse diffusion flame (IDF) burner.
► Effects of the air port/fuel port diameter ratio on flame and combustion characteristics are studied.
► Burner with smaller air port diameter produces more stable blue IDF, less NOx, more CO and HC.
► A similarity in centerline flame temperature profiles is observed independent of the air/fuel port diameter ratio.
► Under the same air flow rate, emissions of incomplete combustion products, e.g., HC and CO, decrease with increasing equivalence ratio.