Study of effects of burner configuration and jet dynamics on characteristics of inversed diffusion flames

The effect of the geometric parameters and jet dynamics of the port array inverse diffusion flame (IDF) burner on the flame characteristics were investigated experimentally usingliquefied petroleum gas (LPG) fuel. The geometric parameters are the central air flow area, the fuel jets flow area, the number of the fuel jets and the radius of the pitch circle around which the fuel ports are arranged. The jet dynamics are the air and the fuel flow rates and their momentum flux. Three burners were used for this purpose. The analysis of the results of the IDF jet dynamics showed that two flame fronts formed in the entrainment zone of the IDF, one of them in the co-flowing jet formed by the fuel and the central air jet and the other is in the peripheral submerged jet formed by the fuel jets and the ambient air. Beyond the neck, the central air jet, the fuel jets and the two flame fronts flow as one flame torch. At high air, Reynolds number and low fuel Reynolds number, corresponding to the primary equivalence ratios near unity, the IDF produced by the burner of pitch circle radius 10 mm are short blue color sootless flames. As the air Reynolds number was gradually decreased to a low value corresponding to a primary equivalence ratio 4.5, the flame was changed to yellow diffusion flame with high soot concentrations. The results also showed that the flame characteristics were highly affected by the number of the fuel ports. The flame became more bluish and shorter as the number of the fuel ports increases to 36 ports.   Key words:  Inverse diffusion flame (IDF), diffusion flame, burner configuration.