Effects of elliptical nozzles on the flame stability and combustion characteristics in a cross-flow

A sub-scaled flaring system was set up to investigate the effects of elliptical nozzles on flame stability, characteristics, and trajectory of flares in a cross-flow for a range of operating conditions. The thesis presents the experimental results of natural gas flames issuing from circular and different aspect ratios (major axis/minor axis) elliptical nozzles with discharge areas of 16.4 mm2, 30.4 mm2, and 93.7 mm2. It was found that flames issuing from elliptical nozzles with the major axis perpendicular to the cross-flow have wider stability limits compared with flames issuing from circular nozzles or elliptical nozzles with the minor axis normal to the cross-flow. This is due to the larger recirculation zone on the leeside of the flare stack, counter-rotating vortices, and axis-switching. It was also found that flames from elliptical nozzles were slightly shorter but more yellowish than flames from circular nozzles. This may be an indication of more soot formation and incomplete combustion, which needs to be verified with emission measurements.