Experimental analysis of blockage effect on low-swirl burner combustion parameters for lean premixed natural gas-air flames

In this paper, the effect of axial flow blockage percentage on combustion parameters of low-swirl burner is investigated. The burner uses premixed natural gas and air mixture. Equivalence ratio varies from 0.55 to 0.59 (lean mixture). Flows are compared in 51.1%, 57.8% and 67.2% of blocked area of axial flow, power of 21.7 kilo Watts and equivalence ratio of 0.57. Geometrical aspects of flame are compared using Canny edge detection algorithm. Combustion zone temperature profile is analyzed using thermocouples in different vertical distances from the burner edge. OH* radical chemiluminescence is compared qualitatively using flame spectroscopy. Concentration of important emissions like CO, NO and NO2 are also reported using exhaust gas analysis. As the result of increasing in axial velocity, by decreasing the blockage, flame blow off happens in a wide range of equivalence ratio. Also by increase in swirl number from 0.41 to 0.49, Combustion zone width (radial direction) increases from 112mm to 123mm which causes a significant decrease of its average temperature and relevant emissions like thermal Nitrogen Oxides (maximum 12ppm). Also as a result of divergence of velocity vectors, flame distance from burner edge decreases from 11.86mm to 5.21mm.

Keywords:

Low-Swirl Burner , Swirl Number , Chemiluminescence , Image Processing , Exhaust Gas Analysis , Flame Edge Detection