화염의 상호작용에 의한 부분 예혼합화염의 화염날림 유속 확대

Abstract

For the non-premixed interacting jet flames, it has been reported that of eight small nozzles are arranged along the circle of 40~72 times the diameter of single jet, the flames are not extinguished even in 200m/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, Φ, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying S and Φ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with Φ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of feul through centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was defferent from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.